Standard Practices of Reticular Chemistry
Since 1995 when the first of metal−organic frameworks was crystallized with the strong bond approach, where metal ions are joined by charged organic linkers exemplified by carboxylates, followed by proof of their porosity in 1998 and ultrahigh porosity in 1999, a revolution in the development of their chemistry has ensued. This is being reinforced by the discovery of two- and three-dimensional covalent organic frameworks in 2005 and 2007. Currently, the chemistry of such porous, crystalline frameworks is collectively referred to as reticular chemistry, which is being practiced in over 100 countries. The involvement of researchers from various backgrounds and fields, and the vast scope of this chemistry and its societal applications, necessitate articulating the “Standard Practices of Reticular Chemistry”.
- Cornelius Gropp*Cornelius Gropp*(C.G.) Email: [email protected]Department of Chemistry, University of California-Berkeley, Kavli Energy Nanoscience Institute at UC Berkeley, Berkeley, California 94720, United StatesMore by Cornelius Gropp
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- Stefano Canossa*Stefano Canossa*(S.C.) Email: [email protected]EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, BelgiumMore by Stefano Canossa
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- Stefan Wuttke*Stefan Wuttke*(S.W.) Email: [email protected]BCMaterials, Basque Center for Materials, UPV/EHU Science Park, 48940 Leioa, SpainMore by Stefan Wuttke
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- Felipe Gándara*Felipe Gándara*(F.G.) Email: [email protected]Instituto de Ciencia de Materiales de Madrid (ICMM)—Consejo Superior de Investigaciones Científicas (CSIC), C/Sor Juana Ineś de la Cruz, 3, Madrid 28049, SpainMore by Felipe Gándara
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- Qiaowei Li*Qiaowei Li*(Q.L.) Email: [email protected]Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Fudan University, Shanghai 200433, ChinaMore by Qiaowei Li
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- Laura Gagliardi*Laura Gagliardi*(L.G.) Email: [email protected]Department of Chemistry, Minnesota Supercomputing Institute, and Chemical Theory Center, University of Minnesota, Minneapolis, Minnesota 55455, United StatesMore by Laura Gagliardi
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- Omar M. Yaghi*Omar M. Yaghi*(O.M.Y.) Email: [email protected]Department of Chemistry, University of California-Berkeley, Kavli Energy Nanoscience Institute at UC Berkeley, Berkeley, California 94720, United StatesMore by Omar M. Yaghi
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Synopsis
Reticular chemistry is a growing field of science with a multitude of practitioners with diverse frames of thinking, making the need for standard practices and quality indicators ever more compelling.
Introduction
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Reticular chemistry, the linking of molecular building blocks by strong bonds into crystalline extended structures, is one of the fastest growing fields of science. (1,2) In metal–organic frameworks (MOFs), the strong bonds are metal to charged ligand rather than the weaker metal to neutral ligand-type bonds of coordination networks (or polymers), (3) and in covalent organic frameworks (COFs) the strong bonds are covalent bonds. There are many distinguishing features of reticular chemistry, which stand out from the usual practice of chemists—a practice that has been largely focused on the study of discrete organic compounds, metal complexes, supramolecular compounds, and polymers, with the occasional foray into solid-state materials such as metal oxides. Although coordination networks have been reported since 1959, (4−11) little effort was applied in developing the strong bond approach using charge-assisted coordination and covalent bonds to produce crystalline, infinite two- and three-dimensional metal–organic and organic structures. (12) One of us (O.M.Y.) recalls that as a student in the mid-1980s, chemists deemed the building of crystalline extended structures by strong bonds an unlikely objective because it was expected to yield amorphous solids (due to the crystallization problem). (13) The lack of attention to this subject is indicated by its near absence from common inorganic and organic textbooks. (14,15) The discovery and development of permanently porous crystalline frameworks, such as MOFs (16−25) and COFs, (26−30) two areas of reticular chemistry, are changing this state of affairs in a foundational way.
In this context and in the spirit of this article, we wish to point out that it is inaccurate to refer, as sometimes found in the literature, to MOFs and COFs as supramolecular frameworks (or solids). We make a distinction here that supramolecular chemistry is the chemistry of controlling noncovalent interactions, and its outcome is molecules held together by such weak bonds to make larger assemblages. (31) These entities often find their inspiration from biology. In contrast, MOFs and COFs are held together by strong bonds between metal ions and charged linkers, and covalent bonds between light elements (e.g., B, C, N, O), respectively. The shift from the weak to the strong bond energy landscape comes with new challenges (such as achieving reversibility) that chemists have to overcome in order to make reticular structures in crystalline form. Thereby, chemical structures with distinguished physical and chemical properties become accessible, as manifested by their architectural and chemical stabilities. As such, reticular frameworks can withstand a wide range of chemical reactions without loss of their porous backbone. This has opened up many opportunities for chemists to practice precision reactions on infinite two- and three-dimensional (2D and 3D) extended chemical structures. (32)
The reticular synthesis of MOFs and COFs uses molecular building blocks and covalent linking reactions emanating from inorganic and organic chemistry. The study of their porosity and molecular confinement properties requires the practitioner to be well-versed in physical chemistry. Recently, the success of incorporating these materials into devices and their field testing required chemistry researchers to extend their skills to engineering. (33−37) It is becoming increasingly evident that the reticular chemist par excellence is one who is not just grounded in chemistry, but also has the ability to develop skills in other fields as the task at hand may require. Indeed, taking one’s basic research all the way to applications should include demonstrating its use in society or at least making credible attempts to take it “outside” the laboratory. This approach is fruitful when the basic science is done rigorously, and the applications are pursued under conditions relevant to those required for their deployment in industry and society. We are not advocating that societal needs necessarily have to dictate the basic research; rather, we wish to emphasize the importance of independent fundamental research and, at the same time, encourage scientists to pursue emerging opportunities to apply their findings toward technologies that address societal problems. This is the spirit with which reticular chemistry was founded and is being developed, and among the reasons for the current excitement and expansion of the field over the last 25 years.
With the increasing number of reticular researchers worldwide of varying backgrounds and interests comes the need for systematizing knowledge and providing guidelines for what constitutes acceptable standards of reporting scientific findings. Every mature field has such standards, although often not formally agreed upon, but they are part of the commonly accepted practice. The introduction of such guidelines for reticular chemistry is needed in light of its rapid development that involves making and predicting new compounds. This would set the tone for incoming researchers and enhance the quality of the science for those who already practice it routinely, not to mention others who might occasionally venture into it in the hope of finding answers to questions raised in their own research.
One of the principal difficulties in reticular chemistry deals with the fact that the results of synthesis are solids having strongly bonded extended structures. As such, they are insoluble in aqueous and nonaqueous media, and therefore the usual protocols and techniques practiced in molecular chemistry rarely provide definitive answers. Evaluation of yield and achieving molecular-level characterization of such reticular solids are much more arduous than for their molecular, soluble counterparts. Despite the constantly evolving crystallographic methods, most importantly X-ray and electron diffraction, a single technique to fully characterize extended structures in their numerous relevant properties is still absent; thus, many different characterization methods are needed for one to achieve the same level of precision commonly realized for discrete molecules. Accordingly, the question of providing guidelines for quality becomes more relevant as is the adherence to the basic chemistry principles on what constitutes a pure compound. As we strive to bring higher precision to the characterization of reticular solids, one must not neglect the power of making meaningful comparisons between results and developing trends in the course of evaluating quality. As in many thriving endeavors, a multitude of practitioners with diverse frames of thinking have entered reticular chemistry, making the need for recalling essential principles and standards (discussed in many other contributions) (38) ever more compelling (Figure 1, see Supporting Information). We note that a major turning point came in 1995 when it was first demonstrated that a charged organic molecule could be linked to a transitions metal-ion and produce a crystalline extended structure, termed a metal–organic framework (Figure 1). (16) This was a departure from the plethora of coordination networks reported up to that point, wherein the linkages are based on metal-neutral ligands. It was the MOFs made from charged linkers (carboxylates) that were later proven to be architecturally robust and to have permanent porosity, (17) making them objects of extensive study until today (Figure 1).
Figure 1
Figure 1. Expansion of reticular chemistry from 1995–2020. The bright yellow dots represent the institutes actively working on MOFs, COFs, and ZIFs. The search was restricted to the terms MOF, COF, and ZIF in original articles and reviews, and the affiliations were counted only for the corresponding authors. In total, as of the day of the search May 4, 2020, researchers in 5102 institutes and 102 countries (country icon) have published a total of 27,524 papers (manuscript icon).
In addition to the points presented above, we wish to outline the goals of this contribution. First, we wish to enumerate the common parameters in the practice of reticular chemistry that define the system under study in its operation, sets of conditions, and results.
Second, we wish to layout guidelines and recommendations for what hopefully would become standards of quality and clarity to be used in reporting scientific data related to these parameters. Our intent is not to give a blueprint for how one achieves such “standards” in the laboratory, but rather to share with the community what we think would strengthen the routine practice of standards. In addition, we offer scientific motivation for closely considering what we call “quality indicators” when reporting research results. We deliberately do not attempt to be prescriptive or comprehensive but instead wish to invoke some deeper thought about this topic and bring awareness to it as we pursue our respective endeavors under the expanding field of reticular chemistry.
Workflow in the Practice of Reticular Chemistry
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At the heart of reticular chemistry and the impetus for its rapid growth is the creation of new structures, where increasingly these are being used to address societal problems. While it has not been and it should not be an objective to have all researchers follow a specific scheme of activities, inevitably patterns in conducting research emerge, and thus a general workflow can be articulated (Figure 2). Such workflow facilitates the research and enhances its replicability and reproducibility. In this regard, we identified three key steps in the practice of reticular chemistry: The synthesis, activation, and analysis of the products (blue, orange, and green cycles in Figure 2). Ideally, the process of venturing from one step to the next should be considered as an iteration for the purpose of refinement (iterative refinement) and ultimate optimization of properties. This iterative process, best aided by computations, implies that each key step is revisited until the compound at hand complies with the quality standards necessary to make the findings valuable to the wider scientific community. Analytical tools and techniques enabling the researcher to examine the outcome of each step are central to the optimization process. It is essential that the assessment of the outcome of each cycle adheres to common quality indicators (bordered by blue, orange, and green squares in Figure 2).
Figure 2
Figure 2. A workflow illustration of the most common scientific activities and related parameters (blue, brown, and green cycles), which reticular researchers follow in their synthesis and characterization of solids. This includes the quality indicators (correspondingly colored squares), which should be carefully considered in reporting of results.
Specifically, every discovery of an extended structure, be it a MOF or a COF, starts with its synthesis (Figure 2, Synthesis). Here, the most commonly considered parameters—and there are arguably many more—are starting compounds, molar ratios, temperature, concentration, reaction additives such as acid or base, modulators (small molecules influencing the reticulation process), solvents, and reaction time. Depending on the experience and persistence of the researcher, one or more of these parameters are varied to obtain the desired crystalline product (noting that in some cases noncrystalline forms, such as glassy materials are targeted). (39−41) The experimental process can be accelerated by high-throughput synthesis (42) or screening by the aid of computational techniques. (43)
A primary quality indicator that allows the researcher to evaluate the outcome of the synthesis is the validation of the atomic structure of the products, as determined by powder or single-crystal X-ray diffraction. The experimental diffraction pattern should match the calculated one, and all reflections that do not match should be assigned to contaminants, unreacted starting compound(s) or byproduct(s), whose structure ideally should be identified. Microscopy techniques are valuable additions, through which the purity of the newly made compound can be evaluated by scrutinizing the shape and elementary composition of the crystals. Particularly for COFs, microscopy techniques are essential to investigating the structural aspects that cannot be probed only by diffraction due to their lower crystallinity relative to MOFs. Finally, chemical group analysis, most importantly done by spectroscopic techniques, should be employed to monitor functional group conversions, compositional heterogeneities, and defects.
Following the initial synthesis, the permanent porosity and architectural stability of the compound at hand are assessed by initially carrying out a process called activation (Figure 2, Activation). Activation describes the practice of removing all guest molecules (including solvent) from the pores of the framework without causing collapse of its structure. This step should be undertaken thoughtfully in that one needs to consider the possible guest-framework interactions and the impact their disruption might make on the overall structure of the framework. Thus, initially the activation of a new framework must be delicately examined to understand the conditions under which permanent porosity and architectural stability can be achieved for that framework. We liken the process of activation to that of separation in molecular chemistry, where a target molecule is isolated from others through separation methods. In the present context of reticular structures, one might consider the activation as a separation of the guests from the framework.
The methods for activation are comprised of conventional heating and vacuum drying, chemical extractions, supercritical CO2 extraction, and solvent exchange. For a detailed discussion on the advantages or disadvantages of each technique, the reader is referred to recent literature reviews. (44−46) An important quality indicator for the success of activation is the measurement of a nitrogen or argon adsorption isotherm (at subatmospheric pressure and below their respective boiling point), followed by analysis of the specific surface area. (1,17) We note that measurements done at room temperature and high pressure are not proof of permanent porosity because under pressure gases are “forced” to permeate through a substance porous and nonporous alike. It is only through measurement of gas adsorption isotherms that pore volume and surface area values are obtained, and any distortions in the framework structure are manifested in the shape of the isotherm. (17,18)
The surface area is routinely obtained from the isotherm and compared to the value calculated from the theoretical model. After activation, it should be verified by atomic structure analysis that no detectable loss in crystallinity occurred. Re-examination of the molecular composition and chemical group analysis will indicate the induced chemical alterations (if any) to the framework.
Next comes the study of the identity and character of the compound (Figure 2, Analysis). This process describes the identification and characterization of the physical and chemical properties of the compounds, thereby allowing the researcher to identify what elevates them from an exercise of scientific curiosity to a meaningful advance in technology. Among those unique identifiers of a compound are phase purity, proving that the compound is free of contaminants. Here, the researcher will have to resort to analytical and computational techniques used to study the atomic structure of the compounds. Finding the chemical composition includes the analysis of the atomic content of the metals and light elements, as well as chemical group analysis. NMR spectroscopy on the digested compound provides valuable information on the composition and stoichiometry by analyzing its molecular organic components.
Crystallinity describes the degree of structural order, which is defined primarily by mosaicity, defects, and disorder, and ultimately encompasses the crystal size and morphology (Figure 2, Analysis). This information is best acquired by combining diffraction and microscopy techniques. Nitrogen or argon isotherms confirm the permanent porosity of the framework and are used to calculate the surface area and pore volume. The pore size and its distribution are experimentally deduced from the isotherm based on its type and profile features. It is important to note that the theoretical models, which are used to calculate the discrete pore size from the isotherms, were originally developed for porous inorganic compounds, such as carbon and zeolites. Therefore, the transferability of these models to MOFs and COFs should be carefully evaluated.
Flexibility, or lack of rigidity, describes the reversible motion or switching of a framework’s backbone while maintaining its permanent porosity. (47−52) It is not to be confused with architectural instability, which is due to the irreversible change of the framework conformation or its loss of structural integrity. (53) For example, indicative of a framework’s flexibility is sometimes the observation of a hysteresis in the nitrogen or argon isotherm, and this behavior can be further examined by in situ/operando spectroscopic and X-ray scattering techniques, and computational simulations. The stability of a framework is indicated by its ability to withstand chemical and/or thermal strain. It is a requirement that the atomic structure and architectural integrity of the compound be preserved after such strain assessment. Architectural stability is undeniably one of the most important features of the framework as it leads to permanent porosity, which is the accessible surface area, and this lays the foundation for most applications.
The main quality indicators at this third stage (Figure 2, Analysis) are relative to the applications of the compounds. These are expressed in terms of performance, longevity, versatility, and specificity. Performance is the efficacy of a compound to execute the designated task. In catalysis for instance, this can be identified by the turnover frequency, while in gas sorption it can be either the capacity or the kinetics of the uptake and release. Longevity is a measure of the long-term performance of the compound and more specifically consists of its ability to maintain the observed performance over time. Versatility is the capability of a compound to carry out more than one function, while the specificity describes how selective the compound is toward one or a group of chemicals.
We recognize that through the application of this iterative refinement researchers can convince themselves that the results are reproducible, but we recommend in addition that such reproducibility be independently confirmed by others in the laboratory. In general, researchers should endeavor to report detailed description of their synthesis procedures to the level that a newcomer to the field with little experience can reproduce it. We provide below what we believe are “best practices” for the correct execution of the analysis and a thorough description of the results.
Characterization Techniques for Reticular Compounds
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The complete characterization of reticular compounds, such as MOFs and COFs, is only achieved through the combination of multiple techniques. Here, we provide a description of the most relevant characterization techniques in support of steps articulated above for the practice of reticular chemistry. For every type of analysis, we clarify which kind of information can be reliably obtained, and the cases where the data should not be overinterpreted but need to be complemented with the results from other techniques. Our purpose here is to provide guidelines to avoid common pitfalls during the characterization process, and to report results and necessary information in a useful and sensible manner. Before discussing the details of single techniques, a few general requirements for the experimental methods description are listed below. These must be supplemented with other essential information, which is specific to each characterization method and will be specified in each dedicated paragraph.
The instrument’s model is an important piece of information as it defines the kind, precision, and accuracy of the resulting analytical information. These details must also comprise the most important components, such as, for spectroscopic and scattering techniques, source type and detector model. A description of the sample holder is also necessary, when its features are not unique and obvious from the instrumentation. The software (and version) used for the data processing, often provided with the instrument, must always be clarified, as well as additional software used for further data treatment, as for instance structure solution and refinement programs for crystal structure determination.
The description of the sample preparation must include all the treatments performed after the synthesis until the start of the data collection. Finally, the conditions that the sample is subjected to during the data acquisition must be described. These include temperature, pressure, and chemical environment such as gas mixture or solvent. This last piece of information can be excluded when it is obvious, for instance, in the case of measurements normally conducted in high vacuum as in scanning and transmission electron microscopies (SEM and TEM).
Single-Crystal X-ray Diffraction (SCXRD)
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SCXRD provides evidence for the structural features of any crystalline compound at the atomic level. It allows the determination of the framework atomic positions, and the corresponding bond lengths and angles, with subangstrom precision. Widely used and developed for decades, SCXRD is the preferred technique for the determination of any new crystal structure. Moreover, SCXRD also allows the study of guest–framework interactions resulting from sorption processes, (54,55) structural changes after postsynthetic modifications, (56) or structural determination of molecules included or generated inside the framework pores, (57,58) provided these processes occur while maintaining the single-crystal nature of the reticular compounds.
Results of the SCXRD experiments provide a picture of the average structure of the crystals. Because of their porous nature, MOF crystals are usually comprised of well-ordered atoms belonging to the framework, and other atoms with a higher degree of disorder, usually belonging to guest molecules located in the pores. Furthermore, even for framework atoms, differences are also commonly found for the different building units, namely, inorganic secondary building units (SBU) and organic linkers. Terminal ligands or chemical functionalities pointing into the pores might also exhibit positional disorder. In these situations, the resulting atomic anisotropic displacement parameters (ADPs) will show these differences, which should be carefully inspected during the refinement. Whenever possible, a disorder model should be attempted to explain otherwise unusually large ADPs. In this regard, the display of difference Fourier maps can highlight whether the regions covered by the large ADPs clearly contain more than one electron density maximum. In such cases, the modeling of multiple atomic positions should be attempted, assisted by the careful use of chemically sound crystallographic restraints/constraints. The large contrast in electron density between framework and pores in the unit cell could make it difficult to locate solvent molecules, or counterions in the case of charged frameworks. This effect is even more pronounced for MOFs made of heavy metal elements. Here, some of the lighter atoms might not be easily evident in the difference Fourier maps, where only areas with small values of electron density are discernible. The presence of atoms with partial occupancies (either not present in every single unit cell, or having split positions) is also common, most particularly for atoms belonging to adsorbed guests, or products of postsynthetic modifications. In these cases, the quantification of the atomic composition or reaction yield should always be corroborated with additional analysis.
Similarly, in the case of structures that contain metal elements with close atomic numbers, and therefore similar scattering factors, X-ray diffraction will not straightforwardly provide a definitive assignment of the atomic species. The use of solvent mask procedures (59) should be opted for critically and only when, in the latest steps of the refinement, every attempt to locate the atomic positions of the molecules in the pores has failed. In any event, the provided crystallographic files should incorporate details of the solvent mask procedure. We also recommend including the refinement indicators obtained before and after applying the solvent mask in the reported crystallographic tables. When dealing with limited data quality as in the cases of crystals that only diffract to limited resolution, the use of restraints/constraints during the refinements is helpful, for example, to refine some molecules as rigid bodies. Whenever used, details on the employed restraints and constraints must be clearly explained and justified in the experimental methods description.
Any newly disclosed crystal structure should adhere to International Union of Crystallography (IUCr) recommendations regarding data reporting in the form of crystallographic information files (CIFs). The provided CIFs must include the experimental structure factors and refinement instructions, which can be easily implemented with modern refinement programs. They must be validated accordingly by the unified CheckCIF procedure (https://checkcif.iucr.org/). When discussing any value obtained from SCXRD, such as distances or angles, their corresponding estimated standard deviations (esd) must be given. Main data collection and refinement indicators should be clearly accessible to the readers. This includes wavelength, source type, maximum resolution reached for I/σ > 2, temperature, atmosphere, instrument with source and detector, unit cell parameters, cell volume, space group, R1, wR2, GOF, largest diffraction peak and hole, and Flack parameter in the case of a non-centrosymmetric structure. When using a solvent mask, the refinement indicator values obtained before and after applying the mask should be given for comparison. Researchers using SCXRD can find further detailed guidelines on structure optimization, validation, and avoidance of common pitfalls in recent crystallographic educational articles. (60−62)
Finally, the interpretation of a refined crystal structure involves a process we call “reading a crystal structure”. This is the examination of directly bonded and nonbonded distances, and angles to determine whether they are reasonable and precedented. This process of familiarizing oneself with the structure uncovers any unusual findings if indeed they exist in the crystal. Often, a model can be helpful during this process.
Powder X-ray Diffraction (PXRD)
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According to the basic postulate of structural crystallography, “only one single chemically sound crystal structure exists that is compatible with the observed diffraction data”. (63) PXRD is thus invaluable in providing the unique footprint of any crystalline material. The identification of any reticular compound with PXRD is made by comparison of experimental and calculated PXRD patterns, and it is vital for the identification of any crystal phase in the sample, ensuring that no other crystalline solid is present in the bulk. Through the analysis of the diffraction profiles, PXRD also provides information on crystal size, as well as on the degree of crystallinity of the samples, or presence of partial disorder. PXRD can be also applied for structural elucidation when access to single crystals is not possible. Variable temperature PXRD is often used in the study of dynamic reticular structures and in the study of phase change. The interpretation of PXRD data can be rather challenging, and different approaches are possible for structure solution from powder diffraction data. The reader is referred to the specific literature on this topic. (64)
Acquisition and interpretation of PXRD data must be made considering the holistic nature of X-ray diffraction. Sample preparation might have a dramatic impact on the obtained pattern. When using a reflection configuration, the sample must be placed on a flat surface, and a sufficiently large amount must be used to decrease background contribution from the sample holder. When this is made challenging by the small amount of available sample, the use of low-background silicon holders is preferable, as well as, when available, the use of beam-limiting slits to reduce the illuminated area to the one covered by the sample. We recommend grinding the sample prior to depositing it on the holder, to homogenize particle sizes, thus reducing to some extent possible preferred orientation effects. The preparation of a fine powder is also crucial to ensure that the sample is properly flattened on the holder, so that its surface roughness is minimized to limit its contribution to the peak broadening when using a reflection configuration. The user also must be aware that an imprecise sample height introduces errors in the position of the peaks in the final diffractograms.
For air-stable MOFs or COFs, we strongly recommend collection of PXRD patterns on well-dried samples, and preferably after activation to facilitate the comparison with the calculated pattern, which often does not account for guest species in the pores. When dealing with air-sensitive samples, we recommend using sample holders specially designed for this purpose, to avoid any structural changes during the pattern acquisition. In these cases, the use of transmission geometries combined with the sample preparation in glass capillaries (Debye–Scherrer configuration) minimizes the exposure of the sample to the external environment, while also decreasing preferred orientation phenomena induced by the powder flattening during the sample preparation. The 2θ range for acquisition of PXRD patterns should be sufficiently large to cover a significant number of diffraction peaks. The lower limit should be in accordance with the expected position of the first diffraction peak. On the higher end, the 2θ range should be large enough to cover the possible presence of impurities with dense crystal structures and small lattices, such as metals or metal oxides. Keep in mind that the lattice parameters ultimately determine the position of the first diffraction peak, and thus a recommended range for the most widely used Cu Kα radiation is between 3° and 50° (corresponding to d = 29.45 and 1.82 Å, respectively). The experimental step size during the acquisition should be small enough to properly describe the shape of the diffraction peaks and disfavor overlap of different reflections having very similar d values. The instrumental set up greatly influences peak profile, and we therefore recommend a step size no larger than 0.03°. The acquisition time is surely influenced by the sample amount and its intrinsic diffractive power, but it is also largely dependent on the instrument source intensity and the quality of the detector. Generally speaking, acquisition time should be sufficiently large to properly resolve from the background all the peaks in the selected range.
Because of their structural features, most MOF and COF PXRD patterns show a large difference in intensities between low and high angle peaks. We advise not to report patterns where the first most intense peaks are evident, but the signal-to-noise ratio in high-angle areas is such that weaker peaks are not clearly resolved. We strongly advise against performing a background subtraction after data collection. If a large background contribution is present in the PXRD pattern due to the presence of solvent, this must avoided by using a dry sample, when possible. If the background contribution is still obvious with the dry sample, this could be indicative of the presence of an amorphous phase, or of limited sample crystallinity, and accordingly this information should not be removed from the pattern. The plot of the experimental pattern must allow the identification of diffraction lines that have close positions (avoid thick lines, see Figure 3). The origin of the structure taken for the calculation of the simulated powder pattern must be clearly specified with its corresponding database reference code and the bibliographic reference of its original journal article. In addition to the entire simulated pattern, the comparison graph should also include position marks for every Miller plane in the plotted range, demonstrating that every single peak in the experimental pattern is indexed.
Figure 3
Figure 3. Representation of PXRD patterns for MOFs and COFs. Comparison between the experimental and simulated patterns of MOF-520 (a). (65) Because of the large difference in relative intensities in different 2θ regions, a blown up area is required. A synchrotron collected (wavelength indicated) PXRD pattern of COF-112 (b). (66) In this case, a Pawley refinement can be made, since there are enough experimentally observed reflections. The nature of the refinement is indicated in the figure legend, and the image includes the calculated pattern for the corresponding model, for visual comparison of the expected relative intensities.
Since the relative intensities of the diffraction patterns are influenced by the presence of guest molecules, it should be clearly stated whether these are included in the model used for the pattern simulation. If noteworthy differences in relative intensities are attributed to the occurrence of preferred orientation, this hypothesis should be commented on and corroborated by microscopy measurements to show the relevant features of crystal morphology and size. Moreover, many programs used for simulating PXRD patterns allow the introduction of a preferred orientation factor. In these cases, calculated patterns with and without preferred orientation effects should be provided.
COF Structural Simulations
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Although 3D COF crystals suitable for SCXRD have been obtained, (67) and structure solutions using electron diffraction data have also proved feasible, (68,69) these techniques are not yet always possible. Structural elucidation of most new COFs therefore strongly relies on a combination of computer simulation and powder X-ray diffraction analysis. Structural simulation of COFs (and for microcrystalline MOFs) is typically accomplished by following a topological approach. (70) Here, crystal models are generated by placing the selected organic linkers at the position of the nodes and edges of the possible networks resulting from the geometry and connectivity of the building units. The models are geometrically optimized, and their PXRD patterns are thus calculated, and compared with the experimental ones. (70)
This approach exploits the unique features of reticular chemistry, namely, the formation of extended networks by strong bonds between selected building units, and it has been extremely successful in elucidating the structure of numerous COFs with a limited number of observable diffraction peaks. However, one must remember that during the structural simulation process several assumptions are made, such as the completeness of the bond formation reaction between linkers, or that the organic linkers do not undergo any fundamental geometrical alterations during the COF formation process. These points must consequently be corroborated with spectroscopic techniques, and all characterization results must be consistent with the features of the proposed crystal models. Moreover, one must ensure that after generation and optimization of models, these do not contain abnormal values of atomic bond lengths and angles, which could result from the incorrect assignment of unit cell parameters or space group.
Regarding the interpretation and comparison of the diffraction pattern calculated from the models, cell-restrained whole powder pattern decomposition (WPPD) refinements are commonly performed. Pawley and Le Bail are two variations of cell-restrained WPPD, (71) which were originally developed to extract peak intensities from powder diffraction patterns and subsequently to be used for structure solution. They require knowledge of the lattice parameters and space group to calculate the diffraction peak positions, information that for COFs is usually obtained from the computer-generated models. The pattern refinement process is thus applied to refine the initially proposed unit cell parameters. However, Pawley or Le-Bail methods do not consider atomic coordinates, and there is no structural information in these refinements. The results are only indicative of the validity of the lattice parameters, and they must not be taken as a measure of the quality of the proposed crystal structure. Moreover, because of the nature of these refinements, for those patterns with a small number of observable diffraction peaks, similarly good refinement values can be reached for different unit cells. Consequently, applying a Pawley or Le-Bail refinement is not informative, as low residual values are always obtained due to the dominating contribution of the background. In these cases of less than 10 diffraction lines, we discourage reporting Pawley or Le-Bail fittings, as they do not sufficiently support the correctness of the chosen unit cell and space group. The validation of a crystal structure determined by means of powder diffraction is made with the completion of a Rietveld refinement. (72) With the Rietveld method, atomic coordinates and other structural and profile variables are used to calculate the intensities of the simulated patterns. These atomic and profile variables are adjusted together to fit calculated and experimental whole patterns. Note that performing a meaningful Rietveld refinement requires a sufficient number of observable, well-defined diffraction peaks, which is not always feasible for many COFs.
In the report of any computer-generated COF crystal model, its three-letter code topology for which the model is based on should be indicated. (73,74) The crystal system, space group, and lattice parameters of the final model must be clearly specified. Models should be completed within a space group compatible with the symmetry of the selected framework topology, and organic linkers, avoiding the report of P1 models unless justified by the actual lack of symmetry on them. Entire structure data including atomic coordinates should be given in electronic format (such as cif). The comparison between experimental and calculated patterns should be made to facilitate the visual comparison of the relative intensity distribution. Considering that experimental diffraction peaks might be contributed to by more than one diffraction plane, instead of adding a single set of Miller indexes on top of an observed reflection, it is recommended that positions of the Miller planes be marked, and the calculated positions and relative intensities of the Miller indexes be given, preferably in a tabulated form.
The simulated pattern should be calculated in the absence of guest molecules and compared with an experimental pattern that equally corresponds to an activated sample. If guest species are part of the model (counterions, or other molecules determined to be present with other techniques), it must be clearly indicated. In the particular case of 2D COFs, the structural model of a layer can be accomplished in a straightforward manner following reticular chemistry principles. However, the determination of the stacking sequence (if any) is not evident, since there are only weak interactions between the layers. For these cases, it is necessary to complete multiple models with a different stacking sequence, such as staggered (AB) or eclipsed (AA) configurations, but also other intermediate cases. Including a third layer in the stacking sequence (i.e., ABC) might result in substantially different distribution of relative intensities. Multiple models should thus be considered during the structural analysis, with their corresponding comparison of calculated diffraction patterns. If two models present only small differences in the relative intensities, the assignment to one or another stacking sequence cannot be made with just PXRD analysis, and it must be supported by additional characterization results, such as thorough sorption studies. Having said this, it is important to recognize that deciphering stacking sequences in 2D COFs is an ongoing challenge, because of the inherent disorder along the stacking axis.
Scanning Electron Microscopy (SEM)
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SEM is widely used in reticular chemistry to investigate size, morphology, and surface elemental composition. (75) As far as the morphological analysis is concerned, conventional SEM analysis generally has a resolution down to a few tens of nanometers, which largely suffices for a reliable assessment of morphology and size in most cases. Concerning the elemental composition analysis, this relies on the detection of characteristic X-rays emitted from the superficial layers of the sample, known as energy-dispersive X-ray analysis (EDX). Although the thickness of the layer probed by EDX can vary depending on various sample and instrumental parameters, this analysis remains mostly limited to the surface, and it is semiquantitative. Therefore, its results should not be considered meaningful concerning the overall composition of the bulk material, for which inductively coupled plasma-optical emission spectroscopy (ICP-OES) or mass spectrometry (ICP-MS) and elemental analysis are more suited.
Before performing an SEM analysis on MOFs or COFs, two sample preparation steps must be followed: Sample drying and sample sputtering. The use of dry sample is essential as most SEM instruments operate in high vacuum conditions and must be protected against chemical contaminations. For this reason, special attention should be paid to the stability of the framework in such low pressures, which should be assessed by exposing the material to analogous conditions and verified by PXRD that no irreversible collapse occurred. Another essential step in the preparation of framework samples for SEM analysis is sputtering the sample with a conductive metallic or carbon film. This is made necessary by the commonly poor electron conductivity of porous materials, resulting in the accumulation of electrons on the sample surface due to their hampered discharge along the sample holder. These excessive charges can be easily recognized as excessively bright regions of the crystals compromising the resolution of the picture. There are, however, two cases when the sputtering treatment can compromise the entire analysis, and its use can be reasonably discarded. The first case is when the sample consists of small nanoparticles. Since the sputtered coating is usually between 5 and 10 nm thick, morphological features close to this range are unavoidably lost. A second case is when SEM is used to investigate the elemental composition by EDX analysis, and the emission signals of the analytes are overlapping with those of the conductive layer. In these cases, the resulting chemical information must be discarded and the sample reprepared for purely elementary examinations using either a different coating element or, in case this is unavailable, by avoiding the sputtering treatment.
Specific information needed for a meaningful report of SEM analysis must include acceleration voltage used for imaging and the one used for EDX. In case nonroutine conditions allowed on specifically designed instruments are used, such as mild pressures or high/low temperatures, their description must be added as well. As far as the data display is concerned, all SEM micrographs must include scale bars, possibly introduced automatically with the raw data reduction software. In any case, all the collected pictures must be included unedited, in full resolution, and with automatically generated scale bars in the Supporting Information file. When displaying any type of size comparison between different samples it is appropriate, scientifically expected, and intellectually honest to use pictures with identical scale bars (Figure 4).
Figure 4
Figure 4. (a–d) Four different types of pure-metal and mixed-metal ZIF-8 samples are shown with good clarity and information completeness. This is achieved by presenting several crystals and, when necessary, magnifications highlighting the morphology of single specimens. Note that each set of high- and low-magnification pictures has identical scale bar length (0.1 and 1 μm, respectively) to facilitate the comparison between different samples. Reproduced from ref (76) with permission from the Royal Society of Chemistry.
As for EDX maps and spectra, their use must be accompanied by the raw data in the Supporting Information file. Finally, local morphology and compositional analysis must be complemented with the same kind of information from a reasonably larger sample, which is therefore more representative of the bulk product. For instance, exemplary images of a few single crystals need to be compared with one or more pictures displaying a large multitude of crystals (a few tens at least) to show how the local information relates to the general characteristics of the sample.
Transmission Electron Microscopy (TEM)
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TEM is one of the most versatile techniques for the analysis of reticular frameworks as it can be used to obtain atomically resolved morphological, compositional, and crystallographic information in a single measurement session. Additionally, TEM instruments can also be employed to investigate particle density heterogeneity, bonding energies, and many other features whose analysis is not considered part of the routine practice. For these more advanced applications, readers can find valuable information in recent bibliography in the field. (77)
The exceptional precision of TEM analysis is balanced by its lack of representativeness of the bulk sample. This is due to the small amount of sample used for an analysis, usually a few micrograms, and the high probability of sample contamination, which is strongly influenced by how the sample preparation is conducted. Below, we are not covering the many important aspects of this step, as we assume every TEM user is thoroughly trained on, but we instead comment on some issues that are more specifically encountered in the analysis of reticular frameworks. In standard sample preparation protocols, the sample is crushed in an agate mortar with the aid of a few droplets of solvent. When this preparation procedure is planned, the chemical and architectural stability of the sample to such solvent-assisted grinding should be proven by comparing its PXRD profiles before and after the treatment. In cases where damage is certain or suspected, the sample should be deposited on the TEM grid by simple mechanical contact, for instance, by rubbing the grid gently on some powder lying on a cleaned glass slide. Concerning the TEM analysis, a distinctive trait of MOFs and COFs is their high beam sensitivity. This often causes sample amorphization and loss of morphological details within a few seconds of illumination. Current instrumentations are usually equipped with highly sensitive detectors, which when combined with low electron doses allow for the analysis of reticular solids without considerable damage. Nevertheless, while collecting images on particles, their diffraction must always be checked and documented, and in case no diffraction is observed, the pre-existing amorphous state of the sample must be confirmed by PXRD analysis. If the amorphization is induced by the electron beam, the significance of the morphological information must be commented on during the interpretation of the results. Beam damage can be minimized not only by decreasing the intensity of the beam, but also by selecting its energy. (78) In this respect, high energies, achieved by using a high acceleration voltage like 300 kV, can be used to minimize the probability of electron-matter inelastic scattering and the resulting ionization damage (radiolysis). However, high energy electrons can cause knock-on damage where atoms are extracted from the sample generating chemical and structural rearrangements. In general, molecular frameworks suffer mainly from radiolysis damage, so that higher energies might be preferable, but these aspects can differ from sample to sample and should be considered when choosing a specific acceleration voltage.
As far as the display of TEM images is concerned, the same general criteria outlined for SEM apply. This also transfers to the importance of reporting the high-tension value used for the analysis, the environmental conditions of the sample and the type of grid and sample holder that have been used. In general, EDX analyses should be considered indicative and not a reliable source of quantitative information for the elementary composition of the sample. In-zone diffraction patterns accompanying the images should contain the reciprocal lattice axes and/or the assignment of some relevant reflections to support the identification of the crystal orientation. In case a selected area aperture or other beam-limiting means is used, the portion of the sample that has been probed by diffraction must be highlighted in its picture (Figure 5).
Figure 5
Figure 5. Exemplary display of TEM imaging data of a reticular structure, UiO-66. The transmission image of the selected crystal (a) is accompanied by a further magnifications (b–c) of an highlighted area of (a), the diffraction pattern of the entire crystal with indexed reflections (d), and the FFT (e) of the high-resolution image shown in (b). Reproduced from ref (79) with permission from the Royal Society of Chemistry. (79)
Surface Area and Pore Size Distribution
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Permanent porosity is one of the intrinsic properties of reticular compounds, and measuring adsorption isotherms is the standard practice to confirm their porosity. On the basis of the adsorption isotherms of MOFs and COFs, the surface area, pore size distribution, and pore volume can be obtained. Before adsorption studies on other gases and kinetic breakthrough measurements, N2 or Ar adsorption should be run at low pressure and low temperature to provide a basic porosity profile of the compound. (1,17) Reporting the surface area and pore volume of structures based on structure modeling should not replace the experimental gas adsorption studies (Figure 6).
Figure 6
Figure 6. Low-pressure Ar adsorption isotherm of IRMOF-74-IV at 87 K (a). (80) 65 adsorption data points (P/P0 from 1.3 × 10–5 to 0.99) and 15 desorption data points were collected. Five continual points at the P/P0 range from 7.85 × 10–2 to 1.73 × 10–1 were used for BET surface area calculation (b). The specific BET surface area of IRMOF-74-IV is 2516 m2 g–1, with a correlation coefficient R being 0.999967. The C constant in the BET equation is 19.345. Pore distribution profile of IRMOF-74-IV using the NLDFT model from the Ar adsorption data (P/P0 from 10–5 to 0.99) at 87 K (calculation model: Ar at 87 K zeolites/silica based on a cylindrical pore model; (c)). The fitting error between experimental isotherm and that based on NLDFT model is 0.819%.
A good adsorption isotherm on reticular structures requires enough sample loading and complete sample activation. By evaluating the PXRD pattern of materials after activation and its preliminary adsorption data, the activation method should be optimized to obtain frameworks with preserved integrity and surface area comparable to the calculated value from the structural model. It is worthy of note that for the N2 or Ar adsorption isotherm at 77 or 87 K, data points at P/P0 as low as 10–7 or 10–5, respectively, are necessary for surface area and pore size distribution analysis in high quality. This is the gold standard for measuring permanent porosity on microporous structures. MOFs with dynamic structural change require a longer equilibration time, and the data collection strategy should be reported.
A comprehensive description of the physisorption isotherm type and hysteresis feature (if any) is indispensable. When the Brunauer–Emmett–Teller (BET) method is used to report the surface area, the limitation of the model should be understood. (81,82) For most structures with micropores, data from low pressure range (P/P0 < 0.1) in which the term V(1 – P/P0) continuously increases with P/P0, rather than the classical range (P/P0 = 0.05–0.3), should be used in the BET equation. A correlation coefficient greater than 0.995 and a positive C value are the gold standards for the multipoints BET method, and they should be reported along with the data point range and the corresponding BET surface area.
Authors should be aware that the pore distribution analysis results are strongly influenced by the model selection and accuracy of the parameters (pore shape, size, and the main interactions between adsorbent and adsorbate). (83) We advise listing the full information on the pore distribution analysis, including calculation methods, application pore size range, adsorbate, pressure range used, and fitting error. For example, a proper description reads: “The pore size distribution from 0.35 to 100 nm of MOF-A was analyzed by the non-local density functional theory (NLDFT) model from the Ar adsorption data (P/P0 from 10–5 to 0.995) at 87 K (calculation model: Ar at 87 K zeolites/silica based on a cylindrical pore model). The fitting error between experimental isotherm and that based on NLDFT model is 0.189%.” The criteria to choose a proper model is not how your pore distribution analysis fit the new crystal structure, since the material may have a different pore distribution due to model limitation, potential structural change, or unsuccessful activation. NLDFT and grand canonical Monte Carlo (GCMC) models are believed to describe the fluid state in the micropores of MOFs and COFs better than classical methods, such as the Barrett–Joyner–Halenda (BJH) method. While there is no kernel developed specifically for reticular structures yet, multiple models need to be investigated, and a comparison between the measured isotherm and the modeled isotherm is important to judge the confidence of the pore distribution result. A fitting error as low as 1% is considered acceptable, and special attention should be paid to the isotherm in the low P range for microporous samples.
The pore volume in framework structures is calculated from the total adsorbed gas volume when P/P0 approaches 1.0. Micrometer sized crystals usually have negligible external surface areas, and typically a P/P0 of 0.90–0.95 is used for the pore volume calculation. Some reticular structures and their composites feature very large macropores and interparticle pores, and the uptake curve goes up vertically at the tail end of the isotherm. In this case, the total volume calculation may not be accurate since the uptake value at this range tends to be arbitrary.
Thermogravimetric Analysis (TGA)
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TGA is used to measure mass loss in a sample over time as a result of temperature changes in a controlled and stable atmosphere. This method helps to quantitatively examine many processes, including the loss of water or solvent, decarboxylation, pyrolysis, oxidation, or other types of decomposition, and even evaporation and sublimation. Linear fits can be applied to the thermogravimetric thermal curve to extrapolate the temperatures of weight loss onset. (84,85)
At least two characteristic weight loss steps are observed in reticular structures. The first occurs at relatively low temperatures (ca. < 300 °C): This is the desorption of guest molecules inside the porous structure. The second step occurring at a higher temperature indicates framework degradation. This temperature is used as an indication of the thermal stability of the framework, but stability measurements must be confirmed by PXRD. The mass of the framework after combustion is also important, and finding the ratio between the weight loss due to the linker and the weight of the inorganic residue can be used to calculate the composition of the framework. When the ratio is compared to the ideal composition, in principle the number of defects (missing linkers and SBUs) can be determined.
Liquid and Solid-State Nuclear Magnetic Resonance (NMR)
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NMR spectroscopy is used to detect and quantify impurities incorporated in MOFs and COFs that might occur due to side reactions during their synthesis. For example, the commonly used solvent N,N-dimethylformamide (DMF) can formylate amino-functionalized linker molecules at elevated temperatures as was shown for UiO-66(Zr)-NH2 and MIL-101(Al)-NH2. (86) Furthermore, NMR spectroscopy is the method of choice to quantify the degree of postsynthetic modification or to evaluate the efficacy of purification. For application of liquid NMR spectroscopy, the framework needs to be digested. Usually, acidic solutions, such as D2SO4, DCl, or DF are used to digest the frameworks, (87) some of which require digestion by acid-free mixtures without causing damage to sensitive functionalities or mask hydrolyzable impurities. (85) It is often more difficult to find methods to appropriately digest those chemically robust COFs.
If for some reason a particular linkage (bonds forming between atoms of adjacent building units) is not decipherable by solution NMR of the digested frameworks, solid-state NMR provides a powerful tool not only to identify but also to quantify the organic components in MOFs and COFs. Detailed experimental parameters in cross-polarization magic angle spinning (CP-MAS) spectroscopy, such as spinning rate, pulse angle and width, contact time, and recycle delays, are essential for the reproducibility of solid-state NMR data. Authors are recommended to provide this information when publishing their results. Apart from the main and satellite peaks attributed to the product, any other peaks should be identified and discussed. The assignment of NMR peaks needs to be validated as the resonance signals for solids often deviate from those in solution. When the spectrum is compared to a simulation, modeling details should be specified. When the spectrum intensity is too weak due to low natural abundance of the nuclei of interest, isotope labeling is recommended. CP-MAS should be applied to both pristine reticular structures and those subjected to postsynthetic modifications. This analysis provides a quantitative measure of conversion, (88) which becomes very important in the case where the functional groups do not survive in acids and could not be quantified using solution NMR on the acid-digested frameworks.
Elemental Analysis
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The weight percent of metal, carbon, hydrogen, nitrogen, and sulfur should be provided using chemical analysis and ICP-OES/MS. The values should be reported along with those calculated from an accurate formula. The elemental composition obtained from the surface using X-ray photoelectron spectroscopy (XPS) and EDX are not quantitatively reliable as the elemental information does not come equally from all regions of the sample, hence limiting the accuracy of these techniques, which should not replace the standard elemental analysis methods. We suggest measurement of the CHNS percentages should be within 0.40% (absolute) of the calculated values as has been commonly practiced and recommended in organic chemistry. If the deviation value exceeds the limit, a formula reflecting another possible structure should be proposed
Considering the porous nature of MOFs and COFs, measurements should be performed on the fully activated sample, with no guests remaining in the pores. Otherwise, a large degree of inaccuracy is introduced in the found formula. For instance, a sample based on MOF-5 (18) [found (%): C, 38.50; H, 2.28; N, 1.71; Zn, 31.56] could be interpreted as MOF-5 containing 0.9 DMF per formula unit [Zn4O(O2C−C6H4−CO2)3]·0.9{CHO−N(CH3)2}, Calc. (%): C, 38.37; H, 2.21; N, 1.51; Zn, 31.31], or MOF-5 with ∼3.3% linker vacancy and 1.1 DMF per formula unit [Zn4O(O2C−C6H4−CO2)2.9]·1.1{CHO−N(CH3)2}, Calc. (%): C, 38.16; H, 2.33; N, 1.85; Zn, 31.37]. Coordinated solvent (such as H2O and C2H5OH) can be removed by activation, thus creating open metal sites in the framework. The uncoordinated metal sites may be saturated with moisture captured from the air, in which case sample handling should be done under inert atmosphere (e.g., glovebox). Given that reticular structures contain many different elements common between the framework and the guest molecules, we caution against the tendency to derive an empirical formula from elemental analysis that incorporates guest molecules. This aspect comes with the need to make sure that the sample analysis is performed on the fully activated framework.
Chemical Stability
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It is crucial to list the details of chemical stability measurements when performed in moisture (temperature, humidity, time), or in any liquid environment (media, pH, temperature, time). Some parameters, such as the amount of sample in certain amount of liquid, with or without guests in the pores, and the time interval between the media exchange, may profoundly affect the results. When setting up a standard chemical stability study, we strongly suggest that it involves the conditions that are required by the intended application of the framework.
We propose the use of three different quality indicators to support the stability of reticular structures. First, crystallinity retention: the PXRD pattern of the sample before and after exposure to chemical agents should be carefully compared under similar data collection conditions to make sure the intensity of the peaks is maintained and no new peaks emerge. Alteration in peak intensity and width could indicate amorphization and, possibly, destruction of the framework, and it should be discussed accordingly. Second, porosity retention: A precise description of any change in surface area, pore size distribution, and pore volume should be made as this indicates compromised porosity and framework integrity. Third, weight retention: For measurements done in liquid media, weight loss of the sample could be obtained by measuring the concentration of metal and/or linker in the supernatant. Considering the structural diversity and complexity of reticular solids, a quantitative evaluation of these three indicators is highly recommended. When possible, the mechanism of degradation or reasons for the stability of the examined frameworks should be discussed. (89)
Computational Modeling of Reticular Frameworks
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Computational modeling of reticular structures has been usefully employed in the last 10–15 years. (90−93) Multiscalar levels of simulations are employed ranging from quantum chemical calculations to explore catalysis in MOFs (94) and their conductive and magnetic properties, to classical simulations based on force fields (95−97) to investigate gas storage, adsorption, separation, and transport. These simulations are very useful because they allow the community to predict novel compounds, their properties, and reactivity before they have been made in the laboratory, but they also pose a challenge because of the complexity of these systems and related phenomena. As was stated recently: “Electronic structure calculations have become ubiquitous, with much of the work published in the field (chemistry) today making use of theoretical results. [···] We find ourselves at a perceived turning point where quantum chemical calculations are believed by many to be on par with experimental methods.” (98)
To make progress in computational and theoretical studies, it is important that the protocols of the simulations fulfill quality indicators and can be reproduced by different research groups. It is a best practice in computational chemistry, both in electronic structure theory and classical simulations, to benchmark methods. In order for these calculations to be reliable, a systematic validation has to be performed, and the limitations of the methods and models should be disclosed. Researchers should not only report results that agree with experiments as this will not necessarily be a quality indicator for the calculations. In the spirit of this article, we encourage both reviewers and editors to appreciate and value the challenges involved with calculations.
In the following, some examples will be presented on how to implement best practices in reticular systems. Let us start with an example of catalysis in MOFs. One should carefully describe their models and methods. It is a good practice to provide in the Supporting Information of a journal article one or more examples of relevant inputs/outputs of the calculations and the structural information on all the species investigated, i.e., coordinate files. When reporting the results one should always keep in mind the scenario in which someone from a different group would like to replicate them and should provide all the necessary information to do so. It is important to discuss the motivation for the choice of a model (for example, did you set up a finite cluster model or a periodic one of a MOF or COF, and why did you do so?) as well as the motivation for the choice of a level of theory, and one should not just state “that was used in previous studies”. (99) A best practice would be to compare different models (cluster vs periodic) and different methods (for example, different density functionals and different basis sets). Validation against existing experimental data is also a useful approach for assessing the quality of a given model and method. However, one should bear in mind that experiments and calculations may be carried out under different conditions. The main goal of theory is to make predictions, provide reasonable explanations, and inspire new thinking.
When one studies reactivity, the spin states of the species involved along the reaction should be reported together with relevant thermochemical quantities, e.g., enthalpies and free energies. One should be careful in describing the conditions in which the various thermodynamic contributions have been calculated (for example, temperature, pressure, and how vibrational frequencies have been accounted for to compute the vibrational partition function). The code used for these calculations and its version should be reported so that it can be replicated by others. The hardware such as type of processor and amount of RAM should also be described to give researchers an idea of the necessary amount of computational resources.
If one wishes to compute macroscopic properties, e.g., adsorption isotherms or other averaged properties in a MOF or COF, Monte Carlo or molecular dynamics simulations are usually performed. Force field development for reticular structures is an active area of research, and inconsistency issues among force fields may emerge. The force field employed in the simulations should be described, and all the relevant input and output files should be provided so that the calculations can be replicated. It is not uncommon that two different Monte Carlo codes, even using the same force field, give different results, depending on the specific sampling schemes used. Once a force field has been developed, it should be broadly tested with different codes to show that there is uniformity in the results. For the calculations to be fully reproducible, it is not enough to cite the reference of the force field, but rather all parameter values that are not part of the accepted standard should be reported in the Supporting Information. It is not uncommon that a small change in a parameter of a force field makes a result irreproducible, and this should be avoided.
Generally, it would be helpful if researchers create a repository with more information than what can be reported in the Supporting Information of a journal article. This repository should be made accessible to the community, especially when the research is conducted as part of a joint center involving many institutions and groups, where data sharing is particularly important.
Finally, it is a best practice to have more than one person working together on a computational project, if the project allows for such collaboration. The reason is that if two or more people work on the same project, even if from different angles, there will be more discussion and validation of the results. Moreover, this will foster collaboration and hopefully advance the level of the discovery. The emerging area of big data science, machine learning, and artificial intelligence in general is changing the way we make, analyze, and study reticular frameworks. (100) We expect that, in light of these developments, further elaboration on our standard practices will be made in due course.
Practice in Reporting Chemical Formulas
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The preparation of a new reticular compound comes with the task of assigning a term of identification for easy reference. Ideally, the identification should be unique and concise, and give justice to the complexity of the newly made structure. Finding the right balance between clarity and brevity is especially challenging for reticular structures, where identifiers should not only give information concerning the chemical composition, but also the connectivity of the constituents. In addition, identifiers have to account for structural complexities, such as heterogeneity and postsynthetic modifications.
In reticular chemistry, the naming of a compound starts with the chemical formula (Table 1), which describes the chemical composition of the structure at hand. The analytical techniques necessary to obtain the accurate chemical formula were treated in the sections above; we emphasize once more that the chemical formula should reflect the experimentally obtained chemical composition and not the “ideal” expected one. For example, the reaction of Zn(NO3)2·4H2O with benzene dicarboxylic acid under the reported reaction conditions gives Zn4N2O15C30H26. This chemical formula gives the exact composition of the framework structure. However, it provides the reader with little information on the molecular composition and connectivity of the reported structure.
Table 1. Examples of Chemical Formula, Molecular Formula, Reticular Formula, and Trivial Names for MOF-5·2DMF and COF-300 (18,101)
| MOFs | |
|---|---|
| chemical formula | Zn4N2O15C30H26 |
| molecular formula | [Zn4O(O2C−C6H4−CO2)3]·2{CHO−N(CH3)2} |
| reticular formula | [(Zn4O)(BDC)3]·2DMF |
| trivial name | MOF−5·2DMF |
| COFs | |
|---|---|
| chemical formula | C41H28N4 |
| molecular formula | [C−(C6H4−NCH)4][(−C6H4−)]2 |
| reticular formula | [(TAM)(BDA)2]imine |
| trivial name | COF-300 |
For this reason, we recommend a molecular formula [Zn4O(O2C−C6H4−CO2)3]·{2CHO−N(CH3)2}, which clarifies the nature of the building units making up the structure. Since the molecular formula can become elaborate, the reticular chemistry community has practiced writing a reticular formula [(Zn4O)(BDC)3]·2DMF, where the building units and guests are abbreviated for clarity. Generally, we recommend that the multimetallic SBU be distinguished from the organic linker and from any guests that might occupy the pores of the framework.
Note that when the framework contains guests, such as DMF, it is preceded by a dot in both the molecular and the reticular formulas. If the structure contains terminal ligands (such as H2O) bound to the backbone, as in HKUST-1, this is accounted for in the formula before the dot: [Cu3(BTC)2(H2O)3]·xG, where G stands for guest. (19) In the case of charged frameworks, the formula must also incorporate the counterions following the same convention, might they be ligands or guests.
For COFs, to specify the connectivity of the organic linkers, the reticular formula includes the type of linkage in the subscript. For example, the condensation of benzene dialdehyde (BDA) with tetra-(4-aminophenyl)-methane (TAM) affords the chemical formula C41H28N4, which corresponds to the molecular formula [C−(C6H4−NCH)4][(−C6H4−)]2 and the reticular formula of [(TAM)(BDA)2]imine. Again, solvent or guest molecules that are part of the chemical formula should be specified as is the case for MOFs.
In addition to the molecular and reticular formula, a trivial name is assigned to each compound. In the case of [(Zn4O)(BDC)3], it is MOF-5, and for [(TAM)(BDA)2]imine, it is COF-300. We recommend that these trivial names refer to the framework structure for easy reference, and in the case that any variations are made on the backbone, such as metalation and covalent functionalization, these should be appropriately appended to the trivial name. For example, MOF-5 was originally assigned to the zinc-containing structure, but recently a cobalt substituted derivative was reported. This is preferably referred to as Co-MOF-5. If its partial substitution, then the molar ratio should be indicated as a subscript x, Cox-MOF-5. (102)
Framework Components
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For reticular structures, it is useful to make the following distinctions to have consistency in reporting. We observed that these, on occasions, have been used interchangeably, and this has obscured their accurate meaning. First, linker/linkage/ligand: Linkers are organic components bearing strongly coordinating functional groups, such as carboxylates, azolates, phosphates, and catecholates, which are used to connect the inorganic SBUs into extended structures. Linkages are defined as the atoms involved in linking the binding groups from the linkers to the metals in the SBUs. For example, in MOF-74, (103) the linker is dihydroxyterepthalic acid, and the linkages are the Zn–O bonds made to the hydroxyls and carboxylates. Any solvent molecules bound to Zn, such as DMF, are ligands.
Second, COFs and porous polymers: COFs are defined as crystalline extended solids realized by linking only organic building units through covalent bonds between light elements (e.g., B, C, N, O, and Si). (1) Here, crystalline, covalently bonded, and extended are the three main prerequisites. The term “porous polymers” is usually used to refer to amorphous organic solids.
Third, MTV and solid solutions: Multivariate (MTV) frameworks have multiple types of functional groups and/or mixed metal components in the same structure. (104) The introduction of multiple functionalities and metals do not alter the connectivity (topology) of the underlying backbone structure. Multivariate components are thus occupying topologically equivalent positions. MTV frameworks should not be confused with solid solutions. The formation of solid solution requires the two constituents similar in size and shape, and partial or limited ranges of the constituents is far more common. A solid solution requires mutual solubility between the components, which implies exchangeability between them (as different metal atoms in alloys). (105) In a substitutional solid solution, the components are usually randomly distributed at sites, or ordered in a form of a supercell in some cases. On the other hand, in MTV frameworks, functionalities and metals with very different sizes and charges have proven to be compatible within one framework. The functional groups and metals are fixed at crystallographic positions by strong bonds, and the place swap is less likely.
Special Consideration in the Area of MTV-MOF
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The continuing intense interest in MTV frameworks has motivated us to suggest a standard practice in characterizing and reporting them. We use here MTV-MOFs as an illustrative example. Assessing bulk purity and homogeneity is not straightforward since MTV-MOFs share the same backbone with the simple component MOFs. It is extremely difficult, when not impossible to differentiate a pure phase MTV-MOF from a physical mixture of its corresponding simple component MOFs using only PXRD. The difficulty is to determine whether one obtains a MOF of many different kinds of linkers or a physical mixture of many MOFs, each of which is composed of only one kind of linker. The authors should perform high resolution elemental mapping on many different fragments of crystals. When advanced solid-state NMR and advanced fluorescent spectroscopic techniques are possible, mapping of organic linkers should be provided by analyzing the interactions between different functionalities to ensure both the bulk purity and the homogeneity (or heterogeneity) of the MTV-MOFs. (106,107) The nomenclature of MTV-MOFs should reflect the composition of different metals and linkers in the structure, rather than the input ratio of different metals and linkers used in the synthesis. For example, the ratio of Mg/Mn (45:55) in MTV-MOF-74 structure deviates from the input ratio of Mg/Mn (30:70), and the suggested formula and name for this MOF should be stated as (MgxMn1–x)2(DOBDC) (x = 0.45, DOBDC = 2,5-dioxidotere-phthalate) and Mg0.45Mn0.55-MOF-74.
Illustration of Frameworks
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The proverbial phrase “a picture is worth a thousand words” holds particularly true in reticular chemistry, where illustrations are essential to visualize the extension of a structure into 2D and 3D space. Reticular frameworks—and illustrations thereof—are typically founded in crystal structures obtained by diffraction techniques. Finding the right balance between detail and clarity is challenging, and we wish to take this opportunity to discuss the different illustration techniques that are available for MOFs and COFs.
First, it should be specified whether the structure is based on experimental data or theoretical models. Artistic modifications of the experimentally found crystal structure are discouraged, as it may detract from the power of data. The depiction of a reticular structure ideally contains three components (such as in Figure 7). First, the molecular building units of the MOF or COF are presented. For MOFs, the SBUs should be illustrated in a stick-and-ball representation, accompanied by a polyhedral model, and highlighted throughout the figure. The organic units in MOFs and COFs are illustrated in a ChemDraw-style (108) representation. (101,109) It is worthwhile to specify the linkage of the COF structures. Second, for both MOFs and COFs, it is advisable to give an intermediate illustration, emphasizing the first sphere connectivity of the building blocks (SBUs and organic linkers). Third, we recommend providing an overall representation of the repeating unit (unit cell) of the crystal structure with special attention given to clarity. Depending on the focus of the framework representation, different graphical choices may be required to enhance the effectiveness of the illustration. Figure 8 provides the reader with some examples of how the same structure can be represented differently to highlight different aspects of the framework architecture, while achieving different degrees of clarity and level of detail. We recommend that the name and version of the program used to make the illustration be indicated in the figure caption or as a citation. (110−112) When a sphere (yellow in Figure 7–8) is placed in the pore of an illustrated framework, its size should be that of the largest sphere that can fit in that pore without touching the van der Waals radii of the framework atoms. A more detailed description of the graphical choices and technical guidelines for their use is provided in the Supporting Information. The underlying net of the MOF or COF, usually found in structural databases, such as the RCSR, should be given in a three-letter symbol (bold, lowercase). (73,74,113−115)
Figure 7
Figure 7. Example of a MOF and a COF depicted in three building-up stages (specified in the section above). (101,109−111) The unit cell is highlighted in dashed gray lines. Only one of the interpenetrated networks of COF-300 is shown.
Figure 8
Figure 8. Structure of ZIF-8 (sod) is used to show how different graphical options can enhance clarity while highlighting the type of information that the figure aims to provide. (112,115) The unit cell is highlighted in dashed black lines.
Scholarly Practice of Citations
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Scientists are arguably motivated by the thrill of discovery and to a certain extent by gaining credit for those discoveries. Nowhere more than in an emerging field is the need more pressing for authors to provide scholarly citations and comparisons of relevant work done by others. This topic has been discussed and presented in cogent articles over the years. (116) The recent rapid rise in the number of publications and the speed with which these are being communicated make it necessary to adhere to high standards of acknowledging others’ work. Here, we wish to encourage practices in citations that will enhance the quality of scientific reports. First, original citations: It is a scholarly practice to cite the work that influenced researchers’ thinking and their study. The practice of “political citations” is considered highly undesirable since it detracts from the scholarship of the scientific contribution. Second, reference “38(d)”: Key earlier contribution should be cited up front and not buried deeply in the reference list or not cited at all. Third, even comparisons: When comparisons are made to preceding work, it is fair and honest to make relevant and even comparisons. For example, if compound X’s performance is not as good as that of the tenth generation of compound Y (made by others), let us call it Y10; X should be compared to Y10 not the performance of the original version of Y. Fourth, early steps: In our eagerness to elevate our work, we unintentionally demote the importance and relevance of others’ work by not acknowledging it as an important “first” or “essential” step. Fifth, start from the same: When reproducing others’ work, it is necessary to start from their reported starting points and to follow closely their procedures before their results are deemed “irreproducible”. Sixth, substantiating claims by data: For example, we have heard it said, and occasionally seen it written, that “MOFs or COFs are expensive” or “unstable” without actual data (or citations) to support these generalizations. There is a wide range of variations of MOFs made from almost every metal in the periodic table, and many of which are made from inexpensive organic linkers (some of these linkers also form the basis for COFs). Which ones are expensive and, more to the point, how much do they cost? The answer almost always depends on the application of the reticular structure in question, its production scale, and many would argue, market forces.
Concerning stability, we all know examples of MOFs and more recently COFs exhibiting extraordinary thermal and chemical stability and that reticular structures have long moved beyond this question. (1,117) We note that stability or lack thereof find equally important utility as the intended function may require. Thus, we recommend that a MOF or COF be specified in the discussions concerning cost and stability, or any other attribute, and that it be backed by data.
Closing Remarks
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In this contribution, we briefly outlined some of what we think are worthwhile considerations concerning standard practices and quality indicators in the field of reticular chemistry. We are all “guilty” on occasion to have overlooked some of these points in our own work and publications, but certainly we all endeavor to continue to improve and build on such standard “best” practices as the field evolves. In no way does our presentation mean that this is the first and last word on this topic, but we sincerely and in good faith attempted to remind, inform, and hopefully inspire serious thinking around these important considerations for the ultimate objective of improving our way of acquiring and presenting data. With this contribution, each one of us has the opportunity to share it with potential authors and researchers embarking on presenting their work to the wider community.
Supporting Information
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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acscentsci.0c00592.
Description of data search for Figure 1; detailed description of graphical illustrations; color codes and settings for Figure 7 (PDF)
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.
Author Information
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- Cornelius Gropp - Department of Chemistry, University of California-Berkeley, Kavli Energy Nanoscience Institute at UC Berkeley, Berkeley, California 94720, United States;
http://orcid.org/0000-0002-5843-8158;
- Felipe Gándara - Instituto de Ciencia de Materiales de Madrid (ICMM)—Consejo Superior de Investigaciones Científicas (CSIC), C/Sor Juana Ineś de la Cruz, 3, Madrid 28049, Spain;http://orcid.org/0000-0002-1671-6260;
- Qiaowei Li - Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Fudan University, Shanghai 200433, China;http://orcid.org/0000-0002-5987-9465;
- Laura Gagliardi - Department of Chemistry, Minnesota Supercomputing Institute, and Chemical Theory Center, University of Minnesota, Minneapolis, Minnesota 55455, United States;http://orcid.org/0000-0001-5227-1396;
- Omar M. Yaghi - Department of Chemistry, University of California-Berkeley, Kavli Energy Nanoscience Institute at UC Berkeley, Berkeley, California 94720, United States;http://orcid.org/0000-0002-5611-3325;
C.G., Leopoldina postdoctoral fellow of the German National Academy of Science (LPDS 2019-02), acknowledges the receipt of a fellowship of the Swiss National Science Foundation (P2EZP2-184380). S.C. acknowledges the Research Foundation Flanders (FWO) for supporting his research (Project 12ZV120N). S.W. acknowledges funding from the Basque Government Industry Department under ELKARTEK and HAZITEK programs. F.G. acknowledges funding from the Spanish Research Agency (AEI, CTQ2017-87262-R, EUR2019-103824), and Ramón y Cajal program (RyC-2015-18384). Q.L. acknowledges the National Natural Science Foundation of China (21922103 and 21961132003) for supporting his research. L.G. acknowledges the Inorganometallic Catalyst Design Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (DE-SC0012702), and the Nanoporous Materials Genome Center, funded by the U.S. Department of Energy, Office of Basic Energy Sciences, under Award DE-FG02-17ER16362, as part of the Computational Chemical Sciences Program. O.M.Y. acknowledges the support and collaboration as part of UC Berkeley-KACST Joint Center of Excellence for Nanomaterials for Clean Energy Applications, King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia.
Acknowledgments
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We thank Mr. Hao Lyu (Yaghi Laboratory) for his help in mapping the institutions involved in reticular chemistry (Figure 1), Dr. Markus Kalmutzki for providing guidelines for the color codes of illustration practices (Figure 7), Professor Lars Öhrstrom, Dr. Francoise Mystere Amombo Noa, and Dr. Zhe Ji for insightful comments on the manuscript, and Dr. Lac Ha Nguyen for useful comments on the illustrations. S.C. thanks Dr. Arianna Lanza for valuable discussions on TEM analysis of MOFs. S.W. thanks Dr. Henrik Hintz for useful discussions on liquid-state NMR analysis.
References
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This article references 117 other publications.
- 1Introduction to Reticular Chemistry: Metal-Organic Frameworks and Covalent Organic Frameworks; Yaghi, O. M.; Kalmutzki, M. J.; Diercks, C. S. Wiley-VCH: Weinheim, 2019.
- 2Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Reticular synthesis and the design of new materials. Nature 2003, 423, 705– 714, DOI: 10.1038/nature01650[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXksV2itro%253D&md5=2417c5adb0e948350d3d62350c8cd7eaReticular synthesis and the design of new materialsYaghi, Omar M.; O'Keeffe, Michael; Ockwig, Nathan W.; Chae, Hee K.; Eddaoudi, Mohamed; Kim, JaheonNature (London, United Kingdom) (2003), 423 (6941), 705-714CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)A review. The long-standing challenge of designing and constructing new cryst. solid-state materials from mol. building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: the authors call this approach reticular synthesis. This chem. has yielded materials designed to have predetd. structures, compns. and properties. In particular, highly porous frameworks held together by strong metal-O-C bonds and with exceptionally large surface area and capacity for gas storage were prepd. and their pore metrics systematically varied and functionalized.
- 3Nimmermark, A.; Öhrström, L.; Reedijk, J. Metal-ligand Bond Lengths and Strengths: Are they Correlated? A detailed CSD Analysis. Z. Kristallogr. - Cryst. Mater. 2013, 228, 311– 317, DOI: 10.1524/zkri.2013.1605[Crossref], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmt1Wiu7s%253D&md5=5cdbba4e536174d76bf763551f531956Metal-ligand bond lengths and strengths: are they correlated? A detailed CSD analysisNimmermark, Anders; Oehrstroem, Lars; Reedijk, JanZeitschrift fuer Kristallographie - Crystalline Materials (2013), 228 (7), 311-317CODEN: ZKCMAJ; ISSN:2194-4946. (Oldenbourg Wissenschaftsverlag GmbH)Structure data on metal-alkoxides, metal-alc., metal-carboxylates, metal-carboxylic acid, metal-azolate and metal-azole coordination compds. from the Cambridge Structural Database (CSD) were analyzed in terms of bond lengths. In general the anionic ligands form shorter metal-ligand bonds by about 0.02-0.05 Å compared to neutral ligands, a clear indication of a charge contribution to the bonding interactions. This small difference is not, however, deemed as sufficient to generate two distinct classes of metal-ligand bonding. Instead, the anionic ligands can be viewed as having "charge assisted" metal-ligand bonding, corresponding to the same term used for "charge-assisted hydrogen bonding".
- 4Kinoshita, Y.; Matsubara, I.; Higuchi, T.; Saito, Y. The Crystal Structure of Bis(adiponitrilo)copper(I) Nitrate. Bull. Chem. Soc. Jpn. 1959, 32, 1221– 1226, DOI: 10.1246/bcsj.32.1221[Crossref], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF3cXovFKntg%253D%253D&md5=962ef78a85c6f22b54ea134d0da0f7ceThe crystal structure of bis(adiponitrilo)copper(I) nitrateKinoshita, Yukio; Matsubara, Ikuo; Hibuchi, Taiichi; Saito, YoshihikoBulletin of the Chemical Society of Japan (1959), 32 (), 1221-6CODEN: BCSJA8; ISSN:0009-2673.cf. preceding abstr. The crystal structure of bis(adiponitrilo)copper(I) nitrate was detd. by 2-dimensional Fourier methods. The cell is orthorhombic Pnnn, with 2 mols. per unit cell of dimensions: a = 9.41 ± 0.02, b = 13.73 ± 0.02, and c = 5.85 ± 0.01 A. A mean isotropic temp. factor with B = 3.0 sq. A. was applied for the 3 principal zones. Final values of R = .sum.‖F0| - |Fc‖/.sum.|F0| were 0.107, 0.116, and 0.112 for (hk0), (h0l), and (0kl), resp., with a weighted mean value of 0.110. The crystal consists of infinite 3-dimensional networks of complex ions, [Cu(NC-CH2-CH2-CH2-CH2CN)2]n+n, and nitrate ions. The Cu atom is tetrahedrally surrounded by 4 N atoms at a distance of 1.98 A. Each adiponitrile mol. is co.ovrddot.ordinated to 2 different Cu atoms forming a planar zigzag configuration of methylene groups. Thus, the Cu atoms and the ligand mols. form a complicated 3-dimensional 4-connected network. The nitrate ions are perpendicular to the a-axis, and seem to have statistical azimuthal orientations in the crystal and have apparent symmetry 222. All the atoms in the group Cu-N-C-C lie approx. on a straight line and the observed C-N distance is 1.13 A., suggesting that the bond character in the C-N group may be expressed by C≡N. C-C distances of 1.54, 1.50, and 1.53 A. were observed. The mechanism of cuprous-ion dyeing of polyacrylonitrile fibers is considered.
- 5Tomic, E. A. Thermal Stability of Coordination Polymers. J. Appl. Polym. Sci. 1965, 9, 3745– 3752, DOI: 10.1002/app.1965.070091121[Crossref], [CAS], Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF28XmtVeiug%253D%253D&md5=40097e0f519110a1902e9471abf89083Thermal stability of coordination polymersTomic, E. A.Journal of Applied Polymer Science (1965), 9 (11), 3745-52CODEN: JAPNAB; ISSN:0021-8995.Polymers insol. in conventional solvents were formed between 3 ligands (1,5-dihydroxynaphthalene-2,6-dicarboxylic acid (I), pyromellitic acid (II), and 2,3,6,7-naphthalenetetracarboxylic acid) and selected metal ions, Zn, Ni, Al, Fe3+, Th, and U. The thermal stability of these chelates in air above 300° was evaluated. The Zn salt of I was more stable than the Fe and Ni polymers. Thermal stability was a function of the metal involved. A higher thermal stability resulted when metals incapable of changing their ionic valency, e.g. Zn or Th, were used. The Fe salt of I had a max. wt. loss of 82.4% while the Zn salt lost only 75%. With II, there was 100% wt. loss at 290°, but only 29% loss with a II-U polymer. Polymers contg. metals capable of redox reactions, e.g. Ni and Fe, decompd., while the Zn salt of I merely lost H2O.
- 6Aumüller, A.; Erk, P.; Klebe, G.; Hünig, S.; von Schütz, J. U.; Werner, H.-P. A Radical Anion Salt of 2,5-Dimethyl-N,N′-dicyanoquinonediimine with Extremely High Electrical Conductivity. Angew. Chem., Int. Ed. Engl. 1986, 25, 740– 741, DOI: 10.1002/anie.198607401
- 7Hoskins, B. F.; Robson, R. Infinite Polymeric Frameworks Consisting of Three Dimensionally Linked Rod-like Segments. J. Am. Chem. Soc. 1989, 111, 5962– 5964, DOI: 10.1021/ja00197a079[ACS Full Text
], [CAS], Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1MXks12rs7k%253D&md5=c1b3b761420baa7f79b0f58be519d396Infinite polymeric frameworks consisting of three dimensionally linked rod-like segmentsHoskins, Bernard F.; Robson, RichardJournal of the American Chemical Society (1989), 111 (15), 5962-4CODEN: JACSAT; ISSN:0002-7863.A new class of solids may be afforded by linking together tetrahedral or octahedral centers by rod-like connecting units. Substitution of the MeCN ligands in Cu(CH3CN)4BF4 by 4,4',4'',4'''-tetracyanotetraphenylmethane (L) has provided the 1st example of a deliberately designed framework of this type. The structure of CuLBF4.xPhNO2 was detd. by x-ray crystallog.; tetragonal I‾4m2, a 13.620(2), c 22.642(2) Å, Z = 2. The structure consists of an infinite, diamond-related, cationic framework of C[C6H4CN]Cu rods, which creates large adamantane-like voids of vol. approx. twice that of the framework itself. This material is unusual in that approx. 2/3 of the contents of what is undoubtedly a crystal are effectively liq., the large inter-framework spaces being occupied by disordered PhNO2 (≥7.7 C6H5NO2 per Cu) together with mobile BF4- ions. The solid undergoes ready anion exchange. - 8Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K. Preparation, Clathration Ability, and Catalysis of a Two-Dimensional Square Network Material Composed of Cadmium(II) and 4,4’-Bipyridine. J. Am. Chem. Soc. 1994, 116, 1151– 1152, DOI: 10.1021/ja00082a055[ACS Full Text], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2cXhsVGnt78%253D&md5=5af3fcd83e3709797b79fe9c9d22d26dPreparation, Clathration Ability, and Catalysis of a Two-Dimensional Square Network Material Composed of Cadmium(II) and 4,4'-BipyridineFujita, Makoto; Kwon, Yoon Jung; Washizu, Satoru; Ogura, KatsuyukiJournal of the American Chemical Society (1994), 116 (3), 1151-2CODEN: JACSAT; ISSN:0002-7863.A two-dimensional square network material {[Cd(4,4'-bpy)2](NO3)2}∞ (1) (bpy = bipyridine) was prepd. from Cd(NO3)2 and 4,4'-bpy. Having inner cavities surrounded by 4,4'-bpy units as shown by crystallog. anal., this material behaved like inorg. porous materials such as zeolites. Thus, the complex 1 easily formed the clathrate complex {[Cd(4,4'-bpy)2](NO3)2·2G}∞ (2,G = o-C6H4X2 or C6H5X, X = Br, Cl) with some arom. compds. and exhibited heterogeneous catalysis for cyanosilyation of aldehydes. X-ray diffraction study of 2 (G = o-C6H4Br2) showed a layered array of the two-dimensional network.
- 9Subramanian, S.; Zaworotko, M. J. Porous Solids by Design: [Zn(4,4′-bpy)2(SiF6)]n·xDMF, a Single Framework Octahedral Coordination Polymer with Large Square Channels. Angew. Chem., Int. Ed. Engl. 1995, 34, 2127– 2129, DOI: 10.1002/anie.199521271[Crossref], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXovVelu7s%253D&md5=b45bb78a4e426c05f0c83ed815d2942bPorous solids by design: [Zn(4,4'-bpy)2(SiF6)]n·xDMF, a single framework octahedral coordination polymer with large square channelsSubramanian, S.; Zaworotko, Michael J.Angewandte Chemie, International Edition in English (1995), 34 (19), 2127-9CODEN: ACIEAY; ISSN:0570-0833. (VCH)[Zn(4,4'-bpy)2(SiF6)]n·xDMF (4,4'-bpy = 4,4'-bipyridine) was prepd. from [Zn(H2O)6]SiF6. Its crystal structure was detd. in space group P4/mmm (R = 0.063). The channel structure of the extended polymer is described and the compd. is suggested as a prototype for a range of porous octahedral structures.
- 10Kitagawa, S.; Kondo, M. Functional Micropore Chemistry of Crystalline Metal Complex-Assembled Compounds. Bull. Chem. Soc. Jpn. 1998, 71, 1739– 1753, DOI: 10.1246/bcsj.71.1739[Crossref], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXls1aitLo%253D&md5=28ab44fe04d3a8e344e5c760c7c2355dFunctional micropore chemistry of crystalline metal complex-assembled compoundsKitagawa, Susumu; Kondo, MitsuruBulletin of the Chemical Society of Japan (1998), 71 (8), 1739-1753CODEN: BCSJA8; ISSN:0009-2673. (Chemical Society of Japan)A review with 108 refs. Syntheses of new porous frameworks with specific pore size and type are of considerable interest for the appearance of zeolite-like functionalities. It is useful to take advantage of metal complex-assembled compds. because of designable frameworks, high microporosity, and flexible frameworks based on a variety of coordination geometries of metal centers and multifunctionality of bridging org. parts. Many recent reports show that the synthesis procedures are developing from serendipitous to rational level. Therefore, the micropore chem. of metal complex-based assemblages is directed toward not only new frameworks but also functionalities such as gas and small mol. adsorption, ion exchange, heterogeneous catalysis, photo-chem. and -phys. properties. For chem. and phys. functionalities robustness of a framework is required even in the absence of guest mols. in the cavity. The stability is largely dependent on the structural dimensionality of the assemblages. A wide variety of structures of metal complex-based assemblages are listed and recent findings in this functional chem. are described.
- 11Structural Inorganic Chemistry; Wells, A. F., Ed.; Oxford University Press: Oxford, 1984.Google ScholarThere is no corresponding record for this reference.
- 12Hoffmann, R. How Should Chemists Think?. Sci. Am. 1993, 268, 66– 73, DOI: 10.1038/scientificamerican0293-66
- 13Jiang, J.; Zhao, Y.; Yaghi, O. M. Covalent Chemistry beyond Molecules. J. Am. Chem. Soc. 2016, 138, 3255– 3265, DOI: 10.1021/jacs.5b10666[ACS Full Text], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XisVWmt7g%253D&md5=b8466d5f42b760f6bf06da3ea685562dCovalent Chemistry beyond MoleculesJiang, Juncong; Zhao, Yingbo; Yaghi, Omar M.Journal of the American Chemical Society (2016), 138 (10), 3255-3265CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A review. Linking mol. building units by covalent bonds to make cryst. extended structures has given rise to metal-org. frameworks (MOFs) and covalent org. frameworks (COFs), thus bringing the precision and versatility of covalent chem. beyond discrete mols. to extended structures. The key advance in this regard has been the development of strategies to overcome the "crystn. problem", which is usually encountered when attempting to link mol. building units into covalent solids. Currently, numerous MOFs and COFs are made as cryst. materials in which the large size of the constituent units provides for open frameworks. The mol. units thus reticulated become part of a new environment where they have (a) lower degrees of freedom because they are fixed into position within the framework; (b) well-defined spatial arrangements where their properties are influenced by the intricacies of the pores; and (c) ordered patterns onto which functional groups can be covalently attached to produce chem. complexity. The notion of covalent chem. beyond mols. is further strengthened by the fact that covalent reactions can be carried out on such frameworks, with full retention of their crystallinity and porosity. MOFs are exemplars of how this chem. has led to porosity with designed metrics and functionality, chem.-rich sequences of information within their frameworks, and well-defined mesoscopic constructs in which nanoMOFs enclose inorg. nanocrystals and give them new levels of spatial definition, stability, and functionality.
- 14Basic Inorganic Chemistry; Cotton, F. A.; Wilkinson, G.; Gaus, P. L., Eds.; Wiley-VCH: Weinheim, 1994.Google ScholarThere is no corresponding record for this reference.
- 15Organic Chemistry: Structure and Function; Vollhardt, P., Schore, N., Eds.; Freemann and Company, New York, NY, 2018.Google ScholarThere is no corresponding record for this reference.
- 16Yaghi, O. M.; Li, G.; Li, H. Selective Binding and Removal of Guests in a Microporous Metal–Organic Framework. Nature 1995, 378, 703– 706, DOI: 10.1038/378703a0[Crossref], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXhtVSnt7rP&md5=b0f48a6fa756cb3acc150b91b847516eSelective binding and removal of guests in a microporous metal-organic frameworkYaghi, O. M.; Li, Guangming; Li, HailianNature (London) (1995), 378 (6558), 703-6CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)Microporous inorg. materials such as zeolites find widespread application in heterogeneous catalysis, adsorption and ion-exchange processes. The rigidity and stability of such frameworks allow for shape- and size-selective inclusion of org. mols. and ions. Analogous microporous structures based on org. building blocks have the potential for more precise rational design, through control of the shape, size and functionalization of the pores. Here we report the synthesis of a metal-org. framework designed to bind arom. guest mols. selectively. The basic building block is a sym. org. mol., which binds metal ions to form layers of the metal-org. compd. alternating with layers whose compn. is detd. by the functionalization of the starting mols. The layers create channels in which guest arom. mols. may be selectively bound. We show that the crystal lattice thus formed is thermally stable up to 350°C, even after removal of included guest mols., and that the inclusions can be selectively readsorbed.
- 17Li, H.; Eddaoudi, M.; Groy, T. L.; Yaghi, O. M. Establishing Microporosity in Open Metal–Organic Frameworks: Gas Sorption Isotherms for Zn(BDC) (BDC = 1,4-Benzenedicarboxylate). J. Am. Chem. Soc. 1998, 120, 8571– 8572, DOI: 10.1021/ja981669x[ACS Full Text], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXltVegtrk%253D&md5=30587bcdce6035f7b29177de9452e8a3Establishing Microporosity in Open Metal-Organic Frameworks: Gas Sorption Isotherms for Zn(BDC) (BDC = 1,4-Benzenedicarboxylate)Li, Hailian; Eddaoudi, Mohamed; Groy, Thomas L.; Yaghi, O. M.Journal of the American Chemical Society (1998), 120 (33), 8571-8572CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Microporous metal-org. frameworks with pores accessible in a zeolite-like fashion were prepd. The synthesis, structural characterization, and gas sorption isotherm measurements for the Zn(BDC) microporous frameworks of cryst. Zn(BDC)·(DMF)(H2O) (BDC= 1,4-benzenedicarboxylate).
- 18Li, H.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Design and Synthesis of an Exceptionally Stable and Highly Porous Metal-Organic Framework. Nature 1999, 402, 276– 279, DOI: 10.1038/46248[Crossref], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXnvFSiuro%253D&md5=68f27e20a7e4e15ea2c2f49a2a61e98aDesign and synthesis of an exceptionally stable and highly porous metal-organic frameworkLi, Hailian; Eddaoudi, Mohamed; O'Keeffe, M.; Yaghi, M.Nature (London) (1999), 402 (6759), 276-279CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)Open metal-org. frameworks are widely regarded as promising materials for applications in catalysis, sepn., gas storage and mol. recognition. Compared to conventionally used microporous inorg. materials such as zeolites, these org. structures have the potential for more flexible rational design, through control of the architecture and functionalization of the pores. So far, the inability of these open frameworks to support permanent porosity and to avoid collapsing in the absence of guest mols., such as solvents, has hindered further progress in the field. The authors report the synthesis of a metal-org. framework, Zn4O(BDC)3.(DMF)8.(PhCl) (named MOF-5, where BDC = 1,4-benzenedicarboxylate), which remains cryst., as evidenced by x-ray single-crystal analyses, and stable when fully desolvated and when heated up to 300°. This synthesis is achieved by borrowing ideas from metal carboxylate cluster chem., where an org. dicarboxylate linker was used in a reaction that gives supertetrahedron clusters when capped with monocarboxylates. The rigid and divergent character of the added linker allows the articulation of the clusters into a three-dimensional framework resulting in a structure with higher apparent surface area and pore vol. than most porous cryst. zeolites. This simple and potentially universal design strategy is currently being pursued in the synthesis of new phases and composites, and for gas-storage applications.
- 19Chui, S. S.-Y.; Lo, S. M.-F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. A Chemically Functionalizable Nanoporous Material [Cu3(TMA)2(H2O)3]n. Science 1999, 283, 1148– 1150, DOI: 10.1126/science.283.5405.1148[Crossref], [PubMed], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXhsFeitLc%253D&md5=8f6f372b015fa0e2bbb7e8bfd316b663A chemically functionalizable nanoporous material [Cu3(TMA)2(H2O)3]nChui, Stephen S.-Y.; Lo, Samuel M.-F.; Charmant, Jonathan P. H.; Orpen, A. Guy; Williams, Ian D.Science (Washington, D. C.) (1999), 283 (5405), 1148-1150CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Although zeolites and related materials combine nanoporosity with high thermal stability, they are difficult to modify or derivatize in a systematic way. A highly porous metal coordination polymer [Cu3(TMA)2(H2O)3]n (TMA is benzene-1,3,5-tricarboxylate) was formed in 80% yield. It has interconnected [Cu2(O2CR)4] units (R is an arom. ring), which create a three-dimensional system of channels with a pore size of 1 nm and an accessible porosity of ∼40% in the solid. Unlike zeolites, the channel linings can be chem. functionalized; for example, the aqua ligands can be replaced by pyridines. TGA and high-temp. single-crystal diffractometry indicate that the framework is stable up to 240°.
- 20Cui, Y.; Evans, O. R.; Ngo, H. L.; White, P. S.; Lin, W. Rational Design of Homochiral Solids Based on Two-Dimensional Metal Carboxylates. Angew. Chem., Int. Ed. 2002, 41, 1159– 1162, DOI: 10.1002/1521-3773(20020402)41:7<1159::AID-ANIE1159>3.0.CO;2-5[Crossref], [CAS], Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XivVykt7o%253D&md5=b573002d44007cf995760a35be95734bRational design of homochiral solids based on two-dimensional metal carboxylatesCui, Yong; Evans, Owen R.; Ngo, Helen L.; White, Peter S.; Lin, WenbinAngewandte Chemie, International Edition (2002), 41 (7), 1159-1162CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)A chiral two-dimensional network is the basis for the structure of a homochiral solid exploiting metal-carboxylate coordination. The synthesis involved enantiopure bridging ligands and metal-org. secondary building units, and resulted in ethoxy-protected BINOL functionalities pointing into the cavities in this cryst. chiral zeolitic material. The cobalt, manganese and nickel-derived complexes of (1S)-6,6'-dichloro-2,2'-diethoxy-1,1'-binaphthalene-4,4'-dicarboxylic acid were reported. The cobalt-derived complex of (1R)-6,6'-dichloro-2,2'-diethoxy-1,1'-binaphthalene-4,4'-dicarboxylic acid was also reported; using either the (1S)-isomer or the (1R)-isomer, supramol. enantiomers were obtained.
- 21Dinca, M.; Yu, A. F.; Long, J. R. Microporous Metal–Organic Frameworks Incorporating 1,4-Benzeneditetrazolate: Syntheses, Structures, and Hydrogen Storage Properties. J. Am. Chem. Soc. 2006, 128, 8904– 8913, DOI: 10.1021/ja061716i[ACS Full Text], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XmtVSjtLg%253D&md5=c33a3b55e4ff31ac354ecbdd5b636120Microporous Metal-Organic Frameworks Incorporating 1,4-Benzeneditetrazolate: Syntheses, Structures, and Hydrogen Storage PropertiesDinca, Mircea; Yu, Anta F.; Long, Jeffrey R.Journal of the American Chemical Society (2006), 128 (27), 8904-8913CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The potential of tetrazolate-based ligands for forming metal-org. frameworks of utility in hydrogen storage is demonstrated using 1,4-benzeneditetrazolate (BDT2-) to generate robust, microporous materials. Reaction of H2BDT with MnCl2·4H2O and Mn(NO3)2·4H2O in N,N-diethylformamide (DEF) produces the two-dimensional framework solids Mn3(BDT)2Cl2(DEF)6 (1) and Mn4(BDT)3(NO3)2(DEF)6 (2), whereas reactions with hydrated salts of Mn2+, Cu2+, and Zn2+ in a mixt. of methanol and DMF afford the porous, three-dimensional framework solids Zn3(BDT)3(DMF)4(H2O)2·3.5CH3OH (3), Mn3(BDT)3(DMF)4(H2O)2·3CH3OH·2H2O·DMF (4), Mn2(BDT)Cl2(DMF)2·1.5CH3OH·H2O (5), and Cu(BDT)(DMF)·CH3OH·0.25DMF (6). The method for desolvating such compds. can dramatically influence the ensuing gas sorption properties. When subjected to a mild evacuation procedure, compds. 3-6 exhibit permanent porosity, with BET surface areas in the range 200-640 m2/g. The desolvated forms of 3-5 store between 0.82 and 1.46% H2 at 77 K and 1 atm, with enthalpies of adsorption in the range 6.0-8.8 kJ/mol, among the highest so far reported for metal-org. frameworks. The desolvated form of 6 exhibits preferential adsorption of O2 over H2 and N2, showing promise for gas sepn. and purifn. applications.
- 22Jia, J.; Lin, X.; Wilson, C.; Blake, A. J.; Champness, N. R.; Hubberstey, P.; Walker, G.; Cussen, E. J.; Schröder, M. Twelve-connected Porous Metal-Organic Frameworks With High H2 Adsorption. Chem. Commun. 2007, 28, 840– 842, DOI: 10.1039/B614254K
- 23An, J.; Geib, S. J.; Rosi, N. L. Cation-triggered Drug Release from a Porous Zinc–Adeninate Metal–Organic Framework. J. Am. Chem. Soc. 2009, 131, 8376– 8377, DOI: 10.1021/ja902972w[ACS Full Text], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXms1Kntbw%253D&md5=e7c5bc9294614369af1be7c69a7198d5Cation-Triggered Drug Release from a Porous Zinc-Adeninate Metal-Organic FrameworkAn, Jihyun; Geib, Steven J.; Rosi, Nathaniel L.Journal of the American Chemical Society (2009), 131 (24), 8376-8377CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A porous anionic metal-org. framework, {[Zn8(ad)4(BPDC)6O]·8DMF·11H2O}n (bio-MOF-1; Had = adenine, H2BPDC = biphenyl-4,4'-dicarboxylic acid), constructed using adenine as a biomol. building block is described. The porosity of this material is evaluated, its stability in biol. buffers is studied, and its potential as a material for controlled drug release is investigated. Specifically, procainamide HCl is loaded into the pores of bio-MOF-1 using a simple cation exchange process. Exogenous cations from biol. buffers are shown to affect the release of the adsorbed drug mols.
- 24Zacher, D.; Shekhah, O.; Wöll, C.; Fischer, R. A. Thin Films of Metal–Organic Frameworks. Chem. Soc. Rev. 2009, 38, 1418– 1429, DOI: 10.1039/b805038b[Crossref], [PubMed], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXkvVamu7g%253D&md5=59eb12bf16cf57126492a7e6b38baf9aThin films of metal-organic frameworksZacher, Denise; Shekhah, Osama; Woell, Christof; Fischer, Roland A.Chemical Society Reviews (2009), 38 (5), 1418-1429CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The fabrication of thin film coatings of metal-org. frameworks (MOFs) on various substrates is discussed in this crit. review. Interestingly, the relatively few studies on MOF films that have appeared in the literature are limited to the following cases: [Zn4O(bdc)3] (MOF-5; bdc = 1,4-benzenedicarboxylate), [Cu3(btc)2] (HKUST-1; btc = 1,3,5-benzenetricarboxylate), [Zn2(bdc)2(dabco)] (dabco = 1,4-diazabicyclo[2.2.2]octane), [Mn(HCOO)], [Cu2(pzdc)2(pyz)] (CPL-1; pzdc = pyrazine-2,3-dicarboxylate, pyz = pyrazine), [Fe(OH)(bdc)] (MIL-53(Fe)) and [Fe3O(bdc)3(Ac)] (MIL-88B; Ac = CH3COO-). Various substrates and support materials have been used, including silica, porous alumina, graphite and org. surfaces, i.e. self-assembled monolayers (SAMs) on gold, as well as silica surfaces. Most of the MOF films were grown by immersion of the selected substrates into specifically pre-treated solvothermal mother liquors of the particular MOF material. This results in more or less densely packed films of intergrown primary crystallites of sizes ranging up to several μm, leading to corresponding film thicknesses. Alternatively, almost atomically flat and very homogeneous films, with thicknesses of up to ca. 100 nm, were grown in a novel stepwise layer-by-layer method. The individual growth steps are sepd. by removing unreacted components via rinsing the substrate with the solvent. The layer-by-layer method offers the possibility to study the kinetics of film formation in more detail using surface plasmon resonance. In some cases, particularly on SAM-modified substrates, a highly oriented growth was obsd., and in the case of the MIL-53/MIL-88B system, a phase selective deposition of MIL-88B, rather than MIL-53(Fe), was reported. The growth of MOF thin films is important for smart membranes, catalytic coatings, chem. sensors and related nanodevices (63 refs.).
- 25Sun, L.; Campbell, M. G.; Dincǎ, M. Electrically Conductive Porous Metal–Organic Frameworks. Angew. Chem., Int. Ed. 2016, 55, 3566– 3579, DOI: 10.1002/anie.201506219[Crossref], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XmslGisw%253D%253D&md5=185401e793b619c797286fe8df7c641eElectrically Conductive Porous Metal-Organic FrameworksSun, Lei; Campbell, Michael G.; Dinca, MirceaAngewandte Chemie, International Edition (2016), 55 (11), 3566-3579CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Owing to their outstanding structural, chem., and functional diversity, metal-org. frameworks (MOFs) have attracted considerable attention over the last two decades in a variety of energy-related applications. Notably missing among these, until recently, were applications that required good charge transport coexisting with porosity and high surface area. Although most MOFs are elec. insulators, several materials in this class have recently demonstrated excellent elec. cond. and high charge mobility. Herein, the authors review the synthetic and electronic design strategies that have been employed thus far for producing frameworks with permanent porosity and long-range charge transport properties. In addn., key expts. that have been employed to demonstrate elec. transport, as well as selected applications for this subclass of MOFs, are discussed.
- 26Côté, A. P.; Benin, A. I.; Ockwig, N. W.; O’Keeffe, M.; Matzger, A. J.; Yaghi, O. M. Porous, Crystalline, Covalent Organic Frameworks. Science 2005, 310, 1166– 1170, DOI: 10.1126/science.1120411[Crossref], [PubMed], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1WgtLnF&md5=e2e033fd4af37870fc73cbb18c1eaed1Porous, Crystalline, Covalent Organic FrameworksCote, Adrien P.; Benin, Annabelle I.; Ockwig, Nathan W.; O'Keeffe, Michael; Matzger, Adam J.; Yaghi, Omar M.Science (Washington, DC, United States) (2005), 310 (5751), 1166-1170CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Covalent org. frameworks (COFs) have been designed and successfully synthesized by condensation reactions of Ph diboronic acid {C6H4[B(OH)2]2} and hexahydroxytriphenylene [C18H6(OH)6]. Powder x-ray diffraction studies of the highly cryst. products (C3H2BO)6•(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P63/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temps. up to 500° to 600°C), permanent porosity, and high surface areas (711 and 1590 square meters per g, resp.).
- 27El-Kaderi, H. M.; Hunt, J. R.; Mendoza-Cortés, J. L.; Côté, A. P.; Taylor, R. E.; O’Keeffe, M.; Yaghi, O. M. Designed Synthesis of 3D Covalent Organic Frameworks. Science 2007, 316, 268– 272, DOI: 10.1126/science.1139915[Crossref], [PubMed], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXktVektbs%253D&md5=4197db9769708ec596162efd126cdca9Designed Synthesis of 3D Covalent Organic FrameworksEl-Kaderi, Hani M.; Hunt, Joseph R.; Mendoza-Cortes, Jose L.; Cote, Adrien P.; Taylor, Robert E.; O'Keeffe, Michael; Yaghi, Omar M.Science (Washington, DC, United States) (2007), 316 (5822), 268-272CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Three-dimensional covalent org. frameworks (3D COFs) were synthesized by targeting two nets based on triangular and tetrahedral nodes: ctn and bor. The resp. 3D COFs were synthesized as cryst. solids by condensation reactions of tetrahedral tetra(4-dihydroxyborylphenyl)methane or tetra(4-dihydroxyborylphenyl)silane and by co-condensation of triangular 2,3,6,7,10,11-hexahydroxytriphenylene. Because these materials are entirely constructed from strong covalent bonds (C-C, C-O, C-B, and B-O), they have high thermal stabilities (400° to 500 °C), and they also have high surface areas (3472 and 4210 square meters per g for COF-102 and COF-103, resp.) and extremely low densities (0.17 g per cubic centimeter).
- 28Wan, S.; Guo, J.; Kim, J.; Ihee, H.; Jiang, D. A Belt-shaped, Blue Luminescent, and Semiconducting Covalent Organic Framework. Angew. Chem., Int. Ed. 2008, 47, 8826– 8830, DOI: 10.1002/anie.200803826[Crossref], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsVCgtLbO&md5=30837c9b478fe26320304d7edcf7e267A belt-shaped, blue luminescent, and semiconducting covalent organic frameworkWan, Shun; Guo, Jia; Kim, Jangbae; Ihee, Hyotcherl; Jiang, DonglinAngewandte Chemie, International Edition (2008), 47 (46), 8826-8830CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Blue belt: Condensation polymn. of pyrene (blue) and triphenylene (green) monomers leads to the formation of a hexagonal mesoporous covalent org. framework. This material exists in a belt shape, absorbs photons over a wide wavelength range to emit them as blue luminescence, and is semiconducting, as well as being capable of repetitive on-off switching.
- 29Spitler, E. L.; Dichtel, W. R. Lewis Acid-catalysed Formation of Two-dimensional Phthalocyanine Covalent Organic Frameworks. Nat. Chem. 2010, 2, 672– 677, DOI: 10.1038/nchem.695[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpt1aksbY%253D&md5=cbb7ec00f7dbefa96c9521b7b80576f4Lewis acid-catalysed formation of two-dimensional phthalocyanine covalent organic frameworksSpitler, Eric L.; Dichtel, William R.Nature Chemistry (2010), 2 (8), 672-677CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Covalent org. frameworks (COFs) offer a new strategy for assembling org. semiconductors into robust networks with at. precision and long-range order. General methods for COF synthesis will allow complex building blocks to be incorporated into these emerging materials. Here we report a new Lewis acid-catalyzed protocol to form boronate esters directly from protected catechols and arylboronic acids. This transformation also provides cryst. boronate ester-linked COFs from protected polyfunctional catechols and bis(boronic acids). Using this method, we prepd. a new COF that features a square lattice composed of phthalocyanine macrocycles joined by phenylene bis(boronic acid) linkers. The phthalocyanines stack in an eclipsed fashion within the COF to form 2.3 nm pores that run parallel to the stacked chromophores. The material's broad absorbance over the solar spectrum, potential for efficient charge transport through the stacked phthalocyanines, good thermal stability and the modular nature of COF synthesis, show strong promise for applications in org. photovoltaic devices.
- 30Dogru, M.; Sonnauer, A.; Gavryushin, A.; Knochel, P.; Bein, T. A Covalent Organic Framework with 4 nm Open Pores. Chem. Commun. 2011, 47, 1707– 1709, DOI: 10.1039/c0cc03792c[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXht1WhtLw%253D&md5=14d4321cc0a17da6c766f2b1cba39b4cA covalent organic framework with 4 nm open poresDogru, Mirjam; Sonnauer, Andreas; Gavryushin, Andrei; Knochel, Paul; Bein, ThomasChemical Communications (Cambridge, United Kingdom) (2011), 47 (6), 1707-1709CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)The synthesis and characterization of a new mesoporous covalent org. framework BTP-COF is described, the latter having fully accessible pores with an open diam. of 4.0 nm.
- 31Lehn, J.-M. Supramolecular Chemistry—Scope and Perspectives Molecules, Supermolecules, and Molecular Devices (Nobel Lecture). Angew. Chem., Int. Ed. Engl. 1988, 27, 89– 112, DOI: 10.1002/anie.198800891
- 32Cohen, S. M. The Postsynthetic Renaissance in Porous Solids. J. Am. Chem. Soc. 2017, 139, 2855– 2863, DOI: 10.1021/jacs.6b11259[ACS Full Text], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFajtro%253D&md5=0f92baffa318d7117f1d557f1cb16b3eThe Postsynthetic Renaissance in Porous SolidsCohen, Seth M.Journal of the American Chemical Society (2017), 139 (8), 2855-2863CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A review. Metal-org. frameworks (MOFs) have rapidly grown into a major area of chem. research over the last two decades. MOFs represent the development of covalent chem. "beyond the mol." and into extended structures. MOFs also present an unprecedented scaffold for performing heterogeneous org. transformations in the solid state, allowing for deliberate and precise prepn. of new materials. The development of these transformations has given rise to the "postsynthetic renaissance", a suite of methods by which these materials can be transformed in a single-crystal-to-single-crystal manner. Postsynthetic modification, postsynthetic deprotection, postsynthetic exchange, postsynthetic insertion, and postsynthetic polymn. have exploited the unique features of both the org. and inorg. components of MOFs to create cryst., porous solids of unique complexity and functionality.
- 33Czaja, A. U.; Trukhan, N.; Müller, U. Industrial Applications of Metal–Organic Frameworks. Chem. Soc. Rev. 2009, 38, 1284– 1293, DOI: 10.1039/b804680h[Crossref], [PubMed], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXkvVamu7o%253D&md5=63295ce7e2fb393c1abecd7623bc9c58Industrial applications of metal-organic frameworksCzaja, Alexander U.; Trukhan, Natalia; Muller, UlrichChemical Society Reviews (2009), 38 (5), 1284-1293CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. New materials are prerequisite for major breakthrough applications affecting the daily life, and therefore are pivotal for the chem. industry. Metal-org. frameworks (MOFs) constitute an emerging class of materials useful in gas storage, gas purifn., and sepn. applications as well as heterogeneous catalysis. They not only offer higher surface areas and the potential for enhanced activity than currently used materials like base metal oxides, but also provide shape/size selectivity which is important both for sepns. and catalysis. In this crit. review an overview of the potential applications of MOFs in the chem. industry is presented. Furthermore, the synthesis and characterization of the materials are briefly discussed from the industrial perspective.
- 34Kim, H.; Yang, S.; Rao, S. R.; Narayanan, S.; Kapustin, E. A.; Furukawa, H.; Umans, A. S.; Yaghi, O. M.; Wang, E. N. Water Harvesting from Air with Metal-Organic Frameworks Powered by Natural Sunlight. Science 2017, 356, 430– 434, DOI: 10.1126/science.aam8743[Crossref], [PubMed], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXmvFejtLo%253D&md5=14666dd987441772addcc6bf9c70b02aWater harvesting from air with metal-organic frameworks powered by natural sunlightKim, Hyunho; Yang, Sungwoo; Rao, Sameer R.; Narayanan, Shankar; Kapustin, Eugene A.; Furukawa, Hiroyasu; Umans, Ari S.; Yaghi, Omar M.; Wang, Evelyn N.Science (Washington, DC, United States) (2017), 356 (6336), 430-434CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Atm. water is a resource equiv. to -10% of all fresh water in lakes on Earth. However, an efficient process for capturing and delivering water from air, esp. at low humidity levels (down to 20%), has not been developed. We report the design and demonstration of a device based on a porous metal-org. framework {M0F-801, [Zr604(0H)4(fumarate)6]} that captures water from the atm. at ambient conditions by using low-grade heat from natural sunlight at a flux of less than 1 sun (1 kW per square meter). This device is capable of harvesting 2.8 L of water per kg of MOF daily at relative humidity levels as low as 20% and requires no addnl. input of energy.
- 35Fathieh, F.; Kalmutzki, M. J.; Kapustin, E. A.; Waller, P. J.; Yang, J.; Yaghi, O. M. Practical Water Production from Desert Air. Sci. Adv. 2018, 4, eaat3198, DOI: 10.1126/sciadv.aat3198
- 36Hanikel, N.; Prévot, M. S.; Fathieh, F.; Kapustin, E. A.; Lyu, H.; Wang, H.; Diercks, N. J.; Glover, T. G.; Yaghi, O. M. Rapid Cycling and Exceptional Yield in a Metal-Organic Framework Water Harvester. ACS Cent. Sci. 2019, 5, 1699– 1706, DOI: 10.1021/acscentsci.9b00745[ACS Full Text], [CAS], Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1ersr%252FP&md5=438f12344a29096e3d34f2774cb9be74Rapid Cycling and Exceptional Yield in a Metal-Organic Framework Water HarvesterHanikel, Nikita; Prevot, Mathieu S.; Fathieh, Farhad; Kapustin, Eugene A.; Lyu, Hao; Wang, Haoze; Diercks, Nicolas J.; Glover, T. Grant; Yaghi, Omar M.ACS Central Science (2019), 5 (10), 1699-1706CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)Sorbent-assisted water harvesting from air represents an attractive way to address water scarcity in arid climates. Hitherto, sorbents developed for this technol. have exclusively been designed to perform one water harvesting cycle (WHC) per day, but the productivities attained with this approach cannot reasonably meet the rising demand for drinking water. This work shows that a microporous aluminum-based metal-org. framework, MOF-303, can perform an adsorption-desorption cycle within minutes under a mild temp. swing, which opens the way for high-productivity water harvesting through rapid, continuous WHCs. Addnl., the favorable dynamic water sorption properties of MOF-303 allow it to outperform other com. sorbents displaying excellent steady-state characteristics under similar exptl. conditions. Finally, these findings are implemented in a new water harvester capable of generating 1.3 L kgMOF-1 day-1 in an indoor arid environment (32% relative humidity, 27°C) and 0.7 L kgMOF-1 day-1 in the Mojave Desert (in conditions as extreme as 10% RH, 27°C), representing an improvement by 1 order of magnitude over previously reported devices. This study demonstrates that creating sorbents capable of rapid water sorption dynamics, rather than merely focusing on high water capacities, is crucial to reach water prodn. on a scale matching human consumption.
- 37Hanikel, N.; Prévot, M. S.; Yaghi, O. M. MOF Water Harvesters. Nat. Nanotechnol. 2020, 15, 348– 355, DOI: 10.1038/s41565-020-0673-x[Crossref], [PubMed], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXosFSlsL0%253D&md5=4b44b62ea400c397b047bdf69fd9cb6cMOF water harvestersHanikel, Nikita; Prevot, Mathieu S.; Yaghi, Omar M.Nature Nanotechnology (2020), 15 (5), 348-355CODEN: NNAABX; ISSN:1748-3387. (Nature Research)A review. The advancement of addnl. methods for freshwater generation is imperative to effectively address the global water shortage crisis. In this regard, extn. of the ubiquitous atm. moisture is a powerful strategy allowing for decentralized access to potable water. The energy requirements as well as the temporal and spatial restrictions of this approach can be substantially reduced if an appropriate sorbent is integrated in the atm. water generator. Recently, metal-org. frameworks (MOFs) have been successfully employed as sorbents to harvest water from air, making atm. water generation viable even in desert environments. Herein, the latest progress in the development of MOFs capable of extg. water from air and the design of atm. water harvesters deploying such MOFs are reviewed. Furthermore, future directions for this emerging field, encompassing both material and device improvements, are outlined.
- 38Purification of Laboratory Chemicals; Armarego, W. L. F., Perrin, D. D., Eds.; Butterworth-Heinemann: Woburn, MA, 2000.Google ScholarThere is no corresponding record for this reference.
- 39Bennett, T. D.; Cheetham, A. K. Amorphous Metal–Organic Frameworks. Acc. Chem. Res. 2014, 47, 1555– 1562, DOI: 10.1021/ar5000314[ACS Full Text], [CAS], Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXls12hsb0%253D&md5=411be02fc16485bcb9b5163c6b260cb0Amorphous Metal-Organic FrameworksBennett, Thomas D.; Cheetham, Anthony K.Accounts of Chemical Research (2014), 47 (5), 1555-1562CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. The prepn. of amorphous metal-org. frameworks (aMOFs) by introduction of disorder into their parent cryst. frameworks through heating, pressure (both hydrostatic and nonhydrostatic), and ball-milling is described. The main method of characterizing these amorphous materials (anal. of the pair distribution function) is summarized, alongside complementary techniques such as Raman spectroscopy. Detailed investigations into their properties (both chem. and mech.) are compiled and compared with those of cryst. MOFs, while the impact of the field on the processing techniques used for cryst. MOF powders is also assessed. The benefits amorphization may bring to existing proposed MOF applications are detailed, alongside the possibilities and research directions afforded by the combination of the unique properties of the amorphous domain with the versatility of MOF chem.
- 40Thornton, A. W.; Jelfs, K. E.; Konstas, K.; Doherty, C. M.; Hill, A. J.; Cheetham, A. K.; Bennett, T. D. Porosity in Metal–Organic Framework Glasses. Chem. Commun. 2016, 52, 3750– 3753, DOI: 10.1039/C5CC10072K[Crossref], [PubMed], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XoslWqtg%253D%253D&md5=1ec6c1023cf8026913a629e4b74a3c34Porosity in metal-organic framework glassesThornton, A. W.; Jelfs, K. E.; Konstas, K.; Doherty, C. M.; Hill, A. J.; Cheetham, A. K.; Bennett, T. D.Chemical Communications (Cambridge, United Kingdom) (2016), 52 (19), 3750-3753CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)The porosity of a glass formed by melt-quenching a metal-org. framework, has been characterized by positron annihilation lifetime spectroscopy. The results reveal porosity intermediate between the related open and dense cryst. frameworks ZIF-4 and ZIF-zni. A structural model for the glass was constructed using an amorphous polymn. algorithm, providing addnl. insight into the gas-inaccessible nature of porosity and the possible applications of hybrid glasses.
- 41Zhao, Y.; Lee, S.-Y.; Becknell, N.; Yaghi, O. M.; Angell, C. A. Nanoporous Transparent MOF Glasses with Accessible Internal Surface. J. Am. Chem. Soc. 2016, 138, 10818– 10821, DOI: 10.1021/jacs.6b07078[ACS Full Text], [CAS], Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlOgt77J&md5=b4deb1aa2357800d28bc790607b55f87Nanoporous Transparent MOF Glasses with Accessible Internal SurfaceZhao, Yingbo; Lee, Seung-Yul; Becknell, Nigel; Yaghi, Omar M.; Angell, C. AustenJournal of the American Chemical Society (2016), 138 (34), 10818-10821CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)While glassy materials can be made from virtually every class of liq. (metallic, mol., covalent, and ionic), to date, formation of glasses in which structural units impart porosity on the nanoscopic level remains undeveloped. In view of the well-established porosity of metal-org. frameworks (MOFs) and the flexibility of their design, we have sought to combine their formation principles with the general versatility of glassy materials. Although the prepn. of glassy MOFs can be achieved by amorphization of cryst. frameworks, transparent glassy MOFs exhibiting permanent porosity accessible to gases are yet to be reported. Here, we present a generalizable chem. strategy for making such MOF glasses by assembly from viscous solns. of metal node and org. strut and subsequent evapn. of a plasticizer-modulator solvent. This process yields glasses with 300 m2/g internal surface area (obtained from N2 adsorption isotherms) and a 2 nm pore-pore sepn. On a volumetric basis, this porosity (0.33 cm3/cm3) is 3 times that of the early MOFs (0.11 cm3/cm3 for MOF-2) and within range of the most porous MOFs known (0.60 cm3/cm3 for MOF-5). We believe the porosity originates from a 3D covalent network as evidenced by the disappearance of the glass transition signature as the solvent is removed and the highly cross-linked nanostructure builds up. Our work represents an important step forward in translating the versatility and porosity of MOFs to glassy materials.
- 42Banerjee, R.; Phan, A.; Wang, B.; Knobler, C.; Furukawa, H.; O’Keeffe, M.; Yaghi, O. M. High-Throughput Synthesis of Zeolitic Imidazolate Frameworks and Application to CO2 Capture. Science 2008, 319, 939– 943, DOI: 10.1126/science.1152516[Crossref], [PubMed], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhslOmtr8%253D&md5=5db725852aeb4ca63bea1883fecb0c77High-Throughput Synthesis of Zeolitic Imidazolate Frameworks and Application to CO2 CaptureBanerjee, Rahul; Phan, Anh; Wang, Bo; Knobler, Carolyn; Furukawa, Hiroyasu; O'Keeffe, Michael; Yaghi, Omar M.Science (Washington, DC, United States) (2008), 319 (5865), 939-943CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A high-throughput protocol was developed for the synthesis of zeolitic imidazolate frameworks (ZIFs). Twenty-five different ZIF crystals were synthesized from only 9600 microreactions of either Zn(II)/Co(II) and imidazolate/imidazolate-type linkers. All of the ZIF structures have tetrahedral frameworks: 10 of which have two different links (heterolinks), 16 of which are previously unobserved compns. and structures, and 5 of which have topologies as yet unobserved in zeolites. Members of a selection of these ZIFs (termed ZIF-68, ZIF-69, and ZIF-70) have high thermal stability (up to 390°) and chem. stability in refluxing org. and aq. media. Their frameworks have high porosity (with surface areas up to 1970 square meters per g), and they exhibit unusual selectivity for CO2 capture from CO2/CO mixts. and extraordinary capacity for storing CO2: 1 L of ZIF-69 can hold ∼83 L of CO2 at 273 K under ambient pressure.
- 43Wilmer, E. C.; Leaf, M.; Lee, C. Y.; Farha, O. K.; Hauser, B. G.; Hupp, J. T.; Snurr, R. Q. Large-scale screening of hypothetical metal–organic frameworks. Nat. Chem. 2012, 4, 83– 89, DOI: 10.1038/nchem.1192[Crossref], [CAS], Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVagtL3K&md5=3becbfed2fdacdb8b58146666da7c038Large-scale screening of hypothetical metal-organic frameworksWilmer, Christopher E.; Leaf, Michael; Lee, Chang Yeon; Farha, Omar K.; Hauser, Brad G.; Hupp, Joseph T.; Snurr, Randall Q.Nature Chemistry (2012), 4 (2), 83-89CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Metal-org. frameworks (MOFs) are porous materials constructed from modular mol. building blocks, typically metal clusters and org. linkers. These can, in principle, be assembled to form an almost unlimited no. of MOFs, yet materials reported to date represent only a tiny fraction of the possible combinations. Here, the authors demonstrate a computational approach to generate all conceivable MOFs from a given chem. library of building blocks (based on the structures of known MOFs) and rapidly screen them to find the best candidates for a specific application. From a library of 102 building blocks the authors generated 137,953 hypothetical MOFs and for each calcd. the pore-size distribution, surface area and methane-storage capacity. The authors identified over 300 MOFs with a predicted methane-storage capacity better than that of any known material, and this approach also revealed structure-property relations. Methyl-functionalized MOFs were frequently top performers, so the authors selected one such promising MOF and exptl. confirmed its predicted capacity.
- 44Nelson, A. P.; Farha, O. K.; Mulfort, K. L.; Hupp, J. T. Supercritical Processing as a Route to High Internal Surface Areas and Permanent Microporosity in Metal–Organic Framework Materials. J. Am. Chem. Soc. 2009, 131, 458– 460, DOI: 10.1021/ja808853q[ACS Full Text], [CAS], Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsFChsb3J&md5=dc9e4bf4e41d4f8d15af0510be0261aaSupercritical Processing as a Route to High Internal Surface Areas and Permanent Microporosity in Metal-Organic Framework MaterialsNelson, Andrew P.; Farha, Omar K.; Mulfort, Karen L.; Hupp, Joseph T.Journal of the American Chemical Society (2009), 131 (2), 458-460CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Careful processing of 4 representative metal-org. framework (MOF) materials with liq. and supercrit. CO2 (ScD) leads to substantial, or in some cases spectacular (up to 1200%), increases in gas-accessible surface area. Maximization of surface area is key to the optimization of MOFs for many potential applications. Preliminary evidence points to inhibition of mesopore collapse, and therefore micropore accessibility, as the basis for the extraordinarily efficacious outcome of ScD-based activation. The crystals of the MOF including naphthalenedimide-contg. ligand are P2(1)/c, with a 23.275(4), b 25.486(4), c 49.521(7) Å, β 117.409(6)°; Z = 4, dc = 0.559; R1 = 0.0692, wR2 = 0.1513.
- 45Mondloch, J. E.; Karagiaridi, O.; Farha, O. K.; Hupp, J. T. Activation of metal–organic framework materials. CrystEngComm 2013, 15, 9258– 9264, DOI: 10.1039/c3ce41232f[Crossref], [CAS], Google Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs12mu7nI&md5=ab1fc6e3417f714af99db2c82f46101eActivation of metal-organic framework materialsMondloch, Joseph E.; Karagiaridi, Olga; Farha, Omar K.; Hupp, Joseph T.CrystEngComm (2013), 15 (45), 9258-9264CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)Cryst. metal-org. frameworks (MOFs) have emerged as a highly desirable class of solid-state materials. Some of their most attractive features include exceptionally high porosities as well as surface areas. A key aspect to the realization of high porosity is the removal of guest mols. from the framework while still maintaining its structural integrity (i.e., "activation"). This contribution highlights the strategies utilized to date for activating MOFs, including: (i) conventional heating and vacuum; (ii) solvent-exchange; (iii) supercrit. CO2 (scCO2) exchange; (iv) freeze-drying; and (v) chem. treatment.
- 46Howarth, A. J.; Peters, A. W.; Vermeulen, N. A.; Wang, T. C.; Hupp, J. T.; Farha, O. K. Best Practices for the Synthesis, Activation, and Characterization of Metal–Organic Frameworks. Chem. Mater. 2017, 29, 26– 39, DOI: 10.1021/acs.chemmater.6b02626[ACS Full Text], [CAS], Google Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFait7nM&md5=d12a6d43e44dd8b441ae14bfd973c6f4Best Practices for the Synthesis, Activation, and Characterization of Metal-Organic FrameworksHowarth, Ashlee J.; Peters, Aaron W.; Vermeulen, Nicolaas A.; Wang, Timothy C.; Hupp, Joseph T.; Farha, Omar K.Chemistry of Materials (2017), 29 (1), 26-39CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)A review. Metal-org. frameworks (MOFs) are structurally diverse materials comprised of inorg. and org. components. As the rapidly expanding field of MOF research demonstrated, these materials are being explored for a wide variety of potential applications. In this tutorial review, the authors give an overview of the current best practices assocd. with the synthesis, activation and characterization of MOFs. Methods described include supercrit. CO2 activation, single crystal XRD, powder X-ray diffraction (PXRD), N adsorption/desorption isotherms, surface area calcns., aq. stability tests, SEM, inductively coupled plasma optical emission spectroscopy (ICP-OES), NMR spectroscopy (NMR), and diffuse reflectance IR Fourier transform spectroscopy (DRIFTS). A variety of different MOFs are presented to aid in the discussion of relevant techniques. Some sections are accompanied by instructional videos to give further insight into the techniques, including tips/tricks/suggestions only those at the bench could describe.
- 47Serre, C.; Millange, F.; Thouvenot, C.; Noguès, M.; Marsolier, G.; Louër, D.; Férey, G. Very Large Breathing Effect in the First Nanoporous Chromium(III)-Based Solids: MIL-53 or CrIII(OH)·{O2C–C6H4–CO2}·{HO2C–C6H4–CO2H}x·H2Oy. J. Am. Chem. Soc. 2002, 124, 13519– 13526, DOI: 10.1021/ja0276974[ACS Full Text], [CAS], Google Scholar47https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XotVegt74%253D&md5=59fd68d1cae2399f56196e58039d3bd5Very Large Breathing Effect in the First Nanoporous Chromium(III)-Based Solids: MIL-53 or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}x·H2OySerre, Christian; Millange, Franck; Thouvenot, Christelle; Nogues, Marc; Marsolier, Gerard; Loueer, Daniel; Ferey, GerardJournal of the American Chemical Society (2002), 124 (45), 13519-13526CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The 1st three-dimensional Cr(III) dicarboxylate, MIL-53as or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}0.75, was obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or CrIII(OH)·{O2C-C6H4-CO2}. At room temp., MIL-53ht adsorbs atm. H2O immediately to give CrIII(OH)·{O2C-C6H4-CO2}·H2O or MIL-53lt (lt: low-temp. form, ht:high-temp. form). Structures, which were detd. by using x-ray powder diffraction data, are built up from chains of Cr(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of 1-dimensional large pore channels filled with free disordered terephthalic mols. (MIL-53as) or H2O mols. (MIL-53lt); when the free mols. are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m2/g. The transition between the hydrated form (MIL-53lt) and the anhyd. solid (MIL-53ht) is fully reversible and followed by a very high breathing effect (more than 5 Å), the pores being clipped in the presence of H2O mols. (MIL-53lt) and reopened when the channels are empty (MIL-53ht). The thermal behavior of the two solids was studied using TGA and x-ray thermodiffractometry. The sorption properties of MIL-53lt also were studied using several org. solvents. Finally, magnetism measurements performed on MIL-53as and MIL-53lt revealed that these two phases are antiferromagnetic with Neel temps. TN of 65 and 55 K, resp. Crystal data for MIL-53as is as follows: orthorhombic space group Pnam with a 17.340(1), b 12.178(1), c 6.822(1) Å, and Z = 4. Crystal data for MIL-53ht is as follows: orthorhombic space group Imcm with a 16.733(1), b 13.038(1), c 6.812(1) Å, and Z = 4. Crystal data for MIL-53lt is as follows: monoclinic space group C2/c with a 19.685(4), b 7.849(1), c 6.782(1) Å, β 104.90(1)°, and Z = 4.
- 48Li, Q.; Zhang, W.; Miljanić, O. Š.; Sue, C.-H.; Zhao, Y.-L.; Liu, L.; Knobler, C. B.; Stoddart, J. F.; Yaghi, O. M. Docking in Metal-Organic Frameworks. Science 2009, 325, 855– 859, DOI: 10.1126/science.1175441[Crossref], [PubMed], [CAS], Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXps1Ogsb4%253D&md5=655dc9f6d1a194d49e7070570cacd2f9Docking in Metal-Organic FrameworksLi, Qiaowei; Zhang, Wenyu; Miljanic, Ognjen S.; Sue, Chi-Hau; Zhao, Yan-Li; Liu, Lihua; Knobler, Carolyn B.; Stoddart, J. Fraser; Yaghi, Omar M.Science (Washington, DC, United States) (2009), 325 (5942), 855-859CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The use of metal-org. frameworks (MOFs) so far has largely relied on nonspecific binding interactions to host small mol. guests. The authors used long org. struts (~2 nm) incorporating 34- and 36-membered macrocyclic polyethers as recognition modules in the construction of several cryst. primitive cubic frameworks that engage in specific binding in a way not obsd. in passive, open reticulated geometries. MOF-1001 is capable of docking paraquat dication (PQT2+) guests within the macrocycles in a stereoelectronically controlled fashion. This act of specific complexation yields quant. the corresponding MOF-1001 pseudorotaxanes, as confirmed by x-ray diffraction and by solid- and soln.-state NMR spectroscopic studies performed on MOF-1001, its pseudorotaxanes, and their mol. strut precursors. A control expt. involving the attempted inclusion of PQT2+ inside a framework (MOF-177) devoid of polyether struts showed negligible uptake of PQT2+, indicating the importance of the macrocyclic polyether in PQT2+ docking.
- 49Deng, H.; Olson, M. A.; Stoddart, J. F.; Yaghi, O. M. Robust Dynamics. Nat. Chem. 2010, 2, 439– 443, DOI: 10.1038/nchem.654[Crossref], [PubMed], [CAS], Google Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXmtlWlt7g%253D&md5=79cf0fcec448dd09b5fbfead8b5c0003Robust dynamicsDeng, Hexiang; Olson, Mark A.; Stoddart, J. Fraser; Yaghi, Omar M.Nature Chemistry (2010), 2 (6), 439-443CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Although metal-org. frameworks are extensive in no. and have found widespread applications, there remains a need to add complexity to their structures in a controlled manner. It is inevitable that frameworks capable of dynamics will be required. However, as in other extended structures, when they are flexible, they fail. We propose that mech. interlocked mols. be inserted covalently into the rigid framework backbone such that they are mounted as integrated components, capable of dynamics, without compromising the fidelity of the entire system. We have coined the term 'robust dynamics' to describe constructs where the repeated dynamics of one entity does not affect the integrity of any others linked to it. The implication of this concept for dynamic mols., whose performance has the disadvantages of random motion, is to bring them to a standstill in three-dimensional extended structures and thus significantly enhance their order, and ultimately their coherence and performance.
- 50Schneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A. Flexible Metal–Organic Frameworks. Chem. Soc. Rev. 2014, 43, 6062– 6096, DOI: 10.1039/C4CS00101J[Crossref], [PubMed], [CAS], Google Scholar50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Slu7nI&md5=b824d2bff6379c9662b50e86739b42f7Flexible metal-organic frameworksSchneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A.Chemical Society Reviews (2014), 43 (16), 6062-6096CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Advances in flexible and functional metal-org. frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009-2013 with ref. to the early pertinent work since the late 1990s. Flexible MOFs combine the cryst. order of the underlying coordination network with cooperative structural transformability. These materials can respond to phys. and chem. stimuli of various kinds in a tunable fashion by mol. design, which does not exist for other known solid-state materials. Among the fascinating properties are so-called breathing and swelling phenomena as a function of host-guest interactions. Phase transitions are triggered by guest adsorption/desorption, photochem., thermal, and mech. stimuli. Other important flexible properties of MOFs, such as linker rotation and sub-net sliding, which are not necessarily accompanied by crystallog. phase transitions, are briefly mentioned as well. Emphasis is given on reviewing the recent progress in application of in situ characterization techniques and the results of theor. approaches to characterize and understand the breathing mechanisms and phase transitions. The flexible MOF systems, which are discussed, are categorized by the type of metal-nodes involved and how their coordination chem. with the linker mols. controls the framework dynamics. Aspects of tailoring the flexible and responsive properties by the mixed component solid-soln. concept are included, and as well examples of possible applications of flexible metal-org. frameworks for sepn., catalysis, sensing, and biomedicine.
- 51Coudert, F.-X. Responsive Metal–Organic Frameworks and Framework Materials: Under Pressure, Taking the Heat, in the Spotlight, with Friends. Chem. Mater. 2015, 27, 1905– 1916, DOI: 10.1021/acs.chemmater.5b00046[ACS Full Text], [CAS], Google Scholar51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXisF2hurw%253D&md5=4c0a4fb50b0c9eefcfd9e1dbc3fca990Responsive Metal-Organic Frameworks and Framework Materials: Under Pressure, Taking the Heat, in the Spotlight, with FriendsCoudert, Francois-XavierChemistry of Materials (2015), 27 (6), 1905-1916CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)A review. Recent years have seen a large increase of the research effort focused on framework materials, including the nowadays-ubiquitous metal-org. frameworks but also dense coordination polymers, covalent org. frameworks, and mol. frameworks. With the quickly increasing no. of structures synthesized and characterized, one pattern emerging is the common occurrence of flexibility. More specifically, an important no. of framework materials are stimuli-responsive: their structure can undergo changes of large amplitude in response to phys. or chem. stimulation. They can display transformations induced by temp., mech. pressure, guest adsorption or evacuation, light absorption, etc. and are sometimes referred to as smart materials, soft crystals, or dynamic materials. This Perspective highlights recent progress in this field, showcasing some of the most novel and unusual responses to stimuli, as well as advances in the fundamental understanding of flexible framework materials.
- 52Martinez-Bulit, P.; Stirk, A. J.; Loeb, S. J. Rotors, Motors, and Machines Inside Metal–Organic Frameworks. Trends in Chemistry 2019, 1, 588– 600, DOI: 10.1016/j.trechm.2019.05.005
- 53Canossa, S.; Ji, Z.; Wuttke, S. Circumventing Wear and Tear of Adaptive Porous Materials. Adv. Funct. Mater. 2020, 1908547, DOI: 10.1002/adfm.201908547
- 54Rowsell, J. L. C.; Spencer, E. C.; Eckert, J.; Howard, J. A. K.; Yaghi, O. M. Gas Adsorption Sites in a Large-Pore Metal-Organic Framework. Science 2005, 309, 1350– 1354, DOI: 10.1126/science.1113247[Crossref], [PubMed], [CAS], Google Scholar54https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXovVOjt7g%253D&md5=f60c7e82ec8088459a2d844cb807f924Gas Adsorption Sites in a Large-Pore Metal-Organic FrameworkRowsell, Jesse L. C.; Spencer, Elinor C.; Eckert, Juergen; Howard, Judith A. K.; Yaghi, Omar M.Science (Washington, DC, United States) (2005), 309 (5739), 1350-1354CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The primary adsorption sites for Ar and N2 within metal-org. framework-5, a cubic structure composed of Zn4O(CO2)6 units and phenylene links defining large pores 12 and 15 angstroms in diam., have been identified by single-crystal x-ray diffraction. Refinement of data collected between 293 and 30 K revealed a total of eight symmetry-independent adsorption sites. Five of these are sites on the zinc oxide unit and the org. link; the remaining three sites form a second layer in the pores. The structural integrity and high symmetry of the framework are retained throughout, with negligible changes resulting from gas adsorption.
- 55Furukawa, H.; Gándara, F.; Zhang, Y.-B.; Jiang, J.; Queen, W. L.; Hudson, M. R.; Yaghi, O. M. Water Adsorption in Porous Metal-Organic Frameworks and Related Materials. J. Am. Chem. Soc. 2014, 136, 4369– 4381, DOI: 10.1021/ja500330a[ACS Full Text], [CAS], Google Scholar55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXjtlOltL0%253D&md5=21f85eb8745a7073aac8aa39e6923ee8Water Adsorption in Porous Metal-Organic Frameworks and Related MaterialsFurukawa, Hiroyasu; Gandara, Felipe; Zhang, Yue-Biao; Jiang, Juncong; Queen, Wendy L.; Hudson, Matthew R.; Yaghi, Omar M.Journal of the American Chemical Society (2014), 136 (11), 4369-4381CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Three criteria for achieving high performing porous materials for water adsorption have been identified. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. Water adsorption properties of 23 materials were investigated, 20 of which being metal-org. frameworks (MOFs). Among the MOFs were 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcryst. powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examd. for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)4(-CO2) secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl org. linkers to make extended porous frameworks. The permanent porosity of all 23 materials was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temp. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermol. interaction between adsorbed water mols. within the pores.
- 56Tanabe, K. K.; Wang, Z.; Cohen, S. M. Systematic Functionalization of a Metal-Organic Framework via a Postsynthetic Modification Approach. J. Am. Chem. Soc. 2008, 130, 8508– 8517, DOI: 10.1021/ja801848j[ACS Full Text], [CAS], Google Scholar56https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmvFKltrw%253D&md5=1e185fd35a2fa8f5872c195a72fba475Systematic Functionalization of a Metal-Organic Framework via a Postsynthetic Modification ApproachTanabe, Kristine K.; Wang, Zhenqiang; Cohen, Seth M.Journal of the American Chemical Society (2008), 130 (26), 8508-8517CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The pendant amino groups in isoreticular metal-org. framework-3 (IRMOF-3) were subjected to postsynthetic modification with 10 linear alkyl anhydrides [O(CO(CH2)nCH3)2] (where n = 1 to 18) and the extent of conversion, thermal and structural stability, and Brunauer-Emmett-Teller (BET) surface areas of the resulting materials were probed. 1H NMR of digested samples showed that longer alkyl chain anhydrides resulted in lower conversions of IRMOF-3 to the corresponding amide framework (designated as IRMOF-3-AM2 to IRMOF-3-AM19). Percent conversions ranged from essentially quant. (∼99%, -AM2) to ∼7% (-AM19) with IRMOF-3 samples. Modified samples were thermally stable up to approx. 430 °C and remained cryst. based on powder X-ray diffraction (PXRD) measurements. Under specific reaction conditions, significant conversions were obtained with complete retention of crystallinity, as verified by single-crystal X-ray diffraction expts. Single crystals of modified IRMOF-3 samples all showed that the F-centered cubic framework was preserved. All single crystals used for X-ray diffraction were analyzed by electrospray ionization mass spectrometry (ESI-MS) to confirm that these frameworks contained the modified 1,4-benzenedicarboxylate ligand. Single crystals of each modified IRMOF-3 were further characterized by measuring the dinitrogen gas sorption of each framework to det. the effects of modification on the porosity of the MOF. BET surface areas (m2/g) confirmed that all modified IRMOF-3 samples maintained microporosity regardless of the extent of modification. The surface area of modified MOFs was found to correlate to the size and no. of substituents added to the framework.
- 57Inokuma, Y.; Yoshioka, S.; Ariyoshi, J.; Arai, T.; Hitora, Y.; Takada, K.; Matsunaga, S.; Rissanen, K.; Fujita, M. X-ray Analysis on the Nanogram to Microgram Scale using Porous Complexes. Nature 2013, 495, 461– 466, DOI: 10.1038/nature11990[Crossref], [PubMed], [CAS], Google Scholar57https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXkslWkt7Y%253D&md5=311c16f17f42a64354c8d7e01b5685a7X-ray analysis on the nanogram to microgram scale using porous complexesInokuma, Yasuhide; Yoshioka, Shota; Ariyoshi, Junko; Arai, Tatsuhiko; Hitora, Yuki; Takada, Kentaro; Matsunaga, Shigeki; Rissanen, Kari; Fujita, MakotoNature (London, United Kingdom) (2013), 495 (7442), 461-466CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)X-ray single-crystal diffraction (SCD) anal. has the intrinsic limitation that the target mols. must be obtained as single crystals. The authors report a protocol for SCD anal. that does not require the crystn. of the sample. In the authors' method, tiny crystals of porous complexes are soaked in a soln. of the target, such that the complexes can absorb the target mols. Crystallog. anal. clearly dets. the absorbed guest structures along with the host frameworks. Because the SCD anal. is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram-microgram order. As little as ∼80 ng of a sample is enough for the SCD anal. In combination with HPLC, the authors' protocol allows the direct characterization of multiple fractions, establishing a prototypical means of liq. chromatog. SCD anal. Also, the authors unambiguously detd. the structure of a scarce marine natural product using only 5 μg of the compd.
- 58Lee, S.; Kapustin, E. A.; Yaghi, O. M. Coordinative Alignment of Molecules in Chiral Metal-Organic Frameworks. Science 2016, 353, 808– 811, DOI: 10.1126/science.aaf9135[Crossref], [PubMed], [CAS], Google Scholar58https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlCju7zP&md5=e4c3357bdcb899451669d13d60abf053Coordinative alignment of molecules in chiral metal-organic frameworksLee, Seungkyu; Kapustin, Eugene A.; Yaghi, Omar M.Science (Washington, DC, United States) (2016), 353 (6301), 808-811CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A chiral metal-org. framework, MOF-520, was used to coordinatively bind and align mols. of varying size, complexity, and functionality. The reduced motional degrees of freedom obtained with this coordinative alignment method allowed the structures of mols. to be detd. by single-crystal x-ray diffraction techniques. The chirality of the MOF backbone also served as a ref. in the structure soln. for an unambiguous assignment of the abs. configuration of bound mols. Sixteen mols. representing four common functional groups (primary alc., phenol, vicinal diol, and carboxylic acid), ranging in complexity from methanol to plant hormones (gibberellins, contg. eight stereocenters), were crystd. and had their precise structure detd. We distinguished single and double bonds in gibberellins, and we enantioselectively crystd. racemic jasmonic acid, whose abs. configuration had only been inferred from derivs.
- 59Spek, A. L. PLATON SQUEEZE: A Tool for the Calculation of the Disordered Solvent Contribution to the Calculated Structure Factors. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 9– 18, DOI: 10.1107/S2053229614024929[Crossref], [PubMed], [CAS], Google Scholar59https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjvFejtw%253D%253D&md5=88200a7c2b687d49b1dedf1a7b7fa38dPLATON SQUEEZE: a tool for the calculation of the disordered solvent contribution to the calculated structure factorsSpek, Anthony L.Acta Crystallographica, Section C: Structural Chemistry (2015), 71 (1), 9-18CODEN: ACSCGG; ISSN:2053-2296. (International Union of Crystallography)The completion of a crystal structure detn. is often hampered by the presence of embedded solvent mols. or ions that are seriously disordered. Their contribution to the calcd. structure factors in the least-squares refinement of a crystal structure has to be included in some way. Traditionally, an atomistic solvent disorder model is attempted. Such an approach is generally to be preferred, but it does not always lead to a satisfactory result and may even be impossible in cases where channels in the structure are filled with continuous electron d. This paper documents the SQUEEZE method as an alternative means of addressing the solvent disorder issue. It conveniently interfaces with the 2014 version of the least-squares refinement program SHELXL [Sheldrick (2015). Acta Cryst. C71. In the press] and other refinement programs that accept externally provided fixed contributions to the calcd. structure factors. The PLATON SQUEEZE tool calcs. the solvent contribution to the structure factors by back-Fourier transformation of the electron d. found in the solvent-accessible region of a phase-optimized difference electron-d. map. The actual least-squares structure refinement is delegated to, for example, SHELXL. The current versions of PLATON SQUEEZE and SHELXL now address several of the unnecessary complications with the earlier implementation of the SQUEEZE procedure that were a necessity because least-squares refinement with the now superseded SHELXL97 program did not allow for the input of fixed externally provided contributions to the structure-factor calcn. It is no longer necessary to subtract the solvent contribution temporarily from the obsd. intensities to be able to use SHELXL for the least-squares refinement, since that program now accepts the solvent contribution from an external file ( file) if the ABIN instruction is used. In addn., many twinned structures contg. disordered solvents are now also treatable by SQUEEZE. The details of a SQUEEZE calcn. are now automatically included in the CIF archive file, along with the unmerged reflection data. The current implementation of the SQUEEZE procedure is described, and discussed and illustrated with three examples. Two of them are based on the reflection data of published structures and one on synthetic reflection data generated for a published structure.
- 60Clegg, W. Some Reflections on Symmetry: Pitfalls of Automation and Some Illustrative Examples. Acta Cryst. E 2019, 75, 1812– 1819, DOI: 10.1107/S2056989019014907[Crossref], [CAS], Google Scholar60https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitleqtLrP&md5=bf70682693bf058b69710bcb4187eec2Some reflections on symmetry: pitfalls of automation and some illustrative examplesClegg, WilliamActa Crystallographica, Section E: Crystallographic Communications (2019), 75 (12), 1812-1819CODEN: ACSECI; ISSN:2056-9890. (International Union of Crystallography)In the context of increasing hardware and software automation in the process of crystal structure detn. by X-ray diffraction, and based on conference sessions presenting some of the experience of senior crystallographers for the benefit of younger colleagues, an outline is given here of some basic concepts and applications of symmetry in crystallog. Three specific examples of structure detns. are discussed, for which an understanding of these aspects of symmetry avoids mistakes that can readily be made by reliance on automatic procedures. Topics addressed include pseudo-symmetry, twinning, real and apparent disorder, chirality, and structure validation.
- 61Spek, A. CheckCIF Validation ALERTS: What They Mean and How to Respond. Acta Cryst. E 2020, 76, 1– 11, DOI: 10.1107/S2056989019016244[Crossref], [PubMed], [CAS], Google Scholar61https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXkvFaisg%253D%253D&md5=8abe01336ac08b0deb698bbb01835186checkCIF validation ALERTS: what they mean and how to respondSpek, Anthony L.Acta Crystallographica, Section E: Crystallographic Communications (2020), 76 (1), 1-11CODEN: ACSECI; ISSN:2056-9890. (International Union of Crystallography)A review. Authors of a paper that includes a new crystal-structure detn. are expected to not only report the structural results of interest and their interpretation, but are also expected to archive in computer-readable CIF format the exptl. data on which the crystal-structure anal. is based. Addnl., an IUCr/checkCIF validation report will be required for the review of a submitted paper. Such a validation report, automatically created from the deposited CIF file, lists as ALERTS not only potential errors or unusual findings, but also suggestions for improvement along with interesting information on the structure at hand. Major ALERTS for issues are expected to have been acted on already before the submission for publication or discussed in the assocd. paper and/or commented on in the CIF file. In addn., referees, readers and users of the data should be able to make their own judgment and interpretation of the underlying exptl. data or perform their own calcns. with the archived data. All the above is consistent with the FAIR (findable, accessible, interoperable, and reusable) initiative [Helliwell (2019). Struct. Dyn.6, 05430]. Validation can also be helpful for less experienced authors in pointing to and avoiding of crystal-structure detn. and interpretation pitfalls. The IUCr web-based checkCIF server provides such a validation report, based on data uploaded in CIF format. Alternatively, a locally installable checkCIF version is available to be used iteratively during the structure-detn. process. ALERTS come mostly as short single-line messages. There is also a short explanation of the ALERTS available through the IUCr web server or with the locally installed PLATON/checkCIF version. This paper provides addnl. background information on the checkCIF procedure and addnl. details for a no. of ALERTS along with options for how to act on them.
- 62Linden, A. Obtaining the Best Results: Aspects of Data Collection, Model Finalization and Interpretation of Results in Small-molecule Crystal-structure Determination. Acta Cryst. E 2020, 76, 765– 775, DOI: 10.1107/S2056989020005368[Crossref], [CAS], Google Scholar62https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtV2rsL3K&md5=8e916b681d9eb4a3583c4c06cfeeb0f9Obtaining the best results: aspects of data collection, model finalization and interpretation of results in small-molecule crystal-structure determinationLinden, AnthonyActa Crystallographica, Section E: Crystallographic Communications (2020), 76 (6), 765-775CODEN: ACSECI; ISSN:2056-9890. (International Union of Crystallography)In small-mol. single-crystal structure detn., we now have at our disposal an inspiring range of fantastic diffractometers with better, brighter sources, and faster, more sensitive detectors. Faster and more powerful computers provide integrated tools and software with impressive graphical user interfaces. Yet these tools can lead to the temptation not to check the work thoroughly and one can too easily overlook tell-tale signs that something might be amiss in a structure detn.; validation with checkCIF is not always revealing. This article aims to encourage practitioners, young and seasoned, by enhancing their structure-detn. toolboxes with a selection of tips and tricks on recognizing and handling aspects that one should constantly be aware of. Topics include a pitfall when setting up data collections, the usefulness of reciprocal lattice layer images, processing twinned data, tips for disorder modeling and the use of restraints, ensuring hydrogen atoms are added to a model correctly, validation beyond checkCIF, and the derivation and interpretation of the final results.
- 63Giacovazzo, C. Phasing in Crystallography: A Modern Perspective; Oxford University Press: Oxford, 2014.Google ScholarThere is no corresponding record for this reference.
- 64Gándara, F.; Bennett, T. D. Crystallography of Metal-Organic Frameworks. IUCrJ 2014, 1, 563– 570, DOI: 10.1107/S2052252514020351[Crossref], [PubMed], [CAS], Google Scholar64https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhvVyju77P&md5=503c253bbfffb1855582556c662913deCrystallography of metal-organic frameworksGandara, Felipe; Bennett, Thomas D.IUCrJ (2014), 1 (6), 563-570CODEN: IUCRAJ; ISSN:2052-2525. (International Union of Crystallography)Metal-org. frameworks (MOFs) are one of the most intensely studied material types in recent times. Their networks, resulting from the formation of strong bonds between inorg. and org. building units, offer unparalleled chem. diversity and pore environments of growing complexity. Therefore, advances in single-crystal X-ray diffraction equipment and techniques are required to characterize materials with increasingly larger surface areas, and more complex linkers. In addn., while structure soln. from powder diffraction data is possible, the area is much less populated and we detail the current efforts going on here. We also review the growing no. of reports on diffraction under non-ambient conditions, including the response of MOF structures to very high pressures. Such expts. are important due to the expected presence of stresses in proposed applications of MOFs - evidence suggesting rich and complex behavior. Given the entwined and inseparable nature of their structure, properties and applications, it is essential that the field of structural elucidation is able to continue growing and advancing, so as not to provide a rate-limiting step on characterization of their properties and incorporation into devices and applications. This review has been prepd. with this in mind.
- 65Gándara, F.; Furukawa, H.; Lee, S.; Yaghi, O. M. High Methane Storage Capacity in Aluminum Metal–Organic Frameworks. J. Am. Chem. Soc. 2014, 136, 5271– 5274, DOI: 10.1021/ja501606h[ACS Full Text], [CAS], Google Scholar65https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXkslamt7w%253D&md5=f45850d29d222bb32621c184ec84ca01High Methane Storage Capacity in Aluminum Metal-Organic FrameworksGandara, Felipe; Furukawa, Hiroyasu; Lee, Seungkyu; Yaghi, Omar M.Journal of the American Chemical Society (2014), 136 (14), 5271-5274CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The use of porous materials to store natural gas in vehicles requires large amts. of methane per unit of vol. Here the authors report the synthesis, crystal structure and methane adsorption properties of two new aluminum metal-org. frameworks, MOF-519 and MOF-520. Both materials exhibit permanent porosity and high methane volumetric storage capacity: MOF-519 has a volumetric capacity of 200 and 279 cm3 cm-3 at 298 K and 35 and 80 bar, resp., and MOF-520 has a volumetric capacity of 162 and 231 cm3 cm-3 under the same conditions. Also, MOF-519 exhibits an exceptional working capacity, being able to deliver a large amt. of methane at pressures between 5 and 35 bar, 151 cm3 cm-3, and between 5 and 80 bar, 230 cm3 cm-3.
- 66Zhao, Y.; Guo, L.; Gándara, F.; Ma, Y.; Liu, Z.; Zhu, C.; Lyu, H.; Trickett, C. A.; Kapustin, E. A.; Terasaki, O.; Yaghi, O. M. A Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic Frameworks. J. Am. Chem. Soc. 2017, 139, 13166– 13172, DOI: 10.1021/jacs.7b07457[ACS Full Text], [CAS], Google Scholar66https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtl2lsb7J&md5=21ff2b0cba138d5bbfb342b4cae51a3bA Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic FrameworksZhao, Yingbo; Guo, Lei; Gandara, Felipe; Ma, Yanhang; Liu, Zheng; Zhu, Chenhui; Lyu, Hao; Trickett, Christopher A.; Kapustin, Eugene A.; Terasaki, Osamu; Yaghi, Omar M.Journal of the American Chemical Society (2017), 139 (37), 13166-13172CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Developing synthetic methodol. to crystallize extended covalent structures was an important pursuit of reticular chem. Here, we report a homogeneous synthetic route for imine covalent org. frameworks (COFs) where crystallites emerge from clear solns. without forming amorphous polyimine ppts. The key feature of this route is the utilization of tert-butyloxycarbonyl group protected amine building blocks, which are deprotected in situ and gradually nucleate the cryst. framework. We demonstrate the utility of this approach by crystg. a woven covalent org. framework (COF-112), in which covalent org. threads are interlaced to form a three-dimensional woven framework. The homogeneous imine COF synthesis also enabled the control of nucleation and crystal growth leading to uniform nanocrystals, through microwave-assisted reactions, and facile prepn. of oriented thin films.
- 67Ma, T.; Kapustin, E. A.; Yin, S. X.; Liang, L.; Zhou, Z.; Niu, J.; Li, L.-H.; Wang, Y.; Su, J.; Li, J.; Wang, X.; Wang, W. D.; Wang, W.; Sun, J.; Yaghi, O. M. Single-Crystal X-ray Diffraction Structures of Covalent Organic Frameworks. Science 2018, 361, 48– 52, DOI: 10.1126/science.aat7679[Crossref], [PubMed], [CAS], Google Scholar67https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXht1Cjs7zM&md5=9c25f3d95459d93a6affbfb36fef477cSingle-crystal x-ray diffraction structures of covalent organic frameworksMa, Tianqiong; Kapustin, Eugene A.; Yin, Shawn X.; Liang, Lin; Zhou, Zhengyang; Niu, Jing; Li, Li-Hua; Wang, Yingying; Su, Jie; Li, Jian; Wang, Xiaoge; Wang, Wei David; Wang, Wei; Sun, Junliang; Yaghi, Omar M.Science (Washington, DC, United States) (2018), 361 (6397), 48-52CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. The crystn. problem is an outstanding challenge in the chem. of porous covalent org. frameworks (COFs). Their structural characterization was limited to modeling and solns. based on powder x-ray or electron diffraction data. Single crystals of COFs amenable to x-ray diffraction characterization were not reported. A general procedure was developed to grow large single crystals of 3-dimensional imine-based COFs (COF-300, hydrated form of COF-300, COF-303, LZU-79, and LZU-111). The high quality of the crystals allowed collection of single-crystal x-ray diffraction data of up to 0.83-Å resoln., leading to unambiguous soln. and precise anisotropic refinement. Characteristics such as degree of interpenetration, arrangement of H2O guests, the reversed imine connectivity, linker disorder, and uncommon topol. were deciphered with at. precision-aspects impossible to det. without single crystals.
- 68Zhang, D.; Oleynikov, P.; Hovmöller, S.; Zou, X. Collecting 3D Electron Diffraction Data by the Rotation Method. Z. Kristallogr. 2010, 225, 94– 102, DOI: 10.1524/zkri.2010.1202[Crossref], [CAS], Google Scholar68https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXltFWqsLg%253D&md5=aeb9f3488219a0b20ffdac02582387e4Collecting 3D electron diffraction data by the rotation methodZhang, Daliang; Oleynikov, Peter; Hovmoeller, Sven; Zou, XiaodongZeitschrift fuer Kristallographie - Crystalline Materials (2010), 225 (2-3), 94-102CODEN: ZKCMAJ; ISSN:2194-4946. (Oldenbourg Wissenschaftsverlag GmbH)A new method for collecting complete 3-dimensional electron diffraction data is described. Diffraction data is collected by combining electron beam tilt at many very small steps, with rotation of the crystal in a few but large steps. A no. of practical considerations are discussed, as well as advantages and disadvantages compared to other methods of collecting electron diffraction data.
- 69Zhang, Y.-B.; Su, J.; Furukawa, H.; Yun, Y.; Gándara, F.; Duong, A.; Zou, X.; Yaghi, O. M. Single-Crystal Structure of a Covalent Organic Framework. J. Am. Chem. Soc. 2013, 135, 16336– 16339, DOI: 10.1021/ja409033p[ACS Full Text], [CAS], Google Scholar69https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs1Cktr3N&md5=ea22e0f58fcdda105e732e4fede57bc5Single-Crystal Structure of a Covalent Organic FrameworkZhang, Yue-Biao; Su, Jie; Furukawa, Hiroyasu; Yun, Yifeng; Gandara, Felipe; Duong, Adam; Zou, Xiaodong; Yaghi, Omar M.Journal of the American Chemical Society (2013), 135 (44), 16336-16339CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The crystal structure of a new covalent org. framework, termed COF-320, is detd. by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepd. by an imine condensation of tetra-(4-anilyl)-methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 °C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m2/g and a methane total uptake of 15.0 wt. % (176 cm3/cm3) at 25 °C and 80 bar. The successful detn. of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chem.
- 70Diercks, C. S.; Yaghi, O. M. The Atom, the Molecule, and the Covalent Organic Framework. Science 2017, 355, eaal1585, DOI: 10.1126/science.aal1585
- 71Le Bail, A. Whole Powder Pattern Decomposition Methods and Applications: A Retrospection. Powder Diffr. 2005, 20, 316– 326, DOI: 10.1154/1.2135315[Crossref], [CAS], Google Scholar71https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht12lsb%252FN&md5=1903ec1ca6e2afd307973c930bd9e365Whole powder pattern decomposition methods and applications: A retrospectionLe Bail, ArmelPowder Diffraction (2005), 20 (4), 316-326CODEN: PODIE2; ISSN:0885-7156. (American Institute of Physics)A review is given on methods extg. fast all the peak intensities from a complete powder diffraction pattern. The genesis of the modern whole powder pattern decompn. methods (the so-called Pawley and Le Bail methods) is detailed and their importance and domains of application are decoded from the most cited papers citing them. These methods represented a decisive step toward the possibility to solve more easily, if not routinely, a structure solely from a powder sample. The contributions from the Louer's group during the rising years 1987-1993 are stressed.
- 72Rietveld, H. M. A Profile Refinement Method for Nuclear and Magnetic Structures. J. Appl. Crystallogr. 1969, 2, 65– 71, DOI: 10.1107/S0021889869006558[Crossref], [CAS], Google Scholar72https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1MXksVeisbk%253D&md5=3e3acdf00920ecd78a9bc042511e7fc4Profile refinement method for nuclear and magnetic structuresRietveld, H. M.Journal of Applied Crystallography (1969), 2 (Pt. 2), 65-71CODEN: JACGAR; ISSN:0021-8898.A structural refinement method for neutron diffraction is presented which makes direct use of the profile intensities obtained from the powder diagram. It is applicable to nuclear structures and to magnetic structures which can be described on the nuclear unit cell or a multiple thereof. Equations for the measured profiles to be used in the least sqs. treatment are cor. for asymmetry and preferred orientation; the angular dependence of the half widths of the peaks is given by the formula of Caglioti, et al. (1958). The magnetic contribution to the profile equation is expressed by calcg. only one av. cross section for each set of equiv. reflections. It is possible to introduce constraint functions, linear or quadratic, between parameters used in the least sqs. treatment. Results of the use of this method are given for a series of compds. In all instances it has proved superior to any other method involving integrated neutron powder intensities, single or overlapping.
- 73Ockwig, N. W.; Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Reticular Chemistry: Occurrence and Taxonomy of Nets and Grammar for the Design of Frameworks. Acc. Chem. Res. 2005, 38, 176– 182, DOI: 10.1021/ar020022l[ACS Full Text], [CAS], Google Scholar73https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXksFSgsg%253D%253D&md5=13530d98a4733672738db281372887aeReticular Chemistry: Occurrence and Taxonomy of Nets and Grammar for the Design of FrameworksOckwig, Nathan W.; Delgado-Friedrichs, Olaf; O'Keeffe, Michael; Yaghi, Omar M.Accounts of Chemical Research (2005), 38 (3), 176-182CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)The structures of all 1127 three-periodic extended metal-org. frameworks (MOFs) reported in the Cambridge Structure Database were analyzed, and their underlying topol. was detd. It is remarkable that among the almost infinite no. of net topologies that are available for MOFs to adopt, only a handful of nets are actually obsd. The discovery of this inversion between expected and obsd. nets led the authors to deduce a system of classification taxonomy for interpreting and rationalizing known MOF structures, as well as those that will be made in future. The origin of this inversion is attributed to the different modes with which MOF synthesis was approached. Specifically, three levels of complexity are defined that embody rules grammar for the design of MOFs and other extended structures. This system accounts for the present proliferation of MOF structures of high symmetry nets, but more importantly, it provides the basis for designing a building block that codes for a specific structure and, indeed, only that structure.
- 74RCSR, http://rcsr.net, accessed April 25, 2020.Google ScholarThere is no corresponding record for this reference.
- 75Suga, M.; Asahina, S.; Sakuda, Y.; Kazumori, H.; Nishiyama, H.; Nokuo, T.; Alfredsson, V.; Kjellman, T.; Stevens, S. M.; Cho, H. S.; Cho, M.; Han, L.; Che, S.; Anderson, M. W.; Schüth, F.; Deng, H.; Yaghi, O. M.; Liu, Z.; Jeong, H. Y.; Stein, A.; Sakamoto, K.; Ryoo, R.; Terasaki, O. Recent Progress in Scanning Electron Microscopy for the Characterization of Fine Structural Details of Nano Materials. Prog. Solid State Chem. 2014, 42, 1– 2, DOI: 10.1016/j.progsolidstchem.2014.02.001[Crossref], [CAS], Google Scholar75https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXks12ksLY%253D&md5=eba822410773b2f229ccb1c468add1d2Recent progress in scanning electron microscopy for the characterization of fine structural details of nano materialsSuga, Mitsuo; Asahina, Shunsuke; Sakuda, Yusuke; Kazumori, Hiroyoshi; Nishiyama, Hidetoshi; Nokuo, Takeshi; Alfredsson, Viveka; Kjellman, Tomas; Stevens, Sam M.; Cho, Hae Sung; Cho, Minhyung; Han, Lu; Che, Shunai; Anderson, Michael W.; Schuth, Ferdi; Deng, Hexiang; Yaghi, Omar M.; Liu, Zheng; Jeong, Hu Young; Stein, Andreas; Sakamoto, Kazuyuki; Ryoo, Ryong; Terasaki, OsamuProgress in Solid State Chemistry (2014), 42 (1-2), 1-21CODEN: PSSTAW; ISSN:0079-6786. (Elsevier Ltd.)A review. Research concerning nanomaterials (metal-org. frameworks (MOFs), zeolites, mesoporous silicas, etc.) and the nano-scale, including potential barriers for the particulates to diffusion to/from is of increasing importance to the understanding of the catalytic utility of porous materials when combined with any potential superstructures (such as hierarchically porous materials). However, it is difficult to characterize the structure of for example MOFs via x-ray powder diffraction because of the serious overlapping of reflections caused by their large unit cells, and it is also difficult to directly observe the opening of surface pores using ordinary methods. Electron-microscopic methods including high-resoln. SEM (HRSEM) have therefore become imperative for the above challenges. Presented is the theory and practical application of recent advances such as through-the-lens detection systems, which permit a reduced landing energy and the selection of high-resoln., topog. specific emitted electrons, even from elec. insulating nanomaterials.
- 76Hillman, F.; Zimmerman, J. M.; Paek, S.-M.; Hamid, M. R. A.; Lim, W. T.; Jeong, H.-K. Rapid Microwave-Assisted Synthesis of Hybrid Zeolitic–Imidazolate Frameworks with Mixed Metals and Mixed Linkers. J. Mater. Chem. A 2017, 5, 6090– 6099, DOI: 10.1039/C6TA11170J[Crossref], [CAS], Google Scholar76https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjsFGltrk%253D&md5=50e2dbc3c2863e9f52c46c6562c9b041Rapid microwave-assisted synthesis of hybrid zeolitic-imidazolate frameworks with mixed metals and mixed linkersHillman, Febrian; Zimmerman, John M.; Paek, Seung-Min; Hamid, Mohamad R. A.; Lim, Woo Taik; Jeong, Hae-KwonJournal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (13), 6090-6099CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)Herein the authors report a new microwave-assisted synthetic strategy to rapidly prep. hybrid zeolitic-imidazolate frameworks (ZIFs): ZIFs with mixed metal centers and/or mixed linkers. The microwave-based method significantly shortens synthesis time, produces a higher yield, substantially reduces the amts. of ligands, and eliminates the use of deprotonating agents. The x-ray diffraction pattern reveals that mixed metal CoZn-ZIF-8 (i.e., ZIF-8 with both Co and Zn centers) maintains the sodalite (SOD) zeolitic topol. from the ZIF-8 parent. Elemental mapping using energy-dispersive x-ray spectroscopy (EDS) and electronic/geometric information obtained from X-ray absorption spectroscopy (XAS) confirm the uniform distribution of tetrahedral Co and Zn metal centers within the same framework of the mixed-metal ZIF. The metal to nitrogen (M-N) stretching frequencies of IR bands are systematically blue-shifted as the Co/Zn ratio in the mixed metal ZIF increases. Also, for the 1st time, a hybrid ZIF with both mixed metal centers (Co and Zn) and mixed linkers (2-methylimidazolate and benzimidazolate) was prepd. through 1-step microwave synthesis. Finally, mixed metal CoZn-ZIF-8 with a Co/Zn ratio of ∼1 was grown as membranes on porous α-Al2O3 supports, showing a higher propylene/propane sepn. factor (∼120) when compared to pure Zn-ZIF-8 membranes (∼63) prepd. by a similar method.
- 77Wiktor, C.; Meledina, M.; Turner, S.; Lebedev, O. I.; Fischer, R. A. Transmission Electron Microscopy on Metal–Organic Frameworks – a Review. J. Mater. Chem. A 2017, 5, 14969– 14989, DOI: 10.1039/C7TA00194K[Crossref], [CAS], Google Scholar77https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXptlSnsLw%253D&md5=7ffb273660f9ff35f370b7baf4917d3aTransmission electron microscopy on metal-organic frameworks - a reviewWiktor, Christian; Meledina, Maria; Turner, Stuart; Lebedev, Oleg I.; Fischer, Roland A.Journal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (29), 14969-14989CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)Versatile materials like metal-org. frameworks require careful characterization. Transmission electron microscopy is a very powerful method that can address a multitude of investigative challenges. In this review we present TEM studies that yielded valuable insights into the investigated MOFs to illustrate the potential of TEM despite the sensitivity of MOFs to the electron beam.
- 78Greer, H.; Zhou, W. Electron diffraction and HRTEM imaging of beam-sensitive materials. Crystallogr. Rev. 2011, 17, 163– 185, DOI: 10.1080/0889311X.2010.535525[Crossref], [CAS], Google Scholar78https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXovFyrsr4%253D&md5=1a41c2561981ad0a8e0f0f3096e1d793Electron diffraction and HRTEM imaging of beam-sensitive materialsGreer, Heather F.; Zhou, WuzongCrystallography Reviews (2011), 17 (3), 163-185CODEN: CRRVEN; ISSN:0889-311X. (Taylor & Francis Ltd.)A review. The high-resoln. transmission electron microscopic investigation of electron beam-sensitive materials is a challenging research field. Applying a low-temp. specimen holder can reduce the sample damage rate. However, both the specimen holder and the running costs are expensive. Alternatively, it has been found that some treatments are helpful to overcome the beam damage problem of operating transmission electron microscope at room temp. In this article, we review some typical examples of electron diffraction and high-resoln. transmission electron microscopic imaging of beam-sensitive specimens carried out at St Andrews University and in other institutions. The samples in question include C60/trimethylbenzene nanowires, zeolites, metal org. frameworks, etc. These developed techniques can certainly be used for many other beam-sensitive materials.
- 79Zhu, L.; Zhang, D.; Xue, M.; Li, H.; Qiu, S. Direct observations of the MOF (UiO-66) structure by transmission electron microscopy. CrystEngComm 2013, 15, 9356– 9359, DOI: 10.1039/c3ce41122b[Crossref], [CAS], Google Scholar79https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs12mu7jP&md5=7a3f891faf31f4bdbf6ed269a577aa28Direct observations of the MOF (UiO-66) structure by transmission electron microscopyZhu, Liangkui; Zhang, Daliang; Xue, Ming; Li, Huan; Qiu, ShilunCrystEngComm (2013), 15 (45), 9356-9359CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)As a demonstration of ab initio structure characterizations of nano metal org. framework (MOF) crystals by high resoln. TEM (HRTEM) and electron diffraction tomog. methods, a Zr-MOF (UiO-66) structure was detd. and further confirmed by Rietveld refinements of powder x-ray diffraction. HRTEM gave direct imaging of the channels.
- 80Deng, H.; Grunder, S.; Cordova, K. E.; Valente, C.; Furukawa, H.; Hmadeh, M.; Gándara, F.; Whalley, A. C.; Liu, Z.; Asahina, S.; Kazumori, H.; O’Keeffe, M.; Terasaki, O.; Stoddart, J. F.; Yaghi, O. M. Large-Pore Apertures in a Series of Metal-Organic Frameworks. Science 2012, 336, 1018– 1023, DOI: 10.1126/science.1220131[Crossref], [PubMed], [CAS], Google Scholar80https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xnt1Kgt7s%253D&md5=be82c139a536be7009991c48606c3829Large-Pore Apertures in a Series of Metal-Organic FrameworksDeng, Hexiang; Grunder, Sergio; Cordova, Kyle E.; Valente, Cory; Furukawa, Hiroyasu; Hmadeh, Mohamad; Gandara, Felipe; Whalley, Adam C.; Liu, Zheng; Asahina, Shunsuke; Kazumori, Hiroyoshi; O'Keeffe, Michael; Terasaki, Osamu; Stoddart, J. Fraser; Yaghi, Omar M.Science (Washington, DC, United States) (2012), 336 (6084), 1018-1023CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The authors report a strategy to expand the pore aperture of metal-org. frameworks (MOFs) into a previously unattained size regime (>32 Å). Specifically, the systematic expansion of a known MOF structure, MOF-74, from its original link of one phenylene ring (I) to two, three, four, five, six, seven, nine, and eleven (II to XI, resp.), afforded an isoreticular series of Mg- or Zn-contg. MOF-74 structures (termed IRMOF-74-I to -XI) with pore apertures ranging from 14 to 98 Å. All members of this series have noninterpenetrating structures and exhibit robust architectures, as evidenced by their permanent porosity and high thermal stability (up to 300°). The pore apertures of an oligoethylene glycol-functionalized IRMOF-74-VII and IRMOF-74-IX are large enough for natural proteins to enter the pores.
- 81Düren, T.; Millange, F.; Férey, G.; Walton, K. S.; Snurr, R. Q. Calculating Geometric Surface Areas as a Characterization Tool for Metal–Organic Frameworks. J. Phys. Chem. C 2007, 111, 15350– 15356, DOI: 10.1021/jp074723h[ACS Full Text], [CAS], Google Scholar81https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtFShtLjP&md5=47226155a5817ef357a9b6f941883ee6Calculating Geometric Surface Areas as a Characterization Tool for Metal-Organic FrameworksDueren, Tina; Millange, Franck; Ferey, Gerard; Walton, Krista S.; Snurr, Randall Q.Journal of Physical Chemistry C (2007), 111 (42), 15350-15356CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Metal-org. frameworks (MOFs) synthesized in a building-block approach from org. linkers and metal corner units offer the opportunity to design materials with high surface areas for adsorption applications by assembling the appropriate building blocks. In this paper, we show that the surface area calcd. in a geometric fashion from the crystal structure is a useful tool for characterizing MOFs. We argue that the accessible surface area rather than the widely used Connolly surface area is the appropriate surface area to characterize cryst. solids for adsorption applications. The accessible surface area calcd. with a probe diam. corresponding to the adsorbate of interest provides a simple way to screen and compare adsorbents. We investigate the effects of the probe mol. diam. on the accessible surface area and discuss the implications for increasing the surface area of metal-org. frameworks by the use of catenated structures. We also demonstrate that the accessible surface area provides a useful tool for judging the quality of a synthesized sample. Exptl. surface areas can be adversely affected by incomplete solvent removal during activation, crystal collapse, or interpenetration. The easily calcd. accessible surface area provides a benchmark for the theor. upper limit for a perfect crystal.
- 82Gomez-Gualdron, D. A.; Moghadam, P. Z.; Hupp, J. T.; Farha, O. K.; Snurr, R. Q. Application of Consistency Criteria To Calculate BET Areas of Micro- And Mesoporous Metal–Organic Frameworks. J. Am. Chem. Soc. 2016, 138, 215– 224, DOI: 10.1021/jacs.5b10266[ACS Full Text], [CAS], Google Scholar82https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVShtb7F&md5=79cdc7a253075410863d233069c7c729Application of Consistency Criteria To Calculate BET Areas of Micro- And Mesoporous Metal-Organic FrameworksGomez-Gualdron, Diego A.; Moghadam, Peyman Z.; Hupp, Joseph T.; Farha, Omar K.; Snurr, Randall Q.Journal of the American Chemical Society (2016), 138 (1), 215-224CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The Brunauer, Emmett, and Teller (BET) surface areas have been calcd. for graphene and 25 MOFs having different pore-size distributions. BET areas were compared with their corresponding geometrically calcd., nitrogen-accessible surface areas (NASAs). Anal. of simulation snapshots elucidated the contributions of "pore-filling" and "monolayer-formation" to the nitrogen adsorption loadings in different MOF pores, revealing the origin of inaccuracies in BET-calcd. monolayer loadings, which largely explain discrepancies between BET areas and NASAs. Even if all consistency criteria were satisfied, the BET calcn. could significantly overestimate the true monolayer loading, esp. in MOFs combining mesopores (d ≥ 20 Å) and large micropores (d = 10-20 Å), due to the overlap of pore-filling and monolayer-formation regimes of these two kinds of pores. While it was not always possible to satisfy all consistency criteria, it was crit. to minimize the deviation from these criteria during BET range selection to consistently compare BET areas of different MOFs and for comparing simulated and exptl. BET areas of a given MOF. To accurately assess the quality of a MOF sample, it is best to compare exptl. BET areas with simulated BET areas rather than with calcd. NASAs.
- 83Möllmer, J.; Celer, E. B.; Luebke, R.; Cairns, A. J.; Staudt, R.; Eddaoudi, M.; Thommes, M. Insights on Adsorption Characterization of Metal-Organic Frameworks: A Benchmark Study on the Novel soc-MOF. Microporous Mesoporous Mater. 2010, 129, 345– 353, DOI: 10.1016/j.micromeso.2009.06.014
- 84Virmani, E.; Beyer, O.; Luning, U.; Ruschewitz, U.; Wuttke, S. Topology-guided functional multiplicity of iron(III)-based metal–organic frameworks. Mater. Chem. Front. 2017, 1, 1965– 1974, DOI: 10.1039/C7QM00263G[Crossref], [CAS], Google Scholar84https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1elsbrK&md5=1428073f00e80e4f1dc4bdf318c68a89Topology-guided functional multiplicity of iron(III)-based metal-organic frameworksVirmani, Erika; Beyer, Ole; Luening, Ulrich; Ruschewitz, Uwe; Wuttke, StefanMaterials Chemistry Frontiers (2017), 1 (10), 1965-1974CODEN: MCFAC5; ISSN:2052-1537. (Royal Society of Chemistry)We report here the synthesis and characterization of a new series of mixed-linker iron(III)-based metal-org. frameworks (MOFs) consisting of dicarboxylate linkers (1,4-benzenedicarboxylic acid ≃ BDC or its amino functionalized deriv.) and tricarboxylate linkers (4,4',4''-[1,3,5-triazine-2,4,6-triyl]tribenzoic acid ≃ TATB or its nitro functionalized deriv.). The resulting mesoporous MOFs with MIL-143 topol. are stable under ambient water conditions for 14 d regardless of the functionalization of the org. linkers. Powder X-ray diffraction results reveal high crystallinity of the materials. This structure type is very tolerant to variation in the functional groups (e.g. nitro and/or amino) along the BDC and/or TATB linkers, but is less tolerant to changes in the size of the linkers themselves. It was attempted to replace linear BDC by biphenyl-4,4'-dicarboxylic acid (BPDC) and trigonal TATB by 2,4-bis(4'-carboxy-biphenyl-4-yl)-6-(4'-carboxy-2-methoxy-biphenyl-4-yl)-1,3,5-triazine (TAPB). Of the three addnl. structures made possible by combinations of these linkers (BDC/TAPB, BPDC/TATB, BPDC/TAPB), only one (BDC/TAPB) yields a cryst. product which, like the BDC/TATB crystal, exhibits MIL-143 topol. However, this material is not very stable and collapses upon guest removal. Our results suggest that the incorporation of diverse functional groups on linkers with different geometries in this new iron(III)-based MOF series offers a simple method of precisely tuning the chem. environment within the pores. More importantly, our work expands the scope of mixed-linker MOFs to include a subset of multivariate MOFs characterized by different functionalities in each type of linker.
- 85Lippke, J.; Brosent, B.; von Zons, T.; Virmani, E.; Lilienthal, S.; Preuße, T.; Hulsmann, M.; Schneider, A. M.; Wuttke, S.; Behrens, P.; Godt, A. Expanding the Group of Porous Interpenetrated Zr-Organic Frameworks (PIZOFs) with Linkers of Different Lengths. Inorg. Chem. 2017, 56, 748– 761, DOI: 10.1021/acs.inorgchem.6b01814[ACS Full Text], [CAS], Google Scholar85https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFKlu7jF&md5=98a5bb266c0fad9b47063f121ee8e6e2Expanding the Group of Porous Interpenetrated Zr-Organic Frameworks (PIZOFs) with Linkers of Different LengthsLippke, Jann; Brosent, Birte; von Zons, Tobias; Virmani, Erika; Lilienthal, Sebastian; Preusse, Thomas; Huelsmann, Miriam; Schneider, Andreas M.; Wuttke, Stefan; Behrens, Peter; Godt, AdelheidInorganic Chemistry (2017), 56 (2), 748-761CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)A Zr-based MOF of the PIZOF type, which consists of two independent and each other interpenetrating UiO-type frameworks with [Zr6O4(OH)4(O2C)12] nodes, does not only form with a PEPEP dicarboxylic acid (P = phenylene, E = ethynylene). Also dicarboxylic acids with the shorter PPPP and PEPP spacers gave PIZOFs, denoted PPPP-PIZOF and PEPP-PIZOF. Reducing the spacer length even further to a PEEP segment caused the switchover to the formation of a UiO. The hysteresis in the Ar sorption curve of PEPP-PIZOF-1 and the slightly too large amt. of combustion residue from PPPP-PIZOF-1 suggest structural defects. These hint to a mismatch of the requirement on the optimal linker length for PIZOF formation and the lengths of the PEPP and PPPP dicarboxylates. Nevertheless, these dicarboxylates prefer the formation of a PIZOF over the formation of a UiO structure. PEPEP-PIZOF-2, PPPP-PIZOF-1 and PEPP-PIZOF-1 are stable in air up to 325°, 350°, and 300°, resp., and have BET surface areas of 2350 m2g-1, 2020 m2g-1 and 1650 m2g-1, resp. PEPEP-PIZOFs, even those with very hydrophilic oligo(ethylene glycol) side chains at the linkers, are very stable in water and also during drying from a water-wetted state. Contrary, PEPP-PIZOF-1 and PPPP-PIZOF-1, that had been exposed to water, required exchange of water for ethanol before drying to mostly preserve the framework. The results emphasize the importance to differentiate framework damage caused through hydrolysis in water and through drying from a water-wetted state. The sensitivity of PEPP-PIZOF-1 and PPPP-PIZOF-1 against drying from a water-wetted state may be the consequence of defects. The drying stability of water-wetted PEPEP-PIZOFs lets the authors suggest that reversible bending of the linkers contributes to the stability of the PEPEP-PIZOFs.
- 86Hintz, H.; Wuttke, S. Solvent-Free and Time Efficient Postsynthetic Modification of Amino-Tagged Metal–Organic Frameworks with Carboxylic Acid Derivatives. Chem. Mater. 2014, 26, 6722– 6728, DOI: 10.1021/cm502920f[ACS Full Text], [CAS], Google Scholar86https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhvFaqu7rM&md5=4106e90862dd9a7f7ccf68ce482a445fSolvent-Free and Time Efficient Postsynthetic Modification of Amino-Tagged Metal-Organic Frameworks with Carboxylic Acid DerivativesHintz, Henrik; Wuttke, StefanChemistry of Materials (2014), 26 (23), 6722-6728CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)A fast, simple, and effective approach for postsynthetic modification (PSM) of amino-tagged metal-org. frameworks (MOFs) with carboxylic acids, acid anhydrides, and acid chlorides without addnl. solvent at elevated temp. was developed. In a comparative study optimal synthesis conditions for PSM were detd. by systematic variation of the reactants in terms of reactivity and size for MIL-53(Al)-NH2, UiO-66(Zr)-NH2, and MIL-101(Al)-NH2. For this purpose, an acid-free digestion was prepd. that allows accurate yield comparison of synthesized acid sensitive amides employing soln. NMR. For MIL-53(Al)-NH2 and UiO-66(Zr)-NH2 best results were obtained using acid chlorides or anhydrides at 100°. For MIL-101(Al)-NH2 the application of acid anhydrides up to 100° was a suitable pathway for an efficient PSM. Optimization of all reaction parameters led to a postfunctionalization yield with acetic anhydride at 100° of 94.9 ± 0.5% for 2 h reaction time with MIL-53(Al)-NH2, 98 ± 3% for 10 min reaction time with UiO-66(Zr)-NH2, and 90 ± 1% yield for 10 min reaction time with MIL-101(Al)-NH2. Reactions with small carboxylic acid reactants or byproducts like HOAc led to damage or decompn. of UiO-66(Zr)-NH2 and MIL-101(Al)-NH2 probably due to postsynthetic ligand exchange. However, this limitation can be overcome by using carboxylic acids with high steric demand that might decelerate or disable ligand exchange and hence prevent the MOF scaffold from damages.
- 87Wang, C. T.; Vermeulen, N. A.; Kim, S. K.; Martinson, A. B. F.; Stoddart, J. F.; Hupp, J. T.; Farha, O. K. Scalable synthesis and post-modification of a mesoporous metal-organic framework called NU-1000. Nat. Protoc. 2016, 11, 149– 162, DOI: 10.1038/nprot.2016.001[Crossref], [PubMed], [CAS], Google Scholar87https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVSktrbN&md5=e812610d74a52cecdc482c24411d6075Scalable synthesis and post-modification of a mesoporous metal-organic framework called NU-1000Wang, Timothy C.; Vermeulen, Nicolaas A.; Kim, In Soo; Martinson, Alex B. F.; Stoddart, J. Fraser; Hupp, Joseph T.; Farha, Omar K.Nature Protocols (2016), 11 (1), 149-162CODEN: NPARDW; ISSN:1750-2799. (Nature Publishing Group)The synthesis of NU-1000, a highly robust mesoporous (contg. pores >2 nm) metal-org. framework (MOF), can be conducted efficiently on a multigram scale from inexpensive starting materials. Tetrabromopyrene and (4-(ethoxycarbonyl)phenyl)boronic acid can easily be coupled to prep. the requisite org. strut with four metal-binding sites in the form of four carboxylic acids, while zirconyl chloride octahydrate is used as a precursor for the well-defined metal oxide clusters. NU-1000 has been reported as an excellent candidate for the sepn. of gases, and it is a versatile scaffold for heterogeneous catalysis. In particular, it is ideal for the catalytic deactivation of nerve agents, and it shows great promise as a new generic platform for a wide range of applications. Multiple post-synthetic modification protocols have been developed using NU-1000 as the parent material, making it a potentially useful scaffold for several catalytic applications. The procedure for the prepn. of NU-1000 can be scaled up reliably, and it is suitable for the prodn. of 50 g of the tetracarboxylic acid contg. org. linker and 200 mg-2.5 g of NU-1000. The entire synthesis is performed without purifn. by column chromatog. and can be completed within 10 d.
- 88Johnson, R. L.; Schmidt-Rohr, K. Quantitative Solid-State 13C NMR with Signal Enhancement by Multiple Cross Polarization. J. Magn. Reson. 2014, 239, 44– 49, DOI: 10.1016/j.jmr.2013.11.009[Crossref], [PubMed], [CAS], Google Scholar88https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXisVaksLc%253D&md5=5c303a46d7b6a3bd6030d2828e890b50Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarizationJohnson, Robert L.; Schmidt-Rohr, KlausJournal of Magnetic Resonance (2014), 239 (), 44-49CODEN: JMARF3; ISSN:1090-7807. (Elsevier B.V.)A simple new method is presented that yields quant. solid-state magic-angle spinning (MAS) 13C NMR spectra of org. materials with good signal-to-noise ratios. It achieves long (>10 ms) cross polarization (CP) from 1H without significant magnetization losses due to relaxation and with a moderate duty cycle of the radio-frequency irradn., by multiple 1-ms CP periods alternating with 1H spin-lattice relaxation periods that repolarize the protons. The new method incorporates previous techniques that yield less distorted CP/MAS spectra, such as a linear variation ("ramp") of the radio-frequency field strength, and it overcomes their main limitation, which is T1ρ relaxation of the spin-locked 1H magnetization. The ramp of the radio-frequency field strength and the asymptotic limit of cross polarization makes the spectral intensity quite insensitive to the exact field strengths used. The new multiCP pulse sequence is a "drop-in" replacement for previous CP methods and produces no addnl. data-processing burden. Compared to the only reliable quant. 13C NMR method for unlabeled solids previously available, namely direct-polarization NMR, the measuring time is reduced by more than a factor of 50, enabling higher-throughput quant. NMR studies. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivs., plant matter, a highly arom. humic acid, and carbon materials made by low-temp. pyrolysis.
- 89Kandiah, M.; Nilsen, M. H.; Usseglio, S.; Jakobsen, S.; Olsbye, U.; Tilset, M.; Larabi, C.; Quadrelli, E. A.; Bonino, F.; Lillerud, K. P. Synthesis and Stability of Tagged UiO-66 Zr-MOFs. Chem. Mater. 2010, 22, 6632– 6640, DOI: 10.1021/cm102601v[ACS Full Text], [CAS], Google Scholar89https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsFaksbvP&md5=4c6f80512caaa2e5521e4e4f0b180b1aSynthesis and Stability of Tagged UiO-66 Zr-MOFsKandiah, Mathivathani; Nilsen, Merete Hellner; Usseglio, Sandro; Jakobsen, Soren; Olsbye, Unni; Tilset, Mats; Larabi, Cherif; Quadrelli, Elsje Alessandra; Bonino, Francesca; Lillerud, Karl PetterChemistry of Materials (2010), 22 (24), 6632-6640CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)The assembly of extended structures of the Zr-based MOF UiO-66 was pursued with three different com. available ligands: 2-aminobenzenedicarboxylic acid (H2N-H2BDC), 2-nitrobenzenedicarboxylic acid (ON-H2BDC), and 2-bromobenzenedicarboxylic acid (Br-H2BDC). Three new functionalized MOFs UiO-66-NH2 (1), UiO-66-NO2 (2), and UiO-66-Br (3) was initiated by detg. the reaction conditions necessary to produce MOFs with the same topol. of the parent UiO-66. Thermal and structural stability of the modified MOFs were examd. using powder X-ray diffraction anal. (PXRD) and thermogravimetric anal. (TGA). Langmuir surface areas were also detd. using N2 isotherms at 77 K to examine the porosity of the functionalized materials. Some changes in the surface area because of the presence of addnl. functionality on the BDC ligand were revealed. The results demonstrate the possibility of incorporating active functional groups into the UiO-66 structure almost without losing its exceptionally high thermal and chem. stability.
- 90Düren, T.; Bae, Y.-S.; Snurr, R. Q. Using Molecular Simulation to Characterise Metal–Organic Frameworks for Adsorption Applications. Chem. Soc. Rev. 2009, 38, 1237– 1247, DOI: 10.1039/b803498m[Crossref], [PubMed], [CAS], Google Scholar90https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXkvVamu7w%253D&md5=781eb0fd9a2a0ee1191346ba080d99bfUsing molecular simulation to characterise metal-organic frameworks for adsorption applicationsDueren, Tina; Bae, Youn-Sang; Snurr, Randall Q.Chemical Society Reviews (2009), 38 (5), 1237-1247CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Mol. simulation is a powerful tool to predict adsorption and to gain insight into the corresponding mol. level phenomena. In this tutorial review, we provide an overview of how mol. simulation can be used to characterize metal-org. frameworks for adsorption applications. Particular attention is drawn to how these insights can be combined to develop design principles for specific applications.
- 91Getman, R. B.; Bae, Y.-S.; Wilmer, C. E.; Snurr, R. Q. Review and Analysis of Molecular Simulations of Methane, Hydrogen, and Acetylene Storage in Metal–Organic Frameworks. Chem. Rev. 2012, 112, 703– 723, DOI: 10.1021/cr200217c[ACS Full Text], [CAS], Google Scholar91https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs1CrsLnF&md5=d8a0e205058909a8d3a171b2fafe676bReview and analysis of molecular simulations of methane, hydrogen, and acetylene storage in metal-organic frameworksGetman, Rachel B.; Bae, Youn-Sang; Wilmer, Christopher E.; Snurr, Randall Q.Chemical Reviews (Washington, DC, United States) (2012), 112 (2), 703-723CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Discussed and analyzed are recent computational studies of adsorption of methane, hydrogen, and acetylene in porous materials and it is shown how simulation was used to guide the design of these materials for gas storage. Addnl. discussed are the state-of-the-art in simulation techniques and the challenges assocd. with performing mol. simulations of gas mols. in MOFs. Throughout the review, both the successes and limitations of such simulations are highlighted. The paper is organized as follows: section 2 discusses models and methods commonly used to calc. gas adsorption in MOFs. Section 3 discusses how these models and methods were used to assess and design MOFs for CH4, H2, and C2H2 storage. Sections 4 and 5 discuss gas adsorption at open metal sites in the nodes and linkers, resp., the different computational strategies required to calc. adsorbate interactions at these sites, and the challenges assocd. with performing such calcns. Section 6 discusses how simulations can be used to calc. the av. enthalpy of adsorption, which is a useful quantity for assessing uptake capabilities. Section 7 discusses specific examples where simulations were used to guide expts.
- 92Civalleri, B.; Maurin, G.; Van Speybroeck, V. Frontiers in Modeling Metal–Organic Frameworks. Adv. Theory Simul. 2019, 2, 1900196, DOI: 10.1002/adts.201900196
- 93Vogiatzis, K. D.; Polynski, M. V.; Kirkland, J. K.; Townsend, J.; Hashemi, A.; Liu, C.; Pidko, E. A. Computational Approach to Molecular Catalysis by 3d Transition Metals: Challenges and Opportunities. Chem. Rev. 2019, 119, 2453– 2523, DOI: 10.1021/acs.chemrev.8b00361[ACS Full Text], [CAS], Google Scholar93https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVamtbbJ&md5=41023ddf4dcd9642362af0f34c458430Computational Approach to Molecular Catalysis by 3d Transition Metals: Challenges and OpportunitiesVogiatzis, Konstantinos D.; Polynski, Mikhail V.; Kirkland, Justin K.; Townsend, Jacob; Hashemi, Ali; Liu, Chong; Pidko, Evgeny A.Chemical Reviews (Washington, DC, United States) (2019), 119 (4), 2453-2523CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)Computational chem. provides a versatile toolbox for studying mechanistic details of catalytic reactions and holds promise to deliver practical strategies to enable the rational in silico catalyst design. The versatile reactivity and nontrivial electronic structure effects, common for systems based on 3d transition metals, introduce addnl. complexity that may represent a particular challenge to the std. computational strategies. In this review, we discuss the challenges and capabilities of modern electronic structure methods for studying the reaction mechanisms promoted by 3d transition metal mol. catalysts. Particular focus will be placed on the ways of addressing the multiconfigurational problem in electronic structure calcns. and the role of expert bias in the practical utilization of the available methods. The development of d. functionals designed to address transition metals is also discussed. Special emphasis is placed on the methods that account for solvation effects and the multicomponent nature of practical catalytic systems. This is followed by an overview of recent computational studies addressing the mechanistic complexity of catalytic processes by mol. catalysts based on 3d metals. Cases that involve noninnocent ligands, multicomponent reaction systems, metal-ligand and metal-metal cooperativity, as well as modeling complex catalytic systems such as metal-org. frameworks are presented. Conventionally, computational studies on catalytic mechanisms are heavily dependent on the chem. intuition and expert input of the researcher. Recent developments in advanced automated methods for reaction path anal. hold promise for eliminating such human-bias from computational catalysis studies. A brief overview of these approaches is presented in the final section of the review. The paper is closed with general concluding remarks.
- 94Bernales, V.; Ortuño, M. A.; Truhlar, D. G.; Cramer, C. J.; Gagliardi, L. Computational Design of Functionalized Metal–Organic Framework Nodes for Catalysis. ACS Cent. Sci. 2018, 4, 5– 19, DOI: 10.1021/acscentsci.7b00500[ACS Full Text], [CAS], Google Scholar94https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXitVShtLfN&md5=f706f2bdf686fc3334f1bc63a07290d7Computational Design of Functionalized Metal-Organic Framework Nodes for CatalysisBernales, Varinia; Ortuno, Manuel A.; Truhlar, Donald G.; Cramer, Christopher J.; Gagliardi, LauraACS Central Science (2018), 4 (1), 5-19CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)A review; recent progress in the synthesis and characterization of metal-org. frameworks (MOFs) has opened the door to an increasing no. of possible catalytic applications. The great versatility of MOFs creates a large chem. space, whose thorough exptl. examn. becomes practically impossible. Therefore, computational modeling is a key tool to support, rationalize, and guide exptl. efforts. In this outlook we survey the main methodologies employed to model MOFs for catalysis, and we review selected recent studies on the functionalization of their nodes. We pay special attention to catalytic applications involving natural gas conversion.
- 95Heinen, J.; Dubbeldam, D. On Flexible Force Fields for Metal–Organic Frameworks: Recent Developments and Future Prospects. WIREs Comp. Mol. Science 2018, 8, e1363 DOI: 10.1002/wcms.1363
- 96Addicoat, M. A.; Vankova, N.; Akter, I. F.; Heine, T. Extension of the Universal Force Field to Metal–Organic Frameworks. J. Chem. Theory Comput. 2014, 10, 880– 891, DOI: 10.1021/ct400952t[ACS Full Text], [CAS], Google Scholar96https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXpt1yhsw%253D%253D&md5=1808c01ed097213e66bd84a18072748bExtension of the Universal Force Field to Metal-Organic FrameworksAddicoat, Matthew A.; Vankova, Nina; Akter, Ismot Farjana; Heine, ThomasJournal of Chemical Theory and Computation (2014), 10 (2), 880-891CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)The Universal Force Field (UFF) (Rappe et al., J. Am. Chem. Soc.1992) provides a general approach to mol. mechanics for mols. and materials composed of elements throughout the periodic table. Though the method is tunable by the specification of bond orders and the introduction of effective charges, the presently available list of atom types is insufficient to treat various systems contg. transition metals, including metal-org. frameworks (MOFs). As MOFs are composite materials built of a combination of individually stable building blocks, a plethora of MOF structures are possible, and the prediction of their structure with a low-cost method is important. We have extended the UFF parameter set to include transition metal elements Zn, Cu, Ni, Co, Fe, Mn, Cr, V, Ti, Sc, and Al, as they occur in MOFs, and have proposed addnl. O parameters that provide reliable structures of the metal oxide clusters of the connectors. We have benchmarked the performance of the MOF extension to UFF (UFF4MOF) with respect to exptl. available data and to DFT calcns. The parameters are available in various well-spread programs, including GULP, deMonNano, and ADF, and all information is provided to include them in other mol. mechanics codes.
- 97Dzubak, A. L.; Lin, L.-C.; Kim, J.; Swisher, J. A.; Poloni, R.; Maximoff, S. N.; Smit, B.; Gagliardi, L. Ab Initio Carbon Capture in Open-Site Metal–Organic Frameworks. Nat. Chem. 2012, 4, 810– 816, DOI: 10.1038/nchem.1432[Crossref], [PubMed], [CAS], Google Scholar97https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xht1Wktr3O&md5=f56250bc5e6e0e4c65741837c918e63aAb initio carbon capture in open-site metal-organic frameworksDzubak, Allison L.; Lin, Li-Chiang; Kim, Jihan; Swisher, Joseph A.; Poloni, Roberta; Maximoff, Sergey N.; Smit, Berend; Gagliardi, LauraNature Chemistry (2012), 4 (10), 810-816CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)During the formation of metal-org. frameworks (MOFs), metal centers can coordinate with the intended org. linkers, but also with solvent mols. In this case, subsequent activation by removal of the solvent mols. creates unsatd. open metal sites known to have a strong affinity to CO2 mols., but their interactions are still poorly understood. Common force fields typically underestimate by as much as 2 orders of magnitude the adsorption of CO2 in open-site Mg-MOF-74, which has emerged as a promising MOF for CO2 capture. We present a systematic procedure to generate force fields using high-level quantum chem. calcns. Monte Carlo simulations based on an ab initio force field generated for CO2 in Mg-MOF-74 shed some light on the interpretation of thermodn. data from flue gas in this material. The force field describes accurately the chem. of the open metal sites, and is transferable to other structures. This approach may serve in mol. simulations in general and in the study of fluid-solid interactions.
- 98Mata, R. A.; Suhm, M. A. Benchmarking Quantum Chemical Methods: Are We Heading in the Right Direction?. Angew. Chem., Int. Ed. 2017, 56, 11011– 11018, DOI: 10.1002/anie.201611308[Crossref], [CAS], Google Scholar98https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXmslOmtbo%253D&md5=1b90a190613930f101c395f92fa6a0fbBenchmarking Quantum Chemical Methods: Are We Heading in the Right Direction?Mata, Ricardo A.; Suhm, Martin A.Angewandte Chemie, International Edition (2017), 56 (37), 11011-11018CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. This discussion leaves out, nonetheless, perhaps thebiggest threat to benchmarking activities in quantum chem.: the growing political pressure in several countries to focus only on immediately useful, applied science. Experimentalistsand theoreticians alike have to fight for the freedom tocontemplate the fundamental meeting points between their methods. And on this note we conclude, with the reminder that fortuitous success will not take us very far.
- 99Ongari, D.; Yakutovich, A. V.; Talirz, L.; Smit, B. Building a Consistent and Reproducible Database for Adsorption Evaluation in Covalent–Organic Frameworks. ACS Cent. Sci. 2019, 5, 1663– 1675, DOI: 10.1021/acscentsci.9b00619[ACS Full Text], [CAS], Google Scholar99https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvVeqsL%252FM&md5=8f47a5e3d00532e7064d5259e73ab1f1Building a Consistent and Reproducible Database for Adsorption Evaluation in Covalent-Organic FrameworksOngari, Daniele; Yakutovich, Aliaksandr V.; Talirz, Leopold; Smit, BerendACS Central Science (2019), 5 (10), 1663-1675CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)We present a workflow that traces the path from the bulk structure of a cryst. material to assessing its performance in carbon capture from coal's postcombustion flue gases. This workflow is applied to a database of 324 covalent-org. frameworks (COFs) reported in the literature, to characterize their CO2 adsorption properties using the following steps: (1) optimization of the crystal structure (at. positions and unit cell) using d. functional theory, (2) fitting at. point charges based on the electron d., (3) characterizing the pore geometry of the structures before and after optimization, (4) computing carbon dioxide and nitrogen isotherms using grand canonical Monte Carlo simulations with an empirical interaction potential, and finally, (5) assessing the CO2 parasitic energy via process modeling. The full workflow has been encoded in the Automated Interactive Infrastructure and Database for Computational Science (AiiDA). Both the workflow and the automatically generated provenance graph of our calcns. are made available on the Materials Cloud, allowing peers to inspect every input parameter and result along the workflow, download structures and files at intermediate stages, and start their research right from where this work has left off. In particular, our set of CURATED (Clean, Uniform, and Refined with Automatic Tracking from Exptl. Database) COFs, having optimized geometry and high-quality DFT-derived point charges, are available for further investigations of gas adsorption properties. We plan to update the database as new COFs are being reported. An automated and reproducible computational workflow is proposed, to systematically optimize the geometry of covalent-org. frameworks and evaluate their performances for carbon capture and storage.
- 100Jablonka, K. M.; Ongari, D.; Moosavi, S. M.; Smit, B. Big-Data Science in Porous Materials: Materials Genomics and Machine Learning arXiv 2020; https://arxiv.org/pdf/2001.06728.pdf.Google ScholarThere is no corresponding record for this reference.
- 101Uribe-Romo, F. J.; Hunt, J. R.; Furukawa, H.; Klöck, C.; O’Keeffe, M.; Yaghi, O. M. A Crystalline Imine-Linked 3-D Porous Covalent Organic Framework. J. Am. Chem. Soc. 2009, 131, 4570– 4571, DOI: 10.1021/ja8096256[ACS Full Text], [CAS], Google Scholar101https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXjtFKlsLs%253D&md5=c509041b8f8d5d6751cdd1221100fc7bA Crystalline Imine-Linked 3-D Porous Covalent Organic FrameworkUribe-Romo, Fernando J.; Hunt, Joseph R.; Furukawa, Hiroyasu; Kloeck, Cornelius; O'Keeffe, Michael; Yaghi, Omar M.Journal of the American Chemical Society (2009), 131 (13), 4570-4571CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A new cryst. porous three-dimensional covalent org. framework, termed COF-300, was synthesized and structurally characterized. Tetrahedral tetra-(4-anilyl)-methane and linear terephthaldehyde building blocks were condensed to form imine linkages in a material whose x-ray crystal structure shows five independent diamond frameworks. Despite the interpenetration, the structure has pores of 7.2 Å diam. Thus, COF-300 shows thermal stability up to 490 °C and permanent porosity with a surface area of 1360 m2 g-1.
- 102Brozek, C. K.; Michaelis, V. K.; Ong, T.-C.; Bellarosa, L.; López, N.; Griffin, R. G.; Dincǎ, M. Dynamic DMF Binding in MOF-5 Enables the Formation of Metastable Cobalt-Substituted MOF-5 Analogues. ACS Cent. Sci. 2015, 1, 252– 260, DOI: 10.1021/acscentsci.5b00247[ACS Full Text], [CAS], Google Scholar102https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht1Gnu7bP&md5=fc8ce0cf092690ed873a1d94dcdbdf0fDynamic DMF Binding in MOF-5 Enables the Formation of Metastable Cobalt-Substituted MOF-5 AnaloguesBrozek, Carl K.; Michaelis, Vladimir K.; Ong, Ta-Chung; Bellarosa, Luca; Lopez, Nuria; Griffin, Robert G.; Dinca, MirceaACS Central Science (2015), 1 (5), 252-260CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)Multinuclear solid-state NMR, mass spectrometry, first-principles mol. dynamics simulations, and other complementary evidence reveal that the coordination environment around the Zn2+ ions in MOF-5, one of the most iconic materials among metal-org. frameworks (MOFs), is not rigid. The Zn2+ ions bind solvent mols., thereby increasing their coordination no., and dynamically dissoc. from the framework itself. On av., one ion in each cluster has at least one coordinated N,N-dimethylformamide (DMF) mol., such that the formula of as-synthesized MOF-5 is defined as Zn4O(BDC)3(DMF)x (x = 1-2). Understanding the dynamic behavior of MOF-5 leads to a rational low-temp. cation exchange approach for the synthesis of metastable Zn4-xCoxO(terephthalate)3 (x > 1) materials, which have not been accessible through typical high-temp. solvothermal routes thus far.
- 103Wang, L. J.; Deng, H.; Furukawa, H.; Gándara, F.; Cordova, K. E.; Peri, D.; Yaghi, O. M. Synthesis and Characterization of Metal–Organic Framework-74 Containing 2, 4, 6, 8, and 10 Different Metals. Inorg. Chem. 2014, 53, 5881– 5883, DOI: 10.1021/ic500434a[ACS Full Text], [CAS], Google Scholar103https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXptVahtb8%253D&md5=58d90e56c354b5bb079545bfeed9dfffSynthesis and Characterization of Metal-Organic Framework-74 Containing 2, 4, 6, 8, and 10 Different MetalsWang, Lisa J.; Deng, Hexiang; Furukawa, Hiroyasu; Gandara, Felipe; Cordova, Kyle E.; Peri, Dani; Yaghi, Omar M.Inorganic Chemistry (2014), 53 (12), 5881-5883CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)Metal-org. frameworks (MOFs) contg. more than two kinds of metal ions mixed in one secondary building unit are rare because the synthesis often yields mixed MOF phases rather than a pure phase of a mixed-metal MOF (MM-MOF). In this study, we use a one-pot reaction to make microcryst. MOF-74 [M2(DOT); DOT = dioxidoterephthalate] with 2 (Mg and Co), 4 (Mg, Co, Ni, and Zn), 6 (Mg, Sr, Mn, Co, Ni, and Zn), 8 (Mg, Ca, Sr, Mn, Fe, Co, Ni, and Zn), and 10 (Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Zn, and Cd) different kinds of divalent metals. The powder X-ray diffraction patterns of MM-MOF-74 were identical with those of single-metal MOF-74, and no amorphous phases were found by SEM. The successful prepn. of guest-free MM-MOF-74 samples was confirmed by N2 adsorption measurements. Elemental anal. data also support the fact that all metal ions used in the MOF synthesis are incorporated within the same MOF-74 structure. Energy-dispersive X-ray spectroscopies indicate that metal ions are heterogeneously distributed within each of the cryst. particles. This approach is also employed to incorporate metal ions (i.e., Ca, Sr, Ba, and Cd) from which the parent MOF structure could not be made as a single-metal-contg. MOF.
- 104Deng, H.; Doonan, C. J.; Furukawa, H.; Ferreira, R. B.; Towne, J.; Knobler, C. B.; Wang, B.; Yaghi, O. M. Multiple Functional Groups of Varying Ratios in Metal-Organic Frameworks. Science 2010, 327, 846– 850, DOI: 10.1126/science.1181761[Crossref], [PubMed], [CAS], Google Scholar104https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhslWju7o%253D&md5=40f9720d9a7633e6102cab3256be0468Multiple Functional Groups of Varying Ratios in Metal-Organic FrameworksDeng, Hexiang; Doonan, Christian J.; Furukawa, Hiroyasu; Ferreira, Ricardo B.; Towne, John; Knobler, Carolyn B.; Wang, Bo; Yaghi, Omar M.Science (Washington, DC, United States) (2010), 327 (5967), 846-850CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Metal-org. frameworks (MOFs) can incorporate a large no. of different functionalities on linking groups in a way that mixes the linker, rather than forming sep. domains. The authors made complex MOFs from 1,4-benzenedicarboxylate (denoted by A in this work) and its derivs. -NH2, -Br, -(Cl)2, -NO2, -Me2, -C4H4, -(OC3H5)2, and -(OC7H7)2 (denoted by B to I,, resp.) to synthesize 18 multivariate (MTV) MOF-5 type structures that contain up to eight distinct functionalities in one phase. The backbone (Zn oxide and phenylene units) of these structures is ordered, but the distribution of functional groups is disordered. The complex arrangements of several functional groups within the pores can lead to properties that are not simply linear sums of those of the pure components. For example, a member of this series, MTV-MOF-5-EHI, exhibits up to 400% better selectivity for CO2 over CO compared with its best same-link counterparts.
- 105West, A. R. Basic Solid State Chemistry, 2nd ed.; John Wiley & Sons, Ltd: Chichester, 1999.Google ScholarThere is no corresponding record for this reference.
- 106Kong, X.; Deng, H.; Yan, F.; Kim, J.; Swisher, J. A.; Smit, B.; Yaghi, O. M.; Reimer, J. A. Mapping of Functional Groups in Metal-Organic Frameworks. Science 2013, 341, 882– 885, DOI: 10.1126/science.1238339[Crossref], [PubMed], [CAS], Google Scholar106https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXht12gsL%252FJ&md5=0ec9e8bf605a484a74a6097ed83190aaMapping of Functional Groups in Metal-Organic FrameworksKong, Xueqian; Deng, Hexiang; Yan, Fangyong; Kim, Jihan; Swisher, Joseph A.; Smit, Berend; Yaghi, Omar M.; Reimer, Jeffrey A.Science (Washington, DC, United States) (2013), 341 (6148), 882-885CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)We detd. the heterogeneous mesoscale spatial apportionment of functional groups in multivariate metal-org. frameworks (MTV-MOF-5) contg. BDC (1,4-benzenedicarboxylate) linkers with different functional groups-B (BDC-NH2), E (BDC-NO2), F [(BDC-Me)2], H [BDC-(OC3H5)2], and I [BDC-(OC7H7)2]-using solid-state NMR measurements combined with mol. simulations. The anal. reveals that these methods discern between random (EF), alternating (EI and EHI), and various cluster (BF) forms of functional group apportionments. This combined synthetic, characterization, and computational approach predicts the adsorptive properties of cryst. MTV-MOF systems. This methodol., developed in the context of ordered frameworks, is a 1st step in resolving the more general problem of spatial disorder in other ordered materials, including mesoporous materials, functionalized polymers, and defect distributions within cryst. solids.
- 107Schrimpf, W.; Jiang, J.; Ji, Z.; Hirschle, P.; Lamb, D. C.; Yaghi, O. M.; Wuttke, S. Chemical Diversity in a Metal–Organic Framework Revealed by Fluorescence Lifetime Imaging. Nat. Commun. 2018, 9, 1647, DOI: 10.1038/s41467-018-04050-w[Crossref], [PubMed], [CAS], Google Scholar107https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC1Mjmslektw%253D%253D&md5=36ebfe6db5e8d578a7527b52d347e4cfChemical diversity in a metal-organic framework revealed by fluorescence lifetime imagingSchrimpf Waldemar; Hirschle Patrick; Lamb Don C; Wuttke Stefan; Jiang Juncong; Ji Zhe; Yaghi Omar M; Yaghi Omar M; Wuttke StefanNature communications (2018), 9 (1), 1647 ISSN:.The presence and variation of chemical functionality and defects in crystalline materials, such as metal-organic frameworks (MOFs), have tremendous impact on their properties. Finding a means of identifying and characterizing this chemical diversity is an important ongoing challenge. This task is complicated by the characteristic problem of bulk measurements only giving a statistical average over an entire sample, leaving uncharacterized any diversity that might exist between crystallites or even within individual crystals. Here, we show that by using fluorescence imaging and lifetime analysis, both the spatial arrangement of functionalities and the level of defects within a multivariable MOF crystal can be determined for the bulk as well as for the individual constituent crystals. We apply these methods to UiO-67 to study the incorporation of functional groups and their consequences on the structural features. We believe that the potential of the techniques presented here in uncovering chemical diversity in what is generally assumed to be homogeneous systems can provide a new level of understanding of materials properties.
- 108ChemDraw Professional 16.0, Version 16.0.1.4; Perkin Elmer Informatics, 2017.Google ScholarThere is no corresponding record for this reference.
- 109Furukawa, H.; Ko, N.; Go, Y. B.; Aratani, N.; Choi, S. B.; Choi, E.; Yazaydin, A. Ö.; Snurr, R. Q.; O’Keeffe, M.; Kim, J.; Yaghi, O. M. Science 2010, 329, 424– 428, DOI: 10.1126/science.1192160[Crossref], [PubMed], [CAS], Google Scholar109https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptVWgsb8%253D&md5=ce5cd4101a6f96dc0d6c349bc478b3b0Ultrahigh Porosity in Metal-Organic FrameworksFurukawa, Hiroyasu; Ko, Nakeun; Go, Yong Bok; Aratani, Naoki; Choi, Sang Beom; Choi, Eunwoo; Yazaydin, A. Oezguer; Snurr, Randall Q.; O'Keeffe, Michael; Kim, Jaheon; Yaghi, Omar M.Science (Washington, DC, United States) (2010), 329 (5990), 424-428CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Cryst. solids with extended non-interpenetrating three-dimensional crystal structures were synthesized that support well-defined pores with internal diams. of up to 48 angstroms. The Zn4O(CO2)6 unit was joined with either one or two kinds of org. link, 4,4',4''-[benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)]tribenzoate (BTE), 4,4',44''-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate (BBC), 4,4',44''-benzene-1,3,5-triyl-tribenzoate (BTB)/2,6-naphthalenedicarboxylate (NDC), and BTE/biphenyl-4,4'-dicarboxylate (BPDC), to give four metal-org. frameworks (MOFs), MOF-180, -200, -205, and -210, resp. Members of this series of MOFs show exceptional porosities and gas (hydrogen, methane, and carbon dioxide) uptake capacities. For example, MOF-210 has Brunauer-Emmett-Teller and Langmuir surface areas of 6240 and 10,400 square meters per g, resp., and a total carbon dioxide storage capacity of 2870 mg per g. The vol.-specific internal surface area of MOF-210 (2060 square meters per cubic centimeter) is equiv. to the outer surface of nanoparticles (3-nm cubes) and near the ultimate adsorption limit for solid materials.
- 110PyMOL, Version 1.8.6.2, DeLano Scientific LLC; Schrödinger Inc., 2020.Google ScholarThere is no corresponding record for this reference.
- 111CrystalMakerX Software Ltd., Version 10.4.7; CrystalMaker Software Ltd., 2019.Google ScholarThere is no corresponding record for this reference.
- 112Momma, K. VESTA , Version 3.5.0, 2020.Google ScholarThere is no corresponding record for this reference.
- 113Bonneau, C.; O’Keeffe, M.; Proserpio, D. M.; Blatov, V. A.; Batten, S. R.; Bourne, S. A.; Lah, M. S.; Eon, J.-G.; Hyde, S. T.; Wiggin, S. B.; Öhrström, L. Deconstruction of Crystalline Networks into Underlying Nets: Relevance for Terminology Guidelines and Crystallographic Databases. Cryst. Growth Des. 2018, 18, 3411– 3418, DOI: 10.1021/acs.cgd.8b00126[ACS Full Text], [CAS], Google Scholar113https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptVCjurs%253D&md5=de9826db45e38dc8e4ce72ab8ae6cc68Deconstruction of Crystalline Networks into Underlying Nets: Relevance for Terminology Guidelines and Crystallographic DatabasesBonneau, Charlotte; O'Keeffe, Michael; Proserpio, Davide M.; Blatov, Vladislav A.; Batten, Stuart R.; Bourne, Susan A.; Lah, Myoung Soo; Eon, Jean-Guillaume; Hyde, Stephen T.; Wiggin, Seth B.; Ohrstrom, LarsCrystal Growth & Design (2018), 18 (6), 3411-3418CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)This communication briefly reviews why network topol. is an important tool (for understanding, comparing, communicating, designing, and solving crystal structures from powder diffraction data) and then discusses the terms of an IUPAC project dealing with various aspects of network topol. One is the ambiguity in node assignment, and this question is addressed in more detail. First, we define the most important approaches: the "all node" deconstruction considering all branch points of the linkers, the "single node" deconstruction considering only components mixed, and the ToposPro "std. representation" also considering linkers as one node but, if present, takes each metal atom as a sep. node. These methods are applied to a no. of metal-org. framework structures (MOFs, although this is just one example of materials this method is applicable on), and it is concluded that the "all node" method potentially yields more information on the structure in question but cannot be recommended as the only way of reporting the network topol. In addn., several terms needing definitions are discussed.
- 114Barthel, S.; Alexandrov, E. V.; Proserpio, D. M.; Smit, B. Distinguishing Metal–Organic Frameworks. Cryst. Growth Des. 2018, 18, 1738– 1747, DOI: 10.1021/acs.cgd.7b01663[ACS Full Text], [CAS], Google Scholar114https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhslyqtrY%253D&md5=ad3b3610b1f238eea55aa9303bd2fa06Distinguishing Metal-Organic FrameworksBarthel, Senja; Alexandrov, Eugeny V.; Proserpio, Davide M.; Smit, BerendCrystal Growth & Design (2018), 18 (3), 1738-1747CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)We consider two metal-org. frameworks as identical if they share the same bond network respecting the atom types. An algorithm is presented that decides whether two metal-org. frameworks are the same. It is based on distinguishing structures by comparing a set of descriptors that is obtained from the bond network. We demonstrate our algorithm by analyzing the CoRe MOF database of DFT optimized structures with DDEC partial at. charges using the program package ToposPro.
- 115Park, K. S.; Ni, Z.; Côté, A. P.; Choi, J. Y.; Huang, R.; Uribe-Romo, F. J.; Chae, H. K.; O’Keeffe, M.; Yaghi, O. M. Exceptional Chemical and Thermal Stability of Zeolitic Imidazolate Frameworks. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 10186– 10191, DOI: 10.1073/pnas.0602439103[Crossref], [PubMed], [CAS], Google Scholar115https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XntlKjtbo%253D&md5=c28cd5862d4765fe4e4937195f5bb4dfExceptional chemical and thermal stability of zeolitic imidazolate frameworksPark, Kyo Sung; Ni, Zheng; Cote, Adrien P.; Choi, Jae Yong; Huang, Rudan; Uribe-Romo, Fernando J.; Chae, Hee K.; O'Keeffe, Michael; Yaghi, Omar M.Proceedings of the National Academy of Sciences of the United States of America (2006), 103 (27), 10186-10191CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Twelve zeolitic imidazolate frameworks (ZIFs; termed ZIF-1 to -12) were synthesized as crystals by copolymn. of either Zn(II) (ZIF-1 to -4, -6 to -8, and -10 to -11) or Co(II) (ZIF-9 and -12) with imidazolate-type links. The ZIF crystal structures are based on the nets of seven distinct aluminosilicate zeolites: tetrahedral Si(Al) and the bridging O are replaced with transition metal ion and imidazolate link, resp. One example of mixed-coordination imidazolate of Zn(II) and In(III) (ZIF-5) based on the garnet net is reported. Study of the gas adsorption and thermal and chem. stability of two prototypical members, ZIF-8 and -11, demonstrated their permanent porosity (Langmuir surface area = 1,810 m2/g), high thermal stability (up to 550°), and remarkable chem. resistance to boiling alk. H2O and org. solvents.
- 116Hoffmann, R.; Kabanov, A. A.; Golov, A. A.; Proserpio, D. M. Homo Citans and Carbon Allotropes: For an Ethics of Citation. Angew. Chem., Int. Ed. 2016, 55, 10962– 10976, DOI: 10.1002/anie.201600655[Crossref], [CAS], Google Scholar116https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1WmtrbP&md5=bd0cb273434415b79773e6867540a305Homo Citans and Carbon Allotropes: For an Ethics of CitationHoffmann, Roald; Kabanov, Artyom A.; Golov, Andrey A.; Proserpio, Davide M.Angewandte Chemie, International Edition (2016), 55 (37), 10962-10976CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)This essay will first take a look at the reasons why appropriate citation is essential. It will then pass from ideals to two case studies of failures in citation in one subfield of chem. and physics,that of hypothetical carbon allotropes.
- 117Howarth, A. J.; Liu, Y.; Li, P.; Li, Z.; Wang, T. C.; Hupp, J. T.; Farha, O. K. Chemical, Thermal and Mechanical Stabilities of Metal–Organic Frameworks. Nat. Rev. Mater. 2016, 1, 15018, DOI: 10.1038/natrevmats.2015.18[Crossref], [PubMed], [CAS], Google Scholar117https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtVertrc%253D&md5=a5de585e107fd7232e4793e644b9dfddChemical, thermal and mechanical stabilities of metal-organic frameworksHowarth, Ashlee J.; Liu, Yangyang; Li, Peng; Li, Zhanyong; Wang, Timothy C.; Hupp, Joseph T.; Farha, Omar K.Nature Reviews Materials (2016), 1 (3), 15018CODEN: NRMADL; ISSN:2058-8437. (Nature Publishing Group)A review. The construction of thousands of well-defined, porous, metal-org. framework (MOF) structures, spanning a broad range of topologies and an even broader range of pore sizes and chem. functionalities, has fuelled the exploration of many applications. Accompanying this applied focus has been a recognition of the need to engender MOFs with mech., thermal and/or chem. stability. Chem. stability in acidic, basic and neutral aq. solns. is important. Advances over recent years have made it possible to design MOFs that possess different combinations of mech., thermal and chem. stability. Here, we review these advances and the assocd. design principles and synthesis strategies. We focus on how these advances may render MOFs effective as heterogeneous catalysts, both in chem. harsh condensed phases and in thermally challenging conditions relevant to gas-phase reactions. Finally, we briefly discuss future directions of study for the prodn. of highly stable MOFs.
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- Zhan-Ting Li, Shang-Bo Yu, Yamin Liu, Jia Tian, Dan-Wei Zhang. Supramolecular Organic Frameworks: Exploring Water-Soluble, Regular Nanopores for Biomedical Applications. Accounts of Chemical Research 2022, 55 (16) , 2316-2325. https://doi.org/10.1021/acs.accounts.2c00335
- Jun Lu, Xiaoyi Hu, Kevin M. Ung, Yinlong Zhu, Xiwang Zhang, Huanting Wang. Metal–Organic Frameworks as a Subnanometer Platform for Ion–Ion Selectivity. Accounts of Materials Research 2022, 3 (7) , 735-747. https://doi.org/10.1021/accountsmr.2c00071
- Tianze Qiu, Yongchen Wang, Yihan Li, Lin Zhu, Zhenxia Chen, Yu Jia, Pu Zhao, Wei Shi, Yaming Zhou, Yun Ling. Unprecedented Ferromagnetic Exchange Coupling of a Square-Planar Cu4O unit in a scu-Type Porous Metal–Organic Framework and Its Reticular Chemistry. Crystal Growth & Design 2022, 22 (7) , 4005-4011. https://doi.org/10.1021/acs.cgd.2c00356
- Guo-Quan Huang, Jun Chen, Yong-Liang Huang, Kun Wu, Dong Luo, Ji-Kang Jin, Ji Zheng, Shi-Hai Xu, Weigang Lu. Mixed-Linker Isoreticular Zn(II) Metal–Organic Frameworks as Brønsted Acid–Base Bifunctional Catalysts for Knoevenagel Condensation Reactions. Inorganic Chemistry 2022, 61 (21) , 8339-8348. https://doi.org/10.1021/acs.inorgchem.2c00941
- Jacopo Andreo, Romy Ettlinger, Orysia Zaremba, Quim Peña, Ulrich Lächelt, Roberto Fernández de Luis, Ralph Freund, Stefano Canossa, Evelyn Ploetz, Wei Zhu, Christian S. Diercks, Harald Gröger, Stefan Wuttke. Reticular Nanoscience: Bottom-Up Assembly Nanotechnology. Journal of the American Chemical Society 2022, 144 (17) , 7531-7550. https://doi.org/10.1021/jacs.1c11507
- Edward T. Conley, Bruce C. Gates. Life History of the Metal–Organic Framework UiO-66 Catalyzing Methanol Dehydration: Synthesis, Activation, Deactivation, and Demise. Chemistry of Materials 2022, 34 (7) , 3395-3408. https://doi.org/10.1021/acs.chemmater.2c00242
- Zhen Shan, Miaomiao Wu, Dongyang Zhu, Xiaowei Wu, Kan Zhang, Rafael Verduzco, Gen Zhang. 3D Covalent Organic Frameworks with Interpenetrated pcb Topology Based on 8-Connected Cubic Nodes. Journal of the American Chemical Society 2022, 144 (13) , 5728-5733. https://doi.org/10.1021/jacs.2c01037
- Wei Gong, Yi Xie, Thang Duc Pham, Suchetha Shetty, Florencia A. Son, Karam B. Idrees, Zhijie Chen, Haomiao Xie, Yan Liu, Randall Q. Snurr, Banglin Chen, Bassam Alameddine, Yong Cui, Omar K. Farha. Creating Optimal Pockets in a Clathrochelate-Based Metal–Organic Framework for Gas Adsorption and Separation: Experimental and Computational Studies. Journal of the American Chemical Society 2022, 144 (8) , 3737-3745. https://doi.org/10.1021/jacs.2c00011
- Jongwon Oh, Seok Min Yoon. Resistive Memory Devices Based on Reticular Materials for Electrical Information Storage. ACS Applied Materials & Interfaces 2021, 13 (48) , 56777-56792. https://doi.org/10.1021/acsami.1c16332
- Maria Valnice Boldrin Kallyni Irikura Beatriz Costa e Silva Juliano Carvalho Cardoso Simone Stulp Caroline Moraes da Silva Regina Célia Galvão Frem Christian Candia-Onfray Susana Rojas Ricardo Salazar . Electrochemical Applications of Metal−Organic Frameworks: Overview, Challenges, and Perspectives. , 395-453. https://doi.org/10.1021/bk-2021-1393.ch015
- Eunji Jin, Jiyeon Kim, Joohan Nam, D. ChangMo Yang, Hyein Jeong, Seonghoon Kim, Eunyoung Kang, Hye Jin Cho, Wonyoung Choe. Adsorptive Removal of Industrial Dye by Nanoporous Zr porphyrinic Metal–Organic Framework Microcubes. ACS Applied Nano Materials 2021, 4 (10) , 10068-10076. https://doi.org/10.1021/acsanm.1c01450
- Xue Wang, Mounib Bahri, Zhiwei Fu, Marc A. Little, Lunjie Liu, Hongjun Niu, Nigel D. Browning, Samantha Y. Chong, Linjiang Chen, John W. Ward, Andrew I. Cooper. A Cubic 3D Covalent Organic Framework with nbo Topology. Journal of the American Chemical Society 2021, 143 (37) , 15011-15016. https://doi.org/10.1021/jacs.1c08351
- Rui-Biao Lin, Zhangjing Zhang, Banglin Chen. Achieving High Performance Metal–Organic Framework Materials through Pore Engineering. Accounts of Chemical Research 2021, 54 (17) , 3362-3376. https://doi.org/10.1021/acs.accounts.1c00328
- Weimin Lin, Erlong Ning, Lingyi Yang, Yin Rao, Shuyin Peng, Qiaowei Li. Snapshots of Postsynthetic Modification in a Layered Metal–Organic Framework: Isometric Linker Exchange and Adaptive Linker Installation. Inorganic Chemistry 2021, 60 (16) , 11756-11763. https://doi.org/10.1021/acs.inorgchem.1c01341
- Liangjun Chen, Chengtao Gong, Xiaokang Wang, Fangna Dai, Mingchu Huang, Xiaowei Wu, Can-Zhong Lu, Yongwu Peng. Substoichiometric 3D Covalent Organic Frameworks Based on Hexagonal Linkers. Journal of the American Chemical Society 2021, 143 (27) , 10243-10249. https://doi.org/10.1021/jacs.1c03739
- Lifeng Yang, Karam B. Idrees, Zhijie Chen, Julia Knapp, Yongwei Chen, Xingjie Wang, Ran Cao, Xuan Zhang, Huabin Xing, Timur Islamoglu, Omar K. Farha. Nanoporous Water-Stable Zr-Based Metal–Organic Frameworks for Water Adsorption. ACS Applied Nano Materials 2021, 4 (5) , 4346-4350. https://doi.org/10.1021/acsanm.1c00638
- Yannick T. Guntern, Jan Vávra, Vikram V. Karve, Seyedeh Behnaz Varandili, Ona Segura Lecina, Chethana Gadiyar, Raffaella Buonsanti. Synthetic Tunability of Colloidal Covalent Organic Framework/Nanocrystal Hybrids. Chemistry of Materials 2021, 33 (7) , 2646-2654. https://doi.org/10.1021/acs.chemmater.1c00501
- Jiangfan Cao, Orysia T. Zaremba, Qi Lei, Evelyn Ploetz, Stefan Wuttke, Wei Zhu. Artificial Bioaugmentation of Biomacromolecules and Living Organisms for Biomedical Applications. ACS Nano 2021, 15 (3) , 3900-3926. https://doi.org/10.1021/acsnano.0c10144
- Xiaoling Liu, Jian Li, Bo Gui, Guiqing Lin, Qiang Fu, Sheng Yin, Xuefen Liu, Junliang Sun, Cheng Wang. A Crystalline Three-Dimensional Covalent Organic Framework with Flexible Building Blocks. Journal of the American Chemical Society 2021, 143 (4) , 2123-2129. https://doi.org/10.1021/jacs.0c12505
- Daniele Ongari, Leopold Talirz, Berend Smit. Too Many Materials and Too Many Applications: An Experimental Problem Waiting for a Computational Solution. ACS Central Science 2020, 6 (11) , 1890-1900. https://doi.org/10.1021/acscentsci.0c00988
- Melike Babucci, Adisak Guntida, Bruce C. Gates. Atomically Dispersed Metals on Well-Defined Supports including Zeolites and Metal–Organic Frameworks: Structure, Bonding, Reactivity, and Catalysis. Chemical Reviews 2020, 120 (21) , 11956-11985. https://doi.org/10.1021/acs.chemrev.0c00864
- Penghao Li, Matthew R. Ryder, J. Fraser Stoddart. Hydrogen-Bonded Organic Frameworks: A Rising Class of Porous Molecular Materials. Accounts of Materials Research 2020, 1 (1) , 77-87. https://doi.org/10.1021/accountsmr.0c00019
- Xiaobo Yu, Wenting Chang, Ziyan Cai, Cilin Yu, Lin Lai, Ziyin Zhou, Ping Li, Yangyi Yang, Chenghui Zeng. Hg2+ detection and information encryption of new [1+1] lanthanide cluster. Talanta 2024, 266 , 125105. https://doi.org/10.1016/j.talanta.2023.125105
- Nagore Barroso, Jacopo Andreo, Garikoitz Beobide, Oscar Castillo, Antonio Luque, Sonia Pérez-Yáñez, Stefan Wuttke. Magnetic sustentation as an adsorption characterization technique for paramagnetic metal-organic frameworks. Communications Chemistry 2023, 6 (1) https://doi.org/10.1038/s42004-022-00799-w
- Dongyang Zhu, Yifan Zhu, Yu Chen, Qianqian Yan, Han Wu, Chun-Yen Liu, Xu Wang, Lawrence B. Alemany, Guanhui Gao, Thomas P. Senftle, Yongwu Peng, Xiaowei Wu, Rafael Verduzco. Three-dimensional covalent organic frameworks with pto and mhq-z topologies based on Tri- and tetratopic linkers. Nature Communications 2023, 14 (1) https://doi.org/10.1038/s41467-023-38538-x
- Tahereh Musabeygi, Nasser Goudarzi, Mahdi Mirzaee, Mansour Arab-Chamjangali. Design of a ternary magnetic composite based on a covalent organic framework and Ag nanoparticles for simultaneous photodegradation of organic pollutants under LED light irradiation: Application of BBD-RSM modeling and resolution of spectral overlap of analytes. Journal of Alloys and Compounds 2023, 964 , 171249. https://doi.org/10.1016/j.jallcom.2023.171249
- Min Ying Tsang, Anna Sinelshchikova, Orysia Zaremba, Flora Schöfbeck, Alejandra Durán Balsa, Michael R. Reithofer, Stefan Wuttke, Jia Min Chin. Multilength Scale Hierarchy in Metal‐Organic Frameworks: Synthesis, Characterization and the Impact on Applications. Advanced Functional Materials 2023, 30 https://doi.org/10.1002/adfm.202308376
- Chengyue Yang, Ziye Li, Zhuang Hu, Yu Sun, Feng Chen, Tuanyu Guo, Jianshe Hu. Multifunctional 3D PAN-C3N4 @COFs for efficiently dynamic and static adsorption of mercury and its chemometric detection. Process Safety and Environmental Protection 2023, 177 , 496-506. https://doi.org/10.1016/j.psep.2023.07.025
- Subhajit Dutta, Roberto Fernández de Luis, Joanna Goscianska, Aude Demessence, Romy Ettlinger, Stefan Wuttke. Metal–Organic Frameworks for Water Desalination. Advanced Functional Materials 2023, 80 https://doi.org/10.1002/adfm.202304790
- Zhenqian Zheng, Yuhao Yang, Di Chen, Song Wang, Qiulin Li, Ziyang Zhang, Wei Li, Bajin Chen, Wen‐Jun Wang, Pingwei Liu. Engineering hollow covalent organic framework particle through self‐templated crystallization. Journal of Polymer Science 2023, 604 https://doi.org/10.1002/pol.20230362
- Patricia De La Torre, Lun An, Christopher J. Chang. Porosity as a Design Element for Developing Catalytic Molecular Materials for Electrochemical and Photochemical Carbon Dioxide Reduction. Advanced Materials 2023, 16 https://doi.org/10.1002/adma.202302122
- Mahyar Panahi‐Sarmad, Shakiba Samsami, Ahmadreza Ghaffarkhah, Seyyed Alireza Hashemi, Shayan Ghasemi, Majed Amini, Stefan Wuttke, Orlando Rojas, Kam Chiu Tam, Feng Jiang, Mohammad Arjmand, Farhad Ahmadijokani, Milad Kamkar. MOF‐Based Electromagnetic Shields Multiscale Design: Nanoscale Chemistry, Microscale Assembly, and Macroscale Manufacturing. Advanced Functional Materials 2023, 11 https://doi.org/10.1002/adfm.202304473
- Xiaokang Wang, Hongyan Liu, Yue Li, Xinlei Yang, Fei Gao, Xiaoqing Wang, Zixi Kang, Weidong Fan, Daofeng Sun. Metal-organic frameworks for C2H2/CO2 separation: Recent development. Coordination Chemistry Reviews 2023, 482 , 215093. https://doi.org/10.1016/j.ccr.2023.215093
- Ann Mariella Babu, Anitha Varghese. Electrochemical deposition for metal organic Frameworks: Advanced Energy, Catalysis, sensing and separation applications. Journal of Electroanalytical Chemistry 2023, 937 , 117417. https://doi.org/10.1016/j.jelechem.2023.117417
- Jiarui Fu, Ziyan He, Eduardo Schott, Honghan Fei, Min Tu, Yi‐nan Wu. Sequential Sol‐Gel Self‐Assembly and Nonclassical Gel‐Crystal Transformation of the Metal‐Organic Framework Gel. Small 2023, 19 (18) https://doi.org/10.1002/smll.202206718
- Yu Li, Xiaojing Zhou, Dameng Gao, Peng Cheng, Jian‐Gong Ma, Datong Song. Impact of Ligands on the Properties of Lanthanide Metal‐Organic Frameworks. Zeitschrift für anorganische und allgemeine Chemie 2023, 649 (8) https://doi.org/10.1002/zaac.202200379
- Rebecca Vismara, Stephanie Terruzzi, Angelo Maspero, Toni Grell, Filippo Bossola, Angelo Sironi, Simona Galli, Jorge A. R. Navarro, Valentina Colombo. CO 2 Adsorption in a Robust Iron(III) Pyrazolate‐Based MOF: Molecular‐Level Details and Frameworks Dynamics From Powder X‐ray Diffraction Adsorption Isotherms. Advanced Materials 2023, https://doi.org/10.1002/adma.202209907
- Suchetha Shetty, Karam B. Idrees, Haomiao Xie, Bassam Alameddine, Omar K. Farha. Synthesis of zirconium-based metal–organic frameworks with iron( ii ) clathrochelate ligands. CrystEngComm 2023, 25 (10) , 1550-1555. https://doi.org/10.1039/D2CE01686A
- Shiyu Nie, Fengfeng Chen, Tianbo Shen, Tingting Wang, Ningyu Di, Junkuo Gao. Incorporation of 1-ethyl-3-methyl-imidazolium acetate into UiO-66 as an efficient sorbent for carbon dioxide capture. New Journal of Chemistry 2023, 47 (5) , 2257-2263. https://doi.org/10.1039/D2NJ05826J
- Yang Liu, Xinyue Jiang, Likun Chen, Yan Cui, Qiu-Yan Li, Xinsheng Zhao, Xiguang Han, Yong-Chao Zheng, Xiao-Jun Wang. Rational design of a phenothiazine-based donor–acceptor covalent organic framework for enhanced photocatalytic oxidative coupling of amines and cyclization of thioamides. Journal of Materials Chemistry A 2023, 11 (3) , 1208-1215. https://doi.org/10.1039/D2TA07177K
- Lucas S. R. Cavalcante, Makena A. Dettmann, Tyler Sours, Dong Yang, Luke L. Daemen, Bruce C. Gates, Ambarish R. Kulkarni, Adam J. Moulé. Elucidating correlated defects in metal organic frameworks using theory-guided inelastic neutron scattering spectroscopy. Materials Horizons 2023, 10 (1) , 187-196. https://doi.org/10.1039/D2MH00914E
- Zhiling Zheng, Ha L. Nguyen, Nikita Hanikel, Kelvin Kam-Yun Li, Zihui Zhou, Tianqiong Ma, Omar M. Yaghi. High-yield, green and scalable methods for producing MOF-303 for water harvesting from desert air. Nature Protocols 2023, 18 (1) , 136-156. https://doi.org/10.1038/s41596-022-00756-w
- Fatemeh Ganjali, Peyman Ghorbani, Nima Khaleghi, Maryam Saidi Mehrabad. Evolution in MOF Porosity, Modularity, and Topology. 2023, 91-100. https://doi.org/10.1007/978-3-031-18675-2_7
- Andreina García, Bárbara Rodríguez, Maibelin Rosales, Yurieth M. Quintero, Paula G. Saiz, Ander Reizabal, Stefan Wuttke, Leire Celaya-Azcoaga, Ainara Valverde, Roberto Fernández de Luis. A State-of-the-Art of Metal-Organic Frameworks for Chromium Photoreduction vs. Photocatalytic Water Remediation. Nanomaterials 2022, 12 (23) , 4263. https://doi.org/10.3390/nano12234263
- Bala Suleiman, Che Azurahanim Che Abdullah, Mohamed Ibrahim Mohamed Tahir, Leen Bahbouh, Mohd Basyaruddin Abdul Rahman. Covalent organic frameworks: Recent advances in synthesis, characterization and their application in the environmental and agricultural sectors. Results in Chemistry 2022, 6 , 100719. https://doi.org/10.1016/j.rechem.2022.100719
- Guanghui Yang, Zhe Zhang, Congcong Yin, Xiansong Shi, Yong Wang. Polyamide membranes enabled by covalent organic framework nanofibers for efficient reverse osmosis. Journal of Polymer Science 2022, 60 (21) , 2999-3008. https://doi.org/10.1002/pol.20210664
- Yuan Chen, Jianyao Li, Qin Zhu, Kun Fan, Yiqing Cao, Guoqun Zhang, Chenyang Zhang, Yanbo Gao, Jincheng Zou, Tianyou Zhai, Chengliang Wang. Two‐Dimensional Organic Supramolecule via Hydrogen Bonding and π–π Stacking for Ultrahigh Capacity and Long‐Life Aqueous Zinc–Organic Batteries. Angewandte Chemie 2022, 134 (37) https://doi.org/10.1002/ange.202116289
- Yuan Chen, Jianyao Li, Qin Zhu, Kun Fan, Yiqing Cao, Guoqun Zhang, Chenyang Zhang, Yanbo Gao, Jincheng Zou, Tianyou Zhai, Chengliang Wang. Two‐Dimensional Organic Supramolecule via Hydrogen Bonding and π–π Stacking for Ultrahigh Capacity and Long‐Life Aqueous Zinc–Organic Batteries. Angewandte Chemie International Edition 2022, 61 (37) https://doi.org/10.1002/anie.202116289
- Yang Deng, Yue Wang, Xiao Xiao, Brett Jacob Saucedo, Zhijun Zhu, Mingsen Xie, Xinru Xu, Kun Yao, Yanling Zhai, Zhen Zhang, Jun Chen. Progress in Hybridization of Covalent Organic Frameworks and Metal–Organic Frameworks. Small 2022, 18 (38) https://doi.org/10.1002/smll.202202928
- Zengyu Li, Qingqing Jia, Yuan Chen, Kun Fan, Chenyang Zhang, Guoqun Zhang, Ming Xu, Minglei Mao, Jing Ma, Wenping Hu, Chengliang Wang. A Small Molecular Symmetric All‐Organic Lithium‐Ion Battery. Angewandte Chemie International Edition 2022, 61 (33) https://doi.org/10.1002/anie.202207221
- R. Eric Sikma, Krista P. Balto, Joshua S. Figueroa, Seth M. Cohen. Metal–Organic Frameworks with Low‐Valent Metal Nodes. Angewandte Chemie International Edition 2022, 61 (33) https://doi.org/10.1002/anie.202206353
- Vageesha W. Liyana Gunawardana, Tyler J. Finnegan, Carson E. Ward, Curtis E. Moore, Jovica D. Badjić. Dissipative Formation of Covalent Basket Cages. Angewandte Chemie International Edition 2022, 61 (33) https://doi.org/10.1002/anie.202207418
- Vageesha W. Liyana Gunawardana, Tyler J. Finnegan, Carson E. Ward, Curtis E. Moore, Jovica D. Badjić. Dissipative Formation of Covalent Basket Cages. Angewandte Chemie 2022, 134 (33) https://doi.org/10.1002/ange.202207418
- Zengyu Li, Qingqing Jia, Yuan Chen, Kun Fan, Chenyang Zhang, Guoqun Zhang, Ming Xu, Minglei Mao, Jing Ma, Wenping Hu, Chengliang Wang. A Small Molecular Symmetric All‐Organic Lithium‐Ion Battery. Angewandte Chemie 2022, 134 (33) https://doi.org/10.1002/ange.202207221
- R. Eric Sikma, Krista P. Balto, Joshua S. Figueroa, Seth M. Cohen. Metal–Organic Frameworks with Low‐Valent Metal Nodes. Angewandte Chemie 2022, 134 (33) https://doi.org/10.1002/ange.202206353
- Jia-Long Ling, Chuan-De Wu. Transformation of metal–organic frameworks with retained networks. Chemical Communications 2022, 58 (62) , 8602-8613. https://doi.org/10.1039/D2CC02865D
- Shiye Li, Wensheng Mao, Li Zhang, Hongmei Huang, Yi Xiao, Liqiu Mao, Rong Tan, Zaihui Fu, Ningya Yu, Dulin Yin. Ionic liquid-modulated aerobic oxidation of isoeugenol and β-caryophyllene via nanoscale Cu-MOFs under mild conditions. Molecular Catalysis 2022, 528 , 112416. https://doi.org/10.1016/j.mcat.2022.112416
- Gang‐Ding Wang, Yong‐Zhi Li, Wen‐Juan Shi, Lei Hou, Yao‐Yu Wang, Zhonghua Zhu. One‐Step C 2 H 4 Purification from Ternary C 2 H 6 /C 2 H 4 /C 2 H 2 Mixtures by a Robust Metal–Organic Framework with Customized Pore Environment. Angewandte Chemie International Edition 2022, 61 (28) https://doi.org/10.1002/anie.202205427
- Gang‐Ding Wang, Yong‐Zhi Li, Wen‐Juan Shi, Lei Hou, Yao‐Yu Wang, Zhonghua Zhu. One‐Step C 2 H 4 Purification from Ternary C 2 H 6 /C 2 H 4 /C 2 H 2 Mixtures by a Robust Metal–Organic Framework with Customized Pore Environment. Angewandte Chemie 2022, 134 (28) https://doi.org/10.1002/ange.202205427
- Ainara Valverde, David Payno, Luis Lezama, José M. Laza, Stefan Wuttke, Roberto Fernández de Luis. Multivariate Functionalization of UiO‐66 for Photocatalytic Water Remediation. Advanced Sustainable Systems 2022, 6 (7) https://doi.org/10.1002/adsu.202200024
- Yi Luo, Saientan Bag, Orysia Zaremba, Adrian Cierpka, Jacopo Andreo, Stefan Wuttke, Pascal Friederich, Manuel Tsotsalas. MOF Synthesis Prediction Enabled by Automatic Data Mining and Machine Learning**. Angewandte Chemie International Edition 2022, 61 (19) https://doi.org/10.1002/anie.202200242
- Yi Luo, Saientan Bag, Orysia Zaremba, Adrian Cierpka, Jacopo Andreo, Stefan Wuttke, Pascal Friederich, Manuel Tsotsalas. Vorhersage der MOF‐Synthese durch automatisches Data‐Mining und maschinelles Lernen**. Angewandte Chemie 2022, 134 (19) https://doi.org/10.1002/ange.202200242
- Bo Gui, Huimin Ding, Yuanpeng Cheng, Arindam Mal, Cheng Wang. Structural design and determination of 3D covalent organic frameworks. Trends in Chemistry 2022, 4 (5) , 437-450. https://doi.org/10.1016/j.trechm.2022.01.002
- Zhiyu Qu, Dan Wu, Jing Jin, Guoping Yang, Yao-Yu Wang. Fabrication of a series of isostructural water-stable lanthanide metal-organic frameworks: Tunable luminescence, sensing for antibiotics and magnetic properties. Journal of Solid State Chemistry 2022, 309 , 123003. https://doi.org/10.1016/j.jssc.2022.123003
- Qingqing Pang, Lingyi Yang, Qiaowei Li. Vacancies in Metal−Organic Frameworks: Formation, Arrangement, and Functions. Small Structures 2022, 3 (5) https://doi.org/10.1002/sstr.202100203
- Eugeny V. Alexandrov, Alexander P. Shevchenko, Nadezhda A. Nekrasova, Vladislav A. Blatov. Topological methods for analysis and design of coordination polymers. Russian Chemical Reviews 2022, 91 (4) , RCR5032. https://doi.org/10.1070/RCR5032
- Guang-Hui Yang, Zhe Zhang, Cong-Cong Yin, Xian-Song Shi, Yong Wang. Morphology Engineering for Covalent Organic Frameworks (COFs) by Surfactant Mediation and Acid Adjustment. Chinese Journal of Polymer Science 2022, 40 (4) , 338-344. https://doi.org/10.1007/s10118-022-2676-6
- R. Eric Sikma, Seth M. Cohen. Metal–Organic Frameworks with Zero and Low‐Valent Metal Nodes Connected by Tetratopic Phosphine Ligands. Angewandte Chemie 2022, 134 (11) https://doi.org/10.1002/ange.202115454
- R. Eric Sikma, Seth M. Cohen. Metal–Organic Frameworks with Zero and Low‐Valent Metal Nodes Connected by Tetratopic Phosphine Ligands. Angewandte Chemie International Edition 2022, 61 (11) https://doi.org/10.1002/anie.202115454
- Guilherme Arroyos, Caroline M. da Silva, Lucas B. Theodoroviez, Jonatas E. M. Campanella, Regina C. G. Frem. Insights on Luminescent Micro‐ and Nanospheres of Infinite Coordination Polymers. Chemistry – A European Journal 2022, 28 (2) https://doi.org/10.1002/chem.202103104
- Wanqi Sun, Jianbo Hu, Simon Duttwyler, Lingyao Wang, Rajamani Krishna, Yuanbin Zhang. Highly selective gas separation by two isostructural boron cluster pillared MOFs. Separation and Purification Technology 2022, 283 , 120220. https://doi.org/10.1016/j.seppur.2021.120220
- Adrian Fuchs, Petra Mannhardt, Patrick Hirschle, Haoze Wang, Irina Zaytseva, Zhe Ji, Omar Yaghi, Stefan Wuttke, Evelyn Ploetz. Single Crystals Heterogeneity Impacts the Intrinsic and Extrinsic Properties of Metal–Organic Frameworks. Advanced Materials 2022, 34 (3) https://doi.org/10.1002/adma.202104530
- Nem Singh, Subin Son, Jusung An, Ilwha Kim, Minhyeok Choi, Na Kong, Wei Tao, Jong Seung Kim. Nanoscale porous organic polymers for drug delivery and advanced cancer theranostics. Chemical Society Reviews 2021, 50 (23) , 12883-12896. https://doi.org/10.1039/D1CS00559F
- Ralph Freund, Stefano Canossa, Seth M. Cohen, Wei Yan, Hexiang Deng, Vincent Guillerm, Mohamed Eddaoudi, David G. Madden, David Fairen‐Jimenez, Hao Lyu, Lauren K. Macreadie, Zhe Ji, Yuanyuan Zhang, Bo Wang, Frederik Haase, Christof Wöll, Orysia Zaremba, Jacopo Andreo, Stefan Wuttke, Christian S. Diercks. 25 Years of Reticular Chemistry. Angewandte Chemie International Edition 2021, 60 (45) , 23946-23974. https://doi.org/10.1002/anie.202101644
- Ralph Freund, Orysia Zaremba, Giel Arnauts, Rob Ameloot, Grigorii Skorupskii, Mircea Dincă, Anastasiya Bavykina, Jorge Gascon, Aleksander Ejsmont, Joanna Goscianska, Markus Kalmutzki, Ulrich Lächelt, Evelyn Ploetz, Christian S. Diercks, Stefan Wuttke. The Current Status of MOF and COF Applications. Angewandte Chemie International Edition 2021, 60 (45) , 23975-24001. https://doi.org/10.1002/anie.202106259
- Ralph Freund, Stefano Canossa, Seth M. Cohen, Wei Yan, Hexiang Deng, Vincent Guillerm, Mohamed Eddaoudi, David G. Madden, David Fairen‐Jimenez, Hao Lyu, Lauren K. Macreadie, Zhe Ji, Yuanyuan Zhang, Bo Wang, Frederik Haase, Christof Wöll, Orysia Zaremba, Jacopo Andreo, Stefan Wuttke, Christian S. Diercks. 25 Jahre retikuläre Chemie. Angewandte Chemie 2021, 133 (45) , 24142-24173. https://doi.org/10.1002/ange.202101644
- Ralph Freund, Orysia Zaremba, Giel Arnauts, Rob Ameloot, Grigorii Skorupskii, Mircea Dincă, Anastasiya Bavykina, Jorge Gascon, Aleksander Ejsmont, Joanna Goscianska, Markus Kalmutzki, Ulrich Lächelt, Evelyn Ploetz, Christian S. Diercks, Stefan Wuttke. Der derzeitige Stand von MOF‐ und COF‐Anwendungen. Angewandte Chemie 2021, 133 (45) , 24174-24202. https://doi.org/10.1002/ange.202106259
- Kai Lv, Sebastian Fichter, Mei Gu, Juliane März, Moritz Schmidt. An updated status and trends in actinide metal-organic frameworks (An-MOFs): From synthesis to application. Coordination Chemistry Reviews 2021, 446 , 214011. https://doi.org/10.1016/j.ccr.2021.214011
- Fábio F. Paiva, Leonildo A. Ferreira, Iara M.L. Rosa, Rafaela M.R. da Silva, Fernando Sigoli, Odivaldo Cambraia Alves, Flávio Garcia, Guilherme P. Guedes, Maria Vanda Marinho. Heterobimetallic metallacrown of EuIIICuII5 with 5-methyl-2-pyrazinehydroxamic acid: Synthesis, crystal structure, magnetism, and the influence of CuII ions on the photoluminescent properties. Polyhedron 2021, 209 , 115466. https://doi.org/10.1016/j.poly.2021.115466
- Kangmin Lee, Jumin Park, Intek Song, Seok Min Yoon. The Magnetism of Metal–Organic Frameworks for Spintronics. Bulletin of the Korean Chemical Society 2021, 42 (9) , 1170-1183. https://doi.org/10.1002/bkcs.12362
- Bhanu Nirosha Yalamandala, Wei‐Ting Shen, Sheng‐Hao Min, Wen‐Hsuan Chiang, Shing‐Jyh Chang, Shang‐Hsiu Hu. Advances in Functional Metal‐Organic Frameworks Based On‐Demand Drug Delivery Systems for Tumor Therapeutics. Advanced NanoBiomed Research 2021, 1 (8) https://doi.org/10.1002/anbr.202100014
- Yuto Suzuki, Mario Gutiérrez, Senri Tanaka, Eduardo Gomez, Norimitsu Tohnai, Nobuhiro Yasuda, Nobuyuki Matubayasi, Abderrazzak Douhal, Ichiro Hisaki. Construction of isostructural hydrogen-bonded organic frameworks: limitations and possibilities of pore expansion. Chemical Science 2021, 12 (28) , 9607-9618. https://doi.org/10.1039/D1SC02690A
- Yang Li, Meghdad Karimi, Yun-Nan Gong, Nan Dai, Vahid Safarifard, Hai-Long Jiang. Integration of metal-organic frameworks and covalent organic frameworks: Design, synthesis, and applications. Matter 2021, 4 (7) , 2230-2265. https://doi.org/10.1016/j.matt.2021.03.022
- Ha L. Nguyen. Reticular design and crystal structure determination of covalent organic frameworks. Chemical Science 2021, 12 (25) , 8632-8647. https://doi.org/10.1039/D1SC00738F
- Vonika Ka‐Man Au, Shuk Ying Kwan, Mio Nga Lai, Kam‐Hung Low. Dual‐Functional Mesoporous Copper(II) Metal‐Organic Frameworks for the Remediation of Organic Dyes. Chemistry – A European Journal 2021, 27 (35) , 9174-9179. https://doi.org/10.1002/chem.202100289
- Peidong Yang, Douglas S. Clark, Omar M. Yaghi. Envisioning the “Air Economy” — Powered by Reticular Chemistry and Sunlight for Clean Air, Clean Energy, and Clean Water. Molecular Frontiers Journal 2021, 05 (01n02) , 30-37. https://doi.org/10.1142/S2529732521400046
- Jubaraj B. Baruah. Naphthalenedicarboxylate based metal organic frameworks: Multifaceted material. Coordination Chemistry Reviews 2021, 437 , 213862. https://doi.org/10.1016/j.ccr.2021.213862
- Jun Guo, Yutian Qin, Yanfei Zhu, Xiaofei Zhang, Chang Long, Meiting Zhao, Zhiyong Tang. Metal–organic frameworks as catalytic selectivity regulators for organic transformations. Chemical Society Reviews 2021, 50 (9) , 5366-5396. https://doi.org/10.1039/D0CS01538E
- Laurens Bourda, Chidharth Krishnaraj, Pascal Van Der Voort, Kristof Van Hecke. Conquering the crystallinity conundrum: efforts to increase quality of covalent organic frameworks. Materials Advances 2021, 2 (9) , 2811-2845. https://doi.org/10.1039/D1MA00008J
- Ha L Nguyen. Perspectives on titanium-based metal–organic frameworks. Journal of Physics: Energy 2021, 3 (2) , 021003. https://doi.org/10.1088/2515-7655/abe3c9
Abstract
Figure 1
Figure 1. Expansion of reticular chemistry from 1995–2020. The bright yellow dots represent the institutes actively working on MOFs, COFs, and ZIFs. The search was restricted to the terms MOF, COF, and ZIF in original articles and reviews, and the affiliations were counted only for the corresponding authors. In total, as of the day of the search May 4, 2020, researchers in 5102 institutes and 102 countries (country icon) have published a total of 27,524 papers (manuscript icon).
Figure 2
Figure 2. A workflow illustration of the most common scientific activities and related parameters (blue, brown, and green cycles), which reticular researchers follow in their synthesis and characterization of solids. This includes the quality indicators (correspondingly colored squares), which should be carefully considered in reporting of results.
Figure 3
Figure 3. Representation of PXRD patterns for MOFs and COFs. Comparison between the experimental and simulated patterns of MOF-520 (a). (65) Because of the large difference in relative intensities in different 2θ regions, a blown up area is required. A synchrotron collected (wavelength indicated) PXRD pattern of COF-112 (b). (66) In this case, a Pawley refinement can be made, since there are enough experimentally observed reflections. The nature of the refinement is indicated in the figure legend, and the image includes the calculated pattern for the corresponding model, for visual comparison of the expected relative intensities.
Figure 4
Figure 4. (a–d) Four different types of pure-metal and mixed-metal ZIF-8 samples are shown with good clarity and information completeness. This is achieved by presenting several crystals and, when necessary, magnifications highlighting the morphology of single specimens. Note that each set of high- and low-magnification pictures has identical scale bar length (0.1 and 1 μm, respectively) to facilitate the comparison between different samples. Reproduced from ref (76) with permission from the Royal Society of Chemistry.
Figure 5
Figure 5. Exemplary display of TEM imaging data of a reticular structure, UiO-66. The transmission image of the selected crystal (a) is accompanied by a further magnifications (b–c) of an highlighted area of (a), the diffraction pattern of the entire crystal with indexed reflections (d), and the FFT (e) of the high-resolution image shown in (b). Reproduced from ref (79) with permission from the Royal Society of Chemistry. (79)
Figure 6
Figure 6. Low-pressure Ar adsorption isotherm of IRMOF-74-IV at 87 K (a). (80) 65 adsorption data points (P/P0 from 1.3 × 10–5 to 0.99) and 15 desorption data points were collected. Five continual points at the P/P0 range from 7.85 × 10–2 to 1.73 × 10–1 were used for BET surface area calculation (b). The specific BET surface area of IRMOF-74-IV is 2516 m2 g–1, with a correlation coefficient R being 0.999967. The C constant in the BET equation is 19.345. Pore distribution profile of IRMOF-74-IV using the NLDFT model from the Ar adsorption data (P/P0 from 10–5 to 0.99) at 87 K (calculation model: Ar at 87 K zeolites/silica based on a cylindrical pore model; (c)). The fitting error between experimental isotherm and that based on NLDFT model is 0.819%.
Figure 7
Figure 7. Example of a MOF and a COF depicted in three building-up stages (specified in the section above). (101,109−111) The unit cell is highlighted in dashed gray lines. Only one of the interpenetrated networks of COF-300 is shown.
Figure 8
Figure 8. Structure of ZIF-8 (sod) is used to show how different graphical options can enhance clarity while highlighting the type of information that the figure aims to provide. (112,115) The unit cell is highlighted in dashed black lines.
References
ARTICLE SECTIONSThis article references 117 other publications.
- 1Introduction to Reticular Chemistry: Metal-Organic Frameworks and Covalent Organic Frameworks; Yaghi, O. M.; Kalmutzki, M. J.; Diercks, C. S. Wiley-VCH: Weinheim, 2019.
- 2Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Reticular synthesis and the design of new materials. Nature 2003, 423, 705– 714, DOI: 10.1038/nature01650[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXksV2itro%253D&md5=2417c5adb0e948350d3d62350c8cd7eaReticular synthesis and the design of new materialsYaghi, Omar M.; O'Keeffe, Michael; Ockwig, Nathan W.; Chae, Hee K.; Eddaoudi, Mohamed; Kim, JaheonNature (London, United Kingdom) (2003), 423 (6941), 705-714CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)A review. The long-standing challenge of designing and constructing new cryst. solid-state materials from mol. building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: the authors call this approach reticular synthesis. This chem. has yielded materials designed to have predetd. structures, compns. and properties. In particular, highly porous frameworks held together by strong metal-O-C bonds and with exceptionally large surface area and capacity for gas storage were prepd. and their pore metrics systematically varied and functionalized.
- 3Nimmermark, A.; Öhrström, L.; Reedijk, J. Metal-ligand Bond Lengths and Strengths: Are they Correlated? A detailed CSD Analysis. Z. Kristallogr. - Cryst. Mater. 2013, 228, 311– 317, DOI: 10.1524/zkri.2013.1605[Crossref], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmt1Wiu7s%253D&md5=5cdbba4e536174d76bf763551f531956Metal-ligand bond lengths and strengths: are they correlated? A detailed CSD analysisNimmermark, Anders; Oehrstroem, Lars; Reedijk, JanZeitschrift fuer Kristallographie - Crystalline Materials (2013), 228 (7), 311-317CODEN: ZKCMAJ; ISSN:2194-4946. (Oldenbourg Wissenschaftsverlag GmbH)Structure data on metal-alkoxides, metal-alc., metal-carboxylates, metal-carboxylic acid, metal-azolate and metal-azole coordination compds. from the Cambridge Structural Database (CSD) were analyzed in terms of bond lengths. In general the anionic ligands form shorter metal-ligand bonds by about 0.02-0.05 Å compared to neutral ligands, a clear indication of a charge contribution to the bonding interactions. This small difference is not, however, deemed as sufficient to generate two distinct classes of metal-ligand bonding. Instead, the anionic ligands can be viewed as having "charge assisted" metal-ligand bonding, corresponding to the same term used for "charge-assisted hydrogen bonding".
- 4Kinoshita, Y.; Matsubara, I.; Higuchi, T.; Saito, Y. The Crystal Structure of Bis(adiponitrilo)copper(I) Nitrate. Bull. Chem. Soc. Jpn. 1959, 32, 1221– 1226, DOI: 10.1246/bcsj.32.1221[Crossref], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF3cXovFKntg%253D%253D&md5=962ef78a85c6f22b54ea134d0da0f7ceThe crystal structure of bis(adiponitrilo)copper(I) nitrateKinoshita, Yukio; Matsubara, Ikuo; Hibuchi, Taiichi; Saito, YoshihikoBulletin of the Chemical Society of Japan (1959), 32 (), 1221-6CODEN: BCSJA8; ISSN:0009-2673.cf. preceding abstr. The crystal structure of bis(adiponitrilo)copper(I) nitrate was detd. by 2-dimensional Fourier methods. The cell is orthorhombic Pnnn, with 2 mols. per unit cell of dimensions: a = 9.41 ± 0.02, b = 13.73 ± 0.02, and c = 5.85 ± 0.01 A. A mean isotropic temp. factor with B = 3.0 sq. A. was applied for the 3 principal zones. Final values of R = .sum.‖F0| - |Fc‖/.sum.|F0| were 0.107, 0.116, and 0.112 for (hk0), (h0l), and (0kl), resp., with a weighted mean value of 0.110. The crystal consists of infinite 3-dimensional networks of complex ions, [Cu(NC-CH2-CH2-CH2-CH2CN)2]n+n, and nitrate ions. The Cu atom is tetrahedrally surrounded by 4 N atoms at a distance of 1.98 A. Each adiponitrile mol. is co.ovrddot.ordinated to 2 different Cu atoms forming a planar zigzag configuration of methylene groups. Thus, the Cu atoms and the ligand mols. form a complicated 3-dimensional 4-connected network. The nitrate ions are perpendicular to the a-axis, and seem to have statistical azimuthal orientations in the crystal and have apparent symmetry 222. All the atoms in the group Cu-N-C-C lie approx. on a straight line and the observed C-N distance is 1.13 A., suggesting that the bond character in the C-N group may be expressed by C≡N. C-C distances of 1.54, 1.50, and 1.53 A. were observed. The mechanism of cuprous-ion dyeing of polyacrylonitrile fibers is considered.
- 5Tomic, E. A. Thermal Stability of Coordination Polymers. J. Appl. Polym. Sci. 1965, 9, 3745– 3752, DOI: 10.1002/app.1965.070091121[Crossref], [CAS], Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF28XmtVeiug%253D%253D&md5=40097e0f519110a1902e9471abf89083Thermal stability of coordination polymersTomic, E. A.Journal of Applied Polymer Science (1965), 9 (11), 3745-52CODEN: JAPNAB; ISSN:0021-8995.Polymers insol. in conventional solvents were formed between 3 ligands (1,5-dihydroxynaphthalene-2,6-dicarboxylic acid (I), pyromellitic acid (II), and 2,3,6,7-naphthalenetetracarboxylic acid) and selected metal ions, Zn, Ni, Al, Fe3+, Th, and U. The thermal stability of these chelates in air above 300° was evaluated. The Zn salt of I was more stable than the Fe and Ni polymers. Thermal stability was a function of the metal involved. A higher thermal stability resulted when metals incapable of changing their ionic valency, e.g. Zn or Th, were used. The Fe salt of I had a max. wt. loss of 82.4% while the Zn salt lost only 75%. With II, there was 100% wt. loss at 290°, but only 29% loss with a II-U polymer. Polymers contg. metals capable of redox reactions, e.g. Ni and Fe, decompd., while the Zn salt of I merely lost H2O.
- 6Aumüller, A.; Erk, P.; Klebe, G.; Hünig, S.; von Schütz, J. U.; Werner, H.-P. A Radical Anion Salt of 2,5-Dimethyl-N,N′-dicyanoquinonediimine with Extremely High Electrical Conductivity. Angew. Chem., Int. Ed. Engl. 1986, 25, 740– 741, DOI: 10.1002/anie.198607401
- 7Hoskins, B. F.; Robson, R. Infinite Polymeric Frameworks Consisting of Three Dimensionally Linked Rod-like Segments. J. Am. Chem. Soc. 1989, 111, 5962– 5964, DOI: 10.1021/ja00197a079[ACS Full Text], [CAS], Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1MXks12rs7k%253D&md5=c1b3b761420baa7f79b0f58be519d396Infinite polymeric frameworks consisting of three dimensionally linked rod-like segmentsHoskins, Bernard F.; Robson, RichardJournal of the American Chemical Society (1989), 111 (15), 5962-4CODEN: JACSAT; ISSN:0002-7863.A new class of solids may be afforded by linking together tetrahedral or octahedral centers by rod-like connecting units. Substitution of the MeCN ligands in Cu(CH3CN)4BF4 by 4,4',4'',4'''-tetracyanotetraphenylmethane (L) has provided the 1st example of a deliberately designed framework of this type. The structure of CuLBF4.xPhNO2 was detd. by x-ray crystallog.; tetragonal I‾4m2, a 13.620(2), c 22.642(2) Å, Z = 2. The structure consists of an infinite, diamond-related, cationic framework of C[C6H4CN]Cu rods, which creates large adamantane-like voids of vol. approx. twice that of the framework itself. This material is unusual in that approx. 2/3 of the contents of what is undoubtedly a crystal are effectively liq., the large inter-framework spaces being occupied by disordered PhNO2 (≥7.7 C6H5NO2 per Cu) together with mobile BF4- ions. The solid undergoes ready anion exchange.
- 8Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K. Preparation, Clathration Ability, and Catalysis of a Two-Dimensional Square Network Material Composed of Cadmium(II) and 4,4’-Bipyridine. J. Am. Chem. Soc. 1994, 116, 1151– 1152, DOI: 10.1021/ja00082a055[ACS Full Text], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2cXhsVGnt78%253D&md5=5af3fcd83e3709797b79fe9c9d22d26dPreparation, Clathration Ability, and Catalysis of a Two-Dimensional Square Network Material Composed of Cadmium(II) and 4,4'-BipyridineFujita, Makoto; Kwon, Yoon Jung; Washizu, Satoru; Ogura, KatsuyukiJournal of the American Chemical Society (1994), 116 (3), 1151-2CODEN: JACSAT; ISSN:0002-7863.A two-dimensional square network material {[Cd(4,4'-bpy)2](NO3)2}∞ (1) (bpy = bipyridine) was prepd. from Cd(NO3)2 and 4,4'-bpy. Having inner cavities surrounded by 4,4'-bpy units as shown by crystallog. anal., this material behaved like inorg. porous materials such as zeolites. Thus, the complex 1 easily formed the clathrate complex {[Cd(4,4'-bpy)2](NO3)2·2G}∞ (2,G = o-C6H4X2 or C6H5X, X = Br, Cl) with some arom. compds. and exhibited heterogeneous catalysis for cyanosilyation of aldehydes. X-ray diffraction study of 2 (G = o-C6H4Br2) showed a layered array of the two-dimensional network.
- 9Subramanian, S.; Zaworotko, M. J. Porous Solids by Design: [Zn(4,4′-bpy)2(SiF6)]n·xDMF, a Single Framework Octahedral Coordination Polymer with Large Square Channels. Angew. Chem., Int. Ed. Engl. 1995, 34, 2127– 2129, DOI: 10.1002/anie.199521271[Crossref], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXovVelu7s%253D&md5=b45bb78a4e426c05f0c83ed815d2942bPorous solids by design: [Zn(4,4'-bpy)2(SiF6)]n·xDMF, a single framework octahedral coordination polymer with large square channelsSubramanian, S.; Zaworotko, Michael J.Angewandte Chemie, International Edition in English (1995), 34 (19), 2127-9CODEN: ACIEAY; ISSN:0570-0833. (VCH)[Zn(4,4'-bpy)2(SiF6)]n·xDMF (4,4'-bpy = 4,4'-bipyridine) was prepd. from [Zn(H2O)6]SiF6. Its crystal structure was detd. in space group P4/mmm (R = 0.063). The channel structure of the extended polymer is described and the compd. is suggested as a prototype for a range of porous octahedral structures.
- 10Kitagawa, S.; Kondo, M. Functional Micropore Chemistry of Crystalline Metal Complex-Assembled Compounds. Bull. Chem. Soc. Jpn. 1998, 71, 1739– 1753, DOI: 10.1246/bcsj.71.1739[Crossref], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXls1aitLo%253D&md5=28ab44fe04d3a8e344e5c760c7c2355dFunctional micropore chemistry of crystalline metal complex-assembled compoundsKitagawa, Susumu; Kondo, MitsuruBulletin of the Chemical Society of Japan (1998), 71 (8), 1739-1753CODEN: BCSJA8; ISSN:0009-2673. (Chemical Society of Japan)A review with 108 refs. Syntheses of new porous frameworks with specific pore size and type are of considerable interest for the appearance of zeolite-like functionalities. It is useful to take advantage of metal complex-assembled compds. because of designable frameworks, high microporosity, and flexible frameworks based on a variety of coordination geometries of metal centers and multifunctionality of bridging org. parts. Many recent reports show that the synthesis procedures are developing from serendipitous to rational level. Therefore, the micropore chem. of metal complex-based assemblages is directed toward not only new frameworks but also functionalities such as gas and small mol. adsorption, ion exchange, heterogeneous catalysis, photo-chem. and -phys. properties. For chem. and phys. functionalities robustness of a framework is required even in the absence of guest mols. in the cavity. The stability is largely dependent on the structural dimensionality of the assemblages. A wide variety of structures of metal complex-based assemblages are listed and recent findings in this functional chem. are described.
- 11Structural Inorganic Chemistry; Wells, A. F., Ed.; Oxford University Press: Oxford, 1984.Google ScholarThere is no corresponding record for this reference.
- 12Hoffmann, R. How Should Chemists Think?. Sci. Am. 1993, 268, 66– 73, DOI: 10.1038/scientificamerican0293-66
- 13Jiang, J.; Zhao, Y.; Yaghi, O. M. Covalent Chemistry beyond Molecules. J. Am. Chem. Soc. 2016, 138, 3255– 3265, DOI: 10.1021/jacs.5b10666[ACS Full Text], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XisVWmt7g%253D&md5=b8466d5f42b760f6bf06da3ea685562dCovalent Chemistry beyond MoleculesJiang, Juncong; Zhao, Yingbo; Yaghi, Omar M.Journal of the American Chemical Society (2016), 138 (10), 3255-3265CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A review. Linking mol. building units by covalent bonds to make cryst. extended structures has given rise to metal-org. frameworks (MOFs) and covalent org. frameworks (COFs), thus bringing the precision and versatility of covalent chem. beyond discrete mols. to extended structures. The key advance in this regard has been the development of strategies to overcome the "crystn. problem", which is usually encountered when attempting to link mol. building units into covalent solids. Currently, numerous MOFs and COFs are made as cryst. materials in which the large size of the constituent units provides for open frameworks. The mol. units thus reticulated become part of a new environment where they have (a) lower degrees of freedom because they are fixed into position within the framework; (b) well-defined spatial arrangements where their properties are influenced by the intricacies of the pores; and (c) ordered patterns onto which functional groups can be covalently attached to produce chem. complexity. The notion of covalent chem. beyond mols. is further strengthened by the fact that covalent reactions can be carried out on such frameworks, with full retention of their crystallinity and porosity. MOFs are exemplars of how this chem. has led to porosity with designed metrics and functionality, chem.-rich sequences of information within their frameworks, and well-defined mesoscopic constructs in which nanoMOFs enclose inorg. nanocrystals and give them new levels of spatial definition, stability, and functionality.
- 14Basic Inorganic Chemistry; Cotton, F. A.; Wilkinson, G.; Gaus, P. L., Eds.; Wiley-VCH: Weinheim, 1994.Google ScholarThere is no corresponding record for this reference.
- 15Organic Chemistry: Structure and Function; Vollhardt, P., Schore, N., Eds.; Freemann and Company, New York, NY, 2018.Google ScholarThere is no corresponding record for this reference.
- 16Yaghi, O. M.; Li, G.; Li, H. Selective Binding and Removal of Guests in a Microporous Metal–Organic Framework. Nature 1995, 378, 703– 706, DOI: 10.1038/378703a0[Crossref], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXhtVSnt7rP&md5=b0f48a6fa756cb3acc150b91b847516eSelective binding and removal of guests in a microporous metal-organic frameworkYaghi, O. M.; Li, Guangming; Li, HailianNature (London) (1995), 378 (6558), 703-6CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)Microporous inorg. materials such as zeolites find widespread application in heterogeneous catalysis, adsorption and ion-exchange processes. The rigidity and stability of such frameworks allow for shape- and size-selective inclusion of org. mols. and ions. Analogous microporous structures based on org. building blocks have the potential for more precise rational design, through control of the shape, size and functionalization of the pores. Here we report the synthesis of a metal-org. framework designed to bind arom. guest mols. selectively. The basic building block is a sym. org. mol., which binds metal ions to form layers of the metal-org. compd. alternating with layers whose compn. is detd. by the functionalization of the starting mols. The layers create channels in which guest arom. mols. may be selectively bound. We show that the crystal lattice thus formed is thermally stable up to 350°C, even after removal of included guest mols., and that the inclusions can be selectively readsorbed.
- 17Li, H.; Eddaoudi, M.; Groy, T. L.; Yaghi, O. M. Establishing Microporosity in Open Metal–Organic Frameworks: Gas Sorption Isotherms for Zn(BDC) (BDC = 1,4-Benzenedicarboxylate). J. Am. Chem. Soc. 1998, 120, 8571– 8572, DOI: 10.1021/ja981669x[ACS Full Text], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXltVegtrk%253D&md5=30587bcdce6035f7b29177de9452e8a3Establishing Microporosity in Open Metal-Organic Frameworks: Gas Sorption Isotherms for Zn(BDC) (BDC = 1,4-Benzenedicarboxylate)Li, Hailian; Eddaoudi, Mohamed; Groy, Thomas L.; Yaghi, O. M.Journal of the American Chemical Society (1998), 120 (33), 8571-8572CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Microporous metal-org. frameworks with pores accessible in a zeolite-like fashion were prepd. The synthesis, structural characterization, and gas sorption isotherm measurements for the Zn(BDC) microporous frameworks of cryst. Zn(BDC)·(DMF)(H2O) (BDC= 1,4-benzenedicarboxylate).
- 18Li, H.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Design and Synthesis of an Exceptionally Stable and Highly Porous Metal-Organic Framework. Nature 1999, 402, 276– 279, DOI: 10.1038/46248[Crossref], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXnvFSiuro%253D&md5=68f27e20a7e4e15ea2c2f49a2a61e98aDesign and synthesis of an exceptionally stable and highly porous metal-organic frameworkLi, Hailian; Eddaoudi, Mohamed; O'Keeffe, M.; Yaghi, M.Nature (London) (1999), 402 (6759), 276-279CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)Open metal-org. frameworks are widely regarded as promising materials for applications in catalysis, sepn., gas storage and mol. recognition. Compared to conventionally used microporous inorg. materials such as zeolites, these org. structures have the potential for more flexible rational design, through control of the architecture and functionalization of the pores. So far, the inability of these open frameworks to support permanent porosity and to avoid collapsing in the absence of guest mols., such as solvents, has hindered further progress in the field. The authors report the synthesis of a metal-org. framework, Zn4O(BDC)3.(DMF)8.(PhCl) (named MOF-5, where BDC = 1,4-benzenedicarboxylate), which remains cryst., as evidenced by x-ray single-crystal analyses, and stable when fully desolvated and when heated up to 300°. This synthesis is achieved by borrowing ideas from metal carboxylate cluster chem., where an org. dicarboxylate linker was used in a reaction that gives supertetrahedron clusters when capped with monocarboxylates. The rigid and divergent character of the added linker allows the articulation of the clusters into a three-dimensional framework resulting in a structure with higher apparent surface area and pore vol. than most porous cryst. zeolites. This simple and potentially universal design strategy is currently being pursued in the synthesis of new phases and composites, and for gas-storage applications.
- 19Chui, S. S.-Y.; Lo, S. M.-F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. A Chemically Functionalizable Nanoporous Material [Cu3(TMA)2(H2O)3]n. Science 1999, 283, 1148– 1150, DOI: 10.1126/science.283.5405.1148[Crossref], [PubMed], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXhsFeitLc%253D&md5=8f6f372b015fa0e2bbb7e8bfd316b663A chemically functionalizable nanoporous material [Cu3(TMA)2(H2O)3]nChui, Stephen S.-Y.; Lo, Samuel M.-F.; Charmant, Jonathan P. H.; Orpen, A. Guy; Williams, Ian D.Science (Washington, D. C.) (1999), 283 (5405), 1148-1150CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Although zeolites and related materials combine nanoporosity with high thermal stability, they are difficult to modify or derivatize in a systematic way. A highly porous metal coordination polymer [Cu3(TMA)2(H2O)3]n (TMA is benzene-1,3,5-tricarboxylate) was formed in 80% yield. It has interconnected [Cu2(O2CR)4] units (R is an arom. ring), which create a three-dimensional system of channels with a pore size of 1 nm and an accessible porosity of ∼40% in the solid. Unlike zeolites, the channel linings can be chem. functionalized; for example, the aqua ligands can be replaced by pyridines. TGA and high-temp. single-crystal diffractometry indicate that the framework is stable up to 240°.
- 20Cui, Y.; Evans, O. R.; Ngo, H. L.; White, P. S.; Lin, W. Rational Design of Homochiral Solids Based on Two-Dimensional Metal Carboxylates. Angew. Chem., Int. Ed. 2002, 41, 1159– 1162, DOI: 10.1002/1521-3773(20020402)41:7<1159::AID-ANIE1159>3.0.CO;2-5[Crossref], [CAS], Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XivVykt7o%253D&md5=b573002d44007cf995760a35be95734bRational design of homochiral solids based on two-dimensional metal carboxylatesCui, Yong; Evans, Owen R.; Ngo, Helen L.; White, Peter S.; Lin, WenbinAngewandte Chemie, International Edition (2002), 41 (7), 1159-1162CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)A chiral two-dimensional network is the basis for the structure of a homochiral solid exploiting metal-carboxylate coordination. The synthesis involved enantiopure bridging ligands and metal-org. secondary building units, and resulted in ethoxy-protected BINOL functionalities pointing into the cavities in this cryst. chiral zeolitic material. The cobalt, manganese and nickel-derived complexes of (1S)-6,6'-dichloro-2,2'-diethoxy-1,1'-binaphthalene-4,4'-dicarboxylic acid were reported. The cobalt-derived complex of (1R)-6,6'-dichloro-2,2'-diethoxy-1,1'-binaphthalene-4,4'-dicarboxylic acid was also reported; using either the (1S)-isomer or the (1R)-isomer, supramol. enantiomers were obtained.
- 21Dinca, M.; Yu, A. F.; Long, J. R. Microporous Metal–Organic Frameworks Incorporating 1,4-Benzeneditetrazolate: Syntheses, Structures, and Hydrogen Storage Properties. J. Am. Chem. Soc. 2006, 128, 8904– 8913, DOI: 10.1021/ja061716i[ACS Full Text], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XmtVSjtLg%253D&md5=c33a3b55e4ff31ac354ecbdd5b636120Microporous Metal-Organic Frameworks Incorporating 1,4-Benzeneditetrazolate: Syntheses, Structures, and Hydrogen Storage PropertiesDinca, Mircea; Yu, Anta F.; Long, Jeffrey R.Journal of the American Chemical Society (2006), 128 (27), 8904-8913CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The potential of tetrazolate-based ligands for forming metal-org. frameworks of utility in hydrogen storage is demonstrated using 1,4-benzeneditetrazolate (BDT2-) to generate robust, microporous materials. Reaction of H2BDT with MnCl2·4H2O and Mn(NO3)2·4H2O in N,N-diethylformamide (DEF) produces the two-dimensional framework solids Mn3(BDT)2Cl2(DEF)6 (1) and Mn4(BDT)3(NO3)2(DEF)6 (2), whereas reactions with hydrated salts of Mn2+, Cu2+, and Zn2+ in a mixt. of methanol and DMF afford the porous, three-dimensional framework solids Zn3(BDT)3(DMF)4(H2O)2·3.5CH3OH (3), Mn3(BDT)3(DMF)4(H2O)2·3CH3OH·2H2O·DMF (4), Mn2(BDT)Cl2(DMF)2·1.5CH3OH·H2O (5), and Cu(BDT)(DMF)·CH3OH·0.25DMF (6). The method for desolvating such compds. can dramatically influence the ensuing gas sorption properties. When subjected to a mild evacuation procedure, compds. 3-6 exhibit permanent porosity, with BET surface areas in the range 200-640 m2/g. The desolvated forms of 3-5 store between 0.82 and 1.46% H2 at 77 K and 1 atm, with enthalpies of adsorption in the range 6.0-8.8 kJ/mol, among the highest so far reported for metal-org. frameworks. The desolvated form of 6 exhibits preferential adsorption of O2 over H2 and N2, showing promise for gas sepn. and purifn. applications.
- 22Jia, J.; Lin, X.; Wilson, C.; Blake, A. J.; Champness, N. R.; Hubberstey, P.; Walker, G.; Cussen, E. J.; Schröder, M. Twelve-connected Porous Metal-Organic Frameworks With High H2 Adsorption. Chem. Commun. 2007, 28, 840– 842, DOI: 10.1039/B614254K
- 23An, J.; Geib, S. J.; Rosi, N. L. Cation-triggered Drug Release from a Porous Zinc–Adeninate Metal–Organic Framework. J. Am. Chem. Soc. 2009, 131, 8376– 8377, DOI: 10.1021/ja902972w[ACS Full Text], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXms1Kntbw%253D&md5=e7c5bc9294614369af1be7c69a7198d5Cation-Triggered Drug Release from a Porous Zinc-Adeninate Metal-Organic FrameworkAn, Jihyun; Geib, Steven J.; Rosi, Nathaniel L.Journal of the American Chemical Society (2009), 131 (24), 8376-8377CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A porous anionic metal-org. framework, {[Zn8(ad)4(BPDC)6O]·8DMF·11H2O}n (bio-MOF-1; Had = adenine, H2BPDC = biphenyl-4,4'-dicarboxylic acid), constructed using adenine as a biomol. building block is described. The porosity of this material is evaluated, its stability in biol. buffers is studied, and its potential as a material for controlled drug release is investigated. Specifically, procainamide HCl is loaded into the pores of bio-MOF-1 using a simple cation exchange process. Exogenous cations from biol. buffers are shown to affect the release of the adsorbed drug mols.
- 24Zacher, D.; Shekhah, O.; Wöll, C.; Fischer, R. A. Thin Films of Metal–Organic Frameworks. Chem. Soc. Rev. 2009, 38, 1418– 1429, DOI: 10.1039/b805038b[Crossref], [PubMed], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXkvVamu7g%253D&md5=59eb12bf16cf57126492a7e6b38baf9aThin films of metal-organic frameworksZacher, Denise; Shekhah, Osama; Woell, Christof; Fischer, Roland A.Chemical Society Reviews (2009), 38 (5), 1418-1429CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The fabrication of thin film coatings of metal-org. frameworks (MOFs) on various substrates is discussed in this crit. review. Interestingly, the relatively few studies on MOF films that have appeared in the literature are limited to the following cases: [Zn4O(bdc)3] (MOF-5; bdc = 1,4-benzenedicarboxylate), [Cu3(btc)2] (HKUST-1; btc = 1,3,5-benzenetricarboxylate), [Zn2(bdc)2(dabco)] (dabco = 1,4-diazabicyclo[2.2.2]octane), [Mn(HCOO)], [Cu2(pzdc)2(pyz)] (CPL-1; pzdc = pyrazine-2,3-dicarboxylate, pyz = pyrazine), [Fe(OH)(bdc)] (MIL-53(Fe)) and [Fe3O(bdc)3(Ac)] (MIL-88B; Ac = CH3COO-). Various substrates and support materials have been used, including silica, porous alumina, graphite and org. surfaces, i.e. self-assembled monolayers (SAMs) on gold, as well as silica surfaces. Most of the MOF films were grown by immersion of the selected substrates into specifically pre-treated solvothermal mother liquors of the particular MOF material. This results in more or less densely packed films of intergrown primary crystallites of sizes ranging up to several μm, leading to corresponding film thicknesses. Alternatively, almost atomically flat and very homogeneous films, with thicknesses of up to ca. 100 nm, were grown in a novel stepwise layer-by-layer method. The individual growth steps are sepd. by removing unreacted components via rinsing the substrate with the solvent. The layer-by-layer method offers the possibility to study the kinetics of film formation in more detail using surface plasmon resonance. In some cases, particularly on SAM-modified substrates, a highly oriented growth was obsd., and in the case of the MIL-53/MIL-88B system, a phase selective deposition of MIL-88B, rather than MIL-53(Fe), was reported. The growth of MOF thin films is important for smart membranes, catalytic coatings, chem. sensors and related nanodevices (63 refs.).
- 25Sun, L.; Campbell, M. G.; Dincǎ, M. Electrically Conductive Porous Metal–Organic Frameworks. Angew. Chem., Int. Ed. 2016, 55, 3566– 3579, DOI: 10.1002/anie.201506219[Crossref], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XmslGisw%253D%253D&md5=185401e793b619c797286fe8df7c641eElectrically Conductive Porous Metal-Organic FrameworksSun, Lei; Campbell, Michael G.; Dinca, MirceaAngewandte Chemie, International Edition (2016), 55 (11), 3566-3579CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Owing to their outstanding structural, chem., and functional diversity, metal-org. frameworks (MOFs) have attracted considerable attention over the last two decades in a variety of energy-related applications. Notably missing among these, until recently, were applications that required good charge transport coexisting with porosity and high surface area. Although most MOFs are elec. insulators, several materials in this class have recently demonstrated excellent elec. cond. and high charge mobility. Herein, the authors review the synthetic and electronic design strategies that have been employed thus far for producing frameworks with permanent porosity and long-range charge transport properties. In addn., key expts. that have been employed to demonstrate elec. transport, as well as selected applications for this subclass of MOFs, are discussed.
- 26Côté, A. P.; Benin, A. I.; Ockwig, N. W.; O’Keeffe, M.; Matzger, A. J.; Yaghi, O. M. Porous, Crystalline, Covalent Organic Frameworks. Science 2005, 310, 1166– 1170, DOI: 10.1126/science.1120411[Crossref], [PubMed], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1WgtLnF&md5=e2e033fd4af37870fc73cbb18c1eaed1Porous, Crystalline, Covalent Organic FrameworksCote, Adrien P.; Benin, Annabelle I.; Ockwig, Nathan W.; O'Keeffe, Michael; Matzger, Adam J.; Yaghi, Omar M.Science (Washington, DC, United States) (2005), 310 (5751), 1166-1170CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Covalent org. frameworks (COFs) have been designed and successfully synthesized by condensation reactions of Ph diboronic acid {C6H4[B(OH)2]2} and hexahydroxytriphenylene [C18H6(OH)6]. Powder x-ray diffraction studies of the highly cryst. products (C3H2BO)6•(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P63/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temps. up to 500° to 600°C), permanent porosity, and high surface areas (711 and 1590 square meters per g, resp.).
- 27El-Kaderi, H. M.; Hunt, J. R.; Mendoza-Cortés, J. L.; Côté, A. P.; Taylor, R. E.; O’Keeffe, M.; Yaghi, O. M. Designed Synthesis of 3D Covalent Organic Frameworks. Science 2007, 316, 268– 272, DOI: 10.1126/science.1139915[Crossref], [PubMed], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXktVektbs%253D&md5=4197db9769708ec596162efd126cdca9Designed Synthesis of 3D Covalent Organic FrameworksEl-Kaderi, Hani M.; Hunt, Joseph R.; Mendoza-Cortes, Jose L.; Cote, Adrien P.; Taylor, Robert E.; O'Keeffe, Michael; Yaghi, Omar M.Science (Washington, DC, United States) (2007), 316 (5822), 268-272CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Three-dimensional covalent org. frameworks (3D COFs) were synthesized by targeting two nets based on triangular and tetrahedral nodes: ctn and bor. The resp. 3D COFs were synthesized as cryst. solids by condensation reactions of tetrahedral tetra(4-dihydroxyborylphenyl)methane or tetra(4-dihydroxyborylphenyl)silane and by co-condensation of triangular 2,3,6,7,10,11-hexahydroxytriphenylene. Because these materials are entirely constructed from strong covalent bonds (C-C, C-O, C-B, and B-O), they have high thermal stabilities (400° to 500 °C), and they also have high surface areas (3472 and 4210 square meters per g for COF-102 and COF-103, resp.) and extremely low densities (0.17 g per cubic centimeter).
- 28Wan, S.; Guo, J.; Kim, J.; Ihee, H.; Jiang, D. A Belt-shaped, Blue Luminescent, and Semiconducting Covalent Organic Framework. Angew. Chem., Int. Ed. 2008, 47, 8826– 8830, DOI: 10.1002/anie.200803826[Crossref], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsVCgtLbO&md5=30837c9b478fe26320304d7edcf7e267A belt-shaped, blue luminescent, and semiconducting covalent organic frameworkWan, Shun; Guo, Jia; Kim, Jangbae; Ihee, Hyotcherl; Jiang, DonglinAngewandte Chemie, International Edition (2008), 47 (46), 8826-8830CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Blue belt: Condensation polymn. of pyrene (blue) and triphenylene (green) monomers leads to the formation of a hexagonal mesoporous covalent org. framework. This material exists in a belt shape, absorbs photons over a wide wavelength range to emit them as blue luminescence, and is semiconducting, as well as being capable of repetitive on-off switching.
- 29Spitler, E. L.; Dichtel, W. R. Lewis Acid-catalysed Formation of Two-dimensional Phthalocyanine Covalent Organic Frameworks. Nat. Chem. 2010, 2, 672– 677, DOI: 10.1038/nchem.695[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpt1aksbY%253D&md5=cbb7ec00f7dbefa96c9521b7b80576f4Lewis acid-catalysed formation of two-dimensional phthalocyanine covalent organic frameworksSpitler, Eric L.; Dichtel, William R.Nature Chemistry (2010), 2 (8), 672-677CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Covalent org. frameworks (COFs) offer a new strategy for assembling org. semiconductors into robust networks with at. precision and long-range order. General methods for COF synthesis will allow complex building blocks to be incorporated into these emerging materials. Here we report a new Lewis acid-catalyzed protocol to form boronate esters directly from protected catechols and arylboronic acids. This transformation also provides cryst. boronate ester-linked COFs from protected polyfunctional catechols and bis(boronic acids). Using this method, we prepd. a new COF that features a square lattice composed of phthalocyanine macrocycles joined by phenylene bis(boronic acid) linkers. The phthalocyanines stack in an eclipsed fashion within the COF to form 2.3 nm pores that run parallel to the stacked chromophores. The material's broad absorbance over the solar spectrum, potential for efficient charge transport through the stacked phthalocyanines, good thermal stability and the modular nature of COF synthesis, show strong promise for applications in org. photovoltaic devices.
- 30Dogru, M.; Sonnauer, A.; Gavryushin, A.; Knochel, P.; Bein, T. A Covalent Organic Framework with 4 nm Open Pores. Chem. Commun. 2011, 47, 1707– 1709, DOI: 10.1039/c0cc03792c[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXht1WhtLw%253D&md5=14d4321cc0a17da6c766f2b1cba39b4cA covalent organic framework with 4 nm open poresDogru, Mirjam; Sonnauer, Andreas; Gavryushin, Andrei; Knochel, Paul; Bein, ThomasChemical Communications (Cambridge, United Kingdom) (2011), 47 (6), 1707-1709CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)The synthesis and characterization of a new mesoporous covalent org. framework BTP-COF is described, the latter having fully accessible pores with an open diam. of 4.0 nm.
- 31Lehn, J.-M. Supramolecular Chemistry—Scope and Perspectives Molecules, Supermolecules, and Molecular Devices (Nobel Lecture). Angew. Chem., Int. Ed. Engl. 1988, 27, 89– 112, DOI: 10.1002/anie.198800891
- 32Cohen, S. M. The Postsynthetic Renaissance in Porous Solids. J. Am. Chem. Soc. 2017, 139, 2855– 2863, DOI: 10.1021/jacs.6b11259[ACS Full Text], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFajtro%253D&md5=0f92baffa318d7117f1d557f1cb16b3eThe Postsynthetic Renaissance in Porous SolidsCohen, Seth M.Journal of the American Chemical Society (2017), 139 (8), 2855-2863CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A review. Metal-org. frameworks (MOFs) have rapidly grown into a major area of chem. research over the last two decades. MOFs represent the development of covalent chem. "beyond the mol." and into extended structures. MOFs also present an unprecedented scaffold for performing heterogeneous org. transformations in the solid state, allowing for deliberate and precise prepn. of new materials. The development of these transformations has given rise to the "postsynthetic renaissance", a suite of methods by which these materials can be transformed in a single-crystal-to-single-crystal manner. Postsynthetic modification, postsynthetic deprotection, postsynthetic exchange, postsynthetic insertion, and postsynthetic polymn. have exploited the unique features of both the org. and inorg. components of MOFs to create cryst., porous solids of unique complexity and functionality.
- 33Czaja, A. U.; Trukhan, N.; Müller, U. Industrial Applications of Metal–Organic Frameworks. Chem. Soc. Rev. 2009, 38, 1284– 1293, DOI: 10.1039/b804680h[Crossref], [PubMed], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXkvVamu7o%253D&md5=63295ce7e2fb393c1abecd7623bc9c58Industrial applications of metal-organic frameworksCzaja, Alexander U.; Trukhan, Natalia; Muller, UlrichChemical Society Reviews (2009), 38 (5), 1284-1293CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. New materials are prerequisite for major breakthrough applications affecting the daily life, and therefore are pivotal for the chem. industry. Metal-org. frameworks (MOFs) constitute an emerging class of materials useful in gas storage, gas purifn., and sepn. applications as well as heterogeneous catalysis. They not only offer higher surface areas and the potential for enhanced activity than currently used materials like base metal oxides, but also provide shape/size selectivity which is important both for sepns. and catalysis. In this crit. review an overview of the potential applications of MOFs in the chem. industry is presented. Furthermore, the synthesis and characterization of the materials are briefly discussed from the industrial perspective.
- 34Kim, H.; Yang, S.; Rao, S. R.; Narayanan, S.; Kapustin, E. A.; Furukawa, H.; Umans, A. S.; Yaghi, O. M.; Wang, E. N. Water Harvesting from Air with Metal-Organic Frameworks Powered by Natural Sunlight. Science 2017, 356, 430– 434, DOI: 10.1126/science.aam8743[Crossref], [PubMed], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXmvFejtLo%253D&md5=14666dd987441772addcc6bf9c70b02aWater harvesting from air with metal-organic frameworks powered by natural sunlightKim, Hyunho; Yang, Sungwoo; Rao, Sameer R.; Narayanan, Shankar; Kapustin, Eugene A.; Furukawa, Hiroyasu; Umans, Ari S.; Yaghi, Omar M.; Wang, Evelyn N.Science (Washington, DC, United States) (2017), 356 (6336), 430-434CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Atm. water is a resource equiv. to -10% of all fresh water in lakes on Earth. However, an efficient process for capturing and delivering water from air, esp. at low humidity levels (down to 20%), has not been developed. We report the design and demonstration of a device based on a porous metal-org. framework {M0F-801, [Zr604(0H)4(fumarate)6]} that captures water from the atm. at ambient conditions by using low-grade heat from natural sunlight at a flux of less than 1 sun (1 kW per square meter). This device is capable of harvesting 2.8 L of water per kg of MOF daily at relative humidity levels as low as 20% and requires no addnl. input of energy.
- 35Fathieh, F.; Kalmutzki, M. J.; Kapustin, E. A.; Waller, P. J.; Yang, J.; Yaghi, O. M. Practical Water Production from Desert Air. Sci. Adv. 2018, 4, eaat3198, DOI: 10.1126/sciadv.aat3198
- 36Hanikel, N.; Prévot, M. S.; Fathieh, F.; Kapustin, E. A.; Lyu, H.; Wang, H.; Diercks, N. J.; Glover, T. G.; Yaghi, O. M. Rapid Cycling and Exceptional Yield in a Metal-Organic Framework Water Harvester. ACS Cent. Sci. 2019, 5, 1699– 1706, DOI: 10.1021/acscentsci.9b00745[ACS Full Text], [CAS], Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1ersr%252FP&md5=438f12344a29096e3d34f2774cb9be74Rapid Cycling and Exceptional Yield in a Metal-Organic Framework Water HarvesterHanikel, Nikita; Prevot, Mathieu S.; Fathieh, Farhad; Kapustin, Eugene A.; Lyu, Hao; Wang, Haoze; Diercks, Nicolas J.; Glover, T. Grant; Yaghi, Omar M.ACS Central Science (2019), 5 (10), 1699-1706CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)Sorbent-assisted water harvesting from air represents an attractive way to address water scarcity in arid climates. Hitherto, sorbents developed for this technol. have exclusively been designed to perform one water harvesting cycle (WHC) per day, but the productivities attained with this approach cannot reasonably meet the rising demand for drinking water. This work shows that a microporous aluminum-based metal-org. framework, MOF-303, can perform an adsorption-desorption cycle within minutes under a mild temp. swing, which opens the way for high-productivity water harvesting through rapid, continuous WHCs. Addnl., the favorable dynamic water sorption properties of MOF-303 allow it to outperform other com. sorbents displaying excellent steady-state characteristics under similar exptl. conditions. Finally, these findings are implemented in a new water harvester capable of generating 1.3 L kgMOF-1 day-1 in an indoor arid environment (32% relative humidity, 27°C) and 0.7 L kgMOF-1 day-1 in the Mojave Desert (in conditions as extreme as 10% RH, 27°C), representing an improvement by 1 order of magnitude over previously reported devices. This study demonstrates that creating sorbents capable of rapid water sorption dynamics, rather than merely focusing on high water capacities, is crucial to reach water prodn. on a scale matching human consumption.
- 37Hanikel, N.; Prévot, M. S.; Yaghi, O. M. MOF Water Harvesters. Nat. Nanotechnol. 2020, 15, 348– 355, DOI: 10.1038/s41565-020-0673-x[Crossref], [PubMed], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXosFSlsL0%253D&md5=4b44b62ea400c397b047bdf69fd9cb6cMOF water harvestersHanikel, Nikita; Prevot, Mathieu S.; Yaghi, Omar M.Nature Nanotechnology (2020), 15 (5), 348-355CODEN: NNAABX; ISSN:1748-3387. (Nature Research)A review. The advancement of addnl. methods for freshwater generation is imperative to effectively address the global water shortage crisis. In this regard, extn. of the ubiquitous atm. moisture is a powerful strategy allowing for decentralized access to potable water. The energy requirements as well as the temporal and spatial restrictions of this approach can be substantially reduced if an appropriate sorbent is integrated in the atm. water generator. Recently, metal-org. frameworks (MOFs) have been successfully employed as sorbents to harvest water from air, making atm. water generation viable even in desert environments. Herein, the latest progress in the development of MOFs capable of extg. water from air and the design of atm. water harvesters deploying such MOFs are reviewed. Furthermore, future directions for this emerging field, encompassing both material and device improvements, are outlined.
- 38Purification of Laboratory Chemicals; Armarego, W. L. F., Perrin, D. D., Eds.; Butterworth-Heinemann: Woburn, MA, 2000.Google ScholarThere is no corresponding record for this reference.
- 39Bennett, T. D.; Cheetham, A. K. Amorphous Metal–Organic Frameworks. Acc. Chem. Res. 2014, 47, 1555– 1562, DOI: 10.1021/ar5000314[ACS Full Text], [CAS], Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXls12hsb0%253D&md5=411be02fc16485bcb9b5163c6b260cb0Amorphous Metal-Organic FrameworksBennett, Thomas D.; Cheetham, Anthony K.Accounts of Chemical Research (2014), 47 (5), 1555-1562CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. The prepn. of amorphous metal-org. frameworks (aMOFs) by introduction of disorder into their parent cryst. frameworks through heating, pressure (both hydrostatic and nonhydrostatic), and ball-milling is described. The main method of characterizing these amorphous materials (anal. of the pair distribution function) is summarized, alongside complementary techniques such as Raman spectroscopy. Detailed investigations into their properties (both chem. and mech.) are compiled and compared with those of cryst. MOFs, while the impact of the field on the processing techniques used for cryst. MOF powders is also assessed. The benefits amorphization may bring to existing proposed MOF applications are detailed, alongside the possibilities and research directions afforded by the combination of the unique properties of the amorphous domain with the versatility of MOF chem.
- 40Thornton, A. W.; Jelfs, K. E.; Konstas, K.; Doherty, C. M.; Hill, A. J.; Cheetham, A. K.; Bennett, T. D. Porosity in Metal–Organic Framework Glasses. Chem. Commun. 2016, 52, 3750– 3753, DOI: 10.1039/C5CC10072K[Crossref], [PubMed], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XoslWqtg%253D%253D&md5=1ec6c1023cf8026913a629e4b74a3c34Porosity in metal-organic framework glassesThornton, A. W.; Jelfs, K. E.; Konstas, K.; Doherty, C. M.; Hill, A. J.; Cheetham, A. K.; Bennett, T. D.Chemical Communications (Cambridge, United Kingdom) (2016), 52 (19), 3750-3753CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)The porosity of a glass formed by melt-quenching a metal-org. framework, has been characterized by positron annihilation lifetime spectroscopy. The results reveal porosity intermediate between the related open and dense cryst. frameworks ZIF-4 and ZIF-zni. A structural model for the glass was constructed using an amorphous polymn. algorithm, providing addnl. insight into the gas-inaccessible nature of porosity and the possible applications of hybrid glasses.
- 41Zhao, Y.; Lee, S.-Y.; Becknell, N.; Yaghi, O. M.; Angell, C. A. Nanoporous Transparent MOF Glasses with Accessible Internal Surface. J. Am. Chem. Soc. 2016, 138, 10818– 10821, DOI: 10.1021/jacs.6b07078[ACS Full Text], [CAS], Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlOgt77J&md5=b4deb1aa2357800d28bc790607b55f87Nanoporous Transparent MOF Glasses with Accessible Internal SurfaceZhao, Yingbo; Lee, Seung-Yul; Becknell, Nigel; Yaghi, Omar M.; Angell, C. AustenJournal of the American Chemical Society (2016), 138 (34), 10818-10821CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)While glassy materials can be made from virtually every class of liq. (metallic, mol., covalent, and ionic), to date, formation of glasses in which structural units impart porosity on the nanoscopic level remains undeveloped. In view of the well-established porosity of metal-org. frameworks (MOFs) and the flexibility of their design, we have sought to combine their formation principles with the general versatility of glassy materials. Although the prepn. of glassy MOFs can be achieved by amorphization of cryst. frameworks, transparent glassy MOFs exhibiting permanent porosity accessible to gases are yet to be reported. Here, we present a generalizable chem. strategy for making such MOF glasses by assembly from viscous solns. of metal node and org. strut and subsequent evapn. of a plasticizer-modulator solvent. This process yields glasses with 300 m2/g internal surface area (obtained from N2 adsorption isotherms) and a 2 nm pore-pore sepn. On a volumetric basis, this porosity (0.33 cm3/cm3) is 3 times that of the early MOFs (0.11 cm3/cm3 for MOF-2) and within range of the most porous MOFs known (0.60 cm3/cm3 for MOF-5). We believe the porosity originates from a 3D covalent network as evidenced by the disappearance of the glass transition signature as the solvent is removed and the highly cross-linked nanostructure builds up. Our work represents an important step forward in translating the versatility and porosity of MOFs to glassy materials.
- 42Banerjee, R.; Phan, A.; Wang, B.; Knobler, C.; Furukawa, H.; O’Keeffe, M.; Yaghi, O. M. High-Throughput Synthesis of Zeolitic Imidazolate Frameworks and Application to CO2 Capture. Science 2008, 319, 939– 943, DOI: 10.1126/science.1152516[Crossref], [PubMed], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhslOmtr8%253D&md5=5db725852aeb4ca63bea1883fecb0c77High-Throughput Synthesis of Zeolitic Imidazolate Frameworks and Application to CO2 CaptureBanerjee, Rahul; Phan, Anh; Wang, Bo; Knobler, Carolyn; Furukawa, Hiroyasu; O'Keeffe, Michael; Yaghi, Omar M.Science (Washington, DC, United States) (2008), 319 (5865), 939-943CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A high-throughput protocol was developed for the synthesis of zeolitic imidazolate frameworks (ZIFs). Twenty-five different ZIF crystals were synthesized from only 9600 microreactions of either Zn(II)/Co(II) and imidazolate/imidazolate-type linkers. All of the ZIF structures have tetrahedral frameworks: 10 of which have two different links (heterolinks), 16 of which are previously unobserved compns. and structures, and 5 of which have topologies as yet unobserved in zeolites. Members of a selection of these ZIFs (termed ZIF-68, ZIF-69, and ZIF-70) have high thermal stability (up to 390°) and chem. stability in refluxing org. and aq. media. Their frameworks have high porosity (with surface areas up to 1970 square meters per g), and they exhibit unusual selectivity for CO2 capture from CO2/CO mixts. and extraordinary capacity for storing CO2: 1 L of ZIF-69 can hold ∼83 L of CO2 at 273 K under ambient pressure.
- 43Wilmer, E. C.; Leaf, M.; Lee, C. Y.; Farha, O. K.; Hauser, B. G.; Hupp, J. T.; Snurr, R. Q. Large-scale screening of hypothetical metal–organic frameworks. Nat. Chem. 2012, 4, 83– 89, DOI: 10.1038/nchem.1192[Crossref], [CAS], Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVagtL3K&md5=3becbfed2fdacdb8b58146666da7c038Large-scale screening of hypothetical metal-organic frameworksWilmer, Christopher E.; Leaf, Michael; Lee, Chang Yeon; Farha, Omar K.; Hauser, Brad G.; Hupp, Joseph T.; Snurr, Randall Q.Nature Chemistry (2012), 4 (2), 83-89CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Metal-org. frameworks (MOFs) are porous materials constructed from modular mol. building blocks, typically metal clusters and org. linkers. These can, in principle, be assembled to form an almost unlimited no. of MOFs, yet materials reported to date represent only a tiny fraction of the possible combinations. Here, the authors demonstrate a computational approach to generate all conceivable MOFs from a given chem. library of building blocks (based on the structures of known MOFs) and rapidly screen them to find the best candidates for a specific application. From a library of 102 building blocks the authors generated 137,953 hypothetical MOFs and for each calcd. the pore-size distribution, surface area and methane-storage capacity. The authors identified over 300 MOFs with a predicted methane-storage capacity better than that of any known material, and this approach also revealed structure-property relations. Methyl-functionalized MOFs were frequently top performers, so the authors selected one such promising MOF and exptl. confirmed its predicted capacity.
- 44Nelson, A. P.; Farha, O. K.; Mulfort, K. L.; Hupp, J. T. Supercritical Processing as a Route to High Internal Surface Areas and Permanent Microporosity in Metal–Organic Framework Materials. J. Am. Chem. Soc. 2009, 131, 458– 460, DOI: 10.1021/ja808853q[ACS Full Text], [CAS], Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsFChsb3J&md5=dc9e4bf4e41d4f8d15af0510be0261aaSupercritical Processing as a Route to High Internal Surface Areas and Permanent Microporosity in Metal-Organic Framework MaterialsNelson, Andrew P.; Farha, Omar K.; Mulfort, Karen L.; Hupp, Joseph T.Journal of the American Chemical Society (2009), 131 (2), 458-460CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Careful processing of 4 representative metal-org. framework (MOF) materials with liq. and supercrit. CO2 (ScD) leads to substantial, or in some cases spectacular (up to 1200%), increases in gas-accessible surface area. Maximization of surface area is key to the optimization of MOFs for many potential applications. Preliminary evidence points to inhibition of mesopore collapse, and therefore micropore accessibility, as the basis for the extraordinarily efficacious outcome of ScD-based activation. The crystals of the MOF including naphthalenedimide-contg. ligand are P2(1)/c, with a 23.275(4), b 25.486(4), c 49.521(7) Å, β 117.409(6)°; Z = 4, dc = 0.559; R1 = 0.0692, wR2 = 0.1513.
- 45Mondloch, J. E.; Karagiaridi, O.; Farha, O. K.; Hupp, J. T. Activation of metal–organic framework materials. CrystEngComm 2013, 15, 9258– 9264, DOI: 10.1039/c3ce41232f[Crossref], [CAS], Google Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs12mu7nI&md5=ab1fc6e3417f714af99db2c82f46101eActivation of metal-organic framework materialsMondloch, Joseph E.; Karagiaridi, Olga; Farha, Omar K.; Hupp, Joseph T.CrystEngComm (2013), 15 (45), 9258-9264CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)Cryst. metal-org. frameworks (MOFs) have emerged as a highly desirable class of solid-state materials. Some of their most attractive features include exceptionally high porosities as well as surface areas. A key aspect to the realization of high porosity is the removal of guest mols. from the framework while still maintaining its structural integrity (i.e., "activation"). This contribution highlights the strategies utilized to date for activating MOFs, including: (i) conventional heating and vacuum; (ii) solvent-exchange; (iii) supercrit. CO2 (scCO2) exchange; (iv) freeze-drying; and (v) chem. treatment.
- 46Howarth, A. J.; Peters, A. W.; Vermeulen, N. A.; Wang, T. C.; Hupp, J. T.; Farha, O. K. Best Practices for the Synthesis, Activation, and Characterization of Metal–Organic Frameworks. Chem. Mater. 2017, 29, 26– 39, DOI: 10.1021/acs.chemmater.6b02626[ACS Full Text], [CAS], Google Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFait7nM&md5=d12a6d43e44dd8b441ae14bfd973c6f4Best Practices for the Synthesis, Activation, and Characterization of Metal-Organic FrameworksHowarth, Ashlee J.; Peters, Aaron W.; Vermeulen, Nicolaas A.; Wang, Timothy C.; Hupp, Joseph T.; Farha, Omar K.Chemistry of Materials (2017), 29 (1), 26-39CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)A review. Metal-org. frameworks (MOFs) are structurally diverse materials comprised of inorg. and org. components. As the rapidly expanding field of MOF research demonstrated, these materials are being explored for a wide variety of potential applications. In this tutorial review, the authors give an overview of the current best practices assocd. with the synthesis, activation and characterization of MOFs. Methods described include supercrit. CO2 activation, single crystal XRD, powder X-ray diffraction (PXRD), N adsorption/desorption isotherms, surface area calcns., aq. stability tests, SEM, inductively coupled plasma optical emission spectroscopy (ICP-OES), NMR spectroscopy (NMR), and diffuse reflectance IR Fourier transform spectroscopy (DRIFTS). A variety of different MOFs are presented to aid in the discussion of relevant techniques. Some sections are accompanied by instructional videos to give further insight into the techniques, including tips/tricks/suggestions only those at the bench could describe.
- 47Serre, C.; Millange, F.; Thouvenot, C.; Noguès, M.; Marsolier, G.; Louër, D.; Férey, G. Very Large Breathing Effect in the First Nanoporous Chromium(III)-Based Solids: MIL-53 or CrIII(OH)·{O2C–C6H4–CO2}·{HO2C–C6H4–CO2H}x·H2Oy. J. Am. Chem. Soc. 2002, 124, 13519– 13526, DOI: 10.1021/ja0276974[ACS Full Text], [CAS], Google Scholar47https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XotVegt74%253D&md5=59fd68d1cae2399f56196e58039d3bd5Very Large Breathing Effect in the First Nanoporous Chromium(III)-Based Solids: MIL-53 or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}x·H2OySerre, Christian; Millange, Franck; Thouvenot, Christelle; Nogues, Marc; Marsolier, Gerard; Loueer, Daniel; Ferey, GerardJournal of the American Chemical Society (2002), 124 (45), 13519-13526CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The 1st three-dimensional Cr(III) dicarboxylate, MIL-53as or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}0.75, was obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or CrIII(OH)·{O2C-C6H4-CO2}. At room temp., MIL-53ht adsorbs atm. H2O immediately to give CrIII(OH)·{O2C-C6H4-CO2}·H2O or MIL-53lt (lt: low-temp. form, ht:high-temp. form). Structures, which were detd. by using x-ray powder diffraction data, are built up from chains of Cr(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of 1-dimensional large pore channels filled with free disordered terephthalic mols. (MIL-53as) or H2O mols. (MIL-53lt); when the free mols. are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m2/g. The transition between the hydrated form (MIL-53lt) and the anhyd. solid (MIL-53ht) is fully reversible and followed by a very high breathing effect (more than 5 Å), the pores being clipped in the presence of H2O mols. (MIL-53lt) and reopened when the channels are empty (MIL-53ht). The thermal behavior of the two solids was studied using TGA and x-ray thermodiffractometry. The sorption properties of MIL-53lt also were studied using several org. solvents. Finally, magnetism measurements performed on MIL-53as and MIL-53lt revealed that these two phases are antiferromagnetic with Neel temps. TN of 65 and 55 K, resp. Crystal data for MIL-53as is as follows: orthorhombic space group Pnam with a 17.340(1), b 12.178(1), c 6.822(1) Å, and Z = 4. Crystal data for MIL-53ht is as follows: orthorhombic space group Imcm with a 16.733(1), b 13.038(1), c 6.812(1) Å, and Z = 4. Crystal data for MIL-53lt is as follows: monoclinic space group C2/c with a 19.685(4), b 7.849(1), c 6.782(1) Å, β 104.90(1)°, and Z = 4.
- 48Li, Q.; Zhang, W.; Miljanić, O. Š.; Sue, C.-H.; Zhao, Y.-L.; Liu, L.; Knobler, C. B.; Stoddart, J. F.; Yaghi, O. M. Docking in Metal-Organic Frameworks. Science 2009, 325, 855– 859, DOI: 10.1126/science.1175441[Crossref], [PubMed], [CAS], Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXps1Ogsb4%253D&md5=655dc9f6d1a194d49e7070570cacd2f9Docking in Metal-Organic FrameworksLi, Qiaowei; Zhang, Wenyu; Miljanic, Ognjen S.; Sue, Chi-Hau; Zhao, Yan-Li; Liu, Lihua; Knobler, Carolyn B.; Stoddart, J. Fraser; Yaghi, Omar M.Science (Washington, DC, United States) (2009), 325 (5942), 855-859CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The use of metal-org. frameworks (MOFs) so far has largely relied on nonspecific binding interactions to host small mol. guests. The authors used long org. struts (~2 nm) incorporating 34- and 36-membered macrocyclic polyethers as recognition modules in the construction of several cryst. primitive cubic frameworks that engage in specific binding in a way not obsd. in passive, open reticulated geometries. MOF-1001 is capable of docking paraquat dication (PQT2+) guests within the macrocycles in a stereoelectronically controlled fashion. This act of specific complexation yields quant. the corresponding MOF-1001 pseudorotaxanes, as confirmed by x-ray diffraction and by solid- and soln.-state NMR spectroscopic studies performed on MOF-1001, its pseudorotaxanes, and their mol. strut precursors. A control expt. involving the attempted inclusion of PQT2+ inside a framework (MOF-177) devoid of polyether struts showed negligible uptake of PQT2+, indicating the importance of the macrocyclic polyether in PQT2+ docking.
- 49Deng, H.; Olson, M. A.; Stoddart, J. F.; Yaghi, O. M. Robust Dynamics. Nat. Chem. 2010, 2, 439– 443, DOI: 10.1038/nchem.654[Crossref], [PubMed], [CAS], Google Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXmtlWlt7g%253D&md5=79cf0fcec448dd09b5fbfead8b5c0003Robust dynamicsDeng, Hexiang; Olson, Mark A.; Stoddart, J. Fraser; Yaghi, Omar M.Nature Chemistry (2010), 2 (6), 439-443CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Although metal-org. frameworks are extensive in no. and have found widespread applications, there remains a need to add complexity to their structures in a controlled manner. It is inevitable that frameworks capable of dynamics will be required. However, as in other extended structures, when they are flexible, they fail. We propose that mech. interlocked mols. be inserted covalently into the rigid framework backbone such that they are mounted as integrated components, capable of dynamics, without compromising the fidelity of the entire system. We have coined the term 'robust dynamics' to describe constructs where the repeated dynamics of one entity does not affect the integrity of any others linked to it. The implication of this concept for dynamic mols., whose performance has the disadvantages of random motion, is to bring them to a standstill in three-dimensional extended structures and thus significantly enhance their order, and ultimately their coherence and performance.
- 50Schneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A. Flexible Metal–Organic Frameworks. Chem. Soc. Rev. 2014, 43, 6062– 6096, DOI: 10.1039/C4CS00101J[Crossref], [PubMed], [CAS], Google Scholar50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Slu7nI&md5=b824d2bff6379c9662b50e86739b42f7Flexible metal-organic frameworksSchneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A.Chemical Society Reviews (2014), 43 (16), 6062-6096CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Advances in flexible and functional metal-org. frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009-2013 with ref. to the early pertinent work since the late 1990s. Flexible MOFs combine the cryst. order of the underlying coordination network with cooperative structural transformability. These materials can respond to phys. and chem. stimuli of various kinds in a tunable fashion by mol. design, which does not exist for other known solid-state materials. Among the fascinating properties are so-called breathing and swelling phenomena as a function of host-guest interactions. Phase transitions are triggered by guest adsorption/desorption, photochem., thermal, and mech. stimuli. Other important flexible properties of MOFs, such as linker rotation and sub-net sliding, which are not necessarily accompanied by crystallog. phase transitions, are briefly mentioned as well. Emphasis is given on reviewing the recent progress in application of in situ characterization techniques and the results of theor. approaches to characterize and understand the breathing mechanisms and phase transitions. The flexible MOF systems, which are discussed, are categorized by the type of metal-nodes involved and how their coordination chem. with the linker mols. controls the framework dynamics. Aspects of tailoring the flexible and responsive properties by the mixed component solid-soln. concept are included, and as well examples of possible applications of flexible metal-org. frameworks for sepn., catalysis, sensing, and biomedicine.
- 51Coudert, F.-X. Responsive Metal–Organic Frameworks and Framework Materials: Under Pressure, Taking the Heat, in the Spotlight, with Friends. Chem. Mater. 2015, 27, 1905– 1916, DOI: 10.1021/acs.chemmater.5b00046[ACS Full Text], [CAS], Google Scholar51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXisF2hurw%253D&md5=4c0a4fb50b0c9eefcfd9e1dbc3fca990Responsive Metal-Organic Frameworks and Framework Materials: Under Pressure, Taking the Heat, in the Spotlight, with FriendsCoudert, Francois-XavierChemistry of Materials (2015), 27 (6), 1905-1916CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)A review. Recent years have seen a large increase of the research effort focused on framework materials, including the nowadays-ubiquitous metal-org. frameworks but also dense coordination polymers, covalent org. frameworks, and mol. frameworks. With the quickly increasing no. of structures synthesized and characterized, one pattern emerging is the common occurrence of flexibility. More specifically, an important no. of framework materials are stimuli-responsive: their structure can undergo changes of large amplitude in response to phys. or chem. stimulation. They can display transformations induced by temp., mech. pressure, guest adsorption or evacuation, light absorption, etc. and are sometimes referred to as smart materials, soft crystals, or dynamic materials. This Perspective highlights recent progress in this field, showcasing some of the most novel and unusual responses to stimuli, as well as advances in the fundamental understanding of flexible framework materials.
- 52Martinez-Bulit, P.; Stirk, A. J.; Loeb, S. J. Rotors, Motors, and Machines Inside Metal–Organic Frameworks. Trends in Chemistry 2019, 1, 588– 600, DOI: 10.1016/j.trechm.2019.05.005
- 53Canossa, S.; Ji, Z.; Wuttke, S. Circumventing Wear and Tear of Adaptive Porous Materials. Adv. Funct. Mater. 2020, 1908547, DOI: 10.1002/adfm.201908547
- 54Rowsell, J. L. C.; Spencer, E. C.; Eckert, J.; Howard, J. A. K.; Yaghi, O. M. Gas Adsorption Sites in a Large-Pore Metal-Organic Framework. Science 2005, 309, 1350– 1354, DOI: 10.1126/science.1113247[Crossref], [PubMed], [CAS], Google Scholar54https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXovVOjt7g%253D&md5=f60c7e82ec8088459a2d844cb807f924Gas Adsorption Sites in a Large-Pore Metal-Organic FrameworkRowsell, Jesse L. C.; Spencer, Elinor C.; Eckert, Juergen; Howard, Judith A. K.; Yaghi, Omar M.Science (Washington, DC, United States) (2005), 309 (5739), 1350-1354CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The primary adsorption sites for Ar and N2 within metal-org. framework-5, a cubic structure composed of Zn4O(CO2)6 units and phenylene links defining large pores 12 and 15 angstroms in diam., have been identified by single-crystal x-ray diffraction. Refinement of data collected between 293 and 30 K revealed a total of eight symmetry-independent adsorption sites. Five of these are sites on the zinc oxide unit and the org. link; the remaining three sites form a second layer in the pores. The structural integrity and high symmetry of the framework are retained throughout, with negligible changes resulting from gas adsorption.
- 55Furukawa, H.; Gándara, F.; Zhang, Y.-B.; Jiang, J.; Queen, W. L.; Hudson, M. R.; Yaghi, O. M. Water Adsorption in Porous Metal-Organic Frameworks and Related Materials. J. Am. Chem. Soc. 2014, 136, 4369– 4381, DOI: 10.1021/ja500330a[ACS Full Text], [CAS], Google Scholar55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXjtlOltL0%253D&md5=21f85eb8745a7073aac8aa39e6923ee8Water Adsorption in Porous Metal-Organic Frameworks and Related MaterialsFurukawa, Hiroyasu; Gandara, Felipe; Zhang, Yue-Biao; Jiang, Juncong; Queen, Wendy L.; Hudson, Matthew R.; Yaghi, Omar M.Journal of the American Chemical Society (2014), 136 (11), 4369-4381CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Three criteria for achieving high performing porous materials for water adsorption have been identified. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. Water adsorption properties of 23 materials were investigated, 20 of which being metal-org. frameworks (MOFs). Among the MOFs were 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcryst. powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examd. for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)4(-CO2) secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl org. linkers to make extended porous frameworks. The permanent porosity of all 23 materials was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temp. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermol. interaction between adsorbed water mols. within the pores.
- 56Tanabe, K. K.; Wang, Z.; Cohen, S. M. Systematic Functionalization of a Metal-Organic Framework via a Postsynthetic Modification Approach. J. Am. Chem. Soc. 2008, 130, 8508– 8517, DOI: 10.1021/ja801848j[ACS Full Text], [CAS], Google Scholar56https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmvFKltrw%253D&md5=1e185fd35a2fa8f5872c195a72fba475Systematic Functionalization of a Metal-Organic Framework via a Postsynthetic Modification ApproachTanabe, Kristine K.; Wang, Zhenqiang; Cohen, Seth M.Journal of the American Chemical Society (2008), 130 (26), 8508-8517CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The pendant amino groups in isoreticular metal-org. framework-3 (IRMOF-3) were subjected to postsynthetic modification with 10 linear alkyl anhydrides [O(CO(CH2)nCH3)2] (where n = 1 to 18) and the extent of conversion, thermal and structural stability, and Brunauer-Emmett-Teller (BET) surface areas of the resulting materials were probed. 1H NMR of digested samples showed that longer alkyl chain anhydrides resulted in lower conversions of IRMOF-3 to the corresponding amide framework (designated as IRMOF-3-AM2 to IRMOF-3-AM19). Percent conversions ranged from essentially quant. (∼99%, -AM2) to ∼7% (-AM19) with IRMOF-3 samples. Modified samples were thermally stable up to approx. 430 °C and remained cryst. based on powder X-ray diffraction (PXRD) measurements. Under specific reaction conditions, significant conversions were obtained with complete retention of crystallinity, as verified by single-crystal X-ray diffraction expts. Single crystals of modified IRMOF-3 samples all showed that the F-centered cubic framework was preserved. All single crystals used for X-ray diffraction were analyzed by electrospray ionization mass spectrometry (ESI-MS) to confirm that these frameworks contained the modified 1,4-benzenedicarboxylate ligand. Single crystals of each modified IRMOF-3 were further characterized by measuring the dinitrogen gas sorption of each framework to det. the effects of modification on the porosity of the MOF. BET surface areas (m2/g) confirmed that all modified IRMOF-3 samples maintained microporosity regardless of the extent of modification. The surface area of modified MOFs was found to correlate to the size and no. of substituents added to the framework.
- 57Inokuma, Y.; Yoshioka, S.; Ariyoshi, J.; Arai, T.; Hitora, Y.; Takada, K.; Matsunaga, S.; Rissanen, K.; Fujita, M. X-ray Analysis on the Nanogram to Microgram Scale using Porous Complexes. Nature 2013, 495, 461– 466, DOI: 10.1038/nature11990[Crossref], [PubMed], [CAS], Google Scholar57https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXkslWkt7Y%253D&md5=311c16f17f42a64354c8d7e01b5685a7X-ray analysis on the nanogram to microgram scale using porous complexesInokuma, Yasuhide; Yoshioka, Shota; Ariyoshi, Junko; Arai, Tatsuhiko; Hitora, Yuki; Takada, Kentaro; Matsunaga, Shigeki; Rissanen, Kari; Fujita, MakotoNature (London, United Kingdom) (2013), 495 (7442), 461-466CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)X-ray single-crystal diffraction (SCD) anal. has the intrinsic limitation that the target mols. must be obtained as single crystals. The authors report a protocol for SCD anal. that does not require the crystn. of the sample. In the authors' method, tiny crystals of porous complexes are soaked in a soln. of the target, such that the complexes can absorb the target mols. Crystallog. anal. clearly dets. the absorbed guest structures along with the host frameworks. Because the SCD anal. is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram-microgram order. As little as ∼80 ng of a sample is enough for the SCD anal. In combination with HPLC, the authors' protocol allows the direct characterization of multiple fractions, establishing a prototypical means of liq. chromatog. SCD anal. Also, the authors unambiguously detd. the structure of a scarce marine natural product using only 5 μg of the compd.
- 58Lee, S.; Kapustin, E. A.; Yaghi, O. M. Coordinative Alignment of Molecules in Chiral Metal-Organic Frameworks. Science 2016, 353, 808– 811, DOI: 10.1126/science.aaf9135[Crossref], [PubMed], [CAS], Google Scholar58https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlCju7zP&md5=e4c3357bdcb899451669d13d60abf053Coordinative alignment of molecules in chiral metal-organic frameworksLee, Seungkyu; Kapustin, Eugene A.; Yaghi, Omar M.Science (Washington, DC, United States) (2016), 353 (6301), 808-811CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A chiral metal-org. framework, MOF-520, was used to coordinatively bind and align mols. of varying size, complexity, and functionality. The reduced motional degrees of freedom obtained with this coordinative alignment method allowed the structures of mols. to be detd. by single-crystal x-ray diffraction techniques. The chirality of the MOF backbone also served as a ref. in the structure soln. for an unambiguous assignment of the abs. configuration of bound mols. Sixteen mols. representing four common functional groups (primary alc., phenol, vicinal diol, and carboxylic acid), ranging in complexity from methanol to plant hormones (gibberellins, contg. eight stereocenters), were crystd. and had their precise structure detd. We distinguished single and double bonds in gibberellins, and we enantioselectively crystd. racemic jasmonic acid, whose abs. configuration had only been inferred from derivs.
- 59Spek, A. L. PLATON SQUEEZE: A Tool for the Calculation of the Disordered Solvent Contribution to the Calculated Structure Factors. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 9– 18, DOI: 10.1107/S2053229614024929[Crossref], [PubMed], [CAS], Google Scholar59https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjvFejtw%253D%253D&md5=88200a7c2b687d49b1dedf1a7b7fa38dPLATON SQUEEZE: a tool for the calculation of the disordered solvent contribution to the calculated structure factorsSpek, Anthony L.Acta Crystallographica, Section C: Structural Chemistry (2015), 71 (1), 9-18CODEN: ACSCGG; ISSN:2053-2296. (International Union of Crystallography)The completion of a crystal structure detn. is often hampered by the presence of embedded solvent mols. or ions that are seriously disordered. Their contribution to the calcd. structure factors in the least-squares refinement of a crystal structure has to be included in some way. Traditionally, an atomistic solvent disorder model is attempted. Such an approach is generally to be preferred, but it does not always lead to a satisfactory result and may even be impossible in cases where channels in the structure are filled with continuous electron d. This paper documents the SQUEEZE method as an alternative means of addressing the solvent disorder issue. It conveniently interfaces with the 2014 version of the least-squares refinement program SHELXL [Sheldrick (2015). Acta Cryst. C71. In the press] and other refinement programs that accept externally provided fixed contributions to the calcd. structure factors. The PLATON SQUEEZE tool calcs. the solvent contribution to the structure factors by back-Fourier transformation of the electron d. found in the solvent-accessible region of a phase-optimized difference electron-d. map. The actual least-squares structure refinement is delegated to, for example, SHELXL. The current versions of PLATON SQUEEZE and SHELXL now address several of the unnecessary complications with the earlier implementation of the SQUEEZE procedure that were a necessity because least-squares refinement with the now superseded SHELXL97 program did not allow for the input of fixed externally provided contributions to the structure-factor calcn. It is no longer necessary to subtract the solvent contribution temporarily from the obsd. intensities to be able to use SHELXL for the least-squares refinement, since that program now accepts the solvent contribution from an external file ( file) if the ABIN instruction is used. In addn., many twinned structures contg. disordered solvents are now also treatable by SQUEEZE. The details of a SQUEEZE calcn. are now automatically included in the CIF archive file, along with the unmerged reflection data. The current implementation of the SQUEEZE procedure is described, and discussed and illustrated with three examples. Two of them are based on the reflection data of published structures and one on synthetic reflection data generated for a published structure.
- 60Clegg, W. Some Reflections on Symmetry: Pitfalls of Automation and Some Illustrative Examples. Acta Cryst. E 2019, 75, 1812– 1819, DOI: 10.1107/S2056989019014907[Crossref], [CAS], Google Scholar60https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitleqtLrP&md5=bf70682693bf058b69710bcb4187eec2Some reflections on symmetry: pitfalls of automation and some illustrative examplesClegg, WilliamActa Crystallographica, Section E: Crystallographic Communications (2019), 75 (12), 1812-1819CODEN: ACSECI; ISSN:2056-9890. (International Union of Crystallography)In the context of increasing hardware and software automation in the process of crystal structure detn. by X-ray diffraction, and based on conference sessions presenting some of the experience of senior crystallographers for the benefit of younger colleagues, an outline is given here of some basic concepts and applications of symmetry in crystallog. Three specific examples of structure detns. are discussed, for which an understanding of these aspects of symmetry avoids mistakes that can readily be made by reliance on automatic procedures. Topics addressed include pseudo-symmetry, twinning, real and apparent disorder, chirality, and structure validation.
- 61Spek, A. CheckCIF Validation ALERTS: What They Mean and How to Respond. Acta Cryst. E 2020, 76, 1– 11, DOI: 10.1107/S2056989019016244[Crossref], [PubMed], [CAS], Google Scholar61https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXkvFaisg%253D%253D&md5=8abe01336ac08b0deb698bbb01835186checkCIF validation ALERTS: what they mean and how to respondSpek, Anthony L.Acta Crystallographica, Section E: Crystallographic Communications (2020), 76 (1), 1-11CODEN: ACSECI; ISSN:2056-9890. (International Union of Crystallography)A review. Authors of a paper that includes a new crystal-structure detn. are expected to not only report the structural results of interest and their interpretation, but are also expected to archive in computer-readable CIF format the exptl. data on which the crystal-structure anal. is based. Addnl., an IUCr/checkCIF validation report will be required for the review of a submitted paper. Such a validation report, automatically created from the deposited CIF file, lists as ALERTS not only potential errors or unusual findings, but also suggestions for improvement along with interesting information on the structure at hand. Major ALERTS for issues are expected to have been acted on already before the submission for publication or discussed in the assocd. paper and/or commented on in the CIF file. In addn., referees, readers and users of the data should be able to make their own judgment and interpretation of the underlying exptl. data or perform their own calcns. with the archived data. All the above is consistent with the FAIR (findable, accessible, interoperable, and reusable) initiative [Helliwell (2019). Struct. Dyn.6, 05430]. Validation can also be helpful for less experienced authors in pointing to and avoiding of crystal-structure detn. and interpretation pitfalls. The IUCr web-based checkCIF server provides such a validation report, based on data uploaded in CIF format. Alternatively, a locally installable checkCIF version is available to be used iteratively during the structure-detn. process. ALERTS come mostly as short single-line messages. There is also a short explanation of the ALERTS available through the IUCr web server or with the locally installed PLATON/checkCIF version. This paper provides addnl. background information on the checkCIF procedure and addnl. details for a no. of ALERTS along with options for how to act on them.
- 62Linden, A. Obtaining the Best Results: Aspects of Data Collection, Model Finalization and Interpretation of Results in Small-molecule Crystal-structure Determination. Acta Cryst. E 2020, 76, 765– 775, DOI: 10.1107/S2056989020005368[Crossref], [CAS], Google Scholar62https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtV2rsL3K&md5=8e916b681d9eb4a3583c4c06cfeeb0f9Obtaining the best results: aspects of data collection, model finalization and interpretation of results in small-molecule crystal-structure determinationLinden, AnthonyActa Crystallographica, Section E: Crystallographic Communications (2020), 76 (6), 765-775CODEN: ACSECI; ISSN:2056-9890. (International Union of Crystallography)In small-mol. single-crystal structure detn., we now have at our disposal an inspiring range of fantastic diffractometers with better, brighter sources, and faster, more sensitive detectors. Faster and more powerful computers provide integrated tools and software with impressive graphical user interfaces. Yet these tools can lead to the temptation not to check the work thoroughly and one can too easily overlook tell-tale signs that something might be amiss in a structure detn.; validation with checkCIF is not always revealing. This article aims to encourage practitioners, young and seasoned, by enhancing their structure-detn. toolboxes with a selection of tips and tricks on recognizing and handling aspects that one should constantly be aware of. Topics include a pitfall when setting up data collections, the usefulness of reciprocal lattice layer images, processing twinned data, tips for disorder modeling and the use of restraints, ensuring hydrogen atoms are added to a model correctly, validation beyond checkCIF, and the derivation and interpretation of the final results.
- 63Giacovazzo, C. Phasing in Crystallography: A Modern Perspective; Oxford University Press: Oxford, 2014.Google ScholarThere is no corresponding record for this reference.
- 64Gándara, F.; Bennett, T. D. Crystallography of Metal-Organic Frameworks. IUCrJ 2014, 1, 563– 570, DOI: 10.1107/S2052252514020351[Crossref], [PubMed], [CAS], Google Scholar64https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhvVyju77P&md5=503c253bbfffb1855582556c662913deCrystallography of metal-organic frameworksGandara, Felipe; Bennett, Thomas D.IUCrJ (2014), 1 (6), 563-570CODEN: IUCRAJ; ISSN:2052-2525. (International Union of Crystallography)Metal-org. frameworks (MOFs) are one of the most intensely studied material types in recent times. Their networks, resulting from the formation of strong bonds between inorg. and org. building units, offer unparalleled chem. diversity and pore environments of growing complexity. Therefore, advances in single-crystal X-ray diffraction equipment and techniques are required to characterize materials with increasingly larger surface areas, and more complex linkers. In addn., while structure soln. from powder diffraction data is possible, the area is much less populated and we detail the current efforts going on here. We also review the growing no. of reports on diffraction under non-ambient conditions, including the response of MOF structures to very high pressures. Such expts. are important due to the expected presence of stresses in proposed applications of MOFs - evidence suggesting rich and complex behavior. Given the entwined and inseparable nature of their structure, properties and applications, it is essential that the field of structural elucidation is able to continue growing and advancing, so as not to provide a rate-limiting step on characterization of their properties and incorporation into devices and applications. This review has been prepd. with this in mind.
- 65Gándara, F.; Furukawa, H.; Lee, S.; Yaghi, O. M. High Methane Storage Capacity in Aluminum Metal–Organic Frameworks. J. Am. Chem. Soc. 2014, 136, 5271– 5274, DOI: 10.1021/ja501606h[ACS Full Text], [CAS], Google Scholar65https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXkslamt7w%253D&md5=f45850d29d222bb32621c184ec84ca01High Methane Storage Capacity in Aluminum Metal-Organic FrameworksGandara, Felipe; Furukawa, Hiroyasu; Lee, Seungkyu; Yaghi, Omar M.Journal of the American Chemical Society (2014), 136 (14), 5271-5274CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The use of porous materials to store natural gas in vehicles requires large amts. of methane per unit of vol. Here the authors report the synthesis, crystal structure and methane adsorption properties of two new aluminum metal-org. frameworks, MOF-519 and MOF-520. Both materials exhibit permanent porosity and high methane volumetric storage capacity: MOF-519 has a volumetric capacity of 200 and 279 cm3 cm-3 at 298 K and 35 and 80 bar, resp., and MOF-520 has a volumetric capacity of 162 and 231 cm3 cm-3 under the same conditions. Also, MOF-519 exhibits an exceptional working capacity, being able to deliver a large amt. of methane at pressures between 5 and 35 bar, 151 cm3 cm-3, and between 5 and 80 bar, 230 cm3 cm-3.
- 66Zhao, Y.; Guo, L.; Gándara, F.; Ma, Y.; Liu, Z.; Zhu, C.; Lyu, H.; Trickett, C. A.; Kapustin, E. A.; Terasaki, O.; Yaghi, O. M. A Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic Frameworks. J. Am. Chem. Soc. 2017, 139, 13166– 13172, DOI: 10.1021/jacs.7b07457[ACS Full Text], [CAS], Google Scholar66https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtl2lsb7J&md5=21ff2b0cba138d5bbfb342b4cae51a3bA Synthetic Route for Crystals of Woven Structures, Uniform Nanocrystals, and Thin Films of Imine Covalent Organic FrameworksZhao, Yingbo; Guo, Lei; Gandara, Felipe; Ma, Yanhang; Liu, Zheng; Zhu, Chenhui; Lyu, Hao; Trickett, Christopher A.; Kapustin, Eugene A.; Terasaki, Osamu; Yaghi, Omar M.Journal of the American Chemical Society (2017), 139 (37), 13166-13172CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Developing synthetic methodol. to crystallize extended covalent structures was an important pursuit of reticular chem. Here, we report a homogeneous synthetic route for imine covalent org. frameworks (COFs) where crystallites emerge from clear solns. without forming amorphous polyimine ppts. The key feature of this route is the utilization of tert-butyloxycarbonyl group protected amine building blocks, which are deprotected in situ and gradually nucleate the cryst. framework. We demonstrate the utility of this approach by crystg. a woven covalent org. framework (COF-112), in which covalent org. threads are interlaced to form a three-dimensional woven framework. The homogeneous imine COF synthesis also enabled the control of nucleation and crystal growth leading to uniform nanocrystals, through microwave-assisted reactions, and facile prepn. of oriented thin films.
- 67Ma, T.; Kapustin, E. A.; Yin, S. X.; Liang, L.; Zhou, Z.; Niu, J.; Li, L.-H.; Wang, Y.; Su, J.; Li, J.; Wang, X.; Wang, W. D.; Wang, W.; Sun, J.; Yaghi, O. M. Single-Crystal X-ray Diffraction Structures of Covalent Organic Frameworks. Science 2018, 361, 48– 52, DOI: 10.1126/science.aat7679[Crossref], [PubMed], [CAS], Google Scholar67https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXht1Cjs7zM&md5=9c25f3d95459d93a6affbfb36fef477cSingle-crystal x-ray diffraction structures of covalent organic frameworksMa, Tianqiong; Kapustin, Eugene A.; Yin, Shawn X.; Liang, Lin; Zhou, Zhengyang; Niu, Jing; Li, Li-Hua; Wang, Yingying; Su, Jie; Li, Jian; Wang, Xiaoge; Wang, Wei David; Wang, Wei; Sun, Junliang; Yaghi, Omar M.Science (Washington, DC, United States) (2018), 361 (6397), 48-52CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. The crystn. problem is an outstanding challenge in the chem. of porous covalent org. frameworks (COFs). Their structural characterization was limited to modeling and solns. based on powder x-ray or electron diffraction data. Single crystals of COFs amenable to x-ray diffraction characterization were not reported. A general procedure was developed to grow large single crystals of 3-dimensional imine-based COFs (COF-300, hydrated form of COF-300, COF-303, LZU-79, and LZU-111). The high quality of the crystals allowed collection of single-crystal x-ray diffraction data of up to 0.83-Å resoln., leading to unambiguous soln. and precise anisotropic refinement. Characteristics such as degree of interpenetration, arrangement of H2O guests, the reversed imine connectivity, linker disorder, and uncommon topol. were deciphered with at. precision-aspects impossible to det. without single crystals.
- 68Zhang, D.; Oleynikov, P.; Hovmöller, S.; Zou, X. Collecting 3D Electron Diffraction Data by the Rotation Method. Z. Kristallogr. 2010, 225, 94– 102, DOI: 10.1524/zkri.2010.1202[Crossref], [CAS], Google Scholar68https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXltFWqsLg%253D&md5=aeb9f3488219a0b20ffdac02582387e4Collecting 3D electron diffraction data by the rotation methodZhang, Daliang; Oleynikov, Peter; Hovmoeller, Sven; Zou, XiaodongZeitschrift fuer Kristallographie - Crystalline Materials (2010), 225 (2-3), 94-102CODEN: ZKCMAJ; ISSN:2194-4946. (Oldenbourg Wissenschaftsverlag GmbH)A new method for collecting complete 3-dimensional electron diffraction data is described. Diffraction data is collected by combining electron beam tilt at many very small steps, with rotation of the crystal in a few but large steps. A no. of practical considerations are discussed, as well as advantages and disadvantages compared to other methods of collecting electron diffraction data.
- 69Zhang, Y.-B.; Su, J.; Furukawa, H.; Yun, Y.; Gándara, F.; Duong, A.; Zou, X.; Yaghi, O. M. Single-Crystal Structure of a Covalent Organic Framework. J. Am. Chem. Soc. 2013, 135, 16336– 16339, DOI: 10.1021/ja409033p[ACS Full Text], [CAS], Google Scholar69https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs1Cktr3N&md5=ea22e0f58fcdda105e732e4fede57bc5Single-Crystal Structure of a Covalent Organic FrameworkZhang, Yue-Biao; Su, Jie; Furukawa, Hiroyasu; Yun, Yifeng; Gandara, Felipe; Duong, Adam; Zou, Xiaodong; Yaghi, Omar M.Journal of the American Chemical Society (2013), 135 (44), 16336-16339CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The crystal structure of a new covalent org. framework, termed COF-320, is detd. by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepd. by an imine condensation of tetra-(4-anilyl)-methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 °C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m2/g and a methane total uptake of 15.0 wt. % (176 cm3/cm3) at 25 °C and 80 bar. The successful detn. of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chem.
- 70Diercks, C. S.; Yaghi, O. M. The Atom, the Molecule, and the Covalent Organic Framework. Science 2017, 355, eaal1585, DOI: 10.1126/science.aal1585
- 71Le Bail, A. Whole Powder Pattern Decomposition Methods and Applications: A Retrospection. Powder Diffr. 2005, 20, 316– 326, DOI: 10.1154/1.2135315[Crossref], [CAS], Google Scholar71https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht12lsb%252FN&md5=1903ec1ca6e2afd307973c930bd9e365Whole powder pattern decomposition methods and applications: A retrospectionLe Bail, ArmelPowder Diffraction (2005), 20 (4), 316-326CODEN: PODIE2; ISSN:0885-7156. (American Institute of Physics)A review is given on methods extg. fast all the peak intensities from a complete powder diffraction pattern. The genesis of the modern whole powder pattern decompn. methods (the so-called Pawley and Le Bail methods) is detailed and their importance and domains of application are decoded from the most cited papers citing them. These methods represented a decisive step toward the possibility to solve more easily, if not routinely, a structure solely from a powder sample. The contributions from the Louer's group during the rising years 1987-1993 are stressed.
- 72Rietveld, H. M. A Profile Refinement Method for Nuclear and Magnetic Structures. J. Appl. Crystallogr. 1969, 2, 65– 71, DOI: 10.1107/S0021889869006558[Crossref], [CAS], Google Scholar72https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1MXksVeisbk%253D&md5=3e3acdf00920ecd78a9bc042511e7fc4Profile refinement method for nuclear and magnetic structuresRietveld, H. M.Journal of Applied Crystallography (1969), 2 (Pt. 2), 65-71CODEN: JACGAR; ISSN:0021-8898.A structural refinement method for neutron diffraction is presented which makes direct use of the profile intensities obtained from the powder diagram. It is applicable to nuclear structures and to magnetic structures which can be described on the nuclear unit cell or a multiple thereof. Equations for the measured profiles to be used in the least sqs. treatment are cor. for asymmetry and preferred orientation; the angular dependence of the half widths of the peaks is given by the formula of Caglioti, et al. (1958). The magnetic contribution to the profile equation is expressed by calcg. only one av. cross section for each set of equiv. reflections. It is possible to introduce constraint functions, linear or quadratic, between parameters used in the least sqs. treatment. Results of the use of this method are given for a series of compds. In all instances it has proved superior to any other method involving integrated neutron powder intensities, single or overlapping.
- 73Ockwig, N. W.; Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Reticular Chemistry: Occurrence and Taxonomy of Nets and Grammar for the Design of Frameworks. Acc. Chem. Res. 2005, 38, 176– 182, DOI: 10.1021/ar020022l[ACS Full Text], [CAS], Google Scholar73https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXksFSgsg%253D%253D&md5=13530d98a4733672738db281372887aeReticular Chemistry: Occurrence and Taxonomy of Nets and Grammar for the Design of FrameworksOckwig, Nathan W.; Delgado-Friedrichs, Olaf; O'Keeffe, Michael; Yaghi, Omar M.Accounts of Chemical Research (2005), 38 (3), 176-182CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)The structures of all 1127 three-periodic extended metal-org. frameworks (MOFs) reported in the Cambridge Structure Database were analyzed, and their underlying topol. was detd. It is remarkable that among the almost infinite no. of net topologies that are available for MOFs to adopt, only a handful of nets are actually obsd. The discovery of this inversion between expected and obsd. nets led the authors to deduce a system of classification taxonomy for interpreting and rationalizing known MOF structures, as well as those that will be made in future. The origin of this inversion is attributed to the different modes with which MOF synthesis was approached. Specifically, three levels of complexity are defined that embody rules grammar for the design of MOFs and other extended structures. This system accounts for the present proliferation of MOF structures of high symmetry nets, but more importantly, it provides the basis for designing a building block that codes for a specific structure and, indeed, only that structure.
- 74RCSR, http://rcsr.net, accessed April 25, 2020.Google ScholarThere is no corresponding record for this reference.
- 75Suga, M.; Asahina, S.; Sakuda, Y.; Kazumori, H.; Nishiyama, H.; Nokuo, T.; Alfredsson, V.; Kjellman, T.; Stevens, S. M.; Cho, H. S.; Cho, M.; Han, L.; Che, S.; Anderson, M. W.; Schüth, F.; Deng, H.; Yaghi, O. M.; Liu, Z.; Jeong, H. Y.; Stein, A.; Sakamoto, K.; Ryoo, R.; Terasaki, O. Recent Progress in Scanning Electron Microscopy for the Characterization of Fine Structural Details of Nano Materials. Prog. Solid State Chem. 2014, 42, 1– 2, DOI: 10.1016/j.progsolidstchem.2014.02.001[Crossref], [CAS], Google Scholar75https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXks12ksLY%253D&md5=eba822410773b2f229ccb1c468add1d2Recent progress in scanning electron microscopy for the characterization of fine structural details of nano materialsSuga, Mitsuo; Asahina, Shunsuke; Sakuda, Yusuke; Kazumori, Hiroyoshi; Nishiyama, Hidetoshi; Nokuo, Takeshi; Alfredsson, Viveka; Kjellman, Tomas; Stevens, Sam M.; Cho, Hae Sung; Cho, Minhyung; Han, Lu; Che, Shunai; Anderson, Michael W.; Schuth, Ferdi; Deng, Hexiang; Yaghi, Omar M.; Liu, Zheng; Jeong, Hu Young; Stein, Andreas; Sakamoto, Kazuyuki; Ryoo, Ryong; Terasaki, OsamuProgress in Solid State Chemistry (2014), 42 (1-2), 1-21CODEN: PSSTAW; ISSN:0079-6786. (Elsevier Ltd.)A review. Research concerning nanomaterials (metal-org. frameworks (MOFs), zeolites, mesoporous silicas, etc.) and the nano-scale, including potential barriers for the particulates to diffusion to/from is of increasing importance to the understanding of the catalytic utility of porous materials when combined with any potential superstructures (such as hierarchically porous materials). However, it is difficult to characterize the structure of for example MOFs via x-ray powder diffraction because of the serious overlapping of reflections caused by their large unit cells, and it is also difficult to directly observe the opening of surface pores using ordinary methods. Electron-microscopic methods including high-resoln. SEM (HRSEM) have therefore become imperative for the above challenges. Presented is the theory and practical application of recent advances such as through-the-lens detection systems, which permit a reduced landing energy and the selection of high-resoln., topog. specific emitted electrons, even from elec. insulating nanomaterials.
- 76Hillman, F.; Zimmerman, J. M.; Paek, S.-M.; Hamid, M. R. A.; Lim, W. T.; Jeong, H.-K. Rapid Microwave-Assisted Synthesis of Hybrid Zeolitic–Imidazolate Frameworks with Mixed Metals and Mixed Linkers. J. Mater. Chem. A 2017, 5, 6090– 6099, DOI: 10.1039/C6TA11170J[Crossref], [CAS], Google Scholar76https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjsFGltrk%253D&md5=50e2dbc3c2863e9f52c46c6562c9b041Rapid microwave-assisted synthesis of hybrid zeolitic-imidazolate frameworks with mixed metals and mixed linkersHillman, Febrian; Zimmerman, John M.; Paek, Seung-Min; Hamid, Mohamad R. A.; Lim, Woo Taik; Jeong, Hae-KwonJournal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (13), 6090-6099CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)Herein the authors report a new microwave-assisted synthetic strategy to rapidly prep. hybrid zeolitic-imidazolate frameworks (ZIFs): ZIFs with mixed metal centers and/or mixed linkers. The microwave-based method significantly shortens synthesis time, produces a higher yield, substantially reduces the amts. of ligands, and eliminates the use of deprotonating agents. The x-ray diffraction pattern reveals that mixed metal CoZn-ZIF-8 (i.e., ZIF-8 with both Co and Zn centers) maintains the sodalite (SOD) zeolitic topol. from the ZIF-8 parent. Elemental mapping using energy-dispersive x-ray spectroscopy (EDS) and electronic/geometric information obtained from X-ray absorption spectroscopy (XAS) confirm the uniform distribution of tetrahedral Co and Zn metal centers within the same framework of the mixed-metal ZIF. The metal to nitrogen (M-N) stretching frequencies of IR bands are systematically blue-shifted as the Co/Zn ratio in the mixed metal ZIF increases. Also, for the 1st time, a hybrid ZIF with both mixed metal centers (Co and Zn) and mixed linkers (2-methylimidazolate and benzimidazolate) was prepd. through 1-step microwave synthesis. Finally, mixed metal CoZn-ZIF-8 with a Co/Zn ratio of ∼1 was grown as membranes on porous α-Al2O3 supports, showing a higher propylene/propane sepn. factor (∼120) when compared to pure Zn-ZIF-8 membranes (∼63) prepd. by a similar method.
- 77Wiktor, C.; Meledina, M.; Turner, S.; Lebedev, O. I.; Fischer, R. A. Transmission Electron Microscopy on Metal–Organic Frameworks – a Review. J. Mater. Chem. A 2017, 5, 14969– 14989, DOI: 10.1039/C7TA00194K[Crossref], [CAS], Google Scholar77https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXptlSnsLw%253D&md5=7ffb273660f9ff35f370b7baf4917d3aTransmission electron microscopy on metal-organic frameworks - a reviewWiktor, Christian; Meledina, Maria; Turner, Stuart; Lebedev, Oleg I.; Fischer, Roland A.Journal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (29), 14969-14989CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)Versatile materials like metal-org. frameworks require careful characterization. Transmission electron microscopy is a very powerful method that can address a multitude of investigative challenges. In this review we present TEM studies that yielded valuable insights into the investigated MOFs to illustrate the potential of TEM despite the sensitivity of MOFs to the electron beam.
- 78Greer, H.; Zhou, W. Electron diffraction and HRTEM imaging of beam-sensitive materials. Crystallogr. Rev. 2011, 17, 163– 185
