Emergence of Coupled Rotor Dynamics in Metal–Organic Frameworks via Tuned Steric InteractionsClick to copy article linkArticle link copied!
- Adrian Gonzalez-NelsonAdrian Gonzalez-NelsonDepartment of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The NetherlandsDPI, P.O.Box 92, 5600 AX Eindhoven, The NetherlandsMore by Adrian Gonzalez-Nelson
- Srinidhi MulaSrinidhi MulaDepartment of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The NetherlandsMore by Srinidhi Mula
- Mantas ŠimėnasMantas ŠimėnasFaculty of Physics, Vilnius University, LT-10222 Vilnius, LithuaniaMore by Mantas Šimėnas
- Sergejus Balčiu̅nasSergejus Balčiu̅nasFaculty of Physics, Vilnius University, LT-10222 Vilnius, LithuaniaMore by Sergejus Balčiu̅nas
- Adam R. AltenhofAdam R. AltenhofDepartment of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United StatesNational High Magnetic Field Laboratory, Tallahassee, Florida 32310, United StatesMore by Adam R. Altenhof
- Cameron S. VojvodinCameron S. VojvodinDepartment of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United StatesNational High Magnetic Field Laboratory, Tallahassee, Florida 32310, United StatesMore by Cameron S. Vojvodin
- Stefano CanossaStefano CanossaEMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, BelgiumMore by Stefano Canossa
- Ju̅ras Banys
- Robert W. Schurko*Robert W. Schurko*[email protected]Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United StatesNational High Magnetic Field Laboratory, Tallahassee, Florida 32310, United StatesMore by Robert W. Schurko
- François-Xavier Coudert*François-Xavier Coudert*[email protected]Chimie ParisTech, PSL University, CNRS, Institut de Recherche de Chimie Paris, 75005 Paris, FranceMore by François-Xavier Coudert
- Monique A. van der Veen*Monique A. van der Veen*[email protected]Department of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The NetherlandsMore by Monique A. van der Veen
Abstract
The organic components in metal–organic frameworks (MOFs) are unique: they are embedded in a crystalline lattice, yet, as they are separated from each other by tunable free space, a large variety of dynamic behavior can emerge. These rotational dynamics of the organic linkers are especially important due to their influence over properties such as gas adsorption and kinetics of guest release. To fully exploit linker rotation, such as in the form of molecular machines, it is necessary to engineer correlated linker dynamics to achieve their cooperative functional motion. Here, we show that for MIL-53, a topology with closely spaced rotors, the phenylene functionalization allows researchers to tune the rotors’ steric environment, shifting linker rotation from completely static to rapid motions at frequencies above 100 MHz. For steric interactions that start to inhibit independent rotor motion, we identify for the first time the emergence of coupled rotation modes in linker dynamics. These findings pave the way for function-specific engineering of gear-like cooperative motion in MOFs.
This publication is licensed under
License Summary*
You are free to share(copy and redistribute) this article in any medium or format within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
Non-Commercial (NC): Only non-commercial uses of the work are permitted.
No Derivatives (ND): Derivative works may be created for non-commercial purposes, but sharing is prohibited.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
License Summary*
You are free to share(copy and redistribute) this article in any medium or format within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
Non-Commercial (NC): Only non-commercial uses of the work are permitted.
No Derivatives (ND): Derivative works may be created for non-commercial purposes, but sharing is prohibited.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
License Summary*
You are free to share(copy and redistribute) this article in any medium or format within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
Non-Commercial (NC): Only non-commercial uses of the work are permitted.
No Derivatives (ND): Derivative works may be created for non-commercial purposes, but sharing is prohibited.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
License Summary*
You are free to share(copy and redistribute) this article in any medium or format within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
Non-Commercial (NC): Only non-commercial uses of the work are permitted.
No Derivatives (ND): Derivative works may be created for non-commercial purposes, but sharing is prohibited.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
License Summary*
You are free to share(copy and redistribute) this article in any medium or format within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
Non-Commercial (NC): Only non-commercial uses of the work are permitted.
No Derivatives (ND): Derivative works may be created for non-commercial purposes, but sharing is prohibited.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
Introduction
Results and Discussion
Chart 1
R | ΔErot (kJ mol–1)a |
---|---|
H | 47.7 |
hydroxy | 81.8 |
amino | 53.7 |
methoxy | 42.1 |
cyano | 34.5 |
fluoro | 35.9 |
chloro | 25.0 |
bromo | 25.1 |
nitro | 17.1 |
Maximum energy state for each molecule (E90) is obtained from constrained geometry optimizations, setting the dihedral angles between carboxylic groups and ring to 90°. Relative values were obtained with respect to a planar conformation energy; see Supporting Information section 3.1 for details.
Figure 1
Figure 1. Structure of three members of the MIL-53 family viewed along the pore direction. (a) MIL-53(Al) (lp), (b) NO2-MIL-53(Al) (lp), and (c) NH2-MIL-53(Al) (np). This topology is characterized by four distinct rows of linkers per unit cell forming rhombic pores. Closest row distances for each MOF are marked in magenta. For compete unit cell parameters, see Table S2.
MOF | rotor spacing within row (Å)a | pore rhombus angle (deg) | row-to-row distance (Å)b |
---|---|---|---|
MIL-53(Al) (lp) | 6.6 | 75.0 | 6.4 |
NO2-MIL-53(Al) (lp) | 6.7 | 79.5 | 6.8 |
NH2-MIL-53(Al) (np) | 6.6 | 43.8 | 3.8 |
Defined as distance between neighboring C–C rotation axes, see Supporting Information section 3.2.
For definition, see Supporting Information section 3.2.
Figure 2
Figure 2. Effect of linker rotation on the potential energy as studied by DFT. (a) Unit cell of NO2-MIL-53(Al) with central linker in 0° rotation with respect to (011) plane (pink); hydrogens omitted for clarity. (b) Rotation angle is defined as the angle between benzene ring plane and (011) plane, taking 0° as the conformation with the functional group pointing in the positive [100] direction. The sign of the angle is assigned based on the direction normal of the reference plane. (c) Potential energy profiles for the rotation of one linker in a NH2-MIL-53(Al) and NO2-MIL-53(Al) unit cell. The direction of rotation is indicated by the direction of the marker. (d) Example of an unfavorable head-to-head nitro group encounters in adjacent linkers when they are located on the same side of the ring (top) and on different sides (bottom).
Figure 3
Figure 3. Dielectric spectra of the three systems. (a, b) Imaginary part (ε′′) of ε* for NO2-MIL-53(Al) with respect to temperature (a) and frequency (b). The latter includes the fitted Cole–Cole model as continuous lines. (c, d) Temperature dependence of ε″ for NH2-MIL-53(Al) (c) and MIL-53(Al) (d).
Figure 4
Figure 4. Solid-state 2H NMR studies of NO2-MIL-53(Al)-d3. (a) Experimental (black) and simulated (red) variable-temperature 2H SSNMR spectra of NO2-MIL-53(Al)-d3. (b) Spectra are composed of overlapping patterns representing SML (<103 Hz) and FML (>107–108 Hz) motions, with relative integrated intensities indicated to the right of the simulated spectra. (c) Cartesian frame of reference for the rotation model. (d) Representation of 2H exchange sites and angles used in the model; deuterons are shown in light blue.
Figure 5
Figure 5. Cooperative rotation in NO2-MIL-53(Al). (a) Rotation angle traces of two neighboring rings in a 2 × 1 × 1 cell MD simulation at 700 K. Correlated motion is observed, with simultaneous angle changes in opposite directions (i, ii, iii), when nitro groups are in proximity (N···N distance ca. 4 Å). (b) Selected snapshots (i–iv) of linker pair conformation during a coupled rotation. As ring A rotates in the positive direction, ring B reaches the space originally occupied by ring A.
Conclusions
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.1c03630.
Experimental section, synthesis and characterization, computational details, supporting figures and discussion, rotation angle measurement pseudocode (PDF)
MD simulation of supercell NO2-MIL-53(Al) at 700 K (MPG)
Structure factors file of single-crystal XRD data of NO2-MIL-53(Al) (TXT)
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.
Acknowledgments
The work of A.G.-N. forms part of the research program of DPI, NEWPOL project 731.015.506. M.A.v.d.V. and S.M. are grateful for funding by the European Research Council (Grant No. 759212) within the Horizon 2020 Framework Programme (H2020-EU.1.1). This work was sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities. R.W.S. is grateful for research support from The Florida State University and the National High Magnetic Field Laboratory (NHMFL), which is funded by the National Science Foundation Cooperative Agreement (DMR-1644779) and by the State of Florida. R.W.S. also acknowledges the support of the National Science Foundation Chemical Measurement and Imaging Program, with partial cofunding from the Solid State and Materials Chemistry Program (NSF-2003854) as well as the support of the Natural Science and Engineering Research Council (NSERC, Canada) through an Research Tools and Instrument (RTI) grant and NSERC Discovery Grant (RGPIN-2016_06642). The authors are grateful to the Canadian Foundation for Innovation (CFI), the Ontario Innovation Trust (OIT), and the University of Windsor for support of solid-state characterization facilities at Windsor. F.-X.C. acknowledges financial support from the Agence Nationale de la Recherche under project MATAREB (ANR-18-CE29-0009-01) and access to high-performance computing platforms provided by GENCI Grant No. A0090807069. The Elettra Synchrotron facility (CNR Trieste, Italy) is gratefully acknowledged for granting beamtime at the single-crystal diffraction beamline XRD1 (Proposal ID 20185483) and the beamline staff is thanked for the assistance.
References
This article references 71 other publications.
- 1van Meer, G.; Voelker, D. R.; Feigenson, G. W. Membrane Lipids: Where They Are and How They Behave. Nat. Rev. Mol. Cell Biol. 2008, 9 (2), 112– 124, DOI: 10.1038/nrm2330Google Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXovFOntw%253D%253D&md5=13d4eb41956211e22d3a9ee5c6b73854Membrane lipids: where they are and how they behavevan Meer, Gerrit; Voelker, Dennis R.; Feigenson, Gerald W.Nature Reviews Molecular Cell Biology (2008), 9 (2), 112-124CODEN: NRMCBP; ISSN:1471-0072. (Nature Publishing Group)A review. Throughout the biol. world, a 30 Å hydrophobic film typically delimits the environments that serve as the margin between life and death for individual cells. Biochem. and biophys. findings have provided a detailed model of the compn. and structure of membranes, which includes levels of dynamic organization both across the lipid bilayer (lipid asymmetry) and in the lateral dimension (lipid domains) of membranes. How do cells apply anabolic and catabolic enzymes, translocases, and transporters, plus the intrinsic phys. phase behavior of lipids and their interactions with membrane proteins, to create the unique compns. and multiple functionalities of their individual membranes.
- 2Duncan, A. L.; Reddy, T.; Koldsø, H.; Hélie, J.; Fowler, P. W.; Chavent, M.; Sansom, M. S. P. Protein Crowding and Lipid Complexity Influence the Nanoscale Dynamic Organization of Ion Channels in Cell Membranes. Sci. Rep. 2017, 7 (1), 16647, DOI: 10.1038/s41598-017-16865-6Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC1M3ms1CgtA%253D%253D&md5=0cbee7d73392b2947e9ed7bf57f060aaProtein crowding and lipid complexity influence the nanoscale dynamic organization of ion channels in cell membranesDuncan Anna L; Reddy Tyler; Koldso Heidi; Helie Jean; Fowler Philip W; Chavent Matthieu; Sansom Mark S P; Reddy Tyler; Koldso Heidi; Helie Jean; Fowler Philip W; Chavent MatthieuScientific reports (2017), 7 (1), 16647 ISSN:.Cell membranes are crowded and complex environments. To investigate the effect of protein-lipid interactions on dynamic organization in mammalian cell membranes, we have performed coarse-grained molecular dynamics simulations containing >100 copies of an inwardly rectifying potassium (Kir) channel which forms specific interactions with the regulatory lipid phosphatidylinositol 4,5-bisphosphate (PIP2). The tendency of protein molecules to cluster has the effect of organizing the membrane into dynamic compartments. At the same time, the diversity of lipids present has a marked effect on the clustering behavior of ion channels. Sub-diffusion of proteins and lipids is observed. Protein crowding alters the sub-diffusive behavior of proteins and lipids such as PIP2 which interact tightly with Kir channels. Protein crowding also affects bilayer properties, such as membrane undulations and bending rigidity, in a PIP2-dependent manner. This interplay between the diffusion and the dynamic organization of Kir channels may have important implications for channel function.
- 3van der Kooij, H. M.; Semerdzhiev, S. A.; Buijs, J.; Broer, D. J.; Liu, D.; Sprakel, J. Morphing of Liquid Crystal Surfaces by Emergent Collectivity. Nat. Commun. 2019, 10 (1), 1– 9, DOI: 10.1038/s41467-019-11501-5Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsFCiurfP&md5=f2d6568b3bf2db458739b67b53db501eMorphing of liquid crystal surfaces by emergent collectivityvan der Kooij, Hanne M.; Semerdzhiev, Slav A.; Buijs, Jesse; Broer, Dirk J.; Liu, Danqing; Sprakel, JorisNature Communications (2019), 10 (1), 1-9CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)Liq. crystal surfaces can undergo topog. morphing in response to external cues. These shape-shifting coatings promise a revolution in various applications, from haptic feedback in soft robotics or displays to self-cleaning solar panels. The changes in surface topog. can be controlled by tailoring the mol. architecture and mechanics of the liq. crystal network. However, the nanoscopic mechanisms that drive morphol. transitions remain unclear. Here, we introduce a frequency-resolved nanostrain imaging method to elucidate the emergent dynamics underlying field-induced shape-shifting. We show how surface morphing occurs in three distinct stages: (i) the mol. dipoles oscillate with the alternating field (10-100 ms), (ii) this leads to collective plasticization of the glassy network (∼1 s), (iii) culminating in actuation of the topog. (10-100 s). The first stage appears universal and governed by dielec. coupling. By contrast, yielding and deformation rely on a delicate balance between liq. crystal order, field properties and network viscoelasticity.
- 4Catalano, L.; Naumov, P. Exploiting Rotational Motion in Molecular Crystals. CrystEngComm 2018, 20 (39), 5872– 5883, DOI: 10.1039/C8CE00420JGoogle Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXotFWgu70%253D&md5=f4fb5c4e8b3f4b31e4db691ea8cc08a2Exploiting rotational motion in molecular crystalsCatalano, Luca; Naumov, PanceCrystEngComm (2018), 20 (39), 5872-5883CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)A review. Various aspects of mol. motion in crystals have been extensively studied in different research fields of chem. as a valuable source of structural and dynamic information en route to new smart materials and solid-state mol. machines. Recent research efforts have been directed towards engineering cryst. media with specific motile components, namely, amphidynamic crystals, whose dynamics can be exploited to achieve specific functions such as sensing, gas sepn. and switchable dielecs. The most promising structural models within this line of pursuit are based upon anisotropic Brownian rotary trajectories. In this highlight, we review the recent advances in this field, with particular emphasis on potential applications. This summary should provide useful guidelines for further development of this remarkable class of materials.
- 5Vogelsberg, C. S.; Garcia-Garibay, M. A. Crystalline Molecular Machines: Function, Phase Order, Dimensionality, and Composition. Chem. Soc. Rev. 2012, 41 (5), 1892– 1910, DOI: 10.1039/C1CS15197EGoogle Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XitFyjsLw%253D&md5=33557d840c4c090a6a7d8d04365b5dc6Crystalline molecular machines: function, phase order, dimensionality, and compositionVogelsberg, Cortnie S.; Garcia-Garibay, Miguel A.Chemical Society Reviews (2012), 41 (5), 1892-1910CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The design of mol. machines is stimulated by the possibility of developing new materials with complex physicochem. and mech. properties that are responsive to external stimuli. Condensed-phase matter with anisotropic mol. order and controlled dynamics, also defined as amphidynamic crystals, offers a promising platform for the design of bulk materials capable of performing such functions. Recent studies have shown that it is possible to engineer mol. crystals and extended solids with Brownian rotation about specific axes that can be interfaced with external fields, which may ultimately be used to design novel optoelectronic materials. Structure/function relationships of amphidynamic materials have been characterized, establishing the blueprints to further engineer sophisticated function. However, the synthesis of amphidynamic mol. machines composed of multiple "parts" is essential to realize increasingly complex behavior. Recent progress in amphidynamic multicomponent systems suggests that sophisticated functions similar to those of simple biomol. machines may eventually be within reach.
- 6Khuong, T.-A. A. V; Nunez, J. E.; Godinez, C. E.; Garcia-Garibay, M. A. Crystalline Molecular Machines: A Quest toward Solid-State Dynamics and Function. Acc. Chem. Res. 2006, 39 (6), 413– 422, DOI: 10.1021/ar0680217Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xjt1Kms7s%253D&md5=65d7a75ad0d31017ab5023392082a8f1Crystalline Molecular Machines: A Quest Toward Solid-State Dynamics and FunctionKhuong, Tinh-Alfredo V.; Nunez, Jose E.; Godinez, Carlos E.; Garcia-Garibay, Miguel A.Accounts of Chemical Research (2006), 39 (6), 413-422CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. Complex mol. machinery may be envisioned as densely packed, multicomponent, self-assembling systems built with high structural precision to control the dynamics of one or more internal degrees of freedom. With mol. gyroscopes as a test, we describe a general strategy to design crystals capable of supporting structurally programmed mol. motions, a practical approach to their synthesis, convenient strategies to characterize their solid-state dynamics, and potential applications based on polar structures responding collectively to external fields.
- 7Comotti, A.; Bracco, S.; Sozzani, P. Molecular Rotors Built in Porous Materials. Acc. Chem. Res. 2016, 49 (9), 1701– 1710, DOI: 10.1021/acs.accounts.6b00215Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlGrs7nF&md5=3ede0039750a5d47042bd3a4299d9dbfMolecular Rotors Built in Porous MaterialsComotti, Angiolina; Bracco, Silvia; Sozzani, PieroAccounts of Chemical Research (2016), 49 (9), 1701-1710CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)Mols. and materials can show dynamic structures in which the dominant mechanism is rotary motion. The single mobile elements are defined as "mol. rotors" and exhibit special properties (compared with their static counterparts), being able in perspective to greatly modulate the dielec. response and form the basis for mol. motors that are designed with the idea of making mols. perform a useful mech. function. The construction of ordered rotary elements into a solid is a necessary feature for such design, because it enables the alignment of rotors and the fine-tuning of their steric and dipolar interactions. Crystal surfaces or bulk crystals are the most suitable to adapt rotors in 2D or 3D arrangements and engineer juxtaposition of the rotors in an ordered way. Nevertheless, it is only in recent times that materials showing porosity and remarkably low d. have undergone tremendous development. The characteristics of large free vol. combine well with the virtually unhindered motion of the mol. rotors built into their structure. Indeed, the mol. rotors are used as struts in porous covalent and supramol. architectures, spanning both hybrid and fully org. materials. The modularity of the approach renders possible a variety of rotor geometrical arrangements in both robust frameworks stable up to 850 K and self-assembled mol. materials. A nanosecond (fast dynamics) motional regime can be achieved at temps. lower than 240 K, enabling rotor arrays operating in the solid state even at low temps. Furthermore, in nanoporous materials, mol. rotors can interact with the diffusing chem. species, be they liqs., vapors, or gases. Through this chem. intervention, rotor speed can be modulated at will, enabling a new generation of rotor-contg. materials sensitive to guests. In principle, an applied elec. field can be the stimulus for chem. release from porous materials. The effort needed to obtain strong dipoles that are noncentrosym. mounted onto rotors and do not hamper rotational motion is a further aspect of this research activity. Thus, materials showing dielec. properties in response to applied elec. fields have been fabricated. This may lead to challenging materials that are promptly responsive to an applied elec. field, altering the ferroelec. or antiferroelec. ground state by fast dipole reorientation when subjected to elec. polarization.
- 8Deng, H.; Olson, M. A.; Stoddart, J. F.; Yaghi, O. M. Robust Dynamics. Nat. Chem. 2010, 2 (6), 439– 443, DOI: 10.1038/nchem.654Google Scholar8https://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.
- 9Gonzalez-Nelson, A.; Coudert, F.-X.; van der Veen, M. Rotational Dynamics of Linkers in Metal–Organic Frameworks. Nanomaterials 2019, 9 (3), 330, DOI: 10.3390/nano9030330Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtFWrs7bO&md5=ff79c23c592c32d12d1589028651b842Rotational dynamics of linkers in metal-organic frameworksGonzalez-Nelson, Adrian; Coudert, Francois-Xavier; Van Der Veen, Monique A.Nanomaterials (2019), 9 (3), 330CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)A review. Among the numerous fascinating properties of metal-org. frameworks (MOFs), their rotational dynamics is perhaps one of the most intriguing, with clear consequences for adsorption and sepn. of mols., as well as for optical and mech. properties. A closer look at the rotational mobility in MOF linkers reveals that it is not only a considerably widespread phenomenon, but also a fairly diverse one. Still, the impact of these dynamics is often understated. In this review, we address the various mechanisms of linker rotation reported in the growing collection of literature, followed by a highlight of the methods currently used in their study, and we conclude with the impacts that such dynamics have on existing and future applications.
- 10Martinez-Bulit, P.; Stirk, A. J.; Loeb, S. J. Rotors, Motors, and Machines Inside Metal–Organic Frameworks. Trends in Chemistry. Cell Press September 2019, 1, 588– 600, DOI: 10.1016/j.trechm.2019.05.005Google ScholarThere is no corresponding record for this reference.
- 11Dong, J.; Wee, V.; Peh, S. B.; Zhao, D. Molecular-Rotor-Driven Advanced Porous Materials. Angew. Chem., Int. Ed. 2021, 60, 2– 16, DOI: 10.1002/anie.202101646Google ScholarThere is no corresponding record for this reference.
- 12Gee, J. A.; Sholl, D. S. Effect of Framework Flexibility on C 8 Aromatic Adsorption at High Loadings in Metal–Organic Frameworks. J. Phys. Chem. C 2016, 120 (1), 370– 376, DOI: 10.1021/acs.jpcc.5b10260Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvFKlu7nM&md5=a6cfb8f04df14571ae5130dae5ca34aeEffect of Framework Flexibility on C8 Aromatic Adsorption at High Loadings in Metal-Organic FrameworksGee, Jason A.; Sholl, David S.Journal of Physical Chemistry C (2016), 120 (1), 370-376CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The authors show that the use of this approxn. to describe the multicomponent adsorption of C8 aroms. in MOFs under industrial conditions gives results that differ dramatically from descriptions that include local framework flexibility. To address this issue, we develop an efficient method for capturing the effect of framework flexibility on adsorption in nanoporous materials. This "flexible snapshot" method uses GCMC simulations to model adsorption in snapshots collected using fully flexible MD simulations and can be applied to any framework-adsorbate system for which reliable force fields are available. The method gives considerably better agreement with expts. for multicomponent C8 arom. selectivities in multiple MOFs than more traditional calcns. using a single rigid framework. The rotation of org. linkers in the MOFs has a strong influence on selectivities in these systems. Because many MOFs contain this structural feature, we expect that using simulations that incorporate this kind of internal flexibility will be important in obtaining accurate adsorption predictions in a range of circumstances. This is esp. true for many industrially relevant sepns. in MOFs, in particular, those that exploit high pore loadings of adsorbed species.
- 13Park, J.; Agrawal, M.; Sava Gallis, D. F.; Harvey, J. A.; Greathouse, J. A.; Sholl, D. S. Impact of Intrinsic Framework Flexibility for Selective Adsorption of Sarin in Non-Aqueous Solvents Using Metal–Organic Frameworks. Phys. Chem. Chem. Phys. 2020, 22 (11), 6441– 6448, DOI: 10.1039/C9CP06788DGoogle Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXktVGrtL4%253D&md5=29d64d87c381388a1b7485ed21c8af26Framework flexibility for selective adsorption of sarin in non-aqueous solvents using metal-organic frameworksPark, Jongwoo; Agrawal, Mayank; Sava Gallis, Dorina F.; Harvey, Jacob A.; Greathouse, Jeffery A.; Sholl, David S.Physical Chemistry Chemical Physics (2020), 22 (11), 6441-6448CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Mol. modeling of mixt. adsorption in nanoporous materials can provide insight into the mol.-level details that underlie adsorptive sepns. Modeling of adsorption often employs a rigid framework approxn. for computational convenience. All real materials, however, have intrinsic flexibility due to thermal vibrations of their atoms. In this article, we examine quant. predictions of the adsorption selectivity for a dil. concn. of a chem. warfare agent, sarin, from bulk mixts. with aq. and non-aq. (methanol, iso-Pr alc.) solvents using metal-org. frameworks (MOFs). These predictions were made in MOFs approximated as rigid and also in MOFs allowed to have intrinsic flexibility. Including framework flexibility appears to have important consequences for quant. predictions of adsorption selectivity, particularly for sarin/water mixts. Our observations suggest the intrinsic flexibility of MOFs can have a nontrivial impact on adsorption modeling of mol. mixts., esp. for mixts. contg. polar species and mols. of different sizes.
- 14Agrawal, M.; Bhattacharyya, S.; Huang, Y.; Jayachandrababu, K. C.; Murdock, C. R.; Bentley, J. A.; Rivas-Cardona, A.; Mertens, M. M.; Walton, K. S.; Sholl, D. S.; Nair, S. Liquid-Phase Multicomponent Adsorption and Separation of Xylene Mixtures by Flexible MIL-53 Adsorbents. J. Phys. Chem. C 2018, 122 (1), 386– 397, DOI: 10.1021/acs.jpcc.7b09105Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFOiurnE&md5=ae96c143beca18253acb13c2d9ad386cLiquid-Phase Multicomponent Adsorption and Separation of Xylene Mixtures by Flexible MIL-53 AdsorbentsAgrawal, Mayank; Bhattacharyya, Souryadeep; Huang, Yi; Jayachandrababu, Krishna C.; Murdock, Christopher R.; Bentley, Jason A.; Rivas-Cardona, Alejandra; Mertens, Machteld M.; Walton, Krista S.; Sholl, David S.; Nair, SankarJournal of Physical Chemistry C (2018), 122 (1), 386-397CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The MIL-53 class of metal-org. frameworks (MOFs) has recently generated interest as potential adsorbents for xylene mixt. sepns. Cost-effective sepn. of xylene isomers is challenging owing to the similarity in their mol. structures, kinetic diams., and b.ps. Here we report a systematic exptl. and computational study of xylene isomer adsorption in MIL-53 adsorbents, focusing particularly on the effects of different metal centers, detn. of sepn. properties with industrially relevant quaternary liq.-phase C8 arom. feeds, and a predictive mol. simulation methodol. that accounts for all relevant modes of MIL-53 framework flexibility. Significant scale-up of MIL-53 synthesis was carried out to produce high-quality materials in sufficient quantities (300-500 g each) for detailed measurements. Single-component adsorption simulations incorporating the MIL-53 "breathing" and linker flexibility effects showed good agreement with exptl. isotherms. Upon the basis of these results, three materials - MIL-53(Al), MIL-53(Cr), and MIL-53(Ga) - were selected for detailed quaternary liq. breakthrough measurements. High o-xylene quaternary selectivity was obtained from all of the MIL-53 materials, with MIL-53(Al) being the most selective. Better packing efficiency of o-xylene and its preferred interactions with the MIL-53 framework are hypothesized to lead to high selectivity. Predictions from flexible-structure multicomponent adsorption simulations showed good overall agreement with expt. This is, to the best of our knowledge, the first exptl. report on the xylene adsorption characteristics of MIL-53 materials under industrially relevant operating conditions. In addn., it is also the first attempt to develop computational methods that account for various flexibility modes in MIL-53 materials for adsorption simulations. This has significant broader applications for the successful prediction of adsorption properties of larger mols. (such as C8 arom. isomers) in flexible MOFs.
- 15Verploegh, R. J.; Kulkarni, A.; Boulfelfel, S. E.; Haydak, J. C.; Tang, D.; Sholl, D. S. Screening Diffusion of Small Molecules in Flexible Zeolitic Imidazolate Frameworks Using a DFT-Parameterized Force Field. J. Phys. Chem. C 2019, 123 (14), 9153– 9167, DOI: 10.1021/acs.jpcc.9b00733Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXktlOitbY%253D&md5=0980f16df3829ee10667f763d686c75aScreening diffusion of small molecules in flexible zeolitic imidazolate frameworks using a DFT-parameterized force fieldVerploegh, Ross J.; Kulkarni, Ambarish; Boulfelfel, Salah Eddine; Haydak, Jonathan C.; Tang, Dai; Sholl, David S.Journal of Physical Chemistry C (2019), 123 (14), 9153-9167CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Quant. modeling adsorbate diffusion through zeolitic imidazolate frameworks (ZIFs) must account for the inherent flexibility of these materials. The lack of a transferable intramol. ZIF force field (FF) for use in classical simulations has previously made an accurate simulation of adsorbate diffusion in many ZIFs impossible. We resolve this problem by introducing a d. functional theory parameterized force field (FF) for ZIFs named the intraZIF-FF, which includes perturbations to the class I force fields previously used to model ZIFs. This FF outperforms ad hoc force fields at predicting ab initio relative energies and at. forces taken from fully periodic ab initio mol. dynamics simulations of SALEM-2, ZIF-7, ZIF-8, and ZIF-90. We use the intraZIF-FF to predict the infinite diln. self-diffusion coeffs. of 30 adsorbates with mol. diams. ranging from 2.66 to 7.0 Å in these 4 ZIFs. These results greatly increase the no. of adsorbates for which accurate information about mol. diffusion in ZIFs is available.
- 16Witman, M.; Ling, S.; Jawahery, S.; Boyd, P. G.; Haranczyk, M.; Slater, B.; Smit, B. The Influence of Intrinsic Framework Flexibility on Adsorption in Nanoporous Materials. J. Am. Chem. Soc. 2017, 139 (15), 5547– 5557, DOI: 10.1021/jacs.7b01688Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXltlCms7k%253D&md5=b834291a7ad2b83f735c98e63428eeb1The Influence of Intrinsic Framework Flexibility on Adsorption in Nanoporous MaterialsWitman, Matthew; Ling, Sanliang; Jawahery, Sudi; Boyd, Peter G.; Haranczyk, Maciej; Slater, Ben; Smit, BerendJournal of the American Chemical Society (2017), 139 (15), 5547-5557CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)For applications of metal-org. frameworks (MOFs) such as gas storage and sepn., flexibility is often seen as a parameter that can tune material performance. The authors aim to det. the optimal flexibility for the shape selective sepn. of similarly sized mols. (e.g., Xe/Kr mixts.). To obtain systematic insight into how the flexibility impacts this type of sepn., the authors develop a simple anal. model that predicts a material's Henry regime adsorption and selectivity as a function of flexibility. The authors elucidate the complex dependence of selectivity on a framework's intrinsic flexibility whereby performance is either improved or reduced with increasing flexibility, depending on the material's pore size characteristics. However, the selectivity of a material with the pore size and chem. that already maximizes selectivity in the rigid approxn. is continuously diminished with increasing flexibility, demonstrating that the globally optimal sepn. exists within an entirely rigid pore. Mol. simulations show that our simple model predicts performance trends that are obsd. when screening the adsorption behavior of flexible MOFs. These flexible simulations provide better agreement with exptl. adsorption data in a high-performance material that is not captured when modeling this framework as rigid, an approxn. typically made in high-throughput screening studies. The authors conclude that, for shape selective adsorption applications, the globally optimal material will have the optimal pore size/chem. and minimal intrinsic flexibility even though other nonoptimal materials' selectivity can actually be improved by flexibility. Equally important, we find that flexible simulations can be crit. for correctly modeling adsorption in these types of systems.
- 17Lennox, M. J.; Düren, T. Understanding the Kinetic and Thermodynamic Origins of Xylene Separation in UiO-66(Zr) via Molecular Simulation. J. Phys. Chem. C 2016, 120 (33), 18651– 18658, DOI: 10.1021/acs.jpcc.6b06148Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1Kms7fF&md5=60526609a421092a2bb6cacae13ee182Understanding the Kinetic and Thermodynamic Origins of Xylene Separation in UiO-66(Zr) via Molecular SimulationLennox, Matthew J.; Duren, TinaJournal of Physical Chemistry C (2016), 120 (33), 18651-18658CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Xylene isomers are precursors in many important chem. processes, yet their sepn. via crystn. or distn. is energy intensive. Adsorption presents an attractive, lower-energy alternative and the discovery of adsorbents which outperform the current state-of-the-art zeolitic materials represents one of the key challenges in materials design, with metal-org. frameworks receiving particular attention. One of the most well-studied systems in this context is UiO-66(Zr), which selectively adsorbs o-xylene over the other C8 alkylaroms. The mechanism behind this sepn. has remained unclear, however. In this work, a wide range of computational techniques are employed to explore both the equil. and dynamic behavior of the xylene isomers in UiO-66(Zr). In addn. to correctly predicting the exptl. obsd. ortho-selectivity, it is demonstrated that the equil. selectivity is based upon the complete encapsulation of o-xylene within the pores of the framework. Furthermore, the flexible nature of the adsorbent is crucial in facilitating xylene diffusion and the simulations reveal for the first time significant differences between the intracryst. diffusion mechanisms of the three isomers resulting in a kinetic contribution to the selectivity. Consequently, it is important to include both equil. and kinetic effects when screening MOFs for xylene sepns.
- 18Evans, J. D.; Krause, S.; Feringa, B. L. Cooperative and Synchronized Rotation in Motorized Porous Frameworks: Impact on Local and Global Transport Properties of Confined Fluids. Faraday Discuss. 2021, 225, 286– 300, DOI: 10.1039/D0FD00016GGoogle Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXksFKkt7c%253D&md5=561247e6a6675cf04d8bf3b5d3a2cff6Cooperative and synchronized rotation in motorized porous frameworks: impact on local and global transport properties of confined fluidsEvans, Jack D.; Krause, Simon; Feringa, Ben L.Faraday Discussions (2021), 225 (Cooperative Phenomena in Framework Materials), 286-300CODEN: FDISE6; ISSN:1359-6640. (Royal Society of Chemistry)Mols. in gas and liq. states, as well as in soln., exhibit significant and random Brownian motion. Mols. in the solid-state, although strongly immobilized, can still exhibit significant intramol. dynamics. However, in most framework materials, these intramol. dynamics are driven by temp., and therefore are neither controlled nor spatially or temporarily aligned. In recent years, several examples of mol. machines that allow for a stimuli-responsive control of dynamical motion, such as rotation, have been reported. In this contribution, we investigate the local and global properties of a Lennard-Jones (LJ) fluid surrounding a mol. motor and consider the influence of cooperative and non-directional rotation for a mol. motor-contg. pore system. This study uses classical mol. dynamics simulations to describe a minimal model, which was developed to resemble known mol. motors. The properties of an LJ liq. surrounding an isolated mol. motor remain mostly unaffected by the introduced rotation. We then considered an arrangement of motors within a one-dimensional pore. Changes in diffusivity for pore sizes approaching the length of the rotor were obsd., resulting from rotation of the motors. We also considered the influence of cooperative motor directionality on the directional transport properties of this confined fluid. Importantly, we discovered that specific unidirectional rotation of altitudinal motors can produce directed diffusion.
- 19Aprahamian, I. The Future of Molecular Machines. ACS Cent. Sci. 2020, 6 (3), 347– 358, DOI: 10.1021/acscentsci.0c00064Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXksVShu7c%253D&md5=3f43b0cedea31dc87158e714bf013d75The Future of Molecular MachinesAprahamian, IvanACS Central Science (2020), 6 (3), 347-358CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)A review. Artificial mol. machines have captured the imagination of scientists and nonscientists alike for decades now, given their clear potential to transform and enhance all aspects of human life. In this Outlook, I use a bicycle as an analogy to explain what a mol. machine is, in my opinion, and work through a representative selection of case studies to specify the significant accomplishments made to date, and the obstacles that currently stand between these and the field's fulfillment of its great potential. The hope of this intentionally sober account is to sketch a path toward a rich and exciting research trajectory that might challenge current practitioners and attract junior scientists into its fold. Considering the progress we have witnessed in the past decade, I am pos. that the future of the field is a rosy one. Using a bicycle as an analogy for mol. machines, this Outlook surveys the recent advances in the field, while elaborating on the challenges in the way of it fulfilling its full potential.
- 20Vogelsberg, C. S.; Uribe-Romo, F. J.; Lipton, A. S.; Yang, S.; Houk, K. N.; Brown, S.; Garcia-Garibay, M. A. Ultrafast Rotation in an Amphidynamic Crystalline Metal Organic Framework. Proc. Natl. Acad. Sci. U. S. A. 2017, 114 (52), 13613– 13618, DOI: 10.1073/pnas.1708817115Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGns7%252FN&md5=a6cc4f2b0e4ea8f49e015ba367c02e65Ultrafast rotation in an amphidynamic crystalline metal organic frameworkVogelsberg, Cortnie S.; Uribe-Romo, Fernando J.; Lipton, Andrew S.; Yang, Song; Houk, K. N.; Brown, Stuart; Garcia-Garibay, Miguel A.Proceedings of the National Academy of Sciences of the United States of America (2017), 114 (52), 13613-13618CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Amphidynamic crystals are an emergent class of condensed phase matter designed with a combination of lattice-forming elements linked to components that display engineered dynamics in the solid state. Here, we address the design of a cryst. array of mol. rotors with inertial diffusional rotation at the nanoscale, characterized by the absence of steric or electronic barriers. We solved this challenge with 1,4-bicyclo[2.2.2]octane dicarboxylic acid (BODCA)-MOF, a metal-org. framework (MOF) built with a high-symmetry bicyclo[2.2.2]octane dicarboxylate linker in a Zn4O cubic lattice. Using spin-lattice relaxation 1H solid-state NMR at 29.49 and 13.87 MHz at of 2.3-80 K, we showed that internal rotation occurs in a potential with energy barriers of 0.185 kcal mol-1. These results were confirmed with 2H solid-state NMR line-shape anal. and spin-lattice relaxation at 76.78 MHz obtained between 6 and 298 K, which, combined with mol. dynamics simulations, indicate that inertial diffusional rotation is characterized by a broad range of angular displacements with no residence time at any given site. The ambient temp. rotation of the bicyclo[2.2.2]octane (BCO) group in BODCA-MOF constitutes an example where engineered rotational dynamics in the solid state are as fast as they would be in a high-d. gas or in a low-d. liq. phase.
- 21Bracco, S.; Castiglioni, F.; Comotti, A.; Galli, S.; Negroni, M.; Maspero, A.; Sozzani, P. Ultrafast Molecular Rotors and Their CO2Tuning in MOFs with Rod-Like Ligands. Chem. - Eur. J. 2017, 23 (47), 11210– 11215, DOI: 10.1002/chem.201702930Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Kqt7jP&md5=2c22a9d917a50470d42b84b01b752e35Ultrafast Molecular Rotors and Their CO2 Tuning in MOFs with Rod-Like LigandsBracco, Silvia; Castiglioni, Fabio; Comotti, Angiolina; Galli, Simona; Negroni, Mattia; Maspero, Angelo; Sozzani, PieroChemistry - A European Journal (2017), 23 (47), 11210-11215CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)A metal org. framework (MOF) engineered to contain in its scaffold rod-like struts featuring ultrafast mol. rotors showed extremely rapid 180 ° flip reorientation with rotational rates of 1011 Hz at 150 K. Crystal-pore accessibility of the MOF allowed the CO2 mols. to enter the cavities and control the rotor spinning speed down to 105 Hz at 150 K. Rotor dynamics, as modulated by CO2 loading/unloading in the porous crystals, was described by proton T1 and 2H NMR spectroscopy. This strategy enabled the regulation of rotary motion by the diffusion of the gas within the channels and the detn. of the energetics of rotary dynamics in the presence of CO2.
- 22Perego, J.; Bracco, S.; Negroni, M.; Bezuidenhout, C. X.; Prando, G.; Carretta, P.; Comotti, A.; Sozzani, P. Fast Motion of Molecular Rotors in Metal–Organic Framework Struts at Very Low Temperatures. Nat. Chem. 2020, 12 (9), 845– 851, DOI: 10.1038/s41557-020-0495-3Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlagtLjJ&md5=d8814e5ea7ea69923bca149127b51bedFast motion of molecular rotors in metal-organic framework struts at very low temperaturesPerego, Jacopo; Bracco, Silvia; Negroni, Mattia; Bezuidenhout, Charl X.; Prando, Giacomo; Carretta, Pietro; Comotti, Angiolina; Sozzani, PieroNature Chemistry (2020), 12 (9), 845-851CODEN: NCAHBB; ISSN:1755-4330. (Nature Research)The solid state is typically not well suited to sustaining fast mol. motion, but in recent years a variety of mol. machines, switches and rotors were successfully engineered within porous crystals and on surfaces. Here the authors show a fast-rotating mol. rotor within the bicyclopentane-dicarboxylate struts of a zinc-based metal-org. framework-the carboxylate groups anchored to the metal clusters act as an axle while the bicyclic unit is free to rotate. The three-fold bipyramidal symmetry of the rotator conflicts with the four-fold symmetry of the struts within the cubic crystal cell of the zinc metal-org. framework. This frustrates the formation of stable conformations, allowing for the continuous, unidirectional, hyperfast rotation of the bicyclic units with an energy barrier of 6.2 cal mol-1 and a high frequency persistent for several turns even at very low temps. (1010 Hz <2 K). Using zirconium instead of zinc led to a different metal cluster-carboxylate coordination arrangement in the resulting metal-org. framework, and much slower rotation of the bicyclic units.
- 23Danowski, W.; van Leeuwen, T.; Abdolahzadeh, S.; Roke, D.; Browne, W. R.; Wezenberg, S. J.; Feringa, B. L. Unidirectional Rotary Motion in a Metal–Organic Framework. Nat. Nanotechnol. 2019, 14 (5), 488– 494, DOI: 10.1038/s41565-019-0401-6Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXms1Ogtrk%253D&md5=861d9bbbd1eafb32a0004a698d9d741aUnidirectional rotary motion in a metal-organic frameworkDanowski, Wojciech; van Leeuwen, Thomas; Abdolahzadeh, Shaghayegh; Roke, Diederik; Browne, Wesley R.; Wezenberg, Sander J.; Feringa, Ben L.Nature Nanotechnology (2019), 14 (5), 488-494CODEN: NNAABX; ISSN:1748-3387. (Nature Research)Overcrowded alkene-based light-driven mol. motors are able to perform large-amplitude repetitive unidirectional rotations. Their behavior is well understood in soln. However, Brownian motion precludes the precise positioning at the nanoscale needed to harness cooperative action. Here, authors demonstrate mol. motors organized in cryst. metal-org. frameworks (MOFs). The motor unit becomes a part of the org. linker (or strut), and its spatial arrangement is elucidated through powder and single-crystal x-ray analyses and polarized optical and Raman microscopies. They confirm that the light-driven unidirectional rotation of the motor units is retained in the MOF framework and that the motors can operate in the solid state with similar rotary speed (rate of thermal helix inversion) to that in soln. These 'moto-MOFs' could in the future be used to control dynamic function in cryst. materials.
- 24Kottas, G. S.; Clarke, L. I.; Horinek, D.; Michl, J. Artificial Molecular Rotors. Chem. Rev. 2005, 105 (4), 1281– 1376, DOI: 10.1021/cr0300993Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjt1KmtL4%253D&md5=e1bed85db4dfe2562729760b32fb45a8Artificial Molecular RotorsKottas, Gregg S.; Clarke, Laura I.; Horinek, Dominik; Michl, JosefChemical Reviews (Washington, DC, United States) (2005), 105 (4), 1281-1376CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review on properties of mech. conformational motion of org. mols. in soln. and solids and on surfaces by expts. and mol. dynamics.
- 25Yan, Y.; Kolokolov, D. I.; da Silva, I.; Stepanov, A. G.; Blake, A. J.; Dailly, A.; Manuel, P.; Tang, C. C.; Yang, S.; Schröder, M. Porous Metal–Organic Polyhedral Frameworks with Optimal Molecular Dynamics and Pore Geometry for Methane Storage. J. Am. Chem. Soc. 2017, 139 (38), 13349– 13360, DOI: 10.1021/jacs.7b05453Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1OmsLvM&md5=44b3451283362914bb619f8a35857e44Porous Metal-Organic Polyhedral Frameworks with Optimal Molecular Dynamics and Pore Geometry for Methane StorageYan, Yong; Kolokolov, Daniil I.; da Silva, Ivan; Stepanov, Alexander G.; Blake, Alexander J.; Dailly, Anne; Manuel, Pascal; Tang, Chiu C.; Yang, Sihai; Schroder, MartinJournal of the American Chemical Society (2017), 139 (38), 13349-13360CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Natural gas (methane, CH4) is widely considered as a promising energy carrier for mobile applications. Maximizing the storage capacity is the primary goal for the design of future storage media. Here we report the CH4 storage properties in a family of isostructural (3,24)-connected porous materials, MFM-112a, MFM-115a, and MFM-132a, with different linker backbone functionalization. Both MFM-112a and MFM-115a show excellent CH4 uptakes of 236 and 256 cm3 (STP) cm-3 (vol./vol.) at 80 bar and room temp., resp. Significantly, MFM-115a displays an exceptionally high deliverable CH4 capacity of 208 vol./vol. between 5 and 80 bar at room temp., making it among the best performing metal-org. frameworks for CH4 storage. We also synthesized the partially deuterated versions of the above materials and applied solid-state 2H NMR spectroscopy to show that these three frameworks contain mol. rotors that exhibit motion in fast, medium, and slow regimes, resp. In situ neutron powder diffraction studies on the binding sites for CD4 within MFM-132a and MFM-115a reveal that the primary binding site is located within the small pocket enclosed by the [(Cu2)3(isophthalate)3] window and three anthracene/phenyl panels. The open Cu(II) sites are the secondary/tertiary adsorption sites in these structures. Thus, we obtained direct exptl. evidence showing that a tight cavity can generate a stronger binding affinity to gas mols. than open metal sites. Solid-state 2H NMR spectroscopy and neutron diffraction studies reveal that it is the combination of optimal mol. dynamics, pore geometry and size, and favorable binding sites that leads to the exceptional and different methane uptakes in these materials.
- 26Sokolov, A. N.; Swenson, D. C.; MacGillivray, L. R. Conformational Polymorphism in a Heteromolecular Single Crystal Leads to Concerted Movement Akin to Collective Rack-and-Pinion Gears at the Molecular Level. Proc. Natl. Acad. Sci. U. S. A. 2008, 105 (6), 1794– 1797, DOI: 10.1073/pnas.0706117105Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXisVWmsLk%253D&md5=623028ae5f5030254ff70c55221bcfdbConformational polymorphism in a heteromolecular single crystal leads to concerted movement akin to collective rack-and-pinion gears at the molecular levelSokolov, Anatoliy N.; Swenson, Dale C.; MacGillivray, Leonard R.Proceedings of the National Academy of Sciences of the United States of America (2008), 105 (6), 1794-1797CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)The authors describe a heteromol. single crystal that exhibits three reversible and concerted reorganizations upon heating and cooling. The products of the reorganizations are conformational polymorphs. The reorganizations are postulated to proceed through three motions: (i) alkyl translations, (ii) olefin rotations, and (iii) rotational tilts. The motions are akin to rack-and-pinion gears at the mol. level. The rack-like movement is based on expansions and compressions of alkyl chains that are coupled with pinion-like 180° rotations of olefins. To accommodate the movements, phenol and thiophene components undergo rotational tilts about intermol. hydrogen bonds. The movements are collective, being propagated in close-packed repeating units. This discovery marks a step to understanding how org. solids can support the development of cryst. mol. machines and devices through correlated and collective movements.
- 27Jarowski, P. D.; Houk, K. N.; Garcia-Garibay, M. A. Importance of Correlated Motions on the Low Barrier Rotational Potentials of Crystalline Molecular Gyroscopes. J. Am. Chem. Soc. 2007, 129 (11), 3110– 3117, DOI: 10.1021/ja0637907Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhvF2kurk%253D&md5=f1e97dbccd1a797bdfabc5f30b6d8ed4Importance of Correlated Motions on the Low Barrier Rotational Potentials of Crystalline Molecular GyroscopesJarowski, Peter D.; Houk, K. N.; Garcia-Garibay, Miguel A.Journal of the American Chemical Society (2007), 129 (11), 3110-3117CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The energetic and structural changes taking place upon rotation of the central phenylene of 1,4-bis(3,3,3-triphenylpropynyl)benzene in the solid state were computed using mol. mechanics calcns. Pseudopolymorphic crystals of a benzene clathrate (1A) and a desolvated form (1B) were analyzed with models that account for varying degrees of freedom within the corresponding lattices. The calcd. rotational barriers in a rigid lattice approxn., 78 kcal/mol for 1A and 72 kcal/mol for 1B, are about 5 times greater than those previously measured by variable-temp. 13C CPMAS NMR and quadrupolar echo 2H NMR line-shape anal.: 12.8 kcal/mol for 1A and 14.6 kcal/mol for 1B. The potential energy barriers calcd. with a model that restricts whole body rotation and translational motions but allows for internal rotations give results that are near the exptl. free-energy barriers. The calcd. barriers for 1A and 1B are 15.5 and 16.2 kcal/mol, resp. The differences between the rigid and partially relaxed models are attributed to the effect of correlated motions of the lattice and the rotating group, which are evident from the structural anal. of the at. position data as a function of the dihedral angle of the rotator. The displacements of neighboring mols. near the rotary transition states for 1A and 1B can be as large as 2.7 and 1.1 Å, resp. The displacement and oscillation (C2) of interpenetrating Ph rings from neighboring rotors proximal to the event are significant for both 1A and 1B. In addn., 6-fold (C6) benzene rotations in clathrate 1A were found to be directly correlated to the rotation of the phenylene rotator.
- 28Howe, M. E.; Garcia-Garibay, M. A. The Roles of Intrinsic Barriers and Crystal Fluidity in Determining the Dynamics of Crystalline Molecular Rotors and Molecular Machines. J. Org. Chem. 2019, 84 (16), 9835– 9849, DOI: 10.1021/acs.joc.9b00993Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtVKgtrrP&md5=85fdc24f1710ed3d0fe269d11304032cThe Roles of Intrinsic Barriers and Crystal Fluidity in Determining the Dynamics of Crystalline Molecular Rotors and Molecular MachinesHowe, Morgan E.; Garcia-Garibay, Miguel A.Journal of Organic Chemistry (2019), 84 (16), 9835-9849CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A review. Cryst. solids are a promising platform for the development of mol. machines. They have the potential of combining the mol.-level control of phys. properties caused by isomerizations, conformational motions, or chem. reactions with the emergent properties that arise from long-range order and multiscale phenomena. The construction of cryst. mol. machinery was challenging due to the difficulties assocd. with the design of structures capable of supporting high order and controlled mol. motion in the solid state, a platform that is termed amphidynamic crystals. With ultrafast rotation as the target, previous work on amphidynamic crystals has explored the creation of free space around the rotator, the advantages of vol.-conserving rotational motions, and the challenges assocd. with correlated rotations, or gearing motions. In this Perspective the authors report the results of a systematic anal. of a large no. of examples from the work and that of others, where the creation of free space alone does not always result in ultrafast dynamics. In a limit that applies to porous crystals with large empty vols. such as MOFs and other extended solids, internal motions fall in the regime of activation control, with dynamics detd. by the intrinsic (gas-phase) electronic barriers for rotation around the bond that connects the rotator and the stator. By contrast, internal rotation in close-packed mol. crystals falls in the regime of diffusion-controlled dynamics and depends on the ability of the rotator surroundings to distort and create transient cavities. The authors refer to this property as crystal fluidity and suggest that it may be used as an addnl. guiding principle for the design of cryst. mol. machines. The authors describe the general principles behind the promising field of cryst. mol. machinery, the anal. methods to analyze rotational dynamics of cryst. solids, and the key structural concepts that may help their future development.
- 29Lemouchi, C.; Iliopoulos, K.; Zorina, L.; Simonov, S.; Wzietek, P.; Cauchy, T.; Rodríguez-Fortea, A.; Canadell, E.; Kaleta, J.; Michl, J.; Gindre, D.; Chrysos, M.; Batail, P. Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational Mutations. J. Am. Chem. Soc. 2013, 135 (25), 9366– 9376, DOI: 10.1021/ja4044517Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXoslSqt7k%253D&md5=e1e325c1a8ea8e2e9bdaa2e0bdf9c3c5Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational MutationsLemouchi, Cyprien; Iliopoulos, Konstantinos; Zorina, Leokadiya; Simonov, Sergey; Wzietek, Pawel; Cauchy, Thomas; Rodriguez-Fortea, Antonio; Canadell, Enric; Kaleta, Jiri; Michl, Josef; Gindre, Denis; Chrysos, Michael; Batail, PatrickJournal of the American Chemical Society (2013), 135 (25), 9366-9376CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The rod-like mol. bis((4-(4-pyridyl)ethynyl)bicyclo[2.2.2]oct-1-yl)buta-1,3-diyne, 1, contains two 1,4-bis(ethynyl)bicyclo[2.2.2]octane (BCO) chiral rotators linked by a diyne fragment and self-assembles in a one-dimensional, monoclinic C2/c centrosym. structure where two equil. positions with large occupancy imbalance (88% vs. 12%) are identified on a single rotor site. Combining variable-temp. (70-300 K) proton spin-lattice relaxation, 1H T1-1, at two different 1H Larmor frequencies (55 and 210 MHz) and DFT calcns. of rotational barriers, we were able to assign two types of Brownian rotators with different activation energies, 1.85 and 6.1 kcal mol-1, to the two 1H spin-lattice relaxation processes on the single rotor site. On the basis of DFT calcns., the low-energy process has been assigned to adjacent rotors in a well-correlated synchronous motion, whereas the high-energy process is the manifestation of an abrupt change in their kinematics once two blades of adjacent rotors are seen to rub together. Although crystals of 1 should be second harmonic inactive, a large second-order optical response is recorded when the elec. field oscillates in a direction parallel to the unique rotor axle director. We conclude that conformational mutations by torsional interconversion of the three blades of the BCO units break space-inversion symmetry in sequences of mutamers in dynamic equil. in the crystal in domains at a mesoscopic scale comparable with the wavelength of light used. A control expt. was performed with a cryst. film of a similar tetrayne mol., 1,4-bis(3-((trimethylsilyl)ethynyl)bicyclo[1.1.1]pent-1-yl)buta-1,3-diyne, whose bicyclopentane units can rotate but are achiral and produce no second-order optical response.
- 30Damron, J. T.; Ma, J.; Kurz, R.; Saalwächter, K.; Matzger, A. J.; Ramamoorthy, A. The Influence of Chemical Modification on Linker Rotational Dynamics in Metal–Organic Frameworks. Angew. Chem., Int. Ed. 2018, 57 (28), 8678– 8681, DOI: 10.1002/anie.201805004Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFaltb7O&md5=911053f9a1807954ea692b8ea860b9a0The Influence of Chemical Modification on Linker Rotational Dynamics in Metal-Organic FrameworksDamron, Joshua T.; Ma, Jialiu; Kurz, Ricardo; Saalwaechter, Kay; Matzger, Adam J.; Ramamoorthy, AyyalusamyAngewandte Chemie, International Edition (2018), 57 (28), 8678-8681CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The robust synthetic flexibility of metal-org. frameworks (MOF) offers a promising class of tailor-able materials for which the ability to tune specific physicochem. properties is highly desired. This is achievable only through a thorough description of the consequences for chem. manipulations in structure and dynamics. Magic angle spinning solid-state NMR spectroscopy offers many modalities in this pursuit, particularly for dynamic studies. This work used a sepd. local-field NMR approach to show how specific intra-framework chem. modifications to MOF UiO-66 heavily modulated the dynamic evolution of the org. ring moiety over several orders of magnitude.
- 31Zhou, W.; Yildirim, T. Lattice Dynamics of Metal-Organic Frameworks: Neutron Inelastic Scattering and First-Principles Calculations. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 74 (18), 180301, DOI: 10.1103/PhysRevB.74.180301Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhtlSksLzL&md5=e96393d378d670d1896cb21ed0a6633fLattice dynamics of metal-organic frameworks: Neutron inelastic scattering and first-principles calculationsZhou, W.; Yildirim, T.Physical Review B: Condensed Matter and Materials Physics (2006), 74 (18), 180301/1-180301/4CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)By combining neutron inelastic scattering (NIS) and first-principles calcns., we have investigated the lattice dynamics of metal-org. framework-5 (MOF5). The structural stability of MOF5 was evaluated by calcg. the three cubic elastic consts. We find that the shear modulus, c44 = 1.16 GPA, is unusually small, while two other moduli are relatively large (i.e., c11 = 29.42 GPa and c12 = 12.56 GPa). We predict that MOF5 is very close to structural instability and may yield interesting phases under high pressure and strain. The phonon dispersion curves and phonon d. of states were directly calcd. and our simulated NIS spectrum agrees very well with our exptl. data. Several interesting phonon modes are discussed, including the softest twisting modes of the org. linker.
- 32Ryder, M. R.; Van De Voorde, B.; Civalleri, B.; Bennett, T. D.; Mukhopadhyay, S.; Cinque, G.; Fernandez-Alonso, F.; De Vos, D.; Rudić, S.; Tan, J. C. Detecting Molecular Rotational Dynamics Complementing the Low-Frequency Terahertz Vibrations in a Zirconium-Based Metal-Organic Framework. Phys. Rev. Lett. 2017, 118 (25), 1– 6, DOI: 10.1103/PhysRevLett.118.255502Google ScholarThere is no corresponding record for this reference.
- 33Liepuoniute, I.; Huynh, C. M.; Perez-Estrada, S.; Wang, Y.; Khan, S.; Houk, K. N.; Garcia-Garibay, M. A. Enhanced Rotation by Ground State Destabilization in Amphidynamic Crystals of a Dipolar 2,3-Difluorophenylene Rotator as Established by Solid State 2 H NMR and Dielectric Spectroscopy. J. Phys. Chem. C 2020, 124 (28), 15391– 15398, DOI: 10.1021/acs.jpcc.0c05314Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1als7bE&md5=a00baee64b848515e9706fc9914724e5Enhanced Rotation by Ground State Destabilization in Amphidynamic Crystals of a Dipolar 2,3-Difluorophenylene Rotator as Established by Solid State 2H NMR and Dielectric SpectroscopyLiepuoniute, Ieva; Huynh, Chau Minh; Perez-Estrada, Salvador; Wang, Yangyang; Khan, Saeed; Houk, K. N.; Garcia-Garibay, Miguel A.Journal of Physical Chemistry C (2020), 124 (28), 15391-15398CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)We report the synthesis and rotational dynamics of the pillared metal-org. framework Zn2(F2BDC)2(DABCO) where F2BDC = 2,3-difluorobenzene-1,4-dicarboxylate acts as a rotating dipolar linker and DABCO = 1,4-diazabicyclo[2.2.2]octane acts as a spacer (F2MOF 1). The pillared structure of F2MOF 1 was confirmed by X-ray diffraction and CP-MAS 13C NMR analyses. Using variable temp. solid state 2H NMR and broadband dielec. spectroscopy, we characterized the rotational dynamics of the dipolar F2BDC linker in the solid state. Variable temp. (VT) quadrupolar echo 2H NMR measurements revealed a rotational activation energy of Ea = 6.8 ± 0.1 kcal/mol, which agreed well with temp.- and frequency-dependent dielec. measurements, indicating a barrier of Ea = 7.1 ± 0.5 kcal/mol. Structural data from single crystal X-ray diffraction and quantum mech. calcns. (DFT) suggest that the rotational potential is detd. by steric interactions between the dipolar rotator and the stator linkers such that fluorine atoms in the F2BDC linker reduce the activation energy by destabilization of the coplanar BDC ground state.
- 34Kolokolov, D. I.; Jobic, H.; Stepanov, A. G.; Guillerm, V.; Devic, T.; Serre, C.; Férey, G. Dynamics of Benzene Rings in MIL-53(Cr) and MIL-47(V) Frameworks Studied By2H NMR Spectroscopy. Angew. Chem., Int. Ed. 2010, 49 (28), 4791– 4794, DOI: 10.1002/anie.201001238Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXotVCgu7Y%253D&md5=5e153c8b326eaf438208f14ae46b8340Dynamics of Benzene Rings in MIL-53(Cr) and MIL-47(V) Frameworks Studied by 2H NMR SpectroscopyKolokolov, Daniil I.; Jobic, Herve; Stepanov, Alexander G.; Guillerm, Vincent; Devic, Thomas; Serre, Christian; Ferey, GerardAngewandte Chemie, International Edition (2010), 49 (28), 4791-4794, S4791/1-S4791/3CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)2H NMR method allowed us to show that the arom. rings in MIL-47(V) and MIL-53(Cr) perform π flips about their symmetry axis. The benzene rings flip faster and with lower activation energy in the flexible MIL-53(Cr) than in the rigid MIL-47(V). This demonstrates that arom. rings in MOFs can be a sensitive marker of the framework structural properties. The terephthalate groups in both MILs can be considered as immobile on a microscopic timescale, in agreement with previous QENS studies and mol. simulations. However, in macroscopic measurements, small mols. like H2, CO2, and CH4 have the possibility to switch from one tunnel to another, and this must be taken into account, for instance, in adsorption or sepn. processes. 2010 Wiley-VCH Verlag GmbH and Co.
- 35Kolokolov, D. I.; Stepanov, A. G.; Jobic, H. Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene Loadings. J. Phys. Chem. C 2014, 118 (29), 15978– 15984, DOI: 10.1021/jp506010pGoogle Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVOjt7jF&md5=762caac7292523f0c2ba3d043f5dd359Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene LoadingsKolokolov, Daniil I.; Stepanov, Alexander G.; Jobic, HerveJournal of Physical Chemistry C (2014), 118 (29), 15978-15984CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Large pore (LP) and narrow pore (NP) cryst. state interconversions of the MIL-53(Al) MOF framework has been monitored via following the thermally induced evolution of phenylene fragments using 2H solid-state NMR. The dynamics of phenylene fragments was shown to be very sensitive to the loading of xylene guests and the MOF structural state. The mol. rotation rate was higher and the activation barrier lower for the LP state of the guest-free or loosely loaded material, whereas the NP and LP states with high loadings and dense guest packing showed a decrease of the rotation rates and increase of the rotation energetic barrier.
- 36Khudozhitkov, A. E.; Jobic, H.; Freude, D.; Haase, J.; Kolokolov, D. I.; Stepanov, A. G. Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of Xylene. J. Phys. Chem. C 2016, 120 (38), 21704– 21709, DOI: 10.1021/acs.jpcc.6b08114Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVWntLrF&md5=81e4e92ea30a9e9c0e5fac8125a46fc8Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of XyleneKhudozhitkov, Alexander E.; Jobic, Herve; Freude, Dieter; Haase, Juergen; Kolokolov, Daniil I.; Stepanov, Alexander G.Journal of Physical Chemistry C (2016), 120 (38), 21704-21709CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)MIL-53 (Al) is an important example of metal-org. frameworks (MOFs) with a flexible framework capable to efficiently sep. ortho and para isomers of xylene at moderate temps. The MIL-53 MOF contains mobile terephthalate phenylene fragments that can be used as a dynamic probe to study the guest-host interactions and the origin of the sepn. selectivity. Here 2H NMR spin alignment echo technique for the 1st time was applied to probe ultraslow structural mobility (0.1-1 kHz) in MOFs materials, with particular application to MIL-53(Al) satd. with ortho or para isomers of xylene. A specific influence of different isomers of xylene adsorbed in the MOF pores on the rotation of the phenylenes in MIL-53 for the temp. range with proved sepn. selectivity (T < 393 K) is shown. The rotation of phenylene fragments is sensitive to the type of xylene isomer. The phenylenes' rotation performs 1 order of magnitude slower in the presence of o-xylene (kortho = 70 s-1) compared to the same rotation in the presence of the other isomer, p-xylene (kpara = 800 s-1) at T ∼ 373 K. This is rationalized by a stronger interaction of the ortho isomer with the linker than the para isomer. This finding offers an understanding of the mol. mechanism of p- and o-xylene sepn. by MIL-53: stronger interaction of o-xylene with org. linker compared to p-xylene provides sepn. of these isomers on MIL-53.
- 37Khudozhitkov, A. E.; Kolokolov, D. I.; Stepanov, A. G.; Bolotov, V. A.; Dybtsev, D. N. Metal-Cation-Independent Dynamics of Phenylene Ring in Microporous MOFs: A 2H Solid-State NMR Study. J. Phys. Chem. C 2015, 119 (50), 28038– 28045, DOI: 10.1021/acs.jpcc.5b09435Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVCjtbnK&md5=4f00b6c94e1cde9695b63be9a49d199aMetal-Cation-Independent Dynamics of Phenylene Ring in Microporous MOFs: A 2H Solid-State NMR StudyKhudozhitkov, Alexander E.; Kolokolov, Daniil I.; Stepanov, Alexander G.; Bolotov, Vsevolod A.; Dybtsev, Danil N.Journal of Physical Chemistry C (2015), 119 (50), 28038-28045CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Mobility of the org. linkers in metal-org. frameworks (MOFs) is an established phenomenon. Knowledge of the details of linker motion in MOFs could provide a great deal of information about the linker structure and the way the guest mols. interact with the org. framework. However, the mobility of the org. linkers is poorly characterized. The extent of the influence of the metal cation or guest mols. on linker motion is still unknown for MOFs with identical topologies. The authors analyzed the rotational dynamics of the phenylene ring fragments of terephthalate (1,4-benzenedicarboxylate, bdc) linkers in MOFs [M2(bdc)2(dabco)]·G (M = Co2+, Ni2+, Cu2+, Zn2+; dabco =1,4-diazabicyclo[2.2.2]octane; G = none or DMF, DMF). The reorientational motion of the phenylene rings was performed by π-flipping of the plane of the ring about its C2 axis. The dynamics of the phenylene rings is insensitive to the variation of the metal cation, whereas the loading of the guest DMF mols. provides both a significant decrease of the rate of π-flips and an increase of the activation energy for the motion of the phenylene rings.
- 38Gould, S. L.; Tranchemontagne, D.; Yaghi, O. M.; Garcia-Garibay, M. A. Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment. J. Am. Chem. Soc. 2008, 130 (11), 3246– 3247, DOI: 10.1021/ja077122cGoogle Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXitFegtrk%253D&md5=109b33711ef380fc414fbf4681127b7cAmphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered EnvironmentGould, Stephanie L.; Tranchemontagne, David; Yaghi, Omar M.; Garcia-Garibay, Miguel A.Journal of the American Chemical Society (2008), 130 (11), 3246-3247CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Metal-org. frameworks (MOFs) have been the focus of much interest within the context of hydrogen storage and other materials applications. With static metal clusters linked by axially substituted org. spacers capable of experiencing internal rotations, MOFs are one of the most promising amphidynamic materials to investigate and exploit the dynamics of cryst. solids. In this communication we report an exptl. study of the rotational dynamics of the 1,4-phenylenedicarboxylate bridge of MOF-5, which has no steric contacts that might contribute to the rotational barrier. Highly reproducible 1H T1 relaxation, high-resoln. 13C CPMAS, and variable temp. quadrupolar echo 2H NMR data were obtained from high quality samples that were sealed at reduced pressure (ca. 3 mTorr). 2H NMR line shape simulation revealed an activation barrier for rotation of 11.3 ± 2.0 kcal/mol, which is lower than the 14-16 kcal/mol values reported in theor. studies of truncated models. While our results suggest that the models used for MOF-5 are insufficient to account for the properties of the extended crystal lattice, they also suggest that the amphidynamic materials with static and dynamic components may reach the friction-free rotational motion characteristic of gas dynamics.
- 39Kolokolov, D. I.; Stepanov, A. G.; Guillerm, V.; Serre, C.; Frick, B.; Jobic, H. Probing the Dynamics of the Porous Zr Terephthalate UiO-66 Framework Using 2H NMR and Neutron Scattering. J. Phys. Chem. C 2012, 116 (22), 12131– 12136, DOI: 10.1021/jp3029193Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmvFGgtrk%253D&md5=e819c06b2f2699b620d49d906d429e4dProbing the Dynamics of the Porous Zr Terephthalate UiO-66 Framework Using 2H NMR and Neutron ScatteringKolokolov, D. I.; Stepanov, A. G.; Guillerm, V.; Serre, C.; Frick, B.; Jobic, H.Journal of Physical Chemistry C (2012), 116 (22), 12131-12136CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)2H NMR and quasi-elastic neutron scattering techniques were used to study the rotational dynamics of the 1,4-benzene-dicarboxylate (BDC) linkers in the porous cubic UiO-66(Zr) metal-org. framework (MOF). The rotation of the benzene rings in the BDC linkers is at the limit of detection of the neutron technique, but it fits perfectly on the 2H NMR time scale. The arom. rings in the UiO-66 framework exhibit the lowest rotational barrier compared to other MOFs, the activation energy for π-flips being 30 kJ mol-1. However, instead of having well-defined flipping rates like in MOF-5, MIL-47, or MIL-53, UiO-66(Zr) shows a distribution of flipping correlation times, probably due to local disorder in the structure. Because of the rotational motion of the benzene rings, the effective size of the microporous windows in UiO-66(Zr) appears to be temp. dependent.
- 40Biswas, S.; Ahnfeldt, T.; Stock, N. New Functionalized Flexible Al-MIL-53-X (X = -Cl, -Br, -CH 3, -NO 2, -(OH) 2) Solids: Syntheses, Characterization, Sorption, and Breathing Behavior. Inorg. Chem. 2011, 50 (19), 9518– 9526, DOI: 10.1021/ic201219gGoogle Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtFeksr7J&md5=0d28e50d97d4801ef914d8ccc38da211New Functionalized Flexible Al-MIL-53-X (X = -Cl, -Br, -CH3, -NO2, -(OH)2) Solids: Syntheses, Characterization, Sorption, and Breathing BehaviorBiswas, Shyam; Ahnfeldt, Tim; Stock, NorbertInorganic Chemistry (2011), 50 (19), 9518-9526CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)Five new flexible Al terephthalate deriv. hydroxo frameworks, [Al(OH)(BDC-X)]·n(guests), were prepd. by solvothermal methods [BDC = 1,4-benzene-dicarboxylate; X = 2-chloro (1); 2-bromo (2); 2-Me (3); 2-nitro (4); 2,5-dihydroxy (5)]. The as synthesized (Al-MIL-53-X-AS) as well as the activated compds. were characterized by x-ray powder diffraction (XRPD), IR spectroscopy, thermogravimetric (TG), and elemental anal. Activation, i.e., removal of unreacted H2BDC-X mols. and/or occluded solvent mols., followed by hydration in air at room temp., led to the narrow pore (NP) form of [Al(OH)(BDC-X)]·n(H2O) (Al-MIL-53-X). TGA and temp.-dependent XRPD (TDXRPD) expts. performed on the NP-form of the compds. indicate high thermal stability in the range 325-500°. As verified by N2, CO2, or H2O sorption measurements, most of the thermally activated compds. exhibit significant microporosity. Similar to pristine Al-MIL-53, the present compds. retain their structural flexibility depending on the nature of guest mols. and temp., as verified by cell parameter detn. from XRPD data. The breathing behavior of the functionalized frameworks upon dehydration-rehydration, studied by temp. and time-dependent XRPD measurements, differs significantly compared to parent Al-MIL-53.
- 41Loiseau, T.; Serre, C.; Huguenard, C.; Fink, G.; Taulelle, F.; Henry, M.; Bataille, T.; Férey, G. A Rationale for the Large Breathing of the Porous Aluminum Terephthalate (MIL-53) upon Hydration. Chem. - Eur. J. 2004, 10 (6), 1373– 1382, DOI: 10.1002/chem.200305413Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXivVykt7s%253D&md5=3a01acd738d767103450cccd3cab8f2eA rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydrationLoiseau, Thierry; Serre, Christian; Huguenard, Clarisse; Fink, Gerhard; Taulelle, Francis; Henry, Marc; Bataille, Thierry; Ferey, GerardChemistry - A European Journal (2004), 10 (6), 1373-1382CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)Al 1,4-benzenedicarboxylate Al(OH)[O2CC6H4CO2][HO2C-C6H4-CO2H]0.70 or MIL-53as (Al) was hydrothermally synthesized by heating a mixt. of Al nitrate, 1,4-benzenedicarboxylic acid, and H2O, for three days at 220°. Its 3 D framework is built up of infinite trans chains of corner-sharing AlO4(OH)2 octahedra. The chains are interconnected by the 1,4-benzenedicarboxylate groups, creating 1 D rhombic-shaped tunnels. Disordered 1,4-benzenedicarboxylic acid mols. are trapped inside these tunnels. Their evacuation upon heating, between 275 and 420°, leads to a nanoporous open-framework (MIL-53ht (Al) or Al(OH)[O2CC6H4CO2]) with empty pores of diam. 8.5 Å. This solid exhibits a Langmuir surface area. of 1590(1) m2g-1 together with a remarkable thermal stability, since it starts to decomp. only at 500°. At room temp., the solid reversibly absorbs H2O in its tunnels, causing a very large breathing effect and shrinkage of the pores. Anal. of the hydration process by solid-state NMR (1H, 13C, 27Al) has clearly indicated that the trapped H2O mols. interact with the carboxylate groups through H bonds, but do not affect the hydroxyl species bridging the Al atoms. The H bonds between H2O and the O atoms of the framework are responsible for the contraction of the rhombic channels. The structures of the three forms were detd. by powder x-ray diffraction anal. Crystal data for MIL-53as (Al) are as follows: orthorhombic system, Pnma (no. 62), a 17.129(2), b 6.628(1), c 12.182(1) Å; for MIL-53ht (Al), orthorhombic system, Imma (no. 74), a 6.608(1), b 16.675(3), c 12.813(2) Å; for MIL-53lt (Al), monoclinic system, Cc (no. 9), a 19.513(2), b 7.612(1), c 6.576(1) Å, β 104.24(1)°.
- 42Liu, Y.; Her, J. H.; Dailly, A.; Ramirez-Cuesta, A. J.; Neumann, D. A.; Brown, C. M. Reversible Structural Transition in MIL-53 with Large Temperature Hysteresis. J. Am. Chem. Soc. 2008, 130 (35), 11813– 11818, DOI: 10.1021/ja803669wGoogle Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXps1Knt74%253D&md5=0d06ce91da90c73847b704c1ae49016fReversible Structural Transition in MIL-53 with Large Temperature HysteresisLiu, Yun; Her, Jae-Hyuk; Dailly, Anne; Ramirez-Cuesta, Anibal J.; Neumann, Dan A.; Brown, Craig M.Journal of the American Chemical Society (2008), 130 (35), 11813-11818CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The metal-org. framework, MIL-53, can have a structural transition from an open-pored to a closed-pored structure by adsorbing different guest mols. The aid of guest mols. is believed to be necessary to initiate this "breathing" effect. Using both neutron powder diffraction and inelastic neutron scattering techniques, we find that MIL-53 exhibits a reversible structural transition between an open-pored and a closed-pored structure as a function of temp. without the presence of any guest mols. Surprisingly, this structural transition shows a significant temp. hysteresis: the transition from the open-pored to closed-pored structure occurs at approx. 125 to 150 K, while the transition from the closed-pored to open-pored structure occurs around 325 to 375 K. To our knowledge, this is first observation of such a large temp. hysteresis of a structural transition in metal-org. frameworks. We also note that the transition from the open to closed structure at low temp. shows very slow kinetics. An ab initio computer simulation is employed to investigate the possible mechanism of the transition.
- 43Munn, A. S.; Pillai, R. S.; Biswas, S.; Stock, N.; Maurin, G.; Walton, R. I. The Flexibility of Modified-Linker MIL-53 Materials. Dalt. Trans. 2016, 45 (10), 4162– 4168, DOI: 10.1039/C5DT03438HGoogle ScholarThere is no corresponding record for this reference.
- 44Stavitski, E.; Pidko, E. A.; Couck, S.; Remy, T.; Hensen, E. J. M.; Weckhuysen, B. M.; Denayer, J.; Gascon, J.; Kapteijn, F. Complexity behind CO2 Capture on NH2-MIL-53(Al). Langmuir 2011, 27 (7), 3970– 3976, DOI: 10.1021/la1045207Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXivVShsrc%253D&md5=e9ebca4338eb83c2165b3582601dd610Complexity behind CO2 Capture on NH2-MIL-53(Al)Stavitski, Eli; Pidko, Evgeny A.; Couck, Sarah; Remy, Tom; Hensen, Emiel J. M.; Weckhuysen, Bert M.; Denayer, Joeri; Gascon, Jorge; Kapteijn, FreekLangmuir (2011), 27 (7), 3970-3976CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Some Metal Org. Frameworks (MOFs) show excellent performance in extg. carbon dioxide from different gas mixts. The origin of their enhanced sepn. ability is not clear yet. Herein, the authors present a combined exptl. and theor. study of the amino-functionalized MIL-53(Al) to elucidate the mechanism behind its unusual high efficiency in CO2 capture. Spectroscopic and DFT studies point out only an indirect role of amine moieties. In contrast to other amino-functionalized CO2 sorbents, no chem. bond between CO2 and the NH2 groups of the structure is formed. The functionalization modulates the breathing behavior of the material, i.e., the flexibility of the framework and its capacity to alter the structure upon the introduction of specific adsorbates. The absence of strong chem. interactions with CO2 is of high importance for the overall performance of the adsorbent, since full regeneration can be achieved within minutes under very mild conditions, demonstrating the high potential of this type of adsorbents for PSA like systems.
- 45Shustova, N. B.; Ong, T.-C.; Cozzolino, A. F.; Michaelis, V. K.; Griffin, R. G.; Dinca, M. Phenyl Ring Dynamics in a Tetraphenylethylene-Bridged Metal–Organic Framework: Implications for the Mechanism of Aggregation-Induced Emission. J. Am. Chem. Soc. 2012, 134 (36), 15061– 15070, DOI: 10.1021/ja306042wGoogle Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFOru77O&md5=3b5bb9537c96ed99cf65c5a14bd9ca02Phenyl Ring Dynamics in a Tetraphenylethylene-Bridged Metal-Organic Framework: Implications for the Mechanism of Aggregation-Induced EmissionShustova, Natalia B.; Ong, Ta-Chung; Cozzolino, Anthony F.; Michaelis, Vladimir K.; Griffin, Robert G.; Dinca, MirceaJournal of the American Chemical Society (2012), 134 (36), 15061-15070CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Mols. that exhibit emission in the solid state, esp. those known as aggregation-induced emission (AIE) chromophores, found applications in areas as varied as light-emitting diodes and biol. sensors. Despite numerous studies, the mechanism of fluorescence quenching in AIE chromophores is still not completely understood. To this end, much interest has focused on understanding the low-frequency vibrational dynamics of prototypical systems, such as tetraphenylethylene (TPE), in the hope that such studies would provide more general principles toward the design of new sensors and electronic materials. The authors hereby show that a perdeuterated TPE-based metal-org. framework (MOF) serves as an excellent platform for studying the low-energy vibrational modes of AIE-type chromophores. In particular, the authors use solid-state 2H and 13C NMR expts. to study the Ph ring dynamics of TPE cores that are coordinatively trapped inside a MOF and find a Ph ring flipping energy barrier of 43(6) kJ/mol. DFT calcns. are then used to deconvolute the electronic and steric contributions to this flipping barrier. Finally, the authors couple the NMR and DFT studies with variable-temp. x-ray diffraction expts. to propose that both the ethylenic C=C bond twist and the torsion of the Ph rings are important for quenching emission in TPE, but that the former may gate the latter. To conclude, the authors use these findings to propose a set of design criteria for the development of tunable turn-on porous sensors constructed from AIE-type mols., particularly as applied to the design of new multifunctional MOFs.
- 46Kolokolov, D. I.; Stepanov, A. G.; Jobic, H. SI: Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene Loadings. J. Phys. Chem. C 2014, 118 (29), 15978– 15984, DOI: 10.1021/jp506010pGoogle Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVOjt7jF&md5=762caac7292523f0c2ba3d043f5dd359Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene LoadingsKolokolov, Daniil I.; Stepanov, Alexander G.; Jobic, HerveJournal of Physical Chemistry C (2014), 118 (29), 15978-15984CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Large pore (LP) and narrow pore (NP) cryst. state interconversions of the MIL-53(Al) MOF framework has been monitored via following the thermally induced evolution of phenylene fragments using 2H solid-state NMR. The dynamics of phenylene fragments was shown to be very sensitive to the loading of xylene guests and the MOF structural state. The mol. rotation rate was higher and the activation barrier lower for the LP state of the guest-free or loosely loaded material, whereas the NP and LP states with high loadings and dense guest packing showed a decrease of the rotation rates and increase of the rotation energetic barrier.
- 47Balčiu̅nas, S.; Simenas, M.; Pavlovaite, D.; Kinka, M.; Shieh, F.-K.; Wu, K. C.-W.; Banys, J.; Grigalaitis, R. Low-Frequency Dipolar Dynamics and Atmospheric Effects in ZIF-90 Metal–Organic Framework. J. Phys. Chem. C 2019, 123 (1), 631– 636, DOI: 10.1021/acs.jpcc.8b10862Google Scholar47https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisVOit73E&md5=81b6cf58596a76cfd3fc13c2eab07703Low-Frequency Dipolar Dynamics and Atmospheric Effects in ZIF-90 Metal-Organic FrameworkBalciunas, Sergejus; Simenas, Mantas; Pavlovaite, Diana; Kinka, Martynas; Shieh, Fa-Kuen; Wu, Kevin C.-W.; Banys, Juras; Grigalaitis, RobertasJournal of Physical Chemistry C (2019), 123 (1), 631-636CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Remarkable gas adsorption properties of zeolitic imidazolate frameworks (ZIFs) are believed to be tightly related to a flexible nature of org. linkers in these compds. We present a low-frequency dielec. spectroscopy study of dynamic effects in a ZIF-90 hybrid compd. Expts. of dehydrated framework reveal slow motion of the imidazolate-2-carboxyaldehyde linker in the kilohertz frequency range. Measurements of hydrated compd. indicate two addnl. dynamic processes related to the adsorbed water mols. These processes are assigned to the proton cond. and relaxation of the supercooled water confined within the pores of the framework. We also study linker dynamics of dehydrated ZIF-90 in vacuum and under different gas atms., revealing that the linker motion is significantly hindered by the guest mols.
- 48Winston, E. B.; Lowell, P. J.; Vacek, J.; Chocholoušová, J.; Michl, J.; Price, J. C. Dipolar Molecular Rotors in the Metal–Organic Framework Crystal IRMOF-2. Phys. Chem. Chem. Phys. 2008, 10 (34), 5188, DOI: 10.1039/b808104bGoogle Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtVektLnK&md5=19b1e4689972550860e27fa3aa5874deDipolar molecular rotors in the metal-organic framework crystal IRMOF-2Winston, Erick B.; Lowell, Peter J.; Vacek, Jaroslav; Chocholousova, Jana; Michl, Josef; Price, John C.Physical Chemistry Chemical Physics (2008), 10 (34), 5188-5191CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Rotating polar linker groups in the cubic metal-org. framework single crystal known as IRMOF-2 were studied for freedom of motion, response to an external elec. field, and effects of dipole-dipole interactions. The crystals consist of octahedrally coordinated zinc oxide clusters linked by the bromoterephthalate group, which contains a rotatable bromo-p-phenylene moiety. The authors confirmed the rotation by dielec. spectroscopy and found a 7.3 kcal mol-1 barrier. The nonpolar analog, IRMOF-1, contg. terephthalic acid, was used as a control system. DFT and MP2 computations of the rotational barrier yield results in agreement with the observation, with B3LYP/SDD being the best. A Monte Carlo anal. of the equil. polarization fluctuations was used to assess the possibility of polar ordering and the potential for electrooptic applications.
- 49Devautour-Vinot, S.; Maurin, G.; Serre, C.; Horcajada, P.; Paula Da Cunha, D.; Guillerm, V.; De Souza Costa, E.; Taulelle, F.; Martineau, C. Structure and Dynamics of the Functionalized MOF Type UiO-66(Zr): NMR and Dielectric Relaxation Spectroscopies Coupled with DFT Calculations. Chem. Mater. 2012, 24 (11), 2168– 2177, DOI: 10.1021/cm300863cGoogle Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XntlOgu7Y%253D&md5=371fdbbaaaede06ced5e363fd614e4f2Structure and Dynamics of the Functionalized MOF Type UiO-66(Zr): NMR and Dielectric Relaxation Spectroscopies Coupled with DFT CalculationsDevautour-Vinot, Sabine; Maurin, Guillaume; Serre, Christian; Horcajada, Patricia; Paula da Cunha, Denise; Guillerm, Vincent; de Souza Costa, Elisangela; Taulelle, Francis; Martineau, CharlotteChemistry of Materials (2012), 24 (11), 2168-2177CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Advanced 1- and 2-dimensional high-field and ultrafast MASNMR measurements were conducted in tandem with DFT calcns. for the NMR parameters to deeply characterize the local environment and the long-range structure order of the porous metal-org. framework (MOF) type UiO-66(Zr) (UiO for University of Oslo) functionalized by polar -Br, -2OH, and -NH2 groups. Such an innovative combining approach applied to the complex architecture of MOFs was revealed successful not only to unambiguously assign all the NMR signals to the corresponding crystallog. sites but also to validate the crystal structures for each functionalized material that were only predicted so far. A further step consisted of probing the impact of the grafted functions on the ligand dynamics of these MOFs by dielec. relaxation spectroscopy measurements. It was evidenced that the rotational motion of the org. linker requires overpassing an energy barrier that strongly depends on the functional groups, the -NH2 functionalized version implying the highest activation energy. Such a finding was further explained by the relatively strong intraframework interactions which take place between the grafted function and the inorg. node as suggested by the anal. of the corresponding simulated crystal structure.
- 50Kremer, A.; Schönhals, F. Theory of Dielectric Relaxation. In Broadband Dielectric Spectroscopy; Springer-Verlag: Berlin Heidelberg, 2003; pp 1– 33. DOI: 10.1007/978-3-642-56120-7_1 .Google ScholarThere is no corresponding record for this reference.
- 51Frunza, S.; Schönhals, A.; Frunza, L.; Ganea, P.; Kosslick, H.; Harloff, J.; Schulz, A. Molecular Relaxation Processes in a MOF-5 Structure Revealed by Broadband Dielectric Spectroscopy: Signature of Phenylene Ring Fluctuations. J. Phys. Chem. B 2010, 114 (40), 12840– 12846, DOI: 10.1021/jp1071617Google Scholar51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtFKlu77F&md5=86c3ccbb9f1e84ee565cd29ce800ce34Molecular Relaxation Processes in a MOF-5 Structure Revealed by Broadband Dielectric Spectroscopy: Signature of Phenylene Ring FluctuationsFrunza, Stefan; Schoenhals, Andreas; Frunza, Ligia; Ganea, Paul; Kosslick, Hendrik; Harloff, Joerg; Schulz, AxelJournal of Physical Chemistry B (2010), 114 (40), 12840-12846CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)The mol. mobility of a MOF-5 metal-org. framework was investigated by broadband dielec. spectroscopy. Three relaxation processes were revealed. The temp. dependence of their relaxation rates follows an Arrhenius law. The process obsd. at lower temps. is attributed to bending fluctuations of the edges of the cages involving the Zn-O clusters. The processes ("region II") at higher temps. were assigned to fluctuations of Ph rings in agreement with the NMR data found by Gould et al. The carboxylate groups might also be involved. The rotational fluctuations of the Ph rings leading to the low frequency part of relaxation region II might be hindered either by some solvent mols. entrapped in the cages or by an interpenetrated structure and have a broad distribution of activation energies. The high frequency part of region II corresponds nearly to a Debye-like process: This is explained by a well-defined structure of empty pores.
- 52Knebel, A.; Geppert, B.; Volgmann, K.; Kolokolov, D. I.; Stepanov, A. G.; Twiefel, J.; Heitjans, P.; Volkmer, D.; Caro, J. Defibrillation of Soft Porous Metal-Organic Frameworks with Electric Fields. Science 2017, 358 (6361), 347– 351, DOI: 10.1126/science.aal2456Google Scholar52https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1Kns7%252FE&md5=65943f86316595f45313607e789d3d52Defibrillation of soft porous metal-organic frameworks with electric fieldsKnebel, A.; Geppert, B.; Volgmann, K.; Kolokolov, D. I.; Stepanov, A. G.; Twiefel, J.; Heitjans, P.; Volkmer, D.; Caro, J.Science (Washington, DC, United States) (2017), 358 (6361), 347-351CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Gas transport through metal-org. framework membranes (MOFs) was switched in situ by applying an external elec. field (E-field). The switching of gas permeation upon E-field polarization could be explained by the structural transformation of the zeolitic imidazolate framework ZIF-8 into polymorphs with more rigid lattices. Permeation measurements under a direct-current E-field poling of 500 V per mm showed reversibly controlled switching of the ZIF-8 into polar polymorphs, which was confirmed by x-ray diffraction and ab initio calcns. The stiffening of the lattice causes a redn. in gas transport through the membrane and sharpens the mol. sieving capability. Dielec. spectroscopy, polarization, and deuterium NMR studies revealed low-frequency resonances of ZIF-8 that we attribute to lattice flexibility and linker movement. Upon E-field polarization, we obsd. a defibrillation of the different lattice motions.
- 53Horansky, R. D.; Clarke, L. I.; Price, J. C.; Khuong, T. A. V; Jarowski, P. D.; Garcia-Garibay, M. A. Dielectric Response of a Dipolar Molecular Rotor Crystal. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72 (1), 1– 5, DOI: 10.1103/PhysRevB.72.014302Google ScholarThere is no corresponding record for this reference.
- 54Horansky, R. D.; Clarke, L. I.; Winston, E. B.; Price, J. C.; Karlen, S. D.; Jarowski, P. D.; Santillan, R.; Garcia-Garibay, M. A. Dipolar Rotor-Rotor Interactions in a Difluorobenzene Molecular Rotor Crystal. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 74 (5), 1– 12, DOI: 10.1103/PhysRevB.74.054306Google ScholarThere is no corresponding record for this reference.
- 55Jiang, X.; O’Brien, Z. J.; Yang, S.; Lai, L. H.; Buenaflor, J.; Tan, C.; Khan, S.; Houk, K. N.; Garcia-Garibay, M. A. Crystal Fluidity Reflected by Fast Rotational Motion at the Core, Branches, and Peripheral Aromatic Groups of a Dendrimeric Molecular Rotor. J. Am. Chem. Soc. 2016, 138 (13), 4650– 4656, DOI: 10.1021/jacs.6b01398Google Scholar55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XktFejsrs%253D&md5=fbf49fbb0235f2e9a0b05a30b24f87d3Crystal Fluidity Reflected by Fast Rotational Motion at the Core, Branches, and Peripheral Aromatic Groups of a Dendrimeric Molecular RotorJiang, Xing; O'Brien, Zachary J.; Yang, Song; Lai, Lan Huong; Buenaflor, Jeffrey; Tan, Colleen; Khan, Saeed; Houk, K. N.; Garcia-Garibay, Miguel A.Journal of the American Chemical Society (2016), 138 (13), 4650-4656CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Low packing densities are key structural features of amphidynamic crystals built with static and mobile components. Here we report a loosely packed crystal of dendrimeric rotor 2 (I) and the fast dynamics of all its arom. groups, both resulting from the hyperbranched structure of the mol. Compd. 2 was synthesized with a convergent strategy to construct a central phenylene core with stators consisting of two layers of triarylmethyl groups. Single crystal X-ray diffraction anal. confirmed a low-d. packing structure consisting of one mol. of 2 and approx. eight solvent mols. per unit cell. Three isotopologues of 2 were synthesized to study the motion of each segment of the mol. in the solid state using variable temp. quadrupolar echo 2H NMR spectroscopy. Line shape anal. of the spectra reveals that the central phenylene, the six branch phenylenes, and the 18 periphery phenyls all display megahertz rotational dynamics in the crystals at ambient temp. Arrhenius anal. of the data gives similar activation energies and pre-exponential factors for different parts of the structure. The obsd. pre-exponential factors are 4-6 orders of magnitude greater than those of elementary site-exchange processes, indicating that the dynamics are not dictated by static energetic potentials. Instead, the activation energies for rotations in the crystals of 2 are controlled by temp. dependent local structural fluctuations and crystal fluidity.
- 56Hansen, M. R.; Graf, R.; Spiess, H. W. Solid-State NMR in Macromolecular Systems: Insights on How Molecular Entities Move. Acc. Chem. Res. 2013, 46 (9), 1996– 2007, DOI: 10.1021/ar300338bGoogle Scholar56https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjvVKku7g%253D&md5=273ff0f58be4bacb773abcaf5a2b37e3Solid-State NMR in Macromolecular Systems: Insights on How Molecular Entities MoveHansen, Michael Ryan; Graf, Robert; Spiess, Hans WolfgangAccounts of Chemical Research (2013), 46 (9), 1996-2007CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. The function of synthetic and natural macromol. systems critically depends on the packing and dynamics of the individual components of a given system. Not only can solid-state NMR provide structural information with at. resoln., but it can also provide a way to characterize the amplitude and time scales of motions over broad ranges of length and time. These movements include mol. dynamics, rotational and translational motions of the building blocks, and also the motion of the functional species themselves, such as protons or ions. This Account examines solid-state NMR methods for correlating dynamics and function in a variety of chem. systems. In the early days, scientists thought that the rotational motions reflected the geometry of the moving entities. They described these phenomena as jumps about well-defined axes, such as Ph flips, even in amorphous polymers. Later, they realized that conformational transitions in macromols. happen in a much more complex way. Because the individual entities do not rotate around well-defined axes, they require much less space. Only recently researchers have appreciated the relative importance of large angle fluctuations of polymers over rotational jumps. Researchers have long considered that cooperative motions might be at work, yet only recently they have clearly detected these motions by NMR in macromol. and supramol. systems. In correlations of dynamics and function, local motions do not always provide the mechanism of long-range transport. This idea holds true in ion conduction but also applies to chain transport in polymer melts and semicryst. polymers. Similar chain motions and ion transport likewise occur in functional biopolymers, systems where solid-state NMR studies are also performed. In polymer science, researchers have appreciated the unique information on mol. dynamics available from advanced solid-state NMR at times, where their colleagues in the biomacromol. sciences have emphasized structure. By contrast, following X-ray crystallographers, researchers studying proteins using soln. NMR introduced the combination of NMR with computer simulation before that became common practice in solid-state NMR. Today's simulation methods can handle partially ordered or even disordered systems common in synthetic polymers. Thus, the multitechnique approaches employed in NMR of synthetic and biol. macromols. have converged. Therefore, this Account will be relevant to both researchers studying synthetic macromol. and supramol. systems and those studying biol. complexes.
- 57Spiess, H. W. Molecular Dynamics of Solid Polymers as Revealed by Deuteron NMR. Colloid Polym. Sci. 1983, 261, 193– 209, DOI: 10.1007/BF01469664Google Scholar57https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3sXhvFyqsLw%253D&md5=9f278078daad59f05ce3d9189264deecMolecular dynamics of solid polymers as revealed by deuteron NMRSpiess, H. W.Colloid and Polymer Science (1983), 261 (3), 193-209CODEN: CPMSB6; ISSN:0303-402X.A review with 92 refs.
- 58Khudozhitkov, A. E.; Jobic, H.; Freude, D.; Haase, J.; Kolokolov, D. I.; Stepanov, A. G. Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of Xylene. J. Phys. Chem. C 2016, 120 (38), 21704– 21709, DOI: 10.1021/acs.jpcc.6b08114Google Scholar58https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVWntLrF&md5=81e4e92ea30a9e9c0e5fac8125a46fc8Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of XyleneKhudozhitkov, Alexander E.; Jobic, Herve; Freude, Dieter; Haase, Juergen; Kolokolov, Daniil I.; Stepanov, Alexander G.Journal of Physical Chemistry C (2016), 120 (38), 21704-21709CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)MIL-53 (Al) is an important example of metal-org. frameworks (MOFs) with a flexible framework capable to efficiently sep. ortho and para isomers of xylene at moderate temps. The MIL-53 MOF contains mobile terephthalate phenylene fragments that can be used as a dynamic probe to study the guest-host interactions and the origin of the sepn. selectivity. Here 2H NMR spin alignment echo technique for the 1st time was applied to probe ultraslow structural mobility (0.1-1 kHz) in MOFs materials, with particular application to MIL-53(Al) satd. with ortho or para isomers of xylene. A specific influence of different isomers of xylene adsorbed in the MOF pores on the rotation of the phenylenes in MIL-53 for the temp. range with proved sepn. selectivity (T < 393 K) is shown. The rotation of phenylene fragments is sensitive to the type of xylene isomer. The phenylenes' rotation performs 1 order of magnitude slower in the presence of o-xylene (kortho = 70 s-1) compared to the same rotation in the presence of the other isomer, p-xylene (kpara = 800 s-1) at T ∼ 373 K. This is rationalized by a stronger interaction of the ortho isomer with the linker than the para isomer. This finding offers an understanding of the mol. mechanism of p- and o-xylene sepn. by MIL-53: stronger interaction of o-xylene with org. linker compared to p-xylene provides sepn. of these isomers on MIL-53.
- 59Serra-Crespo, P.; Van Der Veen, M. A.; Gobechiya, E.; Houthoofd, K.; Filinchuk, Y.; Kirschhock, C. E. A.; Martens, J. A.; Sels, B. F.; De Vos, D. E.; Kapteijn, F.; Gascon, J. NH2-MIL-53(Al): A High-Contrast Reversible Solid-State Nonlinear Optical Switch. J. Am. Chem. Soc. 2012, 134 (20), 8314– 8317, DOI: 10.1021/ja300655fGoogle Scholar59https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmvV2nsLY%253D&md5=5c2d17972ea8024a717a721f608e0d2cNH2-MIL-53(Al): A High-Contrast Reversible Solid-State Nonlinear Optical SwitchSerra-Crespo, Pablo; van der Veen, Monique A.; Gobechiya, Elena; Houthoofd, Kristof; Filinchuk, Yaroslav; Kirschhock, Christine E. A.; Martens, Johan A.; Sels, Bert F.; De Vos, Dirk E.; Kapteijn, Freek; Gascon, JorgeJournal of the American Chemical Society (2012), 134 (20), 8314-8317CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The metal-org. framework NH2-MIL-53(Al) is the 1st solid-state material displaying nonlinear optical switching due to a conformational change upon breathing. A switching contrast of at least 38 was obsd. This transition originates in the restrained linker mobility in the very narrow pore configuration.
- 60Spiess, H. W. Deuteron NMR — a New Tool for Studying Chain Mobility and Orientation in Polymers. In Characterization of Polymers in the Solid State I: Part A: NMR and Other Spectroscopic Methods Part B: Mechanical Methods.; Kaush, H. H., Zachman, H. G., Eds.; Springer: Berlin, Heidelberg, 1985; pp 23– 58. DOI: 10.1007/3-540-13779-3_16 .Google ScholarThere is no corresponding record for this reference.
- 61Gedat, E.; Schreiber, A.; Albrecht, J.; Emmler, T.; Shenderovich, I.; Findenegg, G. H.; Limbach, H. H.; Buntkowsky, G. 2H-Solid-State NMR Study of Benzene-D6confined in Mesoporous Silica SBA-15. J. Phys. Chem. B 2002, 106 (8), 1977– 1984, DOI: 10.1021/jp012391pGoogle Scholar61https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XptVOltA%253D%253D&md5=546d984bf2aa7c18812adb7304eaf8aa2H-Solid-State NMR Study of Benzene-d6 Confined in Mesoporous Silica SBA-15Gedat, E.; Schreiber, A.; Albrecht, J.; Emmler, Th.; Shenderovich, I.; Findenegg, G. H.; Limbach, H.-H.; Buntkowsky, G.Journal of Physical Chemistry B (2002), 106 (8), 1977-1984CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)Benzene-d6 confined in the hexagonal ordered cylindrical pores of mesoporous silica SBA-15 (pore diam. 8.0 nm) was studied by low-temp. 2H-solid-state NMR spectroscopy at 236-19 K and compared to bulk benzene-d6. The solid-state spectra of the bulk benzene-d6 exhibit quadrupolar Pake patterns at high and low temps., and in the intermediate temp. regime the typical line shape changes caused by rotational jumps around the 6-fold axis. At all temps. the benzene mols. are characterized by a single rotational correlation time. For benzene-d6 confined in SBA-15, however, these exchange dominated line shapes are not found. At all temps. below the f.p. the spectra of benzene in the silica show the coexistence of two states with temp.-dependent intensity ratios. This behavior is the result of a Gaussian distributions of activation energies for the rotational jumps inside the pores. For the solid I-solid II (fast 6-fold jump to slow 6-fold jump) transition the center of the distribution is at 40 K (6.0 kJ/mol) with a width of 19.5 K (2.9 kJ/mol). For the liq.-solid I (liq.-like to fast 6-fold jump) transition the center of the distribution is at 204 K (30.6 kJ/mol) and the width is 15 K (2.2 kJ/mol). From the pore vol. and the filling factor, a thickness of four mol. layers of this surface phase is estd.
- 62Larsen, F. H. Simulation of Molecular Motion of Quadrupolar Nuclei in Solid-State NMR Spectra. In Annu. Rep. NMR Spectrosc.; Elsevier Ltd, 2010; Vol. 71, pp 103– 137. DOI: 10.1016/B978-0-08-089054-8.00004-6 .Google ScholarThere is no corresponding record for this reference.
- 63Aliev, A. E.; Mann, S. E.; Rahman, A. S.; McMillan, P. F.; Cora, F.; Iuga, D.; Hughes, C. E.; Harris, K. D. M. High-Resolution Solid-State H-2 NMR Spectroscopy of Polymorphs of Glycine. J. Phys. Chem. A 2011, 115 (44), 12201– 12211, DOI: 10.1021/jp207592uGoogle Scholar63https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlWjtbzK&md5=e8068019ea5b9937d275e3d4f7959357High-Resolution Solid-State 2H NMR Spectroscopy of Polymorphs of GlycineAliev, Abil E.; Mann, Sam E.; Rahman, Aisha S.; McMillan, Paul F.; Cora, Furio; Iuga, Dinu; Hughes, Colan E.; Harris, Kenneth D. M.Journal of Physical Chemistry A (2011), 115 (44), 12201-12211CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)High-resoln. solid-state 2H MAS NMR studies of the α and γ polymorphs of fully deuterated glycine (glycine-d5) are reported. Anal. of spinning sideband patterns is used to det. the 2H quadrupole interaction parameters, and is shown to yield good agreement with the corresponding parameters detd. from single-crystal 2H NMR measurements (the max. deviation in quadrupole coupling consts. detd. from these two approaches is only 1%). From anal. of simulated 2H MAS NMR sideband patterns as a function of reorientational jump frequency (κ) for the -N+D3 group in glycine-d5, the exptl. obsd. differences in the 2H MAS NMR spectrum for the -N+D3 deuterons in the α and γ polymorphs is attributed to differences in the rate of reorientation of the -N+D3 group. These simulations show severe broadening of the 2H MAS NMR signal in the intermediate motion regime, suggesting that deuterons undergoing reorientational motions at rates in the range κ ≈ 104-106 s-1 are likely to be undetectable in 2H MAS NMR measurements for materials with natural isotopic abundances. The 1H NMR chem. shifts for the α and γ polymorphs of glycine have been detd. from the 2H MAS NMR results, taking into account the known second-order shift. Further quantum mech. calcns. of 2H quadrupole interaction parameters and 1H chem. shifts reveal the structural dependence of these parameters in the two polymorphs and suggest that the existence of two short intermol. C-H···O contacts for one of the H atoms of the >CH2 group in the α polymorph have a significant influence on the 2H quadrupole coupling and 1H chem. shift for this site.
- 64Schadt, R. J.; Cain, E. J.; English, A. D. Simulation of One-Dimensional Deuteron NMR Line Shapes. J. Phys. Chem. 1993, 97 (32), 8387– 8392, DOI: 10.1021/j100134a005Google Scholar64https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXlslalsL0%253D&md5=2413c9162dc27432baba2cef71c2b6d0Simulation of one-dimensional deuteron NMR line shapesSchadt, R. J.; Cain, E. J.; English, A. D.Journal of Physical Chemistry (1993), 97 (32), 8387-92CODEN: JPCHAX; ISSN:0022-3654.The detn. of the mol. mechanics involved in a bond reorientation process from the simulation of 1-dimensional 2H NMR spectra is considered for a variety of models. Anisotropic line shape distortions and the accompanying refocusing efficiency factors are essential in identifying the general characteristics of the motional process. The utility of employing a basis set of simulations for an initial anal. of exptl. data where a distribution of correlation times is required to fit the exptl. data is illustrated for the 120° jump or π-flip model.
- 65Leisen, J.; Ohlemacher, A.; Boeffel, C.; Spiess, H. W. Molecular Dynamics in Side-Group Polymers with and without Liquid Crystalline Phases from 2H NMR. Berichte der Bunsengesellschaft für Phys. Chemie 1993, 97 (10), 1306– 1311, DOI: 10.1002/bbpc.19930971019Google ScholarThere is no corresponding record for this reference.
- 66Pschorn, U.; Spiess, H. W.; Hisgen, B.; Ringsdorf, H. Deuteron NMR Study of Molecular Order and Motion of the Mesogenic Side Groups in Liquid-crystalline Polymers. Makromol. Chem. 1986, 187 (11), 2711– 2723, DOI: 10.1002/macp.1986.021871121Google Scholar66https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXjtlOjtw%253D%253D&md5=e4dc35a1e6377b7c71e96cf8b82bb954Deuteron NMR study of molecular order and motion of the mesogenic side groups in liquid-crystalline polymersPschorn, Uwe; Spiess, Hans Wolfgang; Hisgen, Bernd; Ringsdorf, HelmutMakromolekulare Chemie (1986), 187 (11), 2711-23CODEN: MACEAK; ISSN:0025-116X.The mol. order and mobility of 2 liq.-cryst. polyacrylates with Ph benzoate moieties as mesogenic side groups and (CH2)m spacers (m = 2, 6) were investigated by pulsed 2H NMR. The mesogenic side groups were isotopically labeled at the terminal phenylene ring. In the glassy state the orientational distribution function was characterized from the angular dependence of the 2H NMR line shape of samples macroscopically ordered in their nematic phase by the 8.4 T magnetic field of an NMR spectrometer. It was Gaussian with widths of ±18.5° and ±10.5° for the m = 2 frozen nematic and m = 6 frozen smectic system, resp. The phenylene rings undergo 180° jumps about their local C2-axes in the glassy state. The time-scale of this process, however, was not uniform. Instead, the anal. of 2H NMR line shapes and their intensities as a function of temp. yielded a log-Gaussian distribution with correlation times characteristic of amorphous solids, 2.2 vs. 2.5 decades in width and mean activation energy 42 vs. 47 kJ/mol for the m = 2 and m = 6 system, resp. The correlation times for the center of the distribution agree with thoseobtained by dielec. relaxation measurements of the same systems, suggesting that reorientation of the whole mesogenic group is detected via the phenylene rings.
- 67Wehrle, M.; Hellmann, G. P.; Spiess, H. W. Phenylene Motion in Polycarbonate and Polycarbonate/Additive Mixtures. Colloid Polym. Sci. 1987, 265 (9), 815– 822, DOI: 10.1007/BF01418458Google Scholar67https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXmtFygt7k%253D&md5=850347857a2c6752c224607c71f2ea3cPhenylene motion in polycarbonate and polycarbonate/additive mixturesWehrle, M.; Hellmann, G. P.; Spiess, H. W.Colloid and Polymer Science (1987), 265 (9), 815-22CODEN: CPMSB6; ISSN:0303-402X.The large angle motions of phenylene groups in bisphenol A polycarbonate as detd. by pulsed deuterium NMR were related to the β-relaxation since both processes occurred on comparable time scales with similar activation energies and were suppressed by low-mol.-wt. additives (1,4-dichlorobenzene and PCB). The motional mechanism involved π-flips about the C1C4 axis augmented by small-angle fluctuations about the same axis, reaching a root-mean-square amplitude of ±35° at 380 K. The distribution of correlation times for the π-flips was heterogeneous in nature and could be described by either a log-Gaussian or an asym. distribution with a more rapid decay at high correlation times comparable to the Williams-Watts distribution. An av. activation energy of 37 kJ/mol was obtained for both distributions, whereas the temp.-dependent width of the highly asym. distribution was smaller than that of the log-Gaussian distribution.
- 68O’Dell, L. A.; Ratcliffe, C. I. Quadrupolar NMR to Investigate Dynamics in Solid Materials. In Encyclopedia of Magnetic Resonance; Harris, R. K., Wasylishen, R. E., Ed.; John Wiley & Sons, Ltd: Chichester, UK, 2012; pp 3814– 3829. DOI: 10.1002/9780470034590.emrstm1209 .Google ScholarThere is no corresponding record for this reference.
- 69Moreau, F.; Kolokolov, D. I.; Stepanov, A. G.; Easun, T. L.; Dailly, A.; Lewis, W.; Blake, A. J.; Nowell, H.; Lennox, M. J.; Besley, E.; Yang, S.; Schröder, M. Tailoring Porosity and Rotational Dynamics in a Series of Octacarboxylate Metal-Organic Frameworks. Proc. Natl. Acad. Sci. U. S. A. 2017, 114 (12), 3056– 3061, DOI: 10.1073/pnas.1615172114Google Scholar69https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjvF2htb8%253D&md5=0fe2e469dee33a4a805fad9646e48da0Tailoring porosity and rotational dynamics in a series of octacarboxylate metal-organic frameworksMoreau, Florian; Kolokolov, Daniil I.; Stepanov, Alexander G.; Easun, Timothy L.; Dailly, Anne; Lewis, William; Blake, Alexander J.; Nowell, Harriott; Lennox, Matthew J.; Besley, Elena; Yang, Sihai; Schroder, MartinProceedings of the National Academy of Sciences of the United States of America (2017), 114 (12), 3056-3061CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Modulation and precise control of porosity of metal-org. frameworks (MOFs) is of crit. importance to their materials function. Here the authors report modulation of porosity for a series of isoreticular octacarboxylate MOFs, denoted MFM-180 to MFM-185, via a strategy of selective elongation of metal-org. cages. The pseudomonomer of MFM-181 (2) can be presented as Cu4L1(H2O)4 (I). Owing to the high ligand connectivity, these MOFs do not show interpenetration, and are robust structures that have permanent porosity. Activated MFM-185a shows a high Brunauer-Emmett-Teller (BET) surface area of 4734 m2 g-1 for an octacarboxylate MOF. These MOFs show remarkable CH4 and CO2 adsorption properties, notably with simultaneously high gravimetric and volumetric deliverable CH4 capacities of 0.24 g g-1 and 163 vol/vol (298 K, 5-65 bar) recorded for MFM-<185≥a due to selective elongation of tubular cages. The dynamics of mol. rotors in deuterated MFM-180a-d16 and MFM-181a-d16 were studied by variable-temp. 2H solid-state NMR spectroscopy to reveal the reorientation mechanisms within these materials. Anal. of the flipping modes of the mobile Ph groups, their rotational rates, and transition temps. paves the way to controlling and understanding the role of mol. rotors through design of org. linkers within porous MOF materials.
- 70Haigis, V.; Coudert, F.-X.; Vuilleumier, R.; Boutin, A.; Fuchs, A. H. Hydrothermal Breakdown of Flexible Metal–Organic Frameworks: A Study by First-Principles Molecular Dynamics. J. Phys. Chem. Lett. 2015, 6 (21), 4365– 4370, DOI: 10.1021/acs.jpclett.5b01926Google Scholar70https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhs1Ogu7fM&md5=6573bcfba2cd5ccba6ce44c50cef7d97Hydrothermal Breakdown of Flexible Metal-Organic Frameworks: A Study by First-Principles Molecular DynamicsHaigis, Volker; Coudert, Francois-Xavier; Vuilleumier, Rodolphe; Boutin, Anne; Fuchs, Alain H.Journal of Physical Chemistry Letters (2015), 6 (21), 4365-4370CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Flexible metal-org. frameworks, also known as soft porous crystals, have been proposed for a vast no. of technol. applications, because they respond by large changes in structure and properties to small external stimuli, such as adsorption of guest mols. and changes in temp. or pressure. While this behavior is highly desirable in applications such as sensing and actuation, their extreme flexibility can also be synonymous with decreased stability. In particular, their performance in industrial environments is limited by a lack of stability at elevated temps. and in the presence of water. Here, we use first-principles mol. dynamics to study the hydrothermal breakdown of soft porous crystals. Focusing on the material MIL-53(Ga), we show that the weak point of the structure is the bond between the metal center and the org. linker and elucidate the mechanism by which water lowers the activation free energy for the breakdown. This allows us to propose strategies for the synthesis of MOFs with increased heat and water stability.
- 71Gaillac, R.; Pullumbi, P.; Beyer, K. A.; Chapman, K.; Keen, D. A.; Bennett, T. D.; Coudert, F.-X. Liquid Metal–Organic Frameworks. Nat. Mater. 2017, 16 (11), 1149– 1155, DOI: 10.1038/nmat4998Google Scholar71https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1aisr3L&md5=fee166600501104fba7d0f4712e6a9e5Liquid metal-organic frameworksGaillac, Romain; Pullumbi, Pluton; Beyer, Kevin A.; Chapman, Karena W.; Keen, David A.; Bennett, Thomas D.; Coudert, Francois-XavierNature Materials (2017), 16 (11), 1149-1154CODEN: NMAACR; ISSN:1476-1122. (Nature Research)Metal-org. frameworks (MOFs) are a family of chem. diverse materials, with applications in a wide range of fields, covering engineering, physics, chem., biol. and medicine. Until recently, research has focused almost entirely on cryst. structures, yet now a clear trend is emerging, shifting the emphasis onto disordered states, including 'defective by design' crystals, as well as amorphous phases such as glasses and gels. Here the authors introduce a strongly assocd. MOF liq., obtained by melting a zeolitic imidazolate framework, ZIF-4 and ZIF-8. The authors combine in situ variable temp. x-ray, ex situ neutron pair distribution function expts., and first-principles mol. dynamics simulations to study the melting phenomenon and the nature of the liq. obtained. The authors demonstrate from structural, dynamical, and thermodynamical information that the chem. configuration, coordinative bonding, and porosity of the parent cryst. framework survive upon formation of the MOF liq.
Cited By
Smart citations by scite.ai include citation statements extracted from the full text of the citing article. The number of the statements may be higher than the number of citations provided by ACS Publications if one paper cites another multiple times or lower if scite has not yet processed some of the citing articles.
This article is cited by 25 publications.
- Srinidhi Mula, Joris Bierkens, Louis Vanduyfhuys, Monique A. van der Veen. Long-Range and Coupled Rotor Dynamics in NO2-MIL-53(Al) by Classical Molecular Dynamics. The Journal of Physical Chemistry C 2024, 128
(47)
, 20264-20274. https://doi.org/10.1021/acs.jpcc.4c05851
- Gavin A. McCarver, Morgan J. Kramer, Taner Yildirim, Wei Zhou. Unraveling Thermally Regulated Gating Mechanisms in TPT Pore-Partitioned MOF-74: A Computational Endeavor. Chemistry of Materials 2024, 36
(16)
, 8098-8106. https://doi.org/10.1021/acs.chemmater.4c01699
- Marzena Rams-Baron, Alfred Błażytko, Maria Książek, Joachim Kusz, Marian Paluch. Internal Secondary Relaxation as a Dielectric Probe of Molecular Surroundings. The Journal of Physical Chemistry Letters 2024, 15
(9)
, 2595-2600. https://doi.org/10.1021/acs.jpclett.4c00128
- Mingoo Jin, Ryunosuke Kitsu, Natsumi Hammyo, Ayana Sato-Tomita, Motohiro Mizuno, Alexander S. Mikherdov, Mikhail Tsitsvero, Andrey Lyalin, Tetsuya Taketsugu, Hajime Ito. A Steric-Repulsion-Driven Clutch Stack of Triaryltriazines: Correlated Molecular Rotations and a Thermoresponsive Gearshift in the Crystalline Solid. Journal of the American Chemical Society 2023, 145
(50)
, 27512-27520. https://doi.org/10.1021/jacs.3c08909
- Shubha S. Gunaga, David L. Bryce. Modulation of Rotational Dynamics in Halogen-Bonded Cocrystalline Solids. Journal of the American Chemical Society 2023, 145
(34)
, 19005-19017. https://doi.org/10.1021/jacs.3c06343
- Misaki Nakagawa, Shinpei Kusaka, Atsushi Kiyose, Toshinobu Nakajo, Hiroaki Iguchi, Motohiro Mizuno, Ryotaro Matsuda. Beyond the Conventional Limitation of Photocycloaddition Reaction in the Roomy Nanospace of a Metal–Organic Framework. Journal of the American Chemical Society 2023, 145
(22)
, 12059-12065. https://doi.org/10.1021/jacs.3c01225
- Gyehyun Park, Malina Bilo, Michael Fröba, YounJoon Jung, Young Joo Lee. Influence of Surface Chemistry on the Surfactant Organization and Interfacial Structure of Mesoporous Silica and Organosilica. The Journal of Physical Chemistry C 2022, 126
(34)
, 14693-14703. https://doi.org/10.1021/acs.jpcc.2c03951
- Francoise M. Amombo
Noa, Erik Svensson Grape, Michelle Åhlén, William E. Reinholdsson, Christian R. Göb, François-Xavier Coudert, Ocean Cheung, A. Ken Inge, Lars Öhrström. Chiral Lanthanum Metal–Organic Framework with Gated CO2 Sorption and Concerted Framework Flexibility. Journal of the American Chemical Society 2022, 144
(19)
, 8725-8733. https://doi.org/10.1021/jacs.2c02351
- Mikhail Suyetin, Maxim V. Peskov, Udo Schwingenschlögl, Lev Sarkisov. Exploring the limits of csq-Zr-MOFs in Adsorption Heat Pumps: a computational study of their potential for cooling and heating applications. Adsorption 2025, 31
(2)
https://doi.org/10.1007/s10450-024-00579-z
- Marzena Rams-Baron, Alfred Błażytko, Karolina Jurkiewicz, Piotr Lodowski, Maria Książek, Joachim Kusz, Witold Mozga, Marta Fordymacka, Mahshid Teymouri, Julia Krzywik, Marian Paluch. Image of the solid-state rotary motion encoded in the dielectric response. Reports on Progress in Physics 2024, 87
(10)
, 108002. https://doi.org/10.1088/1361-6633/ad7288
- Antonija Ferbezar, Roman Zettl, Katharina Hogrefe, Harald Fitzek, Bernhard Gadermaier, H. Martin R. Wilkening, Ilie Hanzu. Tuning the ion conductivity of Zr-based metal–organic framework ionogels by linker functionalization. Journal of Materials Chemistry A 2024, 12
(21)
, 12552-12563. https://doi.org/10.1039/D3TA06986A
- Konstantin Stracke, Jack D. Evans. The use of collective variables and enhanced sampling in the simulations of existing and emerging microporous materials. Nanoscale 2024, 16
(19)
, 9186-9196. https://doi.org/10.1039/D4NR01024H
- Babak Farhadi Jahromi, Rochus Schmid. Dielectric response of metal–organic frameworks as a function of confined guest species investigated by molecular dynamics simulations. The Journal of Chemical Physics 2024, 160
(18)
https://doi.org/10.1063/5.0203820
- Yun-Long Hou, Caoyu Yang, Zhongjie Yang, Huaqun Zhou, Leiming Guo, Jun Guo, Xiaofei Zhang. Building robust metal-organic frameworks with premade ligands. Coordination Chemistry Reviews 2024, 505 , 215690. https://doi.org/10.1016/j.ccr.2024.215690
- Wang Li, Miao Xie, Shi-Yong Zhang, Cheng-Hui Zeng, Zi-Yi Du, Chun-Ting He. A confinement-regulated (H
3
C–NH
3
)
+
ion as a smallest dual-wheel rotator showing bisected rotation dynamics. Physical Chemistry Chemical Physics 2024, 26
(9)
, 7269-7275. https://doi.org/10.1039/D3CP05406C
- Hui Xiao, Wei-Yu Hu, Qing Wang, Cheng-Hui Zeng, Hao-Hong Li, Haiming Liu, Zi-Yi Du, Chun-Ting He. Molecular rotators anchored on a rod-like anionic coordination polymer adhered by charge-assisted hydrogen bonds. Physical Chemistry Chemical Physics 2024, 26
(5)
, 3974-3980. https://doi.org/10.1039/D3CP05597C
- Lena Marie Funke, Alicia Lund, Hao Zhuang, Jeffrey A. Reimer. Metal–Organic Frameworks: Challenges Addressed via Magnetic Resonance Spectroscopy. Applied Magnetic Resonance 2023, 54
(11-12)
, 1193-1220. https://doi.org/10.1007/s00723-023-01604-0
- Simon Krause, Jovana V. Milić. Functional dynamics in framework materials. Communications Chemistry 2023, 6
(1)
https://doi.org/10.1038/s42004-023-00945-y
- Jennifer Schnabel, Arthur Schulz, Peter Lunkenheimer, Dirk Volkmer. Benzothiadiazole-based rotation and possible antipolar order in carboxylate-based metal-organic frameworks. Communications Chemistry 2023, 6
(1)
https://doi.org/10.1038/s42004-023-00959-6
- Yihao Chen, Jingjing Chen, Chongchong Chen, Xiaoli Wu, Yifan Li, Jie Zhang, Jingtao Wang. Molecular dissolution behaviors on porous membrane surface using hierarchical metal–organic framework lamellar membrane. AIChE Journal 2023, 69
(5)
https://doi.org/10.1002/aic.17981
- Mingoo Jin, Satsuki Matsuura, Hikaru Yamamoto, Motohiro Mizuno, Hajime Ito. Multidynamic Crystalline Molecular Rotors Comprising an N‐Heterocyclic Carbene Binuclear Au(I) Complex Bearing Multiple Rotators. European Journal of Organic Chemistry 2023, 26
(12)
https://doi.org/10.1002/ejoc.202201468
- Baowen Li, Juan P. Vizuet, Gregory T. McCandless, Kenneth J. Balkus Jr. Controlling pore size and interlayer space by ring rotation and electron-withdrawing effects in a 2D MOF. Polyhedron 2023, 230 , 116211. https://doi.org/10.1016/j.poly.2022.116211
- Wang Li, De‐Xuan Liu, Wei‐Yu Hu, Qing‐Yan Liu, Zi‐Yi Du, Chun‐Ting He, Wei‐Xiong Zhang, Xiao‐Ming Chen. A Crystalline Supramolecular Rotor Functioned by Dual Ultrasmall Polar Rotators
†. Chinese Journal of Chemistry 2022, 40
(16)
, 1917-1923. https://doi.org/10.1002/cjoc.202200212
- Xia Li, Jialin Xie, Zhenglin Du, Long Jiang, Guangqin Li, Sanliang Ling, Kelong Zhu. Docking rings in a solid: reversible assembling of pseudorotaxanes inside a zirconium metal–organic framework. Chemical Science 2022, 13
(21)
, 6291-6296. https://doi.org/10.1039/D2SC01497A
- Adam R. Altenhof, Zhehong Gan, Robert W. Schurko. Reducing the effects of weak homonuclear dipolar coupling with CPMG pulse sequences for static and spinning solids. Journal of Magnetic Resonance 2022, 337 , 107174. https://doi.org/10.1016/j.jmr.2022.107174
Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.
Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.
The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.
Recommended Articles
Abstract
Chart 1
Chart 1. Schematic of the Energy Profile of a Terephthalate Rotor LinkerFigure 1
Figure 1. Structure of three members of the MIL-53 family viewed along the pore direction. (a) MIL-53(Al) (lp), (b) NO2-MIL-53(Al) (lp), and (c) NH2-MIL-53(Al) (np). This topology is characterized by four distinct rows of linkers per unit cell forming rhombic pores. Closest row distances for each MOF are marked in magenta. For compete unit cell parameters, see Table S2.
Figure 2
Figure 2. Effect of linker rotation on the potential energy as studied by DFT. (a) Unit cell of NO2-MIL-53(Al) with central linker in 0° rotation with respect to (011) plane (pink); hydrogens omitted for clarity. (b) Rotation angle is defined as the angle between benzene ring plane and (011) plane, taking 0° as the conformation with the functional group pointing in the positive [100] direction. The sign of the angle is assigned based on the direction normal of the reference plane. (c) Potential energy profiles for the rotation of one linker in a NH2-MIL-53(Al) and NO2-MIL-53(Al) unit cell. The direction of rotation is indicated by the direction of the marker. (d) Example of an unfavorable head-to-head nitro group encounters in adjacent linkers when they are located on the same side of the ring (top) and on different sides (bottom).
Figure 3
Figure 3. Dielectric spectra of the three systems. (a, b) Imaginary part (ε′′) of ε* for NO2-MIL-53(Al) with respect to temperature (a) and frequency (b). The latter includes the fitted Cole–Cole model as continuous lines. (c, d) Temperature dependence of ε″ for NH2-MIL-53(Al) (c) and MIL-53(Al) (d).
Figure 4
Figure 4. Solid-state 2H NMR studies of NO2-MIL-53(Al)-d3. (a) Experimental (black) and simulated (red) variable-temperature 2H SSNMR spectra of NO2-MIL-53(Al)-d3. (b) Spectra are composed of overlapping patterns representing SML (<103 Hz) and FML (>107–108 Hz) motions, with relative integrated intensities indicated to the right of the simulated spectra. (c) Cartesian frame of reference for the rotation model. (d) Representation of 2H exchange sites and angles used in the model; deuterons are shown in light blue.
Figure 5
Figure 5. Cooperative rotation in NO2-MIL-53(Al). (a) Rotation angle traces of two neighboring rings in a 2 × 1 × 1 cell MD simulation at 700 K. Correlated motion is observed, with simultaneous angle changes in opposite directions (i, ii, iii), when nitro groups are in proximity (N···N distance ca. 4 Å). (b) Selected snapshots (i–iv) of linker pair conformation during a coupled rotation. As ring A rotates in the positive direction, ring B reaches the space originally occupied by ring A.
References
This article references 71 other publications.
- 1van Meer, G.; Voelker, D. R.; Feigenson, G. W. Membrane Lipids: Where They Are and How They Behave. Nat. Rev. Mol. Cell Biol. 2008, 9 (2), 112– 124, DOI: 10.1038/nrm23301https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXovFOntw%253D%253D&md5=13d4eb41956211e22d3a9ee5c6b73854Membrane lipids: where they are and how they behavevan Meer, Gerrit; Voelker, Dennis R.; Feigenson, Gerald W.Nature Reviews Molecular Cell Biology (2008), 9 (2), 112-124CODEN: NRMCBP; ISSN:1471-0072. (Nature Publishing Group)A review. Throughout the biol. world, a 30 Å hydrophobic film typically delimits the environments that serve as the margin between life and death for individual cells. Biochem. and biophys. findings have provided a detailed model of the compn. and structure of membranes, which includes levels of dynamic organization both across the lipid bilayer (lipid asymmetry) and in the lateral dimension (lipid domains) of membranes. How do cells apply anabolic and catabolic enzymes, translocases, and transporters, plus the intrinsic phys. phase behavior of lipids and their interactions with membrane proteins, to create the unique compns. and multiple functionalities of their individual membranes.
- 2Duncan, A. L.; Reddy, T.; Koldsø, H.; Hélie, J.; Fowler, P. W.; Chavent, M.; Sansom, M. S. P. Protein Crowding and Lipid Complexity Influence the Nanoscale Dynamic Organization of Ion Channels in Cell Membranes. Sci. Rep. 2017, 7 (1), 16647, DOI: 10.1038/s41598-017-16865-62https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC1M3ms1CgtA%253D%253D&md5=0cbee7d73392b2947e9ed7bf57f060aaProtein crowding and lipid complexity influence the nanoscale dynamic organization of ion channels in cell membranesDuncan Anna L; Reddy Tyler; Koldso Heidi; Helie Jean; Fowler Philip W; Chavent Matthieu; Sansom Mark S P; Reddy Tyler; Koldso Heidi; Helie Jean; Fowler Philip W; Chavent MatthieuScientific reports (2017), 7 (1), 16647 ISSN:.Cell membranes are crowded and complex environments. To investigate the effect of protein-lipid interactions on dynamic organization in mammalian cell membranes, we have performed coarse-grained molecular dynamics simulations containing >100 copies of an inwardly rectifying potassium (Kir) channel which forms specific interactions with the regulatory lipid phosphatidylinositol 4,5-bisphosphate (PIP2). The tendency of protein molecules to cluster has the effect of organizing the membrane into dynamic compartments. At the same time, the diversity of lipids present has a marked effect on the clustering behavior of ion channels. Sub-diffusion of proteins and lipids is observed. Protein crowding alters the sub-diffusive behavior of proteins and lipids such as PIP2 which interact tightly with Kir channels. Protein crowding also affects bilayer properties, such as membrane undulations and bending rigidity, in a PIP2-dependent manner. This interplay between the diffusion and the dynamic organization of Kir channels may have important implications for channel function.
- 3van der Kooij, H. M.; Semerdzhiev, S. A.; Buijs, J.; Broer, D. J.; Liu, D.; Sprakel, J. Morphing of Liquid Crystal Surfaces by Emergent Collectivity. Nat. Commun. 2019, 10 (1), 1– 9, DOI: 10.1038/s41467-019-11501-53https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsFCiurfP&md5=f2d6568b3bf2db458739b67b53db501eMorphing of liquid crystal surfaces by emergent collectivityvan der Kooij, Hanne M.; Semerdzhiev, Slav A.; Buijs, Jesse; Broer, Dirk J.; Liu, Danqing; Sprakel, JorisNature Communications (2019), 10 (1), 1-9CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)Liq. crystal surfaces can undergo topog. morphing in response to external cues. These shape-shifting coatings promise a revolution in various applications, from haptic feedback in soft robotics or displays to self-cleaning solar panels. The changes in surface topog. can be controlled by tailoring the mol. architecture and mechanics of the liq. crystal network. However, the nanoscopic mechanisms that drive morphol. transitions remain unclear. Here, we introduce a frequency-resolved nanostrain imaging method to elucidate the emergent dynamics underlying field-induced shape-shifting. We show how surface morphing occurs in three distinct stages: (i) the mol. dipoles oscillate with the alternating field (10-100 ms), (ii) this leads to collective plasticization of the glassy network (∼1 s), (iii) culminating in actuation of the topog. (10-100 s). The first stage appears universal and governed by dielec. coupling. By contrast, yielding and deformation rely on a delicate balance between liq. crystal order, field properties and network viscoelasticity.
- 4Catalano, L.; Naumov, P. Exploiting Rotational Motion in Molecular Crystals. CrystEngComm 2018, 20 (39), 5872– 5883, DOI: 10.1039/C8CE00420J4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXotFWgu70%253D&md5=f4fb5c4e8b3f4b31e4db691ea8cc08a2Exploiting rotational motion in molecular crystalsCatalano, Luca; Naumov, PanceCrystEngComm (2018), 20 (39), 5872-5883CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)A review. Various aspects of mol. motion in crystals have been extensively studied in different research fields of chem. as a valuable source of structural and dynamic information en route to new smart materials and solid-state mol. machines. Recent research efforts have been directed towards engineering cryst. media with specific motile components, namely, amphidynamic crystals, whose dynamics can be exploited to achieve specific functions such as sensing, gas sepn. and switchable dielecs. The most promising structural models within this line of pursuit are based upon anisotropic Brownian rotary trajectories. In this highlight, we review the recent advances in this field, with particular emphasis on potential applications. This summary should provide useful guidelines for further development of this remarkable class of materials.
- 5Vogelsberg, C. S.; Garcia-Garibay, M. A. Crystalline Molecular Machines: Function, Phase Order, Dimensionality, and Composition. Chem. Soc. Rev. 2012, 41 (5), 1892– 1910, DOI: 10.1039/C1CS15197E5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XitFyjsLw%253D&md5=33557d840c4c090a6a7d8d04365b5dc6Crystalline molecular machines: function, phase order, dimensionality, and compositionVogelsberg, Cortnie S.; Garcia-Garibay, Miguel A.Chemical Society Reviews (2012), 41 (5), 1892-1910CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The design of mol. machines is stimulated by the possibility of developing new materials with complex physicochem. and mech. properties that are responsive to external stimuli. Condensed-phase matter with anisotropic mol. order and controlled dynamics, also defined as amphidynamic crystals, offers a promising platform for the design of bulk materials capable of performing such functions. Recent studies have shown that it is possible to engineer mol. crystals and extended solids with Brownian rotation about specific axes that can be interfaced with external fields, which may ultimately be used to design novel optoelectronic materials. Structure/function relationships of amphidynamic materials have been characterized, establishing the blueprints to further engineer sophisticated function. However, the synthesis of amphidynamic mol. machines composed of multiple "parts" is essential to realize increasingly complex behavior. Recent progress in amphidynamic multicomponent systems suggests that sophisticated functions similar to those of simple biomol. machines may eventually be within reach.
- 6Khuong, T.-A. A. V; Nunez, J. E.; Godinez, C. E.; Garcia-Garibay, M. A. Crystalline Molecular Machines: A Quest toward Solid-State Dynamics and Function. Acc. Chem. Res. 2006, 39 (6), 413– 422, DOI: 10.1021/ar06802176https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xjt1Kms7s%253D&md5=65d7a75ad0d31017ab5023392082a8f1Crystalline Molecular Machines: A Quest Toward Solid-State Dynamics and FunctionKhuong, Tinh-Alfredo V.; Nunez, Jose E.; Godinez, Carlos E.; Garcia-Garibay, Miguel A.Accounts of Chemical Research (2006), 39 (6), 413-422CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. Complex mol. machinery may be envisioned as densely packed, multicomponent, self-assembling systems built with high structural precision to control the dynamics of one or more internal degrees of freedom. With mol. gyroscopes as a test, we describe a general strategy to design crystals capable of supporting structurally programmed mol. motions, a practical approach to their synthesis, convenient strategies to characterize their solid-state dynamics, and potential applications based on polar structures responding collectively to external fields.
- 7Comotti, A.; Bracco, S.; Sozzani, P. Molecular Rotors Built in Porous Materials. Acc. Chem. Res. 2016, 49 (9), 1701– 1710, DOI: 10.1021/acs.accounts.6b002157https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtlGrs7nF&md5=3ede0039750a5d47042bd3a4299d9dbfMolecular Rotors Built in Porous MaterialsComotti, Angiolina; Bracco, Silvia; Sozzani, PieroAccounts of Chemical Research (2016), 49 (9), 1701-1710CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)Mols. and materials can show dynamic structures in which the dominant mechanism is rotary motion. The single mobile elements are defined as "mol. rotors" and exhibit special properties (compared with their static counterparts), being able in perspective to greatly modulate the dielec. response and form the basis for mol. motors that are designed with the idea of making mols. perform a useful mech. function. The construction of ordered rotary elements into a solid is a necessary feature for such design, because it enables the alignment of rotors and the fine-tuning of their steric and dipolar interactions. Crystal surfaces or bulk crystals are the most suitable to adapt rotors in 2D or 3D arrangements and engineer juxtaposition of the rotors in an ordered way. Nevertheless, it is only in recent times that materials showing porosity and remarkably low d. have undergone tremendous development. The characteristics of large free vol. combine well with the virtually unhindered motion of the mol. rotors built into their structure. Indeed, the mol. rotors are used as struts in porous covalent and supramol. architectures, spanning both hybrid and fully org. materials. The modularity of the approach renders possible a variety of rotor geometrical arrangements in both robust frameworks stable up to 850 K and self-assembled mol. materials. A nanosecond (fast dynamics) motional regime can be achieved at temps. lower than 240 K, enabling rotor arrays operating in the solid state even at low temps. Furthermore, in nanoporous materials, mol. rotors can interact with the diffusing chem. species, be they liqs., vapors, or gases. Through this chem. intervention, rotor speed can be modulated at will, enabling a new generation of rotor-contg. materials sensitive to guests. In principle, an applied elec. field can be the stimulus for chem. release from porous materials. The effort needed to obtain strong dipoles that are noncentrosym. mounted onto rotors and do not hamper rotational motion is a further aspect of this research activity. Thus, materials showing dielec. properties in response to applied elec. fields have been fabricated. This may lead to challenging materials that are promptly responsive to an applied elec. field, altering the ferroelec. or antiferroelec. ground state by fast dipole reorientation when subjected to elec. polarization.
- 8Deng, H.; Olson, M. A.; Stoddart, J. F.; Yaghi, O. M. Robust Dynamics. Nat. Chem. 2010, 2 (6), 439– 443, DOI: 10.1038/nchem.6548https://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.
- 9Gonzalez-Nelson, A.; Coudert, F.-X.; van der Veen, M. Rotational Dynamics of Linkers in Metal–Organic Frameworks. Nanomaterials 2019, 9 (3), 330, DOI: 10.3390/nano90303309https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtFWrs7bO&md5=ff79c23c592c32d12d1589028651b842Rotational dynamics of linkers in metal-organic frameworksGonzalez-Nelson, Adrian; Coudert, Francois-Xavier; Van Der Veen, Monique A.Nanomaterials (2019), 9 (3), 330CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)A review. Among the numerous fascinating properties of metal-org. frameworks (MOFs), their rotational dynamics is perhaps one of the most intriguing, with clear consequences for adsorption and sepn. of mols., as well as for optical and mech. properties. A closer look at the rotational mobility in MOF linkers reveals that it is not only a considerably widespread phenomenon, but also a fairly diverse one. Still, the impact of these dynamics is often understated. In this review, we address the various mechanisms of linker rotation reported in the growing collection of literature, followed by a highlight of the methods currently used in their study, and we conclude with the impacts that such dynamics have on existing and future applications.
- 10Martinez-Bulit, P.; Stirk, A. J.; Loeb, S. J. Rotors, Motors, and Machines Inside Metal–Organic Frameworks. Trends in Chemistry. Cell Press September 2019, 1, 588– 600, DOI: 10.1016/j.trechm.2019.05.005There is no corresponding record for this reference.
- 11Dong, J.; Wee, V.; Peh, S. B.; Zhao, D. Molecular-Rotor-Driven Advanced Porous Materials. Angew. Chem., Int. Ed. 2021, 60, 2– 16, DOI: 10.1002/anie.202101646There is no corresponding record for this reference.
- 12Gee, J. A.; Sholl, D. S. Effect of Framework Flexibility on C 8 Aromatic Adsorption at High Loadings in Metal–Organic Frameworks. J. Phys. Chem. C 2016, 120 (1), 370– 376, DOI: 10.1021/acs.jpcc.5b1026012https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvFKlu7nM&md5=a6cfb8f04df14571ae5130dae5ca34aeEffect of Framework Flexibility on C8 Aromatic Adsorption at High Loadings in Metal-Organic FrameworksGee, Jason A.; Sholl, David S.Journal of Physical Chemistry C (2016), 120 (1), 370-376CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The authors show that the use of this approxn. to describe the multicomponent adsorption of C8 aroms. in MOFs under industrial conditions gives results that differ dramatically from descriptions that include local framework flexibility. To address this issue, we develop an efficient method for capturing the effect of framework flexibility on adsorption in nanoporous materials. This "flexible snapshot" method uses GCMC simulations to model adsorption in snapshots collected using fully flexible MD simulations and can be applied to any framework-adsorbate system for which reliable force fields are available. The method gives considerably better agreement with expts. for multicomponent C8 arom. selectivities in multiple MOFs than more traditional calcns. using a single rigid framework. The rotation of org. linkers in the MOFs has a strong influence on selectivities in these systems. Because many MOFs contain this structural feature, we expect that using simulations that incorporate this kind of internal flexibility will be important in obtaining accurate adsorption predictions in a range of circumstances. This is esp. true for many industrially relevant sepns. in MOFs, in particular, those that exploit high pore loadings of adsorbed species.
- 13Park, J.; Agrawal, M.; Sava Gallis, D. F.; Harvey, J. A.; Greathouse, J. A.; Sholl, D. S. Impact of Intrinsic Framework Flexibility for Selective Adsorption of Sarin in Non-Aqueous Solvents Using Metal–Organic Frameworks. Phys. Chem. Chem. Phys. 2020, 22 (11), 6441– 6448, DOI: 10.1039/C9CP06788D13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXktVGrtL4%253D&md5=29d64d87c381388a1b7485ed21c8af26Framework flexibility for selective adsorption of sarin in non-aqueous solvents using metal-organic frameworksPark, Jongwoo; Agrawal, Mayank; Sava Gallis, Dorina F.; Harvey, Jacob A.; Greathouse, Jeffery A.; Sholl, David S.Physical Chemistry Chemical Physics (2020), 22 (11), 6441-6448CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Mol. modeling of mixt. adsorption in nanoporous materials can provide insight into the mol.-level details that underlie adsorptive sepns. Modeling of adsorption often employs a rigid framework approxn. for computational convenience. All real materials, however, have intrinsic flexibility due to thermal vibrations of their atoms. In this article, we examine quant. predictions of the adsorption selectivity for a dil. concn. of a chem. warfare agent, sarin, from bulk mixts. with aq. and non-aq. (methanol, iso-Pr alc.) solvents using metal-org. frameworks (MOFs). These predictions were made in MOFs approximated as rigid and also in MOFs allowed to have intrinsic flexibility. Including framework flexibility appears to have important consequences for quant. predictions of adsorption selectivity, particularly for sarin/water mixts. Our observations suggest the intrinsic flexibility of MOFs can have a nontrivial impact on adsorption modeling of mol. mixts., esp. for mixts. contg. polar species and mols. of different sizes.
- 14Agrawal, M.; Bhattacharyya, S.; Huang, Y.; Jayachandrababu, K. C.; Murdock, C. R.; Bentley, J. A.; Rivas-Cardona, A.; Mertens, M. M.; Walton, K. S.; Sholl, D. S.; Nair, S. Liquid-Phase Multicomponent Adsorption and Separation of Xylene Mixtures by Flexible MIL-53 Adsorbents. J. Phys. Chem. C 2018, 122 (1), 386– 397, DOI: 10.1021/acs.jpcc.7b0910514https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFOiurnE&md5=ae96c143beca18253acb13c2d9ad386cLiquid-Phase Multicomponent Adsorption and Separation of Xylene Mixtures by Flexible MIL-53 AdsorbentsAgrawal, Mayank; Bhattacharyya, Souryadeep; Huang, Yi; Jayachandrababu, Krishna C.; Murdock, Christopher R.; Bentley, Jason A.; Rivas-Cardona, Alejandra; Mertens, Machteld M.; Walton, Krista S.; Sholl, David S.; Nair, SankarJournal of Physical Chemistry C (2018), 122 (1), 386-397CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The MIL-53 class of metal-org. frameworks (MOFs) has recently generated interest as potential adsorbents for xylene mixt. sepns. Cost-effective sepn. of xylene isomers is challenging owing to the similarity in their mol. structures, kinetic diams., and b.ps. Here we report a systematic exptl. and computational study of xylene isomer adsorption in MIL-53 adsorbents, focusing particularly on the effects of different metal centers, detn. of sepn. properties with industrially relevant quaternary liq.-phase C8 arom. feeds, and a predictive mol. simulation methodol. that accounts for all relevant modes of MIL-53 framework flexibility. Significant scale-up of MIL-53 synthesis was carried out to produce high-quality materials in sufficient quantities (300-500 g each) for detailed measurements. Single-component adsorption simulations incorporating the MIL-53 "breathing" and linker flexibility effects showed good agreement with exptl. isotherms. Upon the basis of these results, three materials - MIL-53(Al), MIL-53(Cr), and MIL-53(Ga) - were selected for detailed quaternary liq. breakthrough measurements. High o-xylene quaternary selectivity was obtained from all of the MIL-53 materials, with MIL-53(Al) being the most selective. Better packing efficiency of o-xylene and its preferred interactions with the MIL-53 framework are hypothesized to lead to high selectivity. Predictions from flexible-structure multicomponent adsorption simulations showed good overall agreement with expt. This is, to the best of our knowledge, the first exptl. report on the xylene adsorption characteristics of MIL-53 materials under industrially relevant operating conditions. In addn., it is also the first attempt to develop computational methods that account for various flexibility modes in MIL-53 materials for adsorption simulations. This has significant broader applications for the successful prediction of adsorption properties of larger mols. (such as C8 arom. isomers) in flexible MOFs.
- 15Verploegh, R. J.; Kulkarni, A.; Boulfelfel, S. E.; Haydak, J. C.; Tang, D.; Sholl, D. S. Screening Diffusion of Small Molecules in Flexible Zeolitic Imidazolate Frameworks Using a DFT-Parameterized Force Field. J. Phys. Chem. C 2019, 123 (14), 9153– 9167, DOI: 10.1021/acs.jpcc.9b0073315https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXktlOitbY%253D&md5=0980f16df3829ee10667f763d686c75aScreening diffusion of small molecules in flexible zeolitic imidazolate frameworks using a DFT-parameterized force fieldVerploegh, Ross J.; Kulkarni, Ambarish; Boulfelfel, Salah Eddine; Haydak, Jonathan C.; Tang, Dai; Sholl, David S.Journal of Physical Chemistry C (2019), 123 (14), 9153-9167CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Quant. modeling adsorbate diffusion through zeolitic imidazolate frameworks (ZIFs) must account for the inherent flexibility of these materials. The lack of a transferable intramol. ZIF force field (FF) for use in classical simulations has previously made an accurate simulation of adsorbate diffusion in many ZIFs impossible. We resolve this problem by introducing a d. functional theory parameterized force field (FF) for ZIFs named the intraZIF-FF, which includes perturbations to the class I force fields previously used to model ZIFs. This FF outperforms ad hoc force fields at predicting ab initio relative energies and at. forces taken from fully periodic ab initio mol. dynamics simulations of SALEM-2, ZIF-7, ZIF-8, and ZIF-90. We use the intraZIF-FF to predict the infinite diln. self-diffusion coeffs. of 30 adsorbates with mol. diams. ranging from 2.66 to 7.0 Å in these 4 ZIFs. These results greatly increase the no. of adsorbates for which accurate information about mol. diffusion in ZIFs is available.
- 16Witman, M.; Ling, S.; Jawahery, S.; Boyd, P. G.; Haranczyk, M.; Slater, B.; Smit, B. The Influence of Intrinsic Framework Flexibility on Adsorption in Nanoporous Materials. J. Am. Chem. Soc. 2017, 139 (15), 5547– 5557, DOI: 10.1021/jacs.7b0168816https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXltlCms7k%253D&md5=b834291a7ad2b83f735c98e63428eeb1The Influence of Intrinsic Framework Flexibility on Adsorption in Nanoporous MaterialsWitman, Matthew; Ling, Sanliang; Jawahery, Sudi; Boyd, Peter G.; Haranczyk, Maciej; Slater, Ben; Smit, BerendJournal of the American Chemical Society (2017), 139 (15), 5547-5557CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)For applications of metal-org. frameworks (MOFs) such as gas storage and sepn., flexibility is often seen as a parameter that can tune material performance. The authors aim to det. the optimal flexibility for the shape selective sepn. of similarly sized mols. (e.g., Xe/Kr mixts.). To obtain systematic insight into how the flexibility impacts this type of sepn., the authors develop a simple anal. model that predicts a material's Henry regime adsorption and selectivity as a function of flexibility. The authors elucidate the complex dependence of selectivity on a framework's intrinsic flexibility whereby performance is either improved or reduced with increasing flexibility, depending on the material's pore size characteristics. However, the selectivity of a material with the pore size and chem. that already maximizes selectivity in the rigid approxn. is continuously diminished with increasing flexibility, demonstrating that the globally optimal sepn. exists within an entirely rigid pore. Mol. simulations show that our simple model predicts performance trends that are obsd. when screening the adsorption behavior of flexible MOFs. These flexible simulations provide better agreement with exptl. adsorption data in a high-performance material that is not captured when modeling this framework as rigid, an approxn. typically made in high-throughput screening studies. The authors conclude that, for shape selective adsorption applications, the globally optimal material will have the optimal pore size/chem. and minimal intrinsic flexibility even though other nonoptimal materials' selectivity can actually be improved by flexibility. Equally important, we find that flexible simulations can be crit. for correctly modeling adsorption in these types of systems.
- 17Lennox, M. J.; Düren, T. Understanding the Kinetic and Thermodynamic Origins of Xylene Separation in UiO-66(Zr) via Molecular Simulation. J. Phys. Chem. C 2016, 120 (33), 18651– 18658, DOI: 10.1021/acs.jpcc.6b0614817https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1Kms7fF&md5=60526609a421092a2bb6cacae13ee182Understanding the Kinetic and Thermodynamic Origins of Xylene Separation in UiO-66(Zr) via Molecular SimulationLennox, Matthew J.; Duren, TinaJournal of Physical Chemistry C (2016), 120 (33), 18651-18658CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Xylene isomers are precursors in many important chem. processes, yet their sepn. via crystn. or distn. is energy intensive. Adsorption presents an attractive, lower-energy alternative and the discovery of adsorbents which outperform the current state-of-the-art zeolitic materials represents one of the key challenges in materials design, with metal-org. frameworks receiving particular attention. One of the most well-studied systems in this context is UiO-66(Zr), which selectively adsorbs o-xylene over the other C8 alkylaroms. The mechanism behind this sepn. has remained unclear, however. In this work, a wide range of computational techniques are employed to explore both the equil. and dynamic behavior of the xylene isomers in UiO-66(Zr). In addn. to correctly predicting the exptl. obsd. ortho-selectivity, it is demonstrated that the equil. selectivity is based upon the complete encapsulation of o-xylene within the pores of the framework. Furthermore, the flexible nature of the adsorbent is crucial in facilitating xylene diffusion and the simulations reveal for the first time significant differences between the intracryst. diffusion mechanisms of the three isomers resulting in a kinetic contribution to the selectivity. Consequently, it is important to include both equil. and kinetic effects when screening MOFs for xylene sepns.
- 18Evans, J. D.; Krause, S.; Feringa, B. L. Cooperative and Synchronized Rotation in Motorized Porous Frameworks: Impact on Local and Global Transport Properties of Confined Fluids. Faraday Discuss. 2021, 225, 286– 300, DOI: 10.1039/D0FD00016G18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXksFKkt7c%253D&md5=561247e6a6675cf04d8bf3b5d3a2cff6Cooperative and synchronized rotation in motorized porous frameworks: impact on local and global transport properties of confined fluidsEvans, Jack D.; Krause, Simon; Feringa, Ben L.Faraday Discussions (2021), 225 (Cooperative Phenomena in Framework Materials), 286-300CODEN: FDISE6; ISSN:1359-6640. (Royal Society of Chemistry)Mols. in gas and liq. states, as well as in soln., exhibit significant and random Brownian motion. Mols. in the solid-state, although strongly immobilized, can still exhibit significant intramol. dynamics. However, in most framework materials, these intramol. dynamics are driven by temp., and therefore are neither controlled nor spatially or temporarily aligned. In recent years, several examples of mol. machines that allow for a stimuli-responsive control of dynamical motion, such as rotation, have been reported. In this contribution, we investigate the local and global properties of a Lennard-Jones (LJ) fluid surrounding a mol. motor and consider the influence of cooperative and non-directional rotation for a mol. motor-contg. pore system. This study uses classical mol. dynamics simulations to describe a minimal model, which was developed to resemble known mol. motors. The properties of an LJ liq. surrounding an isolated mol. motor remain mostly unaffected by the introduced rotation. We then considered an arrangement of motors within a one-dimensional pore. Changes in diffusivity for pore sizes approaching the length of the rotor were obsd., resulting from rotation of the motors. We also considered the influence of cooperative motor directionality on the directional transport properties of this confined fluid. Importantly, we discovered that specific unidirectional rotation of altitudinal motors can produce directed diffusion.
- 19Aprahamian, I. The Future of Molecular Machines. ACS Cent. Sci. 2020, 6 (3), 347– 358, DOI: 10.1021/acscentsci.0c0006419https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXksVShu7c%253D&md5=3f43b0cedea31dc87158e714bf013d75The Future of Molecular MachinesAprahamian, IvanACS Central Science (2020), 6 (3), 347-358CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)A review. Artificial mol. machines have captured the imagination of scientists and nonscientists alike for decades now, given their clear potential to transform and enhance all aspects of human life. In this Outlook, I use a bicycle as an analogy to explain what a mol. machine is, in my opinion, and work through a representative selection of case studies to specify the significant accomplishments made to date, and the obstacles that currently stand between these and the field's fulfillment of its great potential. The hope of this intentionally sober account is to sketch a path toward a rich and exciting research trajectory that might challenge current practitioners and attract junior scientists into its fold. Considering the progress we have witnessed in the past decade, I am pos. that the future of the field is a rosy one. Using a bicycle as an analogy for mol. machines, this Outlook surveys the recent advances in the field, while elaborating on the challenges in the way of it fulfilling its full potential.
- 20Vogelsberg, C. S.; Uribe-Romo, F. J.; Lipton, A. S.; Yang, S.; Houk, K. N.; Brown, S.; Garcia-Garibay, M. A. Ultrafast Rotation in an Amphidynamic Crystalline Metal Organic Framework. Proc. Natl. Acad. Sci. U. S. A. 2017, 114 (52), 13613– 13618, DOI: 10.1073/pnas.170881711520https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGns7%252FN&md5=a6cc4f2b0e4ea8f49e015ba367c02e65Ultrafast rotation in an amphidynamic crystalline metal organic frameworkVogelsberg, Cortnie S.; Uribe-Romo, Fernando J.; Lipton, Andrew S.; Yang, Song; Houk, K. N.; Brown, Stuart; Garcia-Garibay, Miguel A.Proceedings of the National Academy of Sciences of the United States of America (2017), 114 (52), 13613-13618CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Amphidynamic crystals are an emergent class of condensed phase matter designed with a combination of lattice-forming elements linked to components that display engineered dynamics in the solid state. Here, we address the design of a cryst. array of mol. rotors with inertial diffusional rotation at the nanoscale, characterized by the absence of steric or electronic barriers. We solved this challenge with 1,4-bicyclo[2.2.2]octane dicarboxylic acid (BODCA)-MOF, a metal-org. framework (MOF) built with a high-symmetry bicyclo[2.2.2]octane dicarboxylate linker in a Zn4O cubic lattice. Using spin-lattice relaxation 1H solid-state NMR at 29.49 and 13.87 MHz at of 2.3-80 K, we showed that internal rotation occurs in a potential with energy barriers of 0.185 kcal mol-1. These results were confirmed with 2H solid-state NMR line-shape anal. and spin-lattice relaxation at 76.78 MHz obtained between 6 and 298 K, which, combined with mol. dynamics simulations, indicate that inertial diffusional rotation is characterized by a broad range of angular displacements with no residence time at any given site. The ambient temp. rotation of the bicyclo[2.2.2]octane (BCO) group in BODCA-MOF constitutes an example where engineered rotational dynamics in the solid state are as fast as they would be in a high-d. gas or in a low-d. liq. phase.
- 21Bracco, S.; Castiglioni, F.; Comotti, A.; Galli, S.; Negroni, M.; Maspero, A.; Sozzani, P. Ultrafast Molecular Rotors and Their CO2Tuning in MOFs with Rod-Like Ligands. Chem. - Eur. J. 2017, 23 (47), 11210– 11215, DOI: 10.1002/chem.20170293021https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Kqt7jP&md5=2c22a9d917a50470d42b84b01b752e35Ultrafast Molecular Rotors and Their CO2 Tuning in MOFs with Rod-Like LigandsBracco, Silvia; Castiglioni, Fabio; Comotti, Angiolina; Galli, Simona; Negroni, Mattia; Maspero, Angelo; Sozzani, PieroChemistry - A European Journal (2017), 23 (47), 11210-11215CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)A metal org. framework (MOF) engineered to contain in its scaffold rod-like struts featuring ultrafast mol. rotors showed extremely rapid 180 ° flip reorientation with rotational rates of 1011 Hz at 150 K. Crystal-pore accessibility of the MOF allowed the CO2 mols. to enter the cavities and control the rotor spinning speed down to 105 Hz at 150 K. Rotor dynamics, as modulated by CO2 loading/unloading in the porous crystals, was described by proton T1 and 2H NMR spectroscopy. This strategy enabled the regulation of rotary motion by the diffusion of the gas within the channels and the detn. of the energetics of rotary dynamics in the presence of CO2.
- 22Perego, J.; Bracco, S.; Negroni, M.; Bezuidenhout, C. X.; Prando, G.; Carretta, P.; Comotti, A.; Sozzani, P. Fast Motion of Molecular Rotors in Metal–Organic Framework Struts at Very Low Temperatures. Nat. Chem. 2020, 12 (9), 845– 851, DOI: 10.1038/s41557-020-0495-322https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlagtLjJ&md5=d8814e5ea7ea69923bca149127b51bedFast motion of molecular rotors in metal-organic framework struts at very low temperaturesPerego, Jacopo; Bracco, Silvia; Negroni, Mattia; Bezuidenhout, Charl X.; Prando, Giacomo; Carretta, Pietro; Comotti, Angiolina; Sozzani, PieroNature Chemistry (2020), 12 (9), 845-851CODEN: NCAHBB; ISSN:1755-4330. (Nature Research)The solid state is typically not well suited to sustaining fast mol. motion, but in recent years a variety of mol. machines, switches and rotors were successfully engineered within porous crystals and on surfaces. Here the authors show a fast-rotating mol. rotor within the bicyclopentane-dicarboxylate struts of a zinc-based metal-org. framework-the carboxylate groups anchored to the metal clusters act as an axle while the bicyclic unit is free to rotate. The three-fold bipyramidal symmetry of the rotator conflicts with the four-fold symmetry of the struts within the cubic crystal cell of the zinc metal-org. framework. This frustrates the formation of stable conformations, allowing for the continuous, unidirectional, hyperfast rotation of the bicyclic units with an energy barrier of 6.2 cal mol-1 and a high frequency persistent for several turns even at very low temps. (1010 Hz <2 K). Using zirconium instead of zinc led to a different metal cluster-carboxylate coordination arrangement in the resulting metal-org. framework, and much slower rotation of the bicyclic units.
- 23Danowski, W.; van Leeuwen, T.; Abdolahzadeh, S.; Roke, D.; Browne, W. R.; Wezenberg, S. J.; Feringa, B. L. Unidirectional Rotary Motion in a Metal–Organic Framework. Nat. Nanotechnol. 2019, 14 (5), 488– 494, DOI: 10.1038/s41565-019-0401-623https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXms1Ogtrk%253D&md5=861d9bbbd1eafb32a0004a698d9d741aUnidirectional rotary motion in a metal-organic frameworkDanowski, Wojciech; van Leeuwen, Thomas; Abdolahzadeh, Shaghayegh; Roke, Diederik; Browne, Wesley R.; Wezenberg, Sander J.; Feringa, Ben L.Nature Nanotechnology (2019), 14 (5), 488-494CODEN: NNAABX; ISSN:1748-3387. (Nature Research)Overcrowded alkene-based light-driven mol. motors are able to perform large-amplitude repetitive unidirectional rotations. Their behavior is well understood in soln. However, Brownian motion precludes the precise positioning at the nanoscale needed to harness cooperative action. Here, authors demonstrate mol. motors organized in cryst. metal-org. frameworks (MOFs). The motor unit becomes a part of the org. linker (or strut), and its spatial arrangement is elucidated through powder and single-crystal x-ray analyses and polarized optical and Raman microscopies. They confirm that the light-driven unidirectional rotation of the motor units is retained in the MOF framework and that the motors can operate in the solid state with similar rotary speed (rate of thermal helix inversion) to that in soln. These 'moto-MOFs' could in the future be used to control dynamic function in cryst. materials.
- 24Kottas, G. S.; Clarke, L. I.; Horinek, D.; Michl, J. Artificial Molecular Rotors. Chem. Rev. 2005, 105 (4), 1281– 1376, DOI: 10.1021/cr030099324https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjt1KmtL4%253D&md5=e1bed85db4dfe2562729760b32fb45a8Artificial Molecular RotorsKottas, Gregg S.; Clarke, Laura I.; Horinek, Dominik; Michl, JosefChemical Reviews (Washington, DC, United States) (2005), 105 (4), 1281-1376CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review on properties of mech. conformational motion of org. mols. in soln. and solids and on surfaces by expts. and mol. dynamics.
- 25Yan, Y.; Kolokolov, D. I.; da Silva, I.; Stepanov, A. G.; Blake, A. J.; Dailly, A.; Manuel, P.; Tang, C. C.; Yang, S.; Schröder, M. Porous Metal–Organic Polyhedral Frameworks with Optimal Molecular Dynamics and Pore Geometry for Methane Storage. J. Am. Chem. Soc. 2017, 139 (38), 13349– 13360, DOI: 10.1021/jacs.7b0545325https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1OmsLvM&md5=44b3451283362914bb619f8a35857e44Porous Metal-Organic Polyhedral Frameworks with Optimal Molecular Dynamics and Pore Geometry for Methane StorageYan, Yong; Kolokolov, Daniil I.; da Silva, Ivan; Stepanov, Alexander G.; Blake, Alexander J.; Dailly, Anne; Manuel, Pascal; Tang, Chiu C.; Yang, Sihai; Schroder, MartinJournal of the American Chemical Society (2017), 139 (38), 13349-13360CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Natural gas (methane, CH4) is widely considered as a promising energy carrier for mobile applications. Maximizing the storage capacity is the primary goal for the design of future storage media. Here we report the CH4 storage properties in a family of isostructural (3,24)-connected porous materials, MFM-112a, MFM-115a, and MFM-132a, with different linker backbone functionalization. Both MFM-112a and MFM-115a show excellent CH4 uptakes of 236 and 256 cm3 (STP) cm-3 (vol./vol.) at 80 bar and room temp., resp. Significantly, MFM-115a displays an exceptionally high deliverable CH4 capacity of 208 vol./vol. between 5 and 80 bar at room temp., making it among the best performing metal-org. frameworks for CH4 storage. We also synthesized the partially deuterated versions of the above materials and applied solid-state 2H NMR spectroscopy to show that these three frameworks contain mol. rotors that exhibit motion in fast, medium, and slow regimes, resp. In situ neutron powder diffraction studies on the binding sites for CD4 within MFM-132a and MFM-115a reveal that the primary binding site is located within the small pocket enclosed by the [(Cu2)3(isophthalate)3] window and three anthracene/phenyl panels. The open Cu(II) sites are the secondary/tertiary adsorption sites in these structures. Thus, we obtained direct exptl. evidence showing that a tight cavity can generate a stronger binding affinity to gas mols. than open metal sites. Solid-state 2H NMR spectroscopy and neutron diffraction studies reveal that it is the combination of optimal mol. dynamics, pore geometry and size, and favorable binding sites that leads to the exceptional and different methane uptakes in these materials.
- 26Sokolov, A. N.; Swenson, D. C.; MacGillivray, L. R. Conformational Polymorphism in a Heteromolecular Single Crystal Leads to Concerted Movement Akin to Collective Rack-and-Pinion Gears at the Molecular Level. Proc. Natl. Acad. Sci. U. S. A. 2008, 105 (6), 1794– 1797, DOI: 10.1073/pnas.070611710526https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXisVWmsLk%253D&md5=623028ae5f5030254ff70c55221bcfdbConformational polymorphism in a heteromolecular single crystal leads to concerted movement akin to collective rack-and-pinion gears at the molecular levelSokolov, Anatoliy N.; Swenson, Dale C.; MacGillivray, Leonard R.Proceedings of the National Academy of Sciences of the United States of America (2008), 105 (6), 1794-1797CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)The authors describe a heteromol. single crystal that exhibits three reversible and concerted reorganizations upon heating and cooling. The products of the reorganizations are conformational polymorphs. The reorganizations are postulated to proceed through three motions: (i) alkyl translations, (ii) olefin rotations, and (iii) rotational tilts. The motions are akin to rack-and-pinion gears at the mol. level. The rack-like movement is based on expansions and compressions of alkyl chains that are coupled with pinion-like 180° rotations of olefins. To accommodate the movements, phenol and thiophene components undergo rotational tilts about intermol. hydrogen bonds. The movements are collective, being propagated in close-packed repeating units. This discovery marks a step to understanding how org. solids can support the development of cryst. mol. machines and devices through correlated and collective movements.
- 27Jarowski, P. D.; Houk, K. N.; Garcia-Garibay, M. A. Importance of Correlated Motions on the Low Barrier Rotational Potentials of Crystalline Molecular Gyroscopes. J. Am. Chem. Soc. 2007, 129 (11), 3110– 3117, DOI: 10.1021/ja063790727https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhvF2kurk%253D&md5=f1e97dbccd1a797bdfabc5f30b6d8ed4Importance of Correlated Motions on the Low Barrier Rotational Potentials of Crystalline Molecular GyroscopesJarowski, Peter D.; Houk, K. N.; Garcia-Garibay, Miguel A.Journal of the American Chemical Society (2007), 129 (11), 3110-3117CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The energetic and structural changes taking place upon rotation of the central phenylene of 1,4-bis(3,3,3-triphenylpropynyl)benzene in the solid state were computed using mol. mechanics calcns. Pseudopolymorphic crystals of a benzene clathrate (1A) and a desolvated form (1B) were analyzed with models that account for varying degrees of freedom within the corresponding lattices. The calcd. rotational barriers in a rigid lattice approxn., 78 kcal/mol for 1A and 72 kcal/mol for 1B, are about 5 times greater than those previously measured by variable-temp. 13C CPMAS NMR and quadrupolar echo 2H NMR line-shape anal.: 12.8 kcal/mol for 1A and 14.6 kcal/mol for 1B. The potential energy barriers calcd. with a model that restricts whole body rotation and translational motions but allows for internal rotations give results that are near the exptl. free-energy barriers. The calcd. barriers for 1A and 1B are 15.5 and 16.2 kcal/mol, resp. The differences between the rigid and partially relaxed models are attributed to the effect of correlated motions of the lattice and the rotating group, which are evident from the structural anal. of the at. position data as a function of the dihedral angle of the rotator. The displacements of neighboring mols. near the rotary transition states for 1A and 1B can be as large as 2.7 and 1.1 Å, resp. The displacement and oscillation (C2) of interpenetrating Ph rings from neighboring rotors proximal to the event are significant for both 1A and 1B. In addn., 6-fold (C6) benzene rotations in clathrate 1A were found to be directly correlated to the rotation of the phenylene rotator.
- 28Howe, M. E.; Garcia-Garibay, M. A. The Roles of Intrinsic Barriers and Crystal Fluidity in Determining the Dynamics of Crystalline Molecular Rotors and Molecular Machines. J. Org. Chem. 2019, 84 (16), 9835– 9849, DOI: 10.1021/acs.joc.9b0099328https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtVKgtrrP&md5=85fdc24f1710ed3d0fe269d11304032cThe Roles of Intrinsic Barriers and Crystal Fluidity in Determining the Dynamics of Crystalline Molecular Rotors and Molecular MachinesHowe, Morgan E.; Garcia-Garibay, Miguel A.Journal of Organic Chemistry (2019), 84 (16), 9835-9849CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A review. Cryst. solids are a promising platform for the development of mol. machines. They have the potential of combining the mol.-level control of phys. properties caused by isomerizations, conformational motions, or chem. reactions with the emergent properties that arise from long-range order and multiscale phenomena. The construction of cryst. mol. machinery was challenging due to the difficulties assocd. with the design of structures capable of supporting high order and controlled mol. motion in the solid state, a platform that is termed amphidynamic crystals. With ultrafast rotation as the target, previous work on amphidynamic crystals has explored the creation of free space around the rotator, the advantages of vol.-conserving rotational motions, and the challenges assocd. with correlated rotations, or gearing motions. In this Perspective the authors report the results of a systematic anal. of a large no. of examples from the work and that of others, where the creation of free space alone does not always result in ultrafast dynamics. In a limit that applies to porous crystals with large empty vols. such as MOFs and other extended solids, internal motions fall in the regime of activation control, with dynamics detd. by the intrinsic (gas-phase) electronic barriers for rotation around the bond that connects the rotator and the stator. By contrast, internal rotation in close-packed mol. crystals falls in the regime of diffusion-controlled dynamics and depends on the ability of the rotator surroundings to distort and create transient cavities. The authors refer to this property as crystal fluidity and suggest that it may be used as an addnl. guiding principle for the design of cryst. mol. machines. The authors describe the general principles behind the promising field of cryst. mol. machinery, the anal. methods to analyze rotational dynamics of cryst. solids, and the key structural concepts that may help their future development.
- 29Lemouchi, C.; Iliopoulos, K.; Zorina, L.; Simonov, S.; Wzietek, P.; Cauchy, T.; Rodríguez-Fortea, A.; Canadell, E.; Kaleta, J.; Michl, J.; Gindre, D.; Chrysos, M.; Batail, P. Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational Mutations. J. Am. Chem. Soc. 2013, 135 (25), 9366– 9376, DOI: 10.1021/ja404451729https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXoslSqt7k%253D&md5=e1e325c1a8ea8e2e9bdaa2e0bdf9c3c5Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational MutationsLemouchi, Cyprien; Iliopoulos, Konstantinos; Zorina, Leokadiya; Simonov, Sergey; Wzietek, Pawel; Cauchy, Thomas; Rodriguez-Fortea, Antonio; Canadell, Enric; Kaleta, Jiri; Michl, Josef; Gindre, Denis; Chrysos, Michael; Batail, PatrickJournal of the American Chemical Society (2013), 135 (25), 9366-9376CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The rod-like mol. bis((4-(4-pyridyl)ethynyl)bicyclo[2.2.2]oct-1-yl)buta-1,3-diyne, 1, contains two 1,4-bis(ethynyl)bicyclo[2.2.2]octane (BCO) chiral rotators linked by a diyne fragment and self-assembles in a one-dimensional, monoclinic C2/c centrosym. structure where two equil. positions with large occupancy imbalance (88% vs. 12%) are identified on a single rotor site. Combining variable-temp. (70-300 K) proton spin-lattice relaxation, 1H T1-1, at two different 1H Larmor frequencies (55 and 210 MHz) and DFT calcns. of rotational barriers, we were able to assign two types of Brownian rotators with different activation energies, 1.85 and 6.1 kcal mol-1, to the two 1H spin-lattice relaxation processes on the single rotor site. On the basis of DFT calcns., the low-energy process has been assigned to adjacent rotors in a well-correlated synchronous motion, whereas the high-energy process is the manifestation of an abrupt change in their kinematics once two blades of adjacent rotors are seen to rub together. Although crystals of 1 should be second harmonic inactive, a large second-order optical response is recorded when the elec. field oscillates in a direction parallel to the unique rotor axle director. We conclude that conformational mutations by torsional interconversion of the three blades of the BCO units break space-inversion symmetry in sequences of mutamers in dynamic equil. in the crystal in domains at a mesoscopic scale comparable with the wavelength of light used. A control expt. was performed with a cryst. film of a similar tetrayne mol., 1,4-bis(3-((trimethylsilyl)ethynyl)bicyclo[1.1.1]pent-1-yl)buta-1,3-diyne, whose bicyclopentane units can rotate but are achiral and produce no second-order optical response.
- 30Damron, J. T.; Ma, J.; Kurz, R.; Saalwächter, K.; Matzger, A. J.; Ramamoorthy, A. The Influence of Chemical Modification on Linker Rotational Dynamics in Metal–Organic Frameworks. Angew. Chem., Int. Ed. 2018, 57 (28), 8678– 8681, DOI: 10.1002/anie.20180500430https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFaltb7O&md5=911053f9a1807954ea692b8ea860b9a0The Influence of Chemical Modification on Linker Rotational Dynamics in Metal-Organic FrameworksDamron, Joshua T.; Ma, Jialiu; Kurz, Ricardo; Saalwaechter, Kay; Matzger, Adam J.; Ramamoorthy, AyyalusamyAngewandte Chemie, International Edition (2018), 57 (28), 8678-8681CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The robust synthetic flexibility of metal-org. frameworks (MOF) offers a promising class of tailor-able materials for which the ability to tune specific physicochem. properties is highly desired. This is achievable only through a thorough description of the consequences for chem. manipulations in structure and dynamics. Magic angle spinning solid-state NMR spectroscopy offers many modalities in this pursuit, particularly for dynamic studies. This work used a sepd. local-field NMR approach to show how specific intra-framework chem. modifications to MOF UiO-66 heavily modulated the dynamic evolution of the org. ring moiety over several orders of magnitude.
- 31Zhou, W.; Yildirim, T. Lattice Dynamics of Metal-Organic Frameworks: Neutron Inelastic Scattering and First-Principles Calculations. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 74 (18), 180301, DOI: 10.1103/PhysRevB.74.18030131https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhtlSksLzL&md5=e96393d378d670d1896cb21ed0a6633fLattice dynamics of metal-organic frameworks: Neutron inelastic scattering and first-principles calculationsZhou, W.; Yildirim, T.Physical Review B: Condensed Matter and Materials Physics (2006), 74 (18), 180301/1-180301/4CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)By combining neutron inelastic scattering (NIS) and first-principles calcns., we have investigated the lattice dynamics of metal-org. framework-5 (MOF5). The structural stability of MOF5 was evaluated by calcg. the three cubic elastic consts. We find that the shear modulus, c44 = 1.16 GPA, is unusually small, while two other moduli are relatively large (i.e., c11 = 29.42 GPa and c12 = 12.56 GPa). We predict that MOF5 is very close to structural instability and may yield interesting phases under high pressure and strain. The phonon dispersion curves and phonon d. of states were directly calcd. and our simulated NIS spectrum agrees very well with our exptl. data. Several interesting phonon modes are discussed, including the softest twisting modes of the org. linker.
- 32Ryder, M. R.; Van De Voorde, B.; Civalleri, B.; Bennett, T. D.; Mukhopadhyay, S.; Cinque, G.; Fernandez-Alonso, F.; De Vos, D.; Rudić, S.; Tan, J. C. Detecting Molecular Rotational Dynamics Complementing the Low-Frequency Terahertz Vibrations in a Zirconium-Based Metal-Organic Framework. Phys. Rev. Lett. 2017, 118 (25), 1– 6, DOI: 10.1103/PhysRevLett.118.255502There is no corresponding record for this reference.
- 33Liepuoniute, I.; Huynh, C. M.; Perez-Estrada, S.; Wang, Y.; Khan, S.; Houk, K. N.; Garcia-Garibay, M. A. Enhanced Rotation by Ground State Destabilization in Amphidynamic Crystals of a Dipolar 2,3-Difluorophenylene Rotator as Established by Solid State 2 H NMR and Dielectric Spectroscopy. J. Phys. Chem. C 2020, 124 (28), 15391– 15398, DOI: 10.1021/acs.jpcc.0c0531433https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1als7bE&md5=a00baee64b848515e9706fc9914724e5Enhanced Rotation by Ground State Destabilization in Amphidynamic Crystals of a Dipolar 2,3-Difluorophenylene Rotator as Established by Solid State 2H NMR and Dielectric SpectroscopyLiepuoniute, Ieva; Huynh, Chau Minh; Perez-Estrada, Salvador; Wang, Yangyang; Khan, Saeed; Houk, K. N.; Garcia-Garibay, Miguel A.Journal of Physical Chemistry C (2020), 124 (28), 15391-15398CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)We report the synthesis and rotational dynamics of the pillared metal-org. framework Zn2(F2BDC)2(DABCO) where F2BDC = 2,3-difluorobenzene-1,4-dicarboxylate acts as a rotating dipolar linker and DABCO = 1,4-diazabicyclo[2.2.2]octane acts as a spacer (F2MOF 1). The pillared structure of F2MOF 1 was confirmed by X-ray diffraction and CP-MAS 13C NMR analyses. Using variable temp. solid state 2H NMR and broadband dielec. spectroscopy, we characterized the rotational dynamics of the dipolar F2BDC linker in the solid state. Variable temp. (VT) quadrupolar echo 2H NMR measurements revealed a rotational activation energy of Ea = 6.8 ± 0.1 kcal/mol, which agreed well with temp.- and frequency-dependent dielec. measurements, indicating a barrier of Ea = 7.1 ± 0.5 kcal/mol. Structural data from single crystal X-ray diffraction and quantum mech. calcns. (DFT) suggest that the rotational potential is detd. by steric interactions between the dipolar rotator and the stator linkers such that fluorine atoms in the F2BDC linker reduce the activation energy by destabilization of the coplanar BDC ground state.
- 34Kolokolov, D. I.; Jobic, H.; Stepanov, A. G.; Guillerm, V.; Devic, T.; Serre, C.; Férey, G. Dynamics of Benzene Rings in MIL-53(Cr) and MIL-47(V) Frameworks Studied By2H NMR Spectroscopy. Angew. Chem., Int. Ed. 2010, 49 (28), 4791– 4794, DOI: 10.1002/anie.20100123834https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXotVCgu7Y%253D&md5=5e153c8b326eaf438208f14ae46b8340Dynamics of Benzene Rings in MIL-53(Cr) and MIL-47(V) Frameworks Studied by 2H NMR SpectroscopyKolokolov, Daniil I.; Jobic, Herve; Stepanov, Alexander G.; Guillerm, Vincent; Devic, Thomas; Serre, Christian; Ferey, GerardAngewandte Chemie, International Edition (2010), 49 (28), 4791-4794, S4791/1-S4791/3CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)2H NMR method allowed us to show that the arom. rings in MIL-47(V) and MIL-53(Cr) perform π flips about their symmetry axis. The benzene rings flip faster and with lower activation energy in the flexible MIL-53(Cr) than in the rigid MIL-47(V). This demonstrates that arom. rings in MOFs can be a sensitive marker of the framework structural properties. The terephthalate groups in both MILs can be considered as immobile on a microscopic timescale, in agreement with previous QENS studies and mol. simulations. However, in macroscopic measurements, small mols. like H2, CO2, and CH4 have the possibility to switch from one tunnel to another, and this must be taken into account, for instance, in adsorption or sepn. processes. 2010 Wiley-VCH Verlag GmbH and Co.
- 35Kolokolov, D. I.; Stepanov, A. G.; Jobic, H. Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene Loadings. J. Phys. Chem. C 2014, 118 (29), 15978– 15984, DOI: 10.1021/jp506010p35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVOjt7jF&md5=762caac7292523f0c2ba3d043f5dd359Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene LoadingsKolokolov, Daniil I.; Stepanov, Alexander G.; Jobic, HerveJournal of Physical Chemistry C (2014), 118 (29), 15978-15984CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Large pore (LP) and narrow pore (NP) cryst. state interconversions of the MIL-53(Al) MOF framework has been monitored via following the thermally induced evolution of phenylene fragments using 2H solid-state NMR. The dynamics of phenylene fragments was shown to be very sensitive to the loading of xylene guests and the MOF structural state. The mol. rotation rate was higher and the activation barrier lower for the LP state of the guest-free or loosely loaded material, whereas the NP and LP states with high loadings and dense guest packing showed a decrease of the rotation rates and increase of the rotation energetic barrier.
- 36Khudozhitkov, A. E.; Jobic, H.; Freude, D.; Haase, J.; Kolokolov, D. I.; Stepanov, A. G. Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of Xylene. J. Phys. Chem. C 2016, 120 (38), 21704– 21709, DOI: 10.1021/acs.jpcc.6b0811436https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVWntLrF&md5=81e4e92ea30a9e9c0e5fac8125a46fc8Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of XyleneKhudozhitkov, Alexander E.; Jobic, Herve; Freude, Dieter; Haase, Juergen; Kolokolov, Daniil I.; Stepanov, Alexander G.Journal of Physical Chemistry C (2016), 120 (38), 21704-21709CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)MIL-53 (Al) is an important example of metal-org. frameworks (MOFs) with a flexible framework capable to efficiently sep. ortho and para isomers of xylene at moderate temps. The MIL-53 MOF contains mobile terephthalate phenylene fragments that can be used as a dynamic probe to study the guest-host interactions and the origin of the sepn. selectivity. Here 2H NMR spin alignment echo technique for the 1st time was applied to probe ultraslow structural mobility (0.1-1 kHz) in MOFs materials, with particular application to MIL-53(Al) satd. with ortho or para isomers of xylene. A specific influence of different isomers of xylene adsorbed in the MOF pores on the rotation of the phenylenes in MIL-53 for the temp. range with proved sepn. selectivity (T < 393 K) is shown. The rotation of phenylene fragments is sensitive to the type of xylene isomer. The phenylenes' rotation performs 1 order of magnitude slower in the presence of o-xylene (kortho = 70 s-1) compared to the same rotation in the presence of the other isomer, p-xylene (kpara = 800 s-1) at T ∼ 373 K. This is rationalized by a stronger interaction of the ortho isomer with the linker than the para isomer. This finding offers an understanding of the mol. mechanism of p- and o-xylene sepn. by MIL-53: stronger interaction of o-xylene with org. linker compared to p-xylene provides sepn. of these isomers on MIL-53.
- 37Khudozhitkov, A. E.; Kolokolov, D. I.; Stepanov, A. G.; Bolotov, V. A.; Dybtsev, D. N. Metal-Cation-Independent Dynamics of Phenylene Ring in Microporous MOFs: A 2H Solid-State NMR Study. J. Phys. Chem. C 2015, 119 (50), 28038– 28045, DOI: 10.1021/acs.jpcc.5b0943537https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVCjtbnK&md5=4f00b6c94e1cde9695b63be9a49d199aMetal-Cation-Independent Dynamics of Phenylene Ring in Microporous MOFs: A 2H Solid-State NMR StudyKhudozhitkov, Alexander E.; Kolokolov, Daniil I.; Stepanov, Alexander G.; Bolotov, Vsevolod A.; Dybtsev, Danil N.Journal of Physical Chemistry C (2015), 119 (50), 28038-28045CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Mobility of the org. linkers in metal-org. frameworks (MOFs) is an established phenomenon. Knowledge of the details of linker motion in MOFs could provide a great deal of information about the linker structure and the way the guest mols. interact with the org. framework. However, the mobility of the org. linkers is poorly characterized. The extent of the influence of the metal cation or guest mols. on linker motion is still unknown for MOFs with identical topologies. The authors analyzed the rotational dynamics of the phenylene ring fragments of terephthalate (1,4-benzenedicarboxylate, bdc) linkers in MOFs [M2(bdc)2(dabco)]·G (M = Co2+, Ni2+, Cu2+, Zn2+; dabco =1,4-diazabicyclo[2.2.2]octane; G = none or DMF, DMF). The reorientational motion of the phenylene rings was performed by π-flipping of the plane of the ring about its C2 axis. The dynamics of the phenylene rings is insensitive to the variation of the metal cation, whereas the loading of the guest DMF mols. provides both a significant decrease of the rate of π-flips and an increase of the activation energy for the motion of the phenylene rings.
- 38Gould, S. L.; Tranchemontagne, D.; Yaghi, O. M.; Garcia-Garibay, M. A. Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment. J. Am. Chem. Soc. 2008, 130 (11), 3246– 3247, DOI: 10.1021/ja077122c38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXitFegtrk%253D&md5=109b33711ef380fc414fbf4681127b7cAmphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered EnvironmentGould, Stephanie L.; Tranchemontagne, David; Yaghi, Omar M.; Garcia-Garibay, Miguel A.Journal of the American Chemical Society (2008), 130 (11), 3246-3247CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Metal-org. frameworks (MOFs) have been the focus of much interest within the context of hydrogen storage and other materials applications. With static metal clusters linked by axially substituted org. spacers capable of experiencing internal rotations, MOFs are one of the most promising amphidynamic materials to investigate and exploit the dynamics of cryst. solids. In this communication we report an exptl. study of the rotational dynamics of the 1,4-phenylenedicarboxylate bridge of MOF-5, which has no steric contacts that might contribute to the rotational barrier. Highly reproducible 1H T1 relaxation, high-resoln. 13C CPMAS, and variable temp. quadrupolar echo 2H NMR data were obtained from high quality samples that were sealed at reduced pressure (ca. 3 mTorr). 2H NMR line shape simulation revealed an activation barrier for rotation of 11.3 ± 2.0 kcal/mol, which is lower than the 14-16 kcal/mol values reported in theor. studies of truncated models. While our results suggest that the models used for MOF-5 are insufficient to account for the properties of the extended crystal lattice, they also suggest that the amphidynamic materials with static and dynamic components may reach the friction-free rotational motion characteristic of gas dynamics.
- 39Kolokolov, D. I.; Stepanov, A. G.; Guillerm, V.; Serre, C.; Frick, B.; Jobic, H. Probing the Dynamics of the Porous Zr Terephthalate UiO-66 Framework Using 2H NMR and Neutron Scattering. J. Phys. Chem. C 2012, 116 (22), 12131– 12136, DOI: 10.1021/jp302919339https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmvFGgtrk%253D&md5=e819c06b2f2699b620d49d906d429e4dProbing the Dynamics of the Porous Zr Terephthalate UiO-66 Framework Using 2H NMR and Neutron ScatteringKolokolov, D. I.; Stepanov, A. G.; Guillerm, V.; Serre, C.; Frick, B.; Jobic, H.Journal of Physical Chemistry C (2012), 116 (22), 12131-12136CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)2H NMR and quasi-elastic neutron scattering techniques were used to study the rotational dynamics of the 1,4-benzene-dicarboxylate (BDC) linkers in the porous cubic UiO-66(Zr) metal-org. framework (MOF). The rotation of the benzene rings in the BDC linkers is at the limit of detection of the neutron technique, but it fits perfectly on the 2H NMR time scale. The arom. rings in the UiO-66 framework exhibit the lowest rotational barrier compared to other MOFs, the activation energy for π-flips being 30 kJ mol-1. However, instead of having well-defined flipping rates like in MOF-5, MIL-47, or MIL-53, UiO-66(Zr) shows a distribution of flipping correlation times, probably due to local disorder in the structure. Because of the rotational motion of the benzene rings, the effective size of the microporous windows in UiO-66(Zr) appears to be temp. dependent.
- 40Biswas, S.; Ahnfeldt, T.; Stock, N. New Functionalized Flexible Al-MIL-53-X (X = -Cl, -Br, -CH 3, -NO 2, -(OH) 2) Solids: Syntheses, Characterization, Sorption, and Breathing Behavior. Inorg. Chem. 2011, 50 (19), 9518– 9526, DOI: 10.1021/ic201219g40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtFeksr7J&md5=0d28e50d97d4801ef914d8ccc38da211New Functionalized Flexible Al-MIL-53-X (X = -Cl, -Br, -CH3, -NO2, -(OH)2) Solids: Syntheses, Characterization, Sorption, and Breathing BehaviorBiswas, Shyam; Ahnfeldt, Tim; Stock, NorbertInorganic Chemistry (2011), 50 (19), 9518-9526CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)Five new flexible Al terephthalate deriv. hydroxo frameworks, [Al(OH)(BDC-X)]·n(guests), were prepd. by solvothermal methods [BDC = 1,4-benzene-dicarboxylate; X = 2-chloro (1); 2-bromo (2); 2-Me (3); 2-nitro (4); 2,5-dihydroxy (5)]. The as synthesized (Al-MIL-53-X-AS) as well as the activated compds. were characterized by x-ray powder diffraction (XRPD), IR spectroscopy, thermogravimetric (TG), and elemental anal. Activation, i.e., removal of unreacted H2BDC-X mols. and/or occluded solvent mols., followed by hydration in air at room temp., led to the narrow pore (NP) form of [Al(OH)(BDC-X)]·n(H2O) (Al-MIL-53-X). TGA and temp.-dependent XRPD (TDXRPD) expts. performed on the NP-form of the compds. indicate high thermal stability in the range 325-500°. As verified by N2, CO2, or H2O sorption measurements, most of the thermally activated compds. exhibit significant microporosity. Similar to pristine Al-MIL-53, the present compds. retain their structural flexibility depending on the nature of guest mols. and temp., as verified by cell parameter detn. from XRPD data. The breathing behavior of the functionalized frameworks upon dehydration-rehydration, studied by temp. and time-dependent XRPD measurements, differs significantly compared to parent Al-MIL-53.
- 41Loiseau, T.; Serre, C.; Huguenard, C.; Fink, G.; Taulelle, F.; Henry, M.; Bataille, T.; Férey, G. A Rationale for the Large Breathing of the Porous Aluminum Terephthalate (MIL-53) upon Hydration. Chem. - Eur. J. 2004, 10 (6), 1373– 1382, DOI: 10.1002/chem.20030541341https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXivVykt7s%253D&md5=3a01acd738d767103450cccd3cab8f2eA rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydrationLoiseau, Thierry; Serre, Christian; Huguenard, Clarisse; Fink, Gerhard; Taulelle, Francis; Henry, Marc; Bataille, Thierry; Ferey, GerardChemistry - A European Journal (2004), 10 (6), 1373-1382CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)Al 1,4-benzenedicarboxylate Al(OH)[O2CC6H4CO2][HO2C-C6H4-CO2H]0.70 or MIL-53as (Al) was hydrothermally synthesized by heating a mixt. of Al nitrate, 1,4-benzenedicarboxylic acid, and H2O, for three days at 220°. Its 3 D framework is built up of infinite trans chains of corner-sharing AlO4(OH)2 octahedra. The chains are interconnected by the 1,4-benzenedicarboxylate groups, creating 1 D rhombic-shaped tunnels. Disordered 1,4-benzenedicarboxylic acid mols. are trapped inside these tunnels. Their evacuation upon heating, between 275 and 420°, leads to a nanoporous open-framework (MIL-53ht (Al) or Al(OH)[O2CC6H4CO2]) with empty pores of diam. 8.5 Å. This solid exhibits a Langmuir surface area. of 1590(1) m2g-1 together with a remarkable thermal stability, since it starts to decomp. only at 500°. At room temp., the solid reversibly absorbs H2O in its tunnels, causing a very large breathing effect and shrinkage of the pores. Anal. of the hydration process by solid-state NMR (1H, 13C, 27Al) has clearly indicated that the trapped H2O mols. interact with the carboxylate groups through H bonds, but do not affect the hydroxyl species bridging the Al atoms. The H bonds between H2O and the O atoms of the framework are responsible for the contraction of the rhombic channels. The structures of the three forms were detd. by powder x-ray diffraction anal. Crystal data for MIL-53as (Al) are as follows: orthorhombic system, Pnma (no. 62), a 17.129(2), b 6.628(1), c 12.182(1) Å; for MIL-53ht (Al), orthorhombic system, Imma (no. 74), a 6.608(1), b 16.675(3), c 12.813(2) Å; for MIL-53lt (Al), monoclinic system, Cc (no. 9), a 19.513(2), b 7.612(1), c 6.576(1) Å, β 104.24(1)°.
- 42Liu, Y.; Her, J. H.; Dailly, A.; Ramirez-Cuesta, A. J.; Neumann, D. A.; Brown, C. M. Reversible Structural Transition in MIL-53 with Large Temperature Hysteresis. J. Am. Chem. Soc. 2008, 130 (35), 11813– 11818, DOI: 10.1021/ja803669w42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXps1Knt74%253D&md5=0d06ce91da90c73847b704c1ae49016fReversible Structural Transition in MIL-53 with Large Temperature HysteresisLiu, Yun; Her, Jae-Hyuk; Dailly, Anne; Ramirez-Cuesta, Anibal J.; Neumann, Dan A.; Brown, Craig M.Journal of the American Chemical Society (2008), 130 (35), 11813-11818CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The metal-org. framework, MIL-53, can have a structural transition from an open-pored to a closed-pored structure by adsorbing different guest mols. The aid of guest mols. is believed to be necessary to initiate this "breathing" effect. Using both neutron powder diffraction and inelastic neutron scattering techniques, we find that MIL-53 exhibits a reversible structural transition between an open-pored and a closed-pored structure as a function of temp. without the presence of any guest mols. Surprisingly, this structural transition shows a significant temp. hysteresis: the transition from the open-pored to closed-pored structure occurs at approx. 125 to 150 K, while the transition from the closed-pored to open-pored structure occurs around 325 to 375 K. To our knowledge, this is first observation of such a large temp. hysteresis of a structural transition in metal-org. frameworks. We also note that the transition from the open to closed structure at low temp. shows very slow kinetics. An ab initio computer simulation is employed to investigate the possible mechanism of the transition.
- 43Munn, A. S.; Pillai, R. S.; Biswas, S.; Stock, N.; Maurin, G.; Walton, R. I. The Flexibility of Modified-Linker MIL-53 Materials. Dalt. Trans. 2016, 45 (10), 4162– 4168, DOI: 10.1039/C5DT03438HThere is no corresponding record for this reference.
- 44Stavitski, E.; Pidko, E. A.; Couck, S.; Remy, T.; Hensen, E. J. M.; Weckhuysen, B. M.; Denayer, J.; Gascon, J.; Kapteijn, F. Complexity behind CO2 Capture on NH2-MIL-53(Al). Langmuir 2011, 27 (7), 3970– 3976, DOI: 10.1021/la104520744https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXivVShsrc%253D&md5=e9ebca4338eb83c2165b3582601dd610Complexity behind CO2 Capture on NH2-MIL-53(Al)Stavitski, Eli; Pidko, Evgeny A.; Couck, Sarah; Remy, Tom; Hensen, Emiel J. M.; Weckhuysen, Bert M.; Denayer, Joeri; Gascon, Jorge; Kapteijn, FreekLangmuir (2011), 27 (7), 3970-3976CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Some Metal Org. Frameworks (MOFs) show excellent performance in extg. carbon dioxide from different gas mixts. The origin of their enhanced sepn. ability is not clear yet. Herein, the authors present a combined exptl. and theor. study of the amino-functionalized MIL-53(Al) to elucidate the mechanism behind its unusual high efficiency in CO2 capture. Spectroscopic and DFT studies point out only an indirect role of amine moieties. In contrast to other amino-functionalized CO2 sorbents, no chem. bond between CO2 and the NH2 groups of the structure is formed. The functionalization modulates the breathing behavior of the material, i.e., the flexibility of the framework and its capacity to alter the structure upon the introduction of specific adsorbates. The absence of strong chem. interactions with CO2 is of high importance for the overall performance of the adsorbent, since full regeneration can be achieved within minutes under very mild conditions, demonstrating the high potential of this type of adsorbents for PSA like systems.
- 45Shustova, N. B.; Ong, T.-C.; Cozzolino, A. F.; Michaelis, V. K.; Griffin, R. G.; Dinca, M. Phenyl Ring Dynamics in a Tetraphenylethylene-Bridged Metal–Organic Framework: Implications for the Mechanism of Aggregation-Induced Emission. J. Am. Chem. Soc. 2012, 134 (36), 15061– 15070, DOI: 10.1021/ja306042w45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFOru77O&md5=3b5bb9537c96ed99cf65c5a14bd9ca02Phenyl Ring Dynamics in a Tetraphenylethylene-Bridged Metal-Organic Framework: Implications for the Mechanism of Aggregation-Induced EmissionShustova, Natalia B.; Ong, Ta-Chung; Cozzolino, Anthony F.; Michaelis, Vladimir K.; Griffin, Robert G.; Dinca, MirceaJournal of the American Chemical Society (2012), 134 (36), 15061-15070CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Mols. that exhibit emission in the solid state, esp. those known as aggregation-induced emission (AIE) chromophores, found applications in areas as varied as light-emitting diodes and biol. sensors. Despite numerous studies, the mechanism of fluorescence quenching in AIE chromophores is still not completely understood. To this end, much interest has focused on understanding the low-frequency vibrational dynamics of prototypical systems, such as tetraphenylethylene (TPE), in the hope that such studies would provide more general principles toward the design of new sensors and electronic materials. The authors hereby show that a perdeuterated TPE-based metal-org. framework (MOF) serves as an excellent platform for studying the low-energy vibrational modes of AIE-type chromophores. In particular, the authors use solid-state 2H and 13C NMR expts. to study the Ph ring dynamics of TPE cores that are coordinatively trapped inside a MOF and find a Ph ring flipping energy barrier of 43(6) kJ/mol. DFT calcns. are then used to deconvolute the electronic and steric contributions to this flipping barrier. Finally, the authors couple the NMR and DFT studies with variable-temp. x-ray diffraction expts. to propose that both the ethylenic C=C bond twist and the torsion of the Ph rings are important for quenching emission in TPE, but that the former may gate the latter. To conclude, the authors use these findings to propose a set of design criteria for the development of tunable turn-on porous sensors constructed from AIE-type mols., particularly as applied to the design of new multifunctional MOFs.
- 46Kolokolov, D. I.; Stepanov, A. G.; Jobic, H. SI: Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene Loadings. J. Phys. Chem. C 2014, 118 (29), 15978– 15984, DOI: 10.1021/jp506010p46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVOjt7jF&md5=762caac7292523f0c2ba3d043f5dd359Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene LoadingsKolokolov, Daniil I.; Stepanov, Alexander G.; Jobic, HerveJournal of Physical Chemistry C (2014), 118 (29), 15978-15984CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Large pore (LP) and narrow pore (NP) cryst. state interconversions of the MIL-53(Al) MOF framework has been monitored via following the thermally induced evolution of phenylene fragments using 2H solid-state NMR. The dynamics of phenylene fragments was shown to be very sensitive to the loading of xylene guests and the MOF structural state. The mol. rotation rate was higher and the activation barrier lower for the LP state of the guest-free or loosely loaded material, whereas the NP and LP states with high loadings and dense guest packing showed a decrease of the rotation rates and increase of the rotation energetic barrier.
- 47Balčiu̅nas, S.; Simenas, M.; Pavlovaite, D.; Kinka, M.; Shieh, F.-K.; Wu, K. C.-W.; Banys, J.; Grigalaitis, R. Low-Frequency Dipolar Dynamics and Atmospheric Effects in ZIF-90 Metal–Organic Framework. J. Phys. Chem. C 2019, 123 (1), 631– 636, DOI: 10.1021/acs.jpcc.8b1086247https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisVOit73E&md5=81b6cf58596a76cfd3fc13c2eab07703Low-Frequency Dipolar Dynamics and Atmospheric Effects in ZIF-90 Metal-Organic FrameworkBalciunas, Sergejus; Simenas, Mantas; Pavlovaite, Diana; Kinka, Martynas; Shieh, Fa-Kuen; Wu, Kevin C.-W.; Banys, Juras; Grigalaitis, RobertasJournal of Physical Chemistry C (2019), 123 (1), 631-636CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Remarkable gas adsorption properties of zeolitic imidazolate frameworks (ZIFs) are believed to be tightly related to a flexible nature of org. linkers in these compds. We present a low-frequency dielec. spectroscopy study of dynamic effects in a ZIF-90 hybrid compd. Expts. of dehydrated framework reveal slow motion of the imidazolate-2-carboxyaldehyde linker in the kilohertz frequency range. Measurements of hydrated compd. indicate two addnl. dynamic processes related to the adsorbed water mols. These processes are assigned to the proton cond. and relaxation of the supercooled water confined within the pores of the framework. We also study linker dynamics of dehydrated ZIF-90 in vacuum and under different gas atms., revealing that the linker motion is significantly hindered by the guest mols.
- 48Winston, E. B.; Lowell, P. J.; Vacek, J.; Chocholoušová, J.; Michl, J.; Price, J. C. Dipolar Molecular Rotors in the Metal–Organic Framework Crystal IRMOF-2. Phys. Chem. Chem. Phys. 2008, 10 (34), 5188, DOI: 10.1039/b808104b48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtVektLnK&md5=19b1e4689972550860e27fa3aa5874deDipolar molecular rotors in the metal-organic framework crystal IRMOF-2Winston, Erick B.; Lowell, Peter J.; Vacek, Jaroslav; Chocholousova, Jana; Michl, Josef; Price, John C.Physical Chemistry Chemical Physics (2008), 10 (34), 5188-5191CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Rotating polar linker groups in the cubic metal-org. framework single crystal known as IRMOF-2 were studied for freedom of motion, response to an external elec. field, and effects of dipole-dipole interactions. The crystals consist of octahedrally coordinated zinc oxide clusters linked by the bromoterephthalate group, which contains a rotatable bromo-p-phenylene moiety. The authors confirmed the rotation by dielec. spectroscopy and found a 7.3 kcal mol-1 barrier. The nonpolar analog, IRMOF-1, contg. terephthalic acid, was used as a control system. DFT and MP2 computations of the rotational barrier yield results in agreement with the observation, with B3LYP/SDD being the best. A Monte Carlo anal. of the equil. polarization fluctuations was used to assess the possibility of polar ordering and the potential for electrooptic applications.
- 49Devautour-Vinot, S.; Maurin, G.; Serre, C.; Horcajada, P.; Paula Da Cunha, D.; Guillerm, V.; De Souza Costa, E.; Taulelle, F.; Martineau, C. Structure and Dynamics of the Functionalized MOF Type UiO-66(Zr): NMR and Dielectric Relaxation Spectroscopies Coupled with DFT Calculations. Chem. Mater. 2012, 24 (11), 2168– 2177, DOI: 10.1021/cm300863c49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XntlOgu7Y%253D&md5=371fdbbaaaede06ced5e363fd614e4f2Structure and Dynamics of the Functionalized MOF Type UiO-66(Zr): NMR and Dielectric Relaxation Spectroscopies Coupled with DFT CalculationsDevautour-Vinot, Sabine; Maurin, Guillaume; Serre, Christian; Horcajada, Patricia; Paula da Cunha, Denise; Guillerm, Vincent; de Souza Costa, Elisangela; Taulelle, Francis; Martineau, CharlotteChemistry of Materials (2012), 24 (11), 2168-2177CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Advanced 1- and 2-dimensional high-field and ultrafast MASNMR measurements were conducted in tandem with DFT calcns. for the NMR parameters to deeply characterize the local environment and the long-range structure order of the porous metal-org. framework (MOF) type UiO-66(Zr) (UiO for University of Oslo) functionalized by polar -Br, -2OH, and -NH2 groups. Such an innovative combining approach applied to the complex architecture of MOFs was revealed successful not only to unambiguously assign all the NMR signals to the corresponding crystallog. sites but also to validate the crystal structures for each functionalized material that were only predicted so far. A further step consisted of probing the impact of the grafted functions on the ligand dynamics of these MOFs by dielec. relaxation spectroscopy measurements. It was evidenced that the rotational motion of the org. linker requires overpassing an energy barrier that strongly depends on the functional groups, the -NH2 functionalized version implying the highest activation energy. Such a finding was further explained by the relatively strong intraframework interactions which take place between the grafted function and the inorg. node as suggested by the anal. of the corresponding simulated crystal structure.
- 50Kremer, A.; Schönhals, F. Theory of Dielectric Relaxation. In Broadband Dielectric Spectroscopy; Springer-Verlag: Berlin Heidelberg, 2003; pp 1– 33. DOI: 10.1007/978-3-642-56120-7_1 .There is no corresponding record for this reference.
- 51Frunza, S.; Schönhals, A.; Frunza, L.; Ganea, P.; Kosslick, H.; Harloff, J.; Schulz, A. Molecular Relaxation Processes in a MOF-5 Structure Revealed by Broadband Dielectric Spectroscopy: Signature of Phenylene Ring Fluctuations. J. Phys. Chem. B 2010, 114 (40), 12840– 12846, DOI: 10.1021/jp107161751https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtFKlu77F&md5=86c3ccbb9f1e84ee565cd29ce800ce34Molecular Relaxation Processes in a MOF-5 Structure Revealed by Broadband Dielectric Spectroscopy: Signature of Phenylene Ring FluctuationsFrunza, Stefan; Schoenhals, Andreas; Frunza, Ligia; Ganea, Paul; Kosslick, Hendrik; Harloff, Joerg; Schulz, AxelJournal of Physical Chemistry B (2010), 114 (40), 12840-12846CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)The mol. mobility of a MOF-5 metal-org. framework was investigated by broadband dielec. spectroscopy. Three relaxation processes were revealed. The temp. dependence of their relaxation rates follows an Arrhenius law. The process obsd. at lower temps. is attributed to bending fluctuations of the edges of the cages involving the Zn-O clusters. The processes ("region II") at higher temps. were assigned to fluctuations of Ph rings in agreement with the NMR data found by Gould et al. The carboxylate groups might also be involved. The rotational fluctuations of the Ph rings leading to the low frequency part of relaxation region II might be hindered either by some solvent mols. entrapped in the cages or by an interpenetrated structure and have a broad distribution of activation energies. The high frequency part of region II corresponds nearly to a Debye-like process: This is explained by a well-defined structure of empty pores.
- 52Knebel, A.; Geppert, B.; Volgmann, K.; Kolokolov, D. I.; Stepanov, A. G.; Twiefel, J.; Heitjans, P.; Volkmer, D.; Caro, J. Defibrillation of Soft Porous Metal-Organic Frameworks with Electric Fields. Science 2017, 358 (6361), 347– 351, DOI: 10.1126/science.aal245652https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1Kns7%252FE&md5=65943f86316595f45313607e789d3d52Defibrillation of soft porous metal-organic frameworks with electric fieldsKnebel, A.; Geppert, B.; Volgmann, K.; Kolokolov, D. I.; Stepanov, A. G.; Twiefel, J.; Heitjans, P.; Volkmer, D.; Caro, J.Science (Washington, DC, United States) (2017), 358 (6361), 347-351CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Gas transport through metal-org. framework membranes (MOFs) was switched in situ by applying an external elec. field (E-field). The switching of gas permeation upon E-field polarization could be explained by the structural transformation of the zeolitic imidazolate framework ZIF-8 into polymorphs with more rigid lattices. Permeation measurements under a direct-current E-field poling of 500 V per mm showed reversibly controlled switching of the ZIF-8 into polar polymorphs, which was confirmed by x-ray diffraction and ab initio calcns. The stiffening of the lattice causes a redn. in gas transport through the membrane and sharpens the mol. sieving capability. Dielec. spectroscopy, polarization, and deuterium NMR studies revealed low-frequency resonances of ZIF-8 that we attribute to lattice flexibility and linker movement. Upon E-field polarization, we obsd. a defibrillation of the different lattice motions.
- 53Horansky, R. D.; Clarke, L. I.; Price, J. C.; Khuong, T. A. V; Jarowski, P. D.; Garcia-Garibay, M. A. Dielectric Response of a Dipolar Molecular Rotor Crystal. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72 (1), 1– 5, DOI: 10.1103/PhysRevB.72.014302There is no corresponding record for this reference.
- 54Horansky, R. D.; Clarke, L. I.; Winston, E. B.; Price, J. C.; Karlen, S. D.; Jarowski, P. D.; Santillan, R.; Garcia-Garibay, M. A. Dipolar Rotor-Rotor Interactions in a Difluorobenzene Molecular Rotor Crystal. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 74 (5), 1– 12, DOI: 10.1103/PhysRevB.74.054306There is no corresponding record for this reference.
- 55Jiang, X.; O’Brien, Z. J.; Yang, S.; Lai, L. H.; Buenaflor, J.; Tan, C.; Khan, S.; Houk, K. N.; Garcia-Garibay, M. A. Crystal Fluidity Reflected by Fast Rotational Motion at the Core, Branches, and Peripheral Aromatic Groups of a Dendrimeric Molecular Rotor. J. Am. Chem. Soc. 2016, 138 (13), 4650– 4656, DOI: 10.1021/jacs.6b0139855https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XktFejsrs%253D&md5=fbf49fbb0235f2e9a0b05a30b24f87d3Crystal Fluidity Reflected by Fast Rotational Motion at the Core, Branches, and Peripheral Aromatic Groups of a Dendrimeric Molecular RotorJiang, Xing; O'Brien, Zachary J.; Yang, Song; Lai, Lan Huong; Buenaflor, Jeffrey; Tan, Colleen; Khan, Saeed; Houk, K. N.; Garcia-Garibay, Miguel A.Journal of the American Chemical Society (2016), 138 (13), 4650-4656CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Low packing densities are key structural features of amphidynamic crystals built with static and mobile components. Here we report a loosely packed crystal of dendrimeric rotor 2 (I) and the fast dynamics of all its arom. groups, both resulting from the hyperbranched structure of the mol. Compd. 2 was synthesized with a convergent strategy to construct a central phenylene core with stators consisting of two layers of triarylmethyl groups. Single crystal X-ray diffraction anal. confirmed a low-d. packing structure consisting of one mol. of 2 and approx. eight solvent mols. per unit cell. Three isotopologues of 2 were synthesized to study the motion of each segment of the mol. in the solid state using variable temp. quadrupolar echo 2H NMR spectroscopy. Line shape anal. of the spectra reveals that the central phenylene, the six branch phenylenes, and the 18 periphery phenyls all display megahertz rotational dynamics in the crystals at ambient temp. Arrhenius anal. of the data gives similar activation energies and pre-exponential factors for different parts of the structure. The obsd. pre-exponential factors are 4-6 orders of magnitude greater than those of elementary site-exchange processes, indicating that the dynamics are not dictated by static energetic potentials. Instead, the activation energies for rotations in the crystals of 2 are controlled by temp. dependent local structural fluctuations and crystal fluidity.
- 56Hansen, M. R.; Graf, R.; Spiess, H. W. Solid-State NMR in Macromolecular Systems: Insights on How Molecular Entities Move. Acc. Chem. Res. 2013, 46 (9), 1996– 2007, DOI: 10.1021/ar300338b56https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjvVKku7g%253D&md5=273ff0f58be4bacb773abcaf5a2b37e3Solid-State NMR in Macromolecular Systems: Insights on How Molecular Entities MoveHansen, Michael Ryan; Graf, Robert; Spiess, Hans WolfgangAccounts of Chemical Research (2013), 46 (9), 1996-2007CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. The function of synthetic and natural macromol. systems critically depends on the packing and dynamics of the individual components of a given system. Not only can solid-state NMR provide structural information with at. resoln., but it can also provide a way to characterize the amplitude and time scales of motions over broad ranges of length and time. These movements include mol. dynamics, rotational and translational motions of the building blocks, and also the motion of the functional species themselves, such as protons or ions. This Account examines solid-state NMR methods for correlating dynamics and function in a variety of chem. systems. In the early days, scientists thought that the rotational motions reflected the geometry of the moving entities. They described these phenomena as jumps about well-defined axes, such as Ph flips, even in amorphous polymers. Later, they realized that conformational transitions in macromols. happen in a much more complex way. Because the individual entities do not rotate around well-defined axes, they require much less space. Only recently researchers have appreciated the relative importance of large angle fluctuations of polymers over rotational jumps. Researchers have long considered that cooperative motions might be at work, yet only recently they have clearly detected these motions by NMR in macromol. and supramol. systems. In correlations of dynamics and function, local motions do not always provide the mechanism of long-range transport. This idea holds true in ion conduction but also applies to chain transport in polymer melts and semicryst. polymers. Similar chain motions and ion transport likewise occur in functional biopolymers, systems where solid-state NMR studies are also performed. In polymer science, researchers have appreciated the unique information on mol. dynamics available from advanced solid-state NMR at times, where their colleagues in the biomacromol. sciences have emphasized structure. By contrast, following X-ray crystallographers, researchers studying proteins using soln. NMR introduced the combination of NMR with computer simulation before that became common practice in solid-state NMR. Today's simulation methods can handle partially ordered or even disordered systems common in synthetic polymers. Thus, the multitechnique approaches employed in NMR of synthetic and biol. macromols. have converged. Therefore, this Account will be relevant to both researchers studying synthetic macromol. and supramol. systems and those studying biol. complexes.
- 57Spiess, H. W. Molecular Dynamics of Solid Polymers as Revealed by Deuteron NMR. Colloid Polym. Sci. 1983, 261, 193– 209, DOI: 10.1007/BF0146966457https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3sXhvFyqsLw%253D&md5=9f278078daad59f05ce3d9189264deecMolecular dynamics of solid polymers as revealed by deuteron NMRSpiess, H. W.Colloid and Polymer Science (1983), 261 (3), 193-209CODEN: CPMSB6; ISSN:0303-402X.A review with 92 refs.
- 58Khudozhitkov, A. E.; Jobic, H.; Freude, D.; Haase, J.; Kolokolov, D. I.; Stepanov, A. G. Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of Xylene. J. Phys. Chem. C 2016, 120 (38), 21704– 21709, DOI: 10.1021/acs.jpcc.6b0811458https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVWntLrF&md5=81e4e92ea30a9e9c0e5fac8125a46fc8Ultraslow Dynamics of a Framework Linker in MIL-53 (Al) as a Sensor for Different Isomers of XyleneKhudozhitkov, Alexander E.; Jobic, Herve; Freude, Dieter; Haase, Juergen; Kolokolov, Daniil I.; Stepanov, Alexander G.Journal of Physical Chemistry C (2016), 120 (38), 21704-21709CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)MIL-53 (Al) is an important example of metal-org. frameworks (MOFs) with a flexible framework capable to efficiently sep. ortho and para isomers of xylene at moderate temps. The MIL-53 MOF contains mobile terephthalate phenylene fragments that can be used as a dynamic probe to study the guest-host interactions and the origin of the sepn. selectivity. Here 2H NMR spin alignment echo technique for the 1st time was applied to probe ultraslow structural mobility (0.1-1 kHz) in MOFs materials, with particular application to MIL-53(Al) satd. with ortho or para isomers of xylene. A specific influence of different isomers of xylene adsorbed in the MOF pores on the rotation of the phenylenes in MIL-53 for the temp. range with proved sepn. selectivity (T < 393 K) is shown. The rotation of phenylene fragments is sensitive to the type of xylene isomer. The phenylenes' rotation performs 1 order of magnitude slower in the presence of o-xylene (kortho = 70 s-1) compared to the same rotation in the presence of the other isomer, p-xylene (kpara = 800 s-1) at T ∼ 373 K. This is rationalized by a stronger interaction of the ortho isomer with the linker than the para isomer. This finding offers an understanding of the mol. mechanism of p- and o-xylene sepn. by MIL-53: stronger interaction of o-xylene with org. linker compared to p-xylene provides sepn. of these isomers on MIL-53.
- 59Serra-Crespo, P.; Van Der Veen, M. A.; Gobechiya, E.; Houthoofd, K.; Filinchuk, Y.; Kirschhock, C. E. A.; Martens, J. A.; Sels, B. F.; De Vos, D. E.; Kapteijn, F.; Gascon, J. NH2-MIL-53(Al): A High-Contrast Reversible Solid-State Nonlinear Optical Switch. J. Am. Chem. Soc. 2012, 134 (20), 8314– 8317, DOI: 10.1021/ja300655f59https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmvV2nsLY%253D&md5=5c2d17972ea8024a717a721f608e0d2cNH2-MIL-53(Al): A High-Contrast Reversible Solid-State Nonlinear Optical SwitchSerra-Crespo, Pablo; van der Veen, Monique A.; Gobechiya, Elena; Houthoofd, Kristof; Filinchuk, Yaroslav; Kirschhock, Christine E. A.; Martens, Johan A.; Sels, Bert F.; De Vos, Dirk E.; Kapteijn, Freek; Gascon, JorgeJournal of the American Chemical Society (2012), 134 (20), 8314-8317CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The metal-org. framework NH2-MIL-53(Al) is the 1st solid-state material displaying nonlinear optical switching due to a conformational change upon breathing. A switching contrast of at least 38 was obsd. This transition originates in the restrained linker mobility in the very narrow pore configuration.
- 60Spiess, H. W. Deuteron NMR — a New Tool for Studying Chain Mobility and Orientation in Polymers. In Characterization of Polymers in the Solid State I: Part A: NMR and Other Spectroscopic Methods Part B: Mechanical Methods.; Kaush, H. H., Zachman, H. G., Eds.; Springer: Berlin, Heidelberg, 1985; pp 23– 58. DOI: 10.1007/3-540-13779-3_16 .There is no corresponding record for this reference.
- 61Gedat, E.; Schreiber, A.; Albrecht, J.; Emmler, T.; Shenderovich, I.; Findenegg, G. H.; Limbach, H. H.; Buntkowsky, G. 2H-Solid-State NMR Study of Benzene-D6confined in Mesoporous Silica SBA-15. J. Phys. Chem. B 2002, 106 (8), 1977– 1984, DOI: 10.1021/jp012391p61https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XptVOltA%253D%253D&md5=546d984bf2aa7c18812adb7304eaf8aa2H-Solid-State NMR Study of Benzene-d6 Confined in Mesoporous Silica SBA-15Gedat, E.; Schreiber, A.; Albrecht, J.; Emmler, Th.; Shenderovich, I.; Findenegg, G. H.; Limbach, H.-H.; Buntkowsky, G.Journal of Physical Chemistry B (2002), 106 (8), 1977-1984CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)Benzene-d6 confined in the hexagonal ordered cylindrical pores of mesoporous silica SBA-15 (pore diam. 8.0 nm) was studied by low-temp. 2H-solid-state NMR spectroscopy at 236-19 K and compared to bulk benzene-d6. The solid-state spectra of the bulk benzene-d6 exhibit quadrupolar Pake patterns at high and low temps., and in the intermediate temp. regime the typical line shape changes caused by rotational jumps around the 6-fold axis. At all temps. the benzene mols. are characterized by a single rotational correlation time. For benzene-d6 confined in SBA-15, however, these exchange dominated line shapes are not found. At all temps. below the f.p. the spectra of benzene in the silica show the coexistence of two states with temp.-dependent intensity ratios. This behavior is the result of a Gaussian distributions of activation energies for the rotational jumps inside the pores. For the solid I-solid II (fast 6-fold jump to slow 6-fold jump) transition the center of the distribution is at 40 K (6.0 kJ/mol) with a width of 19.5 K (2.9 kJ/mol). For the liq.-solid I (liq.-like to fast 6-fold jump) transition the center of the distribution is at 204 K (30.6 kJ/mol) and the width is 15 K (2.2 kJ/mol). From the pore vol. and the filling factor, a thickness of four mol. layers of this surface phase is estd.
- 62Larsen, F. H. Simulation of Molecular Motion of Quadrupolar Nuclei in Solid-State NMR Spectra. In Annu. Rep. NMR Spectrosc.; Elsevier Ltd, 2010; Vol. 71, pp 103– 137. DOI: 10.1016/B978-0-08-089054-8.00004-6 .There is no corresponding record for this reference.
- 63Aliev, A. E.; Mann, S. E.; Rahman, A. S.; McMillan, P. F.; Cora, F.; Iuga, D.; Hughes, C. E.; Harris, K. D. M. High-Resolution Solid-State H-2 NMR Spectroscopy of Polymorphs of Glycine. J. Phys. Chem. A 2011, 115 (44), 12201– 12211, DOI: 10.1021/jp207592u63https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlWjtbzK&md5=e8068019ea5b9937d275e3d4f7959357High-Resolution Solid-State 2H NMR Spectroscopy of Polymorphs of GlycineAliev, Abil E.; Mann, Sam E.; Rahman, Aisha S.; McMillan, Paul F.; Cora, Furio; Iuga, Dinu; Hughes, Colan E.; Harris, Kenneth D. M.Journal of Physical Chemistry A (2011), 115 (44), 12201-12211CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)High-resoln. solid-state 2H MAS NMR studies of the α and γ polymorphs of fully deuterated glycine (glycine-d5) are reported. Anal. of spinning sideband patterns is used to det. the 2H quadrupole interaction parameters, and is shown to yield good agreement with the corresponding parameters detd. from single-crystal 2H NMR measurements (the max. deviation in quadrupole coupling consts. detd. from these two approaches is only 1%). From anal. of simulated 2H MAS NMR sideband patterns as a function of reorientational jump frequency (κ) for the -N+D3 group in glycine-d5, the exptl. obsd. differences in the 2H MAS NMR spectrum for the -N+D3 deuterons in the α and γ polymorphs is attributed to differences in the rate of reorientation of the -N+D3 group. These simulations show severe broadening of the 2H MAS NMR signal in the intermediate motion regime, suggesting that deuterons undergoing reorientational motions at rates in the range κ ≈ 104-106 s-1 are likely to be undetectable in 2H MAS NMR measurements for materials with natural isotopic abundances. The 1H NMR chem. shifts for the α and γ polymorphs of glycine have been detd. from the 2H MAS NMR results, taking into account the known second-order shift. Further quantum mech. calcns. of 2H quadrupole interaction parameters and 1H chem. shifts reveal the structural dependence of these parameters in the two polymorphs and suggest that the existence of two short intermol. C-H···O contacts for one of the H atoms of the >CH2 group in the α polymorph have a significant influence on the 2H quadrupole coupling and 1H chem. shift for this site.
- 64Schadt, R. J.; Cain, E. J.; English, A. D. Simulation of One-Dimensional Deuteron NMR Line Shapes. J. Phys. Chem. 1993, 97 (32), 8387– 8392, DOI: 10.1021/j100134a00564https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXlslalsL0%253D&md5=2413c9162dc27432baba2cef71c2b6d0Simulation of one-dimensional deuteron NMR line shapesSchadt, R. J.; Cain, E. J.; English, A. D.Journal of Physical Chemistry (1993), 97 (32), 8387-92CODEN: JPCHAX; ISSN:0022-3654.The detn. of the mol. mechanics involved in a bond reorientation process from the simulation of 1-dimensional 2H NMR spectra is considered for a variety of models. Anisotropic line shape distortions and the accompanying refocusing efficiency factors are essential in identifying the general characteristics of the motional process. The utility of employing a basis set of simulations for an initial anal. of exptl. data where a distribution of correlation times is required to fit the exptl. data is illustrated for the 120° jump or π-flip model.
- 65Leisen, J.; Ohlemacher, A.; Boeffel, C.; Spiess, H. W. Molecular Dynamics in Side-Group Polymers with and without Liquid Crystalline Phases from 2H NMR. Berichte der Bunsengesellschaft für Phys. Chemie 1993, 97 (10), 1306– 1311, DOI: 10.1002/bbpc.19930971019There is no corresponding record for this reference.
- 66Pschorn, U.; Spiess, H. W.; Hisgen, B.; Ringsdorf, H. Deuteron NMR Study of Molecular Order and Motion of the Mesogenic Side Groups in Liquid-crystalline Polymers. Makromol. Chem. 1986, 187 (11), 2711– 2723, DOI: 10.1002/macp.1986.02187112166https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXjtlOjtw%253D%253D&md5=e4dc35a1e6377b7c71e96cf8b82bb954Deuteron NMR study of molecular order and motion of the mesogenic side groups in liquid-crystalline polymersPschorn, Uwe; Spiess, Hans Wolfgang; Hisgen, Bernd; Ringsdorf, HelmutMakromolekulare Chemie (1986), 187 (11), 2711-23CODEN: MACEAK; ISSN:0025-116X.The mol. order and mobility of 2 liq.-cryst. polyacrylates with Ph benzoate moieties as mesogenic side groups and (CH2)m spacers (m = 2, 6) were investigated by pulsed 2H NMR. The mesogenic side groups were isotopically labeled at the terminal phenylene ring. In the glassy state the orientational distribution function was characterized from the angular dependence of the 2H NMR line shape of samples macroscopically ordered in their nematic phase by the 8.4 T magnetic field of an NMR spectrometer. It was Gaussian with widths of ±18.5° and ±10.5° for the m = 2 frozen nematic and m = 6 frozen smectic system, resp. The phenylene rings undergo 180° jumps about their local C2-axes in the glassy state. The time-scale of this process, however, was not uniform. Instead, the anal. of 2H NMR line shapes and their intensities as a function of temp. yielded a log-Gaussian distribution with correlation times characteristic of amorphous solids, 2.2 vs. 2.5 decades in width and mean activation energy 42 vs. 47 kJ/mol for the m = 2 and m = 6 system, resp. The correlation times for the center of the distribution agree with thoseobtained by dielec. relaxation measurements of the same systems, suggesting that reorientation of the whole mesogenic group is detected via the phenylene rings.
- 67Wehrle, M.; Hellmann, G. P.; Spiess, H. W. Phenylene Motion in Polycarbonate and Polycarbonate/Additive Mixtures. Colloid Polym. Sci. 1987, 265 (9), 815– 822, DOI: 10.1007/BF0141845867https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXmtFygt7k%253D&md5=850347857a2c6752c224607c71f2ea3cPhenylene motion in polycarbonate and polycarbonate/additive mixturesWehrle, M.; Hellmann, G. P.; Spiess, H. W.Colloid and Polymer Science (1987), 265 (9), 815-22CODEN: CPMSB6; ISSN:0303-402X.The large angle motions of phenylene groups in bisphenol A polycarbonate as detd. by pulsed deuterium NMR were related to the β-relaxation since both processes occurred on comparable time scales with similar activation energies and were suppressed by low-mol.-wt. additives (1,4-dichlorobenzene and PCB). The motional mechanism involved π-flips about the C1C4 axis augmented by small-angle fluctuations about the same axis, reaching a root-mean-square amplitude of ±35° at 380 K. The distribution of correlation times for the π-flips was heterogeneous in nature and could be described by either a log-Gaussian or an asym. distribution with a more rapid decay at high correlation times comparable to the Williams-Watts distribution. An av. activation energy of 37 kJ/mol was obtained for both distributions, whereas the temp.-dependent width of the highly asym. distribution was smaller than that of the log-Gaussian distribution.
- 68O’Dell, L. A.; Ratcliffe, C. I. Quadrupolar NMR to Investigate Dynamics in Solid Materials. In Encyclopedia of Magnetic Resonance; Harris, R. K., Wasylishen, R. E., Ed.; John Wiley & Sons, Ltd: Chichester, UK, 2012; pp 3814– 3829. DOI: 10.1002/9780470034590.emrstm1209 .There is no corresponding record for this reference.
- 69Moreau, F.; Kolokolov, D. I.; Stepanov, A. G.; Easun, T. L.; Dailly, A.; Lewis, W.; Blake, A. J.; Nowell, H.; Lennox, M. J.; Besley, E.; Yang, S.; Schröder, M. Tailoring Porosity and Rotational Dynamics in a Series of Octacarboxylate Metal-Organic Frameworks. Proc. Natl. Acad. Sci. U. S. A. 2017, 114 (12), 3056– 3061, DOI: 10.1073/pnas.161517211469https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjvF2htb8%253D&md5=0fe2e469dee33a4a805fad9646e48da0Tailoring porosity and rotational dynamics in a series of octacarboxylate metal-organic frameworksMoreau, Florian; Kolokolov, Daniil I.; Stepanov, Alexander G.; Easun, Timothy L.; Dailly, Anne; Lewis, William; Blake, Alexander J.; Nowell, Harriott; Lennox, Matthew J.; Besley, Elena; Yang, Sihai; Schroder, MartinProceedings of the National Academy of Sciences of the United States of America (2017), 114 (12), 3056-3061CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Modulation and precise control of porosity of metal-org. frameworks (MOFs) is of crit. importance to their materials function. Here the authors report modulation of porosity for a series of isoreticular octacarboxylate MOFs, denoted MFM-180 to MFM-185, via a strategy of selective elongation of metal-org. cages. The pseudomonomer of MFM-181 (2) can be presented as Cu4L1(H2O)4 (I). Owing to the high ligand connectivity, these MOFs do not show interpenetration, and are robust structures that have permanent porosity. Activated MFM-185a shows a high Brunauer-Emmett-Teller (BET) surface area of 4734 m2 g-1 for an octacarboxylate MOF. These MOFs show remarkable CH4 and CO2 adsorption properties, notably with simultaneously high gravimetric and volumetric deliverable CH4 capacities of 0.24 g g-1 and 163 vol/vol (298 K, 5-65 bar) recorded for MFM-<185≥a due to selective elongation of tubular cages. The dynamics of mol. rotors in deuterated MFM-180a-d16 and MFM-181a-d16 were studied by variable-temp. 2H solid-state NMR spectroscopy to reveal the reorientation mechanisms within these materials. Anal. of the flipping modes of the mobile Ph groups, their rotational rates, and transition temps. paves the way to controlling and understanding the role of mol. rotors through design of org. linkers within porous MOF materials.
- 70Haigis, V.; Coudert, F.-X.; Vuilleumier, R.; Boutin, A.; Fuchs, A. H. Hydrothermal Breakdown of Flexible Metal–Organic Frameworks: A Study by First-Principles Molecular Dynamics. J. Phys. Chem. Lett. 2015, 6 (21), 4365– 4370, DOI: 10.1021/acs.jpclett.5b0192670https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhs1Ogu7fM&md5=6573bcfba2cd5ccba6ce44c50cef7d97Hydrothermal Breakdown of Flexible Metal-Organic Frameworks: A Study by First-Principles Molecular DynamicsHaigis, Volker; Coudert, Francois-Xavier; Vuilleumier, Rodolphe; Boutin, Anne; Fuchs, Alain H.Journal of Physical Chemistry Letters (2015), 6 (21), 4365-4370CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Flexible metal-org. frameworks, also known as soft porous crystals, have been proposed for a vast no. of technol. applications, because they respond by large changes in structure and properties to small external stimuli, such as adsorption of guest mols. and changes in temp. or pressure. While this behavior is highly desirable in applications such as sensing and actuation, their extreme flexibility can also be synonymous with decreased stability. In particular, their performance in industrial environments is limited by a lack of stability at elevated temps. and in the presence of water. Here, we use first-principles mol. dynamics to study the hydrothermal breakdown of soft porous crystals. Focusing on the material MIL-53(Ga), we show that the weak point of the structure is the bond between the metal center and the org. linker and elucidate the mechanism by which water lowers the activation free energy for the breakdown. This allows us to propose strategies for the synthesis of MOFs with increased heat and water stability.
- 71Gaillac, R.; Pullumbi, P.; Beyer, K. A.; Chapman, K.; Keen, D. A.; Bennett, T. D.; Coudert, F.-X. Liquid Metal–Organic Frameworks. Nat. Mater. 2017, 16 (11), 1149– 1155, DOI: 10.1038/nmat499871https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1aisr3L&md5=fee166600501104fba7d0f4712e6a9e5Liquid metal-organic frameworksGaillac, Romain; Pullumbi, Pluton; Beyer, Kevin A.; Chapman, Karena W.; Keen, David A.; Bennett, Thomas D.; Coudert, Francois-XavierNature Materials (2017), 16 (11), 1149-1154CODEN: NMAACR; ISSN:1476-1122. (Nature Research)Metal-org. frameworks (MOFs) are a family of chem. diverse materials, with applications in a wide range of fields, covering engineering, physics, chem., biol. and medicine. Until recently, research has focused almost entirely on cryst. structures, yet now a clear trend is emerging, shifting the emphasis onto disordered states, including 'defective by design' crystals, as well as amorphous phases such as glasses and gels. Here the authors introduce a strongly assocd. MOF liq., obtained by melting a zeolitic imidazolate framework, ZIF-4 and ZIF-8. The authors combine in situ variable temp. x-ray, ex situ neutron pair distribution function expts., and first-principles mol. dynamics simulations to study the melting phenomenon and the nature of the liq. obtained. The authors demonstrate from structural, dynamical, and thermodynamical information that the chem. configuration, coordinative bonding, and porosity of the parent cryst. framework survive upon formation of the MOF liq.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.1c03630.
Experimental section, synthesis and characterization, computational details, supporting figures and discussion, rotation angle measurement pseudocode (PDF)
MD simulation of supercell NO2-MIL-53(Al) at 700 K (MPG)
Structure factors file of single-crystal XRD data of NO2-MIL-53(Al) (TXT)
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.