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Semiconductor Porous Hydrogen-Bonded Organic Frameworks Based on Tetrathiafulvalene Derivatives
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Journal of the American Chemical Society

Cite this: J. Am. Chem. Soc. 2022, 144, 20, 9074–9082
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https://doi.org/10.1021/jacs.2c01957
Published May 16, 2022

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Abstract

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Herein, we report on the use of tetrathiavulvalene-tetrabenzoic acid, H4TTFTB, to engender semiconductivity in porous hydrogen-bonded organic frameworks (HOFs). By tuning the synthetic conditions, three different polymorphs have been obtained, denoted MUV-20a, MUV-20b, and MUV-21, all of them presenting open structures (22, 15, and 27%, respectively) and suitable TTF stacking for efficient orbital overlap. Whereas MUV-21 collapses during the activation process, MUV-20a and MUV-20b offer high stability evacuation, with a CO2 sorption capacity of 1.91 and 1.71 mmol g–1, respectively, at 10 °C and 6 bar. Interestingly, both MUV-20a and MUV-20b present a zwitterionic character with a positively charged TTF core and a negatively charged carboxylate group. First-principles calculations predict the emergence of remarkable charge transport by means of a through-space hopping mechanism fostered by an efficient TTF π–π stacking and the spontaneous formation of persistent charge carriers in the form of radical TTF•+ units. Transport measurements confirm the efficient charge transport in zwitterionic MUV-20a and MUV-20b with no need for postsynthetic treatment (e.g., electrochemical oxidation or doping), demonstrating the semiconductor nature of these HOFs with record experimental conductivities of 6.07 × 10–7 (MUV-20a) and 1.35 × 10–6 S cm–1 (MUV-20b).

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Introduction

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The design of materials combining electrical conductivity and porosity is an interesting but challenging topic that has gained exponential attention in recent years for exploitation in next-generation applications. (1,2) Despite being usually considered insulating materials, metal–organic frameworks (MOFs) (3) and covalent organic frameworks (COFs) (4) are porous crystalline structures that have proven to be efficient for the transport of electrical charge with a suitable chemical design. (5−7) This has been achieved through organic linkers with an extended π-conjugation, (8,9) via the existence of a π–π stacking through-space pathway, (10−12) or with the incorporation of electroactive guest molecules within the pores of these crystalline materials. (13) Most relevant strategies to boost conductivity in porous materials rely on charge carrier formation, for example, through partial ligand oxidation upon iodine doping or partial metal-node oxidation/reduction in mixed-valence frameworks. (14) However, these approaches imply either a trade-off where porosity and available surface area are decreased or a very limited versatility to access mixed-valence states (e.g., Fe(II)/Fe(III)-based frameworks), respectively. Moreover, the implementation of MOFs/COFs in efficient devices is not trivial, (6) although different approaches have been successfully accomplished in this regard. (15−18)
Hydrogen-bonded organic frameworks, or HOFs, (19−21) have appeared as an alternative type of porous molecular-based crystalline materials that are self-assembled through H-bonding interactions. Similar to MOFs and COFs, HOFs have been used in gas storage, (22) separation, (23) encapsulation, (24) or proton conductivity, (25) among others. (26) However, due to the lack of formation of strong coordination bonds (as in MOFs) or covalent bonds (as in COFs), HOFs can be synthesized under mild conditions, (27) which facilitates their processing, one of the major drawbacks of MOFs and COFs. (16,20) Thus, the preparation of conductive HOFs appears as an intuitive solution for the problematic synthetic methods available for MOFs and COFs.
Tetrathiafulvalene (TTF) derivatives are a well-known family of molecular-based conductors extensively studied in the field of molecular electronics, (28,29) as well as for being used in the preparation of conductive MOFs (30) and COFs. (31) In these systems, in addition to a suitable orbital overlap, it is essential to obtain the radical cation TTF•+ to engender the charge carrier species. This usually implies the oxidation of the material, typically with I2 or Br2, which results in a decreased sorption capacity due to the incorporation of the reduced I3– or Br– species. (32)
Tetrathiafulvalene-tetrabenzoic acid, in short H4TTFTB, is a well-known ligand that has been used by us (33−37) and others (38,39) in the preparation of MOFs and COFs. This ligand has also been employed in the construction of a HOF with limited stability, which collapses upon desolvation, (40) and more recently, it has shown to be involved in single-crystal-to-single-crystal transformations. (41) A very recent development in TTF-based HOFs has been shown by Farha and co-workers, who have prepared a HOF with a naphthalene derivative of TTF, which, upon oxidation with I2, becomes a semiconductor (conductivity of 6.0 × 10–7 S cm–1). (42)
Herein, we present the use of the H4TTFTB molecule to prepare two new porous HOFs, in which the building block ligand has a zwitterionic character. These materials, denoted MUV-20a and MUV-20b, do not require additional doping for electrical charge transport, resulting in two porous conducting HOFs while preserving their crystalline porosity. The semiconducting properties of MUV-20a and MUV-20b stand record within the HOF materials and contrast with those exhibited by a non-zwitterionic HOF based on the same ligand, denoted MUV-21, which behaves as an insulator despite the suitable stacking of the TTF units. Zwitterionic polaron formation within an organic crystal therefore emerges as an new potential strategy to boost conductivity in porous materials.

Results and Discussion

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TTF-tetrabenzoic ether was prepared from the coupling of TTF and ethyl 4-bromobenzoate, followed by hydrolysis and acidification (see Section S1 in the Supporting Information). Importantly, acidification resulted in the protonation of three among the four carboxylate groups, resulting in an amorphous material of formula NaH3TTFTB, as seen with 1H NMR (see Figure S1) and energy-dispersive X-ray analysis (EDAX) (see Figure S2 and Table S1). Dissolution of NaH3TTFTB in THF and heating at 80 °C forms a transparent dark-red solution, and addition of diethyl ether causes the appearance of red needle-like crystals of MUV-20a after few minutes at room temperature (Figure 1). Upon washing the crystals with diethyl ether, the THF molecules are replaced by diethyl ether molecules, yielding crystals of MUV-20b (Figure 2). These crystals were suitable for single-crystal X-ray diffraction analysis (see Table S2 for crystallographic details). Quite differently, crystallization from DMF at 105 °C resulted in large single crystals of MUV-21 (Figure 3 and Table S2). Phase purity of each sample was confirmed by powder X-ray diffraction (Figures S28–S30).

Figure 1

Figure 1. (a) Crystal structure of MUV-20a showing the channels along the a-axis. (b) Microporous channel showing the hydrogen-bond interactions (in red) and the π–π stacking (in green) between benzene groups. (c) Distances between sulfur atoms of TTF units in adjacent layers. (d) Different layers showing the interpenetration along the a-axis. The THF molecules present in the pores have been omitted for clarity.

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Figure 2

Figure 2. (a) Crystal structure of MUV-20b showing the channels along the a-axis. (b) Microporous channel showing the hydrogen-bond interactions in red. (c) Distances between sulfur atoms of TTF units in adjacent layers. (d) Different layers showing the non-interpenetration of the structure along the a-axis. The ether molecules present in the pores have been omitted for clarity.

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Figure 3

Figure 3. (a) Crystal structure of MUV-21 showing the mesoporous channels along the a-axis. (b) Closer view of one microporous channel along the a axis. (c) Distances between sulfur atoms of TTF units in adjacent layers. (d) Different layers showing the non-interpenetrated framework along the a axis. The DMF molecules and DMA+ cations present in the pores have been omitted for clarity.

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MUV-20a forms a 2D hydrogen-bonded network involving three carboxylic acids from each molecule (Figure 1a), with O···O hydrogen-bond distances in the range of 2.60–2.73 Å (Figure S3), forming voids with dimensions of ca. 7 × 9 Å (Figure S4). The 2D layers are interconnected via π–π stacking between the benzene moieties possessing the carboxylate group that is not involved in hydrogen bonding (Figure 1b), with a distance of 3.28 Å between parallel benzene groups (Figure S5). As a result, interpenetration between adjacent layers occurs (blue and red in Figure 1d). The stacking of the layers results in a 3D-networked, rhombic, interpenetrated framework. The structural features of MUV-20a are completed with π–π stacking between the TTF moieties (Figures 1c, S6, and S7), with shortest S···S distances of 3.66 and 4.45 Å for closest and furthest neighbors, respectively (Tables S3 and S4).
Similarly, MUV-20b forms a 2D hydrogen-bonded network involving three carboxylic acids from each molecule (Figure 2a), with O···O hydrogen-bond distances in the range 2.63–2.67 Å (Figures 2b and S12), forming narrow voids with dimensions of ca. 9 × 9 Å (Figure S13). The stacking of the layers results in a 3D-networked, rhombic, non-interpenetrated framework (blue and red in Figure 2d). The structural features of MUV-20b are completed with π–π stacking between the TTF moieties (Figures 2c, S14, and S15), with shortest S···S distances of 3.64 and 4.45 Å for closest and furthest neighbors, respectively (Tables S5 and S6).
In contrast, structural analysis of MUV-21 (Figure 3) reveals that the three carboxylic acids and the carboxylate group are involved in hydrogen-bonding interactions, with O···O hydrogen bond distances in the range 2.46–2.58 Å (Figure S20). The crystalline structure is connected in a 2D framework with no interpenetration between adjacent layers (Figure 3d), forming large channels along the a axis (Figure 3a) of ca. 20 × 15 Å (Figures 3b and S21). The TTF moieties are closer on average than in MUV-20a and in MUV-20b, with shortest S···S distances of 3.77 and 3.80 Å (Figures 3c, S22, and S23, and Tables S7 and S8). In contrast to MUV-20a and MUV-20b, the structure of MUV-21 contains dimethylammonium cations (DMA+) originating from DMF decomposition.
The calculated free space of MUV-20a, MUV-20b, and MUV-21 is 22% (308 Å3 as void volume), 15% (250 Å3), and 27.6% (788.3 Å3), respectively (see Figures S9, S17, and S24). However, despite the apparent large porosity of MUV-21, this material collapses upon activation (Figure S38), probably caused by the stronger interactions of DMF molecules with the framework, as previously observed for analogous systems. (40) The crystallinity of MUV-20a and MUV-20b is maintained upon activation (1 h at 70 °C), remaining stable up to 330 °C (Figures S35–S37). CO2 adsorption isotherms reveal a maximum CO2 adsorption capacity, at 10 °C and 6 bar, of 1.91 and 1.71 mmol g–1 for MUV-20a and MUV-20b, respectively (see Figure 4 and Table S9). These values are comparable to other HOFs found in the literature, such as HOF-6 (43) and HOF-7, (44) although it is still far from the CO2 record uptake of 4.02 mmol g–1 of HOF-5 at 1 bar and 296 K. (22)

Figure 4

Figure 4. Gas adsorption isotherms of CO2 on MUV-20a (blue) and MUV-20b (red) at different temperatures. CO2 adsorption and desorption capacities are shown in closed and open circles, respectively.

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Comparing the two families of HOFs, MUV-21 has a higher void space and slightly shorter mean distances between TTF units than both MUV-20a and MUV-20b, which seems to indicate a better material for combining porosity and electrical conductivity, although, as already shown, the stability of MUV-21 upon activation is limited. However, close inspection of the structures reveals more relevant differences between the two families. Thus, whereas a DMA+ cation is present in MUV-21 to counterbalance the negative charge of the deprotonated carboxylate, no additional cation is present in MUV-20a or MUV-20b. EPR measurements actually evidence the presence of an unpaired electron in both MUV-20a and MUV-20b, which is neither present in the as-synthesized NaH3TTFTB nor in MUV-21 (Figure 5). The g values (g = 2.07) are in good agreement with an oxidized tetrathiafulvalene moiety. Thus, we hypothesize that compounds MUV-20a and MUV-20b can be considered as zwitterionic HOFs formed by molecules with a negative charge at one carboxylate unit and a positive charge at the TTF core. Unlike DMF, both THF and diethyl ether solvent molecules have a tendency to form peroxides, (45−47) which we believe is at the origin of TTF spontaneous oxidation.

Figure 5

Figure 5. EPR spectra of MUV-20a (blue), MUV-20b (red), MUV-21 (purple), and the NaH3TTFTB (black) ligand at room temperature.

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In order to confirm the zwitterionic-radical nature of MUV-20a and MUV-20b, compared to MUV-21, theoretical calculations were performed under the density functional theory (DFT) framework using periodic boundary conditions. The minimum-energy crystal structure of the three compounds was obtained upon full lattice and ionic relaxation at the PBEsol level starting from the experimental X-ray data (see Section S9 in the Supporting Information for computational details). The optimized lattice parameters of the HOFs compare well with the values inferred for the synthetized crystals (see Table S13). Importantly, the presence of DMA+ cations in MUV-21 leads to a H-bonding connection between the countercation and two TTFTB units (one of them with a deprotonated carboxylic acid; COO–), involving two diagonal carboxylic positions of the ligands, whereas a H-bond network connecting four TTFTBs is found for the other two diagonal positions (Figure S48). In contrast, the frameworks of MUV-20a and MUV-20b can grow without any need for countercations toward the formation of a HOF with singly deprotonated TTFTB ligands and overall charge neutrality. The most stable site for the deprotonated carboxylic acid of TTFTB was assessed by placing it at the four inequivalent acid groups of the unit cell of MUV-20a and MUV-20b and fully relaxing the resulting structure (Figure S49). Theoretical calculations predict the preferentially deprotonated carboxylic group as that showing short O(COO)···S(TTF) contacts in the range 2.7–3.1 Å for MUV-20a and MUV-20b (Figure S49). As experimental pieces of evidence indicate that the TTFTB ligand is singly deprotonated upon formation of the porous frameworks, the two ligands of the unit cell were considered to be singly deprotonated in their most stable isomer. (48) Moreover, as no countercation is present in the neutral crystal structure of MUV-20a and MUV20b, the negative charge of the carboxylate group has to be compensated by the formation of TTF•+ through spontaneous oxidation of the electron-donor moiety. We then propose two possible scenarios: (i) the extra electron of the carboxylate moves to the cationic TTF, leading to a carboxylic radical TTFTB species, or (ii) the ligand remains in its zwitterionic form engendering persistent charge carriers and a radical in the TTF core (Figure 6a). Preliminary calculations at the molecular level indicate that although both situations are computed very similar in energy, the zwitterionic species is more stable than the radical COO• analogue in singly deprotonated, neutral TTFTB when including boundary conditions (Figures S50 and S51).

Figure 6

Figure 6. (a) Schematic representation of deprotonated TTFTB as a carboxylic radical (left) and a zwitterion (right) in MUV-20a and MUV-20b. (b) VBM and CBM calculated for MUV-20a and MUV-21 with an isovalue contour of 0.05 atomic units (au). (c) Electronic band structure diagram (left) and density of states (right) calculated for the zwitterionic ferromagnetic MUV-20a at the HSE06 level. The Fermi level is set to the VBM. Spin-up α and spin-down β channels are displayed in blue and red, respectively. The band gaps of α (2.15 eV) and β (1.68 eV) channels are colored in blue and red, respectively. (d) Spin density of MUV-20a represented with an isovalue contour of 0.008 au. The charge accumulation increase (Δq) for the TTF core and the carboxylate group with respect to the reference isolated, fully protonated TTFTB ligand is indicated.

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MUV-20a and MUV-20b can be modeled in a ferromagnetic or an antiferromagnetic configuration by considering the interaction between neighboring radical TTFTB ligands (Figure S52). Theoretical calculations predict that the ferromagnetic alignment is 0.33 and 0.17 eV more stable in MUV-20a and MUV-20b, respectively, than the antiferromagnetic phase at the HSE06 level. In fact, the antiferromagnetic solution leads to the coupling of the unpaired electrons of the interacting TTFTB radicals, prompting a “diamagnetic”-like configuration (see Figures S53 and S54). As experimental data confirm the presence of the TTF radical, and following the theoretical relative stability calculations indicating that the ferromagnetic configuration is more stable, from now on, we focus on the ferromagnetic phase of both MUV-20a and MUV-20b.
Analysis of the electronic band structure and density of states (DOS) reveals a band gap of 1.42 eV in HOF MUV-21 (Figure S55), with a valence-band maximum (VBM) centered on the TTF unit and a conduction-band minimum (CBM) localized over the benzoic acid groups (Figure 6b). On the other hand, the band gap in MUV-20a and MUV-20b is predicted to be 1.68 and 1.52 eV, respectively, in the β-spin manifold (Figures 6c and S56, respectively). In this case, both the VBM(α) and CBM(β) are centered over the TTF moiety (Figures 6b, S57, and S58), suggesting the formation of the radical TTF•+. The spin density calculated for MUV-20a (Figure 6d) and MUV-20b (Figure S59) is fully located over the TTF core, which experiences a charge accumulation increase (Δq) of +0.58 and +0.55e, respectively, with respect to the isolated, fully protonated TTFTB ligand, whereas the deprotonated carboxylic group is predicted with a Δq of −0.70 and −0.66e, respectively. These results evidence the presence of an oxidized TTF core (with an unpaired electron; TTF•+) and a negatively charged carboxylate group (COO–) per TTFTB ligand, therefore confirming the zwitterionic nature of MUV-20a and MUV-20b (Figure 6a).
In our HOFs, the TTF units are assembled in a π-stacking arrangement along the a-axis; thus, charge conduction after carrier generation may arise anisotropically in one dimension. The electronic band structure calculated for our series of HOFs displays flat bands along the full k-path of the first Brillouin zone (Figures 6c, S53, and S56 for MUV-20a, MUV-20b, and MUV-21, respectively), which points toward a hopping regime as the dominant charge-transport mechanism. The size of the polaron was estimated from the spin density contours to localize over few (1–3) TTF units in the three HOFs (Figure S60), (49) supporting a hopping-like transport.
To shed light on the conducting properties of MUV-20a, MUV-20b, and MUV-21, the electronic couplings (J) between neighboring TTFTB ligands, the reorganization energy, and the resulting charge-transfer rate constants (k) were estimated by means of the Marcus theory and molecular calculations (see Section S9 in the Supporting Information for details). The energy splitting between the highest-occupied crystal orbitals involving the two TTFs of the unit cell (VBM energy splitting) (50) was evaluated as a bare approximation of the electronic communication between TTF pairs, showing a larger mean value for zwitterionic MUV-20a (175 meV) and MUV-20b (158 meV) than for MUV-21 (90 meV). Accurate electronic couplings for the closest interacting TTF pairs (dimer A in Figure 7) confirm this picture, with J values of 152, 92, and 55 meV for MUV-20a, MUV-20b, and MUV-21, respectively, which are in the same order of magnitude of those reported for prototypical organic semiconductors. (51,52) The coupling in the weakly interacting TTF pair (dimer B) is predicted one order of magnitude smaller (14, 37, and 7 meV for MUV-20a, MUV-20b, and MUV-21, respectively), which stems from the less efficient π-stacking of the TTF moieties (core-to-core intermolecular distances > 5 Å; Figure 7). Overall, considering the smaller electronic coupling as the limiting step for charge conduction, we predict rate constants of 8 × 1010, 6 × 1011, and 2 × 1010 s–1 for MUV-20a, MUV-20b, and MUV-21, respectively (Table S14). As conductivity depends on charge mobility and carrier concentration, zwitterionic MUV-20a and MUV-20b, which present larger TTFTB electronic couplings and already contain the TTF•+/COO– polaron in the framework, are expected to show a significant enhancement of charge transport compared to bare MUV-21.

Figure 7

Figure 7. TTFTB···TTFTB dimeric pairs in the π-stacking arrangement extracted from the minimum-energy crystal structure of MUV-20a (top), MUV-20b (middle), and MUV-21 (bottom). Relevant intermolecular distances and electronic couplings (J) between pairs are indicated.

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Transport measurements for MUV-20a, MUV-20b, and MUV-21 were performed using two-contact probe pressed-pellet devices measured at room temperature (300 K) (Figure S46), revealing conductivity values of 6.07 × 10–7, 1.35 × 10–6, and 6.23 × 10–9 S cm–1, respectively (see Table S11). This indicates that MUV-20a and MUV-20b behave as semiconductors, presenting electrical conductivities similar to those reported for Cd2(TTFTB) (53) and TTF-COF (39) after being oxidized with iodine and more than 10 times higher than iodine-doped HOF-110 (42) (see Table S12 for comparative values with all reported MOFs and HOFs containing the TTFTB unit). In contrast, non-zwitterionic MUV-21 behaves as an insulator due to the absence of charge carriers. Thus, conductivity measurements confirm the semiconducting nature of zwitterionic MUV-20a and MUV-20b, which present record charge transport in HOFs without the need for further oxidation due to the existence of persistent positive charge carriers in the form of TTF•+ radicals.
Due to the fast synthesis of the crystals under ambient conditions, the processability to prepare thin films of these porous semiconductor materials was examined for MUV-20a. Drop-casting of a 0.02 M THF solution of NaH3TTFTB on a 3 × 3 cm2 glass support yields a continuous thin film, as shown in Figure 8. This illustrates the facile processability of HOFs, contrary to what is commonly found for MOFs and COFs, which paves the way to their implementation in charge-storage devices, electrochemical sensors, or as electrocatalysts.

Figure 8

Figure 8. Preparation of a thin film of MUV-20a using drop casting.

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Conclusions

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A new strategy for the synthesis of conducting HOFs is presented, based on the in situ oxidation of a partially deprotonated TTF-based molecule, which yields a zwitterionic material. This has been exemplified with two different structures, namely, MUV-20a and MUV-20b, which are obtained using the TTFTB building block and have different solvents in the pores (THF and ether, respectively). On the contrary, the solvothermal approach in DMF commonly used for the preparation of porous materials yields a non-zwitterionic HOF, denoted MUV-21. Whereas MUV-21 collapses during pore activation, MUV-20a and MUV-20b display high stability upon evacuation, likely due to their zwitterionic behavior and lower pore sizes, and offer large CO2 sorption capacities up to 1.91 and 1.71 mmol g–1, respectively. Theoretical calculations confirm the zwitterionic nature of these two HOFs and the emergence of efficient charge transport properties without the need of postsynthetic oxidation treatments. Transport measurements indicate conductivity values of 6.07 × 10–7 and 1.35 × 10–6 S·cm–1 for MUV-20a and MUV-20b, respectively, thus placing these materials as the highest conducting HOFs so far, with the added value of facile synthesis for further application in organic electronics.

Experimental Section

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H4TTFTB was prepared as previously described, (38,54) and all details can be found in the Supporting Information.

Crystallization of MUV-20a

2 mL of tetrahydrofuran (THF) was added to 20 mg of NaH3TTFTB in a 40 mL vial. The mixture was sonicated for 2 min until a transparent dark-red solution was formed. This solution was heated for 5 min at 80 °C by placing the vial on top of a heating plate. Then, 30 mL of diethyl ether was added, resulting in red needle-like single crystals of MUV-20a, after few minutes at room temperature, in which THF molecules are embedded in the pores (Figure S11). Finally, the crystals were filtered in air (12 mg, yield 60%).

Crystallization of MUV-20b

Upon formation of red needle-like single crystals of MUV-20a, these were washed with diethyl ether, yielding red needle-like single crystals of MUV-20b (16 mg, yield 80%), in which THF molecules are replaced by diethyl ether molecules (Figure S19). In fact, immersion of crystals of MUV-20a in diethyl ether causes the transformation of MUV-20a to MUV-20b (see Figure S31 in the Supporting Information).

Crystallization of MUV-21

20 mg of NaH3TTFTB was solved with 1 mL of DMF in a 4 mL vial at 105 °C for 60 h in an oven with heating and cooling ramps of 0.5 °C min–1, resulting in red needle-like single crystals of MUV-21 that were washed with diethyl ether at room temperature (4 mg, yield: 20%).

Single-Crystal Diffraction

X-ray data for compound MUV-20a were collected at beamline I19 in a Diamond Light Source synchrotron at a temperature of 100 K using a Pilatus 6M detector. (55) X-ray data for the compound MUV-20b were collected at 100 K using a Rigaku FR-X rotating anode with a Hypix 6000HE detector. X-ray data for compound MUV-21 were collected at 120 K using a Rigaku microfocus Supernova with an Atlas CCD detector. Data were measured using GDA and CrysAlisPro suite of programs. X-ray data were processed and reduced using the CrysAlisPro suite of programs. Absorption correction was performed using empirical methods (SCALE3 ABSPACK) based upon symmetry-equivalent reflections combined with measurements at different azimuthal angles. The crystal structures were solved and refined against all F2 values using the SHELX and Olex 2 suite of programs. (56,57) All atoms were refined anisotropically with the exception of the partially occupied diethyl ether molecule in MUV-20b and a solvent DMF molecule in MUV-21. Hydrogen atoms were placed in the calculated positions. Details of each refinement can be found in the Supporting Information. CCDC 2153374–2153376 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: (+44)1223-336-033; or [email protected]).

Gas Sorption

MUV-20a and MUV-20b crystals were activated at 70 °C during 1 h. High-pressure adsorption isotherms of CO2 were measured at different temperatures from 10 to 55 °C in an IGA-100 gravimetric analyzer (Hiden Isochem) using approximately 35 mg of the different samples. The heat of adsorption was calculated according to the Clausius–Clapeyron equation from the isotherms measured at different temperatures (see Supporting Information Section S6).

Electron Paramagnetic Resonance

Electron paramagnetic resonance was measured using a Bruker ELEXYS E580 at 300 K.

Theoretical Calculations

Quantum chemical calculations were carried out within the DFT framework as implemented in the all-electron full-potential FHI-AIMS electronic structure package. Minimum-energy geometries for MUV-20a, MUV-20b, and MUV-21 were obtained starting from the experimental crystal structures, and after full lattice and ionic relaxation using the GGA-type PBEsol functional and the numeric atom-centered orbital tier-1 basis set. Dispersion forces were treated by means of the van der Waals Hirshfeld correction. The electronic band structure and density of states were obtained by means of the hybrid HSE06 functional. A full k-path in the P1̅ first Brillouin zone and a 3 × 3 × 3 k-grid were employed. The electronic couplings of the different TTF dimers were computed under the fragment-orbital DFT framework, as implemented in FHI-AIMS. See the Supporting Information for full computational details.

Conductivity Measurements

Powders of MUV-20a, MUV-20b, and MUV-21 were pressed to form pellets (P ≈ 5 US tons), cut in rectangular shapes, and allowed to make contact with platinum wires (Goodfellow, 99.99%, 25 μm of diameter) and silver conductive paint (RS 123-9911) in a two-probe configuration (Figure S46). Two different pellets were measured for each sample. The geometrical factors (width, length, and thickness) were measured using an optical microscope. MUV-21 was also measured using a single crystal (Figure S46).

Film Recrystallization

For the synthesis of the film, 40 mg of NaH3TTFTB was dissolved in 2 mL of THF and then was drop-cast on a 3 × 3 cm2 glass. After a few minutes, the solution was dried and a continuous film forming dark small crystals appeared on the surface of the support.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.2c01957.

  • General methods, materials, crystallographic data, computational details, and supporting theoretical data (PDF)

Accession Codes

CCDC 2153374–2153376 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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Author Information

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  • Corresponding Authors
  • Authors
    • María Vicent-Morales - Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, c/ Catedrático José Beltrán, 2, Paterna 46980, Spain
    • María Esteve-Rochina - Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, c/ Catedrático José Beltrán, 2, Paterna 46980, Spain
    • Enrique Ortí - Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, c/ Catedrático José Beltrán, 2, Paterna 46980, Spain;  Orcidhttps://orcid.org/0000-0001-9544-8286
    • Iñigo J. Vitórica-Yrezábal - School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
  • Author Contributions

    M.V.-M. and M.E.-R. contributed equally to this work.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work has been supported by the European Union (ERC-2016-CoG 724681-S-CAGE), Projects PID2020-117177GB-I00, PID2020-119748GA-I00, and Excellence Unit María de Maeztu CEX2019-000919-M granted to ICMol financed by MCIN/AEI/10.13039/501100011033/FEDER, UE, and the Generalitat Valenciana (PROMETEU/2019/066, PROMETEU/2020/077, and GV/2021/027). We acknowledge Diamond Light Source synchrotron for the time allocated (cy23480) and the members of beamline I19 for the help and support provided. We thank J. M. Martínez and G. Agustí for their help with EPR measurements and A. López and S. Mañas-Valero for their help with conductivity measurements.

References

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    The library of isostructural porous frameworks enables a systematic survey to optimize the structure and functionality of porous materials. In contrary to metal-org. frameworks (MOFs) and covalent org. frameworks (COFs), a handful of isostructural frameworks have been reported for hydrogen-bonded org. frameworks (HOFs) due to the weakness of the bonds. Herein, we provide a rule-of-thumb to develop isostructural HOFs, where we demonstrate the construction of the third and fourth generation of isostructural HAT-based HOFs (TolHAT-1 and ThiaHAT-1) by considering three important structural factors, that are (1) directional H-bonding, (2) shape-fitted docking of the HAT core, and (3) modulation of peripheral moieties. Their structural and photo-phys. properties including HCl vapor detection are presented. Moreover, TolHAT-1, ThiaHAT-1, and other isostructural HOFs (CPHAT-1 and CBPHAT-1) were thoroughly compared from the viewpoints of structures and properties. Importantly, mol. dynamics (MD) simulation proves to be rationally capable of evaluating the stability of isostructural HOFs. These results can accelerate the development of various isostructural mol. porous materials.
  20. 20
    Wang, B.; Lin, R.-B.; Zhang, Z.; Xiang, S.; Chen, B. Hydrogen-Bonded Organic Frameworks as a Tunable Platform for Functional Materials. J. Am. Chem. Soc. 2020, 142, 14399– 14416,  DOI: 10.1021/jacs.0c06473
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    Hydrogen-Bonded Organic Frameworks as a Tunable Platform for Functional Materials
    Wang, Bin; Lin, Rui-Biao; Zhang, Zhangjing; Xiang, Shengchang; Chen, Banglin
    Journal of the American Chemical Society (2020), 142 (34), 14399-14416CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A review. As a novel class of porous cryst. materials, hydrogen-bonded org. frameworks (HOFs), self-assembled from org. or metal-org. building blocks through intermol. hydrogen-bonding interactions, have attracted more and more attention. Over the past decade, a no. of porous HOFs have been constructed through judicious selection of H-bonding motifs, which are further enforced by other weak intermol. interactions such as π-π stacking and van der Waals forces and framework interpenetration. Since the H-bonds are weaker than coordinate and covalent bonds used for the construction of metal-org. frameworks (MOFs) and covalent org. frameworks (COFs), HOFs have some unique features such as mild synthesis condition, soln. processability, easy healing, and regeneration. These features enable HOFs to be a tunable platform for the construction of functional materials. Here, we review the H-bonding motifs used for constructing porous HOFs and highlight some of their applications, including gas sepn. and storage, chiral sepn. and structure detn., fluorescent sensing, heterogeneous catalysis, biol. applications, proton conduction, photoluminescent materials, and membrane-based applications.
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    Lin, R.-B.; He, Y.; Li, P.; Wang, H.; Zhou, W.; Chen, B. Multifunctional Porous Hydrogen-Bonded Organic Framework Materials. Chem. Soc. Rev. 2019, 48, 1362– 1389,  DOI: 10.1039/c8cs00155c
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    Multifunctional porous hydrogen-bonded organic framework materials
    Lin, Rui-Biao; He, Yabing; Li, Peng; Wang, Hailong; Zhou, Wei; Chen, Banglin
    Chemical Society Reviews (2019), 48 (5), 1362-1389CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. Hydrogen-bonded org. frameworks (HOFs) represent an interesting type of polymeric porous materials that can be self-assembled through H-bonding between org. linkers. To realize permanent porosity in HOFs, stable and robust open frameworks can be constructed by judicious selection of rigid mol. building blocks and hydrogen-bonded units with strong H-bonding interactions, in which the framework stability might be further enhanced through framework interpenetration and other types of weak intermol. interactions such as π···π interactions. Owing to the reversible and flexible nature of H-bonding connections, HOFs show high crystallinity, soln. processability, easy healing and purifn. These unique advantages enable HOFs to be used as a highly versatile platform for exploring multifunctional porous materials. Here, the bright potential of HOF materials as multifunctional materials is highlighted in some of the most important applications for gas storage and sepn., mol. recognition, elec. and optical materials, chem. sensing, catalysis, and biomedicine.
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    Wang, H.; Li, B.; Wu, H.; Hu, T.-L.; Yao, Z.; Zhou, W.; Xiang, S.; Chen, B. A Flexible Microporous Hydrogen-Bonded Organic Framework for Gas Sorption and Separation. J. Am. Chem. Soc. 2015, 137, 9963– 9970,  DOI: 10.1021/jacs.5b05644
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    A Flexible Microporous Hydrogen-Bonded Organic Framework for Gas Sorption and Separation
    Wang, Hailong; Li, Bin; Wu, Hui; Hu, Tong-Liang; Yao, Zizhu; Zhou, Wei; Xiang, Shengchang; Chen, Banglin
    Journal of the American Chemical Society (2015), 137 (31), 9963-9970CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A microporous three-dimensional hydrogen-bonded org. framework (HOF-5) has been constructed from a new org. linker 4,4',4'',4'''-tetra(2,4-diamino-1,3,5-triazin-6-yl)tetraphenylethene. Activated HOF-5a exhibits a stepwise N2 adsorption isotherm at 77 K, suggesting framework flexibility. The structure of activated HOF-5a has been established by powder X-ray diffraction studies, indicating a significant framework contraction from as-synthesized HOF-5 to activated HOF-5a of ∼21% by vol. HOF-5a shows moderately high porosity with a Brunauer-Emmett-Teller (BET) surface area of 1101 m2/g, and takes up a large amt. of acetylene and carbon dioxide under ambient conditions. Powder neutron diffraction studies and theor. calcns. reveal that suitable pore sizes, curvatures, and functional sites collectively enable HOF-5a to encapsulate a high d. of carbon dioxide mols. packed in a pseudo-one-dimensional array along the pore channel.
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    Li, P.; He, Y.; Arman, H. D.; Krishna, R.; Wang, H.; Weng, L.; Chen, B. A Microporous Six-Fold Interpenetrated Hydrogen-Bonded Organic Framework for Highly Selective Separation of C2H4/C2H6. Chem. Commun. 2014, 50, 13081– 13084,  DOI: 10.1039/c4cc05506c
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    A microporous six-fold interpenetrated hydrogen-bonded organic framework for highly selective separation of C2H4/C2H6
    Li, Peng; He, Yabing; Arman, Hadi D.; Krishna, Rajamani; Wang, Hailong; Weng, Linhong; Chen, Banglin
    Chemical Communications (Cambridge, United Kingdom) (2014), 50 (86), 13081-13084CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A unique 6-fold interpenetrated hydrogen-bonded org. framework (HOF) was developed, for the 1st time, for highly selective sepn. of C2H4/C2H6 at room temp. and normal pressure.
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    Liang, W.; Carraro, F.; Solomon, M. B.; Bell, S. G.; Amenitsch, H.; Sumby, C. J.; White, N. G.; Falcaro, P.; Doonan, C. J. Enzyme Encapsulation in a Porous Hydrogen-Bonded Organic Framework. J. Am. Chem. Soc. 2019, 141, 14298– 14305,  DOI: 10.1021/jacs.9b06589
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    Enzyme Encapsulation in a Porous Hydrogen-Bonded Organic Framework
    Liang, Weibin; Carraro, Francesco; Solomon, Marcello B.; Bell, Stephen G.; Amenitsch, Heinz; Sumby, Christopher J.; White, Nicholas G.; Falcaro, Paolo; Doonan, Christian J.
    Journal of the American Chemical Society (2019), 141 (36), 14298-14305CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Protection of biol. assemblies is crit. to applications in biotechnol., increasing the durability of enzymes in biocatalysis or potentially stabilizing biotherapeutics during transport and use. Here we show that a porous hydrogen-bonded org. framework (HOF) constructed from water-sol. tetra-amidinium (1·Cl4) and tetracarboxylate (2) building blocks can encapsulate and stabilize biomols. to elevated temp., proteolytic and denaturing agents, and extend the operable pH range for catalase activity. The HOF, which readily retains water within its framework structure, can also protect and retain the activity of enzymes such as alc. oxidase, that are inactive when encapsulated within zeolitic imidazolate framework (ZIF) materials. Such HOF coatings could provide valid alternative materials to ZIFs: they are metal free, possess larger pore apertures, and are stable over a wider, more biol. relevant pH range.
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    Sun, Z.-B.; Li, Y.-L.; Zhang, Z.-H.; Li, Z.-F.; Xiao, B.; Li, G. A Path to Improve Proton Conductivity: From a 3D Hydrogen-Bonded Organic Framework to a 3D Copper-Organic Framework. New J. Chem. 2019, 43, 10637– 10644,  DOI: 10.1039/c9nj02025j
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    A path to improve proton conductivity: from a 3D hydrogen-bonded organic framework to a 3D copper-organic framework
    Sun, Zhi-Bing; Li, Yi-Lin; Zhang, Zhe-Hua; Li, Zi-Feng; Xiao, Bo; Li, Gang
    New Journal of Chemistry (2019), 43 (26), 10637-10644CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)
    To conduct a comparative study on proton conductivities of a hydrogen-bonded org. framework (HOF) and its related metal-org. framework (MOF), a 3D HOF (HOF-H3L) (H3L = [3-(4-methyl-benzoyl)-thioureido]-acetic acid; CH3C6H4C(O)NHC(S)NHCH2COOH) and its related 3D copper MOF, {[CuI3CuII3L3(DMF)2(CH3OH)(H2O)]·3CH3OH}n (I) is selected and fabricated. Both HOF-H3L and MOF I exhibit high water stability. Their proton conductivities under different relative humidities (RHs) were fully investigated. Note that the MOF I exhibited the optimized cond. of 3.78 × 10-4 S cm-1 that was nearly one order of magnitude larger than that of HOF-H3L (6.91 × 10-5 S cm-1) at 100° and 98% RH. Based on the crystal data, Ea calcns., water vapor absorptions, and PXRD patterns, the proton-conducting mechanisms were suggested. This comparative investigation provides a new inspiration to researchers to design new proton-conductive materials in the future.
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    Zhou, H.; Ye, Q.; Wu, X.; Song, J.; Cho, C. M.; Zong, Y.; Tang, B. Z.; Hor, T. S. A.; Yeow, E. K. L.; Xu, J. A Thermally Stable and Reversible Microporous Hydrogen-Bonded Organic Framework: Aggregation Induced Emission and Metal Ion-Sensing Properties. J. Mater. Chem. C 2015, 3, 11874– 11880,  DOI: 10.1039/c5tc02790j
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    A thermally stable and reversible microporous hydrogen-bonded organic framework: aggregation induced emission and metal ion-sensing properties
    Zhou, Hui; Ye, Qun; Wu, Xiangyang; Song, Jing; Cho, Ching Mui; Zong, Yun; Tang, Ben Zhong; Hor, T. S. Andy; Yeow, Edwin Kok Lee; Xu, Jianwei
    Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2015), 3 (45), 11874-11880CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
    A microporous hydrogen-bonded org. framework (HOF) derived from a polyhedral oligomeric silsesquioxane (POSS) intermediate and an aggregation-induced emission (AIE) luminogen tetraphenylethene (TPE) deriv. has been synthesized and structurally characterized by various methods. This unique HOF exhibits a permanent porosity with a Brunauer-Emmett-Teller (BET) surface area of 101.9 m2 g-1. This HOF could be well dispersed in org. solvents in the form of nanoparticles with a size of a few hundred nanometers. These nanoparticles are highly fluorescent in org. soln., and exhibit a high fluorescence quenching selectivity towards copper ions. Furthermore, the fluorescence of this HOF could be recovered by the removal of copper ions upon addn. of cyanide and, more interestingly, this process could be repeated several times without considerably sacrificing the sensing activity towards copper ions.
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    Han, Y.-F.; Yuan, Y.-X.; Wang, H.-B. Porous Hydrogen-Bonded Organic Frameworks. Molecules 2017, 22, 266,  DOI: 10.3390/molecules22020266
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    Porous hydrogen-bonded organic frameworks
    Han, Yi-Fei; Yuan, Ying-Xue; Wang, Hong-Bo
    Molecules (2017), 22 (2), 266/1-266/34CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
    A review. Ordered porous solid-state architectures constructed via non-covalent supramol. self-assembly have attracted increasing interest due to their unique advantages and potential applications. Porous metal-coordination org. frameworks (MOFs) are generated by the assembly of metal coordination centers and org. linkers. Compared to MOFs, porous hydrogen-bonded org. frameworks (HOFs) are readily purified and recovered via simple recrystn. However, due to lacking of sufficiently ability to orientate self-aggregation of building motifs in predictable manners, rational design and prepn. of porous HOFs are still challenging. Herein, we summarize recent developments about porous HOFs and attempt to gain deeper insights into the design strategies of basic building motifs.
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    Jana, A.; Bähring, S.; Ishida, M.; Goeb, S.; Canevet, D.; Sallé, M.; Jeppesen, J. O.; Sessler, J. L. Functionalised Tetrathiafulvalene- (TTF-) Macrocycles: Recent Trends in Applied Supramolecular Chemistry. Chem. Soc. Rev. 2018, 47, 5614– 5645,  DOI: 10.1039/c8cs00035b
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    Functionalised tetrathiafulvalene- (TTF-) macrocycles: recent trends in applied supramolecular chemistry
    Jana, Atanu; Bahring, Steffen; Ishida, Masatoshi; Goeb, Sebastien; Canevet, David; Salle, Marc; Jeppesen, Jan O.; Sessler, Jonathan L.
    Chemical Society Reviews (2018), 47 (15), 5614-5645CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    Tetrathiafulvalene (TTF) has been extensively explored as a π-electron donor in supramol. systems. Over the last two decades substantial advances have been made in terms of constructing elaborate architectures based on TTF and in exploiting the resulting systems in the context of supramol. host-guest recognition. The inherent electron-donating character of TTF derivs. has led to their use in the construction of highly efficient optoelectronic materials, optical sensors, and electron-transfer ensembles. TTFs are also promising candidates for the development of the so-called "functional materials" that might see use in a range of modern technol. applications. Novel synthetic strategies, coupled with the versatility inherent within the TTF moiety, are now allowing the architecture of TTF-based systems to be tuned precisely and modified for use in specific purposes. In this crit. review, we provide a "state-of-the-art" overview of research involving TTF-based macrocyclic systems with a focus on their use in supramol. host-guest recognition, as components in non-covalent electron transfer systems, and in the construction of "mol. machines".
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    Otón, F.; Pfattner, R.; Oxtoby, N. S.; Mas-Torrent, M.; Wurst, K.; Fontrodona, X.; Olivier, Y.; Cornil, J.; Veciana, J.; Rovira, C. Benzodicarbomethoxytetrathiafulvalene Derivatives as Soluble Organic Semiconductors. J. Org. Chem. 2011, 76, 154– 163,  DOI: 10.1021/jo101817j
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    Benzodicarbomethoxytetrathiafulvalene Derivatives as Soluble Organic Semiconductors
    Oton, Francisco; Pfattner, Raphael; Oxtoby, Neil S.; Mas-Torrent, Marta; Wurst, Klaus; Fontrodona, Xavier; Olivier, Yoann; Cornil, Jerome; Veciana, Jaume; Rovira, Concepcio
    Journal of Organic Chemistry (2011), 76 (1), 154-163CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    A series of new tetrathiafulvalene (TTF) derivs. bearing dimethoxycarbonyl and Ph or phthalimidyl groups fused to the TTF core has been synthesized as potential sol. semiconductor materials for org. field-effect transistors (OFETs). The electron-withdrawing substituents lower the energy of the HOMO and LUMO levels and increase the soly. and stability of the semiconducting material. Crystal structures of all new TTF derivs. are also described, and theor. DFT calcns. were carried out to study the potential of the crystals to be used in OFET. In the exptl. study, the best performing device exhibited a hole mobility up to 7.5 × 10-3 cm2 V-1 s-1.
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    Ding, B.; Solomon, M. B.; Leong, C. F.; D’Alessandro, D. M. Redox-Active Ligands: Recent Advances towards Their Incorporation into Coordination Polymers and Metal-Organic Frameworks. Coord. Chem. Rev. 2021, 439, 213891,  DOI: 10.1016/j.ccr.2021.213891
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    Redox-active ligands: Recent advances towards their incorporation into coordination polymers and metal-organic frameworks
    Ding, Bowen; Solomon, Marcello B.; Leong, Chanel F.; D'Alessandro, Deanna M.
    Coordination Chemistry Reviews (2021), 439 (), 213891CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    Over the past three decades, the field of coordination polymers (CPs) and metal-org. frameworks (MOFs) has developed rapidly due to the potential applications of these materials in gas storage, sepns., catalysis and switching. Introducing redox properties into CPs and MOFs to electrochem. modulate their properties for the development of solid state electronic devices has been an interesting strategy applied in recent years. Notably, a challenge within this area is the engineering of framework materials with desired redox properties targeted at a specific function. This review explores some of the key redox-active ligands that have been investigated within the previous eight years as redox-active components of solid state materials and examines a no. of key strategies for their integration into CPs and MOFs. This review further highlights emergent redox-active ligands in the literature, which take inspiration from the rich field of org. electronics. While these ligands remain largely unexplored in the field of MOFs and CPs, they offer new opportunities for the improvement of solar cells, light induced photo switches, efficient photoelectrocatalysts and long range, rapid charge transfer in MOF materials.
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    Jin, S.; Sakurai, T.; Kowalczyk, T.; Dalapati, S.; Xu, F.; Wei, H.; Chen, X.; Gao, J.; Seki, S.; Irle, S.; Jiang, D. Two-Dimensional Tetrathiafulvalene Covalent Organic Frameworks: Towards Latticed Conductive Organic Salts. Chem.─Eur. J. 2014, 20, 14608– 14613,  DOI: 10.1002/chem.201402844
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    Two-Dimensional Tetrathiafulvalene Covalent Organic Frameworks: Towards Latticed Conductive Organic Salts
    Jin, Shangbin; Sakurai, Tsuneaki; Kowalczyk, Tim; Dalapati, Sasanka; Xu, Fei; Wei, Hao; Chen, Xiong; Gao, Jia; Seki, Shu; Irle, Stephan; Jiang, Donglin
    Chemistry - A European Journal (2014), 20 (45), 14608-14613CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The construction of a new class of covalent TTF lattice by integrating TTF units into two-dimensional covalent org. frameworks (2-dimensional COFs) is reported. The authors explored a general strategy based on the C2+C2 topol. diagram and applied to the synthesis of microporous and mesoporous TTF COFs. Structural resolns. revealed that both COFs consist of layered lattices with periodic TTF columns and tetragonal open nanochannels. The TTF columns offer predesigned pathways for high-rate hole transport, predominate the HOMO and LUMO levels of the COFs, and are redox active to form org. salts that exhibit enhanced elec. cond. by several orders of magnitude. However, the linkers between the TTF units play a vital role in detg. the carrier mobility and cond. through the perturbation of 2-dimensional sheet conformation and interlayer distance. These results open a way towards designing a new type of TTF materials with stable and predesignable lattice structures for functional exploration.
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    Su, J.; Yuan, S.; Wang, H.-Y.; Huang, L.; Ge, J.-Y.; Joseph, E.; Qin, J.; Cagin, T.; Zuo, J.-L.; Zhou, H.-C. Redox-Switchable Breathing Behavior in Tetrathiafulvalene-Based Metal-Organic Frameworks. Nat. Commun. 2017, 8, 2008,  DOI: 10.1038/s41467-017-02256-y
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    Redox-switchable breathing behavior in tetrathiafulvalene-based metal-organic frameworks
    Su Jian; Wang Hai-Ying; Ge Jing-Yuan; Zuo Jing-Lin; Yuan Shuai; Joseph Elizabeth; Qin Junsheng; Cagin Tahir; Zhou Hong-Cai; Huang Lan; Zhou Hong-Cai; Cagin Tahir
    Nature communications (2017), 8 (1), 2008 ISSN:.
    Metal-organic frameworks (MOFs) that respond to external stimuli such as guest molecules, temperature, or redox conditions are highly desirable. Herein, we coupled redox-switchable properties with breathing behavior induced by guest molecules in a single framework. Guided by topology, two flexible isomeric MOFs, compounds 1 and 2, with a formula of In(Me2NH2)(TTFTB), were constructed via a combination of [In(COO)4](-) metal nodes and tetratopic tetrathiafulvalene-based linkers (TTFTB). The two compounds show different breathing behaviors upon the introduction of N2. Single-crystal X-ray diffraction, accompanied by molecular simulations, reveals that the breathing mechanism of 1 involves the bending of metal-ligand bonds and the sliding of interpenetrated frameworks, while 2 undergoes simple distortion of linkers. Reversible oxidation and reduction of TTF moieties changes the linker flexibility, which in turn switches the breathing behavior of 2. The redox-switchable breathing behavior can potentially be applied to the design of stimuli-responsive MOFs.
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    Castells-Gil, J.; Mañas-Valero, S.; Vitórica-Yrezábal, I. J.; Ananias, D.; Rocha, J.; Santiago, R.; Bromley, S. T.; Baldoví, J. J.; Coronado, E.; Souto, M.; Mínguez Espallargas, G. Electronic, Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal–Organic Frameworks. Chem.─Eur. J. 2019, 25, 12636– 12643
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    Electronic, Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal-Organic Frameworks
    Castells-Gil, Javier; Manas-Valero, Samuel; Vitorica-Yrezabal, Inigo J.; Ananias, Duarte; Rocha, Joao; Santiago, Raul; Bromley, Stefan T.; Baldovi, Jose J.; Coronado, Eugenio; Souto, Manuel; Minguez Espallargas, Guillermo
    Chemistry - A European Journal (2019), 25 (54), 12636-12643CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Tetrathiafulvalene-lanthanide (TTF-Ln) metal-org. frameworks (MOFs) are an interesting class of multifunctional materials in which porosity can be combined with electronic properties such as elec. cond., redox activity, luminescence and magnetism. Herein a new family of isostructural TTF-Ln MOFs is reported, denoted as MUV-5(Ln) (Ln = Gd, Tb, Dy, Ho, Er), exhibiting semiconducting properties as a consequence of the short intermol. S···S contacts established along the chain direction between partially oxidized TTF moieties. This family shows photoluminescence properties and single-mol. magnetic behavior, finding near-IR (NIR) photoluminescence in the Yb/Er deriv. and slow relaxation of the magnetization in the Dy and Er derivs. As such properties are dependent on the electronic structure of the lanthanide ion, the immense structural, electronic and functional versatility of this class of materials is emphasized.
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    Souto, M.; Romero, J.; Calbo, J.; Vitórica-Yrezábal, I. J.; Zafra, J. L.; Casado, J.; Ortí, E.; Walsh, A.; Mínguez Espallargas, G. Breathing-Dependent Redox Activity in a Tetrathiafulvalene-Based Metal-Organic Framework. J. Am. Chem. Soc. 2018, 140, 10562– 10569,  DOI: 10.1021/jacs.8b05890
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    Breathing-Dependent Redox Activity in a Tetrathiafulvalene-Based Metal-Organic Framework
    Souto, Manuel; Romero, Jorge; Calbo, Joaquin; Vitorica-Yrezabal, Inigo J.; Zafra, Jose L.; Casado, Juan; Orti, Enrique; Walsh, Aron; Minguez Espallargas, Guillermo
    Journal of the American Chemical Society (2018), 140 (33), 10562-10569CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    "Breathing" metal-org. frameworks (MOFs) that involve changes in their structural and phys. properties upon an external stimulus are an interesting class of cryst. materials due to their range of potential applications including chem. sensors. The addn. of redox activity opens up a new pathway for multifunctional "breathing" frameworks. Herein, we report the continuous breathing behavior of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, showing a reversible swelling (up to ca. 40% of the vol. cell) upon solvent adsorption. Importantly, the planarity of the TTF linkers is influenced by the breathing behavior of the MOF, directly impacting on its electrochem. properties and thus opening the way for the development of new electrochem. sensors. Quantum chem. calcns. and Raman spectroscopy have been used to provide insights into the tunability of the oxidn. potential.
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    Souto, M.; Calbo, J.; Mañas-Valero, S.; Walsh, A.; Mínguez Espallargas, G. Charge-Transfer Interactions between Fullerenes and a Mesoporous Tetrathiafulvalene-Based Metal-Organic Framework. Beilstein J. Nanotechnol. 2019, 10, 1883– 1893,  DOI: 10.3762/bjnano.10.183
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    Charge-transfer interactions between fullerenes and a mesoporous tetrathiafulvalene-based metal-organic framework
    Souto, Manuel; Calbo, Joaquin; Manas-Valero, Samuel; Walsh, Aron; Espallargas, Guillermo Minguez
    Beilstein Journal of Nanotechnology (2019), 10 (), 1883-1893CODEN: BJNEAH; ISSN:2190-4286. (Beilstein-Institut zur Foerderung der Chemischen Wissenschaften)
    The design of metal-org. frameworks (MOFs) incorporating electroactive guest mols. in the pores has become a subject of great interest in order to obtain addnl. elec. functionalities within the framework while maintaining porosity. Understanding the charge-transfer (CT) process between the framework and the guest mols. is a crucial step towards the design of new electroactive MOFs. Herein, we present the encapsulation of fullerenes (C60) in a mesoporous tetrathiafulvalene (TTF)-based MOF. The CT process between the electron-acceptor C60 guest and the electron-donor TTF ligand is studied in detail by means of different spectroscopic techniques and d. functional theory (DFT) calcns. Importantly, gas sorption measurements demonstrate that sorption capacity is maintained after encapsulation of fullerenes, whereas the elec. cond. is increased by two orders of magnitude due to the CT interactions between C60 and the TTF-based framework.
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    Souto, M.; Santiago-Portillo, A.; Palomino, M.; Vitórica-Yrezábal, I. J.; Vieira, B. J. C.; Waerenborgh, J. C.; Valencia, S.; Navalón, S.; Rey, F.; García, H.; Mínguez Espallargas, G. A Highly Stable and Hierarchical Tetrathiafulvalene-Based Metal-Organic Framework with Improved Performance as a Solid Catalyst. Chem. Sci. 2018, 9, 2413– 2418,  DOI: 10.1039/c7sc04829g
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    A highly stable and hierarchical tetrathiafulvalene-based metal-organic framework with improved performance as a solid catalyst
    Souto, Manuel; Santiago-Portillo, Andrea; Palomino, Miguel; Vitorica-Yrezabal, Inigo J.; Vieira, Bruno J. C.; Waerenborgh, Joao C.; Valencia, Susana; Navalon, Sergio; Rey, Fernando; Garcia, Hermenegildo; Minguez Espallargas, Guillermo
    Chemical Science (2018), 9 (9), 2413-2418CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    Herein we report the synthesis of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, which shows a non-interpenetrated hierarchical crystal structure with mesoporous one-dimensional channels of ca. 3 nm and orthogonal microporous channels of ca. 1 nm. This highly stable MOF (aq. soln. with pH values ranging from 2 to 11 and different org. solvents), which possesses the well-known [Fe3(μ3-O)(COO)6] secondary building unit, has proven to be an efficient catalyst for the aerobic oxidn. of dibenzothiophenes.
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    Vicent-Morales, M.; Vitórica-Yrezábal, I. J.; Souto, M.; Mínguez Espallargas, G. Influence of Interpenetration on the Flexibility of MUV-2. CrystEngComm 2019, 21, 3031– 3035,  DOI: 10.1039/c9ce00233b
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    Influence of interpenetration on the flexibility of MUV-2
    Vicent-Morales, Maria; Vitorica-Yrezabal, Inigo J.; Souto, Manuel; Minguez Espallargas, Guillermo
    CrystEngComm (2019), 21 (19), 3031-3035CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
    The crystal structure of an interpenetrated tetrathiafulvalene (TTF)-based metal-org. framework (MOF) is reported. This MOF, denoted as MUV-2-i, is the interpenetrated analog of the hierarchical and flexible MUV-2. Interestingly, the large flexibility exhibited by MUV-2 upon polar solvent adsorption is considerably reduced in the interpenetrated form which can be explained by short S···S interactions between adjacent TTF-based ligands ensuring more rigidity in the framework. In addn., the porosity of MUV-2-i is significantly decreased in comparison to that of MUV-2 as shown by the reduced free vol. in the crystal structure.
  38. 38
    Narayan, T. C.; Miyakai, T.; Seki, S.; Dincă, M. High Charge Mobility in a Tetrathiafulvalene-Based Microporous Metal-Organic Framework. J. Am. Chem. Soc. 2012, 134, 12932– 12935,  DOI: 10.1021/ja3059827
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    High Charge Mobility in a Tetrathiafulvalene-Based Microporous Metal-Organic Framework
    Narayan, Tarun C.; Miyakai, Tomoyo; Seki, Shu; Dinca, Mircea
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    The tetratopic ligand tetrathiafulvalene-tetrabenzoate (H4TTFTB) was used to synthesize Zn2(TTFTB), a new metal-org. framework that contains columnar stacks of tetrathiafulvalene and benzoate-lined infinite 1-dimensional channels. The new MOF remains porous upon desolvation and exhibits charge mobility commensurate with some of the best org. semiconductors, confirmed by flash-photolysis-time-resolved microwave cond. measurements. Zn2(TTFTB) represents the 1st example of a permanently porous MOF with high charge mobility and may inspire further exploration of the electronic properties of these materials.
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    Ding, H.; Li, Y.; Hu, H.; Sun, Y.; Wang, J.; Wang, C.; Wang, C.; Zhang, G.; Wang, B.; Xu, W.; Zhang, D. A Tetrathiafulvalene-Based Electroactive Covalent Organic Framework. Chem.─Eur. J. 2014, 20, 14614– 14618,  DOI: 10.1002/chem.201405330
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    A Tetrathiafulvalene-Based Electroactive Covalent Organic Framework
    Ding, Huimin; Li, Yonghai; Hu, Hui; Sun, Yimeng; Wang, Jianguo; Wang, Caixing; Wang, Cheng; Zhang, Guanxin; Wang, Baoshan; Xu, Wei; Zhang, Deqing
    Chemistry - A European Journal (2014), 20 (45), 14614-14618CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Two-dimensional covalent org. frameworks (2-dimensional COFs) provide a unique platform for the mol. design of electronic and optoelectronic materials. Here, the synthesis and characterization of an electroactive COF contg. the known tetrathiafulvalene (TTF) unit is reported. The TTF-COF crystallizes into 2-dimensional sheets with an eclipsed AA stacking motif, and shows high thermal stability and permanent porosity. The presence of TTF units endows the TTF-COF with electron-donating ability, which is characterized by cyclic voltammetry. The open frameworks of TTF-COF are amenable to doping with electron acceptors (e.g., iodine), and the cond. of TTF-COF bulk samples can be improved by doping. The results open up a reliable route for the prepn. of well-ordered conjugated TTF polymers, which hold great potential for applications in fields from mol. electronics to energy storage.
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    Hisaki, I.; Emilya Affendy, N. Q.; Tohnai, N. Precise Elucidations of Stacking Manners of Hydrogen-Bonded Two-Dimensional Organic Frameworks Composed of X-Shaped π-Conjugated Systems. CrystEngComm 2017, 19, 4892– 4898,  DOI: 10.1039/c7ce00183e
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    Precise elucidations of stacking manners of hydrogen-bonded two-dimensional organic frameworks composed of X-shaped π-conjugated systems
    Hisaki, Ichiro; Emilya Affendy, N. Q.; Tohnai, Norimitsu
    CrystEngComm (2017), 19 (33), 4892-4898CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
    Two-dimensional covalent org. frameworks (2D-COFs) composed of π-conjugated components are promising functional materials. In general, however, 2D-COFs exhibit low crystallinity, preventing their precise structural characterization. On the other hand, non-covalent org. frameworks (nCOFs) are often obtained as single crystals due to highly reversible bond formation, and therefore, are possible to complement the structural evaluation of 2D-COFs. In this study, three X-shaped tetracarboxylic acid derivs. with benzene, tetrathiafulvalene (TTF), and pyrazinoquinoxaline cores (X-Ph, X-TTF and X-PyQ, resp.) were revealed to form isostructural, hydrogen-bonded rhombic network (RhomNet) sheets, which subsequently stacked without interpenetration to give low d. frameworks with one-dimensional (1D) inclusion channels. RhomNet structures and their stacking manners were fully revealed based on single crystal X-ray anal. Consequently, we revealed that the RhomNet sheets of X-Ph, X-TTF and X-PyQ stack in different ways depending on the conformation of the peripheral phenylene groups, mol. symmetry and interlayer interactions, in spite of the same network topol. in the RhomNet sheets. The precise characterization of the present RhomNet crystals can provide a new structural insight into porous 2D-COFs.
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    Gao, X.-Y.; Li, Y.-L.; Liu, T.-F.; Huang, X.-S.; Cao, R. Single-Crystal-to-Single-Crystal Transformation of Tetrathiafulvalene-Based Hydrogen-Bonded Organic Frameworks. CrystEngComm 2021, 23, 4743– 4747,  DOI: 10.1039/d1ce00519g
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    Single-crystal-to-single-crystal transformation of tetrathiafulvalene-based hydrogen-bonded organic frameworks
    Gao, Xiang-Yu; Li, Yu-Lin; Liu, Tian-Fu; Huang, Xin-Song; Cao, Rong
    CrystEngComm (2021), 23 (27), 4743-4747CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
    The design and synthesis of a hydrogen-bonded org. framework (HOF) based on tetrathiafulvalene tetracarboxylic acid is reported. The resultant HOF can undergo single-crystal-to-single-crystal transformation to form another two isomers. The structural characteristics and the redox properties of the HOFs were conveniently tailored utilizing the transformation of the phases.
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    Kirlikovali, K. O.; Goswami, S.; Mian, M. R.; Krzyaniak, M. D.; Wasielewski, M. R.; Hupp, J. T.; Li, P.; Farha, O. K. An Electrically Conductive Tetrathiafulvalene-Based Hydrogen-Bonded Organic Framework. ACS Mater. Lett. 2022, 4, 128– 135,  DOI: 10.1021/acsmaterialslett.1c00628
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    An Electrically Conductive Tetrathiafulvalene-Based Hydrogen-Bonded Organic Framework
    Kirlikovali, Kent O.; Goswami, Subhadip; Mian, Mohammad Rasel; Krzyaniak, Matthew D.; Wasielewski, Michael R.; Hupp, Joseph T.; Li, Peng; Farha, Omar K.
    ACS Materials Letters (2022), 4 (1), 128-135CODEN: AMLCEF; ISSN:2639-4979. (American Chemical Society)
    Recent advancements in the development of conductive metal-org. frameworks (MOFs) and covalent org. frameworks (COFs) have sparked interest in a variety of applications that leverage electronic materials due to the inherent tunability, porosity, and crystallinity assocd. with these materials. Hydrogen-bonded org. frameworks (HOFs) comprise an emerging class of complementary porous materials that assemble cryst. networks mainly from intermol. hydrogen-bonding interactions; however, relatively few reports on functional HOFs exist as these reversible interactions are much weaker than the coordination or covalent bonds found in the former frameworks, which presents addnl. challenges in the isolation and activation of HOFs. In this work, we introduce an approach to access a permanently porous HOF derived from a tetrathiafulvalene (TTF) core, which is the first HOF reported to date that exhibits elec. cond. Upon pptn. from soln., HOF-110 self-assembles in a preferred orientation that contains vertical columns of TTF dimers, and the postsynthetic incorporation of iodine within the nanoporous channels of this framework affords pressed pellet cond. values of up to 6.0 x 10-7 S·cm-1, which is an almost 30-fold improvement compared with pressed pellets of the pristine framework. Extensive structural characterization studies suggest the presence of radical mixed-valence TTF/TTF·+ species within these materials, which is consistent with previous reports on analogous TTF-based MOFs and COFs. Overall, this work presents a viable strategy to develop robust, elec. conductive frameworks built from purely intermol. interactions, further expanding the toolbox available for the assembly of functional porous materials.
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    Yang, W.; Yang, F.; Hu, T.-L.; King, S. C.; Wang, H.; Wu, H.; Zhou, W.; Li, J.-R.; Arman, H. D.; Chen, B. Microporous Diaminotriazine-Decorated Porphyrin-Based Hydrogen-Bonded Organic Framework: Permanent Porosity and Proton Conduction. Cryst. Growth Des. 2016, 16, 5831– 5835,  DOI: 10.1021/acs.cgd.6b00924
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    Microporous Diaminotriazine-Decorated Porphyrin-Based Hydrogen-Bonded Organic Framework: Permanent Porosity and Proton Conduction
    Yang, Wei; Yang, Fan; Hu, Tong-Liang; King, Stephen Charles; Wang, Hailong; Wu, Hui; Zhou, Wei; Li, Jian-Rong; Arman, Hadi D.; Chen, Banglin
    Crystal Growth & Design (2016), 16 (10), 5831-5835CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    A diaminotriazine-decorated porphyrin-based microporous hydrogen-bonded org. framework has been successfully prepd. and characterized using single crystal X-ray diffraction anal. Its activated phase exhibits permanent porosity, gas sepn., and proton cond. under humid conditions.
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    Yang, W.; Li, B.; Wang, H.; Alduhaish, O.; Alfooty, K.; Zayed, M. A.; Li, P.; Arman, H. D.; Chen, B. A Microporous Porphyrin-Based Hydrogen-Bonded Organic Framework for Gas Separation. Cryst. Growth Des. 2015, 15, 2000– 2004,  DOI: 10.1021/acs.cgd.5b00147
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    A Microporous Porphyrin-Based Hydrogen-Bonded Organic Framework for Gas Separation
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    Crystal Growth & Design (2015), 15 (4), 2000-2004CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    A hydrogen-bonded org. framework (HOF), HOF-7 (1), based on a zinc porphyrin-based building block (ZnTDPP, 2) with diaminotriazine moieties has been successfully constructed and structurally characterized (ZnTDPP = 5,10,15,20-tetrakis(4-(2,4-diaminotriazinyl)phenyl)porphyrinato zinc). Single-crystal X-ray diffraction anal. reveals that HOF-7 is built by the 2D layered subunits connected by the intermol. hydrogen-bonding and π-π interaction, exhibiting two kinds of micropores with sizes of 3.2 x 4.7 A2 and 4.2 X 6.7 A2, resp. This HOF exhibits permanent porosities as demonstrated in the CO2 sorption and selective adsorption of CO2 over N2.
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    In the interest of lab. safety, a study was carried out to det. which chem. structures are potential peroxide formers and hence hazardous. Three lists are presented depending upon the length of time the compds. are safe and the type of reaction that produces the peroxide. These lists are informative and not exhaustive. These compds. form concd. peroxides or else peroxide-initiated polymn. The handling procedures for these compds. are given, as well as labeling instructions. The methods of detection and removal of peroxides are given.
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    A review with 29 refs. concerning safety guidelines for hazards and safe handling of peroxidizable org. chems. Topics discussed include: peroxidn. chem.; classes of peroxide formers; hazardous levels of peroxides; inhibitors; control of peroxidizable org. chems. (purchasing and storage, surveillance, use); peroxidizable detection methods (ferrous thiocyanate method, iodide tests, dip strips, titanium sulfate); and removal of peroxides.
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  48. 48

    Note that partial protonation (50% fully protonated TTFTBs in the unit cell) in MUV-20a and MUV-20b leads to a significant change in the electronic band structure of the HOF, with a predicted band gap in the β-channel of 0.51 and 0.52 eV, respectively (see Figures S56–S59).

    There is no corresponding record for this reference.
  49. 49

    Note that there is no TTF•+ polaron in the bare MUV-21; hence, chemical or electrochemical oxidation processes need to be considered for hole-carrier generation in this material.

    There is no corresponding record for this reference.
  50. 50

    The VBM splitting was estimated as the energy difference between the VBM and the VBM-1 divided by 2.

    There is no corresponding record for this reference.
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    Zeiser, C.; Moretti, L.; Geiger, T.; Kalix, L.; Valencia, A. M.; Maiuri, M.; Cocchi, C.; Bettinger, H. F.; Cerullo, G.; Broch, K. Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene. J. Phys. Chem. Lett. 2021, 12, 7453– 7458,  DOI: 10.1021/acs.jpclett.1c01805
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    Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene
    Zeiser, Clemens; Moretti, Luca; Geiger, Thomas; Kalix, Lukas; Valencia, Ana M.; Maiuri, Margherita; Cocchi, Caterina; Bettinger, Holger F.; Cerullo, Giulio; Broch, Katharina
    Journal of Physical Chemistry Letters (2021), 12 (31), 7453-7458CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Singlet fission (SF), the photophys. process in which 1 singlet exciton is transformed into 2 triplets, depends inter alia on the coupling of electronic states. Here, the authors use fluorination and the resulting changes in partial charge distribution across the chromophore backbone as a particularly powerful tool to control this parameter in pentacene. The introduction of a permanent dipole moment leads to an enhanced coupling of Frenkel exciton and charge transfer states and to an increased SF rate which the authors probed using ultrafast transient absorption spectroscopy. These findings are contrasted with H-aggregate formation and a significantly reduced triplet-pair state lifetime in a fluorinated pentacene for which the different partial charge distribution leads to a negligible dipole moment.
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    Troisi, Alessandro
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    A review. The theories developed since the fifties to describe charge transport in mol. crystals proved to be inadequate for the most promising classes of high mobility mol. semiconductors identified in the recent years, including for example pentacene and rubrene. After reviewing at an elementary level the classical theories, which still provide the language for the understanding of charge transport in these systems, this tutorial review outlines the recent exptl. and computational evidence that prompted the development of new theories of charge transport in mol. crystals. A crit. discussion will illustrate how very rarely it is possible to assume a charge hopping mechanism for high mobility org. crystals at any temp. Recent models based on the effect of non-local electron-phonon coupling, dynamic disorder, coexistence of localized and delocalized states are reviewed. Addnl., a few more recent avenues of theor. investigation, including the study of defect states, are discussed.
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    Sun, L.; Park, S. S.; Sheberla, D.; Dincă, M. Measuring and Reporting Electrical Conductivity in Metal-Organic Frameworks: Cd2(TTFTB) as a Case Study. J. Am. Chem. Soc. 2016, 138, 14772– 14782,  DOI: 10.1021/jacs.6b09345
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    Measuring and Reporting Electrical Conductivity in Metal-Organic Frameworks: Cd2(TTFTB) as a Case Study
    Sun, Lei; Park, Sarah S.; Sheberla, Dennis; Dinca, Mircea
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    Elec. conductive metal-org. frameworks (MOFs) are emerging as a subclass of porous materials that can have a transformative effect on electronic and renewable energy devices. Systematic advances in these materials depend critically on the accurate and reproducible characterization of their elec. properties. This is made difficult by the numerous techniques available for elec. measurements and the dependence of metrics on device architecture and numerous external variables. These challenges, common to all types of electronic materials and devices, are esp. acute for porous materials, whose high surface area make them even more susceptible to interactions with contaminants in the environment. Here, we use the anisotropic semiconducting framework Cd2(TTFTB) (TTFTB4- = tetrathiafulvalene tetrabenzoate) to benchmark several common methods available for measuring elec. properties in MOFs. We show that factors such as temp., chem. environment (atm.), and illumination conditions affect the quality of the data obtained from these techniques. Consistent results emerge only when these factors are strictly controlled and the morphol. and anisotropy of the Cd2(TTFTB) single-crystal devices are taken into account. Most importantly, we show that depending on the technique, device construction, and/or the environment, a variance of 1 or even 2 orders of magnitude is not uncommon for even just one material if external factors are not controlled consistently. Differences in cond. values of even 2 orders of magnitude should therefore be interpreted with caution, esp. between different research groups comparing different compds. These results allow us to propose a reliable protocol for collecting and reporting elec. properties of MOFs, which should help improve the consistency and comparability of reported elec. properties for this important new class of cryst. porous conductors.
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    Mitamura, Y.; Yorimitsu, H.; Oshima, K.; Osuka, A. Straightforward Access to Aryl-Substituted Tetrathiafulvalenes by Palladium-Catalysed Direct C-H Arylation and Their Photophysical and Electrochemical Properties. Chem. Sci. 2011, 2, 2017– 2021,  DOI: 10.1039/c1sc00372k
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    Straightforward access to aryl-substituted tetrathiafulvalenes by palladium-catalyzed direct C-H arylation and their photophysical and electrochemical properties
    Mitamura, Yukihiro; Yorimitsu, Hideki; Oshima, Koichiro; Osuka, Atsuhiro
    Chemical Science (2011), 2 (10), 2017-2021CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    Treatment of tetrathiafulvalene (TTF) with aryl bromides in the presence of Cs carbonate and a Pd catalyst results in direct arylation of TTF. The direct arylation is inherently straightforward and efficient, hence easily creating a large library of aryl TTFs for systematic studies of structure-property relations. The present protocol will thus represent an efficient method for exploiting TTF-based interesting functional materials.
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    The dedicated small-mol. single-crystal X-ray diffraction beamline (I19) at Diamond Light Source has been operational and supporting users for over three years. I19 is a high-flux tunable-wavelength beamline and its key details are described in this article. Much of the work performed on the beamline involves structure detn. from small and weakly diffracting crystals. Other expts. that have been supported to date include structural studies at high pressure, studies of metastable species, variable-temp. crystallog., studies involving gas exchange in porous materials and structural characterizations that require anal. of the diffuse scattering between Bragg reflections. A range of sample environments to facilitate crystallog. studies under non-ambient conditions are available as well as a no. of options for automation. An indication of the scope of the science carried out on the beamline is provided by the range of highlights selected for this paper.
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    The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallog. Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as 'a CIF') contg. embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to ext. the and files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the detn. of abs. structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.
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    New software, OLEX2, was developed for the detn., visualization and anal. of mol. crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure soln., refinement and report generation, as well as novel tools for structure anal. OLEX2 seamlessly links all aspects of the structure soln., refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.

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  • Abstract

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    Figure 1

    Figure 1. (a) Crystal structure of MUV-20a showing the channels along the a-axis. (b) Microporous channel showing the hydrogen-bond interactions (in red) and the π–π stacking (in green) between benzene groups. (c) Distances between sulfur atoms of TTF units in adjacent layers. (d) Different layers showing the interpenetration along the a-axis. The THF molecules present in the pores have been omitted for clarity.

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    Figure 2

    Figure 2. (a) Crystal structure of MUV-20b showing the channels along the a-axis. (b) Microporous channel showing the hydrogen-bond interactions in red. (c) Distances between sulfur atoms of TTF units in adjacent layers. (d) Different layers showing the non-interpenetration of the structure along the a-axis. The ether molecules present in the pores have been omitted for clarity.

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    Figure 3

    Figure 3. (a) Crystal structure of MUV-21 showing the mesoporous channels along the a-axis. (b) Closer view of one microporous channel along the a axis. (c) Distances between sulfur atoms of TTF units in adjacent layers. (d) Different layers showing the non-interpenetrated framework along the a axis. The DMF molecules and DMA+ cations present in the pores have been omitted for clarity.

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    Figure 4

    Figure 4. Gas adsorption isotherms of CO2 on MUV-20a (blue) and MUV-20b (red) at different temperatures. CO2 adsorption and desorption capacities are shown in closed and open circles, respectively.

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    Figure 5

    Figure 5. EPR spectra of MUV-20a (blue), MUV-20b (red), MUV-21 (purple), and the NaH3TTFTB (black) ligand at room temperature.

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    Figure 6

    Figure 6. (a) Schematic representation of deprotonated TTFTB as a carboxylic radical (left) and a zwitterion (right) in MUV-20a and MUV-20b. (b) VBM and CBM calculated for MUV-20a and MUV-21 with an isovalue contour of 0.05 atomic units (au). (c) Electronic band structure diagram (left) and density of states (right) calculated for the zwitterionic ferromagnetic MUV-20a at the HSE06 level. The Fermi level is set to the VBM. Spin-up α and spin-down β channels are displayed in blue and red, respectively. The band gaps of α (2.15 eV) and β (1.68 eV) channels are colored in blue and red, respectively. (d) Spin density of MUV-20a represented with an isovalue contour of 0.008 au. The charge accumulation increase (Δq) for the TTF core and the carboxylate group with respect to the reference isolated, fully protonated TTFTB ligand is indicated.

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    Figure 7

    Figure 7. TTFTB···TTFTB dimeric pairs in the π-stacking arrangement extracted from the minimum-energy crystal structure of MUV-20a (top), MUV-20b (middle), and MUV-21 (bottom). Relevant intermolecular distances and electronic couplings (J) between pairs are indicated.

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    Figure 8

    Figure 8. Preparation of a thin film of MUV-20a using drop casting.

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      Dong, Renhao; Zhang, Tao; Feng, Xinliang
      Chemical Reviews (Washington, DC, United States) (2018), 118 (13), 6189-6235CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      Review highlighting the role of interface-assisted, controlled synthesis of org., inorg., and organometallic two-dimensional materials (2DM) with varied structural features is given. Topics discussed include: introduction; interfacial synthesis overview (interface classifications, interface advantages/uniqueness); 2DM classification (inorg. 2DM, org. [organometallic] 2DM); interfacial synthesis strategies (air/water, liq./liq., liq./solid, gas/solid or vacuum/solid interfaces; layered structure templating; self-sacrificial templates); 2D polymer interfacial synthesis (photopolymn., imine bonds, cyclotrimerization, homocoupling); interfacial synthesis of 2D supramol. polymers; interfacial synthesis of 2D covalent- org. framework films; interfacial synthesis of 2D metal-org. framework films (non-conjugated and conjugated); interfacial synthesis of other sheet-like materials (polymer and non-graphitic C nanosheets); structural and compositional characterization (imaging and spectroscopic methods); conclusions and outlook; and abbreviations and terminol.
    10. 10
      Hoffmann, R. Interaction of Orbitals through Space and through Bonds. Acc. Chem. Res. 1971, 4, 1– 9,  DOI: 10.1021/ar50037a001
      10
      Interaction of orbitals through space and through bonds
      Hoffmann, Roald
      Accounts of Chemical Research (1971), 4 (1), 1-9CODEN: ACHRE4; ISSN:0001-4842.
      A necessary addendum to the chemist's view of a mol. is discussed. Localized orbitals or groups of orbitals may interact with each other directly, through space, or indirectly, through other bonds in the mol. The latter interaction may operate over surprisingly long distances. The primary effects of such interactions and their most direct measure are through ionization potentials and electronic spectra. Stability and reactivity are affected as well. The anal. of these interactions is most conveniently made through the language of perturbation theory; here, as everywhere, the role of symmetry is paramount.
    11. 11
      Batra, A.; Kladnik, G.; Vázquez, H.; Meisner, J. S.; Floreano, L.; Nuckolls, C.; Cvetko, D.; Morgante, A.; Venkataraman, L. Quantifying Through-Space Charge Transfer Dynamics in π-Coupled Molecular Systems. Nat. Commun. 2012, 3, 1086,  DOI: 10.1038/ncomms2083
      11
      Quantifying through-space charge transfer dynamics in π-coupled molecular systems
      Batra Arunabh; Kladnik Gregor; Vazquez Hector; Meisner Jeffrey S; Floreano Luca; Nuckolls Colin; Cvetko Dean; Morgante Alberto; Venkataraman Latha
      Nature communications (2012), 3 (), 1086 ISSN:.
      Understanding the role of intermolecular interaction on through-space charge transfer characteristics in π-stacked molecular systems is central to the rational design of electronic materials. However, a quantitative study of charge transfer in such systems is often difficult because of poor control over molecular morphology. Here we use the core-hole clock implementation of resonant photoemission spectroscopy to study the femtosecond charge-transfer dynamics in cyclophanes, which consist of two precisely stacked π-systems held together by aliphatic chains. We study two systems, [2,2]paracyclophane (22PCP) and [4,4]paracyclophane (44PCP), with inter-ring separations of 3.0 and 4.0 ÅA, respectively. We find that charge transfer across the π-coupled system of 44PCP is 20 times slower than in 22PCP. We attribute this difference to the decreased inter-ring electronic coupling in 44PCP. These measurements illustrate the use of core-hole clock spectroscopy as a general tool for quantifying through-space coupling in π-stacked systems.
    12. 12
      Sirringhaus, H.; Brown, P. J.; Friend, R. H.; Nielsen, M. M.; Bechgaard, K.; Langeveld-Voss, B. M. W.; Spiering, A. J. H.; Janssen, R. A. J.; Meijer, E. W.; Herwig, P.; de Leeuw, D. M. Two-Dimensional Charge Transport in Self-Organized, High-Mobility Conjugated Polymers. Nature 1999, 401, 685– 688,  DOI: 10.1038/44359
      12
      Two-dimensional charge transport in self-organized, high-mobility conjugated polymers
      Sirringhaus, H.; Brown, P. J.; Friend, R. H.; Nielsen, M. M.; Bechgaard, K.; Langeveld-Voss, B. M. W.; Spiering, A. J. H.; Janssen, R. A. J.; Meijer, E. W.; Herwig, P.; De Leeuw, D. M.
      Nature (London) (1999), 401 (6754), 685-688CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)
      Self-organization in many soln.-processed, semiconducting conjugated polymers results in complex microstructures, in which ordered microcryst. domains are embedded in an amorphous matrix. This has important consequences for the elec. properties of these materials: charge transport is usually limited by the most difficult hopping processes and is therefore dominated by the disordered matrix, resulting in low charge-carrier mobility (≤10-5cm2V-1s-1). Here, the authors use thin-film FET transistor structures to probe the transport properties of the ordered microcryst. domains in the conjugated polymer poly(3-hexylthiophene), P3HT. Self-organization in P3HT results in a lamella structure with two-dimensional conjugated sheets formed by interchain stacking. The authors find that, depending on the processing conditions, the lamellae can adopt two different orientations - parallel and normal to the substrate - the mobilities of which differ by more than a factor of 100 and can reach values as high as 0.1 cm2V-1s-1. Optical spectroscopy of the field-induced charge, combined with the mobility anisotropy, reveals the two-dimensional interchain character of the polaronic charge carriers, which exhibit lower relaxation energies than the corresponding radical cations on isolated one-dimensional chains. The possibility of achieving high mobilities via two-dimensional transport in self-organized conjugated lamellae is important for applications of polymer transistors in logic circuits and active-matrix displays.
    13. 13
      Talin, A. A.; Centrone, A.; Ford, A. C.; Foster, M. E.; Stavila, V.; Haney, P.; Kinney, R. A.; Szalai, V.; El Gabaly, F.; Yoon, H. P.; Léonard, F.; Allendorf, M. D. Tunable Electrical Conductivity in Metal-Organic Framework Thin-Film Devices. Science 2014, 343, 66– 69,  DOI: 10.1126/science.1246738
      13
      Tunable electrical conductivity in metal-organic framework thin-film devices
      Talin, A. Alec; Centrone, Andrea; Ford, Alexandra C.; Foster, Michael E.; Stavila, Vitalie; Haney, Paul; Kinney, R. Adam; Szalai, Veronika; El Gabaly, Farid; Yoon, Heayoung P.; Leonard, Francois; Allendorf, Mark D.
      Science (Washington, DC, United States) (2014), 343 (6166), 66-69CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      We report a strategy for realizing tunable elec. cond. in metal-org. frameworks (MOFs) in which the nanopores are infiltrated with redox-active, conjugated guest mols. This approach is demonstrated using thin-film devices of the MOF Cu3(BTC)2 (also known as HKUST-1; BTC, benzene-1,3,5-tricarboxylic acid) infiltrated with the mol. 7,7,8,8-tetracyanoquinododimethane (TCNQ). Tunable, air-stable elec. cond. over 6 orders of magnitude is achieved, with values as high as 7 S per m. Spectroscopic data and 1st-principles modeling suggest that the cond. arises from TCNQ guest mols. bridging the binuclear Cu paddlewheels in the framework, leading to strong electronic coupling between the dimeric Cu subunits. These ohmically conducting porous MOFs could have applications in conformal electronic devices, reconfigurable electronics, and sensors.
    14. 14
      Johnson, E. M.; Ilic, S.; Morris, A. J. Design Strategies for Enhanced Conductivity in Metal-Organic Frameworks. ACS Cent. Sci. 2021, 7, 445– 453,  DOI: 10.1021/acscentsci.1c00047
      14
      Design Strategies for Enhanced Conductivity in Metal-Organic Frameworks
      Johnson, Eric M.; Ilic, Stefan; Morris, Amanda J.
      ACS Central Science (2021), 7 (3), 445-453CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)
      A review. Metal-org. frameworks (MOFs) are a class of materials which exhibit permanent porosity, high surface area, and crystallinity. As a highly tunable middle ground between heterogeneous and homogeneous species, MOFs have the potential to suit a wide variety of applications, many of which require conductive materials. The continued development of conductive MOFs has provided an ever-growing library of materials with both intrinsic and guest-promoted cond., and factors which limit or enhance cond. in MOFs have become more apparent. In this Outlook, the factors which are believed to influence the future of MOF cond. most heavily are highlighted along with proposed methods of further developing these fields. Fundamental studies derived from these methods may provide pathways to raise cond. across a wide range of MOF structures.
    15. 15
      Rubio-Giménez, V.; Galbiati, M.; Castells-Gil, J.; Almora-Barrios, N.; Navarro-Sánchez, J.; Escorcia-Ariza, G.; Mattera, M.; Arnold, T.; Rawle, J.; Tatay, S.; Coronado, E.; Martí-Gastaldo, C. Bottom-Up Fabrication of Semiconductive Metal–Organic Framework Ultrathin Films. Adv. Mater. 2018, 30, 1704291,  DOI: 10.1002/adma.201704291
      There is no corresponding record for this reference.
    16. 16
      Ma, K.; Li, P.; Xin, J. H.; Chen, Y.; Chen, Z.; Goswami, S.; Liu, X.; Kato, S.; Chen, H.; Zhang, X.; Bai, J.; Wasson, M. C.; Maldonado, R. R.; Snurr, R. Q.; Farha, O. K. Ultrastable Mesoporous Hydrogen-Bonded Organic Framework-Based Fiber Composites toward Mustard Gas Detoxification. Cell Rep. Phys. Sci. 2020, 1, 100024,  DOI: 10.1016/j.xcrp.2020.100024
      There is no corresponding record for this reference.
    17. 17
      Ko, M.; Mendecki, L.; Eagleton, A. M.; Durbin, C. G.; Stolz, R. M.; Meng, Z.; Mirica, K. A. Employing Conductive Metal-Organic Frameworks for Voltammetric Detection of Neurochemicals. J. Am. Chem. Soc. 2020, 142, 11717– 11733,  DOI: 10.1021/jacs.9b13402
      17
      Employing Conductive Metal-Organic Frameworks for Voltammetric Detection of Neurochemicals
      Ko, Michael; Mendecki, Lukasz; Eagleton, Aileen M.; Durbin, Claudia G.; Stolz, Robert M.; Meng, Zheng; Mirica, Katherine A.
      Journal of the American Chemical Society (2020), 142 (27), 11717-11733CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      This paper describes the first implementation of an array of two-dimensional (2D) layered conductive metal-org. frameworks (MOFs) as drop-casted film electrodes that facilitate voltammetric detection of redox active neurochems. in a multianalyte soln. The device configuration comprises a glassy carbon electrode modified with a film of conductive MOF (M3HXTP2; M = Ni, Cu; and X = NH, 2,3,6,7,10,11-hexaiminotriphenylene (HITP) or O, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP)). The utility of 2D MOFs in voltammetric sensing is measured by the detection of ascorbic acid (AA), dopamine (DA), uric acid (UA), and serotonin (5-HT) in 0.1 M PBS (pH = 7.4). In particular, Ni3HHTP2 MOFs demonstrated nanomolar detection limits of 63 ± 11 nM for DA and 40 ± 17 nM for 5-HT through a wide concn. range (40 nM-200μM). The applicability in biol. relevant detection was further demonstrated in simulated urine using Ni3HHTP2 MOFs for the detection of 5-HT with a nanomolar detection limit of 63 ± 11 nM for 5-HT through a wide concn. range (63 nM-200μM) in the presence of a const. background of DA. The implementation of conductive MOFs in voltammetric detection holds promise for further development of highly modular, sensitive, selective, and stable electroanal. devices.
    18. 18
      Meng, Z.; Stolz, R. M.; Mendecki, L.; Mirica, K. A. Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials. Chem. Rev. 2019, 119, 478– 598,  DOI: 10.1021/acs.chemrev.8b00311
      18
      Electrically-transduced chemical sensors based on two-dimensional nanomaterials
      Meng, Zheng; Stolz, Robert M.; Mendecki, Lukasz; Mirica, Katherine A.
      Chemical Reviews (Washington, DC, United States) (2019), 119 (1), 478-598CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Elec.-transduced sensors, with their simplicity and compatibility with std. electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high-performance elec.-transduced chem. sensors due to their remarkable electronic and phys. properties originating from their 2D structure. This review highlights the advances in elec.-transduced chem. sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chem. of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and anal. perspective, are summarized for four different groups of analytes: gases, volatile compds., ions, and biomols. The sensing performance is discussed in the context of the mol. design, structure-property relationships, and device fabrication technol. The outlook of challenges and opportunities for 2D nanomaterials for the future development of elec.-transduced sensors is also presented.
    19. 19
      Suzuki, Y.; Gutiérrez, M.; Tanaka, S.; Gomez, E.; Tohnai, N.; Yasuda, N.; Matubayasi, N.; Douhal, A.; Hisaki, I. Construction of Isostructural Hydrogen-Bonded Organic Frameworks: Limitations and Possibilities of Pore Expansion. Chem. Sci. 2021, 12, 9607– 9618,  DOI: 10.1039/d1sc02690a
      19
      Construction of isostructural hydrogen-bonded organic frameworks: limitations and possibilities of pore expansion
      Suzuki, Yuto; Gutierrez, Mario; Tanaka, Senri; Gomez, Eduardo; Tohnai, Norimitsu; Yasuda, Nobuhiro; Matubayasi, Nobuyuki; Douhal, Abderrazzak; Hisaki, Ichiro
      Chemical Science (2021), 12 (28), 9607-9618CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      The library of isostructural porous frameworks enables a systematic survey to optimize the structure and functionality of porous materials. In contrary to metal-org. frameworks (MOFs) and covalent org. frameworks (COFs), a handful of isostructural frameworks have been reported for hydrogen-bonded org. frameworks (HOFs) due to the weakness of the bonds. Herein, we provide a rule-of-thumb to develop isostructural HOFs, where we demonstrate the construction of the third and fourth generation of isostructural HAT-based HOFs (TolHAT-1 and ThiaHAT-1) by considering three important structural factors, that are (1) directional H-bonding, (2) shape-fitted docking of the HAT core, and (3) modulation of peripheral moieties. Their structural and photo-phys. properties including HCl vapor detection are presented. Moreover, TolHAT-1, ThiaHAT-1, and other isostructural HOFs (CPHAT-1 and CBPHAT-1) were thoroughly compared from the viewpoints of structures and properties. Importantly, mol. dynamics (MD) simulation proves to be rationally capable of evaluating the stability of isostructural HOFs. These results can accelerate the development of various isostructural mol. porous materials.
    20. 20
      Wang, B.; Lin, R.-B.; Zhang, Z.; Xiang, S.; Chen, B. Hydrogen-Bonded Organic Frameworks as a Tunable Platform for Functional Materials. J. Am. Chem. Soc. 2020, 142, 14399– 14416,  DOI: 10.1021/jacs.0c06473
      20
      Hydrogen-Bonded Organic Frameworks as a Tunable Platform for Functional Materials
      Wang, Bin; Lin, Rui-Biao; Zhang, Zhangjing; Xiang, Shengchang; Chen, Banglin
      Journal of the American Chemical Society (2020), 142 (34), 14399-14416CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A review. As a novel class of porous cryst. materials, hydrogen-bonded org. frameworks (HOFs), self-assembled from org. or metal-org. building blocks through intermol. hydrogen-bonding interactions, have attracted more and more attention. Over the past decade, a no. of porous HOFs have been constructed through judicious selection of H-bonding motifs, which are further enforced by other weak intermol. interactions such as π-π stacking and van der Waals forces and framework interpenetration. Since the H-bonds are weaker than coordinate and covalent bonds used for the construction of metal-org. frameworks (MOFs) and covalent org. frameworks (COFs), HOFs have some unique features such as mild synthesis condition, soln. processability, easy healing, and regeneration. These features enable HOFs to be a tunable platform for the construction of functional materials. Here, we review the H-bonding motifs used for constructing porous HOFs and highlight some of their applications, including gas sepn. and storage, chiral sepn. and structure detn., fluorescent sensing, heterogeneous catalysis, biol. applications, proton conduction, photoluminescent materials, and membrane-based applications.
    21. 21
      Lin, R.-B.; He, Y.; Li, P.; Wang, H.; Zhou, W.; Chen, B. Multifunctional Porous Hydrogen-Bonded Organic Framework Materials. Chem. Soc. Rev. 2019, 48, 1362– 1389,  DOI: 10.1039/c8cs00155c
      21
      Multifunctional porous hydrogen-bonded organic framework materials
      Lin, Rui-Biao; He, Yabing; Li, Peng; Wang, Hailong; Zhou, Wei; Chen, Banglin
      Chemical Society Reviews (2019), 48 (5), 1362-1389CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Hydrogen-bonded org. frameworks (HOFs) represent an interesting type of polymeric porous materials that can be self-assembled through H-bonding between org. linkers. To realize permanent porosity in HOFs, stable and robust open frameworks can be constructed by judicious selection of rigid mol. building blocks and hydrogen-bonded units with strong H-bonding interactions, in which the framework stability might be further enhanced through framework interpenetration and other types of weak intermol. interactions such as π···π interactions. Owing to the reversible and flexible nature of H-bonding connections, HOFs show high crystallinity, soln. processability, easy healing and purifn. These unique advantages enable HOFs to be used as a highly versatile platform for exploring multifunctional porous materials. Here, the bright potential of HOF materials as multifunctional materials is highlighted in some of the most important applications for gas storage and sepn., mol. recognition, elec. and optical materials, chem. sensing, catalysis, and biomedicine.
    22. 22
      Wang, H.; Li, B.; Wu, H.; Hu, T.-L.; Yao, Z.; Zhou, W.; Xiang, S.; Chen, B. A Flexible Microporous Hydrogen-Bonded Organic Framework for Gas Sorption and Separation. J. Am. Chem. Soc. 2015, 137, 9963– 9970,  DOI: 10.1021/jacs.5b05644
      22
      A Flexible Microporous Hydrogen-Bonded Organic Framework for Gas Sorption and Separation
      Wang, Hailong; Li, Bin; Wu, Hui; Hu, Tong-Liang; Yao, Zizhu; Zhou, Wei; Xiang, Shengchang; Chen, Banglin
      Journal of the American Chemical Society (2015), 137 (31), 9963-9970CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A microporous three-dimensional hydrogen-bonded org. framework (HOF-5) has been constructed from a new org. linker 4,4',4'',4'''-tetra(2,4-diamino-1,3,5-triazin-6-yl)tetraphenylethene. Activated HOF-5a exhibits a stepwise N2 adsorption isotherm at 77 K, suggesting framework flexibility. The structure of activated HOF-5a has been established by powder X-ray diffraction studies, indicating a significant framework contraction from as-synthesized HOF-5 to activated HOF-5a of ∼21% by vol. HOF-5a shows moderately high porosity with a Brunauer-Emmett-Teller (BET) surface area of 1101 m2/g, and takes up a large amt. of acetylene and carbon dioxide under ambient conditions. Powder neutron diffraction studies and theor. calcns. reveal that suitable pore sizes, curvatures, and functional sites collectively enable HOF-5a to encapsulate a high d. of carbon dioxide mols. packed in a pseudo-one-dimensional array along the pore channel.
    23. 23
      Li, P.; He, Y.; Arman, H. D.; Krishna, R.; Wang, H.; Weng, L.; Chen, B. A Microporous Six-Fold Interpenetrated Hydrogen-Bonded Organic Framework for Highly Selective Separation of C2H4/C2H6. Chem. Commun. 2014, 50, 13081– 13084,  DOI: 10.1039/c4cc05506c
      23
      A microporous six-fold interpenetrated hydrogen-bonded organic framework for highly selective separation of C2H4/C2H6
      Li, Peng; He, Yabing; Arman, Hadi D.; Krishna, Rajamani; Wang, Hailong; Weng, Linhong; Chen, Banglin
      Chemical Communications (Cambridge, United Kingdom) (2014), 50 (86), 13081-13084CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A unique 6-fold interpenetrated hydrogen-bonded org. framework (HOF) was developed, for the 1st time, for highly selective sepn. of C2H4/C2H6 at room temp. and normal pressure.
    24. 24
      Liang, W.; Carraro, F.; Solomon, M. B.; Bell, S. G.; Amenitsch, H.; Sumby, C. J.; White, N. G.; Falcaro, P.; Doonan, C. J. Enzyme Encapsulation in a Porous Hydrogen-Bonded Organic Framework. J. Am. Chem. Soc. 2019, 141, 14298– 14305,  DOI: 10.1021/jacs.9b06589
      24
      Enzyme Encapsulation in a Porous Hydrogen-Bonded Organic Framework
      Liang, Weibin; Carraro, Francesco; Solomon, Marcello B.; Bell, Stephen G.; Amenitsch, Heinz; Sumby, Christopher J.; White, Nicholas G.; Falcaro, Paolo; Doonan, Christian J.
      Journal of the American Chemical Society (2019), 141 (36), 14298-14305CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Protection of biol. assemblies is crit. to applications in biotechnol., increasing the durability of enzymes in biocatalysis or potentially stabilizing biotherapeutics during transport and use. Here we show that a porous hydrogen-bonded org. framework (HOF) constructed from water-sol. tetra-amidinium (1·Cl4) and tetracarboxylate (2) building blocks can encapsulate and stabilize biomols. to elevated temp., proteolytic and denaturing agents, and extend the operable pH range for catalase activity. The HOF, which readily retains water within its framework structure, can also protect and retain the activity of enzymes such as alc. oxidase, that are inactive when encapsulated within zeolitic imidazolate framework (ZIF) materials. Such HOF coatings could provide valid alternative materials to ZIFs: they are metal free, possess larger pore apertures, and are stable over a wider, more biol. relevant pH range.
    25. 25
      Sun, Z.-B.; Li, Y.-L.; Zhang, Z.-H.; Li, Z.-F.; Xiao, B.; Li, G. A Path to Improve Proton Conductivity: From a 3D Hydrogen-Bonded Organic Framework to a 3D Copper-Organic Framework. New J. Chem. 2019, 43, 10637– 10644,  DOI: 10.1039/c9nj02025j
      25
      A path to improve proton conductivity: from a 3D hydrogen-bonded organic framework to a 3D copper-organic framework
      Sun, Zhi-Bing; Li, Yi-Lin; Zhang, Zhe-Hua; Li, Zi-Feng; Xiao, Bo; Li, Gang
      New Journal of Chemistry (2019), 43 (26), 10637-10644CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)
      To conduct a comparative study on proton conductivities of a hydrogen-bonded org. framework (HOF) and its related metal-org. framework (MOF), a 3D HOF (HOF-H3L) (H3L = [3-(4-methyl-benzoyl)-thioureido]-acetic acid; CH3C6H4C(O)NHC(S)NHCH2COOH) and its related 3D copper MOF, {[CuI3CuII3L3(DMF)2(CH3OH)(H2O)]·3CH3OH}n (I) is selected and fabricated. Both HOF-H3L and MOF I exhibit high water stability. Their proton conductivities under different relative humidities (RHs) were fully investigated. Note that the MOF I exhibited the optimized cond. of 3.78 × 10-4 S cm-1 that was nearly one order of magnitude larger than that of HOF-H3L (6.91 × 10-5 S cm-1) at 100° and 98% RH. Based on the crystal data, Ea calcns., water vapor absorptions, and PXRD patterns, the proton-conducting mechanisms were suggested. This comparative investigation provides a new inspiration to researchers to design new proton-conductive materials in the future.
    26. 26
      Zhou, H.; Ye, Q.; Wu, X.; Song, J.; Cho, C. M.; Zong, Y.; Tang, B. Z.; Hor, T. S. A.; Yeow, E. K. L.; Xu, J. A Thermally Stable and Reversible Microporous Hydrogen-Bonded Organic Framework: Aggregation Induced Emission and Metal Ion-Sensing Properties. J. Mater. Chem. C 2015, 3, 11874– 11880,  DOI: 10.1039/c5tc02790j
      26
      A thermally stable and reversible microporous hydrogen-bonded organic framework: aggregation induced emission and metal ion-sensing properties
      Zhou, Hui; Ye, Qun; Wu, Xiangyang; Song, Jing; Cho, Ching Mui; Zong, Yun; Tang, Ben Zhong; Hor, T. S. Andy; Yeow, Edwin Kok Lee; Xu, Jianwei
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2015), 3 (45), 11874-11880CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      A microporous hydrogen-bonded org. framework (HOF) derived from a polyhedral oligomeric silsesquioxane (POSS) intermediate and an aggregation-induced emission (AIE) luminogen tetraphenylethene (TPE) deriv. has been synthesized and structurally characterized by various methods. This unique HOF exhibits a permanent porosity with a Brunauer-Emmett-Teller (BET) surface area of 101.9 m2 g-1. This HOF could be well dispersed in org. solvents in the form of nanoparticles with a size of a few hundred nanometers. These nanoparticles are highly fluorescent in org. soln., and exhibit a high fluorescence quenching selectivity towards copper ions. Furthermore, the fluorescence of this HOF could be recovered by the removal of copper ions upon addn. of cyanide and, more interestingly, this process could be repeated several times without considerably sacrificing the sensing activity towards copper ions.
    27. 27
      Han, Y.-F.; Yuan, Y.-X.; Wang, H.-B. Porous Hydrogen-Bonded Organic Frameworks. Molecules 2017, 22, 266,  DOI: 10.3390/molecules22020266
      27
      Porous hydrogen-bonded organic frameworks
      Han, Yi-Fei; Yuan, Ying-Xue; Wang, Hong-Bo
      Molecules (2017), 22 (2), 266/1-266/34CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
      A review. Ordered porous solid-state architectures constructed via non-covalent supramol. self-assembly have attracted increasing interest due to their unique advantages and potential applications. Porous metal-coordination org. frameworks (MOFs) are generated by the assembly of metal coordination centers and org. linkers. Compared to MOFs, porous hydrogen-bonded org. frameworks (HOFs) are readily purified and recovered via simple recrystn. However, due to lacking of sufficiently ability to orientate self-aggregation of building motifs in predictable manners, rational design and prepn. of porous HOFs are still challenging. Herein, we summarize recent developments about porous HOFs and attempt to gain deeper insights into the design strategies of basic building motifs.
    28. 28
      Jana, A.; Bähring, S.; Ishida, M.; Goeb, S.; Canevet, D.; Sallé, M.; Jeppesen, J. O.; Sessler, J. L. Functionalised Tetrathiafulvalene- (TTF-) Macrocycles: Recent Trends in Applied Supramolecular Chemistry. Chem. Soc. Rev. 2018, 47, 5614– 5645,  DOI: 10.1039/c8cs00035b
      28
      Functionalised tetrathiafulvalene- (TTF-) macrocycles: recent trends in applied supramolecular chemistry
      Jana, Atanu; Bahring, Steffen; Ishida, Masatoshi; Goeb, Sebastien; Canevet, David; Salle, Marc; Jeppesen, Jan O.; Sessler, Jonathan L.
      Chemical Society Reviews (2018), 47 (15), 5614-5645CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      Tetrathiafulvalene (TTF) has been extensively explored as a π-electron donor in supramol. systems. Over the last two decades substantial advances have been made in terms of constructing elaborate architectures based on TTF and in exploiting the resulting systems in the context of supramol. host-guest recognition. The inherent electron-donating character of TTF derivs. has led to their use in the construction of highly efficient optoelectronic materials, optical sensors, and electron-transfer ensembles. TTFs are also promising candidates for the development of the so-called "functional materials" that might see use in a range of modern technol. applications. Novel synthetic strategies, coupled with the versatility inherent within the TTF moiety, are now allowing the architecture of TTF-based systems to be tuned precisely and modified for use in specific purposes. In this crit. review, we provide a "state-of-the-art" overview of research involving TTF-based macrocyclic systems with a focus on their use in supramol. host-guest recognition, as components in non-covalent electron transfer systems, and in the construction of "mol. machines".
    29. 29
      Otón, F.; Pfattner, R.; Oxtoby, N. S.; Mas-Torrent, M.; Wurst, K.; Fontrodona, X.; Olivier, Y.; Cornil, J.; Veciana, J.; Rovira, C. Benzodicarbomethoxytetrathiafulvalene Derivatives as Soluble Organic Semiconductors. J. Org. Chem. 2011, 76, 154– 163,  DOI: 10.1021/jo101817j
      29
      Benzodicarbomethoxytetrathiafulvalene Derivatives as Soluble Organic Semiconductors
      Oton, Francisco; Pfattner, Raphael; Oxtoby, Neil S.; Mas-Torrent, Marta; Wurst, Klaus; Fontrodona, Xavier; Olivier, Yoann; Cornil, Jerome; Veciana, Jaume; Rovira, Concepcio
      Journal of Organic Chemistry (2011), 76 (1), 154-163CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
      A series of new tetrathiafulvalene (TTF) derivs. bearing dimethoxycarbonyl and Ph or phthalimidyl groups fused to the TTF core has been synthesized as potential sol. semiconductor materials for org. field-effect transistors (OFETs). The electron-withdrawing substituents lower the energy of the HOMO and LUMO levels and increase the soly. and stability of the semiconducting material. Crystal structures of all new TTF derivs. are also described, and theor. DFT calcns. were carried out to study the potential of the crystals to be used in OFET. In the exptl. study, the best performing device exhibited a hole mobility up to 7.5 × 10-3 cm2 V-1 s-1.
    30. 30
      Ding, B.; Solomon, M. B.; Leong, C. F.; D’Alessandro, D. M. Redox-Active Ligands: Recent Advances towards Their Incorporation into Coordination Polymers and Metal-Organic Frameworks. Coord. Chem. Rev. 2021, 439, 213891,  DOI: 10.1016/j.ccr.2021.213891
      30
      Redox-active ligands: Recent advances towards their incorporation into coordination polymers and metal-organic frameworks
      Ding, Bowen; Solomon, Marcello B.; Leong, Chanel F.; D'Alessandro, Deanna M.
      Coordination Chemistry Reviews (2021), 439 (), 213891CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      Over the past three decades, the field of coordination polymers (CPs) and metal-org. frameworks (MOFs) has developed rapidly due to the potential applications of these materials in gas storage, sepns., catalysis and switching. Introducing redox properties into CPs and MOFs to electrochem. modulate their properties for the development of solid state electronic devices has been an interesting strategy applied in recent years. Notably, a challenge within this area is the engineering of framework materials with desired redox properties targeted at a specific function. This review explores some of the key redox-active ligands that have been investigated within the previous eight years as redox-active components of solid state materials and examines a no. of key strategies for their integration into CPs and MOFs. This review further highlights emergent redox-active ligands in the literature, which take inspiration from the rich field of org. electronics. While these ligands remain largely unexplored in the field of MOFs and CPs, they offer new opportunities for the improvement of solar cells, light induced photo switches, efficient photoelectrocatalysts and long range, rapid charge transfer in MOF materials.
    31. 31
      Jin, S.; Sakurai, T.; Kowalczyk, T.; Dalapati, S.; Xu, F.; Wei, H.; Chen, X.; Gao, J.; Seki, S.; Irle, S.; Jiang, D. Two-Dimensional Tetrathiafulvalene Covalent Organic Frameworks: Towards Latticed Conductive Organic Salts. Chem.─Eur. J. 2014, 20, 14608– 14613,  DOI: 10.1002/chem.201402844
      31
      Two-Dimensional Tetrathiafulvalene Covalent Organic Frameworks: Towards Latticed Conductive Organic Salts
      Jin, Shangbin; Sakurai, Tsuneaki; Kowalczyk, Tim; Dalapati, Sasanka; Xu, Fei; Wei, Hao; Chen, Xiong; Gao, Jia; Seki, Shu; Irle, Stephan; Jiang, Donglin
      Chemistry - A European Journal (2014), 20 (45), 14608-14613CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The construction of a new class of covalent TTF lattice by integrating TTF units into two-dimensional covalent org. frameworks (2-dimensional COFs) is reported. The authors explored a general strategy based on the C2+C2 topol. diagram and applied to the synthesis of microporous and mesoporous TTF COFs. Structural resolns. revealed that both COFs consist of layered lattices with periodic TTF columns and tetragonal open nanochannels. The TTF columns offer predesigned pathways for high-rate hole transport, predominate the HOMO and LUMO levels of the COFs, and are redox active to form org. salts that exhibit enhanced elec. cond. by several orders of magnitude. However, the linkers between the TTF units play a vital role in detg. the carrier mobility and cond. through the perturbation of 2-dimensional sheet conformation and interlayer distance. These results open a way towards designing a new type of TTF materials with stable and predesignable lattice structures for functional exploration.
    32. 32
      Su, J.; Yuan, S.; Wang, H.-Y.; Huang, L.; Ge, J.-Y.; Joseph, E.; Qin, J.; Cagin, T.; Zuo, J.-L.; Zhou, H.-C. Redox-Switchable Breathing Behavior in Tetrathiafulvalene-Based Metal-Organic Frameworks. Nat. Commun. 2017, 8, 2008,  DOI: 10.1038/s41467-017-02256-y
      32
      Redox-switchable breathing behavior in tetrathiafulvalene-based metal-organic frameworks
      Su Jian; Wang Hai-Ying; Ge Jing-Yuan; Zuo Jing-Lin; Yuan Shuai; Joseph Elizabeth; Qin Junsheng; Cagin Tahir; Zhou Hong-Cai; Huang Lan; Zhou Hong-Cai; Cagin Tahir
      Nature communications (2017), 8 (1), 2008 ISSN:.
      Metal-organic frameworks (MOFs) that respond to external stimuli such as guest molecules, temperature, or redox conditions are highly desirable. Herein, we coupled redox-switchable properties with breathing behavior induced by guest molecules in a single framework. Guided by topology, two flexible isomeric MOFs, compounds 1 and 2, with a formula of In(Me2NH2)(TTFTB), were constructed via a combination of [In(COO)4](-) metal nodes and tetratopic tetrathiafulvalene-based linkers (TTFTB). The two compounds show different breathing behaviors upon the introduction of N2. Single-crystal X-ray diffraction, accompanied by molecular simulations, reveals that the breathing mechanism of 1 involves the bending of metal-ligand bonds and the sliding of interpenetrated frameworks, while 2 undergoes simple distortion of linkers. Reversible oxidation and reduction of TTF moieties changes the linker flexibility, which in turn switches the breathing behavior of 2. The redox-switchable breathing behavior can potentially be applied to the design of stimuli-responsive MOFs.
    33. 33
      Castells-Gil, J.; Mañas-Valero, S.; Vitórica-Yrezábal, I. J.; Ananias, D.; Rocha, J.; Santiago, R.; Bromley, S. T.; Baldoví, J. J.; Coronado, E.; Souto, M.; Mínguez Espallargas, G. Electronic, Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal–Organic Frameworks. Chem.─Eur. J. 2019, 25, 12636– 12643
      33
      Electronic, Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal-Organic Frameworks
      Castells-Gil, Javier; Manas-Valero, Samuel; Vitorica-Yrezabal, Inigo J.; Ananias, Duarte; Rocha, Joao; Santiago, Raul; Bromley, Stefan T.; Baldovi, Jose J.; Coronado, Eugenio; Souto, Manuel; Minguez Espallargas, Guillermo
      Chemistry - A European Journal (2019), 25 (54), 12636-12643CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Tetrathiafulvalene-lanthanide (TTF-Ln) metal-org. frameworks (MOFs) are an interesting class of multifunctional materials in which porosity can be combined with electronic properties such as elec. cond., redox activity, luminescence and magnetism. Herein a new family of isostructural TTF-Ln MOFs is reported, denoted as MUV-5(Ln) (Ln = Gd, Tb, Dy, Ho, Er), exhibiting semiconducting properties as a consequence of the short intermol. S···S contacts established along the chain direction between partially oxidized TTF moieties. This family shows photoluminescence properties and single-mol. magnetic behavior, finding near-IR (NIR) photoluminescence in the Yb/Er deriv. and slow relaxation of the magnetization in the Dy and Er derivs. As such properties are dependent on the electronic structure of the lanthanide ion, the immense structural, electronic and functional versatility of this class of materials is emphasized.
    34. 34
      Souto, M.; Romero, J.; Calbo, J.; Vitórica-Yrezábal, I. J.; Zafra, J. L.; Casado, J.; Ortí, E.; Walsh, A.; Mínguez Espallargas, G. Breathing-Dependent Redox Activity in a Tetrathiafulvalene-Based Metal-Organic Framework. J. Am. Chem. Soc. 2018, 140, 10562– 10569,  DOI: 10.1021/jacs.8b05890
      34
      Breathing-Dependent Redox Activity in a Tetrathiafulvalene-Based Metal-Organic Framework
      Souto, Manuel; Romero, Jorge; Calbo, Joaquin; Vitorica-Yrezabal, Inigo J.; Zafra, Jose L.; Casado, Juan; Orti, Enrique; Walsh, Aron; Minguez Espallargas, Guillermo
      Journal of the American Chemical Society (2018), 140 (33), 10562-10569CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      "Breathing" metal-org. frameworks (MOFs) that involve changes in their structural and phys. properties upon an external stimulus are an interesting class of cryst. materials due to their range of potential applications including chem. sensors. The addn. of redox activity opens up a new pathway for multifunctional "breathing" frameworks. Herein, we report the continuous breathing behavior of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, showing a reversible swelling (up to ca. 40% of the vol. cell) upon solvent adsorption. Importantly, the planarity of the TTF linkers is influenced by the breathing behavior of the MOF, directly impacting on its electrochem. properties and thus opening the way for the development of new electrochem. sensors. Quantum chem. calcns. and Raman spectroscopy have been used to provide insights into the tunability of the oxidn. potential.
    35. 35
      Souto, M.; Calbo, J.; Mañas-Valero, S.; Walsh, A.; Mínguez Espallargas, G. Charge-Transfer Interactions between Fullerenes and a Mesoporous Tetrathiafulvalene-Based Metal-Organic Framework. Beilstein J. Nanotechnol. 2019, 10, 1883– 1893,  DOI: 10.3762/bjnano.10.183
      35
      Charge-transfer interactions between fullerenes and a mesoporous tetrathiafulvalene-based metal-organic framework
      Souto, Manuel; Calbo, Joaquin; Manas-Valero, Samuel; Walsh, Aron; Espallargas, Guillermo Minguez
      Beilstein Journal of Nanotechnology (2019), 10 (), 1883-1893CODEN: BJNEAH; ISSN:2190-4286. (Beilstein-Institut zur Foerderung der Chemischen Wissenschaften)
      The design of metal-org. frameworks (MOFs) incorporating electroactive guest mols. in the pores has become a subject of great interest in order to obtain addnl. elec. functionalities within the framework while maintaining porosity. Understanding the charge-transfer (CT) process between the framework and the guest mols. is a crucial step towards the design of new electroactive MOFs. Herein, we present the encapsulation of fullerenes (C60) in a mesoporous tetrathiafulvalene (TTF)-based MOF. The CT process between the electron-acceptor C60 guest and the electron-donor TTF ligand is studied in detail by means of different spectroscopic techniques and d. functional theory (DFT) calcns. Importantly, gas sorption measurements demonstrate that sorption capacity is maintained after encapsulation of fullerenes, whereas the elec. cond. is increased by two orders of magnitude due to the CT interactions between C60 and the TTF-based framework.
    36. 36
      Souto, M.; Santiago-Portillo, A.; Palomino, M.; Vitórica-Yrezábal, I. J.; Vieira, B. J. C.; Waerenborgh, J. C.; Valencia, S.; Navalón, S.; Rey, F.; García, H.; Mínguez Espallargas, G. A Highly Stable and Hierarchical Tetrathiafulvalene-Based Metal-Organic Framework with Improved Performance as a Solid Catalyst. Chem. Sci. 2018, 9, 2413– 2418,  DOI: 10.1039/c7sc04829g
      36
      A highly stable and hierarchical tetrathiafulvalene-based metal-organic framework with improved performance as a solid catalyst
      Souto, Manuel; Santiago-Portillo, Andrea; Palomino, Miguel; Vitorica-Yrezabal, Inigo J.; Vieira, Bruno J. C.; Waerenborgh, Joao C.; Valencia, Susana; Navalon, Sergio; Rey, Fernando; Garcia, Hermenegildo; Minguez Espallargas, Guillermo
      Chemical Science (2018), 9 (9), 2413-2418CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      Herein we report the synthesis of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, which shows a non-interpenetrated hierarchical crystal structure with mesoporous one-dimensional channels of ca. 3 nm and orthogonal microporous channels of ca. 1 nm. This highly stable MOF (aq. soln. with pH values ranging from 2 to 11 and different org. solvents), which possesses the well-known [Fe3(μ3-O)(COO)6] secondary building unit, has proven to be an efficient catalyst for the aerobic oxidn. of dibenzothiophenes.
    37. 37
      Vicent-Morales, M.; Vitórica-Yrezábal, I. J.; Souto, M.; Mínguez Espallargas, G. Influence of Interpenetration on the Flexibility of MUV-2. CrystEngComm 2019, 21, 3031– 3035,  DOI: 10.1039/c9ce00233b
      37
      Influence of interpenetration on the flexibility of MUV-2
      Vicent-Morales, Maria; Vitorica-Yrezabal, Inigo J.; Souto, Manuel; Minguez Espallargas, Guillermo
      CrystEngComm (2019), 21 (19), 3031-3035CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      The crystal structure of an interpenetrated tetrathiafulvalene (TTF)-based metal-org. framework (MOF) is reported. This MOF, denoted as MUV-2-i, is the interpenetrated analog of the hierarchical and flexible MUV-2. Interestingly, the large flexibility exhibited by MUV-2 upon polar solvent adsorption is considerably reduced in the interpenetrated form which can be explained by short S···S interactions between adjacent TTF-based ligands ensuring more rigidity in the framework. In addn., the porosity of MUV-2-i is significantly decreased in comparison to that of MUV-2 as shown by the reduced free vol. in the crystal structure.
    38. 38
      Narayan, T. C.; Miyakai, T.; Seki, S.; Dincă, M. High Charge Mobility in a Tetrathiafulvalene-Based Microporous Metal-Organic Framework. J. Am. Chem. Soc. 2012, 134, 12932– 12935,  DOI: 10.1021/ja3059827
      38
      High Charge Mobility in a Tetrathiafulvalene-Based Microporous Metal-Organic Framework
      Narayan, Tarun C.; Miyakai, Tomoyo; Seki, Shu; Dinca, Mircea
      Journal of the American Chemical Society (2012), 134 (31), 12932-12935CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The tetratopic ligand tetrathiafulvalene-tetrabenzoate (H4TTFTB) was used to synthesize Zn2(TTFTB), a new metal-org. framework that contains columnar stacks of tetrathiafulvalene and benzoate-lined infinite 1-dimensional channels. The new MOF remains porous upon desolvation and exhibits charge mobility commensurate with some of the best org. semiconductors, confirmed by flash-photolysis-time-resolved microwave cond. measurements. Zn2(TTFTB) represents the 1st example of a permanently porous MOF with high charge mobility and may inspire further exploration of the electronic properties of these materials.
    39. 39
      Ding, H.; Li, Y.; Hu, H.; Sun, Y.; Wang, J.; Wang, C.; Wang, C.; Zhang, G.; Wang, B.; Xu, W.; Zhang, D. A Tetrathiafulvalene-Based Electroactive Covalent Organic Framework. Chem.─Eur. J. 2014, 20, 14614– 14618,  DOI: 10.1002/chem.201405330
      39
      A Tetrathiafulvalene-Based Electroactive Covalent Organic Framework
      Ding, Huimin; Li, Yonghai; Hu, Hui; Sun, Yimeng; Wang, Jianguo; Wang, Caixing; Wang, Cheng; Zhang, Guanxin; Wang, Baoshan; Xu, Wei; Zhang, Deqing
      Chemistry - A European Journal (2014), 20 (45), 14614-14618CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Two-dimensional covalent org. frameworks (2-dimensional COFs) provide a unique platform for the mol. design of electronic and optoelectronic materials. Here, the synthesis and characterization of an electroactive COF contg. the known tetrathiafulvalene (TTF) unit is reported. The TTF-COF crystallizes into 2-dimensional sheets with an eclipsed AA stacking motif, and shows high thermal stability and permanent porosity. The presence of TTF units endows the TTF-COF with electron-donating ability, which is characterized by cyclic voltammetry. The open frameworks of TTF-COF are amenable to doping with electron acceptors (e.g., iodine), and the cond. of TTF-COF bulk samples can be improved by doping. The results open up a reliable route for the prepn. of well-ordered conjugated TTF polymers, which hold great potential for applications in fields from mol. electronics to energy storage.
    40. 40
      Hisaki, I.; Emilya Affendy, N. Q.; Tohnai, N. Precise Elucidations of Stacking Manners of Hydrogen-Bonded Two-Dimensional Organic Frameworks Composed of X-Shaped π-Conjugated Systems. CrystEngComm 2017, 19, 4892– 4898,  DOI: 10.1039/c7ce00183e
      40
      Precise elucidations of stacking manners of hydrogen-bonded two-dimensional organic frameworks composed of X-shaped π-conjugated systems
      Hisaki, Ichiro; Emilya Affendy, N. Q.; Tohnai, Norimitsu
      CrystEngComm (2017), 19 (33), 4892-4898CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      Two-dimensional covalent org. frameworks (2D-COFs) composed of π-conjugated components are promising functional materials. In general, however, 2D-COFs exhibit low crystallinity, preventing their precise structural characterization. On the other hand, non-covalent org. frameworks (nCOFs) are often obtained as single crystals due to highly reversible bond formation, and therefore, are possible to complement the structural evaluation of 2D-COFs. In this study, three X-shaped tetracarboxylic acid derivs. with benzene, tetrathiafulvalene (TTF), and pyrazinoquinoxaline cores (X-Ph, X-TTF and X-PyQ, resp.) were revealed to form isostructural, hydrogen-bonded rhombic network (RhomNet) sheets, which subsequently stacked without interpenetration to give low d. frameworks with one-dimensional (1D) inclusion channels. RhomNet structures and their stacking manners were fully revealed based on single crystal X-ray anal. Consequently, we revealed that the RhomNet sheets of X-Ph, X-TTF and X-PyQ stack in different ways depending on the conformation of the peripheral phenylene groups, mol. symmetry and interlayer interactions, in spite of the same network topol. in the RhomNet sheets. The precise characterization of the present RhomNet crystals can provide a new structural insight into porous 2D-COFs.
    41. 41
      Gao, X.-Y.; Li, Y.-L.; Liu, T.-F.; Huang, X.-S.; Cao, R. Single-Crystal-to-Single-Crystal Transformation of Tetrathiafulvalene-Based Hydrogen-Bonded Organic Frameworks. CrystEngComm 2021, 23, 4743– 4747,  DOI: 10.1039/d1ce00519g
      41
      Single-crystal-to-single-crystal transformation of tetrathiafulvalene-based hydrogen-bonded organic frameworks
      Gao, Xiang-Yu; Li, Yu-Lin; Liu, Tian-Fu; Huang, Xin-Song; Cao, Rong
      CrystEngComm (2021), 23 (27), 4743-4747CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      The design and synthesis of a hydrogen-bonded org. framework (HOF) based on tetrathiafulvalene tetracarboxylic acid is reported. The resultant HOF can undergo single-crystal-to-single-crystal transformation to form another two isomers. The structural characteristics and the redox properties of the HOFs were conveniently tailored utilizing the transformation of the phases.
    42. 42
      Kirlikovali, K. O.; Goswami, S.; Mian, M. R.; Krzyaniak, M. D.; Wasielewski, M. R.; Hupp, J. T.; Li, P.; Farha, O. K. An Electrically Conductive Tetrathiafulvalene-Based Hydrogen-Bonded Organic Framework. ACS Mater. Lett. 2022, 4, 128– 135,  DOI: 10.1021/acsmaterialslett.1c00628
      42
      An Electrically Conductive Tetrathiafulvalene-Based Hydrogen-Bonded Organic Framework
      Kirlikovali, Kent O.; Goswami, Subhadip; Mian, Mohammad Rasel; Krzyaniak, Matthew D.; Wasielewski, Michael R.; Hupp, Joseph T.; Li, Peng; Farha, Omar K.
      ACS Materials Letters (2022), 4 (1), 128-135CODEN: AMLCEF; ISSN:2639-4979. (American Chemical Society)
      Recent advancements in the development of conductive metal-org. frameworks (MOFs) and covalent org. frameworks (COFs) have sparked interest in a variety of applications that leverage electronic materials due to the inherent tunability, porosity, and crystallinity assocd. with these materials. Hydrogen-bonded org. frameworks (HOFs) comprise an emerging class of complementary porous materials that assemble cryst. networks mainly from intermol. hydrogen-bonding interactions; however, relatively few reports on functional HOFs exist as these reversible interactions are much weaker than the coordination or covalent bonds found in the former frameworks, which presents addnl. challenges in the isolation and activation of HOFs. In this work, we introduce an approach to access a permanently porous HOF derived from a tetrathiafulvalene (TTF) core, which is the first HOF reported to date that exhibits elec. cond. Upon pptn. from soln., HOF-110 self-assembles in a preferred orientation that contains vertical columns of TTF dimers, and the postsynthetic incorporation of iodine within the nanoporous channels of this framework affords pressed pellet cond. values of up to 6.0 x 10-7 S·cm-1, which is an almost 30-fold improvement compared with pressed pellets of the pristine framework. Extensive structural characterization studies suggest the presence of radical mixed-valence TTF/TTF·+ species within these materials, which is consistent with previous reports on analogous TTF-based MOFs and COFs. Overall, this work presents a viable strategy to develop robust, elec. conductive frameworks built from purely intermol. interactions, further expanding the toolbox available for the assembly of functional porous materials.
    43. 43
      Yang, W.; Yang, F.; Hu, T.-L.; King, S. C.; Wang, H.; Wu, H.; Zhou, W.; Li, J.-R.; Arman, H. D.; Chen, B. Microporous Diaminotriazine-Decorated Porphyrin-Based Hydrogen-Bonded Organic Framework: Permanent Porosity and Proton Conduction. Cryst. Growth Des. 2016, 16, 5831– 5835,  DOI: 10.1021/acs.cgd.6b00924
      43
      Microporous Diaminotriazine-Decorated Porphyrin-Based Hydrogen-Bonded Organic Framework: Permanent Porosity and Proton Conduction
      Yang, Wei; Yang, Fan; Hu, Tong-Liang; King, Stephen Charles; Wang, Hailong; Wu, Hui; Zhou, Wei; Li, Jian-Rong; Arman, Hadi D.; Chen, Banglin
      Crystal Growth & Design (2016), 16 (10), 5831-5835CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      A diaminotriazine-decorated porphyrin-based microporous hydrogen-bonded org. framework has been successfully prepd. and characterized using single crystal X-ray diffraction anal. Its activated phase exhibits permanent porosity, gas sepn., and proton cond. under humid conditions.
    44. 44
      Yang, W.; Li, B.; Wang, H.; Alduhaish, O.; Alfooty, K.; Zayed, M. A.; Li, P.; Arman, H. D.; Chen, B. A Microporous Porphyrin-Based Hydrogen-Bonded Organic Framework for Gas Separation. Cryst. Growth Des. 2015, 15, 2000– 2004,  DOI: 10.1021/acs.cgd.5b00147
      44
      A Microporous Porphyrin-Based Hydrogen-Bonded Organic Framework for Gas Separation
      Yang, Wei; Li, Bin; Wang, Hailong; Alduhaish, Osamah; Alfooty, Khalid; Zayed, Mohie Aldin; Li, Peng; Arman, Hadi D.; Chen, Banglin
      Crystal Growth & Design (2015), 15 (4), 2000-2004CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      A hydrogen-bonded org. framework (HOF), HOF-7 (1), based on a zinc porphyrin-based building block (ZnTDPP, 2) with diaminotriazine moieties has been successfully constructed and structurally characterized (ZnTDPP = 5,10,15,20-tetrakis(4-(2,4-diaminotriazinyl)phenyl)porphyrinato zinc). Single-crystal X-ray diffraction anal. reveals that HOF-7 is built by the 2D layered subunits connected by the intermol. hydrogen-bonding and π-π interaction, exhibiting two kinds of micropores with sizes of 3.2 x 4.7 A2 and 4.2 X 6.7 A2, resp. This HOF exhibits permanent porosities as demonstrated in the CO2 sorption and selective adsorption of CO2 over N2.
    45. 45
      Jackson, H. L.; McCormack, W. B.; Rondestvedt, C. S.; Smeltz, K. C.; Viele, I. E. Control of Peroxidizable Compounds. J. Chem. Educ. 1970, 47, A175,  DOI: 10.1021/ed047pa175
      45
      Control of peroxidizable compounds
      Jackson, Harold Leonard; McCormack, W. B.; Rondestvedt, C. S.; Smeltz, K. C.; Viele, I. E.
      Journal of Chemical Education (1970), 47 (3), A175-A176, A178, A180, A183, A186, A188CODEN: JCEDA8; ISSN:0021-9584.
      In the interest of lab. safety, a study was carried out to det. which chem. structures are potential peroxide formers and hence hazardous. Three lists are presented depending upon the length of time the compds. are safe and the type of reaction that produces the peroxide. These lists are informative and not exhaustive. These compds. form concd. peroxides or else peroxide-initiated polymn. The handling procedures for these compds. are given, as well as labeling instructions. The methods of detection and removal of peroxides are given.
    46. 46
      Kelly, R. J. Review of Safety Guidelines for Peroxidizable Organic Chemicals. Chem. Health Saf. 1996, 3, 28– 36,  DOI: 10.1021/acs.chas.8b03515
      46
      Review of safety guidelines for peroxidizable organic chemicals
      Kelly, Richard J.
      Chemical Health & Safety (1996), 3 (5), 28-36CODEN: CHLSEG; ISSN:1074-9098. (American Chemical Society)
      A review with 29 refs. concerning safety guidelines for hazards and safe handling of peroxidizable org. chems. Topics discussed include: peroxidn. chem.; classes of peroxide formers; hazardous levels of peroxides; inhibitors; control of peroxidizable org. chems. (purchasing and storage, surveillance, use); peroxidizable detection methods (ferrous thiocyanate method, iodide tests, dip strips, titanium sulfate); and removal of peroxides.
    47. 47
      Clark, D. E. Peroxides and Peroxide - Forming Compounds, Chemical Health and Safety. Chem. Health Saf. 2001, 8, 12– 22,  DOI: 10.1016/s1074-9098(01)00247-7
      47
      Peroxides and peroxide-forming compounds
      Clark, D. E.
      Chemical Health & Safety (2001), 8 (5), 12-22CODEN: CHLSEG; ISSN:1074-9098. (Elsevier Science Inc.)
      A review, with refs., discusses the hazards and safety issues assocd. with the lab. use, handling, and storage of inorg. org. peroxy-compds. and peroxide-forming compds. Topics covered include inorg. peroxides and peroxy acids; org. peroxides and other per-compds.; synthesis and use of org. peroxides; storage of org. peroxides and per-compds.; peroxidn. of org. solvents; use and storage of peroxide-forming compds.; detection of peroxides; hazardous levels of org. peroxides; and cleanup and disposal of peroxides and peroxides-forming compds.
    48. 48

      Note that partial protonation (50% fully protonated TTFTBs in the unit cell) in MUV-20a and MUV-20b leads to a significant change in the electronic band structure of the HOF, with a predicted band gap in the β-channel of 0.51 and 0.52 eV, respectively (see Figures S56–S59).

      There is no corresponding record for this reference.
    49. 49

      Note that there is no TTF•+ polaron in the bare MUV-21; hence, chemical or electrochemical oxidation processes need to be considered for hole-carrier generation in this material.

      There is no corresponding record for this reference.
    50. 50

      The VBM splitting was estimated as the energy difference between the VBM and the VBM-1 divided by 2.

      There is no corresponding record for this reference.
    51. 51
      Zeiser, C.; Moretti, L.; Geiger, T.; Kalix, L.; Valencia, A. M.; Maiuri, M.; Cocchi, C.; Bettinger, H. F.; Cerullo, G.; Broch, K. Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene. J. Phys. Chem. Lett. 2021, 12, 7453– 7458,  DOI: 10.1021/acs.jpclett.1c01805
      51
      Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene
      Zeiser, Clemens; Moretti, Luca; Geiger, Thomas; Kalix, Lukas; Valencia, Ana M.; Maiuri, Margherita; Cocchi, Caterina; Bettinger, Holger F.; Cerullo, Giulio; Broch, Katharina
      Journal of Physical Chemistry Letters (2021), 12 (31), 7453-7458CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Singlet fission (SF), the photophys. process in which 1 singlet exciton is transformed into 2 triplets, depends inter alia on the coupling of electronic states. Here, the authors use fluorination and the resulting changes in partial charge distribution across the chromophore backbone as a particularly powerful tool to control this parameter in pentacene. The introduction of a permanent dipole moment leads to an enhanced coupling of Frenkel exciton and charge transfer states and to an increased SF rate which the authors probed using ultrafast transient absorption spectroscopy. These findings are contrasted with H-aggregate formation and a significantly reduced triplet-pair state lifetime in a fluorinated pentacene for which the different partial charge distribution leads to a negligible dipole moment.
    52. 52
      Troisi, A. Charge Transport in High Mobility Molecular Semiconductors: Classical Models and New Theories. Chem. Soc. Rev. 2011, 40, 2347– 2358,  DOI: 10.1039/c0cs00198h
      52
      Charge transport in high mobility molecular semiconductors: classical models and new theories
      Troisi, Alessandro
      Chemical Society Reviews (2011), 40 (5), 2347-2358CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. The theories developed since the fifties to describe charge transport in mol. crystals proved to be inadequate for the most promising classes of high mobility mol. semiconductors identified in the recent years, including for example pentacene and rubrene. After reviewing at an elementary level the classical theories, which still provide the language for the understanding of charge transport in these systems, this tutorial review outlines the recent exptl. and computational evidence that prompted the development of new theories of charge transport in mol. crystals. A crit. discussion will illustrate how very rarely it is possible to assume a charge hopping mechanism for high mobility org. crystals at any temp. Recent models based on the effect of non-local electron-phonon coupling, dynamic disorder, coexistence of localized and delocalized states are reviewed. Addnl., a few more recent avenues of theor. investigation, including the study of defect states, are discussed.
    53. 53
      Sun, L.; Park, S. S.; Sheberla, D.; Dincă, M. Measuring and Reporting Electrical Conductivity in Metal-Organic Frameworks: Cd2(TTFTB) as a Case Study. J. Am. Chem. Soc. 2016, 138, 14772– 14782,  DOI: 10.1021/jacs.6b09345
      53
      Measuring and Reporting Electrical Conductivity in Metal-Organic Frameworks: Cd2(TTFTB) as a Case Study
      Sun, Lei; Park, Sarah S.; Sheberla, Dennis; Dinca, Mircea
      Journal of the American Chemical Society (2016), 138 (44), 14772-14782CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Elec. conductive metal-org. frameworks (MOFs) are emerging as a subclass of porous materials that can have a transformative effect on electronic and renewable energy devices. Systematic advances in these materials depend critically on the accurate and reproducible characterization of their elec. properties. This is made difficult by the numerous techniques available for elec. measurements and the dependence of metrics on device architecture and numerous external variables. These challenges, common to all types of electronic materials and devices, are esp. acute for porous materials, whose high surface area make them even more susceptible to interactions with contaminants in the environment. Here, we use the anisotropic semiconducting framework Cd2(TTFTB) (TTFTB4- = tetrathiafulvalene tetrabenzoate) to benchmark several common methods available for measuring elec. properties in MOFs. We show that factors such as temp., chem. environment (atm.), and illumination conditions affect the quality of the data obtained from these techniques. Consistent results emerge only when these factors are strictly controlled and the morphol. and anisotropy of the Cd2(TTFTB) single-crystal devices are taken into account. Most importantly, we show that depending on the technique, device construction, and/or the environment, a variance of 1 or even 2 orders of magnitude is not uncommon for even just one material if external factors are not controlled consistently. Differences in cond. values of even 2 orders of magnitude should therefore be interpreted with caution, esp. between different research groups comparing different compds. These results allow us to propose a reliable protocol for collecting and reporting elec. properties of MOFs, which should help improve the consistency and comparability of reported elec. properties for this important new class of cryst. porous conductors.
    54. 54
      Mitamura, Y.; Yorimitsu, H.; Oshima, K.; Osuka, A. Straightforward Access to Aryl-Substituted Tetrathiafulvalenes by Palladium-Catalysed Direct C-H Arylation and Their Photophysical and Electrochemical Properties. Chem. Sci. 2011, 2, 2017– 2021,  DOI: 10.1039/c1sc00372k
      54
      Straightforward access to aryl-substituted tetrathiafulvalenes by palladium-catalyzed direct C-H arylation and their photophysical and electrochemical properties
      Mitamura, Yukihiro; Yorimitsu, Hideki; Oshima, Koichiro; Osuka, Atsuhiro
      Chemical Science (2011), 2 (10), 2017-2021CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      Treatment of tetrathiafulvalene (TTF) with aryl bromides in the presence of Cs carbonate and a Pd catalyst results in direct arylation of TTF. The direct arylation is inherently straightforward and efficient, hence easily creating a large library of aryl TTFs for systematic studies of structure-property relations. The present protocol will thus represent an efficient method for exploiting TTF-based interesting functional materials.
    55. 55
      Nowell, H.; Barnett, S. A.; Christensen, K. E.; Teat, S. J.; Allan, D. R. I19, the Small-Molecule Single-Crystal Diffraction Beamline at Diamond Light Source. J. Synchrotron Radiat. 2012, 19, 435– 441,  DOI: 10.1107/s0909049512008801
      55
      I19, the small-molecule single-crystal diffraction beamline at Diamond Light Source
      Nowell, Harriott; Barnett, Sarah A.; Christensen, Kirsten E.; Teat, Simon J.; Allan, David R.
      Journal of Synchrotron Radiation (2012), 19 (3), 435-441CODEN: JSYRES; ISSN:0909-0495. (International Union of Crystallography)
      The dedicated small-mol. single-crystal X-ray diffraction beamline (I19) at Diamond Light Source has been operational and supporting users for over three years. I19 is a high-flux tunable-wavelength beamline and its key details are described in this article. Much of the work performed on the beamline involves structure detn. from small and weakly diffracting crystals. Other expts. that have been supported to date include structural studies at high pressure, studies of metastable species, variable-temp. crystallog., studies involving gas exchange in porous materials and structural characterizations that require anal. of the diffuse scattering between Bragg reflections. A range of sample environments to facilitate crystallog. studies under non-ambient conditions are available as well as a no. of options for automation. An indication of the scope of the science carried out on the beamline is provided by the range of highlights selected for this paper.
    56. 56
      Sheldrick, G. M. Crystal Structure Refinement with SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3– 8,  DOI: 10.1107/s2053229614024218
      56
      Crystal structure refinement with SHELXL
      Sheldrick, George M.
      Acta Crystallographica, Section C: Structural Chemistry (2015), 71 (1), 3-8CODEN: ACSCGG; ISSN:2053-2296. (International Union of Crystallography)
      The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallog. Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as 'a CIF') contg. embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to ext. the and files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the detn. of abs. structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.
    57. 57
      Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. OLEX2: A Complete Structure Solution, Refinement and Analysis Program. J. Appl. Crystallogr. 2009, 42, 339– 341,  DOI: 10.1107/s0021889808042726
      57
      OLEX2: a complete structure solution, refinement and analysis program
      Dolomanov, Oleg V.; Bourhis, Luc J.; Gildea, Richard J.; Howard, Judith A. K.; Puschmann, Horst
      Journal of Applied Crystallography (2009), 42 (2), 339-341CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
      New software, OLEX2, was developed for the detn., visualization and anal. of mol. crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure soln., refinement and report generation, as well as novel tools for structure anal. OLEX2 seamlessly links all aspects of the structure soln., refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.

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