1. Non-Crystalline Metal-organic frameworks and coordination polymers
Metal–organic frameworks are a novel family of chemically diverse materials, with applications in a wide field covering engineering, physics, chemistry, biology and medicine. Research so far has focused almost entirely on crystalline structures, yet a clear trend has emerged shifting the emphasis onto disordered states of MOFs, including “defective by design” crystals, as well as amorphous phases such as glasses and gels. The group has pioneered the synthesis, characterization and potential applications of non-crystalline MOFs. These include liquids, glasses and, to some extent, gels.
T. D Bennett* and S. Horike*, Nat. Rev. Mater., 2018, DOI: 10.1038/s41578-018-0054-3
2. Metal-Organic Framework Liquids
Here we introduce a MOF liquid, a strongly associated liquid obtained by melting a zeolitic imidazolate framework (ZIF), with retention of chemical configuration, coordinative bonding modes, and porosity of the parent crystalline framework. We combine in-situ variable temperature X-ray, ex-situ neutron pair distribution function experiments, and first principles molecular dynamics simulations to study the melting phenomenon and the nature of the liquid obtained, focusing on structural characterization at the molecular scale, dynamics of the species, and thermodynamics of the solid–liquid transition.
R. Gaillac, P. Pullumbi, K. A. Beyer, K. W. Chapman, D. A. Keen, T. D. Bennett and F. X. Coudert, Nat. Mater., 2017, 16, 1149-1145
3. Metal-Organic Framework Glasses
The glasses formed by quenching MOF liquids contain both inorganic, and organic components. They are thus the first new category of glass (outside of traditional inorganic, organic and metallic categories) to be discovered since the latter in the 1970s. After our initial discovery, we have worked to look at (i) the expansion of the glass forming MOF family, and (ii) the optical, porous and mechanical properties of the resultant glasses.
C. Zhou, L. Longley, A. Krajnc, G. J. Smales, A. Qiao, I. Erucar, C. M. Doherty, A. W. Thornton, A. J. Hill, C. W. Ashling, O. T. Qazvini, S. J. Lee, P. A. Chater, N. J. Terrill, A. J. Smith, Y. Yue, G. Mali, D. A. Keen, S. G. Telfer and T. D. Bennett, Nat. Commum., 2018, 9, 5042.
T. D. Bennett*, Y. Yue, P. Lim A. Qiao, H. Tao, G. N. Greaves, T. Richards, G. I. Lampronti, Simon. A. T. Redfern, F. Blanc, O. K. Farha, J. T. Hupp, A. K. Cheetham and D. A. Keen, J. Am. Chem. Soc., 2016, 138, 3484-3492.
J. Hou, M. L. R. Gómez, A. Krajnc, A. McCaul, S. Li, A. M. Bumstead, A. F. Sapnik, Z. Deng, R. Lin, P. A. Chater, D. S. Keeble, D. A. Keen, D. Appadoo, B. Chan, V. Chen, G. Mali, T. D. Bennett,* J. Am. Chem. Soc., 2020, DOI: 10.1021/jacs.9b11639.
4. metal-organic framework crystal-glass composites
The majority of research into metal-organic frameworks (MOFs) focuses on their crystalline nature. Recent research has revealed solid-liquid transitions within the family, which we use here to create a class of functional, stable and porous composite materials by embedding crystalline MOFs into a MOF-glass. In our work to date we have shown that these metal-organic framework crystal glass composites (MOF-CGCs) enable highly porous, unstable crystalline MOFs to exist at room temperature (Publication 1). For example, the coordinative bonding and chemical structure of a MIL-53 crystalline phase are preserved within the ZIF-62 glass matrix. Whilst separated phases, the interfacial interactions between the closely contacted microdomains improve the mechanical properties of the composite glass. More significantly, the high temperature open pore phase of MIL-53, which spontaneously transforms to a narrow pore upon cooling in the presence of water, is stabilised at room temperature in the crystal-glass composite. This leads to a significant improvement of CO2 adsorption capacity.
J. Hou, C. W. Ashling, S. M. Collins, A. Krajnc, C. Zhou, L. Longley, D. N. Johnstone, P. Chater, S. Li, M. V. Coulet, P. L. Llewellyn, F. X. Coudert, D. A. Keen, P. A. Midgley, G. Mali, V. Chen, T. D. Bennett,* Nat. Commun., 2019, 10, 2580.
C. W. Ashling, D. N. Johnstone, R. N. Widmer, J. Hou, S. M. Collins, A. F. Sapnik, A. Bumstead, P. A. Chater, D. A. Keen and Thomas. D. Bennett*, J. Am. Chem. Soc., 2019, 141, 15641-15648.
5. High Pressure – High Temperature Phase Diagrams of MOFs
R. N. Widmer, G. I. Lampronti, S. Anzellini, R. Gaillac, S. Farsang, C. Zhou, A. M. Belenguer, H. Palmer, A. K. Kleppe, M. T. Wharmby, S. A. T. Redfern, F. X. Coudert, S. G. Macleod, T. D. Bennett,* Nat. Mater., 2019, DOI: 10.1038/s41563-019-0317-4.
R. N. Widmer, G. I. Lampronti, S. Chibani, C. W. Wilson, S. Anzellini, S. Farsang, A. K. Kleppe, N. P. M. Casati, S. G. MacLeod, S. A. T. Redfern, F. X. Coudert and T. D. Bennett*, J. Am. Chem. Soc., 2019, 141, 9330-9337.
6. Metal-Organic Frameworks Gels and Monoliths
The ability of metal-organic frameworks (MOFs) to gelate under specific synthetic conditions opens up new opportunities in the preparation and shaping of hierarchically porous MOF monoliths, which could be directly implemented for catalytic and adsorptive applications. In this work, we present the first examples of xero- or aerogel monoliths consisting solely of nanoparticles of several prototypical Zr4+ -based MOFs: UiO-66-X (X = H, NH2, NO2, (OH)2), UiO-67, MOF-801, MOF-808 and NU-1000. High reactant and water concentrations during synthesis were observed to induce the formation of gels, which were converted to monolithic materials by drying in air or supercritical CO2. Electron microscopy, combined with N2 physisorption experiments, was used to show that an irregular nanoparticle packing leads to pure MOF monoliths with hierarchical pore systems, featuring both intraparticle micropores and interparticle mesopores. Finally, UiO-66 gels were shaped into monolithic spheres of 600 m diameter using an oil-drop method, creating promising candidates for packedbed catalytic or adsorptive applications, where hierarchical pore systems can greatly mitigate mass transfer limitations.
B. Bueken, N. Van Velthoven, T. Willhammar, T. Stassin, I. Stassen, D. A. Keen, G. V. Baron, J. F. M. Denayer, R. Ameloot, S. Bals, D. De Vos* and T. D. Bennett* Chem. Sci., 2017, 8, 3939-3948.
J. Hou, A. F. Sapnik and T. D. Bennett*, Chem. Sci., 2020, 11, 310-323.