Metal-Organic Framework Liquids, Gels and Glasses

Seminar | January 19 | 4-5 p.m. | 120 Latimer Hall

 Tom Bennett, Department of Materials Science and Metallurgy, University of Cambridge

 College of Chemistry

Crystalline solids dominate the field of metal−organic frameworks (MOFs),1 with access to the liquid and glass states of matter usually prohibited by relatively low temperatures of thermal decomposition. Recently, I have demonstrated the melting three dimensional MOFs belonging to the zeolitic imidazolate framework (ZIF) family, of chemical composition Zn(Im)2 (Im – C3H3N2].2 The mechanism of melting is investigated by in-situ pair distribution function measurements and simultaneous DFT-based MD calculations,3 which provide pathways in generalizing the approach to other MOF systems. Cooling of these ZIF liquids yields glasses, which are chemically and structurally distinct from the three other existing categories of melt-quenched glasses (inorganic nonmetallic, organic, and metallic), and retain the basic metal–ligand connectivity of their parent crystalline frameworks.

These new families of metal-organic framework materials, called MOF-glasses and MOF-liquids have been characterized, and are further discussed in this lecture. The possibilities for the future expansion of the MOF field into these new areas are presented, along with structure property relationships gained by linking crystal chemistry to framework melting temperature (Tm) and physical behaviour of the glass-forming liquids.

In the second part of the talk, I consider the UiO family of MOFs, and their collapse to form amorphous MOFs upon mechanical stress.4 I will also cover MOF-gels, and in particular describe the synthesis and structure of gels in several UiO-based frameworks. Electron microscopy and X-ray diffraction reveal these gels to consist of MOF nanoparticles of ca 10nm diameter, which agglomerate upon solvent removal. Importantly, we use the gels to ‘cast’ beads using bespoke equipment.5

[1] T. D. Bennett*, A. K. Cheetham. A. H. Fuchs and F. X. Coudert*, Nat. Chem., 2017, 9, 11-16.
[2] T. D. Bennett* et al, Nat. Commun, 2015, 6, 8079.
[3] T. D. Bennett* et al, Nat. Mater, 2017, accepted manuscript.
[4] T. D. Bennett* et al, Phys. Chem. Chem. Phys., 2016,18, 2192-2201.
[5] B. Bueken et al, Chem. Sci. 2017, 8, 3939-3948.

 Light refreshments will be served at 3:50 at The Coffee Lab, 510-643-0572