A Computational and Experimental Approach Linking Disorder, High-Pressure Behavior, and Mechanical Properties in UiO Frameworks

• Published in: Angewandte Chemie (International ed.) Vol. 55; no. 7; pp. 2401 - 2405
• Main Authors: Hobday, Claire L., Marshall, Ross J., Murphie, Colin F., Sotelo, Jorge, Richards, Tom, Allan, David R., Düren, Tina, Coudert, François-Xavier, Forgan, Ross S., Morrison, Carole A., Moggach, Stephen A., Bennett, Thomas D.
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 12.02.2016; Wiley Subscription Services, Inc; Wiley-VCH Verlag; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Biphenyl; Chemical Sciences; Communication; Communications; Compression; Computational fluid dynamics; Computer applications; Corrosion resistance; Density; Density functional theory; Diamonds; Functional anatomy; gas separation; high-pressure chemistry; Industrial applications; Material chemistry; Mathematical analysis; Mechanical properties; metal-organic frameworks; Metals; Methanol; Modulus of elasticity; Molecular dynamics; Nonlinearity; or physical chemistry; Pressure; Single crystals; Stability; Stabilization; Strength; structure elucidation; Theoretical and; Topology; X-ray crystallography; X-ray diffraction; X-ray crystallography; high-pressure chemistry; structure elucidation; gas separation; metal-organic frameworks
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201509352

Whilst many metal–organic frameworks possess the chemical stability needed to be used as functional materials, they often lack the physical strength required for industrial applications. Herein, we have investigated the mechanical properties of two UiO‐topology Zr‐MOFs, the planar UiO‐67 ([Zr6O4(OH)4(bpdc)6], bpdc: 4,4′‐biphenyl dicarboxylate) and UiO‐abdc ([Zr6O4(OH)4(abdc)6], abdc: 4,4′‐azobenzene dicarboxylate) by single‐crystal nanoindentation, high‐pressure X‐ray diffraction, density functional theory calculations, and first‐principles molecular dynamics. On increasing pressure, both UiO‐67 and UiO‐abdc were found to be incompressible when filled with methanol molecules within a diamond anvil cell. Stabilization in both cases is attributed to dynamical linker disorder. The diazo‐linker of UiO‐abdc possesses local site disorder, which, in conjunction with its longer nature, also decreases the capacity of the framework to compress and stabilizes it against direct compression, compared to UiO‐67, characterized by a large elastic modulus. The use of non‐linear linkers in the synthesis of UiO‐MOFs therefore creates MOFs that have more rigid mechanical properties over a larger pressure range. Bowed but unbroken: Two Zr‐MOFs of the UiO family are reported. By including flexible azobenzene‐based linkers into the frameworks, the lattices were shown to an exhibit moderate increase in flexibility, along with a dramatic increase in mechanical stability. These results may help design MOFs for useful industrial applications.