Direct Elucidation of the Gas Adsorption Behaviour of Metal-Organic Frameworks (MOFs) by In-situ Single Crystal X-ray Diffraction

Metal-organic frameworks (MOFs) form the largest group of crystalline nanoporous material that has been receiving global research attention, as evidenced by the several thousand MOFs reported within the ca. 21000 research papers produced over the past 20 years. MOFs have huge potential for a wide variety of applications including gas storage and separation technologies and are being sold as commercial products for gas storage/ release applications of highly toxic gases, for example, PH3, and in a controlled release product that prevents fruit ripening.
MOFs exhibit a range of exciting gas adsorption phenomena including hysteresis, and stepped and gated adsorption when gases such as nitrogen, carbon dioxide, methane, hydrogen disulphide are adsorbed. These phenomena are often facilitated by framework structural changes. Gas adsorption and other data have demonstrated the existence of these gas adsorption phenomena and computational modelling has provided some predicative insight into the structural mechanism of their action. However, few experimentally determined crystal structures exist for these materials during these adsorption behaviours which prevent critical comprehension of these novel behaviours.
This project aims to determine the gas adsorption behaviour of certain rigid and flexible framework MOFs by experimentally determining the crystal structures of the MOFs during single crystal-to-single crystal transitions instigated by different loadings of a diverse variety of industrially relevant gases at various temperatures and pressures.
The project will involve the synthesis of known or modified MOFs in single crystal form, characterisation including single crystal and powder X-ray diffraction, scanning electron microscopy, gas adsorption measurements and other associated spectroscopic techniques. Particular emphasis of the project will be on using in-situ single crystal X-ray crystallography to obtain the crystal structures of gas loaded MOFs using state-of-the art single crystal X-ray diffractometers and a capillary gas cell (operating temperature range 100 - 500 K, pressure range 0 - 15 bar).
Success of the project will enable experimental determination of the actual mechanisms for these adsorption processes that will be highly attractive to the academic and industrial communities and, through greater understanding, will enable enhanced design of future multifunctional nanoporous materials.