Coordination frameworks: host-guest chemistry and structural dynamics

Coordination frameworks employ metal ions possessing well defined coordination geometries and an extensive range of molecular bridging ligands with a vast array of functional groups to produce microporous materials with a range of interesting and useful properties. My PhD research is focused towards characterising the structural behaviour of three of these properties in metal-cyanide and metal-imidazolate materials: 1) gas adsorption; 2) metal insertion and; 3) anomalous thermal expansion. Neutron diffraction and scattering are central to all three areas and provide essential information that cannot be readily obtained from other techniques. This is largely due to their sensitivity to light atoms, important for determining the location of light atoms (e.g. CO2 and Li+ ions); their highly penetrating nature, allowing the use of highly specialised sample environments; and their inelastic scattering to provide information on host-guest binding energetics. Gas Adsorption: The primary goal is to elucidate the packing and ordering behaviours of carbon dioxide. These frameworks contain a variety of functional groups which have a known affinity for interaction with CO2, making them suitable for the selective separation of gas mixtures commonly found as flue gas streams of combustion power sources. Metal insertion: The goal is to develop structural understandings of the redox-insertion of lithium and sodium into metal-cyanide phases for the development of new battery electrode materials. Recent work from our group has shown very high reversible loadings of Li into these materials, with in-situ NPD at OPAL used to determine the structures during insertion. Anomalous thermal expansion: Our group has previously investigated the anomalous thermal expansion behaviour in a range of coordination frameworks. Using both NPD and INS, the goal of this project is to develop an even greater understanding of guest influence on these temperature dependent structural behaviours.