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|Title:||On the structure-property relationships in framework materials: negative thermal expansion & lithium insertion behaviours|
|Publisher:||The University of Sydney. School of Chemistry.|
|Citation:||Cameron, L. (2014). On the structure-property relationships in framework materials: negative thermal expansion & lithium insertion behaviours. PhD Doctorate. Doctor of Philosophy Ph.D., University of Sydney, Sydney, Australia.|
|Abstract:||A range of Prussian blue analogues were studied here incorporating both changes in bond strength (through variation of oxidation states) as well as more subtle changes such as those resulting from the introduction of vacancy sites. Three series of Prussian blue analogues were investigated here, FeM(CN)6, Fe3[M(CN)6]2 and M3[Co(CN)6]2, where M = two or more of Mn, Fe, Co, Ni, Cu, Zn, Cd, Ru and Ir. In the FeM(CN)6 series, for M = Co and Ir, changing the carbon-bound metal results in variations in the magnitude of NTE, demonstrating that the strength of the M–C bond influences the magnitude of NTE. This result was supported by the behaviour of the Fe3[M(CN)6]2 series, for M = Fe and Ru, where the stronger bonds in the iron analogue result in a lesser degree of NTE. For the M3[Co(CN)6]2 series, where M = Mn, Fe, Co, Ni, Cu, Zn and Cd, comparisons with the MPt(CN)6 series, where M = Mn, Fe, Co, Cu, Zn, and Cd, allowed for closer investigation of the vacancies in Prussian blue analogues. It was found that the introduction of vacancies introduces local disorder into these materials which impact on the bond energies in the frameworks and, consequently, the NTE. Electrochemical investigations on FeFe(CN)6 and FeCo(CN)6 found both compounds able to reversibly insert lithium, with FeFe(CN)6 being able to incorporate three times more lithium in its structure than FeCo(CN)6. Structural studies found that FeIII is reduced in FeCo(CN)6 as lithium is inserted and the carbon-bound FeIII is being reduced in FeFe(CN)6. Powder neutron diffraction studies showed that in both cases lithium was found to prefer a site near the carbon of the cyanide when it is inserted into the framework, suggesting the carbon end of the cyanide is the most attractive force for lithium in the framework. This is a significant result to achieve as lithium sites have yet to be determined in any other Prussian blue analogues. Finally, from investigation of the IRMOF series it was found that local distortions could be incorporated into these structures through addition of functional groups to the bridging ligands. This change in structure caused both a static disorder and a reduction of flexibility in the framework. The introduction of static disorder into these types of frameworks by the functionalisation of the ligand has not previously been observed, and while the effect is small it is still sufficient to have a noticeable effect on the NTE. This is an exciting new strategy for controlling the NTE in these compounds; with the use of more bulky functional groups potentially further perturbing the NTE properties. The author retains copyright of this thesis. It may only be used for the purposes of research and study. It must not be used for any other purposes and may not be transmitted or shared with others without prior permission.|
|Gov't Doc #:||8104|
|Appears in Collections:||Journal Articles|
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