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Synthesis, physicochemical and atomistic analysis of templated polymerisation in metal-organic frameworks (MOFs)

Mehta, Nimai 2021. Synthesis, physicochemical and atomistic analysis of templated polymerisation in metal-organic frameworks (MOFs). PhD Thesis, Cardiff University.
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Abstract

Metal-organic frameworks (MOFs) are porous three-dimensional coordination networks comprised of metal nodes that are covalently bound to organic linkers in an array. These materials are attractive due to their porosity and structural diversity. A variety of MOFs in the literature has been used as templates for polymerisation reaction, where MOFs act as hosts for guest monomers that then polymerise in situ, allowing synthesis of highly porous polymer networks. Many of the studies are focussed on achieving polymerisation under confinement, but there is a lack in understanding of the fundamental mechanistic interpretation of processes involved. In this work, prototypical frameworks MOF-5 and HKUST-1 have been used as hosts for polymerising biocompatible and biodegradable monomers vinyl acetate, lactic acid, lactide, and ε-caprolactone. A range of techniques have been used to characterise the MOFs, monomer@MOF, polymer@MOF composites, and polymers isolated from the MOFs. Characterisation of polymer@MOF composites by SEM confirmed intrinsic polymerisation, with typically 65 % conversion of monomer determined by 1H-NMR spectroscopy. Powder X-ray diffraction experiments showed an expansion of unit cell of both frameworks after monomer adsorption, followed by contraction after polymerisation. For the vinyl acetate@MOF-5 system, guest specific binding, guest-framework interactions, polymerisation kinetics, and changes in local framework mobility have been investigated by single crystal X-ray diffraction, solid-state NMR, total neutron scattering, quasi-elastic neutron scattering and neutron spectroscopy. Experiments suggest binding of monomer at the MOF metal nodes, and close association with the linker groups, which are lost following polymerisation. Working with the Disordered Materials Group at ISIS Pulsed Neutron and Muon Source at Rutherford Appleton Laboratories (Oxfordshire, UK), the monomer@MOF composites were investigated in the first simulations of confined liquids in crystalline solid materials to be performed on the Dissolve simulation environment. The combination of simulation and experimental data has provided the first atomic-scale resolution of monomer@MOF composites.

Item Type: Thesis (PhD)
Date Type: Submission
Status: Unpublished
Schools: Chemistry
Date of First Compliant Deposit: 1 April 2022
Last Modified: 04 Apr 2022 16:03
URI: https://orca.cardiff.ac.uk/id/eprint/149014

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