Artificial Synthesis and Characterisation of Amorphous Microporous Framework Materials

Mollart, Catherine and Trewin, Abbie (2024) Artificial Synthesis and Characterisation of Amorphous Microporous Framework Materials. PhD thesis, Lancaster University.

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Abstract

In this thesis, four microporous polymer materials are simulated using an artificial synthesis protocol. The resulting models are then compared to experiment to rationalise the structure and properties. The first material discussed is CMP-1, used to rationalise the influence of reaction solvent choice on the porosity of conjugated microporous polymers (CMPs). It was established that the polarity of the solvent relative to the monomer building blocks is crucial to the formation of the polymer framework and resulting pore structure. The second material is a hypercrosslinked polymer (HCP), which, when loaded with azobenzene, shows differing porosities and gas uptakes depending on the presence and isomer of azobenzene. These differences were rationalised due to changes in the micropore region of the pore size distribution, and the ability of cis-azobenzene to interact with carbon dioxide via dipole-quadrupole interactions, rather than the ability of the carbon dioxide to diffuse throughout the material. The third material is organically synthesised porous carbon (OSPC)-1, composed of sp3 hybridised carbon nodes connected by sp hybridised carbon linkers. The solid-state nuclear magnetic resonance (NMR) spectrum of this framework appears to show an alternative structure, and it was rationalised that the framework is composed of dense, interpenetrated, and non-porous polymer chains, surrounded by a thin shell of open, porous OSPC-1, explaining the experimental porosity and NMR. Finally, CTF-1, a covalent triazine framework, is simulated to rationalise the differences in the Fourier-transform infrared spectra of CTF-1 synthesised using high-temperature ionothermal conditions, and the same material synthesised at room temperature, named P1. It was established that the amorphous P1 structure is able to incorporate additional structural diversity within the system, composed of neutral intermediates and alternative ring features formed during the kinetically controlled reaction. The remaining peaks in the spectrum were rationalised as absorbed guest molecules that interact favourably with the framework.