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Photophysical Studies of Multilayer Two-Dimensional Covalent Organic Frameworks

Nowicka-Dylag, Caroline Vanessa; (2020) Photophysical Studies of Multilayer Two-Dimensional Covalent Organic Frameworks. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis studies the photophysical properties of multilayer two-dimensional (2D) covalent organic frameworks (COFs). COFs are a type of crystalline porous polymer which allow the atomically precise incorporation of organic units to create structures with predesigned skeletons and nanopores. In all COFs the molecules are linked via covalent bonds within the single layers, which is an important characteristic that defines these materials. This leads to a variety of applications; for example, catalysis, gas storage, adsorption and optoelectronics. This thesis focuses on porphyrins to make COFs via a Schiff-base condensation reaction. Porphyrins have been studied for decades and have been shown to have interesting photophysical properties, such as the generation of triplet states and charge states. The synthesis of the COFs was mainly studied using scanning tunnelling microscopy (STM), and supported using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The photophysical properties of the porphyrin COFs was studied using transient absorption spectroscopy (TAS). The STM results have shown a successful synthesis of 2D-COFs but the synthesis is not reliable nor reproducible which is a large stumbling block. The TAS results have shown a difference when comparing the porphyrins, and then COFs, in solution and as a multilayer film. In a solution the porphyrins exhibit triplet states. However, as a film the porphyrins and COFs exhibit charge states and subsequent bimolecular recombination. The generation of charge states was then compared between the porphyrin film precursor and subsequent COF film and the differences have been expanded upon in the thesis. Future work to improve the synthesis of the COF films and further photophysical studies have also been included.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Photophysical Studies of Multilayer Two-Dimensional Covalent Organic Frameworks
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10111940
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