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Title: Synthesis and engineering of metal-organic frameworks for liquid phase applications
Author: Vulpe, Diana
ISNI:       0000 0004 7968 634X
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2019
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Metal-organic frameworks (MOFs) are a class of highly versatile porous materials expressing previously unobserved high surface areas and tuneable both internal and external chemical environments. However, the current shortfall of these structures is insufficient data on their chemical stability as well as the lack of a standardised stability testing approach across literature. Thus, the aims of this work are two develop a comparable way of probing the water stability of MOFs as well as to test their applicability for micro-pollutant capture purposes. UiO-66 MOF showed poor stability in basic environment followed by moderate instability in neutral conditions. On the other hand, the inclusion of functional groups on UiO-66 confer a metal cluster shielding effect which can effectively prevent the diffusion of attacking chemical species into the MOF. Even in large pore size MOFs, the pore collapse inducing capillary effects during direct activation from water can be navigated by inclusion of hydrophobic functionalities. The poor stability of powdered ZIF-8 in acidic media and even in neutral conditions is attested. More importantly, the kinetic stability of ZIF-8 is dramatically improved by shaping into a pure phase monolithic MOF using a sol-gel synthesis process. Whereas the stability of monolithic UiO-66 and MOF-808 still needs improvement, it was found that monolithic MOF- 808 is successfully activated from water after stability testing with almost complete retention of original porosity, its powdered analogue suffered complete amorphisation under the same conditions. The current dissertation also presents a in-situ growth procedure of ZIF-8 on open frontal area honeycomb ceramic cordierite substrate. By tailoring the surface chemistry of the substrate, especially with ZnO, it was found that the growth of ZIF-8 was significantly enhanced, to achieve a uniform and complete surface coverage. ZIF-8 and UiO-66 MOFs were investigated for adsorption of endocrine disruptor micro-pollutant, bisphenol B (BPB). Whereas both MOFs promise very rapid uptake within less than 30 minutes of contact, their respective structural intricacies and stability limitations affect their removal capabilities. Most importantly, the monolithic ZIF-8 configuration yielded superior performance in both flow and batch mode conditions.
Supervisor: Fairen-Jimenez, David Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: metal-organic frameworks ; water treatment ; ZIF-8 ; UiO-66 ; MOF-808 ; adsorption ; endocrine disruptors