Acid and Base Gas Exposure and Solvent Effects on Metal-Organic Framework Structure and Gas Adsorption Properties
Mounfield, William Pratt
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With carbon dioxide emissions from the combustion of coal, oil and natural gas comprising nearly 80% of worldwide emissions, and with total global emissions on the rise, the need for high-performance, low-cost sorbent materials is ever growing. Solids adsorbents have garnered much interest as CO2 adsorbents as they offer the ability to reduce the regeneration penalty that plagues modern amine scrubbers due to their much lower heat capacities. One class of solid adsorbents is metal-organic frameworks (MOFs). These inorganic-organic hybrid materials have shown promise for a wide range of applications in adsorption separations and catalysis, owing to their high surface areas, vast selection of metal sources and organic linkers, and tunable chemical properties. The development of the chemical intuition necessary for targeted experimental synthesis of novel structures would revolutionize the field of adsorption and allow access to the enormous array of chemical and structural properties of these materials. In this dissertation, an investigation on the effects of synthesis solvent and acid gas adsorption on the structure and gas adsorption properties of several MOF structures was performed. The study of MIL-53(Al) revealed that synthesis solvent plays an important role in the structure and CO2 adsorption properties of the framework, a finding that can be leveraged for modification of these properties for specific applications. A comprehensive investigation of the effects of acid gas adsorption on MIL-125 allowed the determination of the degradation mechanism in the presence of water and SO2. This study provided an experimental and computational pathway for the determination of acid gas degradation effects in other MOFs. Finally, a mixed MgAl oxide was explored as a beneficial binding material to increase the adsorption of composites formed with UiO-66 and provide an avenue for future studies of increased adsorption in MOF composites.