(340k) Understanding Solvent Effects in Catalysis and Adsorption in Metal Organic Frameworks

Research Interests: Catalysis, Reaction engineering, Adsorption, Separations, Nanoporous materials, Molecular simulations, Computational chemistry

Nanoporous materials such as metal-organic frameworks (MOFs) have shown promise in numerous applications such as catalysis, adsorption, separations, and drug delivery. Solvents are often used to aid in the catalytic upgrading of biomass to chemicals and have been shown in various systems to help improve reaction rates and selectivities. MOFs provide active sites and large pore sizes that can accommodate reactants and solvents, thereby presenting opportunities to tune the solvent environment inside the pores that can facilitate selective chemical transformations.

Understanding both - the solvent effects on catalysis and solvent adsorption can provide insights into the design of better catalyst-solvent systems. Below, I highlight my research work in these two areas:

Solvent effects in MOF catalysis: We utilize density functional theory calculations supported by experiments to investigate the alcohol solvent effects in transformations involved in biomass-derived glucose to fructose in MOF UiO-66. Specifically, we show that the use of different alcohol solvents, namely - methanol and 1-propanol, lead to significantly different selectivities towards fructose formation. The use of 1-propanol favors the isomerization of glucose to fructose, whereas methanol favors the side reaction of glucose etherification. Our calculations indicate that methanol being the more acidic solvent stabilizes the basic methoxy species involved in the etherification transition state, thereby favoring glucose etherification, in agreement with experiments. These insights are now being used to identify better solvents that improve fructose selectivity.

Solvent adsorption in MOFs: We use force field-based molecular simulations to understand the adsorption of ethanol and water in MOF UiO-66. We demonstrate how the adsorption behavior and solvent structuring are affected by the specific hydrogen-bonding interactions of these solvents with UiO-66 sites. Ethanol and water preferentially bind at carboxylic oxygen atoms of linkers and the μ₃-OH groups at low-to-intermediate relative pressures, showing the degree of hydrophilicity exhibited by UiO-66. We are now using these findings to understand the solvent adsorption behavior in modified UiO-66 with different defects in the framework.

More generally, my computational research in collaboration with experimental researchers highlights the importance of solvent effects in catalysis and adsorption and provides fundamental insights into the interactions between the reactants, solvents, and the MOF catalyst that can guide the development of better MOF/solvent systems. In addition, I have utilized the technical skills learned from these projects to understand other industrially relevant reactive and separation systems involving nanoporous materials like zeolites. These skills have provided me with opportunities for mentoring and collaborating with other researchers in my field.