Michele Sarazen, Assistant Professor in the Department of Chemical and Biological Engineering at Princeton University, Princeton University

"Reaction and deactivation mechanisms of peroxide-mediated oxidations on iron carboxylate MOFs"

Iron-based carboxylate metal-organic frameworks (MOFs; (NH₂-)MIL-101, MIL-100, MOF-235) are active for oxidative reactions utilizing peroxides (hydrogen: H₂O₂; tert-butyl: TBHP) in industrially relevant upstream (alkene oxidation) and downstream (oxidative degradation of wastewater pollutants (methylene blue; MB)) applications. All investigated frameworks exhibit trimeric Fe-oxo nodes, but with varied framework structures, i.e., open MTN zeotype with microporous windows to mesoporous cages (MILs) or more closed ACS topology (MOF-235). We evaluate these systems in polar, aprotic (e.g., acetonitrile) and polar, protic (e.g., water and methanol) solvents, where we show that both reactions involve the generation and reaction of peroxide-derived species, and polar solvents can better stabilize relevant transition states and reactive intermediates. To understand the underlying mechanistic details, we explore the effects of nodal identity, Fe-valency, and pore environment on reaction performance (e.g., turnover rates and product selectivity) and material dynamics and stability. Nodal identity and valency are addressed through measurement (and synthetic control) of defect sites, high temperature pre-activation of Fe centers, and varied capping ligand identities, which can dictate selectivities in complex reaction networks. Further, we show that the solvent identity and coordination environment can affect the extent of effective oxidant utilization and ultimately the stability of the MOF catalyst, with MIL-101 exhibiting reduced stability in water in comparison to acetonitrile. Collectively, this work demonstrates how active intermediate formation is heavily influenced by solvent character and that the resulting nodal and pore coordination environment is important in rationalizing observed selectivity and reactivity trends in Fe-MOF systems.

Bio:

Michele L. Sarazen is an Assistant Professor in the Department of Chemical and Biological Engineering at Princeton University. Her research group couples synthetic, kinetic, and theoretical investigations of porous crystalline materials as catalysts and adsorbents for sustainable fuel and chemical production with an emphasis on reaction and deactivation mechanisms. She earned her BS in Chemical Engineering, summa cum laude, at the Pennsylvania State University and her PhD in Chemical Engineering from the University of California, Berkeley. Before arriving at Princeton, she was a postdoctoral fellow at the Georgia Institute of Technology. Her recognitions include the NSF CAREER Award, AIChE 35 under 35, ICC Young Talent Laureate, Howard B. Wentz, Jr. Junior Faculty Award, National Academy of Engineering Frontiers of Engineering, The Catalysis Review “Mover and Shaker”, and MSDE Outstanding Early Career Paper Award. She has served as a Division Director and D&I Task Force member for AIChE in Catalysis and Reaction Engineering, Director of the Catalysis Society of Metropolitan New York, Early Career Board member for Journal of Catalysis and Applied Catalysis A, and ACS CATL Division Program Chair.