(82d) Metal-Organic Frameworks (MOFs) As Catalysts and Catalyst Precursors for Oxidation and Reduction Reactions

Metal-organic frameworks (MOFs) are porous materials that are formed by nodes of metal ions or metal oxide clusters linked by organic ligands; the modularity of these components results in a large set of diverse pore networks useful in various applications. Here, we investigate MOFs as catalysts and catalyst precursors for oxidation, reduction, and dehydrogenation reactions. First, we probe the kinetic mechanism and recyclability of MIL-101 in its Cr and Fe forms for styrene oxidation by hydrogen peroxide. Styrene consumption turnover rates and product distributions are relatively constant across all reaction cycles for MIL-101(Fe), whereas MIL-101(Cr) resulted in increased rates and a different product distribution after the first cycle; the presence of solvated Cr(III) complexes was observed via UV-Vis, indicating that Cr leaching dominates cycling inefficiencies. Second, we utilize MOFs as catalysts precursors that result in unique nanomaterials upon high temperature treatment or under an applied potential. The efficacy of these MOF-derived catalysts, in monometallic Fe and Cu forms, was tested for propane dehydrogenation and CO₂ electrocatalytic reduction, respectively. The effect of external applied driving force on the phase and/or structure of the catalysts, as determined from various characterization techniques, was evaluated along with their catalytic performances. The work shown here provides examples of using MOFs as catalysts and as precursors to synthesize unique, stable catalyst structures with desired rates and selectivities, which we can leverage to optimize green methods for producing valuable organic molecules. Further, this work combines expertise that Michele garnered from working in four different heterogeneous catalysis labs, beginning as a sophomore undergraduate student. The varying scientific techniques and mentoring philosophies have shaped her nascent independent research group at Princeton University.