SusChEM: CAREER: High-Resolution X-ray Spectroscopic Studies of Base Metal Catalysis

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With this CAREER award, the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division is funding Professor Kyle M. Lancaster of the Department of Chemistry and Chemical Biology at Cornell University to use cutting-edge X-ray spectroscopies to explore the reactivity of earth-abundant transition metal catalysts. The goal of this research is to determine the mechanisms by which these catalysts effect remarkable chemical transformations including the breakdown of biomass to simple sugars for biofuels and the conversion of natural gas to transportable liquid forms. Understanding the reactivity of catalysts incorporating earth-abundant metals is key to a sustainable chemical future. The proposed work incorporates elements of biochemistry, synthesis, spectroscopy, and theory, affording interdisciplinary training for undergraduate and graduate researchers. The interaction between light and matter that forms the basis of spectroscopy is the foundation for outreach efforts under this project; specifically, hands-on "lab kits" are to be developed for K-12 students to explore properties of light.Valence-to-core X-ray emission spectroscopy, high-energy-resolution fluorescence-detected X-ray absorption spectroscopy and resonant inelastic X-ray scattering are emerging, versatile methods to characterize coordination environments and ligand electronic structures. These methods are being used to probe copper catalysts, defined here as either enzymes or coordination complexes. One such catalyst to be studied is a mononuclear copper enzyme that oxidatively cleaves polysaccharides in biomass such as chitin and cellulose. Stopped-flow kinetics and rapid freeze quench methods are being used to trap reactive copper-oxygen species for X-ray spectroscopic characterization. Nature's copper catalyst for conversion of methane to methanol is a focus of this study. This catalyst is an integral membrane protein whose reactive copper-oxygen species have eluded study by conventional methods. Efforts are to be extended to an abiotic system: copper-catalyzed aerobic alcohol oxidation. This study could demonstrate that the methods to be employed do not necessarily require precise knowledge of precatalysts in order to characterize reaction constituents.