CAS: CAREER: Light-Initiated C-H Functionalization by Metal Oxo Complexes for Sustainable Light Hydrocarbon Upgrading

Louisiana State University, Baton Rouge LA

Investigators

Abstract

With the funding from the Chemical Catalysis (CAT) Program of the Division of Chemistry (CHE) and the Established Program to Stimulate Competitive Research (EPSCoR) office, Matthey Chambers of the Louisiana State University (LSU) will work to develop methods to employ solar energy (light) as a renewable energy source to drive the conversion of hydrocarbons to commodity chemicals. Hydrocarbon functionalization is the cornerstone of the chemical industry and the energy economy, but methods for generating value-added commodity chemicals and fuels today typically rely on high temperatures, high pressures, and environmentally hazardous reagents. This has the consequence of dramatic energy usage, as steam reforming and related processes account for 1-10% of global energy consumption. Motivated by biological systems that efficiently use special molecular cofactors containing metal-oxygen active sites, this project will investigate the manner in which interactions with light can actuate these motifs to selectively mediate the catalytic conversion of inert hydrocarbons to products. As the director of LSU’s ChemDemo program, Dr. Chambers will actively engage communities and provides hands-on science experiences to underserved and underrepresented K-12 students throughout the region. This project has potential long term broader impacts related to sustainable catalysis of relevance to the chemical industry. Matthew Chambers and his group will investigate the factors that underpin early transition metal oxo photochemical properties (light absorption, emission energy, and lifetimes) and reactivity patterns. Photochemical characterization will be achieved via steady-state and transient luminescence spectroscopy and product distributions will be determined by NMR spectroscopy and GC-MS analysis. An emphasis will be placed on more oxophilic platforms as, upon excitation, these systems may efficiently activate C–H bonds while allowing the activated substrate to undergo a diverse array of follow-up reactivity to achieve a broad range of products. The selectivity of these transformations is related experimentally and computationally to the M–OH bond dissociation energies of the intermediates as this is thought to be the critical parameter influencing product selectivity. Also under investigation will be methodologies to achieve efficient and stable photocatalytic platforms. Kinetic studies will aim to identify the key steps during the reoxidation of the metal oxo photocatalyst while ancillary ligand field variations are directed at developing an understanding of the critical features impacting photocatalysis. Collectively, these aims are expected to lead to enhanced understanding of metal oxo photochemistry and the parameters that underpin selectivity. Understanding the factors that influence the catalytic reactivity of photoexcited metal oxos would constitute enabling technology, with potential applicability to the development of new petrochemical technologies and fuel-forming reactions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.