CAREER: SusChEM: Metal Complexes with Pendant Proton Relays for Small Molecule Activation

University Of Southern California, Los Angeles CA

Investigators

Abstract

CHE-1555387 CAREER: Metal Complexes with Pendant Proton Relays for Small Molecule Activation; Smaranda C. Marinescu, University of Southern California (USC) Energy harvested directly from sunlight is an attractive source for filling the global need for power with minimal environmental impact. To avail ourselves of this practically inexhaustible source, several important problems in solar energy capture, storage, and distribution need first to be met in order to harness solar radiation to satisfy global energy demand. One promising method is the use of solar energy to drive chemical reactions that produce easily stored fuels. Carbon dioxide (CO2), the undesirable "greenhouse gas" byproduct of burning fossil fuels and other industrial processes, is potentially an abundant, economic feedstock for solar-driven catalysis to produce hydrocarbon fuels. With inspiration from natural photosynthetic biological systems, Dr. Smarandra Marinescu is developing molecular catalysts for this process. The catalyst architecture is specifically designed with a hydrogen-bonded framework capable of CO2 activation. The research goals of this project are to design and synthesize catalyst complexes of first-row transition metals supported by negatively-charged or neutral molecular fragments (called ligands) able to supply protons needed in the chemical reaction, and to use these metal-ligand complexes to enable conversion of CO2 to CO, the first step in activating the greenhouse gas in the formation of hydrocarbon chemicals. The research has broader societal impact both in developing access to solar energy in an efficient and storable way and in removing the CO2 from the environment, thus turning a harmful waste product into a useful resource. The project also has broader impact in meeting the CAREER-specific criterion of integrating research and educational activities, which involve both students and teachers in the local middle/high schools in energy-related projects and educational experiences. Dr. Marinescu is also developing mentoring programs for women at undergraduate, graduate, and postdoctoral levels to increase the participation of this underrepresented group in science fields. With funding from the Chemical Catalysis Program of the Chemistry Division, Professor Smarandra Marinescu of the Department of Chemistry at University of Southern California is synthesizing several macrocyclic aminopyridine complexes and evaluating their catalytic properties for the reduction of CO2. Preliminary studies indicate that cobalt complexes with pendant NH groups act as efficient electrocatalysts for the reduction of CO2 to CO with excellent Faradaic efficiencies. In comparison, the cobalt complexes with pendant tertiary amines are not as efficient CO2-reduction catalysts, suggesting that the presence of the pendant NH moiety of the secondary amine is crucial for catalysis. Stoichiometric studies are performed to detect and characterize proposed intermediates in the catalytic cycle. The prepared catalysts are studied structurally, electrochemically and spectroscopically to understand their chemical reactivity. These fundamental studies further the fundamental understanding of how hydrogen bonding facilitates the reduction of CO2 and aid in the development of practical catalysts using inexpensive metals. Additionally, there are several broader impacts directly tied to improving and diversifying the pipeline of young scientists interested and engaged in chemistry. The educational components are integrated with energy and catalysis applications, and target middle/high school students and teachers. Dr. Marinescu is also developing mentoring programs for women at undergraduate, graduate, and postdoctoral levels to increase the participation of this underrepresented group in STEM fields.