CAS: Collaborative Research: Macrocyclic and Supramolecular Pincer Catalysts Using Ruthenium and First Row Metals for Carbon Dioxide Reduction

With the support of the Chemical Catalysis program in the Division of Chemistry, Elizabeth T. Papish of The University of Alabama, Jared H. Delcamp of The University of Mississippi, and Charles Edwin Webster of Mississippi State University will study the transformation of the greenhouse gas carbon dioxide into synthetic fuels with new metal catalysts of novel structure.

Envisioning a sunlight-driven energy infrastructure in our future requires efficient and robust catalysts that can power artificial photochemically driven reactions for fuel production. Using sunlight to create fuels as stored chemical energy available on demand is attractive relative to our current fossil fuel-reliant infrastructure. Nonetheless, this vision requires fast, durable, and selective catalysts that would ideally utilize readily available and affordable metals where feasible.

The current lack of such catalysts represents a significant gap in the current knowledge base. The investigators will design new catalysts for carbon dioxide reduction to fuels with innovative structures previously untested. They will work on controlling and understanding carbon dioxide reduction through design of robust and highly active catalysts via synthetic, mechanistic, and computational studies.

These studies can elucidate the factors that impact catalysis and eventually lead to the production of solar fuels from a greenhouse gas in a carbon neutral fashion. The results of this research are to be shared broadly, and this project is expected to help train a diverse group of 10-15 undergraduate and graduate students over the project period. The investigators will visit local schools for outreach events and host high school students in their research laboratories.

In addition, undergraduate students will perform catalytic reactions in a teaching lab setting, and the results will be shared with the community, to offer educational experiences along with experiment verification.

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Elizabeth T. Papish of The University of Alabama, and her collaborators, Jared H. Delcamp of The University of Mississippi, and Charles Edwin Webster of Mississippi State University, will study carbon dioxide reduction with new metal catalysts containing first row transition metals and macrocyclic ligands.

More efficient, robust, and selective catalysts are needed for artificial photochemical schemes aimed at converting carbon dioxide to fuels or fuel precursors. Using prior experience in the synthesis and testing of efficient self-sensitized catalysts that retain activity in water, the collaborative team will work on designing new robust catalysts using two strategies: active site isolation via use of a macrocyclic pincer ligand, and low-coordinate metal complexes via the use of low-valent metals.

Synthetic, mechanistic, and computational studies will be directed toward three goals: (1) to increase the understanding of CNC-pincer ligated first-row metal catalysts, (2) to expand the knowledge of under-explored supramolecular catalysts with iridium photosensitizers, and (3) to understand the behavior of homogeneous catalysts linked to semiconductor electrodes. The long-term goal is to move the field of molecular catalyst design closer to a durable, earth-abundant metal-based catalyst system for the photocatalytic reduction of carbon dioxide coupled to water splitting in a solar powered photo-electrochemical cell using the knowledge gained in the above tasks.

Applying these ideas systematically to first-row metals is still largely uncharted territory, with the potential payoff being understanding how to make solar fuels with first row-metal complexes. The scientific results will be communicated through publications, presentations, and patents; the broader impacts will include outreach events and catalysis research experiments in an undergraduate teaching laboratory setting.

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.