Improving Catalysis Sustainability

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Over the last 5 years, research in the Principal Investigator's (PI) group has developed Pd (palladium) N-heterocyclic carbene (NHC) catalysts to solve synthetic problems in the formation of C-C, C-S, and C-N bonds. With these innovations, processes that only worked under harsh conditions (e.g., strong base, high temperatures) can now be done routinely with mild base at RT. These Pd catalysts have all been commercialized and are being used in laboratories worldwide. While catalysis itself is viewed as one of the Twelve Principals of Green Chemistry, more must be done to make such chemistry truly sustainable. Pd is a popular metal for catalysis because of its unsurpassed broad-spectrum reactivity and selectivity. However, Pd is also among the most scarce elements and goes from being concentrated in mining deposits to being distributed widely into waste streams that do allow the metal to be recovered and recycled, thus essentially losing it forever. Further, the shear volume of earth that has to be moved to find rare metals causes large-scale environmental damage. The overriding objective of this research proposal is to improve catalysis sustainability following four concepts: 1) making longer-living, high reactivity catalysts thereby significantly reducing the amount of metal and associated ligand necessary for catalysis, 2) adapting more abundant metals (e.g., cobalt) for wider synthetic applications through ligand design, 3) devising catalysts to work effectively in more environmentally friendly solvents including water and alcohol, and 4) performing co-catalysis employing enzymes, which are nature's catalysts. In approaching the above objectives four new tools will be developed for the catalysis toolbox that will help make this area of synthetic chemistry more sustainable. Importantly, proposed research targets large-scale chemical production from the outset, so results should be more directly applicable to current manufacturing practices. Specifically, new ligand designs will improve catalyst lifetime allowing far less precious (and non-precious) metals to be used and we will move catalysis away from large-scale organic solvent use by making existing catalytic processes amenable to being conducted in water. White papers of many chemical manufacturers prominently highlight catalysis and biocatalysis as key technologies for achieving a zero-carbon footprint in synthesis, thus significant impact and application of the outcomes in this proposal are anticipated.Important applications being pursued using this methodology include the pursuit of new pharmaceutical and diagnostics agents to battle disease, new materials for the electronics industry, and new agrochemicals to help ensure a reliable food supply. The PI is well connected with companies in these sectors, which will streamline the transformation of these discoveries into goods and services to benefit society.