Our thermochemical research seeks to establish the chemical basis for processes that convert CO₂ into high-volume products. To be viable, these processes must minimize energy intensity, avoid consuming stoichiometric reagents, and produce no waste. Ideally, they would also afford a distinct chemical advantage or process intensification relative to a conventional route. Our strategy is inspired by the simplicity of the natural Calvin-Benson cycle in nature, which uses acid-base chemistry (C–H deprotonation) to generate a reactive intermediate that engages CO₂ in C–C bond formation. We seek to generalize this strategy by developing ways to use carbonate (CO₃^2–) to promote C–H carboxylation reactions, which can be incorporated into closed cycles (no waste generation) for synthesizing carboxylic acids. Building on these studies, we are also developing catalysts that use acid-base chemistry to catalyze CO₂ hydrogenation, providing a way to convert the chemical energy of H₂ into carbon-containing fuels.

C–H bonds are very weak acids and cannot be deprotonated by a weak base such as CO₃^2– in conventional reaction media. We have found that solvent-free systems composed of alkali salts enable CO₃^2– to reversibly deprotonate very weakly acidic C–H bonds at intermediate temperatures, generating carbanions that readily trap CO₂ to form carboxylates (C–CO₂^–). We have used this reaction to develop a novel process for synthesizing furan-2,5-dicarboxylic acid (FDCA), a monomer that is used to make performance-advantaged polyester plastic. Our carboxylation route sources FDCA from CO₂ and inedible biomass and eliminates much of the complexity of competing processes that make FDCA from fructose. We have also applied carbonate-promoted C–H carboxylation to generate polyamide monomers from furfurylamine, a feedstock prepared in one step from furfural. These application-focused projects have led to fundamental studies to investigate the phase behavior of solvent-free systems and explore their utility for other bond-forming reactions.

We are also developing ways to perform C–H carboxylation as a gas–solid reaction with substrates that can be volatilized. We have found that dispersing alkali carbonates (M₂CO₃) in mesoporous materials disrupts the crystalline lattice, resulting in amorphous surface carbonates that are capable of deprotonating un-activated C–H bonds at elevated temperature in the presence of CO₂. We have demonstrated that these materials can be used to perform C–H carboxylation of aromatic hydrocarbons such as benzene and naphthalene. Ongoing efforts seek to discern the local structure of these amorphous carbonates, develop strategies to further enhance their basicity, and broaden the substrate scope.