Phosphine Modulation for Enhanced CO Capture: Quantum Mechanics Predictions of New Materials.

It is imperative to develop efficient CO capture and activation technologies to combat the rising levels of deleterious greenhouse gases in the atmosphere. Using Quantum Mechanics methods (Density Functional Theory), we propose and evaluate several metal-free and metal-containing phosphines that provide strong CO binding under ambient conditions. Depending on the electron donating capacity of the phosphine and the ability of the P-bound ligands to hydrogen bond to the CO, we find that the CO binding can be as strong as -18.6 kcal/mol downhill, which should be quite adequate for ambient conditions. We explore some modifications of the phosphine to improve CO binding, and we elucidate which chemical descriptors correlate directly with CO binding energy. Specifically, we find that charge accumulation on the CO unit of the CO-bound adduct has the greatest correlation with CO binding affinity. Finally, we probe the mechanism for CO reduction to CO and methanol in aqueous media.