Phosphine Modulation for Enhanced CO₂Capture: Quantum Mechanics Predictions of New Materials

It is imperative to develop efficient CO2 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 CO2 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 CO2, we find that the CO2 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 CO2 binding, and we elucidate which chemical descriptors correlate directly with CO2 binding energy. Specifically, we find that charge accumulation on the CO2 unit of the CO2-bound adduct has the greatest correlation with CO2 binding affinity. Finally, we probe the mechanism for CO2 reduction to CO and methanol in aqueous media.