Theoretical Study of Hydrogen-Bond Interactions of CO _\textbf2 in Organic Absorbent 1, 3-Diphenylguanidine

Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide (CO _2 ) emission into the environment. It has been found that the amine-based organic molecules could absorb CO _2 efficiently and form the bicarbonate salts through hydrogen-bond (H-bond) interactions. Recently, the aqueous 1, 3-diphenylguanidine (DPG) solution was developed to trap and convert CO _2 to valuable chemicals under ambient conditions. However, how the DPG molecules interact with CO _2 in an aqueous solution remains unclear. In this work, we perform molecular dynamics simulations to explore the atomistic details of CO _2 in the aqueous DPG. The simulated results reveal that the protonated DPGH ^+ and the bicarbonate anions prefer to form complexes through different H-bond patterns. These double H-bonds are quite stable in thermodynamics, as indicated from the accurate density functional theory calculations. This study is helpful to understand the catalytic mechanism of CO _2 conversion in the aqueous DPG.