Direct Air Capture of CO₂ with an Amine Resin: A Molecular Modeling Study of the CO₂ Capturing Process

Several reactions, known from other amine systems for CO₂ capture, have been proposed for Lewatit R VP OC 1065. The aim of this molecular modeling study is to elucidate the CO₂ capture process: the physisorption process prior to the CO₂-capture and the reactions. Molecular modeling yields that the resin has a structure with benzyl amine groups on alternating positions in close vicinity of each other. Based on this structure, the preferred adsorption mode of CO₂ and H₂O was established. Next, using standard Density Functional Theory two catalytic reactions responsible for the actual CO₂ capture were identified: direct amine and amine-H₂O catalyzed formation of carbamic acid. The latter is a new type of catalysis. Other reactions are unlikely. Quantitative verification of the molecular modeling results with known experimental CO₂ adsorption isotherms, applying a dual site Langmuir adsorption isotherm model, further supports all results of this molecular modeling study.