A catalytic role of surface silanol groups in CO2 capture on the amine-anchored silica support

Abstract

A new mechanism of CO₂ capture on the amine-functionalized silica support is demonstrated using density functional theory calculations, in which the silica surface not only acts as a support to anchor amines, but also can actively participate in the CO₂ capture process through a facile proton transfer reaction with the amine groups. The surface-mediated proton transfer mechanism in forming a carbamate–ammonium product has lower kinetic barrier (8.1 kcal mol⁻¹) than the generally accepted intermolecular mechanism (12.7 kcal mol⁻¹) under dry conditions, and comparable to that of the water-assisted intermolecular mechanism (6.0 kcal mol⁻¹) under humid conditions. These findings suggest that the CO₂ adsorption on the amine-anchored silica surface would mostly occur via the rate-determining proton transfer step that is catalyzed by the surface silanol groups.