FTIR study of CO₂ adsorption on amine-grafted SBA-15: Elucidation of adsorbed species

The interaction between amines and CO₂ offers a possible route for the catalytic activation of CO₂. In situ infrared spectroscopy was used to study the interaction of CO₂ with aminegrafted SBA-15. We employed three different types of amine-grafted SBA-15 surfaces to quantify the effect distinct tethered amine moieties have on the chemistry of CO₂ interacting with amine-grafted SBA-15. When the SBA-15 surface has a low density of amines and is "capped" to mitigate against interactions with surface-bound moieties, no new chemical species are observed on exposure to carbon dioxide. An ionic carbamate and a surface-bound carbamate are observed on the other SBA-15 surfaces on exposure to CO₂. The formation of carbamates decreases the bond order of the carbon oxygen bond of the carbon dioxide molecule. The role of the different amine moieties and the surface silanol groups in the formation of the carbamates is discussed. Our results suggest that controlling the local environment around surface-grafted amines, which could be achieved by the use of suitably engineered surface environments, could facilitate the adsorption and activation of CO₂.