DFT modeling of CO2 capture mechanism over (N-methylaminopropyl)-trimethoxysilane-modified mesoporous silica

Determination of the CO2 interaction mechanisms with amine-modified solid adsorbents plays an important role in the development of highly efficient sorbents that would meet the future requirements to mitigate the severe effects of global warming. Accordingly, this study aimed to examine the CO2 capture mechanism over trimethoxy[3-(methylamino)propyl]silane (MAPS)-functionalized mesoporous silica using DFT modeling and to clarify the effect of free surface silanol density as well as amine density on the capture mechanism. Our calculations indicated that carbamic acid and ammonium carbamate were the two main products, formation of both requiring amine pairs rather than isolated amine structures. Besides, surface silanols were observed to play a significant role on the capture of CO2, they were not only effective on the stabilization of the adsorption species but can also directly participate in the reaction mechanism. Amine functionality, on the other hand, seemed to be less deterministic on the capture under the conditions employed in this study.