Water Effect on CO2 Adsorption Kinetics in Amine-Functionalized Silicas Assessed Using the Density Functional Theory

Amine-grafted silicas are potential candidates for a variety of applications ranging from heterogeneous catalysis to CO2 capture. The presence of moisture is inevitable in almost all real-life applications, and these are very hygroscopic materials. A density functional theory study is conducted to better understand the effect of moisture on the CO2 capture mechanism using an amine-functionalized silica support. It is found that the presence of water reduces up to 7 times the activation barrier of the capture reaction. Moreover, the combination of water and free surface silanol groups leads to a more stabilized product and favors the formation of ammonium carbamate over carbamic acid. A vibrational analysis has been conducted to show the effect of water on signature bond vibrations. These vibrational frequencies were compared with the experimental infrared spectra from the literature to better understand the surface chemistry.