Interaction of CO, CO2 and CH4 with mesoporous organosilica: Periodic DFT calculations with dispersion corrections

The interaction of CO, CO2 and CH4, with the internal walls of p-phenylenesilica has been studied using periodic supercell DFT calculations and adding specific corrections to include dispersion forces. Two models of p-phenylenesilica have been considered, with different number of silanols on the surface and characterized by a different sequence of silica rings. The three molecules interact preferentially with the silanol groups with adsorption energies typical of a physisorbed state (CO 14.3 kJ/mol, CO2 13.3 kJ/mol, CH4 9.2 kJ/mol). The dispersion part of the interaction is substantial, being about one half of the total value. We also considered possible ways to modify the adsorption properties by doping or modifying the inorganic or organic parts of the framework. In particular, we have introduced Ti–OH, Si–O− and Al−–OH groups or altered the organic part of the framework, but in no case an increase of the adsorption energy has been observed.