Microscopic mechanism of CO2 adsorption on M2+(M = Fe, Ca, Mg)-doped kaolinite (001) surface: DFT calculations

To investigate the microscopic mechanism of CO2 adsorption on the M2+ (M = Fe, Ca, Mg)-doped kaolinite (denoted the M2+-Kao) (0 0 1) surface of low-priced metal cation, density functional theory (DFT) was employed to simulate CO2 adsorption on the perfect-phase kaolinite (denoted Kao) (0 0 1) surface and the M2+-Kao (0 0 1) surface. The results show that M2+ doping mainly enhances the activity of H atoms on the surface, and the order of CO2 adsorption on M2+-Kao (0 0 1) surface was Fe2+-Kao > Ca2+-Kao > Mg2+-Kao. The adsorption energy calculation results indicate that CO2 can be stably adsorbed on both the Kao (0 0 1) surface and the M2+-Kao (0 0 1) surface. The adsorption mechanism of CO2 on the M2+-Kao (0 0 1) surface involves the combined action of hydrogen bonding and electrostatic interactions, with the latter being the main contributor. The results provide valuable theoretical and technical insights for the preparation of clay-based CO2 mineralized functional materials.