Well-dispersed g-C3N4 nanophases in mesoporous silica channels and their catalytic activity for carbon dioxide activation and conversion

Well-dispersed g-C3N4 nanophases in SBA-15 mesochannels were prepared by a two-step vapor condensation of dicyandiamide. Defect-containing g-C3N4 nanophases were active catalysts for CO2 activation. Activated CO2 species were steadily converted to target compounds with a high selectivity. The presence of doped metal ions markedly promoted the catalytic activity and selectivity. Zn2+-doped g-C3N4/SBA-15 showed a high activity in transferring CO2 to epoxides. Fe3+-doped g-C3N4/SBA-15 was an efficient catalyst for the direct oxidative cycloadditon of CO2 to olefins. Styrene was converted into 4-phenyl-1, 3-dioxolan-2-one. The process conversion was 34.1% and the selectivity to the oxidative cycloaddition product reached 93%. The recyclability of SBA-15 supported g-C3N4 nanophases was investigated through a five-run test. Their catalytic activity and microstructures were kept constant during the five-run recycling test. No marked metal leaching was detected during each test.