Mesoporous C-doped C3N5 as a superior photocatalyst for CO2 reduction

Use of naturally abundant solar light for CO2 reduction is a green pathway to reduce carbon footprint. C3N5 is a promising visible-light photocatalyst with enhanced local electron concentration and more active N[dbnd]N sites compared to g-C3N4. We herein report development of mesoporous C-doped C3N5 through a simple copolymerisation of 3-amino-1,2,4-triazole with trimesic acid via hard-templating method, which demonstrated enhanced light absorption ability and delocalised π-electron density (as evident from density functional theory calculation), resulting in efficient charge transfer to the active surface sites of the photocatalyst. The optimised C-doped mesoporous C3N5 exhibited a superior photocatalytic CO2 reduction activity with the CO evolution of 116.6 µmol·g⁻¹, which is 4-fold and 12-fold times higher than that of C3N5 and g-C3N4 respectively. The enhanced photocatalytic CO2 conversion efficiency can be attributed to the synergetic effects of π-electron modulation by C-doping and enhanced surface-active sites brought by mesoporosity.