Sulfoxide‐Functionalized Mesoporous C 3 N 5 as a Metal‐Free and Visible‐Light‐Driven Efficient Photocatalyst for CO 2 Reduction

Abstract Photocatalytic CO 2 reduction reaction provides a promising green strategy to mitigate atmospheric CO 2 levels and simultaneously achieve valuable chemicals. C 3 N 5 has emerged as an excellent metal‐free photocatalyst for CO 2 RR due to its narrow bandgap with a lower conduction band edge, which provides high reduction potential to reduce thermodynamically stable CO 2 molecules. Surface functionalization and enhanced porosity can yield superior catalytic performance in C 3 N 5 . The recent efforts to synthesize sulfoxide‐functionalized mesoporous C 3 N 5 is reported, which enhances CO 2 RR up to 4.4 times (94.8 ± 11.2 µmol·g −1 in 8 h) that of intact C 3 N 5 . According to Ultraviolet Photoelectron Spectroscopy analysis, while the functionalization of the C 3 N 5 surface with sulfoxide groups leaves the valence band position unchanged, it significantly shifts the conduction band position toward a more negative potential, thereby enhancing material reduction capabilities. Additionally, steady‐state photoluminescence and transient absorption and time‐resolved photoluminescence spectra indicate a significant reduction in exciton recombination. Insights from theoretical calculations reveal that SO‐functionalization enhances CO 2 adsorption and CO desorption, thereby facilitating enhanced photocatalytic CO 2 reduction.