Constructing Carbon Nitride Donor-Acceptor Structures by Vacancy Engineering and Sulfone-Containing Molecule Grafting for Photocatalytic CO2 Reduction.

Carbon nitride (CN) has attracted extensive attention in the field of photocatalytic CO2 reduction owing to its controllable structure and low preparation cost. However, it suffers from severe recombination of photogenerated carriers and strong localization of the π-conjugated system, leading to unsatisfactory photocatalytic performance. Although defect engineering can enhance charge separation by breaking the periodic structure of CN, the π-electron delocalization remains confined. Meanwhile, constructing donor-acceptor (D-A) structures with conjugated π-systems can extend electron delocalization and promote charge transfer. Herein, by introducing carbon vacancies and grafting sulfone-containing electron-withdrawing molecules, we prepare photocatalysts with intramolecular D-A structure (VC-DSDA), where the sulfone unit bridges electron-rich triazine rings to facilitate directional charge transfer. Density functional theory (DFT) calculations show that the synergistic effect of vacancy engineering with the D-A structure breaks the periodic structure of CN and extends the π-electron off-domain range, which significantly improves the separation efficiency of the photogenerated charges. As a result, the optimized 5% VC-DSDA achieves a remarkable CO generation rate of 35.57 μmol g-1 h-1, which was 6.4 and 2.6 times higher than that of pristine and vacancy-modified CN. This article demonstrates a dual-regulation strategy for designing high-performance CN photocatalysts through defect engineering and molecular grafting.