Potassium and Sulfur Dual Sites on Highly Crystalline Carbon Nitride for Photocatalytic Biorefinery and CO2 Reduction

The co-production of high-value-added chemicals and fuels by coupling biomass photooxidation with carbon dioxide (CO2) photoreduction has attracted wide interest. Nevertheless, there still lacks comprehensive studies. Herein, we synthesized a highly crystalline carbon nitride with potassium and sulfur dual sites (K/S@CN-x) by a salt-template-assisted incorporation method. The incorporation of K/S and high crystallinity resulted in the photocatalytic performance by significantly enhancing the visible-light absorption and accelerated photogenerated charge separation/transfer. Thus, in K/S@CN-0.5, the carbon monoxide (CO) evolution rate (16.27 μmol g–1 h–1) and lactic acid yield (78.07%) were 4.80 times and 1.15 times, respectively, those of CN. Furthermore, density functional theory calculations were performed to investigate the role of K and S dual sites in photocatalytic reactions. Our findings provide unique routes for synthesizing highly crystalline photocatalysts with dual sites and demonstrate the feasibility of photocatalytic selective oxidation of biomass coupled with CO2 reduction.