Enhanced photocatalytic performance of S-doped covalent triazine framework for organic pollutant degradation

Photocatalysis using the abundant solar energy is an environmentally friendly and efficient way to degrade organic matter. Covalent triazine frameworks (CTFs), a new class of metal-free organic semiconductors responsive to visible light, are promising materials for water treatment. In this study, an original CTF, namely CTF-1, was modified by S-doping to form CTFSx, which were used as metal-free catalysts for degradation of methyl orange (MO) and bisphenol A (BPA). The outcomes demonstrated that the photocatalytic degradation of MO and BPA by CTFSx was superior to that by CTF-1, with better stability and reusability. Within 6 h, 53.2% MO and 84.7% BPA were degraded by CTFS5, and the degradation rate constants were 0.145 h(-1) and 0.29 h(-1), respectively, which were 3.6 and 5.8 times higher than those of CTF-1. Further investigation revealed that enhanced visible light absorption, a reduced degree of free carrier recombination, rapid separation and transfer of photogenerated electrons and holes, and improved center dot OH oxidation capacity were important factors contributing to the significantly enhanced photocatalytic activity. The S-doping method effectively improved the light absorption performance, electronic structure, and modulation band structure of CTF-1. This work highlights the potential application of low-cost metal-free catalysts driven by visible light for the removal of organic pollutants from wastewater.