Oxygen-Doped Porous g-C₃N₄ via Oxalic Acid-Assisted Thermal Polycondensation as a Visible Light-Driven Photocatalyst for Bisphenol A Degradation

Graphitic phase carbon nitride (g-C 3 N 4 ) demonstrates tremendous potential for photocatalytic degradation of organic pollutants, but its performance is severely limited by the high recombination of photogenerated electron–hole pairs. This study introduces an innovative approach oxalic acid-assisted thermal polycondensation to construct a series of oxygen-doped porous g-C 3 N 4 (OCN) nanostructured materials, which simultaneously utilizes the heat-induced foaming mechanism of oxalic acid to achieve element doping modification. The results indicate that modified OCN-1.5 exhibited the optimal photocatalytic activity. Under visible light conditions, the degradation efficiency of OCN-1.5 catalyst toward bisphenol A (BPA, 30 mg L –1 ) reached 82.55% (240 min light irradiation). This represents a significant improvement of 60% compared to the traditional g-C 3 N 4 catalyst. The mechanism is as follows: on the one hand, the doping of oxygen atoms alter the charge distribution and symmetry of g-C 3 N 4, thereby enhancing the separation efficiency of photogenerated charge carriers. Furthermore, under visible light irradiation, it facilitates the formation of conjugated delocalized systems associated with e – and h + on the surface, leading to an accelerated mineralization degradation of OCN and BPA at the interface. Additionally, the • O 2 – radicals generated from the interfacial reactions can also directly oxidize BPA simultaneously. On the other hand, the construction of a porous nanostructure provides a larger specific surface area and channels for the diffusion of charge carriers, thereby enhancing light capture and transfer. Moreover, this structure offers more active sites for the adsorption and degradation of pollutants. Therefore, the synthetic strategy proposed in this study overcomes the long-standing aggregation issue in the synthesis of g-C 3 N 4, providing a perspective for the scalable preparation of high-performance g-C 3 N 4 photocatalysts and the removal of organic pollutants.