Enhanced Fenton-like efficiency by the synergistic effect of oxygen vacancies and organics adsorption on FexOy-d-g-C3N4 with Fe‒N complexation.

d-g-C3N4-Fe composites was prepared via a self-assembly and calcination process. According to measurements and density functional theory (DFT) computations, the complexation of iron and pyridinic N of g-C3N4 (Fe‒N) occurred with Fe(III)-π interaction, causing more oxygen vacancies (OVs) with more electrons in iron oxides. In the catalyst air-saturated suspension, the adsorbed pollutants complexed surface Fe(III) through their hydroxyl group donated electrons to around OVs, reducing the surface Fe(III) to Fe(II) and were destructed by Fe(III)-π interaction of the complexation. The addition of H2O2 mainly acted as acceptor being reduced •OH at the OV centers, causing higher degradation rate of pollutants due to both •OH and the surface reaction. However, for the adsorbed hydrophobic pollutants onto the sites of peripheral structure in g-C3N4, H2O2 was mainly decomposed into O2 by the synergistic effect of iron species and OVs. Therefore, the catalyst exhibited high Fenton-like efficiency for the degradation of hydroxyl-containing pollutants and hydrophobic pollutants mixing with the former. Our results demonstrate that the Fe(III)-π interaction could carry out the oxidation of pollutants on the catalyst surface, decreasing the consumption of H2O2, and the role of OVs depends on pollutant adsorption patterns.