Interfacial Zr-O-N bond-modulated oxygen vacancies in an S-scheme heterojunction for enhanced wastewater purification

UiO-66 derived oxygen-doped g-C₃N₄(OCN)/t-ZrO₂ heterojunctions with Zr-O-N interfacial chemical bonds were successfully prepared via a solid-state grinding and pyrolysis method. The presence of Zr-O-N bonds induced the generation of abundant oxygen vacancies (Ov), which enhanced the surface adsorption of pollutant molecules. Meanwhile, the Zr-O-N bonds acted as "electron channels", optimizing the interfacial contact of the S-scheme heterojunction and suppressing the recombination of photogenerated electron-hole pairs. Moreover, the Ov-mediated degradation pathway dominated by singlet oxygen (¹O₂) and superoxide radicals (˙O₂^-) effectively promoted the efficient degradation and deep mineralization of pollutants, allowing for a triple synergy of "enhanced adsorption-promoted charge separation-regulated reactive species". After 30 min of dark adsorption followed by 120 min of simulated visible-light irradiation, the optimal sample ZOCN-3 achieved a total adsorption-photocatalytic removal of 95.72% for tetracycline hydrochloride (TC) and 97.58% for methylene blue (MB). Its degradation rate constants for TC and MB were 4.56 and 2.66 times those of t-ZrO₂, respectively, with a TOC removal of 61.41% for TC after 120 min. ZOCN-3 also exhibited excellent recyclability, stability, and anti-interference capability. This work offers an interfacial engineering approach for creating MOF-derived S-scheme heterojunctions with superior efficacy in treating wastewater.