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

Abstract

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, 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 to create MOF-derived S-scheme heterojunctions with superior efficacy in treating wastewater.