Significantly enhanced photocatalytic performance of the W-Zr-MOF-NH2@TpTt-COF heterostructure for tetracycline removal by defects engineering

A hollow heterojunction of W-Zr-MOF-NH2@TpTt-COF (WZT) was fabricated by combining etched W-Zr-MOF-NH2 with TpTt-COF. WZT, synthesized through acid etching and hydrothermal methods, showed better tetracycline degradation than pure W-Zr-MOF-NH2 and pure TpTt-COF due to its larger specific surface area and more active sites. The surface of WZT contains abundant oxygen vacancies (OVs) that capture electrons, promoting the separation of photogenerated e−-h+ pairs and increasing WZT's photocatalytic activity. WZT (1:1, mass) showed 87 % degradation of tetracycline under 300 W Xenon lamp irradiation. The results of cycling experiments demonstrated the high stability and reusability of WZT (1:1), making it feasible for production. The excellent photocatalytic degradation of tetracycline by WZT (1:1) originates from the formation of heterojunctions and the presence of surface OVs, which reduces the strong photogenerated e−-h+ complexation efficiency. Possible photocatalytic degradation mechanisms are proposed while demonstrating the formation of Z-scheme heterojunction in WZT, which aligned with the experimental results of electron spin resonance (ESR). The tetracycline oxidative decomposition process involves the participation of •OH, 1O2, •O2-, e−, and h+ as proven by ESR and radical trapping experiments. This work proposes a research idea to prepare high-performance photocatalysts with MOF@COF type, featuring OVs-rich and Z-scheme heterojunctions.