Core-shell MOF@COF photocatalysts for synergistic enhanced U(VI) and tetracycline cleanup through space and carrier separation

Uranium and antibiotics coexisting in natural water bodies pose a significant threat to the environment and human health. Herein, Ti-MOF@DATp was developed by using a metal–organic framework (Ti-MOF) as the core and in-situ growing covalent organic framework (DATp) shells on its surface for simultaneous photocatalytic reduction U(VI) and oxidation tetracycline. The staggered energy levels between Ti-MOF and DATp create a Z-Scheme heterojunction through covalent bonds between them, promoting the charge and holes transfer with enhancing the photocatalytic performance. The Ti-MOF@DATp enables tetracycline passing through the DATp shell while selectively capturing U(VI), then Ti-MOF functions as the site for photooxidation tetracycline, while DATp serves as the site for photoreduction U(VI). The oxidation and reduction of sites can be effectively separated, improving the utilization efficiency of photogenerated electrons and holes. Hence, Ti-MOF@DATp can effectively accomplish the simultaneous photocatalytic removal of 96% U(VI) and 90% tetracycline of their mixture. In comparison to the removal efficiency of 89% for U(VI) and 77% for tetracycline when removal alone, a notable enhancement in performance is observed. Particularly, the removal rate constant of the U(VI) and tetracycline mixture is 55 times higher than that of U(VI) alone and 4 times higher than that of tetracycline alone. Therefore, bifunctional photocatalysts offer an effective approach to tackling complex environmental challenges.