Oxygen Vacancy-Redox Synergy in a Zr/Fe Metal-Organic Framework Enables Highly Selective Uranyl Photoreduction and Immobilization.

Addressing uranium contamination in tailings wastewater is key to reducing ecological threats and securing the future of nuclear power. The integration of adsorption with in situ photocatalytic U(VI) immobilization has been explored as a green alternative, but charge separation inefficiency and poor ion selectivity continue to hinder its use in complex wastewater. Herein, we constructed a bimetallic metal-organic framework, OVs-Zr/Fe UiO-66-NH2, by incorporating Fe2+/Fe3+ species into the UiO-66-NH2 lattice. The incorporation of Fe into the UiO-66-NH2 lattice narrows the bandgap and improves visible-light absorption. The same Fe doping induces oxygen vacancies (OVs) within the framework. The OVs trap photogenerated electrons to enhance charge separation, while their electron-rich nature favors the selective uptake of UO2 2+. Meanwhile, the Fe2+/Fe3+ redox couple provides an internal electron mediation pathway, directing electrons to the OV-bound uranyl species and promoting the interfacial uranium conversion into stable species. With this combined adsorption-photocatalysis mechanism, OVs-Zr/Fe UiO-66-NH2 removed 99.2% of U(VI) within 6 h under ambient air without sacrificial agents, and its distribution coefficient (K d) reached 1.96 × 105 ml g-1, 11.9 times that of pristine UiO-66-NH2. This work provides a synergistic strategy for crafting photocatalysts with high efficiency and selectivity for sustainable uranium remediation in complex waters.