Defect-engineered metal-organic framework with enhanced photoreduction activity toward uranium extraction from seawater

Photoreduction conversion of soluble U(VI) to insoluble U(IV) is considered a promising strategy for uranium capture from radioactive wastewater and seawater. Metal-organic frameworks (MOFs) are emerging as potential photocatalysts due to their inherent large surface areas, tunable cavities, and tailorable photo response. Herein, the electronic structure of UiO-66-NH2 (Zr-MOF) is modulated by missing-linker defects and node metal substitution, allowing for the reduced energy needed to transfer the excited linker's electrons to the node's unoccupied d orbitals, which contributes to enhanced photocatalytic uranium extraction capacity. Moreover, the missing-linker defects create more open frameworks, which facilitate fast diffusion of uranyl ions (UO22+) into inner pores and hence increase utilization of the hidden adsorption binding sites. Consequently, light-irradiated Zr/Ti-MOF-25 delivers a high uranium sorption capacity (8.66 ± 0.29 mg-U/g-Ads) with excellent antimicrobial ability in natural seawater. Creation of defects in MOFs opens novel opportunities for enhancing uranium capture through combined complexation and photoreduction.