Defect-engineered metal-organic framework with enhanced photoreduction activity toward uranium extraction from seawater
Tao Liu, Shuai Tang, Tao Wei, Mengwei Chen, Zuji Xie, Ruoqian Zhang, Yinjiang Liu, Ning Wang
Abstract
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.