Sulfur-Vacancy-Derived Lewis Acid Sites in 3R-Phase ZnIn₂S₄ Nanosheets for Efficient Uranium Extraction From Wastewater

Photocatalytic uranium extraction from wastewater is of great significance for environmental remediation and resource recycling, yet conventional photocatalysts for this purpose suffer from insufficient active sites and low carrier separation efficiency. To address these challenges, we report a rational strategy of constructing sulfur-vacancy-rich Lewis acid sites on two-dimensional 3R-phase ZnIn₂S₄ nanosheets. The sulfur vacancies, acting as electron-deficient centers, serve as robust Lewis acid sites that can preferentially adsorb uranyl ions. Meanwhile, the synergistic effect between the sulfur vacancies and the 3R-phase crystal structure facilitates charge separation and transfer to drive uranyl photoreduction. This integrated strategy achieves a remarkable enhancement in uranium extraction capacity, increasing from 133 (bulk) to 1320 mg/g (sulfur-vacancy-rich nanosheets). Notably, the sample maintains outstanding selectivity for uranium even in the presence of multiple competing ions (each at 100 ppm, K⁺, Ca²⁺, Mg²⁺, Zn²⁺, Co²⁺, Ni²⁺, Pb²⁺, Cu²⁺, Fe³⁺, and V⁵⁺). Furthermore, the material exhibits inherent anti-biofouling performance (≈100% after 3 h) and excellent cycling stability over 10 cycles. Our findings reveal the dual role of sulfur vacancies in photocatalysis as a binding site for uranium and an electronic modulator for charge dynamics, thereby proposing a “phase-defect synergy” design principle for the development of advanced environmental remediation materials.