Tensile Lattice Strain via Sulfur Vacancies Activates Interlayer Charge Transfer in ZnIn ₂ S ₄ for Superior Photocatalytic U(VI) Removal

Lattice strain engineering in semiconductors offers a powerful avenue to precisely tune band structures and lower interfacial potential barriers, thus dramatically accelerating interfacial charge transfer rates. However, the practical application of conventional ZnIn2S4 in photocatalytic U(VI) removal is primarily hampered by its limited charge separation efficiency and the inherent interlayer charge transfer barrier. To overcome these limitations, we herein report a strategy of engineering sulfur vacancies to deliberately induce tensile lattice strain in ZnIn2S4. The created sulfur vacancies function dually as electron-relay centers for accelerated carrier migration and as initiators of tensile strain that modulates the band structure. More critically, this strain significantly enhances the electronic coupling between the In–S and Zn–S layers, thereby facilitating interlayer charge transfer. Benefiting from this dual mechanism, the optimally strained ZnIn2S4 achieves a remarkable U(VI) removal efficiency of 98.36% within 50 min under light irradiation, outperforming its vacancy-free counterpart by 2.08-fold. This work highlights the pivotal yet overlooked role of vacancy-induced tensile lattice strain in simultaneously regulating charge transport and interlayer interaction, providing a novel design principle for multilayer photocatalysts.