Engineering unsaturated metal sites in Zn2In2S5 for enhanced photocatalytic selective HMF oxidation

Surfactant-assisted synthesis regulates Zn 2+ vacancies in Zn 2 In 2 S 5 for selective HMF oxidation. • Unsaturated Zn sites enhance charge separation and O 2 activation in photocatalytic biomass conversion. MIL-derived ZnIn 2 S 4 nanosheet network synthesized via MOF templating. Photocatalytic conversion of biomass into value-added chemicals constitutes a promising green and sustainable approach for carbon-neutral resource utilization. Defect engineering has been widely recognized as an effective strategy to modulate the electronic structure and surface redox properties of semiconductor photocatalysts, thereby boosting their catalytic performance. Herein, we report a one-pot hydrothermal synthesis protocol that enables the generation of Zn vacancies on the surface of Zn 2 In 2 S 5 (ZIS) via the introduction of different surfactants, affording a cost-effective and scalable modification strategy. The optimal catalyst, denoted as Z V IS-1, which is rich in Zn 2+ vacancies, exhibits exceptional performance in the visible-light-driven aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF). Specifically, Z V IS-1 achieves an HMF conversion of 72.2% and a DFF yield of 65.9% under optimized reaction conditions, corresponding to a 4.0-fold enhancement compared to pristine ZIS (16.5% DFF yield). The DFF formation rate over Z V IS-1 reaches 2108 μmol·g −1 ·h −1 , which is among the highest values reported for sulfide-based photocatalysts in this reaction system. Comprehensive characterization and mechanistic studies reveal that the introduced Zn 2+ vacancies not only promote the separation and migration of photogenerated charge carriers, but also serve as active sites for O 2 activation and HMF adsorption, effectively mitigating the intrinsic limitation of insufficient surface reactivity of pristine ZIS. This work provides new insights into the rational design of defect-engineered semiconductor photocatalysts for efficient and sustainable biomass valorization. Zn-vacancy-engineered Zn 2 In 2 S 5 nanoflowers achieve selective photocatalytic oxidation of HMF to DFF with enhanced charge separation and oxygen activation capability. Download: Download high-res image (96KB) Download: Download full-size image