Spatial charge separation on the (110)/(102) facets of cocatalyst-free ZnIn₂S₄ for the selective conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran

Photorefining of biomass and its derivatives to value-added chemicals is an alternative solution to address the global energy shortage and environmental issues. Herein, efficient and selective oxidation of 5-hydroxymethylfurfural (HMF, 91.1% conversion) to 2,5-diformylfuran (DFF, 99.4% selectivity) is demonstrated by visible light-driven photocatalysis over cocatalyst-free ZnIn₂S₄ nanosheets with crystal facet engineering. The spatial accumulation of photogenerated electrons and holes on the (110) and (102) crystal facets triggers a two-electron oxygen reduction reaction (2e-ORR) for H₂O₂ generation and HMF oxidation into DFF, respectively. The severe attenuation of photostability is caused by the irreversible photocorrosion of Zn-S with the formation of Zn-O chemical bonds by the formation of ˙OH from the in situ decomposition of H₂O₂. Spontaneous substitution of oxygen with sulfur has been proven to efficiently improve the photostability of ZnIn₂S₄. This present work provides insights into improving the durability of ZnIn₂S₄ and sheds new light on biomass valorization via photorefinery.