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

Abstract

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.