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.

Automated summary

Photorefining of biomass and its derivatives to value-added chemicals offers a solution to global energy shortage and environmental issues. In this study, efficient and selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) was achieved using visible light-driven photocatalysis over cocatalyst-free ZnIn2S4 nanosheets with crystal facet engineering. The use of (110) and (102) crystal facets allowed for the spatial accumulation of photogenerated electrons and holes, enabling a two-electron oxygen reduction reaction (2e-ORR) for H2O2 generation and HMF oxidation into DFF. The research also demonstrated the importance of improving the photostability of ZnIn2S4 through sulfur substitution, which sheds new light on biomass valorization via photorefinery.