Dual Vacancy Engineering in Alloyed Ga-Zn-Cu-Se Quantum Dots for Photocatalytic 5-Hydroxymethylfurfural to 2,5-Diformylfuran Conversion.

Highly -active/-selective photocatalytic biomass conversion is of great importance for achieving remarkable solar-to-chemical conversion. However, serious challenges, e.g., limited photon utilization, high charge recombination, and sluggish/uncontrolled reaction kinetics, remain for further development in this area. Herein, a dual-vacancy-engineering strategy is employed to regulate the Ga-Zn co-doped Ga-Zn-Cu-Se (GZC) quantum dots (QDs) by a cation exchange route utilizing the CuSe template. The optimized GZC QDs exhibit excellent photocatalytic performances for the selective oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-diformylfuran (DFF), with 89% HMF conversion and 91% DFF selectivity. Advanced ex situ/in situ characterizations, together with theoretical calculations, reveal the origins of the excellent performance: i) Zn doping enhances charge carrier mobility, thereby promoting the HMF-to-DFF conversion rate; ii) Ga doping introduces intermediate states in electronic structure, facilitating better charge separation/transfer; iii) Ga/Zn co-introduction results in formation of Se/Cu vacancies, which play a critical role in charge separation and reactive oxygen species generation. Overall, the research exhibits a rational strategy for designing vacancy-engineered photocatalysts, offering a promising approach for selective biomass conversion.