Synergetic Effect of Heterojunction and Sulfur Vacancy on ZnIn2S4/CeO2 to Enhance the Photocatalytic Performance of 5-Hydroxymethylfurfural into 2,5-Diformylfuran

The efficient separation of photocarriers and facile generation of superoxide radicals are crucial for enhancing the performance of photocatalysts in the selectively photo-oxidizing 5-hydroxymethylfurfural (HMF) into 2,5-diformylfuran (DFF). Herein, a ZnIn₂S₄/CeO₂ composite with S-scheme heterojunction and sulfur vacancies (S_V) is successfully developed through a one-step hydrothermal method. The optimal catalyst (S_V-ZnIn₂S₄/CeO₂) exhibits excellent catalytic activity with 100% conversion of HMF and 96.1% selectivity of DFF in 80 min under ambient conditions, the production rate of DFF is up to 952.6 µmol g⁻¹ h⁻¹. Intriguingly, the performance remains significant even when the concentration of HMF is increased from 8 to 100 mм. Experimental and theoretical investigations discover that the synergistic effect of S-scheme heterojunction and sulfur vacancies contribute to the separation of photocarriers and the activation of oxygen, which facilitate the generation of superoxide radicals, thus boosting the catalytic oxidation reactions.