Core–Shell Structured Cobalt Sulfide/C. I. Pigment Yellow 53 Photocatalysts with Abundant Sulfur Vacancies for Efficient Photocatalytic Co‐Production of Xylonic Acid and CO

Abstract Photocatalytic biorefinery has been gaining increasing attention as a promising method for utilizing biomass and solar energy, yet it still faces the key challenge of designing stable, efficient, and cost‐effective photocatalysts. In this study, cobalt sulfide/ C. I. Pigment Yellow 53 composite photocatalysts (CoS/PY53‐CS x ) with a core–shell structure, which has abundant sulfur (S) vacancies, are developed using a simple hydrothermal method. The CoS nanocage with S vacancies not only offers numerous active sites but also enhances the light‐trapping performance of PY53. Moreover, the internal electric field within the core–shell CoS/PY53‐CS x further enhances charge separation/transfer efficiency while reducing electron transfer resistance, thereby boosting photocatalytic activity. Remarkably, 75.2% of xylonic acid and 22.8 µmol of CO from xylose are obtained using CoS/PY53‐CS 0.1 in an air atmosphere. Recycling experiments demonstrate that CoS/PY53‐CS 0.1 exhibits excellent recyclability due to the strong bonding force between the core and shell. In addition, electron spin resonance characterization combined with poisoning experiments suggests that h + and ·O 2 − serve as the main oxidation active species during this system. This work presents a simple and cost‐effective method for efficient photocatalytic biorefinery.