Facet‐Engineered Cds with Cd Vacancies for High‐Efficiency Photocatalytic Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Diformylfuran

The photocatalytic oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐diformylfuran (DFF) is a promising process with significant implications for sustainable energy and environmental applications. However, achieving highly selective DFF production from HMF remains a challenging task, particularly due to the dependency of molecular O 2 activation on the composition and exposed facets of nanomaterials. This study investigates the impact of different preferential facets of hydrothermally synthesized cadmium sulfide (CdS) morphologies—including hollow spheres, nanorods, and flower‐like structures—on the photocatalytic oxidation of HMF to DFF. The findings reveal that the preferential CdS (002) facet and Cd vacancies in the hollow sphere morphology significantly enhance photocatalytic activity, achieving 68% HMF conversion and 89% selectivity for DFF production within 12 h of reaction time. This work highlights the critical role of material composition and facet orientation in optimizing photocatalytic processes for selective oxidation reactions, offering a potential strategy for the design of advanced photocatalysts in sustainable chemical production.