Directed Hole Localization Stabilizing Interfacial Sulfur Species to Boost α‐C–H Activation for Selective Biomass Photo‐oxidation

The selective photocatalytic oxidation is one of the versatile routes for biomass valorization, while α‐C–H bond cleavage is typically limited by uncontrolled hole migration and poor stability of active free radicals. Herein, we showcase the integration of interlayer polarization modulation and interface engineering for directional C–H activation. As a proof of concept, phosphorus (P) incorporation amplifies the charge density gradient between [ZnS 4 ] and [InS 6 ] layers of P‐doped ZnIn 2 S 4 (P x ‐ZIS), anchoring a robust polarization electric field. In‐situ characterization and theoretical calculations reveal that the enhanced polarization electric field significantly improves carrier separation efficiency by spatially separating electron–hole pairs. Meanwhile, driving the oriented localization of holes to interfacial S sites in the Zn‐S layer stabilizes the generated sulfur anion radicals (S −· ). This not only promotes precise electron transfer from C–H bonds to P x ‐ZIS, enhancing α‐C–H adsorption/activation, but also reduces the product desorption barrier, associated with improved selectivity. The developed P 1 ‐ZIS can catalyze the partial oxidation of bio‐based 5‐hydroxymethylfurfural to exclusively afford 2,5‐diformylfuran with 90% yield under visible light at 25 °C, outperforming state‐of‐the‐art photocatalytic systems. This work establishes a new paradigm of combining polarization field and interface engineering for merging selective C–H activation and in‐situ transformation of biomass feedstock.