Acid–Base Matching at Kaolin‐Regulated Interfaces for Efficient Photocatalytic Degradation of Phenol

Kaolin is typically regarded as a structural support in composite photocatalysts, where its function is mainly attributed to improved dispersion, suppressed aggregation, and enhanced charge separation, while its interfacial chemical role has rarely been explicitly examined. Here, we construct ZnO/kaolin and TiO 2 /kaolin composites and use phenol photodegradation as a probe reaction to demonstrate that kaolin acts as an interfacial platform for tuning the Lewis acid–base properties of metal oxides. Despite comparable light absorption and charge‐carrier dynamics, interfacial electron redistribution in ZnO/kaolin renders Zn 2+ electron‐deficient, strengthening its Lewis acidity, promoting water dissociation, and enriching surface hydroxyl groups. This increases the in situ flux of hydroxyl radicals (•OH) and enables coordination between Zn 2+ sites and the phenolic hydroxyl group, thereby accelerating surface reaction kinetics and leading to a markedly higher degradation efficiency (95.9%). In contrast, the weak electronic coupling at the TiO 2 /kaolin interface fails to regulate acid–base sites and hydroxyl density, resulting in limited radical generation and lower activity (63.1%). These findings identify kaolin as an interfacial acid–base regulator that enables reactive oxygen species flux engineering, providing a molecular‐level strategy for rational photocatalyst design in advanced oxidation processes.