Crystal Facet-Engineered Bi2WO6-BiOCl S-Scheme Heterojunction Synergized with Surface Hydroxyls Enables Complete Photocatalytic Mineralization of Toluene

The complete mineralization of aromatic VOCs via photocatalysis remains a grand challenge, limited by severe photogenerated carrier recombination and the easy formation of toxic refractory phenolic intermediates. Here, we demonstrate a solvent-mediated crystal facet engineering strategy to construct a Bi 2 WO 6 -BiOCl S-scheme heterojunction with oriented exposure of high-activity facets and abundant surface hydroxyl sites. The facet-tailored heterojunction achieves efficient spatial separation of photogenerated carriers via a strong built-in electric field, while retaining the strong redox capacity to generate abundant reactive oxygen species. The optimal catalyst delivers over 95% gaseous toluene removal and 94.9% mineralization efficiency within 1   h irradiation, with 99.7% of removed toluene converted to CO 2 , exceeding the aqueous-synthesized control, pure-phase counterparts, and most reported bismuth-based photocatalysts. In-situ diffuse reflectance infrared Fourier transform spectroscopy combined with theoretical calculations reveals that facet-induced surface hydroxyl sites act as specific adsorption and activation centers for toluene molecules, steering the degradation toward a benign benzyl alcohol-benzaldehyde-benzoic acid pathway and inhibiting the generation of toxic phenolic byproducts. This work clarifies the critical role of crystal facet engineering in coordinating heterojunction charge transfer and surface reaction pathway modulation, providing a new avenue for designing high-performance photocatalysts for the complete mineralization of aromatic VOCs.