Oxygen Vacancy‐Rich S‐Scheme Heterojunction Photocatalyst With Enhanced Interfacial Charge Transfer for Round‐the‐Clock Formaldehyde Degradation

Graphitic carbon nitride (g‐C ₃ N ₄ ) holds great promise for photocatalytic formaldehyde removal, yet its efficiency is fundamentally restricted by severe carrier recombination and sluggish charge transport. To address these intrinsic bottlenecks, a dual‐functional strategy is devised that couples interlayer‐expanded porous nanosheets with an oxygen vacancy‐rich S‐scheme heterojunction, thereby reinforcing the built‐in electric field and enabling long‐afterglow‐assisted charge separation. As a result, the optimized CS2.5 heterostructure achieved 92% FA removal with a rate of 1.72 ppm g ⁻¹  min ⁻¹ , representing nearly an order‐of‐magnitude enhancement over bulk g‐C ₃ N ₄ . Beyond the improved charge dynamics, the heterojunction interface promotes in situ oxygen vacancy formation, which serves as electron reservoirs to sustain afterglow‐driven catalysis. This defect‐engineered S‐scheme architecture exemplifies a generalizable approach for precise modulation of carrier behavior and the realization of sustained photocatalytic systems.