Abstract
Selective traditional oxidation of toluene to high-value products like benzyl alcohol, benzaldehyde, and benzoic acid faces significant challenges due to high dissociation energy requirements, harsh reaction conditions, and complex product distributions. While photocatalysis using O(2) as an oxidant offers a green alternative, developing efficient and durable photocatalysts for selective oxidation in both batch and flow systems remains challenging. Here, sulfur-doped polymeric carbon nitride (S-CN) is demonstrated as a versatile photocatalyst for selective toluene oxidation, applicable in both powder form and as binder-free panels across various reactor configurations and solvents. Tuning S monomer content within supramolecular assemblies that serve as S-CN precursors, allows enhanced light absorption, optimized band positions, high specific surface area, and tailored structural properties of the ensuing catalysts. The optimized photocatalyst achieves high product selectivity, yielding ∼72% benzaldehyde and ∼26% benzoic acid after 24 h. Mechanistic studies confirm the concurrent oxidation and reduction reactions occurring and the roles of O(2) (·) (-) and (1)O(2). Extended reaction time (48 h) enables selective benzoic acid production (73.4%) with minimal benzaldehyde formation (<1%), demonstrating excellent product control.