The built-in electric field in fragmented g-C3N4@ZnIn2S4 composite boosts the generation of superoxide radicals for highly selective photocatalytic toluene oxidation

The sp³ C-H bond in hydrocarbons is a ubiquitous chemical bond found in organic compounds. Due to its inherent inertness, direct chemical conversion under mild conditions is significantly restricted. In this study, we have designed and synthesized a Z-type fragmented g-C₃N₄@ZnIn₂S₄ heterojunction photocatalyst with enhanced visible light response, achieving the oxidation of inert sp³ C-H bonds under mild conditions. During the photocatalytic selective oxidation of toluene, the synthesized catalyst demonstrated a 10.2 mmol g⁻¹ h⁻¹ conversion rate of toluene, with a selectivity for benzaldehyde products reaching up to 80 %. Control experiments and characterization analyses revealed that the formation of the Z-type heterojunction facilitated the establishment of an internal electric field, thereby enhancing charge separation and migration efficiency. This promoted the generation of superoxide radicals (·O₂^-), enabling efficient transformation of toluene. This research offers new insights into the application of Z-type heterojunctions and the activation of C-H bonds.