Photocatalytic benzylic and aliphatic sp³ C–H activation and CO₂ carboxylation over Z-scheme CdS@g-C₃N₄

Achieving heterogeneous photocatalytic activation of sp³ C–H bonds and carboxylation of CO₂ to produce arylacetic acids and alkyl carboxylic acids with increased carbon chains is a highly significant and demanding research endeavor. In this work, a new method for synthesizing redox centers spatially separated Z-scheme CdS@graphitic carbon nitride (g-C₃N₄) was developed, aiming to achieve photocatalytic benzylic and aliphatic sp³ C–H activation as well as CO₂ carboxylation without sacrificial agent. Notably, both benzylic and aliphatic sp³ C–H activation together with CO₂ carboxylation were achieved in heterogeneous photocatalytic system, resulting in the production of carboxylic acids with increased carbon chains under mild conditions. Various methylbenzene derivatives and cycloalkanes were employed to synthesize carbon-chain increased acids via a process involving K₃PO₄-assisted photogenerated holes activation for benzyl radical generation, photoinduced CO₂ reduction, as well as solvent-assisted chemoselective carboxylation. Various characterizations and density functional theory (DFT) results revealed that Z-scheme CdS@g-C₃N₄ not just significantly enhanced separation of charges and accumulation of photoinduced electrons on g-C₃N₄ but also facilitated adsorption along with activation of CO₂. This research provided novel heterogeneous photocatalytic approach to produce carbon chains increased carboxylic acids via sp³ C–H activation and CO₂ carboxylation.