Regulation of Pd single-atom coordination for enhanced photocatalytic oxidation of toluene to benzaldehyde

Photocatalytic oxidation represents an effective means of hydrocarbon valorization, but achieving high-selectivity intermediate products at high substrate conversion remains challenging. Here single-atom Pd–O catalytic sites with different coordination environments are synthesized. The Pd–O₃ coordinated single sites show the best catalytic performance for selective toluene oxidation, exhibiting a high benzaldehyde selectivity of 95% at 95% toluene conversion, and a benzaldehyde yield rate up to 12,000 μmol g⁻¹ h⁻¹, surpassing previously reported results. The Pd–O₃ catalytic sites serve as the location of photogenerated charge separation and C(sp³)–H bond activation. These sites can trap the photogenerated holes effectively to enhance the charge-separation efficiency, improving the yield rate by a factor of 2.9 relative to the Bi₂WO₆ support. Additionally, the coordination structure weakens benzaldehyde adsorption, reducing overoxidation and improving reaction selectivity. This work highlights the importance of single-atom site coordination in optimizing the activity and selectivity of photocatalytic oxidation reactions. (Figure presented.)