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

Abstract

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. The design of active sites in single-atom photocatalysts has a large impact on the catalytic reactivity. Here single-atom Pd–O catalytic sites are engineered by regulating their coordination environments. The Pd–O3 sites exhibit enhanced activity and selectivity for photocatalytic oxidation of toluene to benzaldehyde.