Probing the intrinsic active sites of modified graphene oxide for aerobic benzylic alcohol oxidation

The graphene-based materials, particularly graphene oxide (GO) with rich oxygenated groups, exhibit high catalytic performance in various metal-free oxidation reactions. However, the intrinsic active site is still unclear, which greatly retards to further develop advanced catalysts. Here, the modified graphene oxide (abGO) was synthesized by sequential base and acid treatment and employed in the aerobic oxidation of benzyl alcohol to benzaldehyde. This novel catalyst displayed much higher activity, selectivity and stability than that of conventional GO. 93.1% conversion and 100% selectivity were achieved over abGO. More importantly, it is shown that the yield of benzaldehyde is linearly proportional to the content of surface phenol hydroxyl groups. Experimentally observed reactivity trends, structure-behavior correlation, molecule mimicking and characterization results strongly confirm that the surface phenol hydroxyl groups are the intrinsic active sites.