Gold Nanoparticle-Polydopamine-Reduced Graphene Oxide Ternary Nanocomposite as an Efficient Catalyst for Selective Oxidation of Benzylic C(sp3)-H Bonds Under Mild Conditions

A ternary nanocomposite comprising of Au nanoparticles (NPs), polydopamine, and reduced graphene oxide exhibits excellent activity and selectivity towards the oxidation of C-H bonds in benzylic hydrocarbons under mild conditions in the presence of N-hydroxyphthalimide. All the components in the nanocomposite play an important role in the effectiveness of the catalyst. Sufficient electron transfer from polydopamine to the Au NPs afforded a more negatively charged nanoparticle surface and was favorable for molecular oxygen activation, leading to C-H bond oxidation. The reaction followed a free radical pathway as shown by detailed mechanistic studies. Further, easy separation and excellent reusability without significant loss in activity over several iterations make the ternary nanocomposite an excellent heterogeneous catalyst for C-H oxidation reactions.