Ball-Milled Co–N–C Nanocomposite for Benzylic C–H Bond Oxidation: a Facile, Practical, and Recyclable Catalyst under Neat Conditions and Atmospheric Pressure Oxygen

A novel Co–N–C nanocomposite catalyst was prepared using a mechanical ball-milling method from melamine and Co­(NO3)2, and no high-temperature calcination procedures were required. The superior nanocomposite catalyst shows excellent catalytic activity in the selective liquid-phase oxidation of benzylic C–H bonds with atmospheric pressure oxygen as an oxidant under solvent-free conditions. With 0.5 mol % of the Co–N–C nanocomposite catalyst, up to a 95% conversion and 98% selectivity are achieved in the oxidation of ethylbenzene to acetophenone. Furthermore, the catalyst shows good recyclability and can be simply recovered by filtration and reused several times without a significant loss in catalytic activity.