Efficient and reusable catalysis of benzylic C–H oxidation over layered [Co5(OH)6]4+ derivatives

Aerobic oxidation of benzylic C(sp3)-H bonds in a green and heterogeneous manner is a major target in organic catalysis. Herein, we report the synthesis of 3D coordination polymers containing [Co5(OH)6]4+ layers, affording reusable and efficient oxidation of ethylbenezene and tetralin by using O2 as the oxidant. Moreover, the cleavage of CoII-carboxylate bonding renders atomically thin cobaltate nanosheets and enhanced catalytic performance. This is one of the top catalytic performances for CoII-catalyzed benzylic C(sp3)-H oxidation (∼0.02 mol% Co and 76% conversion for nanosheets), ascribed to the exposed, accessible and coordinatively unsaturated CoII species.