Bifunctional Graphene-Based Metal Free Catalysts for Oxidative Coupling of Amines.

Graphene oxide (GO), an emerging material ornamented by oxygen-containing functional groups, is becoming a promising alternative for various applications. The piranha solution treatment of GO can increase oxygen-containing functional groups and make improved graphene oxide (IGO), as well as restore the functional groups lost due to the reaction. It is found that GO can oxidize the amine to the corresponding imine in the absence of oxygen and catalyst, and the obtained IGO even shows higher activity. In addition, the piranha solution can partially restore the reactivity of GO after the reaction. The different role of oxygen-containing functional groups in the oxidative coupling reaction is investigated. A possible reaction mechanism for the oxidation of benzylamine to N-benzylidene benzylamine is also proposed.