Successive Free-Radical C(sp2)-C(sp2) Coupling Reactions to Form Graphene

Abstract

Graphene is of great interest because of its exciting properties and potential applications, but its production on a large-scale still presents considerable challenges. Herein, we report the synthesis of predominately few-layer graphene, due to π-π stacking, and single-layer graphene from reaction between hexabromobenzene and Na metal, followed by annealing to improve crystallinity. The reaction proceeds via a free-radical C(sp2)-C(sp2) coupling mechanism, which is supported by theoretical calculations. The graphene can host unpaired spin electrons, leading to a short acquisition time for a solid-state nuclear magnetic resonance 13C spectrum from unlabeled graphene, which is ascribed to the very short spin-lattice relaxation time. High catalytic activity for transforming amine to imine with a conversion of >99% and a yield of ∼97% is demonstrated, and high electronic conductivity of ∼105 S·m−1 is found by terahertz spectroscopy. The reaction delivers a method for synthesizing graphene with a high spin concentration from perbrominated benzene molecules by using an active metallic agent, such as Na, Li, or Mg.