In situ-formed cobalt nanoparticles embedded within carbonaceous matrix as highly efficient and selective catalysts for the hydrogenation of nitroarenes

Abstract

Inhibiting the side reactions meanwhile promoting the hydrogenation of aromatic nitro compounds are the target for the production of functional amines. In this work, an easy-to-prepare heterogeneous catalyst with multilayered graphitic shells was successfully synthesized and applied. First of all, the structural features of catalyst reveal two possible catalytic mechanisms; in simple terms, 1) the metallic nanoparticles are covered with thin carbon layers with small cracks, where H2 can be diffused through and activated for the hydrogenation, and 2) the outer graphitic shell can be activated by the electronic interaction between inner metallic nanoparticles and outer graphene layer. Subsequently, the catalytic properties were tested in the hydrogenation of nitroarenes by a series of reaction conditions, hydrogen sources and substrates, and most of the nitro aromatics with functional groups were well tolerated in an excellent yield even under very mild industrially viable and scalable conditions. More surprisingly, this catalyst preformed highly selective hydrogenation on –NO2 and can further catalyze N-methylation for various tertiary amines by tandem reaction; not only that, a slight loss of catalytic activity was observed after recycling up to eight times, suggesting a potential routs to produce functional amines in scale-up application.