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 (such as dehalogenation) while promoting both/transfer hydrogenation are the main target for the production of functional anilines from nitroarenes; consequently, the preparation of an ideal catalyst to improve reaction selectivity stays as the fundamental direction for this field. In this work, we provided an easy-to-prepared heterogeneous catalyst with multilayered graphene shells where cobalt nanoparticles were encapsulated inside and distributed uniformly. This as-prepared catalysts were fabricated via one-pot pyrolysis by using mixture of citrate acid and cobalt acetate as C source and Co source, respectively. First of all, structural features of catalyst were characterized by a series of analytic techniques involving XPS, SEM/EDS, TEM as well as elemental mapping, to reveal its unique properties in relation to the catalytic mechanisms; in simple terms, the outer graphitic shell could be activated by the electronic interaction between the inner metallic nanoparticles and the outer graphene layer. Subsequently, the catalytic performance was tested in hydrogenation of nitrobenezene by using H2 as hydrogen source, so as to optimize the preparation process as well as the reaction conditions. Other nitro aromatics with functional groups such as halogen atoms, methyl or hydroxyl were also tolerated under very mild industrially viable and scalable conditions (60 °C, 2 h, and 2 MPa H2). More surprisingly, this catalyst could still exhibit excellent yields over 96 % in gram-scale test for the selected substrates, and could also be easily separated from the aqueous system due to its magnetic properties. The determined yields of target products were not decreased even after eight cycles, suggesting a potential for future industrial application in the selective hydrogenation of nitroarenes to the corresponding amines.