Efficient and recyclable bimetallic Co-Cu catalysts for selective hydrogenation of halogenated nitroarenes

Silica supported N-doped carbon layers encapsulating Co-Cu nanoparticles (Co1Cux@CN/SiO2) were prepared by a one-step impregnation of Co(NO3)(2)center dot 6H(2)O, Cu(NO3)(2)center dot 3H(2)O, urea and glucose, following in situ carbothermal reduction. Effects of Cu contents on the catalytic performance of the Co1Cux@CN/SiO2 catalysts were investigated for selective hydrogenation of p-chloronitrobenzene to p-chloroaniline. The Co1C0.30@CN/SiO2 with Cu/Co molar ratio of 0.30:1 presented much higher activity and stability than the monometallic Co@CN/SiO2 catalyst. The addition of Cu into Co1Cux@CN/SiO2 catalysts had favorable effects on the formation of highly active Co-N sites and N-doped carbon layer. The role of the N-doped carbon layer was to protect the Co from oxidation by air, and the Co1C0.30@CN/SiO2 could be reused for at least 12 cycles without decrease in catalytic efficiency. Mechanistic and in situ infrared studies revealed that the interaction effect between the Co and Cu atoms made the surface of Co highly electron rich, which decreased adsorption of halogen groups and resulting in the enhanced selectivity during chemoselective hydrogenation of halogenated nitroarenes for a wide scope of substrates. (C) 2021 Elsevier B.V. All rights reserved.