Magnetic graphene oxide-anchored Ni/Cu nanoparticles with a Cu-rich surface for transfer hydrogenation of nitroaromatics

Abstract

• The Ni/Cu NPs with a Cu-rich surface were prepared by thermal decomposition. • Graphene oxide anchored Ni/Cu NPs to prepare magnetic Ni/Cu-GO catalyst. • Ni/Cu-GO with different composition for CTH of 2-methyl-5-nitrophenol were studied. • Ni 7 /Cu 3 -GO did not dehalogenate for CTH of halogen-containing nitroaromatics. The bimetallic nanoparticles compositing of Ni-rich core and Cu-rich shell (Ni/Cu NPs) were successfully synthesized by a liquid-phase thermal decomposition method. The content of copper and nickel in Ni/Cu NPs was controllable by adjusting the ratio of two metal precursors, copper formate (Cuf) and nickel acetate tetrahydrate (Ni(OAc) 2 ∙4H 2 O). Ni/Cu NPs were further anchored on graphene oxide (GO) to prepare a magnetic composite catalyst, called Ni/Cu-GO. The dispersibility of Ni/Cu NPs in solution was enhanced by GO anchoring to prevent the sintering and aggregation during the reaction process, thereby ensuring the catalytic and cycling performance of the catalyst. The catalytic transfer hydrogenation (CTH) reaction of nitroaromatics was investigated when ammonia borane was used as the hydrogen source. Cu dominated the main catalytic role in the reaction, while Ni played a synergistic role of catalysis and providing magnetic properties for separation. The Ni 7 /Cu 3 -GO catalyst exhibited the best catalytic performance with the conversion and yield of 99% and 96%, respectively, when 2-methyl-5-nitrophenol was used as the substrate. The Ni 7 /Cu 3 -GO catalyst also exhibited excellent cyclic catalytic performance with the 5-amino-2-methylphenol yield of above 90% after 6 cycles. In addition, the Ni 7 /Cu 3 -GO catalyst could be quickly recycled by magnetic separation. Moreover, the Ni 7 /Cu 3 -GO catalyst showed good catalytic performance for halogen-containing nitroaromatics without dehalogenation.