Synthesis of Mesoporous γ-Alumina-Supported Co-Based Catalysts and Their Catalytic Performance for Chemoselective Reduction of Nitroarenes.

Mesoporous γ-alumina (γ-MA)-supported cobalt oxides (Co3O4) with large surface areas and narrow pore size distributions were first prepared through one-pot hydrolysis of metal nitrates. The obtained Co3O4/γ-MA materials were impregnated with a water-ethanol solution of 1,10-phenanthroline, followed by treatment at 700 °C in N2 atmosphere, generating Co-NC/γ-MA catalysts containing N-doped graphitic carbon (NC). The Co-NC/γ-MA catalysts maintained the mesoporous structure of γ-MA, and Co3O4 was reduced to metallic Co nanoparticles highly dispersed in the γ-MA frameworks. Metallic Co species had a strong interaction with NC in the matrices, avoiding the surface oxidation of Co particles. The Co-NC/γ-MA catalysts exhibited superior catalytic activity and quantitatively reduced a variety of functionalized nitroarenes to the corresponding arylamines with hydrazine hydrate in ethanol at near room temperature, affording yields of >99%. The recycling test of 2-chloronitrobenzene as a model reaction showed no detectable change in catalyst performance after 10 cycle reactions.