Synergic catalytic effect of Co nanoparticles and graphitic N on carbon aerogels towards transfer hydrogenation of nitrobenzene

Abstract

In this study, cobalt-nanoparticles-decorated N-doped carbon aerogels (CoZn@NCA) with well-developed porosity are fabricated through a straightforward sol-gel technique followed by pyrolysis. Chitosan serves as the carbon and nitrogen precursor in the synthesis process, while zinc nitrate acts as a barrier agent promoting the dispersion of cobalt nanoparticles. The CoZn@NCA catalyst demonstrates high activity in the transfer hydrogenation of nitrobenzene with hydrazine hydrate (N₂H₄·H₂O) being used as the hydrogen source. The CoZn@NCA catalyst calcined at 700 °C shows the highest Co⁰ and graphitic nitrogen content, where both of them synergistically contribute to its superior activity. The CoZn@NCA catalyst delivers an impressive catalytic activity in the conversion of nitrobenzene at 99.78 % and amine selectivity of 99.59 % at 60 °C with 4 equivalents of N₂H₄·H₂O in hexane. A reaction pathway is proposed whereby the transfer hydrogenation of nitrobenzene catalyzed by CoZn@NCA via the indirect pathway involving azobenzene and azoxybenzene as the reaction intermediates.