Active cobalt nanoparticles confined in porous N-doped carbon shell for selective hydrogenation of nitroarenes

Abstract

Selective hydrogenation is still challenging due to the trade-off between activity and selectivity of the catalyst. Hollow carbon shell confining cobalt nanoparticles is a competitive candidate catalyst, of which the structure and composition should be finely tailored for selective hydrogenation. In this work, Co in ZIF-67 is partially replaced by Zn and coated by polydopamine followed by pyrolysis to realize synergistic Zn regulation and N doping of shell-shaped carbon-cobalt catalyst. By changing Co/Zn ratio, the state of cobalt particles and the structure and composition of the N-doped carbon shell are effectively tuned. When Co/Zn ratio was 1:1, the as-prepared catalyst exhibited the best performance for selective nitro hydrogenation. H2 is dissociated on cobalt nanoparticles to generate active H radicals, which can be exchanged with H atoms of isopropanol as the solvent for facilitating hydrogenation. Selective adsorption of nitro group occurs on the N-doped carbon shell and the confined cobalt nanoparticles. The catalyst possesses good stability, which still maintained the original performance after 5 cycles.