Protein-assisted synthesis of zeolite-supported pseudo-single-atom cobalt catalyst for nitrobenzene hydrogenation

A novel pseudo-single-atom cobalt catalyst based on a hollow zeolite microsphere (HZM) constructed by MWW nanosheets was prepared with the aid of bovine serum albumin (BSA). BSA was adsorbed on the external surface of nanosheets, forming a protein coating which prevented cobalt ions getting into micropores of HZM and at the same time induced their implantation on the outer surface through specific ion-protein interaction. The cobalt ions on BSA layer were highly dispersive in that one BSA tended to bind no more than one cobalt ion in a specific region, which constituted the basis of single-atom. Cobalt ions were reduced and trapped in the N-doped carbon layer derived from BSA coating during pyrolysis, obtaining the pseudo-single-atom cobalt catalyst (Co@CN@HZM). Co@CN@HZM exhibited high catalytic efficiency and favorable cycle stability in the reaction from nitrobenzene to aniline. The excellent performance of the catalyst mainly benefited from the highly exposed active sites on the outer surface, the hierarchical porous structure facilitating diffusion, and the oscillating effect of substrate in the cavity of microsphere. This work proposed a facile strategy for preparing single-atom or pseudo-single-atom materials with metal atom uniformly dispersed on the outer surface of zeolites or other similar supports.