Magnetic cobalt nanoparticles embedded in hierarchically porous nitrogen-doped carbon frameworks for highly efficient and well-recyclable catalysis

Abstract

The utilization of metal–organic frameworks (MOFs) for constructing metal nanoparticles inside carbon frameworks offers great advantages for the rational design and fabrication of advanced catalysts. In this study, hierarchically porous nitrogen-doped carbon frameworks embedded with cobalt nanoparticles (Co@NC) were prepared by a MOF-engaged strategy using a well-defined rhombic dodecahedral cobalt-based zeolitic imidazolate framework-67 (ZIF-67-Co) as an effective precursor and template. The resulting Co@NC exhibited remarkable catalytic activity and excellent durability for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH₄ in an aqueous solution. It could reach nearly 100% conversion within 3 min, even when the amount of the catalyst used was as low as 0.02 mg. Moreover, after 17 successive cycles of reactions, it still retained large conversion efficiencies over 95%. The apparent rate constant for the catalytic reaction of 4-NP reduction was estimated to be 1.024 min⁻¹, which was superior to those of the previously reported transition metal nanoparticles and even compared favorably with that of the most active noble metal nanoparticles. In addition, such a novel Co@NC catalyst was also found to be highly active for catalytic degradation of rhodamine B (RhB) by NaBH₄ in an aqueous solution.