Magnetic N-doped Co–carbon composites derived from metal organic frameworks as highly efficient catalysts for p-nitrophenol reduction reaction

Abstract

Magnetic nitrogenous cobalt–carbon composites were synthesized via calcination of N-ZIF-67, where metal and N atoms were introduced into the conductive carbon matrix formed during carbonization of N-ZIF-67, and were applied, as catalysts, in the reduction reaction of p-nitrophenol, assisted by NaBH₄. Characterization of the prepared composites was carefully performed using SEM, TEM, XRD, SQUID magnetometric analysis, XPS and nitrogen adsorption/desorption measurements. Compared to Co@C, which was similarly prepared, the N-Co@C catalyst exhibits much better catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol. The pseudo-first-order rate constant for the N-Co@C catalyst is 4.47 times greater than that for the Co@C catalyst, and its stability shows little change after five reaction cycles. The superior catalytic properties of the N-Co@C catalyst are due to the presence of N moieties. Leaching out the cobalt cores was induced using FeCl₃ and HCl to see what the active centers were. The results show that the majority of the catalytic activity is associated with the metal cores.