N-doped semi-graphitic C loaded with metallic Co: synthesis parameters and catalytic selective reduction of p-nitrophenol

p-Nitrophenol (PNP) is an important pesticide intermediate, and is also a water pollutant that is extremely harmful to personal health. It can be converted to p-aminophenol (PAP) through selective catalytic hydrogenation reduction. This work reports that the Co/CN-x (x is the pyrolysis temperature) catalysts derived from the precursor Co-ZIF-9 could catalyze highly selective hydrogenation of PNP with H₂ to PAP. The obtained N-doped semi-graphitic C loaded with a metallic Co (Co/CN) catalyst had an extraordinary morphology and exhibited excellent catalytic hydrogenation activity. The size effect of Co NPs dispersed on nitrogen-carbon materials played a critical role in promoting the reaction efficiency. It was found that the conversion of PNP reached 100% and the selectivity of PAP was 98.5% over Co/CN-350 under mild reaction conditions. In addition, Co/CN-x catalysts also displayed excellent substrate tolerance and good recyclability with a catalytic performance remaining between 97.4% and 100% with 14 recycles. This work not only provides a new idea for the application of environment-friendly Co-based catalysts, but also opens up a suitable catalytic route for selective hydrogenation of nitrophenols.