N-Doped carbon nanotube encapsulated cobalt for efficient oxidative esterification of 5-hydroxymethylfurfural

Cobalt nanoparticles embedded in graphitic nitrogen-rich carbon nanotubes (Co/GCN) were prepared with a facile method and employed as an efficient catalyst for oxidative esterification of 5-hydroxymethylfurfural (HMF). The introduction of N species to carbon benefits the synergistic effects between the Co nanoparticles and nitrogen-doped carbon nanotube substrate, which modify the surface chemical state of the Co/GCN catalyst and create abundant active sites to improve the HMF conversion. The Co/GCN catalyst carbonized at 800 °C exhibited the best catalytic performance with a 95.8% yield of furan-2,5-dimethylcarboxylate (FDMC) at 98.6% HMF conversion under mild reaction conditions. The effect of acid–base properties of the catalyst on the HMF conversion was investigated and the reaction mechanism of the HMF oxidative esterification was proposed.