Hierarchically porous carbon confined cobalt nanoparticles for highly efficient oxidative esterification of 5-hydroxymethylfurfural

Herein, we report a controllable and versatile strategy for the synthesis of highly dispersed Co nanoparticles embedded in open-channel hierarchically porous N/O-doped carbon skeleton. Moreover, the pore sizes of the hierarchical structures can be easily tuned by adjusting the size of precursors. The as-obtained Co@NC-2ST exhibits unprecedented activity and selectivity in the oxidative esterification of 5-hydroxymethylfurfural (HMF) to dimethyl furan-2,5-dicarboxylate under base-free and atmospheric conditions. In particular, the achieved turnover frequency value is an order of magnitude higher than that of the state-of-art heterogeneous catalysts reported to date. A combination of experimental and density function theory studies reveals that the unique features of Co@NC-2ST enable a novel reaction route, that is, the  CHO group of HMF is preferentially esterified instead of the  OH group. This can be attributed to the nucleophilic addition reaction caused by the attack of methoxy anion on the  CHO group of HMF.