Oxidative Esterification of 5-Hydroxymethylfurfural with an N-doped Carbon-supported CoCu Bimetallic Catalyst

The direct fabrication of furan-2,5-dimethylcarboxylate (FDMC), a promising renewable monomer, from biomass-derived 5-hydroxymethylfurfural (HMF) is a cutting-edge process. In this contribution, an elaborately designed N-doped carbon-supported CoCu bimetallic catalyst (Co_x Cu_y -NC; x/y=9:1, 7:3, 4:6, which represents the designed molar ratio of Co and Cu in the catalyst), which could offer a desirable FDMC yield of 95 % under mild and base-free conditions (Co₇ Cu₃ -NC, 2 bar O₂ , 80 °C, 4 h) is described for the oxidative esterification of HMF. Notably, an FDMC formation rate of 6.1 mol_FDMC  mol_Co ^-1  h^-1 was achieved over Co₇ Cu₃ -NC, which represents the highest catalytic efficiency so far among Co-based catalytic systems. It has been demonstrated that Cu-doping in Co₇ Cu₃ -NC catalyst brings about more active sites (Co-N_x species) with stronger molecular oxygen activation ability. The increase of surface N content of Co₇ Cu₃ -NC also improves basicity of the catalyst, which favors the hydrogen abstraction process during the HMF oxidative esterification reaction. These findings may pave an efficient and green way for the synthesis of sustainable bio-based polymer monomers.