Aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Co/Mn-lignin coordination complexes-derived catalysts

Deriving more valuable products from renewable lignocellulosic biomass is attractive but still remains major challenges, the insufficient lignin valorization is considered as one of the main obstacles. Here, we report a novel catalyst comprised of cobalt nanoparticles (NPs) encapsulated in graphitic carbon tailored with manganese and nitrogen heteroatoms (Co-Mn/N@C), fabricated by pyrolyzing a mixture of Co/Mn-lignin complex and dicyandiamide. The as-synthesized Co-Mn/N@C catalyst exhibits excellent activity and recyclability for oxidizing biomass-derived 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) in aqueous system using O-2 as oxidant. The structure-performance relations of the catalyst are investigated, suggesting that Mn/N-doped carbon can activate the reactivity of Co NPs for HMF oxidation by tuning the electronic structure of embedded metal NPs. Additionally, isotopic labelling experiments reveal the role of water and O-2 for FDCA production using Co-Mn/N@C as catalyst. This work not only demonstrates the integrated biorefinery strategy, but also provides a new approach for sustainable, low-cost heterogenous catalysts preparation.