Oxygen-vacancy-rich MnO supported RuO for efficient base-free oxidation of 5-hydroxymethylfurfural and 5-methoxymethylfurfural to 2,5-furandicarboxylic acid

2,5-Furandicarboxylic acid (FDCA) is a promising biomass-derived polymeric monomer that serves as an attractive alternative to terephthalic acid derived from fossil resources. However, the green and efficient production of FDCA through the oxidation of 5-hydroxymethylfurfural (HMF) and its derivatives is still rudimentary under base-free conditions. In this work, oxygen-vacancy-rich MnOx was prepared and displayed a strong adsorption and anchoring ability to Ru species that mainly exposed the (210) plane of RuO2, bringing about highly dispersed and active interfacial Ru-O-Mn structures. Experimental results and density functional theory calculations confirm that these above features greatly facilitate the adsorption/activation of oxygen and the dehydrogenation-oxidation of HMF/5-methoxymethylfurfural (MMF), which enables an efficient FDCA production under base-free and mild conditions. Notably, a desirable FDCA yield of 86.56% was still obtained from concentrated HMF (10 wt%) under base-free conditions over oxygen-vacancy-rich MnOx supported RuOx (1.0 MPa O2, 120 °C, 6 h). This work delineates a facile catalyst preparation strategy for HMF/MMF oxidation, and might open a new avenue for the green synthesis of FDCA under base-free conditions.