Activating Lattice Oxygen in Amorphous MnO2 Nanostructure for Efficiently Selective Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid

Aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) offers an appealing way to transform the biomass feedstock into chemical commodities but suffers from low efficiency and selectivity due to the formation of 5-formyl-2-furancarboxylic acid (FFCA) byproduct. Herein, we demonstrated that an amorphous MnO2 (amor-MnO2) nanostructure having a disordered lattice structure can carry OL of high reactivity for catalyzing the aerobic oxidation of HMF to prepare FDCA efficiently and selectively. The FDCA formation rate of amor-MnO2 reaches up to 1307 μmolFDCA gcat–1 h–1, about 8.2 times that of crystalline MnO2 (cry-MnO2) (160 μmolFDCA gcat–1 h–1) and surpassing many other state-of-the-art Mn-based catalysts. Kinetic studies reveal that the amor-MnO2 nanostructure can efficiently convert the low-concentration FFCA intermediate into FDCA, which helps tackle the rate-determining step in the HMF → FFCA → FDCA oxidation process. Density functional theory calculations and experimental measurements demonstrate that amor-MnO2 delivers superior lattice oxygen (OL) activity and stronger O2 adsorption capability when compared with the crystalline counterpart. The findings showcase the use of amorphous materials as advanced catalysts for achieving sustainable chemistry industry.