Activating Lattice Oxygen in Amorphous MnO 2 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 MnO 2 (amor-MnO 2 ) nanostructure having a disordered lattice structure can carry O L of high reactivity for catalyzing the aerobic oxidation of HMF to prepare FDCA efficiently and selectively. The FDCA formation rate of amor-MnO 2 reaches up to 1307 μmol FDCA g cat –1 h –1, about 8.2 times that of crystalline MnO 2 (cry-MnO 2 ) (160 μmol FDCA g cat –1 h –1 ) and surpassing many other state-of-the-art Mn-based catalysts. Kinetic studies reveal that the amor-MnO 2 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-MnO 2 delivers superior lattice oxygen (O L ) activity and stronger O 2 adsorption capability when compared with the crystalline counterpart. The findings showcase the use of amorphous materials as advanced catalysts for achieving sustainable chemistry industry.