A La MnO2 catalyst exhibited excellent performance in aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Characterization of the samples revealed that the loose surface morphology and high oxygen species mobility facilitated the HMF oxidation reaction. H2O was verified as a good solvent for the formation of FDCA because of the facilitation of aldehyde group hydration to generate a carboxyl group on the HMF molecule. A 95.4% FDCA selectivity at 96.3% HMF conversion was achieved in H2O under mild conditions.