Selective Aerobic Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Diformylfuran or 2‐Formyl‐5‐furancarboxylic Acid in Water by using MgO⋅CeO2 Mixed Oxides as Catalysts

Mixed oxides based on MgO⋅CeO2 were used as efficient catalysts in the aerobic oxidation of 5‐hydroxymethylfurfural (5‐HMF) to afford, with very high selectivity, either 2,5‐diformylfuran (DFF, 99 %) or 2‐formyl‐5‐furancarboxylic acid (FFCA, 90 %), depending on the reaction conditions. 5‐Hydroxymethyl‐2‐furancarboxylic acid (HMFCA, 57–90 %) was formed only at low concentration of 5‐HMF (99 %) and reusable. The use of mixed oxides allows tuning of the basicity of the catalysts, avoiding the need for external bases for efficient and selective conversion of 5‐HMF and waste formation, resulting in an environmentally friendly, sustainable process. Mixology: By using a tunable mixed oxide, such as MgO⋅CeO2, selective and quantitative oxidation of 5‐hydroxymethylfurfural (5‐HMF) to 2,5‐diformylfuran (DFF) or 2‐formyl‐5‐furancarboxylic acid (FFCA) is carried out in water in the presence of O2 as oxidant. Interestingly, the oxidation of the aldehyde moiety, which brings about the formation of 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA), can be suppressed.