Quantitative Catalytic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid by TEMPO in a Single Aqueous Phase under Mild Conditions

2,5-Furandicarboxylic acid (FDCA) has been extensively verified as a biobased aromatic ring platform compound. The development of mild and efficient novel oxidation technologies is important for FDCA preparation technologies. In this study, the efficient oxidation of 5-hydroxymethylfurfural (HMF) to produce FDCA by the TEMPO/NaClO/KBr single-phase aqueous catalytic oxidation system was systematically investigated, and the mechanism was analyzed in detail. Under the optimal reaction conditions, TEMPO as the main catalyst directly catalyzed the oxidation of HMF to FDCA, and the HMF conversion and FDCA yield both reached 100%. The oxidant NaClO could achieve a quantitative reaction (NaClO/HMF = 3:1(mol)). In addition, the reaction was conducted at mild room temperature and innovatively utilized a single aqueous system as the reaction solvent. This establishes a new method for the oxidative preparation of FDCA with the potential for technical scale-up.