Ligand-engineered Ir nanozymes for catalytic conversion of molar level 5-hydroxymethylfurfural to 2, 5-furandicarboxylic acid in acidic condition

2, 5-furandicarboxylic acid (FDCA) is an eco-friendly polyester monomer that holds great promise for the production of biodegradable plastics. FDCA can be prepared by the oxidation of 5-hydroxymethylfurfural (HMF), but the transformation was usually achievable only in alkaline conditions, resulting in a millimolar level reaction and complicated product purification. In present work, a series of iridium nanozymes with an average size of 2 nm were synthesized by using tartaric acid (TA) or other structurally similar small molecular ligands as the stabilizing agents. The different ligands significantly affect the Ir 4f binding energy, with TA exhibiting superior electron donation effect to the Ir center, thus facilitates the electron transfer and the enhancement in enzymatic efficiency. In the presence of H 2 O 2 , the TA-Ir nanozymes can directly catalyze the conversion of molar level HMF to FDCA in acidic condition (pH 4), achieving 99.8% HMF conversion and ∼ 90% FDCA yield.