Enzyme-catalyzed selective oxidation of 5-hydroxymethylfurfural (HMF) and separation of HMF and 2,5-diformylfuran using deep eutectic solvents

Abstract
An enzyme toolbox was developed for the synthesis of 2,5-diformylfuran (DFF), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) with good yields from 5-hydroxymethylfurfural (HMF) via selective oxidation. In addition, a proof-of-concept based on deep eutectic solvents (DES) was provided for the efficient separation of HMF and DFF. The DFF purity was improved to 97% from 76% after extraction by choline-based DES.