Photo-enzyme-coupled catalysis for selective oxidation of 2,5-diformylfuran into 2,5-furandicarboxylic acid†

Abstract

The transformation of 2,5-diformylfuran (DFF) into renewable biomass-derived 2,5-furandicarboxylic acid (FDCA) is an attractive reaction. In this study, a novel photo-enzymatic catalysis system was established for selective oxidation of DFF into FDCA under mild conditions and through a one-pot process, in which 2-ethylanthraquinone served as the homogeneous photocatalyst for in situ H₂O₂ production under visible light irradiation, while H₂O₂ served as the oxidant for the organic peracid-assisted oxidation of DFF into FDCA by commercial lipase (Lipozyme 435). Results indicated that the constitution of the buffering system evidently influenced both photocatalyst and lipase activities in the coupling system, which further affected the kinetics of the tandem reactions and FDCA yield. Under optimized conditions (2 mg mL⁻¹ of 2-ethylanthraquinone, 3 mg mL⁻¹ of lipase, 7 W and λ > 420 nm of the light source, and tert-butanol/ethanol ratio of 9 : 1 (v : v)), 84.14% ± 4.68% of FDCA yield with complete DFF conversion was realized. Mechanism investigation using molecular docking simulation indicated that H₂O₂ produced from the light reaction was consumed by lipase to generate peracetic acid from ethyl acetate that drove the selective oxidation of aldehyde groups in the DFF molecule. The novel visible-light-driven photo-enzyme coupling system successfully addressed the challenges associated with manually adding, storing, and transporting H₂O₂ in conventional DFF oxidation, thus showing promise in valorization of a broader range of aldehyde group-containing biomass-derived molecules into renewable chemicals.