Selective and green conversion of 5-HMF to FDCA via enzymatic (laccase) and transition metal (MnO2 and Co–Mn/AC) catalysis in an integrated system

Abstract

The sustainable synthesis of bio-based monomers from renewable biomass intermediates is a central goal in green chemistry and biorefinery innovation. This study introduces a synergistic catalytic–enzymatic strategy for the efficient and eco-friendly oxidation of 5-hydroxymethylfurfural (5-HMF) into 2,5-furandicarboxylic acid (FDCA), a key monomer for next-generation biodegradable plastics. The catalytic phase employed non-noble metal catalysts, MnO₂ and Co–Mn supported on activated carbon (Co–Mn/AC), under mild batch reaction conditions at 90 °C. Through systematic optimization, a metal-modified catalyst composition was developed to enhance both conversion and selectivity. Complementing this, the enzymatic oxidation step utilized laccase, a sustainable biocatalyst, immobilized in a packed-bed column reactor operating under continuous flow. Preliminary batch studies were conducted to understand the conversion kinetics and establish optimal parameters. Maximum FDCA yield was achieved with an enzyme concentration of 1 mg mL⁻¹ at 40 °C and pH 5. Additionally, the influence of substrate concentration, residence time, and reaction temperature was assessed for process intensification. This dual-step process exemplifies a green and scalable pathway, merging heterogeneous catalysis and biocatalysis for the valorization of biomass into high-value bio-based chemicals. The approach provides a forward-looking model for industrial adoption of sustainable oxidation technologies in the development of environmentally friendly polymers.