Strategic Metal Doping in MnOx Catalysts Unlocks High-Yield 2,5-Furandicarboxylic Acid Production via Tailored Lattice Oxygen Activity and Oxygen Vacancies

Abstract

2,5-Furandicarboxylic acid (FDCA), derived from the oxidation of 5-hydroxymethylfurfural (HMF), is emerging as a viable biomass-based monomer for bioplastic production, offering a sustainable alternative to a petroleum-derived monomer. This study systematically investigates lattice oxygen (O_L) activation in Mn-based oxides through doping with transition metals (Ce, Zr, La, and Sm) to enhance the aerobic oxidation of HMF to FDCA. Among the prepared catalysts, Mn₆Ce₁O_x (Mn/Ce molar ratio of 6), with the highest surface oxygen vacancy (O_V) concentration and activated O_L, achieved a high FDCA yield of 97.2% with a generation rate of 1520 μmol_FDCA g_cat^–1 h^–1 under mild conditions (120 °C, 1 MPa O₂, 8 h). Catalyst characterization results revealed that the metal dopants modulated the strength of Mn–O bonds, thereby influencing O_L activity and O_V concentration. Incorporating Ce ions into the MnO_x lattice weakened Mn–O bond strength, enhancing O_L mobility and promoting O_V formation. This reactive O_L, acting as the active oxygen species for HMF oxidation, could be efficiently regenerated via the Mars–van Krevelen mechanism. The abundant O_V on Mn₆Ce₁O_x promoted the adsorption of both O₂ and HMF. The synergistic roles of O_V and O_L contributed to the high activity of this catalyst in converting HMF to FDCA. This study provides critical insights into the strategic regulation of O_L activity in Mn-based oxides, offering promising avenues for improving the efficiency and cost-effectiveness of biomass-based chemical production via catalytic oxidation.