Solid-State Preparation of MnOx catalysts for selective aerobic oxidation of 5-HMF to 2,5-FDCA in aqueous medium

The selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) offers a green, sustainable route to bioplastic production. However, developing highly efficient and affordable non-noble metal catalysts for this oxidation remains a challenge. This study reports a highly active MnO x catalyst synthesized via a simple, cost-effective, and environmentally benign solid-state method. The catalyst was characterized with several analytical techniques, such as BET, XPS, SEM, and XRD, which showed diffraction peaks corresponding to various manganese oxidation states, while BET measurements confirmed a mesoporous material with a high surface area of 284 m²/g. The XPS shows a high Mn 3+ ratio of 56% in the freshly prepared MnO x , and 26% of the used catalyst, which can be attributed to the catalyst's activity. The catalytic performance was evaluated for the aerobic oxidation of HMF in water. Key parameters, including reaction time, catalyst loading, and temperature, were systematically optimized. Under the established optimal conditions (11 h, 120 °C, HMF: MnO x weight ratio of 1:2), a 96.4% yield of FDCA was achieved, with complete HMF conversion and full selectivity. The results suggest that the reaction proceeds via the formation of an HMFCA intermediate. After completing the reaction, the catalyst was recovered and reused over multiple consecutive runs with no significant loss in the catalytic activity performance.