Selective Oxidation of Biomass-Derived 5-Hydroxymethylfurfural Catalyzed by an Iron-Grafted Metal-Organic Framework with a Sustainably Sourced Ligand

The efficient conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is a major challenge under base-free conditions with inexpensive catalysts. We report a precious-metal-free recyclable MOF-based catalyst (CAU-28), constructed from the FDC ligand, with grafted redox-active Fe sites. This enables the conversion of HMF to FDCA under solvothermal heating or microwave-assisted methods in base-free aqueous conditions. The optimized process achieves 100% HMF conversion producing FDCA at the gram scale with a 70-80% yield in 1 h. The turnover frequency (TOF) and cost-normalized TOF for the best catalyst are >800 h-1 and >1000 h-1 -1 pound, respectively, surpassing those of conventional catalysts and processes using precious elements or basic additives for HMF conversion. The economic viability and practical applicability of the process are further realized by utilizing the catalytically derived FDCA (without purification) for the successful construction of pristine CAU-28 MOFs and formation of the biodegradable plastic polyethylene furanoate (PEF) after purification.