Base-free atmospheric O₂-mediated oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic acid triggered by Mg-bearing MTW zeolite supported Au nanoparticles

Mg-bearing MTW silicalite zeolite, MgSi-ZSM-12, was straightforwardly synthesized by involving an unusual acidic pre-gelation system and engaged as the task-specific support for loading the Au nanoparticles (NPs). The resulting Au/MgSi-ZSM-12 catalyst showed stably excellent activity for the oxidation of HMF into FDCA in the presence of atmospheric dioxygen (O₂) without externally adding any liquid base, affording a yield of 87 % and turnover number (TON) of 331 based on the surface Au sites. Superior basicity was evidenced by embedding Mg species into the all-silica zeolitic skeleton, which enables strong, weak, and near-zero affinity towards aldehyde, alcohol, and carboxyl groups, respectively, thus, allows rapid and high-uptake adsorption of HMF, but negligible adsorption of FDCA. This unique feature of the Mg-bearing all-silica zeolite support together with its synergy with the active sites of Au NPs is revealed to accelerate the production of FDCA under the base-free mild condition.