Aerobic Oxidation of 5‐Hydroxymethylfurfural via Hydrogen Bonds Reconstruction with Ternary Deep Eutectic Solvents

A novel “hydrogen bond reconstruction” strategy was developed to enhance the reactivity of biomass-based compounds by utilizing a series of ternary deep eutectic solvents (DESs) as molecular scissors, thereby disrupting initial intermolecular hydrogen bonds and facilitating the reconstructing of new ones. Through this approach, 5-hydroxymethylfurfural (HMF) can be more efficiently solubilized, depolymerized and activated. In addition, DESs can activate the Anderson-type catalyst Na₅IMo₆O₂₄ via an electron transfer mechanism, which promoted the generation of oxygen vacancies and significantly improved its ability to activate molecular oxygen. Leveraging this innovative catalytic system enables efficient oxidation of HMF to FFCA.

Abstract

Hydrogen bonding effect exists widely in various chemical and biochemical systems, primarily stabilizing the molecular structure as a positive factor. However, the presence of intermolecular hydrogen bonds among biomass molecules results in a formidable challenge for the efficient utilization of biomass resources. Here in, a novel strategy of “hydrogen bonds reconstruction” was developed by a series of ternary deep eutectic solvent (DESs) as molecular scissors, which disrupting the initial intermolecular hydrogen bonds and reconstructing the new ones to increase the reactivity of the biomass-based compound. The DESs played a crucial role in enhancing the reactivity of 5-hydroxymethylfurfural (HMF) and promoting its oxidation through reconstructing the hydrogen bonds interactions. Furthermore, DESs was also found to activate the Anderson-type catalyst Na₅IMo₆O₂₄ (IMo₆) through an electron-transfer mechanism, which facilitated the generation of oxygen vacancies and significantly enhances its ability to activate molecular oxygen. With this novel catalytic system, oxidation of HMF exhibited remarkable efficiency as HMF was almost entirely converted into FFCA with an impressive yield of 98 % under the optimized conditions. This finding offers novel insights into the utilization of biomass resources and endows the solvent with new functions in the chemical reaction.

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