Enhanced selective oxidation of 5-Hydroxymethylfurfural with a recyclable V34@Fe3O4/C catalyst Enriched with Mixed-valence polyoxovanadate active centers

Abstract

Exploring and discovering high-performance catalysts that efficiently catalyze the conversion of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) is of great significance for the future development of pharmaceuticals and polymers. Unlike the vanadium-substituted polyoxometalates previously employed for HMF catalytic conversion, this study examined a series of polyvanadates with well-defined structures, among which the 34-nuclear polyoxovanadate (V₃₄) demonstrated exceptional catalytic performance. In addition to the conventional notion that oxidation capability aids catalytic conversion, the terminal oxygen of V₃₄ exhibits superior hydrogen adsorption properties, thereby further enhancing the catalytic conversion of HMF. Under optimized conditions, the conversion rate of HMF and the yield of DFF can reach 98.7% and 97.2%, respectively. Additionally, via a hydrothermal method, V₃₄ can be easily loaded onto the magnetically nanospindle Fe₃O₄/C support generated from the carbonization of MIL-88(Fe), forming the V₃₄@Fe₃O₄/C composite catalyst. This catalyst maintains its efficiency in the directed conversion of HMF even under relatively moderate conditions, achieving conversion rates and DFF yields that are nearly 100%. Following 10 cycles of magnetic separation, the catalytic performance remains virtually unaltered, showcasing exceptional catalytic stability and recyclability. Further investigation into the catalytic mechanism of the V₃₄@Fe₃O₄/C catalyst uncovered a synergistic effect between Fe₃O₄/C and V₃₄. This interaction facilitates the transfer of electrons and protons in the proton-coupled electron transfer process, thereby enhancing catalytic efficiency. The synthesis of the V₃₄@Fe₃O₄/C polyoxometalate catalyst not only expands the range of HMF catalysts but also presents a novel technological strategy for the design of efficient and recyclable green biomass catalysts.