Conversion of cellulose to 5-hydroxymethylfurfural over vanadium-modified Dawson polyoxometalate catalysts

5-Hydroxymethylfurfural (5-HMF), an emerging platform compound, holds significant potential in chemical synthesis and is widely applicable in the production of biofuels, biodegradable plastics, and fine chemicals. While acid-catalyzed dehydration of hexose represents an effective route to 5-HMF, the limited availability of hexose and the abundance of cellulose make the direct conversion of cellulose to 5-HMF a more economical strategy by avoiding hexose separation. In this study, Dawson-type polyoxometalates (POMs) were screened for the catalytic conversion of cellulose to 5-HMF. The vanadium-modified catalyst H₇P₂Mo₁₇VO₆₂ (V1) afforded the highest yield under optimized conditions: 0.1 g microcrystalline cellulose (MCC), 0.1 g catalyst, 190 °C, 6 h, and a water/methyl isobutyl ketone (MIBK) ratio of 1:5. This system achieved a 63 % yield of 5-HMF and a 4 % yield of levulinic acid (LA). Preliminary recovery experiments on the catalyst were conducted, and the results showed that the catalyst lost its performance after 3 to 4 cycles of use. After five cycles were completed, 5-HMF with a yield of 42 % was finally obtained. The incorporation of vanadium into the Dawson-type POM structure modulated both the acidic and oxidative properties of the catalyst, which significantly influenced the product distribution. This work demonstrates a synergistic catalytic approach leveraging tailored acidity and oxidative functionality for the efficient transformation of cellulose to 5-HMF.