One-pot, One-step Synthesis of 2,5-Diformylfuran from Carbohydrates over Mo-Containing Keggin Heteropolyacids

In this work, a one-pot strategy for directly converting fructose into 2,5-diformylfuran (DFF) over Mo-containing Keggin heteropolyacids (HPAs) in open air is developed. H3PMo12O40 HPA is found to show high activity and selectivity to the formation of DFF owing to its higher Bronsted acidity and moderate redox potential. The partial substitution of the H+ in H3PMo12O40 with Cs+ leads to the heterogenization of the HPA by forming its cesium salts CsxH3-xPMo12 (x = 0.5, 1.5, and 2.5). A satisfactory yield of 69.3% to DFF is obtained over Cs0.5H2.5PMo12 polyoxometalate after deliberate optimization of the reaction conditions. The heterogenized polyoxometalate could be recycled and reused without significant loss of catalytic activity for five runs. The produced DFF could be separated from the resulting mixture by an adsorption-desorption method using activated carbon as the adsorbent and furfural as the desorbent. A highest isolated yield of 58.2% is obtained.