Polyoxometalate-based Ionic liquid as thermoregulated and environmentally friendly catalyst for starch oxidation

[Display omitted] ► Easily synthesis of POM-based ionic liquid catalyst [(CH3)3NCH2CH2OH]5PV2Mo10O40 ► Thermoregulated catalysis based on POMs, which means it could be used as a homogeneous catalyst for oxidation of starch when raising the temperature. ► Highly efficiency (0.59 molCO2H per 100 g) and high selectivity on producing of polyhydroxycarboxylic acids. ► Easily handling of this catalyst for reuse. A new kind of polyoxometalate (POM) ionic liquid ([(CH3)3NCH2CH2OH]5PV2Mo10O40) (abbreviated as Ch5PMo10V2O40) has been synthesized by a precipitation/ion exchange method with choline chloride and H5PMo10V2O40 as precursors. The produced salt turned out to be an original ionic liquid (IL) catalyst and exhibited a novel switchable property based on temperature variation. In this regard, it refers to a thermoregulated feature that elevated temperature leads to the miscibility of catalyst and substrate. As decreasing the temperature, the catalyst precipitates and becomes heterogeneous form to be separated automatically from the reaction mixture. The combination of POMs with choline chloride was also proved to be effective in catalyzing the oxidation of starch, which showed higher or nearly identical performance with traditional catalysts, such as FeSO4. Results demonstrated the catalyst was easily separated from the products and the retrieved Ch5PMo10V2O40 could be repeatedly used without appreciable loss of its performance, which highlighted the practical application of this important biomass.