Microwave-assisted hydrolysis of polysaccharides over polyoxometalate clusters

•Phosphotungstic acid effectively hydrolyzed starch and cellulose during microwaving.•Clusters of phosphotungstic acid were stable and recyclable after hydrolysis.•The dielectric property of phosphotungstic acid could conserve microwave energy. Polyoxometalate (POM) clusters were utilized as recyclable acid catalysts and microwave-absorbing agents for the microwave-assisted hydrolysis of corn starch and crystalline cellulose. Phosphotungstic (PW) and silicotungstic (SiW) acids showed high hydrolyzing activity, while phosphomolybdic acid (PMo) showed lower glucose stability. The PW catalyst could be recycled by ether extraction at least 4 times without changing its catalytic activity. The addition of PW could reduce the energy demand required for running the hydrolysis by 17–23%. The dielectric property of the aqueous PW solution was important for increasing the microwave-absorption capability of the reaction system and reducing the energy consumption.