Direct mechanochemical synthesis of polyoxometalates

Mechanochemistry can offer alternative paths to producing polyoxometalates (POMs) from simple reagents and under less stringent conditions than traditional wet synthesis. A molybdenum isoPOM and two different molybdenum heteroPOMs, of the Strandberg- and Keggin-type, can be directly produced by molybdenum oxide, potassium or ammonium carbonate and phosphate, via simple grinding in a ball mill. The reaction may last from 30 minutes to 3 hours, while products are controlled by the stoichiometric ratio of the reagents and the liquids used. In situ investigations of the syntheses by synchrotron X-ray diffraction have revealed the formation of different intermediates along the reaction path. Their identification helps to explain the underlying mechanism of the reaction by which they are formed and progress towards the final POMs.