In Situ Observation of Polyoxometalate Formation by Vibrational Spectroscopy

Polyoxometalates (POMs) are multinuclear clusters of transition metals and oxo-ligands. They have a long history and are still gaining an increased relevance for diverse applications, such as sustainable catalysis. Although the first examples were discovered over a century ago, little is known about the process of their formation. We have now employed modern in situ IR and Raman techniques to gain insights into the processes of the formation of different POM structures in aqueous solution. Thereby, we were able to identify intermediates and optimize reaction conditions. We found that POM formation proceeds very rapidly even at low temperatures, making it unnecessary to reflux the synthesis solutions for multiple hours. With this knowledge, we developed an improved synthetic method for vanadium-substituted phosphomolybdates, which are of high relevance for sustainable catalysis.