Unity of opposites: stabilization of cationic M6 metal cluster and anionic Lindqvist-type polyoxotungstate in hybrid salts and synergism in photodegradation of organic pollutants†

Metal cluster complexes and polyoxometalates (POMs) are inorganic polynuclear compounds having great potential for application in various fields, and especially in catalysis. The association of these two opposites – electron-rich clusters and electron-poor POMs – may favor the activity enhancement through electron/energy transfer processes. In this work, hybrid salts composed of cationic clusters [{M₆I₈}(DMSO)₆]⁴⁺ (M = Mo, W) and two anionic Lindquist-type polyoxotungstates [W₆O₁₉]²⁻ were obtained via three different approaches and their composition and phase purity were confirmed by a set of physicochemical analyses. Emission studies, supported by DFT calculations, demonstrated the possibility of electron transfer between the components. The water-dispersed materials showed high stability under harsh conditions such as ultrasonic treatment at elevated temperature, irradiation with light, and acidic environment. Photocatalytic properties were evaluated through the degradation of rhodamine B (RhB) under white light irradiation. Both materials exhibited zero-order kinetics, probably due to a diffusion-limited processes. Complete decomposition of RhB was observed after ∼25–30 min of irradiation with preservation of both activity and composition of catalysts for at least 5 cycles of dye degradation.