Photocatalysis with Na4W10O32 in water system: Formation and reactivity of OH radicals

Photoexcitation of Na4W10O32 dissolved in water leads to the formation of hydroxyl radicals. These species originate both from H2O oxidation and H2O2 reduction. EPR-spin trapping investigation and laser flash photolysis experiments contribute to clarify their formation mechanism and their involvement in the oxidation of propan-2-ol. Continuous irradiation of water solutions of Na4W10O32 leads to the overoxidation of propan-2-ol to CO2 with high yield. This result may be of interest for the development of photocatalytic systems aimed to pollutants degradation. Entrapment of Na4W10O32 into a microporous silica matrix gives a rather robust photocatalyst where the decatungstate structure is preserved. This material is able to catalyze the photooxidation of propan-2-ol to acetone with appreciable chemoselectivity. In particular, it is seen that the solid photocatalyst yields acetone as main product inhibiting its over-oxidation to carbon dioxide.

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► Na4W10O32-photoassisted formation of OH radicals in water has been proved.
► OH radicals originate both from H2O oxidation and H2O2 reduction.
► OH radicals are directly involved in the oxidation of propan-2-ol.
► Entrapment of Na4W10O32 in a proper microporous silica minimizes CO2 production.