Microporous decatungstates: Synthesis and photochemical behavior

Photoreactive decatungstates Na4W10O32 and (nBu(4)N)(4)W10O32 were heterogenized inside the silica network via a sol-gel technique, resulting in the Na4W10O32/SiO2 (Na1) and (nBu(4)N)(4)W10O32/SiO2 (Q1) composites. The physicochemical properties of as-synthesized composites were measured by UV diffuse reflectance spectrum, Fourier transform infrared, thermogravimetric analysis and differential thermal analysis, inductively coupled plasma-atomic emission spectroscopy, and scanning electron microgragh, suggesting that the structural integrity of the decatungstates has been preserved after incorporation into the silica network. The microporous structures of the Nat and Q1 were confirmed by the nitrogen adsorption measurements. The photocatalytic behaviors of the composites were studied via degradation and mineralization of organophosphorus pesticide, trichorofon (TCF), under near-UV irradiation and in media where they are insoluble. The photocatalytic behaviors of the Nat and Q1 were also compared with two silica-supported decatungstates, Na4W10O32-SiO2 (Na2) and (nBu(4)N)(4)W10O32-SiO2 (Q2). It indicated that the Nat had the highest photocatalytic efficiency among four insoluble decatungstates, and the leakage of the catalyst from the support was hardly observed for Nat. Studies on the reaction mechanism indicate that OH. radical attack may be responsible for the degradation and final mineralization of TCF.