Photo-electrochemical and physical characterizations of a new single crystal POM-based material. Application in photocatalysis

•A new single crystal POM-based hybrid compound was synthesized by hydrothermal route.•[(H2pip)3][α-PW12O40]2·4H2O exhibits n-type conduction and two optical transitions.•The valence and conduction bands are made from O2−:2p; W6+:5d orbitals respectively.•The energy band positions of the compound lead to dye photo-degradation.

A new inorganic-organic hybrid material [(H2pip)3][α-PW12O40]2·4H2O, prepared by hydrothermal method, was structurally characterized by single-crystal X-ray diffraction. The compound based on a Keggin-type polyoxotungstate and piperazine (pip) displays a hybrid framework built from two (α-Keggin)3− polyoxoanions and three (H2pip)2+ hydrogen-bonded fragments, forming 3-D supramolecular architecture. The diffuse reflectance spectrum shows two optical transitions directly (3.27 eV) and indirectly (3.12 eV) allowed. The electrical conductivity follows an exponential law, indicating a semiconducting comportment with activation energy of 14 meV. The Mott-Schottky characteristic, plotted in Na2SO4 (0.5 M) solution indicates n-type conduction with a flat band potential of −0.084 VSCE and electrons density of 4.24 × 1018 cm−3. As application, the photo-degradation of methylene blue (MB) upon UV irradiation was successfully achieved by OH• radicals. The improved activity is attributed to the potentials closeness of the valence and conduction bands with the radical levels.

Graphical abstractPhotocatalytic degradation of methylene blue on [(H2pip)3][α-PW12O40]2·4H2O supramolecular material.Figure optionsDownload full-size imageDownload as PowerPoint slide