A polyoxometalate-based ionic crystal assembly from a heterometallic cluster and polyoxoanions with visible-light catalytic activity

Abstract

A polyoxometalate-based inorganic–organic hybrid [WO₄{Ni(en)₂(H₂O)}₃] [Ni(en)₃]{P₂W₁₈O₆₂}·[Ni(en)₃]CO₃·H₂O (1) (en = ethanediamine), was synthesized under hydrothermal conditions, and characterized by IR, elemental analyses, XPRD, UV diffuse reflectance spectroscopy and single crystal X-ray diffraction analyses. Compound 1 consists of a heterometallic cluster [WO₄{Ni(en)₂(H₂O)}₃]⁴⁺, two [Ni(en)₃]²⁺ groups, one [CO₃]²⁻ group, one water molecule and a Wells–Dawson anion [P₂W₁₈O₆₂]⁶⁻ ({P₂W₁₈}), which represents the first POM-based ionic crystal with the heterometallic macrocation cluster. Photocatalytic studies indicate that compound 1 is not only actively photocatalytic for degradation of methylene blue (MB) under visible light irradiation, but very stable and easily separated from the reaction system for reuse as well.