Ionothermal synthesis and characterization of two new heteropolytungstates with 1-ethyl-3-methylimidazolium bromide ionic liquid as solvent

Abstract

In this article, we have synthesized two new heteropolytungstate-based compounds [EMIM]₄[SiW₁₂O₄₀] (1) and [EMIM]₆[P₂W₁₈O₆₂] · 4H₂O (2) using the ionic liquid (IL) [EMIM]Br (EMIM = 1-ethyl-3-methylimidazolium) as a solvent and characterized them by infrared (IR) and ultraviolet (UV) spectra, thermogravimetric (TG) and elemental analyses, electrochemistry, and single-crystal X-ray analyses. Compound 1 is constructed from one [SiW₁₂O₄₀]⁴⁻ and four [EMIM]⁺. In the structure, [SiW₁₂O₄₀]⁴⁻ and [EMIM]⁺ are connected by hydrogen bonds with the surface oxygens of the polyoxoanion to form a 3-D supramolecular framework. The heteropolyanion of 2 is a classical Dawson-type structure [P₂W₁₈O₆₂]⁶⁻ and connected with six cations through hydrogen bonds. The structures of these two heteropolyanions are consistent with those synthesized by traditional methods, indicating that ionothermal synthesis is an effective method for the preparation of heteropolyoxometalates. The photocatalytic properties of these compounds have also been investigated.

Keywords:

• Polyoxometalates
• Ionothermal synthesis
• Photocatalysis
• Crystal structure

Acknowledgments

This work was supported by the National Natural Science Foundation of China (no. 20701005/20701006); the Science and Technology Development Project Foundation of Jilin Province (no. 20060420); the Postdoctoral station Foundation of Ministry of Education (no. 20060200002); the Testing Foundation of Northeast Normal University (NENU); Science and Technology Creation Foundation of NENU (NENU-STC07009) and Science Foundation for Young Teachers of NENU (no. 20070302/20070312); and the Program for Changjiang Scholars and Innovative Research Team in University.