Crystalline metal chalcogenides are a class of important functional materials that may find applications in thermoelectricity, photocatalysis, ion exchange, and fast-ion conductivity. The progress of chalcogenide chemistry benefits much from the development of new synthetic methods. ionic liquid (IL) has received ever growing attention due to its ability to be an alternative of conventional organic solvents in many processes, as well as other fascinating applications. In particular, the preparation of novel inorganic and inorganic-organic hybrid materials such as zeolites and metal-organic frameworks in ILs has become a hot research topic in recent years, because the specific ionic crystallization environment and structure-directing effects of ILs would favor the formation of novel compounds that are inaccessible in traditional molecular solvents. However, utilization of ILs in synthesizing new crystalline metal chalcogenides has been scarcely reported.

The research group headed by Prof. HUANG Xiaoying at Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences (CAS), has made significant progress on the synthesis of novel crystalline metal chalcogenides in ionic liquids.

Using IL as solvent and structure-directing agent, they successfully synthesized the first examples of IL-directed three-dimensional open-framework selenidostannates and two-dimensional microporous structures composed of inorganic selenidostannate nanotubes (Figure 1). The compounds are constructed by different linkages of [SnSe4] tetrahedra and [Sn3Se4] semicubes and possess nanopores in multi-directions, with nearly 60% solvent-accessible volumes after excluding the IL cations (Angew. Chem. Int. Ed. 2011, 50, 11395-11399). Recently, they have also obtained in ILs a series of the largest discrete T5 cluster compounds with Cu-M-S constitutions (M = In, Ga) (Figure 2), in which the IL cations play an important role in separating and stabilizing the large clusters (Chem. Sci., 2012, 3, DOI:10.1039/C2SC00824F).

This research provides a valuable synthetic route towards novel crystalline metal chalcogenides.

 

Figure 1. Crystalline open-framework selenidostannates synthesized in ionic liquids.

 

　 Figure 2. Largest discrete supertetrahedral T5 clusters synthesized in ionic liquids.