Mesostructured Non-Oxidic Solids with Adjustable Worm-hole Shaped Pores: M-Ge-Q (Q = S, Se) Frameworks Based on Tetrahedral [Ge4Q10]4- Clusters

Abstract

The discovery of MCM-41 and its relatives has spawned a revolution in the design and synthesis of tailored mesostructured oxide-based materials. By comparison, non-oxidic solids such as sulfides or selenides are only very little exploredÐpartly because of difficulties in handling or obtaining relevant precursors (e.g., [SiS4] 4± units). Direct sulfur and selenium analogs of MCM-41 type materials would be the thioand selenoaluminosilicates. However, these systems are expected to be very unstable to hydrolysis. Therefore, one needs a working analog for the sulfides and selenides to mimic some of the characteristics of the [SiO4] 4± unit. A suitable such building unit with tetrahedral topology and similar charge is the adamantane thioanion [Ge4S10] 4± (or its selenium analog) (Scheme 1), which is made of four corner-linked [GeS4] 4± tetrahedra. We have already studied in detail their corresponding salts (RNMe3)4[Ge4Q10] (abbrev. as CnGeQ) with various surfactants. Reports on mesostructured chalcogenides have begun to appear, such as CdS and ZnS prepared through the incorporation of surfactants. Also, initial studies on mesostructured tin sulfides and a brief report on the synthesis of mesostructured thiogermanates resulting from the hydrothermal treatment of amorphous GeS2 and C16H33NMe3 Br, (CTA), are noteworthy. Various microstructured metal sulfides resembling those of zeolites have been forecast and important first steps have been made in recent years. The adsorption and sensing behavior of some structurally well-defined microporous lamellar tin sulfides (cation)2Sn3S7 have been explored. [15] Small guests such as NH3, H2S, and alcohols were found to interact with these materials. A recent exciting development toward producing well-defined mesostructured materials is the discovery of ASU-32, a novel indium sulfide that features pore diameters of ~14.5 Š.