Clay Minerals-Ionic Liquids, Nanoarchitectures, and Applications

Clay minerals, whose world resources are extremely large, have the potential to be more exploited as the basis for functional materials. Of interest are their interactions with ionic liquids (ILs). These compounds have found a large number of applications in the last few decades due to unique properties, such as low vapor pressure, high thermal stability, and remarkable solvation abilities. In the case of the swelling smectites, the organic cation of ILs can replace interlayer cations and find applications in the preparation of nanocomposites. This feature article is mainly focused on kaolinite, a nonswelling 1:1 phyllosilicate, whose layers are essentially neutral. Consequently, the intercalation of ILs involves both cation and anion. The organic cations can be designed to bear hydroxyl groups that will react with the aluminol internal surface of kaolinite, resulting in ionic liquids not only intercalated but also grafted. The resulting nanohybrid materials are characterized by a fixed, rigid, constrained 2D structure, whose dimension can be tuned by the size of the organic cation, whereas the anion is exchangeable. These materials are used for sensing applications such as the specific detection of anions as well as their quantitative analysis. They are also used as catalyst support for nanoparticles.