Point-functionalization of ionic liquids: An overview of synthesis and applications

In recent years, the designer nature of ionic liquids (ILs) has driven their exploration and exploitation in numerous fields. Undoubtedly, the most attractive feature of ILs is their tunability and the incorporation of functional groups into the cations or anions is the most efficient way to impart a particular property. Functionalized ILs are generally named "task-specific ionic liquids" (TSILs). In this review, we survey some of the classes of TSILs, generally characterized by the presence of only one "common" functional group, arising from slight modifications (here, defined as "point-functionalization") that can be achieved through simple synthetic procedures. In particular, we will discuss their synthesis, immobilization and applications in some specific fields. Among these, we consider their use as solvent catalysts in organic synthesis and metal-catalysed processes, and as fluids in metal extraction processes and gas capture, highlighting their possible uses in materials sciences. The aim of this review is to provide, through a careful survey of the literature, indications of sustainable and rational developments in this extremely prolific field.