Covalently Supported Ionic Liquid Phases: An Advanced Class of Recyclable Catalytic Systems

In this review, the most recent advances in the synthesis and catalytic applications of covalently supported ionic liquid (IL) phases will be discussed. This class of recyclable catalytic materials is based on the covalent attachment of several types of ammonium salts, usually imidazolium, but also thiazolium, triazolium, and pyrrolidinium salts, on the surface of different supports, for example, silica, periodic mesoporous organosilica, polystyrene, magnetic-based materials, carbon nanotubes (NTs), halloysite NTs, polyhedral oligomeric silsesquioxane (POSS), and fullerenes. Moreover, poly(ionic liquid) materials, in which the IL-based structure also acts as a support, will be considered. The synthetic applications of these materials will be presented, with special emphasis on their roles as catalysts, without added organocatalysts or metal-based catalysts, as supports for organocatalysts, and as supports for metal-based catalysts.