Immobilisation of ionic liquids on solid supports
A short summary of possible methods for the preparation of immobilised ionic liquids (ILs) is presented. The differences in the resulting heterogeneous catalysts are discussed and examples for the use of these catalysts in organic reactions are given. The different immobilised ionic liquids can be classified by their interaction with the support material. As will be shown, the ILs can be bound to a surface either by covalent bonds between silanol groups and the anion or the cation of the liquid, or without covalent bonds in the form of supported liquid phases (SLPs). In a few cases, the catalysts are prepared without actually using an ionic liquid at any step. Strictly speaking, these materials are not immobilised ionic liquids, but they are included here since they contain ionic complexes which show strong similarities to ionic liquids. In Friedel–Crafts alkylation reactions some of the novel catalysts show catalytic activities which are among the best to be found in literature.