Ionic liquids are salts with a melting point below 100 °C. They possess unique properties: while their vapour pressure is extremely low, their chemical and thermal stability is very high. The possibility to combine a large variety of anions and cations allows for designing liquids with tailor-made properties for various applications.
For instance ionic liquids are able to solve a large amount of carbon dioxide, while the solubility of other gases like nitrogen or carbon monoxide is low. Therefore ionic liquids can be used as absorbers or in supported liquid membranes to separate gases. Due to their low volatility there is no loss of the liquids as it is the case with amine scrubbers and the membranes will not dry out. The investigation of structure-property relationship is the base to understand the interaction and to come to tailor-made solutions.