Reversible ionic liquids designed for facile separations

Reversible ionic liquids can increase the application of traditional ionic liquids, such as those based on imidazolium cations, and generate new technologies along the way. While traditional ionic liquids have gained industrial and academic attention as solvents, many applications suffer from the difficulty associated with removing high boiling point products from non-volatile liquids. Reversible ionic liquids are those which can be reversed back and forth between molecular and ionic forms enabling facile separations through large in situ property changes. Thus these novel solvents lead to truly sustainable processes. An understanding of the phase behavior of these systems provides insight into the separation capability. Here we review both one- and two-component reversible ionic liquids and their applications with an emphasis on separations.