Tunable solvents for separation: a comprehensive review of ILs and DESs in aqueous biphasic systems

Aqueous biphasic systems (ABSs), known for their mild operating conditions, have attracted considerable attention in the field of separation science. The advent of ionic liquids (ILs) and deep eutectic solvents (DESs) as tunable and sustainable solvents has introduced breakthrough alternatives to conventional polymer/salt-based ABSs. This review provides a comprehensive analysis of the physicochemical properties of ILs and DESs, and the applications of IL/DES-based ABSs, with a focus on their phase behavior, phase separation mechanisms, and inherent sustainability advantages. Furthermore, future perspectives are proposed to advance the field, including the rational design of task-specific ILs/DESs, and integration with emerging hybrid separation technologies. These insights aim to accelerate the development of high-performance, eco-friendly separation platforms for industrial applications.