Tuning the Directional Solubility of Ionic Liquids through Multicomponent Ions for Low-Temperature Desalination

Directional solvent extraction (DSE) is an emerging technology capable of utilizing low-temperature heat sources (e.g., waste heat) for desalination, but the identification of high-performing directional solvents remains a significant unmet need hindering its broader implementation. Herein, we report the design of thermoresponsive ionic liquids with multicomponent ions as a powerful class of directional solvents. Our studies revealed that freshwater yield and ion rejection rates for [choline][NTf2] were greatly enhanced by the addition of [choline][OH]. Molecular simulations highlight the importance of balancing hydrophilicity and hydrophobicity through the addition of polar, protic functional groups in the development of a reliable structure-function relationship toward identifying an optimal ionic liquid-based directional solvent. The newly developed ionic liquid directional solvents may significantly advance the DSE technology to solve the global water shortage challenge.