Hydrophobic deep eutectic solvents

Hydrophobic deep eutectic solvents combine the typical, desirable features of deep eutectic solvents; inexpensive, benign, often naturally occurring components with high hydrogen bond-forming tendencies with hydrophobicity; and the ability to form biphases with water. This implies an intrinsically challenging design, where hydrophobicity is obtained in mixtures of components that can form hydrogen bonds and so have hydrophilic tendencies. Moreover, this is usually achieved without resorting to the use of expensive perfluorinated components. This chapter outlines design strategies of hydrophobic deep eutectic solvents, followed by an overview of the key applications as extraction media for organic molecules from fermentation broths and wastewater streams, metal ions from aqueous media, and other uses including microextraction for analysis and CO2 capture.