Introduction, Types, Properties, and Applications of Switchable Solvents: A Review

Abstract

Switchable solvents (SS) are a class of liquids with the unique ability to significantly alter their physical properties in response to external stimuli such as changes in temperature or the introduction or removal of CO2 gas. This reversible behaviour allows them to return to their original state with minimal changes, making them highly advantageous for various applications. A notable example of a switchable solvent is waste carbon dioxide gas, which is non‐toxic, non‐flammable, and cost‐effective. The versatility of switchable solvents extends to their polarity and physical states, which can be modified through molecular adjustments, opening new pathways for research and industrial applications. This review provides a comprehensive overview of switchable solvents, including their classification, history, properties, and applications, with a particular focus on their role in green chemistry. The types of switchable solvents discussed include Switchable‐Polarity Solvents (SPS), Switchable‐Hydrophilicity Solvents (SHS), and Switchable Water. Each type is examined in terms of synthesis, chemical properties, and development. The desirable properties of switchable solvents, such as their efficiency and recyclability, make them suitable alternatives to traditional solvents in various fields. Their applications range from water treatment and oil extraction to cleaning solid particles and recovering residual motor oil. Additionally, switchable solvents have proven effective as reaction media and in recovering polystyrene from foam. This paper also highlights the environmental benefits of switchable solvents, emphasizing their role in reducing the ecological impact of chemical processes. The potential for future developments in this field is significant, with ongoing research aimed at enhancing their performance and expanding their applications. By providing a detailed analysis of switchable solvents, this review aims to support researchers and industry professionals in developing more sustainable and efficient chemical processes.