Ionic liquids: history, conception, applications, and perspectives

Over the last few decades, ionic liquids (ILs) have emerged as a class of innovative solvents with unique physico-chemical properties such as low vapor pressure, high thermal stability, high solvation capacity among others making them attractive for a wide range of applications. This literature review takes an in-depth look at the physico-chemical properties of ILs, focusing on their molecular structure, viscosity, electrical conductivity, solvation power, density, and polarity. In addition, various methods for ILs syntheses are discussed, including conventional approaches and more recent synthetic methods such as green chemistry. In addition to their advantages, this review also addresses the environmental concerns associated to ILs, such as their toxicity, biodegradability, and recyclability. Finally, this review explores a large range of ILs applications in various fields, including catalytic chemistry, enzymatic synthesis, electrochemistry, extraction of bioactive molecules, depollution, and metals recovery. In summary, this review highlights the growing importance of ILs as alternative solvents and promoters to replace conventional organic solvents, while highlighting the challenges and opportunities associated with their use in a variety of applications.