Encapsulated ionic liquids: A comprehensive review of production methods and potential applications
Patrícia Coimbra, Ana M.A. Dias, Hermínio C. de Sousa
Abstract
• Encapsulation of ionic liquids (ILs) is comprehensively reviewed. • Main methods of ILs encapsulation are described. • Established and emergent applications of encapsulated ILs (ENILs) are critically discussed. • Key aspects for the further development of these materials are discussed. • Areas in which ENILs have the greatest potential for innovation are identified. Ionic liquids (ILs) are widely investigated as advanced solvents. However, their practical application is sometimes limited by kinetics issues, arising from their typically poor mass transport properties. The encapsulation of ILs within organic or inorganic shells, with diameters ranging from the nanometer scale to a few millimeters, has been proposed as a strategy to enhance the mass transfer rates of ILs. This review provides a comprehensive overview of encapsulated ionic liquids (ENILs). It begins by summarizing the most relevant properties of ILs and by identifying ILs already encapsulated. This introduction is followed by the description of the most representative IL encapsulation strategies reported in the literature, many of which are based on classical encapsulation methods. The predominant applications of ENILs in separation processes, particularly for CO 2 capture and water contaminant removal are summarized and discussed. In addition, other emerging applications are highlighted, including the use of ENILs as microreactors, as drug delivery and theragnostic vehicles, and as components in composite materials with advanced functional properties. This work shows that ENILs are versatile materials with a wide range of potential applications beyond separation processes.