Mixed-Matrix Ion Gel Membranes for Gas Separation

The potential of ionic liquid materials to improve membrane-based gas separation processes has been realized during the past few years, through the exploitation of diverse configurations, chemical functionalities, and properties. Nowadays, one of the most recent trends on this field is the development of mixed-matrix ion gels, an emerging family of ionic soft-solid materials, in which fillers are embedded into polymer/IL matrices. This review aims at presenting an overview on the latest developments and advances on ion gel membranes containing a third component, such as zeolites, metal organic frameworks, silica, graphene oxide, metal salts, and nanoparticles, for gas separation processes. We provide an analysis of this building system and highlight the diverse type of mixed-matrix ion gels hitherto reported, for which the impact of the different fillers on the ion gels' overall properties is discussed in detail. The main challenges on their preparation, as well as their transport mechanism and how it can be influenced by the different fillers, are also addressed. Finally, technological aspects, perspectives, and opportunities to pursue this topic are discussed from a critical point of view.