Porous Liquids: The Next Frontier

Porous liquids are a new class of molecular- and colloidal-size porous materials that combine permanent porosity of solid sorbents and fluid properties of liquids. Different from transient molecular clathrates, porous liquids have the potential to reinvent materials syntheses and unify homogeneous and heterogeneous separations and catalytic and energy-related processes, previously ascribed to liquids and porous solids, respectively. Surface areas and pore volumes of the first examples of porous liquids based on porous molecular organic cages restricted their potential for technological applications. Recent advances in ionic liquid-based colloidal suspensions or covalently stabilized nanocomposites have improved the adsorption properties and increased our ability to tailor chemical composition and pore architecture. These hybrid porous liquids, however, still present challenges such as high melting temperatures, density, and viscosity. This critical review discusses these challenges and presents opportunities for selected emerging applications based on analogous structure to that of traditional colloidal systems.