Development of the composite materials based on framework structures and designable solvents in separation fields

The framework materials such as metal–organic framework (MOF), covalent organic framework (COF), and zeolite imidazolate framework (ZIF), possess numerous outstanding properties including a large surface area, high porosity, tunable pore size, and stable thermal and chemical capabilities, among others. In recent years, ionic liquids (ILs) and deep eutectic solvents (DESs), which serve innovative types of designable or functional solvents, have undergone rapid development due to their environmentally friendly nature, low melting point, and other significant properties. The introduction of ILs or DESs as guest solvents into the matrix materials of MOFs, COFs, or ZIFs can improve the physicochemical properties of the composite materials, enabling their widespread application in the field of separation. In particular, these composites outperform the original framework materials in terms of gas storage, adsorption, membrane-based gas separation, and ionic conductivity. Therefore, this review traces and summarizes the research progress in the synthesis, properties, and separation of functional framework composites materials based on ILs or DESs. This review aims to identify the opportunities and challenges of composite materials in the field of separation, providing a reference for the development of future industrial processes.