Designing organic solvent separation membranes: Polymers, porous structures, 2D materials, and their combinations

As the interest for membrane-based organic solvent separation increases, membrane materials exhibiting high permeance, high selectivity, and long-term stability against solvents are sought. Membrane technology has experienced tremendous progress by integrating well-established polymeric membranes with emerging materials such as porous polymers, metal-organic frames (MOFs), and two-dimensional (2D) materials. This review aims to provide a timely update on novel molecular architectures developed to surpass permeability and selectivity trade-off and improve stability. First, we describe the transport mechanisms of organic liquids in membranes and summarize the state-of-the-art commercial membranes. Second, various strategies in designing polymers to improve separation performance are presented, including chemical functionalization and cross-linking. Third, we critically review porous materials with well-controlled nanostructures, such as polymers of intrinsic microporosity (PIMs), covalently organic frameworks (COFs), carbon molecular sieves (CMS), and mixed matrix membranes (MMMs). Finally, membranes based on 2D materials with exciting separation properties are highlighted.