Engineering membranes with macrocycles for precise molecular separations

Abstract

Macrocycles are a class of intrinsically porous organic molecules that can host guest molecules selectively. Owing to their diversified porous characteristics, host–guest/supramolecular feature, unique chemical versatility and tunable chemical functionalities, macrocycles are considered fascinating membrane building blocks for advanced and efficient separations. Continuously growing research explorations on macrocycle-based membranes have recently emerged ranging from preparation tactics to applications; however, their significance for membrane separations is far from being fully recognized and understood. Therefore, it is important to timely and systematically summarize the progress of macrocycle-based membranes and provide genuine insight for future studies in this interesting field. In this review, we first discuss the different types of macrocycles used to produce high-quality membranes and elucidate their characteristics. We then focus on fabrication approaches, including blending, surface (or pore) modification, crosslinking and self-assembly by discussing the merits and limitations of each approach. We also break-down the different applications of macrocycle-based membranes including water treatment, pervaporation and organic solvent nanofiltration and chiral separation. All separation applications are evaluated and analyzed in terms of current efficiency and future prospects. Most importantly, this review highlights the challenges and opportunities for improving these smart membranes in order to scale-up and translate this promising technology directly into the consumer market.