The recent advance of precisely designed membranes for sieving

Abstract

Developing new membranes with both high selectivity and permeability is critical in membrane science since conventional membranes are often limited by the trade-off between selectivity and permeability. In recent years, the emergence of advanced materials with accurate structures at atomic or molecular scale, such as MOF, COF, graphene, has accelerated the development of membranes, offering opportunities to manipulate the membrane structures precisely. In this review, current state-of-the-art membranes are first reviewed and classified into three different types according to the structures of their building blocks, including laminar structured membranes, framework structured membranes， and channel structured membranes, followed by the performance and applications for representative separations (liquid separation and gas separation) of these precisely designed membranes. Last, the challenges and opportunities of these advanced membranes are also discussed.

Bioinspired Gradient Covalent Organic Framework Membranes for Ultrafast and Asymmetric Solvent Transport

“…Due to their highly aligned nanopores, [ 20 ] also called single‐digit nanopores (SDNs), COFs showed potential in separation applications. [ 21,22 ] For example, some ultrathin COF membranes with tunable aperture [ 23 ] can surpass conventional separation materials [ 24 ]; However, although powdery COFs normally possess large surface areas, tunable pore sizes/structures along with tailorable functionalities, most these features cannot be simply inherited by their membrane derivatives because of the inevitable defects in COF's rigid skeleton on a large scale; Consequently, the fabrication of macroscale COF membrane is facing significant challenges. [ 25 ] I) poor crystallinity/inevitable defects in macroscale; II) low chemical stability as membranes; III) mechanical weakness in a membrane state; IV) restrained functionalities derived from low processabilities.…”