Covalent organic framework-based membranes for liquid separation

Covalent organic frameworks (COFs) are a class of organic porous polymers with regular pore structures, which are connected by organic building units through covalent bonds. The unique features of COFs, such as regular pore, uniform pore size and tunable pore environment, provide great potential in the field of membrane separation. In this review, we focus on the COF-based membranes for liquid separation. We first summarize their synthesis and characterization methods, and briefly discuss the separation mechanism and the key factors for improving their separation performance. Then, we give an introduction to the liquid separation of COF membranes from three aspects: water treatment, the recovery and purification of organic solvents, and chiral separation. Finally, a perspective on the opportunities and challenges for next-generation COF-based membranes for liquid separation is given.