Recent progress of covalent organic frameworks membranes: Design, synthesis, and application in water treatment

To date, significant efforts have been devoted to eliminate hazardous components to purify wastewater through development of various nanomaterials. Covalent organic frameworks (COFs), as an important branch of porous crystalline family, possess the peculiarity of ultrahigh surface area, adjustable pore size and facile functionality. Exciting study from design fabrication to potential applications in water treatment by COF-based membranes (COMs) have emerged. This review summarizes various preparation strategies and synthesis mechanism for COMs, including layer-by-layer stacking, in situ growth, interfacial polymerization, and electrochemical synthesis, and the advanced characterization techniques for COMs are also briefly described. Moreover, the application of COMs in heavy metal removal, dye separation, purification of radionuclides, pollutant detection, sea water desalination etc. are described and discussed. Finally, the perspectives on future opportunities for design COMs in water purification have been proposed, as well.