Improvement strategies on application of covalent organic frameworks in adsorption, photocatalytic, and membrane processes for organic pollution removal from water

Recently, covalent organic frameworks (COFs), as emerging structures produced by assembling organic building blocks via covalent bonds, have drawn great attention for water treatment due to their high surface area and pores, numerous functional groups, and excellent chemical stability. Applying appropriate functional groups and building units and making COF-based composites represented effective strategies to enhance removal efficiency. In the photocatalytic, membrane separation, and adsorption processes, these strategies can result in the production of more charge carriers and degradative species, controlling water flow and rejection, and selective adsorption of organic pollutants. In this comprehensive review, the synthesis and modification methods of COFs and the recent advancement of their application in the removal of organic pollutants from water by adsorption, photocatalytic, and membrane separation processes were highlighted. Finally, the current challenges and future perspectives in the application of COFs in these processes are discussed.