Smart superwetting COF membrane for controllable oil/water separation.

[Display omitted] • A series of COF membranes with tunable wettability were constructed using COF nanofibers by filtration assembly. • The membrane exhibits superior robustness and flexibility and can be easily peeled off from substrates into a self-standing membrane. • The membrane can achieve switchable separation of light oil/water, heavy oil /water, water-in-oil and oil-in-water emulsion. • The membrane presents excellent stability and recyclability. Covalent organic frameworks (COFs), as a kind of porous crystalline materials, have exhibited tremendous application prospects in various fields over the past few decades. Nonetheless, the employment of COFs in oil/water separation field was rarely reported. Herein, we prepared a robust and loose COF membrane using the collected COF nanofibers by filtration assembly method. The obtained COF membrane possesses unique superwettability, which endows the COF membrane with switchable transport performance. Consequently, the COF membrane can achieve the controllable and switchable separation of light oil/water mixture, heavy oil/water mixture, water-in-oil emulsion, and oil-in-water emulsion with high separation efficiency and permeance. This intelligent COF membrane with the underwater superoleophobic and underoil superhydrophobic properties will greatly enrich the application field of COFs and open up new prospects for designing more novel materials in controllable free oil/water mixture separation and on-demand oil/water emulsion separation. [ABSTRACT FROM AUTHOR]