Rapid synthesis of highly-crystalline and dense covalent organic framework membranes via regulating the nucleation, growth and assembly processes

Highly-crystalline and defect-free covalent organic framework (COF) membranes are highly desired for efficient molecular separations. However, their rapid and facile synthesis remains challenging‌. The formation of COF membranes closely relates to the nucleation, growth and assembly processes of crystals. Herein, we report a universal strategy for rapidly synthesizing highly-crystalline and dense 3D/2D COF membranes via rationally regulating the nucleation, growth and assembly processes. This strategy employs the inhibitor of aniline and the controlled released catalyst to moderate nucleation rate, avoiding fast formation of amorphous particles. Meanwhile, aniline is gradually removed under the controlled heating and solvent vapor exchange, driving the growth and subsequent assembly of COF crystals into continuous films. The morphological changes of COF films with aniline dosage verified the regulation mechanism. Under optimal condition, highly-crystalline and dense membranes could be synthesized in 45 min. Typically, the synthesized COF-300/nylon membrane demonstrated 100 % rejection to Congo Red, Brilliant Blue R250 (BB), Direct Blue15 and Alcian Blue with permeance higher than 500 L m −2 h −1 MPa −1 . And all the five prepared 3D/2D COF membranes exhibited 100 % rejection to BB with high permeance. This work also provides a mechanistic basis for the rational design and synthesis of high-quality COF membranes. • Universal strategy for rapidly synthesizing crystalline and dense COF membranes. • Rational regulation of nucleation, growth and assembly processes for synthesis. • The prepared membranes exhibited stable and superior nanofiltration performance.