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Two-Dimensional Cationic Covalent Organic Framework Membrane for Selective Molecular Sieving

Abstract

The search of new-type membrane materials with ideal molecular sieving caused widely interest in both academia and industry. Covalent organic frameworks (COFs) are excellent candidates for efficient molecular separation because of their well-defined pore structure and fine-tuning pore size. However, existing synthetic approaches of COFs mainly result in insoluble and unprocessable powder, which severely restrict their widespread applicability. In this work, a facile bottom-up interfacial crystallization approach to obtain a two-dimensional (2D) cationic COF, EB-COF:Br nanosheets is reported. Then a layer-by-layer restacking process is performed to fabricate continuous and dense 2D ionic COF membrane with tunable thickness by simple vacuum filtration. The 2D COF membrane shows much higher solvent permeability than graphene-oxide membranes and commercial nanofiltration membranes because of their high porosity. Moreover, due to there are abundant positive charge sites in pore walls, the EB-COF:Br membrane demonstrates highly selective sieving performance for dye molecules/ions with different charges and sizes. The EB-COF:Br membrane can efficiently reject ∼>98% of anionic dye molecules/ions, while maintaining high solvent permeability. The cationic 2D COF membrane far outperform other nanofiltration membranes in terms of excellent selective molecular/ionic sieving and superior solvent permeability. The result suggested that ionic COFs membrane can offer a new avenue for separation technology.

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Publication details

The article was received on 05 May 2018, accepted on 11 Jun 2018 and first published on 12 Jun 2018


Article type: Paper
DOI: 10.1039/C8TA04178D
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Two-Dimensional Cationic Covalent Organic Framework Membrane for Selective Molecular Sieving

    W. Zhang, L. Zhang, H. Zhao, B. Li and H. Ma, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C8TA04178D

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