Mixed-dimensional COF membrane towards fast organic solvent nanofiltration

Mixed-dimensional COF membrane is constructed with 2D COF nanosheet and 1D COF nanotube. • 2D COF nanosheets served as the building block to provide in-plane mass transfer channels • 1D COF nanotube acts as intercalator to construct additional interlayer mass transfer channels. • The membrane exhibits high permeance for solvents and high rejection for dyes. • The membrane shows stable separation performance in long-term test. Covalent organic framework (COF) membrane holds significant potential in organic solvent nanofiltration (OSN), and the regulation of mass transport channels in covalent organic framework nanosheets (CON) assembled membrane is the key for the high separation performance. Herein, we utilized two-dimensional (2D) CON and one-dimensional (1D) COF nanotube (COF-NT) to prepare mixed-dimensional CON/COF-NT membrane for fast OSN. 2D CON served as the building block of the membrane to provide in-plane mass transfer channels and 1D COF-NT acted as intercalator to construct additional interlayer mass transfer channels, thus constructing the stable mixed-dimensional channels to enhance the membrane permeance while ensuring its high selectivity. As a result, CON/COF-NT membrane exhibited high permeance of 293 L m −2  h −1  bar −1 , 354 L m −2  h −1  bar −1 and 366 L m −2  h −1  bar −1 for water, acetone and acetonitrile, respectively, while maintaining high rejection rates of 96.0%, 98.6% and 100% for Methyl blue, Congo red and Alcian blue 8GX, respectively. Furthermore, compared with using 1D cellulose nanofiber as the intercalator, CON/COF-NT membrane maintained more stable water permeance with transmembrane pressure ranging from 0.5 bar to 3.0 bar, and separation performance for the 7-day long-term test. This study provides a novel approach to regulating the mass transport channels in COF membrane to achieve fast OSN. Mixed-dimensional COF membrane is prepared using two-dimensional COF nanosheet and one-dimensional COF nanotube as the building block to provide in-plane mass transfer channels and intercalator to construct additional interlayer mass transfer channels, respectively, leading to fast organic solvent nanofiltration. Download: Download high-res image (161KB) Download: Download full-size image