Laminated self-standing covalent organic framework membrane with uniformly distributed subnanopores for ionic and molecular sieving

Abstract

The preparation of subnanoporous covalent-organic-framework (COF) membranes with high performance for ion/molecule sieving still remains a great challenge. In addition to the difficulties in fabricating large-area COF membranes, the main reason is that the pore size of 2D COFs is much larger than that of most gas molecules and/or ions. It is urgently required to further narrow their pore sizes to meet different separation demands. Herein, we report a simple and scalable way to grow large-area, pliable, free-standing COF membranes via a onestep route at organic-organic interface. The pore sizes of the membranes can be adjusted from >1 nm to sub-nm scale by changing the stacking mode of COF layers from AA to AB stacking. The obtained AB stacking COF membrane composed of highly-ordered nanoflakes is demonstrated to have narrow aperture (∼0.6 nm), uniform pore distribution and shows good potential in organic solvent nanofiltration, water treatment and gas separation.

Novel Nanofluidic Cells Based on Nanowires and Nanotubes for Advanced Chemical and Bio-Sensing Applications

“…has greatly enriched and promoted the field of nanofluid ion transport [ 5 ]. Compared with nanopores or other nanofluidic channels, 2D nanofluidic channel systems with high flow rates are relatively easy and expandable to manufacture, which can be used for applications in bionic transmission and manipulation of ions, molecular screening, and energy conversion [ 6 , 7 , 8 ]. However, the currently reported research on the asymmetric ion transmission characteristics of the 2D nanofluidic homogeneous structure is still in its infancy, due to their problems of insufficient charge density and low rectification ratio [ 9 ].…”

Pore engineering of ultrathin covalent organic framework membranes for organic solvent nanofiltration and molecular sieving

“…20,21 They developed a solution-casting method to prepare relatively thick membranes out of these COF materials for OSN applications and the separation of nanoparticles. [22][23][24][25][26][27][28][29][30] We developed a Langmuir-Blodgett (LB) process to synthesize crystalline ultrathin COF membranes from 1,3,5-triformylphloroglucinol (TFP) and 9,9-dihexyluorene-2,7-diamine (DHF) which is also based on the stable b-ketoenamine linkage. 31 The TFP-DHF membrane showed a remarkably high solvent ux in the application of organic solvent nanoltration.…”

Screen printing directed synthesis of covalent organic framework membranes with water sieving property

“…(2) Interfacial polymerisation. [14][15][16][17][18][19][20] The monomers in two immiscible solvents counter diffuse to liquid-liquid or liquid-air interfaces and COF membranes are formed at these interfaces. This method can produce thin and free-standing membranes, but produced membranes are usually devoid of high compactness which leads to low separation performance.…”