Electrosynthesis of Ionic Covalent Organic Frameworks for Charge‐Selective Separation of Molecules

Covalent organic frameworks (COFs) have emerged as potent material platforms for engineering advanced membranes to tackle challenging separation demands. However, the synthesis of COF membranes is currently hampered by suboptimal productivity and harsh synthesis conditions, especially for ionic COFs with perdurable charges. Herein, ionic COFs with charged nanochannels are electrically synthesized on conductive supports to rapidly construct composite membranes for charge-selective separations of small molecules. The intrinsic charging nature and strong charge intensity of ionic COFs are demonstrated to collectively dominate the membrane growth. Spontaneous repairing to diminish defects under the applied electric field is observed, in favor of generating well-grown COF membranes. Altering electrosynthetic conditions realizes the precise control over the membrane thickness and thus the separation ability. Electrically synthesized ionic COF membranes exhibit remarkable molecular separation performances due to their relatively ordered and charged nanochannels. With these charge-selective pathways, the membranes enable the efficient sieving of charged and neutral molecules with analogous structures. This study reveals an electrical route to synthesizing COF thin films, and showcases the great potential of ionic nanochannels in precise separation based on charge selectivity.