Charged Nanochannels in Covalent Organic Framework Membranes Enabling Efficient Ion Exclusion

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Controllable ion transport is vital for artificial and biological membranes.
• Covalent organic frameworks (COFs) offer tunable nanochannels for synthetic membranes.
• Existing COF membranes struggle with selective ion exclusion due to large nanochannels.

Purpose of the Study:

• To develop ionic COF membranes (iCOFMs) for controlled ion transport.
• To address the challenge of ion exclusion in COF-based membranes.
• To create membranes with high ion selectivity and water permeability.

Main Methods:

• Fabrication of iCOFMs with sulfonate groups on internal nanochannel surfaces.
• Investigation of ion transport mechanisms within charged nanochannels.
• Characterization of ion exclusion and water permeability properties.

Main Results:

• iCOFMs exhibit superior charge density due to arrayed sulfonate groups.
• Overlapping electrical double layers in nanochannels effectively block co-ions.
• Charge balance restrains counterion permeation, enabling selective ion exclusion.
• High water permeability is maintained alongside effective ion exclusion.

Conclusions:

• iCOFMs provide a novel platform for controllable ion transport.
• The charged nanochannel design overcomes limitations of traditional COF membranes.
• These membranes show promise for water purification, ionic separation, sensing, and energy conversion.