Covalent organic framework membranes for ion separation and ion-driven energy conversion

Area of Science:

• Materials Science
• Nanotechnology
• Separation Science

Background:

• Covalent organic framework (COF) membranes are evolving from porous solids to processable platforms.
• COFs offer precise control over nanochannel properties, unlike conventional polymer membranes.

Purpose of the Study:

• To review fabrication routes and membrane attributes of COF membranes.
• To organize advances in aqueous ion separation based on design logics.
• To connect transport principles to energy conversion applications.

Main Methods:

• Summarizing fabrication routes: interfacial growth, casting, layer assembly, composite architectures.
• Organizing ion separation advances by design logics for different ion targets.
• Connecting transport principles to energy conversion, including salinity-gradient, thermal, and photo fields.

Main Results:

• COF membranes enable tunable selectivity for monovalent/multivalent ions, monovalent cations, and anions (Cl-/SO42-).
• Sub-nanometre sieving and hydrogen-bond-assisted proton conduction achieve high proton/metal-ion selectivity.
• COF membranes show potential in salinity-gradient energy conversion.

Conclusions:

• Scalable fabrication with defect control and orientation is crucial for COF membrane translation.
• Mechanistic validation in complex electrolytes and process-relevant benchmarking are needed.
• COF membranes offer promising avenues for advanced ion separation and energy conversion.