Covalent/metal-organic framework membranes with tailored pore functionality for accurate ion separation.

Area of Science:

• Materials Science and Engineering
• Chemical Engineering
• Environmental Science

Background:

• Ion-selective membranes are crucial for water resource management and critical metal recovery.
• Conventional polymer membranes face a permeability-selectivity trade-off due to disordered pore structures.
• Understanding ion transport in sub-nanometer channels of conventional membranes is challenging.

Purpose of the Study:

• To review recent advancements in ion-selective membranes utilizing covalent organic frameworks (COFs) and metal-organic frameworks (MOFs).
• To elucidate ion-differentiation mechanisms within the sub-nanochannels of these crystalline framework materials.
• To highlight pore engineering design principles for enhanced selective ion transport.

Main Methods:

• Critical review of literature on COF and MOF-based ion-selective membranes.
• Analysis of ion-differentiation mechanisms: size exclusion, electrostatic interactions, and chemical binding.
• Examination of pore engineering strategies, including ion-binding moieties, pore dimensions, charge, and asymmetric structures.

Main Results:

• COFs and MOFs provide ordered pore architectures, overcoming the limitations of conventional membranes.
• Pore engineering of COFs and MOFs enables tunable microenvironments for precise ion selectivity.
• Specific design principles enhance selective ion transport through tailored pore characteristics.

Conclusions:

• Crystalline framework materials like COFs and MOFs are highly promising for next-generation ion-selective membranes.
• Further research is needed for on-demand design and fabrication of these advanced membranes.
• These materials hold significant potential for applications in water treatment and resource recovery.