Scalable Art-Inspired Tessellated Covalent Organic Framework Membranes Enable Highly Selective Ion Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Covalent organic frameworks (COFs) offer tunable structures for separation but face challenges in pore size control and membrane integration.
• Fabricating COF membranes with precise angstrom-scale pores remains a significant hurdle for advanced separations.

Purpose of the Study:

• To synthesize a substoichiometric aminal-linked COF with angstrom-scale pores.
• To develop a covalent tessellation strategy for defect-free COF membranes.
• To evaluate the performance of these membranes in molecular and ionic separations and assess scalability.

Main Methods:

• Synthesis of a substoichiometric aminal-linked COF with ~5 Å pore size.
• Development of a covalent tessellation strategy via interfacial polymerization.
• Fabrication and characterization of tessellated COF (tCOF) membranes.

Main Results:

• The tCOF membranes exhibit ultra-microporous structures.
• Achieved high water permeance (10.2 L m⁻² h⁻¹ bar⁻¹) and near-perfect Na₂SO₄ rejection (99.4%).
• Demonstrated exceptional Cl⁻/SO₄²⁻ selectivity (1,090) and scalability to roll-to-roll format (30 cm width).

Conclusions:

• The covalent tessellation methodology enables the fabrication of scalable, defect-free COF membranes with angstrom-scale pores.
• These tCOF membranes show great promise for highly selective separations and resource recovery, such as producing high-purity NaCl.
• The study opens new avenues for designing advanced COF-based separation technologies.