Precision-Engineered Crystalline Covalent Organic Framework Membranes with Staggered ABC Stacking for...

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Covalent organic framework (COF) membranes show promise for water separations but face challenges with large pores and low crystallinity.
• These limitations hinder their effectiveness in demanding applications like water desalination.

Purpose of the Study:

• To develop a novel strategy for engineering ultramicroporous and highly crystalline COF membranes.
• To overcome the performance limitations of existing COF membranes in aqueous separations, particularly desalination.

Main Methods:

• An acid-modulated interfacial synthesis (AMIS) strategy was employed using acetic acid to control the reaction-diffusion kinetics of aliphatic linkers.
• Detailed mechanistic investigations, including experimental validation and simulations, were used to understand the synthesis process and membrane structure.
• The synthesis yielded a stripe-patterned Turing architecture with defect self-correction, resulting in high film crystallinity.

Main Results:

• The engineered aliphatic ODH-COF membranes exhibited a unique ABC stacking mode and sub-6-Å pore apertures.
• These membranes achieved a record 99.7% NaCl rejection and a water permeance of 0.82 L m⁻² h⁻¹ bar⁻¹.
• The membranes demonstrated robust fouling resistance and long-term stability.

Conclusions:

• The AMIS strategy successfully produced highly crystalline, ultramicroporous COF membranes with exceptional desalination performance.
• This advancement significantly enhances COF membrane technology for sustainable and efficient water management solutions.
• The developed membranes surpass current state-of-the-art COF membranes for pressure-driven separation processes.