Surface-Engineered Asymmetric Covalent Organic Framework Membranes with Polymers for Improved Ion Transport

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Highly oriented two-dimensional (2D) covalent organic frameworks (COFs) offer aligned channels for efficient ion transport.
• COFs are promising membrane materials for reverse electrodialysis (RED) systems.
• A key challenge is balancing ion conductivity and selectivity in ion-exchange membranes.

Purpose of the Study:

• To develop strategies for overcoming the conductivity-selectivity trade-off in COF membranes.
• To create asymmetric membrane properties by modifying COF surfaces with polymers.
• To enhance ion permeability and selectivity for improved RED performance.

Main Methods:

• Surface modification of 2D COFs with polymers to induce asymmetry.
• Characterization of anchored polyelectrolytes for charge density and hydrophilicity.
• Evaluation of ion transport, selectivity, and membrane resistance.
• Molecular dynamics simulations to understand polymer chain effects.

Main Results:

• Minimal polymer surface modification induced meaningful asymmetry in COF membranes.
• Anchored polyelectrolytes enhanced ion transport and reduced internal resistance.
• Longer polymer chains amplified the positive effects due to increased functional groups and counterion affinity.
• The polymer-integrated COF membrane showed over a 15-fold performance enhancement, stable for over 50 days.

Conclusions:

• Simple and subtle tuning of COF surface properties effectively modulates ion transport.
• Polymer integration offers a viable strategy to enhance COF membrane performance for osmotic power generation.
• Asymmetric membrane design is crucial for advancing RED technology.