Substituent-Induced Secondary Interactions Reprogram Ion Permselectivity in Cationic Covalent Organic Framework
Jiaming Yi1, Zhiwei Xing1, Zhuozhi Lai1
1Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, China.
Angewandte Chemie (International Ed. in English)
|February 2, 2026
Summary
Neutral substituents reprogram ion selectivity in cationic covalent organic framework (COF) membranes by introducing secondary interactions. This enables tunable, reversible ion transport for advanced separation and energy harvesting technologies.
Area of Science:
- Materials Science
- Chemical Engineering
- Nanotechnology
Background:
- Precise control over ion permselectivity in synthetic membranes is essential for separation and energy applications.
- Covalent organic frameworks (COFs) offer tunable properties but require methods for precise ion transport modulation.
- Understanding the interplay between framework charge and local chemical environment is key to designing advanced membranes.
Purpose of the Study:
- To demonstrate how neutral substituents can reprogram the ion selectivity of cationic COF membranes.
- To investigate the role of secondary local interactions in modulating Coulombic forces for ion transport.
- To achieve programmable and reversible ion permselectivity for enhanced energy harvesting.
Main Methods:
- Systematic variation of substituents (hydroxyl, methoxy) on 1,3,5-trialdehyde linkers in triaminoguanidinium-based COFs.
- Characterization of COF membranes to analyze the impact of substituents on ion transport properties.
- Measurement of ionic thermoelectric performance under a temperature gradient.
Main Results:
- Neutral substituents introduced secondary interactions that competed with long-range Coulombic forces.
- Hydroxyl substitution inverted the surface potential and switched transport from anion- to cation-selective.
- Methoxy substitution weakened Coulombic interactions, enhancing anion selectivity.
- Achieved record ionic thermoelectric performance (25.9 W m-2 single, 39.1 W m-2 stacked).
Conclusions:
- Substituent-mediated secondary interactions provide a general strategy for programming ion transport in COFs.
- This approach enables tunable and reversible ion permselectivity without altering the permanent framework charge.
- The findings bridge biological selectivity principles with adaptive COF membrane design for energy and separation technologies.
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