Merocyanine-Linked Zwitterionic Covalent Organic Frameworks
Zhechang He1, Cheng-Hao Liu1, Ting Yu1
1Department of Chemistry, McGill University, 801 Sherbrooke Street W, Montréal, Quebec H3A 0B8, Canada.
Journal of the American Chemical Society
|February 26, 2026
Summary
We synthesized novel zwitterionic merocyanine-based covalent organic frameworks (COFs). These materials exhibit tunable properties, including reversible color changes and pore size adjustments based on medium polarity.
Area of Science:
- Materials Science
- Organic Chemistry
- Supramolecular Chemistry
Background:
- Merocyanines are π-conjugated systems known for their zwitterionic nature and optoelectronic properties.
- Covalent Organic Frameworks (COFs) offer tunable structures and functionalities for advanced applications.
Purpose of the Study:
- To synthesize the first merocyanine-based C=C-linked COFs.
- To investigate the optoelectronic properties and stimuli-responsive behavior of these novel COFs.
Main Methods:
- Condensation reaction between N-alkylcollidinium salts and hydroxytrimesic aldehyde.
- Characterization using UV-Vis spectroscopy, DFT calculations, and time-resolved spectroscopy.
- Preparation of thin films via heterogeneous nucleation.
Main Results:
- Successful synthesis of stable, zwitterionic merocyanine-based COFs with charge-transfer absorption up to 850 nm.
- Demonstrated pore contraction/expansion in response to medium polarity, leading to macroscopic changes.
- Observed reversible color transitions (black to yellow) upon protonation.
- DFT calculations indicated omnidirectional π-conjugation and large band dispersions.
- Thin films exhibited vertical 2D sheet orientation, stimulated emission, and long-lived excited states.
Conclusions:
- The developed merocyanine-based COFs represent a new class of functional materials.
- Their stimuli-responsive behavior and optoelectronic properties hold promise for applications in sensors and optoelectronics.
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