Linkage conversions in single-crystalline covalent organic frameworks.
Baoqiu Yu1, Rui-Biao Lin2, Gang Xu3
1Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials, Department of Chemistry and Chemical Engineering, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing, China.
Nature Chemistry
|September 18, 2023
Summary
Researchers developed a flexible covalent organic framework (COF) with interpenetrated qtz topology. This material exhibits unique structural transformations and achieves high proton conductivity after phosphoric acid loading.
Area of Science:
- Materials Science
- Crystallography
- Polymer Chemistry
Background:
- Single-crystal X-ray diffraction is crucial for determining atomic structures but challenging for covalent organic frameworks (COFs), especially those undergoing post-synthetic modifications.
- Developing flexible COFs that maintain single-crystal integrity is essential for advanced characterization and functional applications.
Purpose of the Study:
- To synthesize a flexible COF with interpenetrated qtz topology suitable for single-crystal analysis.
- To investigate the material's flexibility, structural transformations, and potential for proton conductivity.
Main Methods:
- Synthesis of a flexible COF via polymerization of tetra(phenyl)bimesityl-based tetraaldehyde and tetraamine building blocks.
- Characterization using single-crystal X-ray diffraction to observe structural changes.
- Assessment of thermal expansion and solvent removal-induced transformations.
- Evaluation of redox-induced linkage conversions (imine to amine/amide) and proton conductivity measurements.
Main Results:
- A flexible COF with interpenetrated qtz topology was successfully synthesized.
- The material demonstrated significant anisotropic positive thermal expansion (αc = +491 × 10⁻⁶ K⁻¹) and structural transformation upon solvent removal.
- Single-crystal-to-single-crystal transformations were achieved through redox-induced imine linkage conversions.
- Phosphoric acid loading resulted in anhydrous proton conductivity up to 6.0 × 10⁻² S cm⁻¹.
Conclusions:
- The synthesized flexible COF enables single-crystal analysis and exhibits tunable structural properties.
- Redox-induced linkage conversions enhance material stability and open pathways for functional applications like proton conduction.
- This work presents a promising strategy for designing robust and adaptable COFs for advanced material applications.
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