Polycrystalline Covalent Organic Frameworks: Multiscale Structural Insights from Morphological Diversity to Dynamic
Juan Li1, Yukun Liu1, Xuezeng Tian2
1Institute of Crystalline Materials, Shanxi University, Taiyuan 03006, China.
Journal of the American Chemical Society
|July 18, 2025
Summary
Covalent organic frameworks (COFs) are porous materials whose polycrystalline structures are poorly understood. This study reveals diverse morphologies and assembly mechanisms in polycrystalline COFs, offering insights for improved synthesis and property exploration.
Area of Science:
- Materials Science
- Chemistry
- Nanotechnology
Background:
- Covalent organic frameworks (COFs) are crystalline porous materials with significant potential.
- The polycrystalline nature of COFs often obscures their detailed structure.
- Understanding COF structure is crucial for correlating properties and applications.
Purpose of the Study:
- To investigate the complex structures of polycrystalline covalent organic frameworks.
- To reveal the coexistence of different morphologies and their behaviors.
- To elucidate novel assembly mechanisms in COF formation.
Main Methods:
- High-resolution transmission electron microscopy (HRTEM) for visualization.
- Analysis of nanoparticle fusion and amorphous-phase-interconnected crystalline domains.
- Characterization of polygon and channel structures within COFs.
Main Results:
- Identified four distinct morphologies: nanoparticle aggregates, nanorod aggregates, ultrathin nanosheets, and parasitic fusion entities.
- Visualized diverse polygons, channels, and their contents, along with boundaries and unstructured complements.
- Uncovered new assembly mechanisms, including covalent-bond-mediated nanoparticle fusion.
Conclusions:
- Provided a realistic, multi-scale picture of polycrystalline framework structures.
- Established new insights into COF assembly mechanisms.
- Laid the foundation for synthesizing high-quality COFs and exploring their functions.
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