3D Imaging Reveals Widespread Stacking Disorder in Single Crystal 2D Covalent Organic Frameworks
Priti Kharel1, Patrick T Carmichael2, Anusree Natraj3
1Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States.
Journal of the American Chemical Society
|March 31, 2025
Summary
Layered 2D covalent organic frameworks (COFs) exhibit significant stacking disorder, distorting their 3D pore structure. This finding challenges assumptions and highlights the need for controlling 3D structures in COF materials.
Area of Science:
- Materials Science
- Nanotechnology
- Chemistry
Background:
- Two-dimensional (2D) covalent organic frameworks (COFs) are known for tunable porosity.
- Understanding the three-dimensional (3D) pore structure arising from interplanar stacking in 2D COFs is crucial but challenging.
Purpose of the Study:
- To investigate the interplanar stacking and 3D pore structure of single-crystalline 2D COF particles.
- To reveal the extent and nature of stacking disorder in imine-linked COFs.
Main Methods:
- Utilized scanning transmission electron microscopy (STEM).
- Employed ptychography, a 3D angstrom-scale imaging technique.
- Studied single-crystalline imine-linked 2D COF TAPB-DMPDA.
Main Results:
- Identified widespread stacking disorder beyond angstrom-level variations.
- Observed interplanar shifts up to half a unit cell and nanoscale stacking/tilt inhomogeneities.
- 3D visualizations confirmed distortion of pore channels due to stacking disorder.
Conclusions:
- Even high-quality 2D COFs exhibit significant stacking disorder.
- This disorder profoundly impacts potential applications of COFs.
- Development of strategies to control 3D structures in COFs is essential.
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