Triple Isomerism in 3D Covalent Organic Frameworks
Xiaohan Wang1,2, Yuki Wada3, Terumasa Shimada3
1Laboratory for Zero-Carbon Energy, Institute of Innovative Research, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan.
Journal of the American Chemical Society
|January 11, 2024
Summary
Researchers discovered three framework isomers in 3D covalent organic frameworks (COFs) for the first time. This finding expands the diversity of COFs, which are crucial for various applications.
Area of Science:
- Materials Science
- Crystallography
- Supramolecular Chemistry
Background:
- Isomerism in covalent organic frameworks (COFs) is a poorly understood phenomenon.
- Previous studies have not explored the possibility of multiple framework isomers within COFs.
Purpose of the Study:
- To demonstrate the existence of triple framework isomerism in 3D COFs for the first time.
- To investigate the structural diversity and formation pathways of these isomers.
- To expand the application potential of COFs.
Main Methods:
- Synthesis of 3D COFs using a tetrahedral building block with a flexible junction and a linear building block with PEO side chains.
- Structural characterization using X-ray diffraction (including Rietveld analysis for the qtz topology).
- Spectroscopic analysis (FT-IR, solid-state NMR) and energy calculations.
Main Results:
- Successfully synthesized three distinct framework isomers (polymorphs) of 3D COFs from the same building blocks.
- Identified unprecedented triple isomerism, including noninterpenetrated dia, qtz, and 3-fold interpenetrated dia-c3 nets.
- Confirmed the qtz topology as a kinetic isomer, evidenced by interisomer transition.
- Obtained isomers as large crystals (>10 μm) with distinct shapes but identical spectra.
Conclusions:
- The reticulation of flexible building blocks is an effective strategy to achieve significant diversity in 3D COFs.
- The discovery of triple isomerism broadens the scope of COF design and potential applications.
- This work provides a new perspective on controlling framework topology and isomerism in porous materials.
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