Transformation between 2D and 3D Covalent Organic Frameworks via Reversible [2 + 2] Cycloaddition.
Thaksen Jadhav1, Yuan Fang1, Cheng-Hao Liu1
1Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada.
Journal of the American Chemical Society
|April 21, 2020
Summary
Researchers achieved the first reversible transformation between 2D and 3D covalent organic frameworks (COFs). Light triggers cross-linking into 3D COFs, while heating reverses it, altering material properties and conductivity.
Area of Science:
- Materials Science
- Polymer Chemistry
- Crystallography
Background:
- Covalent Organic Frameworks (COFs) offer tunable properties but transforming their dimensionality is challenging.
- Controlling the dimensionality of COFs impacts their mechanical, electronic, and conductive behaviors.
Purpose of the Study:
- To report the first transformation between 2D and 3D COFs.
- To investigate the reversibility of this transformation and its effect on material properties.
Main Methods:
- Absorption-edge irradiation of 2D poly(arylenevinylene) COFs to induce [2 + 2] cycloaddition.
- Thermal treatment (200 °C) to induce cycloreversion and recover 2D COFs.
- Characterization of mechanical, electronic, optical, and conductive properties.
Main Results:
- Successful light-induced transformation from 2D to 3D COFs via [2 + 2] cycloaddition.
- Reversible transformation achieved through heating, retaining COF crystallinity.
- Significant changes observed in UV-Vis absorption, luminescence, band structure, and acid-doping behavior.
- Demonstrated room-temperature ion conductivity (1.8 × 10-4 S/cm for 2D, 3.5 × 10-5 S/cm for 3D) and proton conductivity (1.7 × 10-2 S/cm for 2D, 2.2 × 10-3 S/cm for 3D).
Conclusions:
- Dimensionality transformation in COFs is achievable through reversible photo- and thermal-induced reactions.
- This transformation offers a new pathway to tune COF properties for potential applications in energy storage and electronics.
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