Semiconducting Covalent Organic Frameworks Based on Spin-Delocalized Trioxotriangulene Neutral Radicals

Area of Science:

• Materials Science
• Organic Chemistry
• Polymer Science

Background:

• Electrically conductive two-dimensional covalent organic frameworks (2D COFs) are promising for electronics and energy storage.
• Current methods for high conductivity often require post-synthetic doping, which can degrade framework properties.
• Persistent neutral radical conductors offer an alternative by generating charge carriers intrinsically.

Purpose of the Study:

• To design and synthesize 2D COFs incorporating spin-delocalized neutral radicals.
• To investigate the electrical conductivity and electronic properties of these novel COFs.
• To establish a doping-free strategy for creating conductive crystalline organic frameworks.

Main Methods:

• Synthesis of imine-linked 2D COFs using trioxotriangulene (TOT) neutral radical derivatives.
• Complementary synthetic approaches were employed for framework construction.
• Characterization of the resulting crystalline framework (TOT-COF-H) for its structural and electronic properties.

Main Results:

• A highly crystalline 2D COF (TOT-COF-H) was successfully synthesized using TOT neutral radicals.
• The material exhibited semiconducting behavior with a room-temperature conductivity of 1.2 × 10⁻⁴ S cm⁻¹.
• A reduced band gap (1.09 eV) and low activation energy (0.24 eV) were observed, indicating efficient charge transport.

Conclusions:

• This study demonstrates a viable strategy for integrating neutral radical building blocks into 2D COFs.
• The developed COFs are intrinsically conductive, porous, and crystalline without extrinsic doping.
• This work paves the way for advanced organic electronic and energy storage devices.