High Charge Carrier Mobility in Non-Conjugated 3D Covalent Organic Frameworks

Area of Science:

• Materials Science
• Organic Electronics
• Nanotechnology

Background:

• Charge transport in organic materials relies on π-conjugation, π-π stacking, and long-range order.
• Covalent organic frameworks (COFs) offer unique structural and electronic properties for conductive materials.
• Intraframework π-conjugation is typically crucial for enhancing charge carrier mobility in COFs.

Purpose of the Study:

• To investigate charge transport mechanisms in a novel 3D covalent organic framework (COF).
• To explore the role of interframework π-π stacking in charge mobility in the absence of intraframework π-conjugation.

Main Methods:

• Synthesis of Joa-COF-2, a 3D COF with an 11-fold interpenetrated dia topology.
• Characterization of the material's structure and electronic properties.
• Measurement of charge carrier mobility.

Main Results:

• Joa-COF-2 exhibits a high charge carrier mobility of 14 ± 1 cm² V⁻¹ s⁻¹.
• This mobility is achieved despite the lack of extended intraframework π-conjugation.
• Tight interframework π-π stacking was identified as the key factor enabling efficient charge transport.

Conclusions:

• Efficient charge transport in COFs can be achieved through strong interframework π-π stacking.
• Joa-COF-2 demonstrates a new design strategy for conductive organic materials.
• This finding challenges the necessity of intraframework π-conjugation for high charge mobility in certain COF architectures.