Single Na- and K-Ion-Conducting Sulfonated -NH-Linked Covalent Organic Frameworks

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Developing cost-effective and sustainable energy storage solutions is crucial.
• Nonlithium ion-based solid electrolytes are essential for this advancement.
• Covalent organic frameworks (COFs) offer tunable structures for ion conduction.

Purpose of the Study:

• To synthesize and characterize novel sulfonated -NH-linked COFs for sodium (Na+) and potassium (K+) ion conduction.
• To evaluate the ionic conductivity and activation energy of these COFs as solid electrolytes.
• To explore the potential of these COFs in sustainable energy storage applications.

Main Methods:

• One-step synthesis of two classes of sulfonated COFs: i-COF-2 and i-COF-3.
• Characterization of ionic conductivity at room temperature without additional salt or solvent.
• Measurement of activation energies for ion transport within the COF structures.

Main Results:

• i-COF-2 (Na/K) and i-COF-3 (Na/K) exhibited high ionic conductivities at room temperature (e.g., up to 3.17 × 10⁻⁴ S cm⁻¹ for i-COF-2 (Na)).
• Low activation energies were recorded (0.21 eV for i-COF-2, 0.24-0.25 eV for i-COF-3), indicating efficient ion transport.
• The COFs demonstrated intrinsic framework stability and required no additional salt or solvent for conduction.

Conclusions:

• The synthesized sulfonated COFs (i-COF-2 and i-COF-3) are promising solid electrolytes for Na+ and K+ conduction.
• Their high ionic conductivity, low cost, and stability support their use in sustainable energy storage.
• These materials pave the way for next-generation nonlithium-ion batteries and energy devices.