Room-temperature superprotonic conductivity in COOH-functionalized multicomponent covalent organic frameworks.

Area of Science:

• Materials Science
• Chemistry
• Chemical Engineering

Background:

• Proton conductivity in solid materials is vital for energy applications.
• Hydrogen bonding (H-bonding) networks within material pores are key for efficient proton transport.
• Covalent organic frameworks (COFs) are a promising class of materials for proton conduction.

Purpose of the Study:

• To synthesize and evaluate chemically stable, carboxylic acid-functionalized 2D microporous COFs for proton conductivity.
• To investigate the role of carboxylic acid groups and H-bonding in enhancing proton transport.
• To establish a general strategy for developing high-performance proton-conducting COFs.

Main Methods:

• Synthesis of a carboxylic acid-functionalized COF (Qy-COOH) via the Doebner multicomponent reaction (MCR).
• Synthesis of a control COF (Qy-H) lacking -COOH functionality via an MC Domino reaction.
• Measurement and comparison of proton conductivity for synthesized COFs and an imine-based COF.

Main Results:

• The Qy-COOH COF exhibited significantly enhanced proton conductivity (10⁻² S cm⁻¹).
• Strong H-bonding interactions between water and -COOH groups were identified as the cause of enhanced conductivity.
• The Qy-H COF showed lower conductivity (10⁻⁵ S cm⁻¹), and an imine-based COF showed 10⁻⁶ S cm⁻¹.

Conclusions:

• A general strategy for achieving efficient proton conduction in 2D -COOH-functionalized COFs was demonstrated.
• Superprotonic conductivity was achieved at room temperature without additives.
• The MCR-COF design approach offers a promising pathway for developing stable, high-performance proton-conducting materials.