Bio-Inspired Synthetic Hydrogen-Bonded Organic Frameworks for Efficient Proton Conduction

Area of Science:

• Materials Science
• Chemistry
• Proton Conduction

Background:

• Hydrogen-bonded organic frameworks (HOFs) are promising proton conductors.
• A key challenge is balancing chemical stability with efficient proton conduction.

Purpose of the Study:

• To develop novel single-component HOFs inspired by lipid bilayers.
• To investigate the relationship between molecular structure and proton conductivity.

Main Methods:

• Synthesis of aminomethylphosphonic acid-derived HOFs with varying substituents.
• Stability testing in harsh acidic and alkaline conditions.
• Proton conductivity measurements under controlled temperature and humidity.
• Single-crystal structure analysis and density functional theory (DFT) calculations.

Main Results:

• Developed stable single-component HOFs resistant to degradation in strong acid/alkaline solutions for one month.
• Achieved a high proton conductivity of 4.2 × 10⁻³ S cm⁻¹ in a methyl-substituted HOF at 80°C and 98% RH.
• This conductivity is the highest reported for single-component HOFs and comparable to mixed-ligand systems.
• DFT and structural analysis revealed strengthened hydrogen bonds contribute to high conductivity.

Conclusions:

• Bio-inspired single-component HOFs can exhibit superior proton conductivity and stability.
• Molecular design, particularly charge-assisted hydrogen bonds, is crucial for optimizing proton conductor performance.
• Understanding structure-property relationships in HOFs is vital for developing advanced proton-conducting materials.