Sulfonated Sub-1-nm Metal-Organic Framework Channels with Ultrahigh Proton Selectivity

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Biological proton channels exhibit sub-1-nm pores with exceptional proton selectivity.
• Developing artificial analogues is crucial for advanced separation science.
• Metal-organic frameworks (MOFs) offer tunable structures for ion transport applications.

Purpose of the Study:

• To fabricate synthetic proton channels using sulfonated MOFs.
• To mimic the high proton selectivity of biological proton channels.
• To explore applications in selective ion conduction and separation.

Main Methods:

• Synthesis of sulfonated MOFs (UiO-66-X, X = SAG, NH-SAG, (NH-SAG)2) with sub-1-nm windows.
• Functionalization with a high density of sulfonic acid groups.
• Measurement of ion conductance and selectivity (H+, K+, Na+, Li+).

Main Results:

• UiO-66-X channels demonstrated high proton selectivity (H+ >> K+ > Na+ > Li+).
• Sulfonated MOF channels showed significantly enhanced proton selectivity compared to pristine MOFs.
• UiO-66-(NH-SAG)2 channels achieved ultrahigh selectivities (e.g., H+/Li+ up to ~100).

Conclusions:

• The narrow pore structure and high-density sulfonic acid groups in MOFs facilitate selective proton transport.
• These sulfonated MOF channels offer a promising platform for efficient ion separation.
• The study opens new avenues for designing functional MOF-based separation materials.