Tuning Pore Size in Graphene in the Angstrom Regime for Highly Selective Ion-Ion Separation

Area of Science:

• Materials Science
• Nanotechnology
• Separation Science

Background:

• Two-dimensional materials like graphene offer potential for ion-selective membranes due to their angstrom-scale pores.
• A major challenge is creating crack-free macroscopic graphene membranes with tunable, selective pores for ion separation.

Purpose of the Study:

• To develop a tool for precisely tuning angstrom-scale pore sizes in single-layer graphene.
• To create graphene membranes with high ion selectivity and minimize non-selective larger pores.

Main Methods:

• Development of an angstrom-scale pore size tuning tool for single-layer graphene.
• Fabrication of centimeter-scale porous graphene membranes.
• Ion diffusion studies to analyze ion-pore interactions and selectivity.

Main Results:

• Achieved high density of ion-selective pores (3.5–8.5 Å) while minimizing pores >10 Å.
• Demonstrated high selectivity between monovalent and bivalent ions and near-complete blockage of ions >9.0 Å hydration diameter.
• Observed temperature-dependent selectivity reversal for K+/Li+ ions, linked to dehydrated ion size.

Conclusions:

• The developed pore tuning tool enables precise control over graphene pore sizes for advanced membrane applications.
• Precisely engineered porous 2D materials show significant promise for highly selective solute-solute separation.