Reversible pH-Gated MXene Membranes with Ultrahigh Mono-/Divalent-Ion Selectivity.

Area of Science:

• Materials Science
• Nanotechnology
• Separation Science

Background:

• Artificial ion channel membranes are crucial for water treatment, nanofluidics, and energy conversion.
• Developing membranes with both reversible ion-gating and high ion selectivity remains a significant challenge.

Purpose of the Study:

• To construct a smart MXene-based membrane with reversible ion-gating and ultrahigh metal ion selectivity.
• To mimic the functionality of biological ion channels in an artificial system.

Main Methods:

• Fabrication of a MXene-based membrane functionalized with p-phenylenediamine (MLM-PPD).
• Characterization of the membrane's subnanochannels and ion transport properties.
• Investigation of pH-dependent ion gating and metal ion selectivity using experimental and theoretical approaches.

Main Results:

• The MLM-PPD membrane exhibits stable, aligned 2D subnanochannels.
• Demonstrated reversible Mg2+ gating with a pH-switching ratio up to 100.
• Achieved ultrahigh mono/divalent metal ion selectivity (e.g., K+/Mg2+ up to 1243.8), surpassing existing membranes.
• Theoretical and experimental data indicate steric hindrance and PPD-ion interactions are key to selectivity.

Conclusions:

• The developed MLM-PPD membrane offers a novel strategy for artificial ion channel membranes.
• The membrane possesses reversible ion-gating and exceptional ion selectivity, comparable to biological channels.
• This work paves the way for advanced applications in water purification, ion separation, and energy conversion.