Charge- and Size-Selective Ion Sieving Through Ti3C2Tx MXene Membranes

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Two-dimensional (2D) materials like MXenes offer unique properties for separation technologies.
• Developing freestanding membranes with controlled thickness is crucial for advanced filtration.

Purpose of the Study:

• To assemble nanometer-thin 2D Ti3C2Tx (MXene) sheets into membranes for selective ion and molecule rejection.
• To investigate the separation performance of MXene membranes with varying thicknesses.

Main Methods:

• Assembly of 2D Ti3C2Tx (MXene) nanosheets into freestanding and supported membranes.
• Characterization of membrane properties including thickness, flexibility, mechanical strength, hydrophilicity, and electrical conductivity.
• Evaluation of water flux and ion sieving capabilities using salt solutions.

Main Results:

• MXene membranes with controllable thicknesses (hundreds of nanometers to several micrometers) were successfully fabricated.
• Micrometer-thick membranes exhibited high mechanical strength, flexibility, and ultrafast water flux (37.4 L/(Bar·h·m(2))).
• Selective ion rejection was observed, with cations differing in permeation based on hydration radius and charge relative to MXene interlayer spacing (~6 Å).

Conclusions:

• 2D Ti3C2Tx (MXene) membranes are promising for separation applications due to their tunable properties.
• The membranes demonstrate efficient and selective ion separation, influenced by ion hydration and charge.
• These findings pave the way for developing advanced separation membranes from 2D carbides.