Facile Size-Selective Defect Sealing in Large-Area Atomically Thin Graphene Membranes for Sub-Nanometer Scale...

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Atomically thin graphene membranes offer ideal properties for separations due to subnanometer pores.
• Larger defects and differential etching limit the performance of graphene-based membranes.
• Precise control over pore size and defect sealing is crucial for advanced membrane applications.

Purpose of the Study:

• To develop a scalable method for creating defect-free, nanoporous graphene membranes with high performance.
• To demonstrate the ability of size-selective interfacial polymerization to seal larger defects while preserving subnanometer pores.
• To evaluate the separation performance of the synthesized membranes for water, ions, and organic molecules.

Main Methods:

• Fabrication of high-density subnanometer pores in graphene via low-temperature growth and UV/ozone oxidation.
• Application of size-selective interfacial polymerization to seal macroscopic tears and larger defects (>0.5 nm).
• Characterization of synthesized centimeter-scale nanoporous atomically thin membranes (NATMs) and assessment of their separation performance using forward osmosis.

Main Results:

• Achieved high-density (4-5.5 × 10^12 cm^-2) subnanometer pores in graphene.
• Successfully sealed larger defects and macroscopic tears using interfacial polymerization, preserving smaller pores.
• Demonstrated high water permeance (∼23× higher than commercial membranes) and excellent rejection rates for salt ions (>97%) and organic molecules (∼100%).

Conclusions:

• Size-selective interfacial polymerization is an effective strategy for fabricating high-performance graphene membranes.
• The developed NATMs show significant potential for advanced separation applications, including water purification and desalination.
• This scalable method overcomes limitations of previous graphene membrane fabrication techniques.