Lamellar-Confinement-Induced ZIF-67 Nanosheet Mixed Matrix Membranes for Enhanced CH₄/N₂ Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Mixed-matrix membranes (MMMs) for gas separation face challenges due to poor interfacial compatibility between metal-organic framework (MOF) fillers and polymer matrices.
• Traditional isotropic MOFs limit the performance of MMMs.

Purpose of the Study:

• To develop a lamellar-confinement strategy for synthesizing 2D ZIF-67 nanosheets (ZIF-67_ns).
• To improve the interfacial compatibility and gas separation performance of MMMs.

Main Methods:

• Utilized a cetyltrimethylammonium bromide (CTAB) liquid crystal template with water as a cosolvent to synthesize 2D ZIF-67_ns.
• Controlled crystal growth along the c-axis and promoted lateral expansion for nanosheet formation.
• Incorporated ZIF-67_ns into a styrene-ethylene-butylene-styrene (SEBS) copolymer matrix to create MMMs.

Main Results:

• Synthesized ZIF-67_ns with high crystallinity, hexagonal morphology (44.3 nm thickness), and high specific surface area (1029.3 m²/g).
• Fabricated MMMs showed a ~1050% increase in CH₄ permeability (from 24.3 to 278.4 barrer) at 30 wt% loading.
• Achieved a CH₄/N₂ selectivity of 5.15, demonstrating enhanced gas separation performance.

Conclusions:

• The lamellar-confinement strategy effectively produces 2D MOFs with enhanced properties.
• Morphology-controlled 2D MOFs significantly improve interfacial contact and performance in MMMs for gas separation.
• This approach holds significant potential for developing highly efficient gas separation membranes.