Flexible Amorphous Metal-Organic Framework Membranes With Local Order for Gas Separations

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Metal-organic framework (MOF) membranes offer potential for energy-efficient gas separations.
• However, their inherent brittleness limits their practical application in membrane modules.

Purpose of the Study:

• To engineer mechanically resilient and flexible MOF membranes.
• To overcome the processing limitations posed by the brittleness of crystalline MOFs.
• To achieve ultra-microporosity combined with polymer-like flexibility in MOF-based materials.

Main Methods:

• A symmetry-mismatch strategy involving electrified co-assembly of two structurally related MOFs.
• Utilizing MOFs with identical metal nodes and connectivity but distinct linkers and space groups.
• Employing preformed subunits to preserve local structural order while disrupting long-range periodicity.

Main Results:

• Successfully transformed brittle crystalline MOFs into amorphous membranes.
• Achieved an extraordinary combination of polymer-like flexibility and crystal-like ultra-microporosity.
• Demonstrated remarkable mechanical properties: flexural modulus of 234 MPa and curvature of 1000 m^-1.
• Exhibited impressive gas separation performance.

Conclusions:

• The symmetry-mismatch strategy is effective for creating mechanically robust amorphous MOF membranes.
• This approach overcomes a critical barrier to the real-world application of MOF membranes.
• Establishes a design principle for engineering high-performance amorphous materials with enhanced mechanical resilience.