Amphiphilic Zeolitic Imidazolate Framework for Improved CO₂ Separation in PIM-1 Mixed Matrix Membranes

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Mixed matrix membranes (MMMs) face challenges in filler-polymer compatibility, hindering efficient gas separation.
• ZIF-94 exhibits high CO2 affinity but requires improved integration into polymer matrices.
• Polymers of intrinsic microporosity (PIMs) are promising but can suffer from trade-offs between permeability and selectivity.

Purpose of the Study:

• To enhance filler-polymer compatibility in MMMs for improved CO2 separation.
• To modify ZIF-94 using the solvent-assisted ligand exchange (SALE) method to create ZIF-94-umIm.
• To evaluate the CO2 separation performance of MMMs incorporating the modified ZIF-94-umIm filler.

Main Methods:

• Solvent-assisted ligand exchange (SALE) was used to modify ZIF-94 with 2-undecylimidazolate (umIm).
• The modified ZIF-94 (ZIF-94-umIm) was incorporated into a polymer of intrinsic microporosity (PIM-1) matrix to form MMMs.
• Gas separation performance was tested using mixed gas (CO2/N2) at specified conditions, and thin film nanocomposite membranes were also prepared.

Main Results:

• The modified ZIF-94-umIm retained significant CO2 adsorption capacity.
• MMMs with 5 wt.% ZIF-94-umIm showed a ~70% increase in CO2 permeability and a ~10% increase in CO2/N2 selectivity compared to pristine PIM-1.
• Thin film nanocomposite membranes achieved a CO2/N2 selectivity of 23.5 at 2350 GPU of CO2.

Conclusions:

• The amphiphilic ZIF-94-umIm filler significantly improves the compatibility with PIM-1, leading to enhanced membrane performance.
• This MOF modification strategy offers a promising route for developing advanced materials for efficient CO2 capture technologies.
• Tailoring MOF fillers is a viable approach for optimizing membrane materials in gas separation applications.