Engineering Multiple Transport Pathways in MMMs Using COF@MOF Hierarchical Nanostructures for Efficient CO₂...

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Mixed-matrix membranes (MMMs) are crucial for efficient gas separation.
• Developing advanced fillers for MMMs is key to enhancing CO2 separation performance.
• Existing membranes often face limitations in permeability and selectivity.

Purpose of the Study:

• To engineer a novel hierarchical porous crystalline composite (COF@MOF) for CO2 separation.
• To fabricate polyethylene oxide (PEO)-based MMMs incorporating the COF@MOF filler.
• To investigate the synergistic effects of the composite filler on membrane performance.

Main Methods:

• Synthesized a hierarchical composite of covalent organic framework (COF, TpPa-1) within amino-functionalized zeolitic imidazolate framework (ZIF, NH2-ZIF-8).
• Fabricated PEO-based MMMs using the in situ grown TpPa-1@NH2-ZIF-8 composite nanosheets as fillers.
• Utilized UV cross-linking for membrane fabrication and characterized the MMMs' gas separation performance.

Main Results:

• The PEO/NH2-ZIF-8@TpPa-1 MMMs exhibited a CO2 permeability of 760.85 Barrer, a 292% increase over pristine PEO.
• CO2/N2 selectivity reached 65.09, a 146% enhancement compared to the PEO membrane.
• The hierarchical structure facilitated synergistic effects including molecular sieving, enhanced adsorption, and facilitated transport.

Conclusions:

• The COF@MOF hierarchical structure offers a multimechanism synergistic strategy for superior gas separation.
• This approach transcends conventional solution-diffusion mechanisms, significantly boosting separation efficiency.
• The developed MMMs show exceptional performance and potential for practical gas separation applications.