Controlled Covalent Functionalization of ZIF-90 for Selective CO₂ Capture & Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Mixed Matrix Membranes (MMMs) are crucial for gas separations, with porous metal-organic frameworks (MOFs) enhancing their performance.
• Zeolitic imidazolate frameworks (ZIF-90) offer advantageous structural and chemical properties for fabricating high-performance MMMs.

Purpose of the Study:

• To develop and investigate controlled post-synthetic modifications (PSM) of ZIF-90 using ethanolamine for improved CO2 capture and separation.
• To evaluate the performance of Polyetherimide (PEI) MMMs incorporating modified ZIF-90 (50-PSM-ZIF-90) compared to pure PEI and unmodified ZIF-90 MMMs.

Main Methods:

• Fabrication of PEI MMMs incorporating ZIF-90 and 50-PSM-ZIF-90.
• Characterization of physical and chemical properties of ZIF-90 and modified ZIF-90.
• Evaluation of membrane performance through gas permeability tests (H2, CO2, O2, CH4, C2H6, C3H8, N2) and selectivity analysis.

Main Results:

• The permeability order across membranes was P(H2) > P(CO2) > P(O2) > P(CH4) > P(C2H6) > P(C3H8) > P(N2), indicating kinetic gas diffusion as the primary transport mechanism.
• The 50-PSM-ZIF-90 PEI MMM demonstrated superior CO2/CH4 (20% increase) and CO2/N2 (26% increase) separation compared to ZIF-90 PEI MMM.
• Enhanced H2/O2 (15% increase) and H2/CH4 (9% increase) separation was observed for the 50-PSM-ZIF-90 PEI MMM over the ZIF-90 PEI MMM.

Conclusions:

• Controlled post-synthetic modification of ZIF-90 is an effective strategy to tune pore size and enhance gas transport properties.
• The developed 50-PSM-ZIF-90 PEI MMM shows significant promise for efficient CO2 capture and separation applications.
• This research highlights the potential of tailored MOFs in advanced membrane technology for industrial gas separation processes.