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Uncertainty in Composite Membranes: From Defect Engineering to Film Processing
Justin J Teesdale1, Moonjoo Lee1, Ruoxin Lu1
1Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts02139, United States.
Journal of the American Chemical Society
|December 28, 2022
Summary
Defect engineering in metal-organic frameworks (MOFs) impacts composite membrane performance. Low-porosity MOFs unexpectedly enhanced CO2/CH4 separation, but decreased sorption capacity offset diffusion gains, highlighting the need for replicate experiments.
Area of Science:
- Materials Science
- Chemical Engineering
- Nanotechnology
Background:
- Composite membranes with metal-organic frameworks (MOFs) show promise for gas separations.
- Reproducibility issues in MOF synthesis and membrane fabrication hinder commercialization.
- The impact of MOF crystal defects on membrane transport properties is poorly understood.
Purpose of the Study:
- To investigate the effect of MOF porosity and defects on composite membrane performance.
- To establish reliable structure-property correlations for MOF-polymer membranes.
- To address uncertainties in MOF synthesis and membrane manufacturing for improved reproducibility.
Main Methods:
- Synthesized two UiO-66-NH2 MOF samples with controlled, differing porosities.
- Fabricated composite membranes using 6FDA-Durene polymer and the synthesized MOFs.
- Conducted light gas permeation and sorption measurements.
- Applied the Maxwell model for performance extrapolation.
Main Results:
- Low-porosity UiO-66-NH2 composites showed a small, unexpected CO2/CH4 performance enhancement.
- High-porosity MOFs exhibited a 50% decrease in sorption capacity, negating diffusion benefits.
- Replicate experiments revealed significant sample-to-sample variation, obscuring differences at low MOF loadings.
- Extrapolation using the Maxwell model showed considerable variability.
Conclusions:
- MOF defect engineering significantly influences composite membrane gas transport and sorption.
- Controlled synthesis and rigorous replicate testing are crucial for reliable MOF membrane development.
- Variability in MOF properties can mask performance enhancements, emphasizing the need for standardized protocols.
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