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Tuning the Adsorption Selectivity of ZIF-8 by Amorphization
Qiang Ma1, Hua Jin1, Yanshuo Li1
1School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, 315211, P. R. China.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|July 12, 2020
Summary
Mechanically compressing ZIF-8 creates amorphous metal-organic frameworks (am MOFs) with enhanced gas adsorption and separation capabilities. These novel porous materials show improved selectivity for propylene/propane mixtures and potential in membrane applications.
Area of Science:
- Materials Science
- Chemical Engineering
- Nanotechnology
Background:
- Amorphous metal-organic frameworks (am MOFs) represent a novel class of porous hybrid materials.
- ZIF-8, a crystalline MOF, has shown promise in gas separation but can be further optimized.
- Developing materials with tailored porosity and structure is crucial for advanced separation technologies.
Purpose of the Study:
- To synthesize amorphous ZIF-8 (am ZIF-8) via mechanical compression.
- To investigate the structural changes and porosity of am ZIF-8.
- To evaluate the gas adsorption and separation performance of am ZIF-8, including its potential in membrane applications.
Main Methods:
- Solid-state amorphization of ZIF-8 using mechanical compression at 0.75 GPa.
- Characterization of the structural and porous properties of the resulting am ZIF-8.
- Gas adsorption and separation experiments using various gas mixtures (C3H6/C3H8, CO2/N2, CO2/CH4, H2/CH4).
- Fabrication and testing of a self-standing am ZIF-8 membrane.
Main Results:
- Compression successfully induced amorphization of ZIF-8, resulting in a partially collapsed structure with retained porosity.
- am ZIF-8 exhibited significantly higher thermodynamic adsorption selectivity for C3H6/C3H8 (6.72) compared to crystalline ZIF-8 (1.06).
- Complete separation of an equimolar C3H6/C3H8 mixture was achieved with am ZIF-8, indicated by the earlier breakthrough of C3H8.
- Enhanced selectivities were observed for CO2/N2 and CO2/CH4 separations.
- A novel self-standing am ZIF-8 membrane demonstrated promising separation potential for multiple gas pairs.
Conclusions:
- Mechanical compression is an effective method for creating amorphous MOFs with tunable properties.
- The collapsed structure of am ZIF-8 enhances gas adsorption selectivity, particularly for C3H6/C3H8.
- am ZIF-8 shows potential as a separation material in both packed beds and membrane configurations.
- This work opens new avenues for designing advanced porous materials through solid-state amorphization.
