Zeolitic imidazolate framework-8 (ZIF-8) membranes have emerged as promising wall candidates for use in membrane reactors. These membranes can improve the water gas shift (WGS) reaction performance because of their exceptional thermal stability and marked H2/CO2 sieving ability. Here, we propose a modified counter diffusion scheme to form an unprecedented, thermally stable ZIF-8 membrane: Pre-deposition of a zinc precursor (zinc acetate dihydrate) and subsequent solvothermal reaction with a methanolic solution of the ligand (2-methylimidazole). It appears that the pre-deposition and drying of the Zn precursor on and inside a porous support were key to retarding the diffusion of the Zn source, thus leading to the primary contact between the Zn source and ligand molecules within the porous support. As a result, it is likely that a continuous ZIF-8 layer was formed on the top surface and, more preferentially, at the interface with the grains of the porous support, reaching an infiltration depth of approximately 80 μm. Accordingly, this allowed for the effective blocking of the support pores by ZIF-8 grains, as well as their high dispersion. Notably, the resulting ZIF-8 membrane exhibited a maximum H2/CO2 separation factor of ca. 8.7 at a WGS reaction temperature of 300 °C. Unlike the conventional membrane architecture, ZIF-8 grains were densely embedded inside the porous support, thus reducing the risk of mechanical damage. Furthermore, the unique membrane structure was desirable for securing superior thermal stability for reliable and sustainable H2/CO2 separation at 300 °C for up to 72 h.
Bibliographical noteFunding Information:
This work was supported by the Mid-Career Researcher Program ( 2020R1A2C1101974 ) through the National Research Foundation of Korea , funded by the Korea government. In addition, this work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry and Energy of the Republic of Korea (No. 20191510301170 ).
© 2023 Elsevier B.V.
- Embedded ZIF-8 layer
- H/CO separation
- Interlocking structure
- Thermal and mechanical stability
- ZIF-8 membrane
ASJC Scopus subject areas
- General Materials Science
- Physical and Theoretical Chemistry
- Filtration and Separation