Synthesis and Characterization of Hybrid Metal Zeolitic Imidazolate Framework Membrane for Efficient H2/CO2 Gas Separation

Po-Hsueh Chang; Yuan-Tse Lee; Cheng-Hsiung Peng

doi:10.3390/ma13215009

Synthesis and Characterization of Hybrid Metal Zeolitic Imidazolate Framework Membrane for Efficient H₂/CO₂ Gas Separation

Materials (Basel). 2020 Nov 6;13(21):5009. doi: 10.3390/ma13215009.

Authors

Po-Hsueh Chang¹, Yuan-Tse Lee², Cheng-Hsiung Peng¹

Affiliations

¹ Department and Institute of Chemical and Materials Engineering, Minghsin University of Science and Technology, Xinxing Road, Hsinchu 30401, Taiwan.
² Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan.

Abstract

In this paper, we propose mixed metal ions in the node of the zeolitic imidazolate framework (ZIF) structure. The hybrid metal ZIF is formed for the gas separation of hydrogen and carbon dioxide. In the first stage, the nanoparticles were prepared as a coating on a substrate, and acting as secondary growing nuclei. The hybrid metal ZIF structures were characterized by X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). N₂ adsorption-desorption isotherms determined surface area, and scanning electron microscopy (SEM) was used to observe the microstructure and surface morphology. The hybrid metal ZIF-8-67 powder had the largest surface area (1260.40 m² g^-1), and the nanoparticles (100 nm) could be fully dense-coated on the substrate to benefit the subsequent membrane growth. In the second stage, we prepared the hybrid metal ZIF-8-67 membrane on the pre-seeding substrate with mixed metal nanoparticles of cobalt and zinc, by the microwave hydrothermal method. Cobalt ions were identified in the tetrahedral coordination through UV-Vis, and the membrane structure and morphology were determined by XRD and SEM. Finally, a gas permeation analyzer (GPA) was used to determine the gas separation performance of the hybrid metal ZIF-8-67 membrane. We successfully introduced zinc ions and cobalt ions into the ZIF structure, where cobalt had a strong interaction with CO₂. Therefore, GPA analysis showed an excellent H₂/CO₂ separation factor due to lower CO₂ permeability. The CO₂ permeance was ~0.65 × 10^-8 mol m^-2 s^-1 Pa^-1, and the separation factors for H₂/CO₂ and H₂/N₂ were 9.2 and 2.9, respectively. Our results demonstrate that the hybrid metal ZIF-8-67 membrane has a superior H₂/CO₂ separation factor, which can be attributed to its very high specific surface area and structure. Based on the above, hybrid metal ZIF-8-67 membranes are expected to be applied in hydrogen or carbon dioxide gas separation and purification.

Keywords: ZIF-8-67 membranes; gas separation; permeance; separation factor; zeolitic imidazolate framework.