Mixed-linker strategy for suppressing structural flexibility of metal-organic framework membranes for gas separation

• Published in: Communications chemistry Vol. 6; no. 1; p. 118
• Main Authors: Chang, Chung-Kai, Ko, Ting-Rong, Lin, Tsai-Yu, Lin, Yen-Chun, Yu, Hyun Jung, Lee, Jong Suk, Li, Yi-Pei, Wu, Heng-Liang, Kang, Dun-Yen
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.06.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/299/1013; 639/301/357/537; 639/4077/4057; 639/638/298/921; Carbon dioxide; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Density functional theory; Flexibility; Fourier transforms; Gas permeation; Gas separation; Membranes; Metal-organic frameworks; Methane; Structural stability
• ISSN: 2399-3669; 2399-3669
• DOI: 10.1038/s42004-023-00917-2

Structural flexibility is a critical issue that limits the application of metal-organic framework (MOF) membranes for gas separation. Herein we propose a mixed-linker approach to suppress the structural flexibility of the CAU-10-based (CAU = Christian-Albrechts-University) membranes. Specifically, pure CAU-10-PDC membranes display high separation performance but at the same time are highly unstable for the separation of CO 2 /CH 4 . A partial substitution (30 mol.%) of the linker PDC with BDC significantly improves its stability. Such an approach also allows for decreasing the aperture size of MOFs. The optimized CAU-10-PDC-H (70/30) membrane possesses a high separation performance for CO 2 /CH 4 (separation factor of 74.2 and CO 2 permeability of 1,111.1 Barrer under 2 bar of feed pressure at 35°C). A combination of in situ characterization with X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, as well as periodic density functional theory (DFT) calculations, unveils the origin of the mixed-linker approach to enhancing the structural stability of the mixed-linker CAU-10-based membranes during the gas permeation tests. Metal–organic frameworks have demonstrated great promise for gas separation membranes, but their structural flexibility hinders their stability and hence sieving performance. Here, the authors systematically tune the ratio of mixed linkers in CAU-10-based MOF membranes, finding the optimal ratio that suppresses structural flexibility and enhances CO 2 /CH 4 separation performance.