Roztocki, K.; Rauche, M.; Bon, V.; Kaskel, S.; Brunner, E.; Matoga, D.: Combining In Situ Techniques (XRD, IR, and C-13 NMR) and Gas Adsorption Measurements Reveals CO2-Induced Structural Transitions and High CO2/CH4 Selectivity for a Flexible Metal-Organic Framework JUK-8. ACS Applied Materials & Interfaces 13 (2021), p. 28503-28513
10.1021/acsami.1c07268
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Abstract:
Flexible metal–organic frameworks (MOFs) are promising materials in gas-related technologies. Adjusting the material to processes requires understanding of the flexibility mechanism and its influence on the adsorption properties. Herein, we present the mechanistic understanding of CO2-induced pore-opening transitions of the water-stable MOF JUK-8 ([Zn(oba)(pip)]n, oba2– = 4,4′-oxybis(benzenedicarboxylate), pip = 4-pyridyl-functionalized benzene-1,3-dicarbohydrazide) as well as its potential applicability in gas purification. Detailed insights into the global structural transformation and subtle local MOF–adsorbate interactions are obtained by three in situ techniques (XRD, IR, and 13CO2-NMR). These results are further supported by single-crystal X-ray diffraction (SC-XRD) analysis of the solvated and guest-free phases. High selectivity toward carbon dioxide derived from the single-gas adsorption experiments of CO2 (195 and 298 K), Ar (84 K), O2 (90 K), N2 (77 K), and CH4 (298 K) is confirmed by high-pressure coadsorption experiments of the CO2/CH4 (75:25 v/v) mixture at different temperatures (288, 293, and 298 K) and in situ NMR studies of the coadsorption of 13CO2/13CH4 (50:50 v/v; 195 K).