Due to unique structural properties, high porosity, surface area and unexpected thermal and chemical stability zeolitic imidazolate frameworks (ZIFs) could be applied in catalysis, gas separation and storage [1]. For example,... [ view full abstract ]
Due to unique structural properties, high porosity, surface area and unexpected thermal and chemical stability zeolitic imidazolate frameworks (ZIFs) could be applied in catalysis, gas separation and storage [1]. For example, ZIF-8 could be effectively applied for iodine isotopes, which are a by-product of nuclear fuel cycle [2]. Most of ZIFs structures studied during the last decades are based on single metals and their properties mainly depend on metal species. Therefore, construction of mixed ZIFs would be an interesting option for tuning or introducing new properties in ZIFs.
In this study CoxZn1-x-ZIF-8 (x=5, 25, 75 %) frameworks we synthesized using microwave radiation [3]. The experimental Co K-edge (7709 eV) and Zn-K edge (9659 eV) XANES spectra were measured using in-house X-ray spectrometer Rigaku R-XAS Looper. The crystal structure of CoxZn1-x-ZIF8 samples were characterized with powder X-ray diffraction (PXRD). Additionally, for the characterization of the samples XRF, TEM techniques were used.
XRD patterns of synthesized samples suggests that the bimetallic ZIFs have the same crystalline structure as that of Zn-ZIF-8. A well-resolved pre-edge feature on the Co-K-edge XANES spectra (~7,700 eV) is characterized by an 1s→3d electronic transition and clearly indicates that the local environment of cobalt atoms is not centrally symmetric and confirms the tetrahedral symmetry. The position of the absorption edge and the white line (~ 7708 eV) on the XANES spectra for the Co-ZIF-67 sample and the bimetallic CoxZn1-x-ZIF-8 zeolites coincide, which means that the bimetallic ZIFs as well as the original Co-ZIF-67 material contain divalent cobalt ions, which is consistent with the data of X-ray diffraction.
This work was supported by the Government of the Russian Federation (Mega-grant no. 14.Y26.31.0001).
1. Tulchinsky, Y., et al., Reversible Capture and Release of Cl2 and Br2 with a Redox-Active Metal–Organic Framework. J. Am. Chem. Soc., 2017. 139: p. 5992-5997.
2. Sava, D.F., et al., Capture of Volatile Iodine, a Gaseous Fission Product, by Zeolitic Imidazolate Framework-8. J. American Chem. Soc., 2011. 133: p. 12398-12401.
3. Butova, V.V., et al., New microwave-assisted synthesis of ZIF-8. Mendeleev Commun., 2016. 26: p. 43-44.
Spectroscopy , Nanotechnology for environment and energy
