Combined experimental and computational NMR study of crystalline and amorphous zeolitic imidazolate frameworks



Baxter, Emma F, Bennett, Thomas D, Mellot-Draznieks, Caroline, Gervais, Christel, Blanc, Frederic ORCID: 0000-0001-9171-1454 and Cheetham, Anthony K
(2015) Combined experimental and computational NMR study of crystalline and amorphous zeolitic imidazolate frameworks. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17 (38). pp. 25191-25196.

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Abstract

Zeolitic imidazolate frameworks (ZIFs) have attracted great interest in recent years due to their high chemical and thermal stability with promising applications in gas storage and separations. We investigate the structures of three different crystalline ZIFs - ZIF-4, ZIF-8, ZIF-zni - and their amorphous counterparts using high field (13)C and (15)N CP MAS NMR. The high field (20 T) allows for the observation of all crystallographically independent carbon and nitrogen atoms in the crystalline ZIFs. Combining our experimental results with density functional theory calculations enabled the assignment of all chemical shifts. The crystalline spectra reveal the potential of high field NMR to distinguish between two ZIF polymorphs, ZIF-4 and ZIF-zni, with identical [Zn(C3H3N2)2] chemical compositions. (13)C and (15)N CP MAS NMR data obtained for the amorphous ZIFs clearly showed signal broadening upon amorphization, confirming the retention of chemical composition and the structural similarity of amorphous ZIF-4 and ZIF-zni. In the case of amorphous ZIF-8, we present evidence for the partial de-coordination of the 2-methyl imidazole linker.

Item Type: Article
Uncontrolled Keywords: Zeolites, Imidazoles, Crystallography, X-Ray, Magnetic Resonance Spectroscopy, Molecular Conformation
Subjects: ?? QD ??
Depositing User: Symplectic Admin
Date Deposited: 06 Oct 2015 15:03
Last Modified: 16 Dec 2022 12:08
DOI: 10.1039/c5cp02552d
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/2029719