Issue 38, 2015

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

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 13C and 15N 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. 13C and 15N 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.

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

Supplementary files

Article information

Article type
Paper
Submitted
01 Mai 2015
Accepted
01 Sep 2015
First published
01 Sep 2015

Phys. Chem. Chem. Phys., 2015,17, 25191-25196

Author version available

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

E. F. Baxter, T. D. Bennett, C. Mellot-Draznieks, C. Gervais, F. Blanc and A. K. Cheetham, Phys. Chem. Chem. Phys., 2015, 17, 25191 DOI: 10.1039/C5CP02552D

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