Issue 20, 2012

Structural flexibility and intrinsic dynamics in the M2(2,6-ndc)2(dabco) (M = Ni, Cu, Co, Zn) metal–organic frameworks

Abstract

The synthesis and structural flexibility of the metal–organic frameworks M2(2,6-ndc)2(dabco) (DUT-8(M), M = Ni, Co, Cu, Zn; 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane) as well as their characterization by gas adsorption, 129Xe NMR and 13C MAS NMR spectroscopy are described. Depending on the integrated metal atom the compounds show reversible (DUT-8(Ni), DUT-8(Co)), non-reversible (DUT-8(Zn)) or no (DUT-8(Cu)) structural transformation upon solvent removal and/or physisorption of several gases. DUT-8(Co) exhibits a similar structural transformation by solvent removal and adsorption behavior as observed for DUT-8(Ni). DUT-8(Zn) undergoes an irreversible structural change caused by solvent removal. The non-flexible copper containing MOF reveals the best performance concerning porosity and gas storage capacities within the DUT-8 series. Xenon adsorption studies combined with 129Xe NMR spectroscopy are used to study the flexibility of the DUT-8 compounds. 129Xe chemical shift and line width strongly depend on the metal atom. Solid-state 13C NMR spectroscopy has been applied in order to further characterize the organic parts of the DUT-8 frameworks. While DUT-8(Ni) exhibits narrow, well-resolved lines in its “as made” state, the signals of DUT-8(Co) are broadened and shifted over an unusually wide chemical shift range (−72 to 717 ppm). No detectable signals are found in DUT-8(Cu) indicating significantly changed internal dynamics compared to DUT-8(Ni) and DUT-8(Co).

Graphical abstract: Structural flexibility and intrinsic dynamics in the M2(2,6-ndc)2(dabco) (M = Ni, Cu, Co, Zn) metal–organic frameworks

Supplementary files

Article information

Article type
Paper
Submitted
01 Nov 2011
Accepted
08 Feb 2012
First published
14 Mar 2012

J. Mater. Chem., 2012,22, 10303-10312

Structural flexibility and intrinsic dynamics in the M2(2,6-ndc)2(dabco) (M = Ni, Cu, Co, Zn) metal–organic frameworks

N. Klein, H. C. Hoffmann, A. Cadiau, J. Getzschmann, M. R. Lohe, S. Paasch, T. Heydenreich, K. Adil, I. Senkovska, E. Brunner and S. Kaskel, J. Mater. Chem., 2012, 22, 10303 DOI: 10.1039/C2JM15601F

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