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Issue 10, 2017
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Porous zinc and cobalt 2-nitroimidazolate frameworks with six-membered ring windows and a layered cobalt 2-nitroimidazolate polymorph

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Abstract

Polymorphs of Zn(2-nIm)2 (compound 1) and Co(2-nIm)2 (compounds 2 and 3) (2-nIm = 2-nitroimidazole) have been prepared by two routes: solvothermal synthesis and recrystallisation of ZIF-65(Zn/Co). Compounds 1 and 2 are isostructural, with a tetrahedrally-connected framework topology related to, but different from, that of tridymite (lonsdaleite). Single crystal X-ray diffraction analysis showed that in compound 1 (Pccn, Z = 8; a = 8.462(8) Å, b = 14.549(15) Å, c = 18.799(18) Å, V = 2314(4) Å3) there is rotational disorder for two of the three crystallographically-distinct linker types, which has been investigated computationally and by solid-state NMR spectroscopy. Detailed adsorption studies on a sample of 1 prepared by recrystallisation show 1.1 mmol g−1 uptake of CO2 at 0.1 bar (25 °C) with high affinity for CO2 over CH4 and N2 (adsorption enthalpies of 39.5, 26.0 and 18.5 kJ mol−1, respectively). A cobalt analogue (compound 2) with improved water stability (but lower porosity) has also been prepared. Changing the conditions of synthesis and recrystallisation gives rise to a cobalt 2-nitroimidazolate (Co(2-nIm)2, compound 3), which has a layered structure (I41/amd, a = 6.025(18) Å, c = 26.95(8) Å, V = 978.3(5) Å3) containing sheets of tetrahedrally-connected Co2+ cations composed of four membered rings, without porosity.

Graphical abstract: Porous zinc and cobalt 2-nitroimidazolate frameworks with six-membered ring windows and a layered cobalt 2-nitroimidazolate polymorph

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Publication details

The article was received on 29 Nov 2016, accepted on 20 Jan 2017 and first published on 23 Jan 2017


Article type: Paper
DOI: 10.1039/C6CE02476A
Citation: CrystEngComm, 2017,19, 1377-1388

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    Porous zinc and cobalt 2-nitroimidazolate frameworks with six-membered ring windows and a layered cobalt 2-nitroimidazolate polymorph

    A. Orsi, D. J. Price, J. Kahr, R. S. Pillai, S. Sneddon, S. Cao, V. Benoit, M. M. Łozińska, D. B. Cordes, A. M. Z. Slawin, P. L. Llewellyn, I. Casely, S. E. Ashbrook, G. Maurin and P. A. Wright, CrystEngComm, 2017, 19, 1377
    DOI: 10.1039/C6CE02476A

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