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

Angelica Orsi, David J. Price, Jürgen Kahr, Renjith S. Pillai, Scott Sneddon, Shuai Cao, Virginie Benoit, Magdalena M. Łozińska, David B. Cordes, Alexandra M. Z. Slawin, Philip L. Llewellyn, Ian Casely, Sharon Elizabeth Ashbrook, Guillaume Maurin, Paul A. Wright

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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.
Original languageEnglish
Pages (from-to)1377-1388
Number of pages12
JournalCrystEngComm
Volume19
Issue number10
Early online date23 Jan 2017
DOIs
Publication statusPublished - 14 Mar 2017

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