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Issue 14, 2017
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Insights into the pores of microwave-assisted metal–imidazolate frameworks showing enhanced gas sorption

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Abstract

Microwave heating (MW)-assisted synthesis has been widely applied as an alternative method for the chemical synthesis of organic and inorganic materials. In this work, we report MW-assisted synthesis of three isostructural 3D frameworks with a flexible linker arm of the chelating linker 2-substituted imidazolate-4-amide-5-imidate, named IFP-7-MW (M = Zn, R = OMe), IFP-8-MW (M = Co; R = OMe) and IFP-10-MW (M = Co; R = OEt) (IFP = Imidazolate Framework Potsdam). These chelating ligands were generated in situ by partial hydrolysis of 2-substituted 4,5-dicyanoimidazoles under MW- and also conventional electrical heating (CE)-assisted conditions in DMF. The structure of these materials was determined by IR spectroscopy and powder X-ray diffraction (PXRD) and the identity of the materials synthesized under CE-conditions was established. Materials obtained from MW-heating show many fold enhancement of CO2 and H2 uptake capacities, compared to the analogous CE-heating method based materials. To understand the inner pore-sizes of IFP structures and variations of gas sorptions, we performed positron annihilation lifetime spectroscopy (PALS), which shows that MW-assisted materials have smaller pore sizes than materials synthesized under CE-conditions. The “kinetically controlled” MW-synthesized material has an inherent ability to trap extra linkers, thereby reducing the pore sizes of CE-materials to ultra/micropores. These ultramicropores are responsible for high gas sorption.

Graphical abstract: Insights into the pores of microwave-assisted metal–imidazolate frameworks showing enhanced gas sorption

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Publication details

The article was received on 29 Jan 2017, accepted on 16 Mar 2017 and first published on 16 Mar 2017


Article type: Paper
DOI: 10.1039/C7DT00350A
Citation: Dalton Trans., 2017,46, 4824-4833
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    Insights into the pores of microwave-assisted metal–imidazolate frameworks showing enhanced gas sorption

    S. S. Mondal, S. Dey, A. G. Attallah, R. Krause-Rehberg, C. Janiak and H. Holdt, Dalton Trans., 2017, 46, 4824
    DOI: 10.1039/C7DT00350A

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