Issue 14, 2017

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

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

Supplementary files

Article information

Article type
Paper
Submitted
29 Jan 2017
Accepted
16 Mar 2017
First published
16 Mar 2017

Dalton Trans., 2017,46, 4824-4833

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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