title: 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 CO2and H2uptake 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.
authors.affiliation: Institut für Chemie, Anorganische Chemie, Universität Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany. holdt@uni-potsdam.de.
authors.forename: Suvendu Sekhar
authors.initials: SS
authors.lastname: Mondal
authors.affiliation: Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40204 Düsseldorf, Germany.
authors.forename: Subarna
authors.initials: S
authors.lastname: Dey
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle, Germany and Physics Department, Faculty of Science, Minia University, P.O. 61519, Egypt.
authors.forename: Ahmed G
authors.initials: AG
authors.lastname: Attallah
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krause-Rehberg
authors.affiliation: Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, 40204 Düsseldorf, Germany.
authors.forename: Christoph
authors.identifier: http://orcid.org/0000-0002-6288-9605
authors.initials: C
authors.lastname: Janiak
authors.affiliation: Institut für Chemie, Anorganische Chemie, Universität Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany. holdt@uni-potsdam.de.
authors.forename: Hans-Jürgen
authors.identifier: http://orcid.org/0000-0002-8121-6254
authors.initials: HJ
authors.lastname: Holdt