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Issue 10, 2016
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The flexibility of modified-linker MIL-53 materials

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Abstract

The flexibility of eight aluminium hydroxo terephthalates [Al(OH)(BDC–X)]·n(guest) (BDC = 1,4-benzene-dicarboxylate; X = –H, –CH3, –Cl, –Br, –NH2, –NO2, –(OH)2, –CO2H) crystallising in the MIL-53-type structure was investigated upon thermal dehydration of as-made samples, superhydration and methanol adsorption/desorption using in situ powder X-ray diffraction (PXRD). Profile fitting was used to determine lattice parameters as a function of time and/or temperature to describe their structural evolution. It has thus been shown that while methanol vapour adsorption induces an opening of all the modified frameworks, except the –NH2 material, superhydration only leads to open structures for Al-MIL-53–NO2, –Br and –(OH)2. All the MIL-53 solids, except Al-MIL-53–(OH)2 are present in the open structures upon thermal dehydration. In addition to the exploration of the breathing behavior of this MIL-53 series, the issue of disorder in the distribution of the functional groups between the organic linkers was explored. As a typical illustration, density functional theory calculations were carried out on different structures of Al-MIL-53–Cl, in which the distribution of –Cl within two adjacent BDC linkers is varied. The results show that the most energetically stable configuration leads to the best agreement with the experimental PXRD pattern. This observation supports that the distribution of the selected linker substituent in the functionalised solid is governed by energetics and that there is a preference for an ordering of this arrangement.

Graphical abstract: The flexibility of modified-linker MIL-53 materials

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Supplementary files

Article information


Submitted
04 Sep 2015
Accepted
06 Oct 2015
First published
06 Oct 2015

Dalton Trans., 2016,45, 4162-4168
Article type
Paper
Author version available

The flexibility of modified-linker MIL-53 materials

A. S. Munn, R. S. Pillai, S. Biswas, N. Stock, G. Maurin and R. I. Walton, Dalton Trans., 2016, 45, 4162
DOI: 10.1039/C5DT03438H

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