Metal-Dependent and Selective Crystallization of CAU-10 and MIL-53 Frameworks through Linker Nitration |
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Authors: | Timo Rabe Erik Svensson Grape Dr. Tobias A. Engesser Dr. A. Ken Inge Jonas Ströh Gitta Kohlmeyer-Yilmaz Dr. Mohammad Wahiduzzaman Prof. Dr. Guillaume Maurin Prof. Dr. Frank D. Sönnichsen Prof. Dr. Norbert Stock |
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Affiliation: | 1. Department of Inorganic Chemistry, Christian-Albrechts-Universität zu Kiel, 24118 Kiel, Germany;2. Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden;3. Otto Diels Institute for Organic Chemistry, Christian-Albrechts-Universität zu Kiel, 24118 Kiel, Germany;4. ICGM, Univ. Montpellier, CNRS, ENSCM, Université Montpellier, 34095 Montpellier, France |
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Abstract: | The reaction of the V-shaped linker molecule 5-hydroxyisophthalic acid (H2L0), with Al or Ga nitrate under almost identical reaction conditions leads to the nitration of the linker and subsequent formation of metal–organic frameworks (MOFs) with CAU-10 or MIL-53 type structure of composition [Al(OH)(L)], denoted as Al-CAU-10-L0, 2, 4, 6 or [Ga(OH)(L)], denoted as Ga-MIL-53-L2. The Al-MOF contains the original linker L0 as well as three different nitration products (L2, L4 and L4/6), whereas the Ga-MOF mainly incorporates the linker L2. The compositions were deduced by 1H NMR spectroscopy and confirmed by Rietveld refinement. In situ and ex situ studies were carried out to follow the nitration and crystallization, as well as the composition of the MOFs. The crystal structures were refined against powder X-ray diffraction (PXRD) data. As anticipated, the use of the V-shaped linker results in the formation of the CAU-10 type structure in the Al-MOF. Unexpectedly, the Ga-MOF crystallizes in a MIL-53 type structure, which is usually observed with linear or slightly bent linker molecules. To study the structure directing effect of the in situ nitrated linker, pure 2-nitrobenzene-1,3-dicarboxylic acid (m-H2BDC-NO2) was employed which exclusively led to the formation of [Ga(OH)(C8H3NO6)] (Ga-MIL-53-m-BDC-NO2), which is isoreticular to Ga-MIL-53-L2. Density Functional Theory (DFT) calculations confirmed the higher stability of Ga-MIL-53-L2 compared to Ga-CAU-10-L2 and grand canonical Monte Carlo simulations (GCMC) are in agreement with the observed water adsorption isotherms of Ga-MIL-53-L2. |
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Keywords: | aluminium framework flexibility gallium molecular simulations water adsorption |
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