Journal
MICROPOROUS AND MESOPOROUS MATERIALS
Volume 183, Issue -, Pages 156-161Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.micromeso.2013.09.015
Keywords
MIL-53; Hydrothermal stability of MOF; Surface modification of MIL-53; Hydrolysis of MIL-53
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Funding
- French Agence Nationale de la Recherche [SOFTCRYSTAB ANR-2010-BLAN-0822-04]
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It is shown that treatment of MIL-53(Al) (Al(OH)BDC-H2O, BDC = 1,4-benzene dicarboxylate) under reflux in water results in a progressive transformation of the solid into a new well crystallized phase. After reflux for 10 h or more the new phase is obtained in a pure form and its XRD pattern was indexed in a monoclinic system with the following cell parameters: a = 19.47 angstrom, b = 8.98 angstrom, c = 6.60 angstrom, beta = 107.7 degrees. Characterization of the obtained solid by TGA, ET-IR, NMR, TEM and XRD has revealed that its composition is [0.8Al(OH)BDC-0.2H(2)BDC] + 0.2 gamma-AlO(OH). Formation of this material indicates that under reflux in water a partial hydrolysis of the MOF network occurs producing H2BDC molecules (occluded in the pores) and gamma-AlO(OH) species. The latter is shown to form a thick shell (100-200 nm) consisting of strongly crumpled sheets of 3 nm of thickness. Formation of gamma-AlO(OH) under reflux in water allows to use such treatment as an easy way to modify the surface properties of MIL-53(Al). We showed that treatment of MIL-53(Al) under reflux in water for a short time (<1 h) yields a thin layer of gamma-AlO(OH) on the surface of the particles while only slightly decreasing their pore volume (from 0.57 to 0.50 cm(3)/g). Such surface modification of MIL-53(Al) might be useful from two points of view. First, it creates a strongly hydrophilic layer on the surface of material and may thus facilitate its shaping. Second, the OH groups of gamma-AlO(OH) surface layer may be used as anchoring sites for functionalization of MIL-53(Al) particles. (C) 2013 Elsevier Inc. All rights reserved.
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