How Interpenetration Ensures
Rigidity and Permanent
Porosity in a Highly Flexible Hybrid Solid
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Abstract
The synthesis and the crystal structure determination,
using a
synchrotron microdiffraction setup, of the interwoven analogue of
the highly flexible iron(III) dicarboxylate MIL-88D structure are
reported. Unlike its flexible counterpart, MIL-126, or Fe<sup>III</sup><sub>3</sub>O(H<sub>2</sub>O)<sub>2</sub>(OH)[(O<sub>2</sub>C)-C<sub>12</sub>H<sub>8</sub>-(CO<sub>2</sub>)]<sub>3</sub>·<i>n</i>(solv), exhibits a rigid structure with an accessible three
dimensional (3D) pore system resulting in a Brunauer–Emmett–Teller
(BET) surface area over 1700 m<sup>2</sup>·g<sup>–1</sup>. Moreover, a large amount of coordinatively unsaturated Fe sites
of +2 and +3 oxidation states are accessible to NO and acetonitrile
molecules as shown by infrared spectroscopy. MIL-126 might be thus
used for the removal of aromatic N-heterocyclic compounds from fossil
fuel streams, as shown here in the efficient capture of indole from
model benzothiophene/indole mixtures in heptane/toluene
