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Uptake of Liquid Alcohols by the Flexible Fe III Metal–Organic Framework MIL‐53 Observed by Time‐Resolved In Situ X‐ray Diffraction
Author(s) -
Walton Richard I.,
Munn Alexis S.,
Guillou Nathalie,
Millange Franck
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201003634
Subject(s) - in situ , diffraction , x ray , metal organic framework , metal , x ray crystallography , materials science , liquid metal , chemistry , analytical chemistry (journal) , organic chemistry , physics , optics , adsorption
A comprehensive, time‐resolved, energy‐dispersive X‐ray diffraction study of the uptake of liquid alcohols (methanol, ethanol, propan‐1‐ol and propan‐2‐ol) by the flexible metal‐organic framework solid MIL‐53(Fe)[H 2 O] is reported. In the case of the primary alcohols, a fluorinated version of the MIL‐53(Fe) host ( C 2/ c symmetry V ca. 1000 Å 3 ), in which a fraction of framework hydroxides are replaced by fluoride, shows uptake of alcohols to give initially a partially expanded phase ( C 2/ c symmetry , V ca. 1200 Å 3 ) followed by an expanded form of the material (either Imcm or Pnam symmetry , V ca. 1600 Å 3 ). In the case of methanol–water mixtures, the EDXRD data show that the partially open intermediate phase undergoes volume expansion during its existence, before switching to a fully open structure if concentrated methanol is used; analogous behaviour is seen if the initial guest is propan‐2‐ol, which then is replaced by pyridine, where a continuous shift of Bragg peaks within C 2/ c symmetry is observed. In contrast to the partially fluorinated materials, the purely hydroxylated host materials show little tendency to stabilise partially open forms of MIL‐53(Fe) with primary alcohols and the kinetics of guest introduction are markedly slower without the framework fluorination: this is exemplified by the exchange of water by propan‐2‐ol, where a partially open C 2/ c phase is formed in a step‐wise manner. Our study defines the various possible pathways of liquid‐phase uptake of molecular guests by flexible solid MIL‐53(Fe).