Journal Article

DESY-2014-02097

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Isomorphous Substitution in a Flexible Metal–Organic Framework: Mixed-Metal, Mixed-Valent MIL-53 Type Materials

Breeze, M. I. (Corresponding author) ; Clet, G. ; Campo, B. C. ; Vimont, A. ; Daturi, M. ; Grenèche, J.-M. ; Dent, A. J. ; Millange, F.Extern* ; Walton, R. (Corresponding Author)Extern*

2013
American Chemical Society Washington, DC

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Please use a persistent id in citations: doi:10.1021/ic400923d  doi:10.3204/DESY-2014-02097

Abstract: Mixed-metal iron–vanadium analogues of the 1,4-benzenedicarboxylate (BDC) metal–organic framework MIL-53 have been synthesized solvothermally in N,N′-dimethylformamide (DMF) from metal chlorides using initial Fe:V ratios of 2:1 and 1:1. At 200 °C and short reaction time (1 h), materials (Fe,V)II/IIIBDC(DMF1–xFx) crystallize directly, whereas the use of longer reaction times (3 days) at 170 °C yields phases of composition [(Fe,V)III0.5(Fe,V)0.5II(BDC)(OH,F)]0.5–·0.5DMA+ (DMA = dimethylammonium). The identity of the materials is confirmed using high-resolution powder X-ray diffraction, with refined unit cell parameters compared to known pure iron analogues of the same phases. The oxidation states of iron and vanadium in all samples are verified using X-ray absorption near edge structure (XANES) spectroscopy at the metal K-edges. This shows that in the two sets of materials each of the vanadium and the iron centers are present in both +2 and +3 oxidation states. The local environment and oxidation state of iron is confirmed by 57Fe Mössbauer spectrometry. Infrared and Raman spectroscopies as a function of temperature allowed the conditions for removal of extra-framework species to be identified, and the evolution of μ2-hydroxyls to be monitored. Thus calcination of the mixed-valent, mixed-metal phases [(Fe,V)III0.5(Fe,V)0.5II(BDC)(OH,F)]0.5–·0.5DMA+ yields single-phase MIL-53-type materials, (Fe,V)III(BDC)(OH,F). The iron-rich, mixed-metal MIL-53 shows structural flexibility that is distinct from either the pure Fe material or the pure V material, with a thermally induced pore opening upon heating that is reversible upon cooling. In contrast, the material with a Fe:V content of 1:1 shows an irreversible expansion upon heating, akin to the pure vanadium analogue, suggesting the presence of some domains of vanadium-rich regions that can be permanently oxidized to V(IV).

Note: © American Chemical Society

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Contributing Institute(s):

1. DOOR-User (DOOR)

Research Program(s):

1. DORIS Beamline F3 (POF2-54G13) (POF2-54G13)

Experiment(s):

1. DORIS Beamline F3 (DORIS III)

Appears in the scientific report 2013

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Database coverage:
; ; JCR ; NCBI Molecular Biology Database ; Nationallizenz ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection ; Zoological Record

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