2.
Unraveling the arrangement of Al and Fe within the framework explains the magnetism of mixed-metal MIL-100(Al,Fe)Gregor Mali,
Matjaž Mazaj,
Iztok Arčon,
Darko Hanžel,
Denis Arčon,
Zvonko Jagličić, 2019, original scientific article
Abstract: Properties of mixed-metal MOFs depend on the distribution of different
metals within their frameworks. Determination of this distribution is often very
challenging. Using an example of aluminum- and iron-containing MIL-100, we
demonstrate that 27Al NMR spectroscopy, when combined with first-principles
calculations and magnetic, X-band electron paramagnetic resonance, Fe K-edge extended
X-ray absorption fine structure, and Mössbauer measurements, enables one to accurately
determine the arrangement of Al and Fe within the metal trimers, which are the basic
building units of MIL-100. In this particular material, the incorporation of Fe and Al on
the framework metal sites is random. Crucial for deciphering the arrangement is detecting
NMR signals, shifted because of the strong hyperfine interaction between the 27Al nuclei
and the unpaired electronic spins of Fe3+ ions, assigning the shifted signals aided by first-principles calculations of hyperfine
couplings, and quantitatively evaluating the NMR intensities and the measured effective magnetic moment.
Keywords: Fe EXAFS, XANES, MIL100, MOF, magnetizem
Published in RUNG: 26.03.2019; Views: 3885; Downloads: 0
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