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. 2019 Mar 14;10(7):1464–1470. doi: 10.1021/acs.jpclett.9b00341

Figure 1.

Figure 1

(A) Fe K-edge XANES spectra of MIL-100(Fe) and MIL-100(Al,Fe) samples and reference iron oxide compounds with iron valence states between Fe2+ and Fe3+ [Fe2+: FeSO4·7H2O; Fe2.67+: Fe3O4; Fe3+: Fe2O3 (hematite), α-FeOOH (goethite)]. The spectra are shifted vertically for clarity. The vertical dashed line is plotted at the Fe K-edge position of 7125 eV to facilitate the comparison of the Fe K-edge energy positions in different Fe compounds. (B) Fourier transform magnitude of k3-weighted Fe EXAFS spectra of MIL-100(Fe) and MIL-100(Al,Fe) samples, calculated in the k range of 3–14 Å–1. Experiment, circles; best-fit EXAFS models in the R range from 1.0–3.3 Å, solid lines. (C) Fe Mössbauer spectra of MIL-100(Fe) and MIL-100(Al,Fe) can be modeled well by at least three contributions. Three equally intense individual components, comprising the fit of the spectrum of MIL-100(Fe), are shown. The three components can be assigned to three crystallographically slightly different Fe sites within the 3Fe trimers. (D) X-band EPR spectra of MIL-100(Fe) (red bullets) and MIL-100(Al,Fe) (blue circles) recorded at 295 and 30 K. The thin black lines are the fits of the spectra (see the Supporting Information). The positions of the resonances with g = 2.09 and g = 4.3 are marked with vertical lines. The narrow signal indicated by a star is due to the dielectric resonator. The spectra are vertically shifted for clarity.