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Dr. Peter G. Weidler

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Diffraction

Structural investigations of SURMOFs
Different set-ups resp. diffractometer are available: Out-of-plane (coplanar) in θ-θ geometry: determination of lattice plane spacing parallel to the substrate, e.g., (00l)-planes with l=1,2,3.

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Figure 1: The orientation of the planes detectable for the different set-ups

In-plane (non-coplanar) geometry: determination of lattice plane spacing perpendicular to the substrate, e.g., (hk0)-planes with h,k,=1,2,3.

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Figure 2: The geometry of the in-plane configuration (Picture from LAB Report XRD 68, Bruker AXS).

Examples for the OP and IP diffractograms of a HKUST-1 SURMOF are depicted in figure 3 and 4.

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Figure 3: Out-of-plane diffractogram of an HKUST-1 SURMOF. This is also the first quality check in the SURMOF production.

Dies ist auch der erste Qualitätscheck in der Herstellung der SURMOF. (Abb3.jpg)

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Figure 4: In-plane diffractogram of HKUST-1. Clearly more peaks are visible. This additional information is essential for the structure determination e.g., with Rietveld methods

 

Diese zusätzliche Information ist sehr wichtig füreine Strukturbestimmung , z.B. mittels Rietveldmethoden.

 

In-Situ investigations of SUFMOFs
Monitoring of the intensity chance of certain Braggpeaks reveals the kinetics of the loading resp. incorporation of guest-molecules into the SURMOF pore structure.

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Figure 5: Intensity change, especially of the first order Braggpeaks with increasing incorporation of guest molecules into the SURMOF lattice.

Heating the SURMOF in special heating-stages and simultaneously recording the diffractograms allows to determine physical properties of the SUR-MOFs. The example presents heating of HKUST-1 from RT to 150°C. Data evaluation yields a negative thermal expansion factor, i.e. the dimension of the units cell shrinks while heating.

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Figure 6: Shift of the Braggpeak position to higher angles with increasing temperature.

 

 

X-Ray Reflection (XRR)
Moreover X-ray reflection can be applied in order to determine the layer-thickness and layer composition of the sunstrates.