I was reading an article that mentioned in it, Anchoring Ir-EDTA onto the cluster surface did not affect the structure of the MOF since the characteristic peaks remained unaltered. In XRPD pattern all peaks remain but the intensity of peaks decrease with increase of catalyst loading. So I want to know Does anchoring molecular catalyst ( metal complexes ) to MOFs decrease the crystallinity of the MOFs?
ICP-OES analysis for the determination of Ir content gave the following results: IrEDTA@UiO-66(1) = 256 µmol/g; IrEDTA@UiO-66(2) = 226 µmol/g; and IrEDTA@UiO-66(3) =170 µmol/g.
https://www.mdpi.com/549538
If the peak intensity is decreasing it can be due to multiple factors. You could try to compare the SEM images of MOF before and after anchoring of Ir-EDTA. You might see some changes in the morphology. It is possible that some amorphous materials covered the surface and that might lead to decrease in intensity of XRD peaks. The crystallite size might have changed after anchoring, or some feature of the crystal morphology might have been affected due to anchoring.
Dear Sina Safavi thank you for posting this very interesting technical question. As you may remember, I'm not a proven expert in this area of research as we are organometallic chemists. However, when looking at the reference you provided, I had some (perhaps irrelevant) thoughts about this: In the article the authors say that the original MOF has "defects" which are induced by partial substitution of terephthalic acid linkers by smaller formate groups. What if anchoring of the iridium complex sort of "repairs" these defects so that the resulting anchored MOF becomes more crystalline? I may be proven wrong, but I assume that the crystallinity of a MOF can even increase by post-synthesis modification. Of course, as mentioned by Mohammad Kooti post-synthetic functionalization of MOFs can also have the opposite effect.
For more general information about this, please have a look at the following useful articles:
Post-synthetic metalation of metal–organic frameworks
https://pubs.rsc.org/en/content/articlelanding/2014/cs/c4cs00076e#!divAbstract
and
Metal–Organic Frameworks as Versatile Platforms for Organometallic Chemistry
Article Metal–Organic Frameworks as Versatile Platforms for Organome...
The second article has been posted by the authors as public full text on RG so that it can be freely downloaded as pdf file.
Good luck with your research and best wishes, Frank Edelmann
Peak reduction could be due to several effects. Change in crystallinity, crystal-to-crystal transformation resulting in change/reduction in phase i.e., specific indices associated with those principle peaks, accumulation of amorphous/glassy species, guest removal, etc. In my view, one can combine other invetigations alongwith xrd to confirm what has happened. SEM (as stated by another colleague) can help but thats not conlusive. X-Ray absorption studies can be conclusive in this regard.
Disclaimer: i typed this answer using my phone so apologies for typos.
Peak reduction could be due to several effects. Change in crystallinity, crystal-to-crystal transformation resulting in change/reduction in phase i.e., specific indices associated with those principle peaks, accumulation of amorphous/glassy species, guest removal, etc. In my view, one can combine other invetigations alongwith xrd to confirm what has happened. SEM (as stated by another colleague) can help but thats not conlusive. X-Ray absorption studies can be conclusive in this regard.
Disclaimer: i typed this answer using my phone so apologies for typos.
Dear Frank T. Edelmann
I always get happy when see your wonderful answers under my questions. The idea of repairing the defects by anchoring catalyst is amazing and as I quickly searched, it doesn't studied yet. But in the purpose of water splitting they made that defects to improve the diffusion of solvent to increase catalytic activity. Hence if the defects repaired then the catalytic activity will decrease. But your hypothesis is a golden one. And I would be glad if I could work with you on this interesting research.
Dear Ranjit Kumar and Latif Ullah
Your are absolutely right but there is no SEM or TEM images even in supporting information.
It depends on the MOF and modification conditions. Remarkably, the UiO-66 series are remained intact. The XRD peak intensities are usually decreased due to the pore occupation (< ~2Theta =10 degree)and some changes in the structure.
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