I am synthesizing a Zinc based MOF that is having acyclic ligand (in DMF), after synthesis while taking it out (the MOF single crystal ) from the reaction mixture it is giving very good diffraction & 1700 angstrom cube volume , but it is getting degraded in room temp as well as in low temp (150K). So the Single Crystal XRD is undoable. I have also noticed after synthesis if I solvent exchange it with water , the MOF crystals are not present as solid mostly going back to solution. What should I do to successfully complete the SCXRD experiment?
Hi Sumanta,
My first suggestion is to avoid water for solvent exchange it will degrade the Zn MOF surely very well-known phenomenon in literature. Next thing, in case of DMF as solvent we face this type of problem again very well known example is early reported MOF-5. Try to keep reaction with DMA (dimethylacetamide) and DEF (diethylformamide) as the solvent. Otherwise, you can try collecting the crystal dipped in mother liquor such tips are available where a very small amount of solvent can be loaded with crystal and where crystal remained dipped whole time during data collection which will allow you to collect full Single crystal data.
Sumanta Chowdhury
- always keep the crystals in very little volume of reaction solvent for stability
when it comes to XRD analysis
- Keep the crystals dipped in reaction solvent
or
- Try using Lindemann capillary tube (also you "MAY" need to dip the crystal in reaction solvent )
We have access to a SCXRD machine which has a fixed source and moving sample holder. I think it's very difficult to perform the Lindemann capillary tube assisted SCXRD.
You can load the crystal and the solution in a borosilicate glass (aka Lindemann) capillary then cut it as a suitable length, seal it and mount it on the sample holder as you would with a normal glass fiber. No need for special setup. However this requires a bit of manual practice and patience and the tricky part is to prevent the crystal from moving inside the capillary when you rotate it. You can stick a few glass wool fibers in the capillary to help getting the crystal stuck.
Another option is to take a few crystals from the solution very quickly and immediately dip them in a drop of oil or grease (e.g. Paratone oil, vaseline). Chose the crystal and mount it on a glass fiber or on a loop using the oil itself and make sure the crystal is still covered by a thin layer of it. Measure at low T so that the oil or grease will be hard enough and act as glue.
Side note. Before putting all this effort, you might want to check in a database if the unit cell is new or not.
Thank you all for your suggestions. I will let you know if I succeeded or not. Thank you again.
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