For the synthesis of MOFs many have reported purification only by filtration and washing with water/solvent. How do you make sure the MOFs are free of unreacted metal compounds/ligands by washing with water/solvents? Is there a way to confirm the complete removal of unreacted material?
Hi Bing Wei Chua
Washing with solvent or MeOH/EtOH is a way to prepare/collect MOF as and product followed by filtration. To confirm the desire end product MOF from the reaction is to run some characterization techniques (XRD, FTIR, EDX, etc.) and the data should be compared with the same characterizations of reactants. From my side, I can suggest this.
Regards
@ Bing Wei chua
Most of the metal ions are soluble in water. So during washing with water those could be removed easily. For ligands, usually solvents which have sparingly solubility for those ligands are employed and can be confirmed easily using XRD.
Hi. usually, to synthesize a MOF, a solvent is selected that has the ability to dissolve metal salt and ligands. After the end of the reaction, MOF is obtained in solid form. then wash the products several times with the same solvent, metal ions and ligands are dissolved in the liquid phase and then overflowed. After drying, you can be sure of your synthesis by comparing the IR and XRD of your sample with the report of MOF synthesis in the reference article.
Qasem Maleki Nitin Gumber Arnab Mukherjee thank you so much for the kind suggestion
Dear Bing Wei Chua this is a very interesting technical question for all researchers who work on the synthesis and characterization of MOFs. The purification of MOFs is an issue which can sometimes not be easily solved. Most MOFs are prepared using hydrothermal / solvothermal synthesis methods. Thus they normally crystallize upon slow cooling of the reaction mixtures. The key to success here is to choose the right molar ratios of starting materials so that as little by-products as possible are formed. Normally the resulting MOFs cannot be purified by recrystallization. Thus it is a safe get to first wash the product with water to remove unreacted metal salts and then wash with a universal organic solvent such as acetone to remove unreacted organic linkers.
Good luck with your work!
By washing you remove also the non reacted linker (FTIR before and after washing) . In addition, BET surface area analysis (in theory after washing the surface area , porosity will increase).
See
DOI https://doi.org/10.1039/C3RA42519C
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