Vacuum drying is probably the least evasive technique and also it is the first thought that comes to mind when evacuating a material BUT usually MOFs collapse after solvent removal and to avoid this we have to carefully monitor the vacuum heating rate.
It is very necessary for synthesizing MOF compounds to make the reaction happens very slowly in order to growth crystals beside the reaction.
Nabeel Arif Tawfeeq Many thanks for your answer, I know this, But I mean during drying and not during synthesis.
for example for the synthesis of MIL-101-SO3H in the autoclave I use fixed temperature ( 180 C for 6 days). and then I collect the product I perform solvent exchange several times then centrifuge after that I start activation in vacuum oven where is required to fix the heating rate 10C/ min. and I am asking about this rate and how can we choose it as my programmable oven can offer 1C/min only
I think the fast cooling cause crystal cracking while a programmed cooling will not cause any cracks.
Since you are stuck with the fixed rate (1C/m), I would recommend to do the solvent exchange with a solvent (e.g. Benzene) of least surface tension, followed by freeze drying for at least 12 h and then dry at ambient temperature, under vacuum for another day. Only then you can use higher temperature in your vacuum oven. I hope this will give you better result.
Md Mamdudur Rahman thank you so much.
Nabeel Arif Tawfeeq thank you so much
The heating rate is very crucial to ensure the stability of the MOFs synthesised,thus preserving the original structure formed from collapsing.
Is there any MOFs which withstands temperature above 1000 degree celsius?
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