I had measured standard nitrogen adsorption isotherms for MOF materials. However for some of them they had strange shape with maximum. I saw this type of isotherm for hydrogen adsorption, but not for nitrogen. How I can interpret this results?
Thanks in advance!
The isotherm cannot decrease (at least in 99% of cases, but there is a negative adsorption in MOF observed recently in a Nature Chemistry paper). I think this is experimental error.
Probably your apparatus is measuring a wrong dead volume at the beginning of the experiment. Have a look at these and check if the numbers make sense, then examine the experimental procedure to do this in the equipment and what manufacturer recommends for measuring with a another gas (H2 is very small, so it can enter in very narrow pores easily).
Also, there are many discussions here in ResearchGate with isotherms showing a maximum, you can find easily.
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