What effect does the adsorbate gas have on the experiment?
N 2 at 77K is the most commonly used adsorbate for microporous and mesoporous analysis, but N 2 is adsorbed on micropores, especially ultramicropores (apertures).
The quantification of the problem is unsatisfactory. Therefore, both IUPAC and ISO15901 recommend the use of Ar and CO 2 as an alternative to N 2
Molecular probes. Although the kinetic diameters of N 2 , Ar and CO 2 are similar (0.36, 0.34 and 0.33, respectively), these three adsorbates
The qualitative adsorption behavior is completely different. Since there is no quadrupole moment, Ar does not occur with most surface functional groups and exposed ions.
Specific interactions, therefore Ar adsorption at boiling temperature (87.3K) for many microporous systems (especially molecular sieves, socMOF
Such materials can give more accurate aperture information. Taking FAU molecular sieves as an example, Ar can be at a relatively high relative pressure (10 -5?
Rate adsorption isotherm; while nitrogen micropore filling occurs at 10 -7? instrument
Vacuum degree, longer
Balance time, so the analysis time is at least a few hours longer. The picture shows the standards promulgated by the European Standard Reference Committee.
BCR704/FD107 (same sample, different system names used due to different analytical methods), the experimental time of Ar (87K) used
The experimental time required for 30 hours, while N 2 (77K) is 56 hours. For MOF materials, such as socMOF with high ionization architecture
In the middle, Ar (87K) can also be observed to fill the micropores in a relatively high pressure interval. But for carbon materials, especially without
The surface-modified carbon material can be observed in Ar(87K) and N 2 (77K) due to the small effect of the surface atoms and the quadrupole moment of N 2 .
The adsorption behavior is very similar. ?
? ? ? CO 2 at 273K due to physical properties such as saturated vapor pressure of CO 2 gas, liquefaction temperature and triple point
Adsorption, ? The capillary condensation process of CO 2 does not occur in the mesopores, so the mesoporous pore size distribution cannot be calculated. But due
The kinetic diameter of the sub-gen is small, and CO 2 is a very useful microwell analysis probe for micropores smaller than 1 nm. ?
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