If a material shows pore diameter less than 2nm (around 1.8 nm) but following H4 hysteresis. Will it be considered as microporous or mesoporous?
Dear Kuljit Kaur
To find the porosity of a material from BET (Brunauer–Emmett–Teller) analysis, you need to first obtain the BET surface area using nitrogen adsorption isotherms at different pressures. The BET surface area provides information on the total surface area of the material, including both external and internal surfaces.
Once you have obtained the BET surface area, you can use the t-plot or BJH (Barrett-Joyner-Halenda) method to analyze the adsorption isotherm data at low relative pressures and obtain the pore volume and pore size distribution of the material. The pore volume gives the amount of void space in the material, and the pore size distribution provides information on the size and shape of the pores.
Regarding the second part of your question, if a material shows pore diameter less than 2nm (around 1.8 nm) but follows H4 hysteresis, it is typically considered as microporous. This is because H4 hysteresis is often observed in materials with small, slit-like pores or narrow channels, which are characteristic of microporous materials. However, it's important to note that the classification of a material as microporous or mesoporous can depend on various factors, including the method of analysis and the criteria used to define pore size ranges.
Dear Kaushik Shandilya
I have done the BET analysis. But the above data was observed after BET characterization. Is it possible the material is having both type of pores (i.e., micropores and mesopores)?
We cannot answer for your material, or for your data which we have not seen, but many real microporous materials also have mesopores.
Even "purely microporous" structures may have mesoporous voids in between the particles.
The IUPAC report mentions a couple of other classes of material which can show H4 hysteresis ( doi: 10.1515/pac-2014-1117 )
Article Physisorption of gases, with special reference to the evalua...
[I will note that it can be confusing to talk of BET measurement when you are really referring to full physisorption isotherms... ]
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