XPS will give you information about the chemistry of the extreme surface, not not that inside the pores. For "seeing" surface functions and quantifying them, you may do Boehm titration or temperature-programmed desorption. Besides this, pH in water and measurement of point of zero charge will teach you even more about the chemistry.

Alain

What about Raman Scattering?

Plz check attached files

XPS will give you information about the chemistry of the extreme surface, not not that inside the pores. For "seeing" surface functions and quantifying them, you may do Boehm titration or temperature-programmed desorption. Besides this, pH in water and measurement of point of zero charge will teach you even more about the chemistry.

Alain

Another way to evaluate the surface of the pores would be to measure water vapour isotherms. But as your pores are quite wide, I am not sure this will work. So I would go for Boehm titration or TPD (as Alain Celzard suggested).

Mercury intrusion porosimetry could be a good technique in your case. It works for pore characterisation up to 250 micrometers.

Dear all: Thanks a lot for your kind help, really sorry for my late response.

Anna: Could you please share me some related refs? thanks!

Hassan and Elia: It seems like that your suggestion is more related to physical structure of porous materials, rather than surface chemistry?

Alain and Peter:I tried XPS because it was used for similar purpose in a published paper (please check the attached file). and  I guess that the Boehm titration would tell some difference from samples,but is it possible to know what kind of functional groups exist at pore surfaces? and it would be better if the quantity is also measurable/calculable.

Many thanks again！

I was not expecting so large pores, and therefore my former reply is no more relevant. It was relevant for nm-sized pores, but not for large cells as those of polyHIPEs. Moreover, Boehm titration requires high surface area for being accurate, and in the present case the surface area will be quite low. In my opinion, the pores are so large that you don't have to expect some chemical differences depending on the zone of the material; differences happen when the pores are so narrow that steric hindrance prevents some surface functions to be in the pores. Nothing similar here.

Alain

Alain: Actually my situation is quite similar to that shown in the attached paper, except for the emulsifier-- they used amphiphilic copolymer while I used Pickering type particles with Janus structure. One side of the particles were modified with different functional groups, and my purpose is just to confirm that the difference could also be recognized in fabricated polyHIPEs, and all of the functional groups are exposed at pore surfaces rather than embedded in material matrix. The paper used XPS to prove that hydrophilic groups were exposed at pore surface, but it not worked in my case. So I just eager to know if there is any other characterization method or my trial was just failed. 

Yes, mercury intrusion technique is for physical pore size and volume measurements, I thought it was this the problem with your sample analysis. In concrete you would like to analyse the suface chemistry just inside the pore and not outside?

I cannot come up with an easy way at the moment, the  only techniques that I personally used are NH3 thermal programmed desorption or H2 thermal programmed desorption. With those you will have informations about the whole surface chemistry, not just inside the pores.

Elia: Measurement of the whole surface chemistry is also acceptable, as I just want to confirm that the functional groups are not embedded in material matrix, in that case, they are not "functional" any more.

So you suggest the TPD method? but I am worrying that the methodology can only show differences between samples, but can't tell me exactly what kind of functional groups it is?

Well, with H2-TPR you have hydrogen consumption in correspondence to the temperature of reduction of determined species (for examples metals, alloys, metalates or oxydes), and you can find lot of data in the literature helping you to identify what exatly is your functional group.

Same thing for NH3-TPD you can discriminate between stronger and weaker acid sites and compare to whats already been published, but to have a deeper understanding in my opinion is better to use probe molecule adsorption and than solid IR analysis:

for example to analyse acidic sites you can put a solid sample under pyridine vapour flow (attention when manipulating this) and then analyse it by solid IR and determine exatly to which kind of site the pyridine is bond to.

Depending on the functional group(s), pulse chemisorption with, i.e. CO, CO2, NH3, NO, NO2, 2-Amino propane and subsequent TPD of the absorbed material should help identifying the surface species. With 2-Amino propane, you would also need an MS attached to your measurement set-up to study the release of propene and NH3 from your sample.

Thanks for Elia and Markus's suggestion. So, for example, concretely, if the SAMPLE a has imidazole based ionic functional group, while the SAMPLE b just has hydrophobic alkyl chain on its pore surface, is it possible to distinguish? And what about different counter anion of SAMPLE a?

If there is no functional group on the alkyl chain, yes, it is possible to distinguish between sample "a" & "b". For imidazole functionality you might consider CO2 if it is more likely to have basic activity, NH3 if it is more likely to have acidic functionality.

I agree with Markus answer, for the counter anion though I think you have to use a different technique, like for example cation exchange and then an inverse titration to quantify it.