Yes, for calculating the heat of adsorption you use the Clausius-Clapeyron equation and the data from the isotherms measured at 2-3 different temperatures (if it´s 3 or even more, better). Chemisorption will give you much higher values of heat of adsorption than phyisisoprtion, which normally has values lower than 30 kJ/mol for CO2.

For the kinetics, you have to take into account also the porosity in your material and the fact that maybe those amino groups are impeding the easy acces to the porosity

What if I can't measure the CO2 adsorption isotherms at different temperatures (0 degC only)?

Do you recommend any alternative parameter I could refer to?

So, you mean that the slower kinetic exhibited by amino-functionalised materials is simply due to pore blockage rather than chemisorption?

Chemisorption this is the sorption between sorbate and sorbent with formation of new products. What may be the mechanism of chemisorption CO2 on amine groups?

May be will you try to make desorption? Or maybe you make to investigation of IR-spectrum carbon before and after sorption for identify of mechanism of sorption.

CO2 capture by amine-functionalized materials mimics the traditional absorption process by amine solutions. Primary and secondary amines react with CO2 to produce carbamates through the formation of zwitterionic intermediates.

The slower kinetics can be due to both things, there are papers on CO2 capture by amine functionalized silicas were you can check that.

Chemisorption is also characterized for giving you higher selectivity versus other gases (the ratio CO2/N2 should be high); also for desorption, you will need higher temperatures than if you had only phyisisorption

yes surely. with calculation of adsorption energy (E),Standard Gibbs free

energy of adsorption change (∆G0 ), enthalpy of adsorption change (∆H0

) and  changing operative conditions  such as T, pH and..

The problem is that I can't measure the CO2 adsorption isotherms at different temperatures (so I suppose I can't use the Clausius Clapeyron equation).

What about the energy of adsorption (E0) calculated by applying DR method to the CO2 adsorption isotherms at 0 degC? Could it be an alternative parameter to distinguish physisorption and chemisorption?

you should do this set of experiment to your aim. It's unavoidable. DR is a proper way to estimate of physisorption and chemisorption. I used it in my new paper that will publish soon. why you cant do CO2 adsorption isotherm?

My instrument can measure CO2 adsorption isotherms at 0 C only. So, which are the E0 (DR) values typical of physisorption/chemisorption?

Please do be careful with the Clausius-Clapeyron equation: A requirement for being able to apply the equation is complete reversibility, meaning in the evaluated pressure range the adsorption branch has to be the same as the desorption branch. So, if you have chemisorption, that is probably not the case. Is your isotherm reversible? The slower kinetics seem reasonable, both due to possible reaction and some temporary pore blocking due to your functionalization. Don't you have access to a volumetric adsorption apparatus? Many of them offer chemisorption measurement modes, also temperature variation is easily achievable by using ice, dry ice mixtures, external thermostats for room temperature etc

When I measure the CO2 adsorption isotherms with my volumetric adsorption apparatus I don't get any desorption branch so I can't tell if it is reversible or not.

Is the apparatus not able to measure desorption or does that only occur with your material? When using TGA, could you measure the desorption by switching to nitrogen  flow after the plateau is reached?

It is just that I've never tried. Yes, I usually perform a desorption stage first under CO2 (increasing T) and then finally by switching to N2..

What about the measurement of CO2 adsorption isotherms at room T, do I still need to soak the cell in a bath (e.g. water at room T rather than iced water)?

If you increase the temperature during desorption, you could fake reversibility that is not really there. You could maybe switch to N2 at constant temperature and see if you reach m0 again. When measuring isotherms, the correct way is always to ensure constant temperature. For a qualitative measurement you could omit any bath, but for the data to be valid, you'd have to attach a water bath whose temperature is controlled by a thermostat or you can not call that an isotherm.

to calculate of DR you should do experiment in various T, however I wrote a summarized text about DR.I generally agree with Stella comment in  your case.      

TheDubinin–Radushkevich isotherm is an empirical model initially conceived for the adsorption of subcritical vapors onto microporous solids following a certain pore filling mechanism. It is generally applied to express the adsorption mechanism with a Gaussian energy distribution onto a heterogeneous surface.The approach was usually applied to distinguish the physical and chemical adsorption of metal ions, with its mean free energy E per molecule of adsorbate (for moving a molecule from its location in the sorption space to the infinity) :It is established that when the magnitude of E is between 8 kJ. mol-1 and 16 kJ. mol-1, the adsorption type can be explained by ion-exchange; and when the adsorption energy is lower than 8 kJ.mol-1, the type of adsorption can be considered as physical adsorption.

Could you recommend any paper related to the application of DR method to CO2 adsorption isotherms in order to discriminate physisorption and chemisorption of CO2?

Most of the my references are in case of metal ion, but I could find these papers among of them, I hope to be useful .