The kinetics of absorption of dry and wet CO2 of polyethylenimine-functionalized single walled carbon nanotube (PEI-SWNT), graphite oxide (PEI-GO), and fullerene C-60 (PEI-C-60) were analyzed in detail using six different kinetic models: Elovich, pseudo-1st-order, pseudo-2nd-order, pseudo-n(th)-order, modified Avrami, and extended model. It is found that PEI-SWNT follows a pseudo-2nd-order kinetics both in dry and wet CO2, whereas PEI-GO follows a modified Avrami kinetics with values of the parameter m close to 1, being this a simple correction to a pure pseudo-1st-order kinetics. The kinetics of PEI-C-60 appears to be more complex and slower due to gas diffusion limitations. A comparison of the kinetics of PEI-GO and PEI-SWNT supports the hypothesis that carbon scaffolds of higher curvature can activate and enhance the CO2 absorption capability of PEI.