CO2 facilitated transport was studied using a membrane with amine sites covalently bound to the polymer backbone and ion exchange membranes which have amine complexing agents (carrier) as counterions. The two types of membranes were compared, and several amine functionalities for the ion-exchange membrane were studied. Although the covalently bonded membranes had a larger absorption capacity than amine functionalized Nafion ion-exchange membranes, the facilitation effect of CO2 through the covalently bonded membrane was very small (less than 1.5 at 10 kPa CO2 partial pressure) compared with the ion-exchange membrane (8.0 at 11 kPa CO2 pressure with mono protonated ethylenediamine carrier form in Nafion 117). A simulation model for the covalently bound membranes was developed to understand the results. The facilitation effect depends largely on carrier diffusivity, and reactive diffusion through the covalently bonded membrane is much slower than counterion diffusivity through the ion-exchange membrane. The ethylenediamine carrier exhibited a large facilitation effect in a Nafion 117 membrane. Other secondary or hindered diamines exhibited a small facilitation effect. For a swollen Nafion membrane, both ethylenediamine and ethylenediamine derivatives showed a high facilitation effect, and a secondary diamine produced a facilitation factor of 4.09 and a CO2 flux of 1.02 x 10(-8) mol/cm(2) s at 22.5 kPa CO2 pressure in the feed.