SAPO-34 seeds and membranes were functionalized with several organic amino cations, such as ethylenediamine, hexylamine, and octylamine. The successful incorporation of the amino groups in the SAPO-34 framework was confirmed by Fourier transform infrared (FTIR) and X-ray photoemission (XPS) spectroscopies. The resultant SAPO-34 membranes were evaluated for the separation of CO2/CH4 and CO2/N-2 gas mixtures. CO2/CH4 selectivities as high as 245, with CO2 permeances of similar to 5 x 10(-7) mol m(-2) s(-1) Pa-1 at 295 K and 138 kPa, were observed for an optimum ethylenediamine-functionalized membrane, which corresponded to a similar to 40% increase in the separation index, as compared to the nonfunctionalized SAPO-34 membrane. Similarly, the CO2/N-2 separation performance was highly improved with the incorporation of ethylenediamine. CO2/N-2 selectivities as high as 39, with CO2 permeances of similar to 2.1 x 10(-7) mol m(-2) s(-1) Pa-1 at 295K and 138 kPa, were observed for an optimum ethylenediamine-functionalized membrane, which corresponded to a similar to 167% increase in the separation index, as compared to the nonfunctionalized SAPO-34 membrane.