The Ba form of a silicoaluminophosphate-34 (SAPO-34) zeolite membrane was synthesized and investigated for carbon dioxide (CO 2 )/nitrogen (N 2 ) separation with low CO 2 concentration (as low as 5) in the feed. The effects of the separation temperature, CO 2 concentration in the feed, and pressure difference on the separation performance of the Ba form of a SAPO-34 zeolite membrane were investigated. A CO 2 gas permeance of 17.5 � 10 -7 mol/m 2 ·s·Pa and a CO 2 /N 2 separation selectivity of 78 were attained for the Ba form of a SAPO-34 zeolite membrane at 100 kPa pressure difference, 303 K, and 5 CO 2 concentration in the feed. With low CO 2 concentration (5) in the CO 2 /N 2 mixture, the Ba form of a SAPO-34 zeolite membrane was efficient in CO 2 /N 2 separation and displayed good stability for the separation performance of CO 2 /N 2 gas mixtures, in a gas separation durability test up to a total durability test time of 58 h. © 2018 American Chemical Society.