The processing and characterization of a novel membrane system for CO, separation is described. The membrane was made of lithium zirconate (Li2ZrO3), which has a potential to react reversibly with CO2 molecules at high temperatures. The reaction of Li2ZrO3 with CO2 essentially produced two electrolyte materials in situ. One of them, Li2CO3, is capable of carrying CO2 and the other, ZrO2, is a well-known O-2 ion conductor. This combination of selective reaction and electrolyte conduction permitted the design of a membrane system capable of selective CO2 steady-state permeation across the membrane. Using the membrane, a separation factor of 4.9 was measured between CO2 and CH, gas molecules at a temperature of 600 degrees C. The measured separation value of 4.9 is very high compared with the Knudsen diffusion limit of 0.6 and therefore clearly supports the use of the membrane system for selective separation of CO2.