In our prior study, we employed several in-situ techniques to investigate the thermal evolution of the structure of a Mg-Al-CO3 layered double hydroxide (LDH) under an inert atmosphere and proposed a model to describe the structural evolution of the Mg-Al-CO3 LDH structure. In this paper we present results of our ongoing investigations with these materials pertaining to their sorption characteristics and thermal reversibility under both inert and reactive atmospheres. The experimental observations are shown to be consistent with the structural model for the LDH previously proposed. The structure, sorption characteristics, and thermal reversibility of these materials are of importance in their use for the preparation of CO2-permselective membranes for high-temperature membrane reactor applications.