Reversible CO₂ Absorption by the 6H Perovskite Ba₄Sb₂O₉

A novel compound for carbon capture and storage (CCS) applications, the 6H perovskite Ba₄Sb₂O₉, was found to be able to absorb CO₂ through a chemical reaction at 873 K to form barium carbonate and BaSb₂O₆. This absorption was shown to be reversible through the regeneration of the original Ba₄Sb₂O₉ material upon heating above 1223 K accompanied by the release of CO₂. A combined synchrotron X-ray diffraction, thermogravimetric, and microscopy study was carried out to characterize first the physical absorption properties and then to analyze the structural evolution and formation of phases in situ. Importantly, through subsequent carbonation and regeneration of the material over 100 times, it was shown that the combined absorption and regeneration reactions proceed without any significant reduction in the CO₂ absorption capacity of the material. After 100 cycles the capacity of Ba₄Sb₂O₉ was ∼0.1 g (CO₂)/g (sorbent), representing 73% of the total molar capacity. This is the first report of a perovskite-type material showing such good properties, opening the way for studies of new classes of inorganic oxide materials with stable and flexible chemical compositions and structures for applications in carbon capture