Nature of Chemisorbed CO2 in Zeolite A

Formation of CO32– and HCO3– species without the participation of the framework-bridging oxygen atoms (−O−) upon chemisorption of CO2 in zeolite |Na12|-A is revealed. The transfer of O and H atoms is very likely to have proceeded via the involvement of residual H2O or −OH groups. A combined study by the solid-state 1H and 13C MAS NMR, quantum chemical calculations, and in situ infrared spectroscopy showed that the chemisorption mainly occurred by the formation of HCO3–. However, at a low surface coverage of physisorbed and acidic CO2, a significant fraction of HCO3– was deprotonated and transformed into CO32–. We expect that a similar chemisorption of CO2 would occur for low-silica zeolites and other basic silicates of interest for capture of CO2 from the gas mixtures.