One Ca2+ Site in CaNaY Zeolite Can Attach Three CO2 Molecules.

Abstract

To design efficient CO2 capture materials, it is necessary to ensure a high adsorption capacity. We recently reported that one Na+ site in NaY zeolite can attach two CO2 molecules. However, the process is not suitable for practical use because it proceeds at a low temperature. Here, we present results on CO2 adsorption on CaNaY zeolites, demonstrating that one Ca2+ site can attach three CO2 molecules. The ν3(13CO2) mode arising from the natural 13C abundance allows for easy infrared monitoring of the processes: it appears at 2298, 2294, and 2291 cm-1 for the complexes with one, two, and three CO2 ligands, respectively. The 12CO2 molecules in the polyligand complexes interact vibrationally, leading to the split of the ν3(12CO2) modes. At ambient temperature, Ca2+(CO2)2 complexes predominate at >1 mbar CO2 and triligand species begin to form at 65 mbar. The obtained results show that CaY zeolites can be very effective CO2 capture materials.