CO2 Adsorption in the RHO Family of Embedded Isoreticular Zeolites

Abstract

More effective carbon capture techniques and materials are still required to combat ever-increasing anthropogenic CO2 emissions. Here we report the CO2 adsorption isotherms, at 298-373 K and 0-1.0 bar, on various alkali cation forms of the five members of the RHO family of embedded isoreticular zeolites (i.e., Rho, PST-29, ECR-18, ZSM-25, and PST-20). The adsorption behavior of CO2 on this new family was found to differ significantly according not only to the zeolite framework flexibility but also to the type of extraframework cation. Among the zeolites studied here, the adsorption isotherms on the Cs+-tetraethylammonium cation form of ZSM-25 and PST-20 are characterized as one-step, with working capacities of 1.3-1.4 mmol g(-1) at 298-343 K, which may have a clear advantage for the industrial temperature swing adsorption process. These two zeolite adsorbents also have large CO2 selectivities (ca. 100 and 50, respectively) over N-2 and CH4, as well as good long-term stability.