Steam Isotherms, CO2/H2O Mixed-Gas Isotherms, and Single-Component CO2 and H2O Diffusion Rates in CALF-20

Abstract

Calgary Framework 20 (CALF-20) has emerged as a metal–organic framework (MOF) that is steam-stable and exhibits selective CO₂ physisorption over water vapor, which makes it a candidate for industrial-scale CO₂ capture from flue gases. In this work, multicomponent CO₂/H₂O adsorption data show that the α-to-β phase transformation has little impact on the multicomponent CO₂ adsorption capacity of CALF-20. Also, H₂O isotherms up to 175 °C reveal only limited changes in the water capacity as temperature increases above 45 °C. CO₂ and H₂O single-component diffusion rates were measured via concentration swing frequency response. The results show that the diffusion rate of water through CALF-20 is similar to that of water diffusion in the highly water-permeable MOF-333, as well as BPL-activated carbon. The data provides key insight into the fundamental thermodynamic and mass transfer parameters that govern the separation of CO₂ and H₂O using CALF-20 and provides quantified parameters that can be used to model adsorption systems based on CALF-20.