A Cluster Based Cooperative Kinetic Model for CO2 Adsorption on Amine Functionalized Metal–Organic Frameworks

Abstract

A new model for the adsorption kinetics of CO2 on amine functionalized metal–organic frameworks Mg2 (dobpdc) and Mn2 (dobpdc) is proposed. The equilibrium adsorption is evaluated using the cooperative lattice theory of Kundu et al. The lattice theory provides a microscopic interpretation of adsorption behavior on the basis of the state of adsorbed CO2: singly adsorbed, chain ends, and chain interiors. On this basis, the proposed kinetic model accounts for the kinetics of singly adsorbed CO2, as well as the kinetics of adsorption into chains. These two kinetic paths have separate yet coupled rate laws. This allows for the accurate description of complex kinetic phenomena observed in low partial pressure CO2 breakthrough curves on mmen-Mg2 (dobpdc). In addition to good numerical agreement with measured data, the approach developed in this work provides a needed microscopic interpretation of measured kinetic data in these systems. This microscopic picture may allow for more targeted material design and a pathway to include additional factors such as the effect of humidity on CO2 adsorption and kinetics.