Kinetics of CO₂ Adsorption and Deformation in Microporous Carbon: A Classical DFT Approach

Adsorption kinetics plays a key role in numerous industrial applications, including gas separation by molecular sieving, water purification, gas storage, and TSA processes. It is accompanied by adsorption-induced deformation, in which molecules adsorbed onto the pore surfaces generate stress, resulting in dimensional changes in the material. Among other things, they control the permeability of coal, influence material degradation during TSA, and complicate the characterization of aerogels. In this work, we present a diffusion-based kinetic model that relies on classical density functional theory to calculate the required equilibrium properties and to account for intraparticle diffusion, external surface barriers, and heat effects. We measured a series of CO₂ uptakes on a carbon molecular sieve (Shirasagi MSC CT-350) at 293 K to verify our model and assess its predictive capabilities. Additionally, data from the literature were used to test the precision of the description of adsorption-induced deformation. We showed that our model can describe and predict both adsorption and deformation kinetic measurements. After the approach was validated, we studied the dependence of strain uptakes on PSD, mass transfer mechanisms, and temperature effects. Our results demonstrate the potential of the proposed approach and can be used to interpret experimental data on adsorption and deformation.