Molecular Simulation Study of CO₂ Adsorption and Sequestration on Clay Minerals under Geological Conditions

Geological utilization and sequestration of CO₂ are considered among the most effective methods for reducing carbon emissions. Clay minerals, as dominant diagenetic components in sedimentary formations, play a crucial role in CO₂ geological sequestration owing to their large surface area and strong adsorption capacity. In this study, the adsorption and sequestration mechanisms of CO₂ on typical clay minerals, including illite and kaolinite, were systematically investigated under geological temperature and pressure conditions representative of the eastern Junggar Basin using grand canonical Monte Carlo and molecular dynamics simulations. The results demonstrate that CO₂ adsorption capacity is governed by the coupled effects of mineral type, pore size, temperature, and pressure. Illite exhibits approximately 1.4 times higher CO₂ storage capacity than kaolinite, attributed to its stronger thermodynamic affinity and higher adsorption heat. Elevated temperature reduces CO₂ adsorption, whereas increased pressure promotes it. In micropores smaller than 2 nm, confinement effects dominate and yield stable monolayer adsorption, while in mesopores, multilayer adsorption and coexistence of adsorbed and free CO₂ phases occur as the pore size increases. The adsorbed phase proportion is consistently higher in illite, implying more stable and efficient CO₂ trapping. These findings provide molecular-level insights into CO₂-clay mineral interactions and establish a theoretical foundation for evaluating storage capacity, trapping stability, and caprock integrity, offering practical guidance for the safe and efficient implementation of CO₂ geological sequestration projects in the eastern Junggar Basin, China.