Context <p>High carbon emissions have become a major problem perplexing human society, and the use of shale for CO₂ storage has a broad application prospect and significance. In this paper, a SiO₂- Al₂O₃ heterostructure model representing clay shale is established, and the adsorption mechanisms of CO₂ in clay shale are studied systematically by means of grand canonical Monte Carlo (GCMC), molecular dynamics (MD) and density functional theory (DFT). The findings indicate that the system's equilibrium shifts toward adsorption as pressure increases, enhancing gas uptake. Conversely, rising temperature favors the desorption equilibrium, thereby reducing the overall adsorption capacity. Higher water content reduces CO₂ adsorption capacity in hydrous SiO₂-Al₂O₃ nanopores. For every 5 wt% increment in water content, the CO₂ adsorption amount decreases by approximately 18.6%. The density profiles show that the interaction between H₂O and adsorption sites on the shale surface is stronger than that of CO₂. The radial distribution functions indicate the difference of CO₂ distribution between SiO₂ region and Al₂O₃ region and reveal the effect of water on Al₂O₃ region is greater than that of SiO₂ region. This study has an in-depth exploration of the adsorption rule and migration mechanism of CO₂ in clay shale, which may contribute preliminary theoretical insights for optimizing CO₂ adsorption and storage.</p> Method <p>The simulation software employed in this study is Materials Studio, and the associated force field utilized is COMPASS III. The adsorption configurations are obtained from the Sorption module and molecular dynamics simulations are performed on it by using the Forcite module with the NVT ensemble. Based on the DFT, molecular optimization and performance metrics analysis are all calculated using the DMol³ module.</p>