Volume 12 Issue 1 ( March 2025)

With the advancement of porous materials, physical adsorption has found extensive applications in environmental and energy-related fields. However, capturing the detailed adsorption process through experiments remains challenging, and comprehensive studies of adsorption kinetics using molecular simulations are still limited. This study employs molecular dynamics simulations to investigate methane adsorption in MOF-5 across temperatures (200 K, 270 K, 300 K) and pressures (5–50 bar). Equilibrium adsorption uptake agrees well with experimental data, where the mean relative error is less than 6 %, validating the simulation approach. Adsorption energy and self-diffusion coefficients reveal the saturation of high-energy sites at low pressure and the transition of methane to a supercritical state with reduced mobility at higher densities. Adsorption dynamics curves, fitted with Sultan’s model, generally match the simulations but give higher initial value in high-pressure stages, reflecting model limitations, where the root mean square is around 0.1-0.3. Correlation analysis highlights the relationships among fitting parameters and equilibrium adsorption properties. Radial distribution functions reveal structural transitions, including multilayer adsorption and phase tendencies influenced by temperature and pressure. This comprehensive study demonstrates the effectiveness of molecular dynamics in modeling adsorption processes, offering insights into equilibrium properties, kinetics, and phase behavior, and providing a robust framework for future adsorption research.

Keywords: Adsorption kinetics; Methane; MOF; Molecular dynamics; Diffusion; Adsorption energy; Porous material