Dynamic analysis of adsorbate behavior in nanopores: Liquid bridge formation, cavitation, and contact angle evaluation via molecular dynamics simulations

To explore the internal transport mechanisms and evolutionary processes within nanopore, molecular dynamic simulations were employed to explore the formation of liquid bridges and the evolution of menisci. The adsorption–desorption isotherms were obtained, and the dynamic behavior of the adsorbate was analyzed. Results revealed two distinct processes governing the behavior of the adsorbate within nanopore. At low pressure ratios, a molecular adsorption layer initially grows continuously on the pore surface. As the pressure ratio increases, an additional mechanism emerges, characterized by the formation of a liquid bridge near the nanopore mouth. This leads to pore filling as the liquid bridge expands and retreats towards the pore's closed end. During desorption, cavitation occurs, which can be characterized as an activation process. Once initiated, cavitation intensifies, progressively increasing the number of cavities. The convergence of these cavities undermines the stability of the liquid bridge, ultimately resulting in its collapse and the rapid evaporation of the adsorbate molecules. Additionally, we further calculated the contact angle at the vapor–liquid interface using the Kelvin equation. The results indicated a deviation of less than 5 % compared to our simulations, suggesting that the Kelvin equation is applicable for materials with pore sizes of at least 3.6 nm. © 2024 Elsevier B.V.