From Molecular Clusters to Liquid Phase Transition: Predictive Modeling of Adsorption and Evaporation in Nanoporous Materials

This study integrates molecular dynamics simulations with the Zeta adsorption isotherm to elucidate liquid formation and transport in porous materials. Two critical processes, pore filling and condensate evaporation, are analyzed. The Zeta model accurately predicts adsorption at low relative pressures (<0.45) using parameters from a nonporous surface. Simulations reveal that the vapor-to-liquid phase transition proceeds via molecular clusters nucleation and coalescence. A predictive capillary condensation model was developed to capture the staged evolution of cluster growth. An augmented Young–Laplace equation incorporating disjoining pressure effects reveals distinct regimes: evaporation suppression in the adsorbed film zone (governed by surface interactions) and enhanced mass transfer in the intrinsic meniscus region (dominated by capillary forces). This pressure gradient-driven mechanism enables continuous liquid replenishment while maintaining structural stability. This multiscale approach bridges molecular interactions with macroscopic transport, offering quantitative insights for optimizing porous materials in applications such as thermal energy storage and catalysis.