Molecular dynamics simulation study on the thermophysical properties of <i>n</i> -eicosane@IRMOFs composite phase change materials

Composite phase change materials (CPCMs) have emerged as key functional materials for thermal management. Understanding the thermophysical properties of these composites is critical, especially for CPCM based on metal–organic frameworks (MOFs). In this study, we investigate the thermal properties of n-eicosane confined within isoreticular metal–organic frameworks (IRMOFs), sharing the same topology but different organic ligands. Results indicate that n-eicosane@IRMOF-3 exhibits a significant enhancement of thermal conductivity after the composite, and the thermal conductivity of n-eicosane@MOFs is heavily influenced by temperature. Furthermore, the melting point of such CPCMs increased by about 16-25 K to 325–335 K compared to the bulk n-eicosane, and the enthalpy during phase change decreases by 54.1%−64.3%. The thermal conductivity of n-eicosane within CPCMs displays a distinct crossover near the phase transition temperature, whereas the heat capacity grows with the temperature increase. Below the melting point, it slightly decreases compared to bulk n-eicosane, whereas above the melting point, a significant enhancement of thermal conductivity is observed. Investigation of intermolecular interactions confirms the dominance of van der Waals forces between the supported materials and n-eicosane. These findings explain how thermophysical properties evolve in nanoconfined CPCMs, providing guidance for the design of high-performance MOF-based energy storage materials.