Influence of adsorbed gas molecules on thermal transport in metal- organic framework HKUST-1

HZ Fan and ZG Li and YG Zhou, PHYSICAL REVIEW APPLIED, 23, 054006 (2025).

DOI: 10.1103/PhysRevApplied.23.054006

Metal-organic frameworks (MOFs) have been regarded as promising candidates for gas fuel storage. It is known that a large amount of heat will be released (exothermic) or adsorbed (endothermic) during the gas storage process, which leads to a large temperature change in the system and, in turn, affects the usable gas uptake capacity. It is therefore necessary to investigate thermal transport in gas-adsorbed MOFs. By using atomistic simulations, we here systematically study the thermal transport in CH4-, C2H6-, and H2-adsorbed MOF-199, which usually refers to HKUST-1. We find that the room temperature thermal conductivity of CH4-and C2H6-adsorbed systems first decreases greatly to approximately 40% of the original value and then converges with the amount of adsorbed gas molecules. However, for H2-adsorbed systems at room temperature, the corresponding thermal conductivity decreases from approximately 1.37 W/mK to approximately 0.69 W/mK and then increases to approximately 1.16 W/mK with increase of the amount of adsorbed H2 molecules. It is further shown that the thermal conductivity contributed by the HKUST-1 framework decreases monotonously with increase of the amount of adsorbed gas molecules owing to the increased scattering between the HKUST-1 framework and adsorbed gas molecules. The thermal energy transferred by the adsorbed CH4 and C2H6 (H2) molecules increases a little (greatly) with increase of the amount of adsorbed gas molecules. This is because the adsorbed H2 molecules can diffuse farther in HKUST-1 than the adsorbed CH4 and C2H6 molecules, which is caused by the small size of H2 molecules and weak interactions between the HKUST-1 framework and H2 molecules. Therefore, the adsorbed H2 molecules can effectively transfer thermal energy through both conductive and diffusive pathways, and the thermal conductivity of the saturated-H2 system is much higher than that of the saturated-CH4 and saturated-C2H6 systems. Our results provide a physical picture of thermal transport in gas-adsorbed MOFs, which should facilitate the design of high-performance MOF-based gas storage systems.

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