P. Ying, J. Zhang, X. Zhang, Z. Zhong, Impacts of Functional Group Substitution and Pressure on the Thermal Conductivity of ZIF-8. The Journal of Physical Chemistry C 124, 6274-6283 (2020).

Metal–organic frameworks (MOFs) are promising candidates as natural gas adsorbents because of their porous feature and high structural tunability. In the gas adsorption/desorption process, MOFs are often under complicated physical environments, such as varied pressure and temperature; however, limited attention has been paid to the effect of pressure on their thermal properties. In this work, taking ZIF-8 with four different functional groups (−H, −CH3, −Cl, and −Br) as an example, we investigate the influence of functional group substitution and pressure on the thermal conductivity of MOFs through equilibrium molecular dynamics simulations. A reduction in thermal conductivity induced by the functional group substitution is observed, which is caused by a damping effect of the acoustic mismatch. Regarding the impact of pressure, the thermal conductivity of ZIF-8 is found to decrease first with increasing hydrostatic pressure. When the pressure exceeds a critical value, a sudden rise is observed in the thermal conductivity of ZIF-8 because a phase transformation from the porous phase to the dense phase is found in this process. The complicated influence of pressure on thermal conductivity is explained by a competition between the aggravation of phonon scattering and the enhancement of volumetric heat capacity in ZIF-8 with increasing pressure. This work is expected to provide molecular insights into the functional group- and pressure-dependent thermal transport of MOFs and thus facilitate their applications in energy storage and gas absorption.

Download paper here