(349f) Defect-Induced Increase of Thermal Conductivity in Metal-Organic Frameworks

Metal-organic frameworks (MOFs) have been widely researched for their potential applications in gas storage, sensing, and separations. However, one of the major challenges in these applications is managing the thermal energy generated during the exothermic adsorption process. Previous studies have explored the influence of various factors on the thermal conductivity of MOFs, but have not fully considered the effects of defects which are inherently present in synthesized MOF crystals. In this work, we investigate the influence of randomly distributed missing linker and missing cluster defects on the thermal conductivity of two well-known MOFs, HKUST-1 and UiO-66, using molecular dynamics simulations and the equilibrium Green-Kubo method. We also examine the thermal conductivity of three experimentally determined correlated defect nanodomains of UiO-66 with underlying topologies of bcu, reo, and scu nets. Our findings show that both randomly introduced missing linker and missing cluster defects reduce thermal conductivity, while the correlated missing linker defect nanodomain (bcu topology) exhibits a higher thermal conductivity than pristine UiO-66 due to the removal of perpendicular linkers acting as phonon scattering sources. Our results are further supported by harmonic lattice dynamics calculations, which reveal an increase in phonon group velocity. Our study demonstrates the potential of controlling defects to tune the thermal conductivity of MOFs and provides new insights into the underlying mechanisms of thermal transport in these materials.