Researchers at the School of Engineering of the Hong Kong University of Science and Technology (HKUST) have developed a sustainable and controllable strategy to manipulate interfacial heat transfer, paving the way for improving the performance of eco-friendly cooling in various applications such as electronics, buildings and solar panels.
One emerging field of study is passive cooling using metal-organic frameworks (MOFs), which are porous materials that can capture water vapor from the air and be used to increase energy efficiency in room temperature space cooling applications. However, MOFs typically exhibit low thermal conductivity, making them poor thermal conductors. Moreover, the presence of adsorbed water molecules in MOFs further reduces their effective thermal conductivity. This limitation leaves little room for manipulating the intrinsic thermal transport properties of MOFs to enhance their cooling perfo
Through comprehensive frequency-domain thermoreflectance (FDTR) measurements and molecular dynamics (MD) simulations, they have demonstrated a remarkable improvement in interfacial thermal conduction (ITC) between the contacted substrate and MOFs. The ITC was increased from 5.3 MW/m2K to 37.5 MW/m2K, representing an enhancement of approximately 7.1 times. Effective enhancements are also observed in other Au/MOF systems.
The research team attributes this improvement to the formation of dense water channels facilitated by the adsorbed water molecules within MOFs. These channels serve as additional thermal pathways, significantly enhancing thermal energy transfer across the interfaces. Further analysis found that the adsorbed water not only activates the high-frequency vibrations, but also increases the overlap of vibrational density of states between the substrate and MOF which enhances the thermal energy dissipation from the substrate to MOF, highlighting the bridge effect of the adsorbed water molecules.