Session: 11-60-01: Simulations of Thermal Transport in Nanostructures and across Interfaces

Paper Number: 119868

119868 - Direct Observation of Tunable Thermal Conductance at Solid/porous Crystalline Solid Interfaces Induced by Water Adsorbents 

Cooling is essential in various fields, from digital hardware (e.g., electronic cooling) to building cooling in everyday life. Passive cooling using metal-organic frameworks (MOFs) has recently gained attention for its eco-friendly and zero-electricity properties in cooling electronics, solar panels, and buildings. However, the cooling performance strongly depends on the thermal conductivity of MOFs and interfacial thermal conductance (ITC) between the objectives and MOFs. Unfortunately, MOFs typically have a low thermal conductivity below 2 W/mK at room temperature and are considered poor thermal conductors. The presence of adsorbed water molecules in MOFs further reduces the effective thermal conductivity. For instance, Babaei et al. reported a decrease in the thermal conductivity of MOF-199 (HKUST-1) from 0.69 W/mK to 0.21 W/mK when water molecules are adsorbed. Therefore, there is limited space to manipulate the intrinsic thermal transport properties of MOFs. Designing an effective interfacial heat dissipation channel between the objectives and MOFs may be the only feasible way to improve cooling performance. Interfacial engineering techniques, such as adhesion layers, nanostructures, chemical modification, and self-assembled monolayers, have been widely applied to enhance ITC. However, controlling the structures of buffer layers at an atomic level remains a significant challenge and limits their applications.

Here, we design a strategy by utilizing the water adsorption-desorption process in porous metal-organic frameworks (MOFs) to tune the interfacial heat transfer. We observe a changeable thermal conductance across the solid/porous MOFs interfaces owing to the dense water channel formed by the adsorbed water molecules in MOFs. Our experimental results using FDTR show that the interfacial thermal conductance of Au/Cu₃(BTC)₂ heterointerfaces can be improved from 5.3 MW/m²K to 37.5 MW/m²K (~7.1 times) via this strategy, where Cu₃(BTC)₂ is a typical porous MOF and usually referred to as HKUST-1. Our MD simulations further show that the surface tension of the Au layer will cause the adsorbed water molecules in HKUST-1 to gather at the interfacial region. The dense water channels formed by the adsorbed water molecules in HKUST-1 serve as additional thermal pathways and enhances the thermal energy across the interfaces significantly. Besides, the vibrational transmission coefficient function calculated by the frequency domain direct decomposition method (FDDDM) further demonstrates that the thermal energy can be easily dissipated from Au to the MOF with adsorbents owing to the bridge effect of the adsorbed water molecules. Our findings provide a new concept for tailoring thermal transport at the solid/porous MOFs heterointerfaces which will largely benefit MOF-related applications.

Presenting Author: Guang Wang The Hongkong University of Science and Technology

Presenting Author Biography: Mr. Guang WANG received his B.S in physics at Tongji University in 2017, and then received his M.S degree in physics at Tsinghua University in 2020. He is now a Ph.D. candidate in the Department of Mechanical and Aerospace Engineering at the Hongkong University of Science and Technology. He focused on understanding and engineering fundamental thermal transport phenomena and new materials for applications in thermal management, energy, and electronics.

Authors:

Hongzhao Fan The Hongkong University of Science and Technology
Jiawang Li The Hongkong University of Science and Technology
Zhigang Li The Hongkong University of Science and Technology
Yanguang Zhou The Hongkong University of Science and Technology
Guang Wang The Hongkong University of Science and Technology