Cheng Ruihuan, Wei Wei, Zhang Jincheng, Li Song
Department of New Energy Science and Engineering, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
China-EU Institute for Clean and Renewable Energy, Huazhong University of Science and Technology, Wuhan 430074, China.
J Phys Chem B. 2023 Nov 2;127(43):9390-9398. doi: 10.1021/acs.jpcb.3c04372. Epub 2023 Oct 18.
Metal-organic frameworks (MOFs) with ultrahigh specific surface area and porosity have emerged as promising nanoporous materials for gas separation, storage, and adsorption-driven thermal energy conversion systems such as adsorption heat pumps. However, an inadequate understanding of the thermal transport of MOFs with adsorbed gases hampers the thermal management of such systems in practical applications. In this work, an in-depth investigation on the mechanistic heat transfer performance of three topological zeolitic imidazolate frameworks (ZIFs) upon hydrogen, methane, and ethanol adsorption was carried out by molecular dynamics simulations. It is revealed that the trade-off between the additional heat transfer pathway and phonon scattering resulting from adsorbed gases determines the thermal conductivity of ZIFs. It is found that the increased thermal conductivity with the increased number of adsorbed gases is correlated with the overlap energy between the vibrational density of states of gases and Zn atoms, suggesting the additional heat transfer pathways formed between gas molecules and frameworks. Moreover, the gas spatial distribution and diffusion also impose remarkable impacts on the heat transfer performance. Both the homogeneous gas distribution and the fast gas diffusion are conducive to form effective heat transfer pathways, leading to enhanced thermal conductivity. This study provides molecular insight into the mechanism of the improved thermal conductivity of ZIFs upon gas adsorption, which may pave the way for effective thermal management in MOF-related applications.
具有超高比表面积和孔隙率的金属有机框架材料（MOF）已成为用于气体分离、存储以及吸附驱动的热能转换系统（如吸附式热泵）的有前景的纳米多孔材料。然而，对吸附气体的MOF的热输运理解不足阻碍了此类系统在实际应用中的热管理。在这项工作中，通过分子动力学模拟对三种拓扑结构的沸石咪唑酯骨架材料（ZIF）在吸附氢气、甲烷和乙醇时的传热机理性能进行了深入研究。结果表明，吸附气体导致的额外传热途径与声子散射之间的权衡决定了ZIF的热导率。发现随着吸附气体数量增加热导率增加与气体和锌原子的振动态密度之间的重叠能量相关，这表明气体分子与骨架之间形成了额外的传热途径。此外，气体的空间分布和扩散也对传热性能产生显著影响。均匀的气体分布和快速的气体扩散都有利于形成有效的传热途径，从而提高热导率。这项研究为气体吸附时ZIF热导率提高的机理提供了分子层面的见解，这可能为MOF相关应用中的有效热管理铺平道路。
