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Metal-organic frameworks (MOFs) are highly porous materials with tunable pore characteristics, making them attractive for applications in gas storage, separation, and catalysis [1]. Their unique properties have garnered significant attention in water vapor adsorption technology, crucial for humidity control, air conditioning, and heat pump systems. The Leibniz Supercomputing Center, in collaboration with IBM, has pioneered a water-cooled supercomputer utilizing a water adsorption heat pump (AHP) for efficient waste heat utilization [2].
This study investigates the V-type isotherms displayed by Aluminum-fumarate and CAU-10 MOFs in water vapor adsorption, a phenomenon not extensively studied. Unlike traditional materials like activated carbon, these MOFs exhibit a distinctive "S-shape" adsorption isotherm, indicating a complex adsorption mechanism requiring comprehensive modeling. Existing models, including the Mahle model [3] and Weighted dual-side-Langmuir model [4], while valuable, have limitations in accurately characterizing adsorption behavior, particularly at lower and higher relative pressures.
To address this, we propose a modified Mahle equation tailored for dynamic conditions and temperature- dependent V-type isotherms. Our model extends the range of reliable relative pressures up to 0.8, surpassing the capabilities of established models. Utilizing this model, we conduct dynamic simulations to gain insights into the water vapor adsorption behavior of Aluminum-fumarate and CAU-10 MOFs under diverse conditions.
This study holds significant implications for the advancement of MOF-based heat pump systems, offering a sustainable alternative to traditional refrigerant-based systems. By enhancing our understanding of MOFs' water vapor adsorption properties and developing accurate dynamic simulation models, this research paves the way for more energy-efficient and environmentally friendly heat pump systems. Considering the global drive for sustainable energy solutions, our findings mark a crucial step towards the broader adoption of MOFs in vital applications such as dehumidification, air conditioning, and heat pump systems.
References:
1. X. Chen, H. Gao, Z. Tang, G. Wang, Metal-Organic Framework-based Phase Change Materials for Thermal Energy Storage, Cell Reports Physical Science 1 (2020) 100218. https://doi.org/10.1016/j.xcrp.2020.100218.
2. P. Küsgens, M. Rose, I. Senkovska, H. Fröde, A. Henschel, S. Siegle, S. Kaskel, Characterization of metal-organic frameworks by water adsorption, Microporous and Mesoporous Materials 120 (2009) 325–330. https://doi.org/10.1016/j.micromeso.2008.11.020.
3. J.J. Mahle, An adsorption equilibrium model for Type 5 isotherms, Carbon 40 (2002) 2753–2759.
4. M. Hefti, L. Joss, Z. Bjelobrk, M. Mazzotti, On the potential of phase-change adsorbents for CO2 capture by temperature swing adsorption, Faraday Discuss. 192 (2016) 153–179. https://doi.org/10.1039/c6fd00040a.
