The desorption processes of organic working fluids in metal organic frameworks and covalent organic frameworks: A molecular dynamics study

QB Li and K Wu, INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER, 167, 109294 (2025).

DOI: 10.1016/j.icheatmasstransfer.2025.109294

The heat storage capacity of working fluids can be enhanced by the conversion of thermal energy and surface energy during their adsorption and desorption processes in porous materials. However, existing studies have predominantly focused on adsorption processes, while desorption processes remain underexplored. This study employed molecular dynamics simulations to investigate the desorption properties of R32, R134a, and R1234yf in two groups of MOFs (IRMOF-1, IRMOF-16) and COFs (BF-COF-2, COF-108) with varying volume specific surface areas. The results show that the desorption capacity, desorption heat, and self-diffusion coefficient increase with temperature. For similar specific surface areas, the desorption performance of COFs is better than that of MOFs. In addition, the desorption free energy of COFs is relatively higher. Porous materials with smaller specific surface areas show greater advantages in desorption due to fewer adsorption sites. Adding 1 wt% of IRMOF-1, IRMOF-16, BF-COF-2, and COF-108 to R134a at 410 K enhanced thermal energy storage properties by 1.34 %, 5.49 %, 2.36 %, and 5.99 %, respectively. Due to the larger desorption heat of COFs, the thermal energy storage capacity of working fluids with COFs performs better than that of working fluids with MOFs at similar specific surface areas.

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