Molecular Dynamics Study of Adsorption, Desorption, and Thermal Energy Storage Performance of Zeotropic Mixtures in IRMOF-1.

Metal-organic heat carrier nanofluids (MOHCs) can enhance the thermal storage capacity of working fluids by utilizing the endothermic desorption of working fluids in metal-organic frameworks (MOFs). However, investigations into the adsorption and desorption of zeotropic mixtures in MOFs and the thermal storage enhancement effect of MOFs on these mixtures remain limited. In this work, molecular dynamics simulations are employed to investigate the adsorption and desorption processes of zeotropic mixtures R32/R1234yf and R32/R1234ze(E) in IRMOF-1. The results indicate that IRMOF-1 exhibits a higher adsorption capacity for R1234yf and R1234ze(E) than that for R32. Competitive adsorption is observed in the zeotropic mixture systems, with the adsorption selectivity of R32 remaining below 1, indicating a preferential adsorption of R1234yf and R1234ze(E) by IRMOF-1. During the desorption process, R32 demonstrates a stronger tendency to desorb from the MOF compared with the other components. Moreover, R1234ze(E) shows a stronger interaction energy with the IRMOF-1 than R1234yf. Under conditions of low temperature difference and high pressure, the thermal storage enhancement of mixture MOHCs becomes more significant, whereas increasing the mass fraction of R32 leads to a deterioration in thermal storage performance. These findings clarify the adsorption and desorption mechanisms of zeotropic mixtures in IRMOF-1 and provide molecular-level guidance for designing MOHC systems for thermal energy storage.