Effect of amino functional groups on the thermal properties of stearic acid/UiO-66 composite phase change materials:Experimental and molecular dynamics simulations

Modification of metal-organic frameworks (MOFs) with different functional groups can effectively improve the loading ratio of phase change materials (PCMs) as well as the thermal properties of composite phase change material (CPCM). However, the interaction mechanism between functional groups and PCMs is still unclear. Herein, molecular dynamics (MD) simulations and experimental tools were used to study the interaction mechanism between integrating amino-functionalized and unfunctionalized UiO-66-NH 2 , UiO-66 (UiO-66: Zirconium-centred MOF) and stearic acid (SA). The incorporation of amino groups enhanced the phonon vibrational coupling between UiO-66-NH 2 and SA, as well as the number of hydrogen bonds. Thermal resistance between PCM and the carrier was effectively reduced, exhibiting a 42.46% decrease compared to UiO-66, because the amino functional group can increase the number of hydrogen bonds between UiO-66 and SA, thereby increasing the overall thermal conductivity. From the experimental results in this paper, the amino-modified UiO-66-NH 2 can load more SA, and therefore the enthalpy is also well enhanced, with a maximum melting enthalpy of 71.3 J/g, and no leakage during the phase transition. The findings of the experimental study are in alignment with the results of the molecular dynamics simulations. In addition, the results of the thermal management experiment demonstrate that the CPCMs consisting of UiO-66-NH 2 and SA can effectively regulate the heating rate of the heating element. In conclusion, the present study offers novel experimental and MD simulation insights that may inform the future design of MOF-based CPCMs modified with diverse surface functional groups.