A novel enhancement of shape/thermal stability and energy-storage capacity of phase change materials through the formation of composites with 3D porous (3,6)-connected metal-organic framework

Abstract

Leakage at temperatures above the melting point and thermal-transport performance are prime factors for the effective application of phase change materials (PCMs). In this study, a shape-stabilized composite PCM based on a three-dimensional (3D) porous (3,6)-connected metal-organic framework (MOF) and polyethylene glycol (PEG) was designed. The (3,6)-connected Zn2+ MOF gel was used as a porous supporting material, whereas PEG was employed as an energy-storage material. The PCM, which was impregnated by a capillary force and anchored by a weak hydrogen-bonding interaction between hydroxyl and amine groups, was stabilized by the supporting material. The 3D and two-fold interpenetrated structure of the MOF provided continuous heat-transfer paths in the composite PCM. The resulting composite material exhibited a high transition enthalpy (159.8 kJ/kg) with an encapsulation efficiency and impregnation ratio of 93.4% and 92.2%, respectively. The large interior surface accessibility of the MOF played a vital role in enhancing the thermal properties of the as-synthesized composite PCM. Additionally, the composite PCM exhibited excellent thermal stability and reliability even after 100 thermal cycles. Therefore, the composite PCM is a promising candidate for thermal-energy management systems owing to its high latent heat, suitable phase-change temperature, good chemical compatibility, reduced extent of supercooling, and high thermal stability.