Incorporating CaCl2·6H2O into expanded graphite@UIO-66 hybrid matrix to develop phase change temperature-humidity control material

Indoor temperature and humidity are crucial to human health and productivity, which drives the search for energy-efficient and sustainable materials to regulate them. Traditional phase change materials (PCMs) have been demonstrated the significant potential in temperature regulation, but they possess the drawbacks including low thermal conductivity, leakage during phase transitions and the inability to control indoor humidity. These shortcomings significantly hinder the effectiveness of PCMs in real-world applications. Therefore, this study aimed to address these issues by developing a phase change temperature and humidity control material (PCHCM) which composed CaCl₂·6H₂O PCM modified with SrCl₂·6H₂O (nucleating agent) as the temperature control material, expanded graphite (EG) as a carrier for PCM and UIO-66 as a humidity control component. The PCHCM was obtained by combining EG@UIO-66 hybrid matrix with CaCl₂·6H₂O PCM, for which the hybrid matrix was firstly synthesized by depositing UIO-66 on the surfaces on the EG via in-situ method. The shape stability, thermal performances and moisture adsorption capacity of the obtained PCHCM were studied. The research results indicated that the phase change temperature of PCHCM was 25.6 °C, with a phase change enthalpy of 117.1 J/g, thermal conductivity of 7.912 W/m·K, and effective leakage prevention. Simultaneously, the PCHCM exhibited a high adsorption capacity of 1.024 g/g at 60 % relative humidity. After 50 thermal cycles, the phase change enthalpy decreased by only 1.54 %, demonstrating excellent cycling stability. Therefore, the newly developed PCHCM in this work has broad application prospects in temperature and humidity control as well as in building energy conservation. • A PCHCM was synthesized using CaCl₂·6H₂O as PCM and EG@UIO-66 as the hybrid matrix. • Adding EG@UIO-66 resolved PCM leakage and increased the thermal conductivity of PCHCM. • The PCHCM had high phase change enthalpy and good thermal stability. • PCHCM exhibited excellent hygroscopicity and had great potential in the buildings.