Introduction Hydrated salt phase change energy storage materials enable sustainable storage and release of thermal energy through the phase transition of crystalline water. This low-cost, environmentally friendly material has a high heat storage density. However, the significant heat loss and liquid phase leakage after multiple cycles become persistent challenges, restricting the large-scale application of the original hydrated salt phase change material. Consequently, the preparation of shape-stabilized composite phase change materials by infiltrating hydrated salt phase change materials into porous support structures is one of the investigated methods to address the encapsulation challenges of hydrated salt phase change materials. In this paper, carbon aerogels with a high adsorption capacity were prepared with melamine foam as a precursor. The carbon aerogels were used to encapsulate hydrated salt phase change materials. Methods Carbon aerogel was prepared via multistage temperature carbonization with melamine foam as a precursor. A composite eutectic salt material (EHS) of Na2SO4·10H2O-Na2HPO4·12H2O with 0.2% glucose carbon nanoparticles was added as the phase change matrix. Shape-stabilized melamine carbon aerogel/eutectic salt composite phase change materials were prepared via vacuum melt impregnation.The apparent morphology of the prepared aerogels was determined by scanning electron microscopy (SEM). The composition of the aerogels was analyzed by X-ray diffractometry (XRD), and the interactions between the MF and the eutectic hydrate salts in the composite phase change materials were investigated by the Fourier infrared spectrometry (IR). The thermal conductivities of the samples at room temperature were determined by the Hot Disk thermal constant analysis. Also, the latent heat of the phase change material was analyzed by differential scanning calorimetry (DSC), and the thermal stabilities of the samples were assessed by the simultaneous thermal analysis.Results and discussion Melamine foam before carbonization has large pore and smooth surface. The size of pore decreases with increasing carbonization temperature. Meanwhile, the elemental of carbon aerogels mainly includes C, N and O. The surface functional group disappears as the carbonization temperature rises. The XRD patterns and IR spectra of the carbon aerogel reveal the presence of numerous defects in conjunction with the carbon material, indicating a high degree of graphitization. Moreover, the graphitization degree shows a gradual increase with increasing carbonization temperature. The specific surface areas of carbon aerogels MF, MF6, MF7 and MF8 measured by BET method are 1.4, 107.9, 485.1 m2·g-1 and 313.4 m2·g-1, respectively. The DFT analysis of the pore size distribution shows that carbon aerogel MF has a number of pore sizes larger than 50 nm, and the volume of carbon aerogel MF7 decreases significantly. Also, a large number of micropores and a part of the mesoporous structure appear. The destruction of melamine formaldehyde structure at high temperatures leads to the reduction of the original micropores and the generation of new pores, which is consistent with the SEM results.The loadings of carbon aerogels MF and MF7 reach 116 and 122 times after 5 000 solid-liquid cycles, and the loss of carbon aerogel MF7 is less, indicating its better cycling stability and high potential for application. The initial eutectic salts lose completely at 75 ℃. The eutectic salts after encapsulation by carbon aerogels has a better thermal stability. All of them lose water completely at 145 ℃. The thermal conductivities of composite phase change materials PCM6, PCM7 and PCM8 prepared are 1.11, 1.24 W·m-1·K-1 and 1.37 W·m-1·K-1, respectively. The phase transition latent heat value of PCM is the maximum, but after multiple solid-liquid cycles, its enthalpy of melting is decreased by 15.0% and crystallization enthalpy is decreased by 16.3%, leading to a poor cycling stability. Also, the enthalpy of melting of PCM7 is 278.3 J·g-1 and the enthalpy of crystallization is 227.0 J·g-1, which are only decreased by 4.5% and 2.6% after solid-liquid cycling, resepctively. PCM7 has a superior cycling stability.Conclusions Carbon aerogel of a three-dimensional network structure with high loading, high elasticity and good ductility was prepared via multistage carbonization with melamine foam as a precursor, and carbon aerogel eutectic salt composite phase change materials were prepared.The carbonization of carbon aerogel MF at different temperatures had an effect on the surface elements, functional groups, morphology, and the degree of graphitization of the pore structure. The carbon aerogel prepared at 700 ℃ had an advantage over the encapsulated eutectic salt phase change materials.Carbon aerogel MF had a high loading for EHS, but its leakage prevention, thermal conductivity and cycling stability were poor. Carbon aerogel MF7 had a better pore structure and a needle fiber surface, making it maintain 122 times of its own mass adsorption after 5 000 solid-liquid cycles.The enthalpies of melting and crystallization of PCM7 were 278.3 J·g-1 and 227.0 J·g-1, and the enthalpies were decreased by 4.5% and 2.6%, respectively, after 5 000 solid-liquid cycles. PCM7 had a good cycling stability and a great application potential.