ZIF-engineered interpenetrating 3D network for efficient solar-thermal energy storage

Encapsulating phase change materials (PCMs) within photothermal supporting materials holds considerable promise for mitigating the intermittency and instability associated with solar energy. However, the development of efficient supporting materials that can uniformly disperse photothermal scaffold while precisely controlling pore size and distribution remains a significant challenge. Herein, we propose a one-step hydrothermal synthesis strategy to construct an integrated carbon nanotube (CNT) scaffold within a zeolitic imidazolate framework (ZIF) matrix, which is subsequently immersed with n-docosane. The resulting composite forms a unique interpenetrating three-dimensional (3D) network architecture that not only enhances broadband photon absorption but also promotes multi-scale light scattering and reflection, leading to highly efficient photothermal conversion. Furthermore, n-docosane is tightly encapsulated within the ZIF nanosheets via capillary forces, ensuring intimate contact with the CNT scaffold and enabling rapid thermal energy storage. The distinctive hierarchical porous structure also significantly improves the crystallization behavior of n-docosane by reducing its activation energy, thus promoting efficient thermal release. As a result, the n-docosane/CNT@ZIF composite achieves an exceptional photothermal conversion efficiency of 95.53 % under 150 mW/cm2 irradiation, demonstrating superior performance in thermal management and solar-thermal-electric conversion systems. This study promotes interdisciplinary applications and enhances the development of solar energy utilization technologies.