Stearic acid-modified MOF-based composite phase change materials for solar-thermal energy conversion and storage

•SA-modified HKUST-1 was prepared via in-situ hydrothermal method for the first time.•The SA loading of HS as support material was 20 wt% higher than that of HKUST-1.•The co-incorporation of TaON and SiW12 synergistically enhanced the light absorption abilities.•The solar-thermal conversion efficiency of the SA/HS/TaON/SiW12 composite PCMs was 96.6%. The utilization, conversion and storage of clean solar energy serving composite phase change materials (PCMs) formed through combination of shape-stable PCMs and light-absorbing materials becomes one of the most efficacious measures to accomplish sustainable development. In this article, the metal–organic framework (MOF) was functionally modified with stearic acid (SA) by in-situ hydrothermal method for the first time and the prepared SA-modified HKUST-1 (HS) was served as the support material for SA. The morphology and crystal structure of HS displayed unobvious change, while significantly increased the surface and formed a relatively strong hydrogen bond with SA. Therefore, the SA adsorption rate of HS reached as high as 60 wt% without any leakage, which was 20 wt% higher than HKUST-1. TaON and SiW12 were collaboratively employed as light-harvesting materials innovatively, and all PCM composites were fabricated through the simple solution immersion means. It is exciting that the SA/HS/TaON/SiW12 composite PCMs not only exhibited good shape-stability, high latent heat (126.4 J/g) as well as heightened thermal conductivity (grown by 295.9% than SA), but also displayed the outstanding thermal reliability and remarkable solar-thermal energy conversion capability (efficiency reached 96.6%). This work expanded a new orientation of photothermal materials used for utilization of solar energy especially in the application of solar water heater systems.