Polydopamine-coated metal-organic framework-based composite phase change materials for photothermal conversion and storage

The liquid leakage and weak solar absorption capacity of organic phase change materials (PCMs) seriously hinder the efficient utilization of solar energy and thermal energy storage. To address these issues, we prepared nanoporous metal organic framework (Ni-MOF) for the vacuum infiltration of paraffin wax (PW), followed by the coating of solar-absorbing functional polydopamine (PDA) on the surface of PW@MOF for photothermal conversion and storage. As an efficient photon harvester, PDA coating endows PW@MOF/PDA composite PCMs with excellent photothermal conversion and storage properties due to the robust broadband solar absorption capability in the UV–vis region. Resultantly, our prepared PW@MOF/PDA composite PCMs exhibit a high photothermal conversion and storage efficiency of 91.2%, while that of PW@MOF composite PCMs is only zero. In addition, PW@MOF/PDA composite PCMs also exhibit excellent thermal stability, shape stability, energy storage stability, and photothermal conversion stability. More importantly, this coating strategy is universal by integrating different MOFs and solar absorbers, showing the potential to accelerate the major breakthroughs of high-efficiency MOF-based photothermal composite PCMs in solar energy utilization.