NIR-induced self-healing and recyclable polyurethane composites based on thermally reversible cross-linking for efficient solar-to-thermal energy storage

Conventional chemically cross-linked phase change materials (PCMs) possess many merits, such as reliable structural stability, high mechanical strength , and excellent form stability, but they unable to be self-healed, recycled and reprocessed because of permanently covalent cross-linking structure. Furthermore, the poor solar-to-thermal performance of organic PCMs severely restricts their practical usage for solar energy utilization. Herein, novel dynamically covalent cross-linked PEG-based polyurethane (FMPCMs) with superior solar-to-thermal conversion performance, satisfactory self-healing ability and admirable recyclability were synthesized by introducing furan-decorated Ti 3 C 2 T x MXene nanosheets (f-MXene) into polyethylene glycol-based polyurethane (PEG-PU). f-MXene, which is dynamically and covalently linked in polymeric FMPCMs, served not only as an efficient photon capturer in PEG-PU for converting solar to thermal energy but also as a dynamic cross-linked point for thermal-induced recycling and self-healing. Due to the reversible Diels-Alder (DA) covalent bond , f-MXene nanosheets endows the FMPCMs with significantly increased near-infrared-induced (NIR-induced) self-healing efficiency (90.6%) and satisfactory recyclability. Furthermore, the solar-to-thermal conversion and storage efficiency of FMPCMs were effectively increased with the incorporation of f-MXene. In conclusion, FMPCMs show tremendous potential in solar-to-thermal energy storage.