The exploitation of from-stable phase change materials (PCMs) with superior energy storage capacity and excellent solar−thermal conversion performance is crucial for the efficient exploitation of solar energy. Herein, 2D-layered polymerized dopamine-decorated Ti 3 C 2 T x MXene nanosheets (P-MXene) with superior photothermal effects and excellent oxidation stability were synthesized from Ti 3 AlC 2 particles by the selective etching and self-polymerization of dopamine. Then, novel biomass-derived PCM composites, eMPCMs, were fabricated by impregnating erythritol into P-MXene/cellulose nanofiber (CNF) hybrid aerogels. The porous and interconnected 3D aerogels adequately support erythritol and resist liquid leakage during thermal storage. Differential scanning calorimetry (DSC) results showed that the eMPCMs based on P-MXene/CNF aerogels exhibited an extremely high thermal storage density (325.4−330.6 J/g) and excellent PCM loading capacity (up to 1929%). The introduction of P-MXene nanosheets into eMPCMs significantly increased the solar−thermal conversion and storage efficiency, solar−thermal−electricity conversion capacity, and thermal conductivity of the synthesized PCM composites. Moreover, the P-MXene/CNF hybrid aerogelbased PCM composites possessed excellent long-term thermal reliability and thermostability. Hence, the synthesized eMPCMs reveal tremendous potential for efficient solar−thermal storage fields.

Conventional polymeric phase change materials (PCMs) exhibit good shape stability, large energy storage density, and satisfactory chemical stability, but they cannot be recycled and self-healed due to their permanent cross-linking structure. Additionally, the high flammability of organic PCMs seriously restricts their applications for thermal energy storage (TES). Therefore, it is urgently required to explore PCM composites exhibiting superior recyclability, good self-healing capability, and excellent flame retardancy simultaneously. Herein, tri-maleimide end-capped cyclotriphosphazene flame retardant (TMCTP) was synthesized via the nucleophilic substitution between 1,3,5,2,4,6-triazatriphosphorine-2,2,4,4,6,6-hexachloride and N-(2-hydroxyethyl)­maleimide. Then, novel dynamically cross-linked PCM composites (FPCMs) with superior recyclability, good self-healing capability, and excellent flame retardancy were fabricated by bonding PEG and TMCTP to polymeric skeleton via reversible furan/maleimide Diels–Alder (DA) reaction. TMCTP, which covalently and dynamically binding in the polymeric FPCMs, acted not only as an efficient flame retardant for reducing the flammability of PCM composites but also as dynamic cross-linking skeletons for thermally induced self-healing and recycling. Differential scanning calorimetry (DSC) analysis confirmed the reversible energy storage and release ability of FPCMs. Due to its reversible DA covalent bonds, the introduction of TMCTP endowed the FPCMs with considerably increased self-healing efficiency (up to 93.1%) and recyclability efficiency (94.6%). Moreover, with the introduction of TMCTP into FPCMs, the heat release rate (HRR) and total heat release (THR) significantly decreased, while the char residue and limiting oxygen index (LOI) value increased, confirming that the flame retardancy of FPCMs greatly improved. Hence, the synthesized FPCMs show enormous potential in TES applications.

A synergistic reactive flame‐retardant polyol (AFeDH) containing ferrocene, phosphorus, and nitrogen elements was synthesized from ferro‐formaldehyde, 5‐amino‐1,3, 4‐thiadiazole‐2‐mercaptan, 9,10‐dihydro‐9‐oxa‐10‐phos‐phaphenanthrene‐10‐oxide and hydroxyl terminated polybutadiene acrylonitrile, and then applied for flame retarding waterborne polyurethane (WPU). The chemical structures of intermediates and final products were well characterized to confirm the successful preparation of ternary P‐N‐Fe flame retardant. The effects of incorporated AFeDH on thermal stability, flame retardancy and mechanical properties of AFeDH/WPU films were systematically studied. The results indicated that LOI value increased with the increase amount of AFeDH, while the value then decreased as the loading content above 6 wt%. This increase in flame retardancy results from the competition between the catalytic degradation of iron and the catalytic carbonization. Benefiting from the good synergistic effects among each element of AFeDH, the WPU/AFeDH films perform the decreased heat release and smoke production. Moreover, the flame retardant films also show the enhanced tensile strength of 33.8 MPa and elongation at break of 763.3%. Therefore, this novel halogen‐free flame retardant shows an excellent synergistic effect among P, N, and Fe elements, which has a great potential in the application of flame retardant WPU.

Impregnating organic phase-change materials (PCMs) into biomass-derived aerogels is regarded as one of the most effective and accessible approach to address the liquid leakage issues of solid–liquid PCMs. However, the inefficient solar–thermal conversion and low thermal conductivity still restrict the large-scaled applications of organic PCMs in solar utilization fields. Herein, novel form-stable PCM composites (CMPCM-Fe) with enhanced thermal conductivity and excellent solar- and magnetic-driven thermal energy conversion and storage efficiency were fabricated by impregnating n-docosane into Fe3O4-functionalized κ-carrageenan/melanin hybrid aerogels (CMA-Fe) through vacuum impregnation. CMA-Fe effectively supported n-docosane and prevented the leakage issue during the phase transition process owing to its strong surface tension and capillary force. CMPCM-Fe exhibited high encapsulated efficiency (88.9–94.6%), satisfactory thermal storage capacity (229.1–246.9 J/g), and excellent reversible stability. The introduction of Fe3O4 nanoparticles enhanced the thermal conductivity (55.3% increased) and solar–thermal conversion efficiency (up to 93.5%) of CMPCM-Fe and endowed it with excellent magnetic–thermal conversion capacity under an alternating magnetic field. The synthesized CMPCM-Fe possesses broad application prospect in mutiresponse thermal management.

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