A Formable Wood‐Based Phase Change Materials with Enhanced Mechanical Properties and Thermal Efficiency for Smart Building

Abstract Solid–liquid phase change materials (PCMs) are capable of absorbing and releasing heat through a reversible phase change process, playing a significant role in thermal protection and energy conservation in smart buildings. However, challenges such as liquid leakage and subsequent declines in mechanical properties persist. Here, a wood‐form‐stable phase change composite (DWTP) is reported, created by regulating the self‐assembly of multi‐active site polyethylene glycol and in situ mineralization. The DWTP features a multi‐scale network formed by gradient hydrogen bonding between cellulose molecules and Si─O─Si/PEG, demonstrating a high enthalpy of 94.73 J g −1 and outstanding mechanical tensile strength of 134.42 MPa—the highest reported for any PCM to date. Additionally, this DWTP can support loads exceeding 110 times its weight without deformation and leakage when heated above its phase transition temperature. Following 50 thermal‐cold cycles, the DWTP retains 97.3% of its phase change performance. Outdoor thermal management tests verify that the DWTP cabin achieves a maximum sub‐ambient temperature reduction of 14.1 °C in conditions with an ambient temperature of 50 °C. This biomass DWTP represents a significant advancement in the design of next‐generation sustainable thermal management materials.