Thermochromic Janus Membranes with Dynamic Solar Modulation Toward Sustainable and High-Efficiency Solar-to-Thermal Intelligent Management

Solar-energy thermal management, characterized by its environmental friendliness, cost-effectiveness, and efficiency, holds a promising future, which has brought about widespread interest in the evolution of solar-to-thermal materials with the desired properties. Nevertheless, in both hot and cold environments, challenges in developing functionally integrated hydrogels for sustainable thermal regulation still remain. In this study, a rationally, simply, and effectively designed structured Janus membrane, consisting of a Ti3C2Tx MXene/GO/alginate fibers nonwoven (GMF) layer and a P (NIPAM co-DMAA) (PAD) hydrogel layer. The GMF with excellent hydrophilicity forms an interpenetrating structure with the PAD hydrogel through strong hydrogen bonds and can be easily adapted to multishape and multifield applications. By adjusting the content of thermochromic PAD hydrogel monomers, an improvement in the critical transition temperature (37.7 degrees C) and a reduction in volume shrinkage has been achieved, and the full-spectrum intrinsic transmittance is 67.59%, which is of excellent practicability and cyclic stability. Under constant sunlight, the hydrogel's phase transition decelerates the temperature increment in the photothermal layer, thereby establishing a stable equilibrium temperature in the environment. The equilibrium temperature of the photothermal layer can be adjusted between 32 and 36 degrees C to match a variety of climates by regulating the relative content of the Ti3C2Tx MXene and GO in the photothermal layer. Additionally, the existence of the thermochromic hydrogel in the Janus membrane prevents the indoor temperature from overheating. Furthermore, the membrane's asymmetric structure enhances its ability to reduce heat dissipation, crucial for high-performance thermal management. Moreover, this novel structure can be used as a self-supporting agricultural film to maintain a stable temperature in the environment for efficient plant growth, demonstrating significant potential in new modern agriculture.