Multifunctional Hierarchical Coatings with Synergistic Anti-graffiti and Ultra-hardness Properties for NIR Shielding Energy-saving Windows

The efficient regulation of sunlight to minimize unnecessary energy exchange through windows plays a vital role in advancing building energy efficiency. However, the inferior stability of cerium-doped tungsten trioxide (CWO) as a near-infrared (NIR) shielding material, combined with the poor mechanical properties of its coatings, poses significant challenges for long-term thermal insulation performance. Here, a hierarchical thermal insulation coating with multifunctional integration has been developed. The inner layer’s excellent NIR shielding performance (94.4%) results in a temperature reduction of 13.6 °C, demonstrating outstanding thermal insulation. Meanwhile, the external layer composed of polysilsesquioxane grafted by carboxylated hexafluoropropylene trimer offers exceptional weather resistance due to the low surface energy. The fluorosilicone coating effectively mitigates oxidation of CWO, as evidenced by the retention of NIR shielding performance even after 30 days of exposure to 60 °C and 90% relative humidity. Furthermore, the coating demonstrates superior anti-graffiti properties and achieves an ultra-high mechanical strength of 0.49 GPa through precise fluorine content modulation. This hierarchical design integrates high hardness, excellent abrasion resistance, anti-graffiti functionality, transparency, and long-term operational durability into a single smart window system, offering a promising solution for reducing building energy consumption.