Flexible ZnS Nanosphere/Porous PDMS Films with Vivid Color and Self-Cleaning for Effective Passive Daytime Radiative Cooling

The growing frequency of extreme summer heat events has intensified interest in passive daytime radiative cooling (PDRC) as a zero-energy thermal management strategy. However, most PDRC materials are limited to white or light colors, restricting their aesthetic integration and application versatility. Here, we report colored and superhydrophobic PDRC films based on a hierarchically porous-particle binary architecture. Uniform zinc sulfide (ZnS) nanospheres are spray-coated as noniridescent structural colorants onto porous polydimethylsiloxane (P-PDMS) substrates with submicrometer to micrometer-sized pores. Benefiting from this structural design, the films exhibit a solar reflectance of 73.8% over 0.3 to 2.5 μm and a high longwave infrared emissivity of 92.4% within the atmospheric window. Under outdoor conditions, the ZnS/P-PDMS films achieve a stable temperature reduction of approximately 1–6 °C below ambient temperature. In addition, the films feature superhydrophobic surfaces with self-cleaning capability. Notably, the temperature response and wettability can be largely retained after representative environmental challenges, including alkaline immersion at pH 14, heating at 90 °C, ultraviolet exposure at 365 nm, and water scouring. The simple fabrication process and environmentally benign materials highlight the potential of this approach for large-scale production and practical PDRC applications.