DLP 3D printed hydrophobic polymer for passive daytime radiative cooling

Rapid urbanization has exacerbated the urban heat island (UHI) effect and increased building cooling energy demand, posing significant challenges to public health and energy sustainability. Herein, we developed a 3D-printed spectrally engineered polymer (PPHP) for building radiative cooling via UV-initiated thiol–ene click chemistry combined with chemical vapor deposition (CVD), achieving high solar reflectance, strong emissivity within the atmospheric window, and stable performance under humid conditions. PPHP consists of a crosslinked organic network formed by PETMP and PETA/HDDA, with PVDF-HFP incorporated to generate a porous fluorinated structure. The multiscale scattering interfaces provided a high solar spectral reflectance of 94.24%, effectively suppressing solar absorption. Meanwhile, the strong vibrational characteristics of the–CF 2 – and C–F bonds in the 8–13 μm range enable a near-blackbody emissivity of 99.16%, facilitating efficient thermal radiation to outer space. MTMS chemical vapor deposition further constructs a hydrophobic interface (contact angle of 136°), ensuring spectral stability across a humidity range of 11–98% relative humidity (RH). As a result, PPHP 15 -C/T 5 exhibited a theoretically simulated subambient cooling potential of 6–10 °C under a solar irradiance of 900 W m −2 and achieved an average subambient cooling of 6.88 °C in the rooftop model-house test. EnergyPlus simulations further indicated that PPHP 15 -C/T 5 could reduce the annual cooling load in cooling-dominated regions when applied to roofs and opaque exterior walls. This study provides a scalable and manufacturable strategy for passive radiative cooling of building envelopes under complex climatic conditions.