Passive radiative cooling (PRC) is the most promising technique to address future cooling requirements as it cools a surface without any energy input by reflecting sunlight and radiating heat, which will have a great impact on the global energy landscape. Here, we report a significant advance toward the design and fabrication of a novel hybrid material for outdoor PRC based on three-dimensionally porous cellulose acetate (3DPCA) film with rationally designed pore sizes centered at ~5 µm and auto-deposited resonant polar dielectric SiO₂ microspheres. The side of 3DPCA/SiO₂ film with enriched SiO₂ shows both ultrahigh average solar reflectance ${\bar{R}}_{\mathit{solar}}$ of ~96% and enhanced average infrared emittance ${\bar{\epsilon }}_{\mathit{IR}}$ of ~95%, reaching up to the state-of-the-art levels. Especially the ${\bar{\epsilon }}_{\mathit{IR}}$ value is greater than that of the reported solid polymer film with randomly distributed SiO₂ microspheres (93%). The excellent PRC capability is further demonstrated by outdoor tests where practically attainable cooling temperatures are ~8.6 °C for nighttime and ~6.2 °C for daytime. The performance equals or surpasses that of state-of-the-art PRC designs, while the developed technique offers paint-like simplicity for low-cost and large-scale production. Owing to its superior PRC capability and scalability, this composite film is of great potential for promoting radiative cooling as a viable energy technology.

被动辐射冷却（PRC）是解决未来冷却需求的最有前途的技术，因为它通过反射阳光和辐射热量来冷却没有任何能量输入的表面，这将对全球能源格局产生重大影响。在这里，我们报告了基于三维多孔醋酸纤维素（3DPCA）膜的新型室外PRC杂化材料的设计和制造方面的重大进展，该膜具有合理设计的孔径在〜5 µm中心并且具有自动沉积的共振极性电介质SiO _2个微球。3DPCA / SiO ₂薄膜中富含SiO ₂的一面显示出超高的平均日光反射率${\overline{\mathrm{[R}}}_{\mathit{太阳能的}}$ 〜96％的平均红外发射率 ${\bar{\epsilon }}_{\mathit{红外}}$约为95％，达到了最先进的水平。特别是${\bar{\epsilon }}_{\mathit{红外}}$值大于已报道的具有随机分布的SiO ₂微球的固体聚合物薄膜的数值（93％）。室外测试进一步证明了出色的PRC能力，在室外测试中，夜间可达到的实际冷却温度为约8.6°C，白天为约6.2°C。性能等于或超过最新的PRC设计，而发达的技术为低成本和大规模生产提供了类似油漆的简便性。由于其优越的PRC能力和可扩展性，这种复合膜在促进辐射冷却作为一种可行的能源技术方面具有巨大的潜力。