Hierarchical Ceramic Nanofibrous Aerogels for Universal Passive Radiative Cooling

Abstract Solar‐induced thermal challenges in buildings, cold chain logistics, and spacecrafts may be overcome by integrating passive radiative cooling (PRC) with aerogels having thermal insulation (TI). Herein, a universal radiative cooling silica aerogel (UCSA) is prepared through the simple regeneration and freeze‐drying of commercial quartz fiber membranes. The optically engineered UCSA with a hybrid structure (silica nanofibers/microbeads) achieves remarkable solar reflectance (R_S.E. = 98.1%) and atmospheric transparency window emittance (ε_ATW = 92.1%) under Earth conditions, with a theoretical daytime cooling power of 103.3 W m⁻². In the harsh space environment, it exhibits ultrahigh average solar reflectance (R_S.E. = 99.1%) and broadband mid‐infrared emittance (ε_MIR = 90%), achieving a cooling power of 354.1 W m⁻². Compared to single‐functional approaches, UCSA synergistically integrates the PRC and TI performance for excellent thermal management capability. Moreover, this ceramic aerogel can resist temperatures up to 830 °C, safeguarding building occupants and spacecraft electronics. Furthermore, UCSA passes environmental aging and thermal vacuum outgassing tests for long‐term viability both on Earth and in space. Finally, a USCA‐covered box achieves an average sub‐ambient cooling of 18.6 °C when exposed to sunlight. In summary, UCSA opens a path for energy‐efficient and sustainable cooling strategy with universal applications.