A structural bioplastic metafilm for durable passive radiative cooling

Bio-derived radiative coolers offer a sustainable alternative to petrochemical materials but struggle with long-term stability. Here, we report a bioplastic cooling metafilm with a bi-continuous architecture engineered through crystallization modulation. The metafilm achieves high solar reflectance (98.7%), exceptional thermal emittance (96.6%), and ultra-low thermal conductivity (0.049 W m −1 K −1 ). It provides a maximum sub-ambient cooling of ∼9.2°C at midday, with an average cooling power of 136 W m −2 under peak solar intensity (944.9 W m −2 ). Notably, it sustains a stable cooling of 5°C–6.5°C even when subjected to severe conditions like prolonged acid (pH 1, 120 h) and ultraviolet (UV; ∼8 months) exposure. This work offers a new strategy for designing sustainable, durable, and energy-efficient cooling materials through structural innovation.