A Coral-Inspired Photoluminescent Phase-Change Material for Passive Radiative Cooling and Waste-Heat Harvesting

Abstract Addressing the escalating heat challenges driven by global warming requires advanced thermal management materials with both high cooling efficiency and energy recovery capability. A biomimetic passive radiative cooling material (BPPM), inspired by the hierarchical porous structure and visible luminescent appearance of corals, is developed to simultaneously harness environmental light and heat. BPPM integrates a porous cellulose acetate (CA) matrix with photoluminescent phase-change microcapsules (PL-PCs), exhibiting a PL-assisted apparent solar reflectance of 100.26% arising from the combined effects of PL-PC photoluminescence and Mie scattering, and an infrared emissivity of 97.71% within the atmospheric window via the molecular vibrations of CA and lattice vibrations of the CaWO4 shell. Under a custom-built outdoor radiative-cooling test configuration, BPPM achieved an average daytime cooling effect of 13.96 ± 1.25 °C relative to the chamber temperature. The BPPM coating also lowered the simulated oil-pillow surface temperature by 17.4 °C and reduced the internal oil temperature. Coupling with a thermoelectric module enables the conversion of low-grade thermal energy into a stable 0.6 V output, while accelerated aging tests show 93% performance retention after 72 h, with substantial performance maintained after 288 h. Building simulations further reveal that annual cooling energy consumption can be reduced by over 20% when BPPM is used as an envelope material. These results in strong potential of BPPM as a zero-energy thermal management material for energy-efficient buildings and cooling applications.