Biomass-based mineralized chitin microsheets for high-efficiency radiative cooling.

The increasing frequency of extreme heat events under global climate change, combined with high energy consumption and CO2 emissions from conventional cooling systems, threatens both ecological sustainability and human health. While traditional passive radiative cooling materials offer a potential solution, they often lead to pollution and have complex designs with high costs. To address these limitations, we developed Mineralized Chitin-based Composite Microsheets (MCCM), a low-cost, eco-friendly radiative cooling material derived from shrimp shells. By leveraging the natural mineralized multiscale Bouligand structure of shrimp shells, we designed a simple chemical treatment to remove proteins, lipids, and pigments while preserving its multiscale structure. Under solar irradiation, MCCM enables sub-ambient radiative cooling, achieving an average temperature reduction of 4.5 °C, attributed to its high solar reflectance (90.0 %) and mid-infrared emissivity (96.0 %). When applied to building exteriors and rooftops, MCCM significantly enhances annual energy-saving performance (>80 GJ) and effectively reduces CO2 emissions. Additionally, it exhibits excellent thermal stability and flame retardancy and can be recycled as agricultural fertilizer, further enhancing its sustainability. This simple processing method for high-value utilization of waste shrimp shells offers a novel approach to developing low-cost functional materials and recycling biomass waste, demonstrating significant potential for building temperature management.