Morphology‐Engineered CaCO 3 Enabling Dual‐Mode Nanocomposites for Zonal Radiative Cooling and Heating

Abstract Passive radiative cooling (PRC) and passive radiative heating (PRH) have emerged as promising strategies for low‐energy temperature control technology. However, conventional materials fall short in addressing the challenges posed by regionalized thermal control. In response, a dual‐mode film capable of delivering both high‐performance PRC and PRH is demonstrated. On the cooling side, a gradient densified structure is constructed by precisely controlling the size distribution of spherical calcium carbonate (CaCO 3 ) and optimizing packing density within the PDMS matrix, resulting in a film with average solar reflectance of 95.2% and infrared emissivity of 96.7%. The heating side features a hierarchically structured PDMS/carbon nanotubes (CNTs) absorber templated from urchin‐like CaCO 3 , further integrates with a polyethylene terephthalate/indium tin oxide (PET/ITO) infrared suppression layer to enhance solar absorption and minimize thermal radiation losses. The heating side achieves an average 30.2% solar reflectance and 2.5% infrared emissivity, demonstrating its excellent radiative heating properties. The dual‐mode film achieves average subambient cooling of 7.6 °C and heating of 3.6 °C under sunny and cloudy conditions. The synergistic enhancement of cooling and heating can be achieved by adjusting the orientation of each mode in building applications, providing a novel approach for a low‐energy, high‐efficiency, and intelligent building thermal control system.