A Sustainable Ultrawide‐Spectrum‐Selective Paper‐Based Heating Window Against Microwave Radiation

Abstract Energy scarcity and electromagnetic microwave (EMW) management pose global challenges, yet integrating functionalities in a single material to manage ultrawide‐spectrum radiative energy from visible to microwave remains formidable. Here, sustainable yet appropriate cellulose and cellulose nanofibers (CNFs) are utilized to integrate silver nanowires and transition metal carbides, consequently yielding the large‐area, ultrathin, high‐strength, ultra‐flexible, and durable paper‐based window films toward advanced ultrawide‐spectrum heating and EMW attenuation. The ultrawide‐spectrum‐selective films demonstrate high visible light transmittance, near‐infrared photothermal conversion, mid‐infrared low emissivity‐induced passive radiative heating, and effective EMW attenuation, simultaneously elevating energy conversion efficiency and EMW management. Under a solar power density of 50 mW cm − 2 , a CAMC‐equipped room with dimensions of 30 × 20 × 18 cm 3 exhibits a temperature increase of 9.4 °C, outperforming other heating materials of identical dimensions and initial temperatures. Furthermore, they offer an adjustable range of optical transmittance and EMW shielding effectiveness (SE), with a thickness‐normalized specific SE ranging from 937 to 2562 dB mm −1 and transmittance between 80.3% and 55.1%, surpassing the reported materials.