Hollow CoFe‐MOF@Bamboo Derived Lightweight Carbon Composites for High‐Efficiency Electromagnetic Interference Shielding and Thermal Management

The urgent demand for sustainable, high‐performance electromagnetic interference (EMI) shielding materials accelerates the development of biomass‐derived alternatives. However, achieving simultaneous high shielding effectiveness (SE), low reflection, and lightweight characteristics remains a critical challenge. Herein, an ultrathin, lightweight hollow magnetic CoFe carbon nanocages embedded within bamboo‐derived carbonized composites (HCoFe@CN/BC) is reported, engineered via the in situ growth of CoFe Prussian blue analogs on a cellulose scaffold, followed by acid etching, compression, and carbonization. The well‐established electric–magnetic coupling network within the composites enables multiple energy dissipation mechanisms and substantially enhances electromagnetic (EM) wave absorption capability. In particular, the unique hollow structure promotes multiple internal reflections of EM waves while simultaneously reducing material density. Consequently, the optimized composites (0.14 mm thickness, 0.278 g cm −3 density) achieve an outstanding EMI SE of 50.1 dB, an ultralow average reflection SE of 6.57 dB, and a specific EMI SE of 12872.6 dB cm 2 g −1 , outperforming most reported bio‐based EMI shielding materials. Additionally, the composites exhibit remarkable Joule heating performance, reach a high surface temperature of 118 °C at a low voltage of 2 V. Given these properties, practical demonstrations underscore the potential of HCoFe@CN/BC composites for advanced EMI shielding and thermal management in decorative building materials and smart home systems.