Design of electrically anisotropic renewable carbon nanofiber sheets with tunable electromagnetic behavior from microwave to terahertz

• Carbonization temperature (600–1000 °C) governs porosity, anisotropy, and electric conductivity, enabling tunable electromagnetic response. • Intrinsic impurities induce activation-free hierarchical porosity, achieving a high specific surface area of 926 m 2 g −1 . • A clear structure–property–function is observed, from dielectric behavior to absorber-dominated attenuation and ultimately to reflection-dominated shielding. • Anisotropy enable orientation-dependent shielding response from GHz to THz. Carbon materials are widely investigated for electromagnetic (EM) shielding and absorption. However, designing sustainable and tunable architectures that span multiple EM functions remains challenging. Here, we present a renewable materials strategy based on biopolymer-derived carbon nanofiber sheets where both carbonization temperature and fiber alignment are used to tune EM attenuation. The sheets were fabricated via high-speed electrospinning followed by carbonization at 600–1000 °C, enabling systematic tuning of microstructure, anisotropy, porosity, electrical conductivity and dielectric response. The electrospinning process produced aligned nanofiber networks that upon carbonization developed into anisotropic conductive pathways. Carbonization at 1000 °C yielded highly porous sheets with a specific surface area of 926 m 2 g −1 without external activation. The temperature-driven structural evolution resulted in a distinct functional transition: dielectric transparency at 600 °C, broadband absorption at 700–800 °C, and highly conductive reflective-dominating shielding at 1000 °C. The optimized sheet achieved shielding effectiveness of 54 dB at 18.3 GHz and 44.5 dB at 1.0 THz. Electrical anisotropy further enabled orientation-dependent shielding of 16.4 dB (GHz) and 21.8 dB (THz). These results establish aligned, renewable carbon nanofiber sheets as scalable platforms for next generation microwave and terahertz technologies.