Nanofibrous aerogels with continuous conductivity gradient for ultrabroadband absorption-dominant electromagnetic interference shielding.

Electromagnetic interference (EMI) shields are limited by a severe impedance mismatch with free space, leading to strong reflections and secondary radiation. Here, we introduce ultralight all-polymer aerogels featuring a continuous through-thickness conductivity gradient (MCAs), fabricated in a single step via diffusion-driven oxidative polymerization of pyrrole within aramid nanofiber scaffolds. An exponentially decaying conductivity profile enables ultrabroadband, low-reflection performance in 5-mm-thick samples, achieving reflection power coefficient R < 0.1 across 10.2-40.0 GHz, while maintaining shielding effectiveness > 30 dB under low-conductivity face incidence. Waveguide measurements and simulations show that progressive impedance transition and internal field redistribution drive absorption-dominated ohmic loss rather than surface reflection. A gradient-stratified electromagnetic model delineates an optimal design window for key gradient parameter. Beyond EMI protection, this nanofibrous architecture provides mechanical robustness and facile processability, establishing a diffusion-reaction strategy for spatially programmed conductive networks relevant to electromagnetic, electronic, and energy systems.