LAUSR

Currently, a versatile route is urgently required to achieve excellent electromagnetic wave (EMW) absorption and shielding functions simultaneously. A lightweight, flexible and sustainable 3D framework aerogel is designed to reach this goal, which is assembled by unique “1D‐1D” combination, nanoscale carbon nanotubes (CNTs) grown on microscale carbon fiber. EM absorption requires appropriate conductivity of filler to acquire moderate permittivity. On the contrary, EM shielding requires great conductivity to reflect most of the incident EMW. Based on this design concept, the change of electric conductivity of as‐obtained samples through in situ regulation of the growth state of CNTs is successfully controlled. When the CNTs are short and curly, the optimized conductivity favors excellent microwave absorption with wide absorption bandwidth of 5.08 GHz at only 1.6 mm. When the CNTs are long and straight, the increased conductivity is clearly boosted with 29.8 dB EM shielding effectiveness. This elaborate architecture and controlled CNT growth allow the designed 3D framework aerogel to be applied in both EM wave absorption and shielding. This conductivity tunable route gives inspiration for fabricating other efficient EM absorption and shielding devices.