Microstructure Design of Lightweight, Flexible, and High Electromagnetic Shielding Porous Multiwalled Carbon Nanotube/Polymer Composites

Multiwalled carbon nanotube/polymer composites with aligned and isotropic micropores are constructed by a facile ice‐templated freeze‐drying method in a wide density range, with controllable types and contents of the nanoscale building blocks, in order to tune the shielding performance together with the considerable mechanical and electrical properties. Under the mutual promotion of the frame and porous structure, the lightweight high‐performance shielding is achieved: a 2.3 mm thick sample can reach 46.7 and 21.7 dB in the microwave X‐band while the density is merely 32.3 and 9.0 mg cm −3 , respectively. The lowest density corresponds to a value of shielding effectiveness divided by both the density and thickness up to 10 4 dB cm 2 g −1 , far beyond the conductive polymer composites with other fillers ever reported. The shielding mechanism of the flexible porous materials is further demonstrated by an in situ compression experiment.