▎ 摘　　要

The development of high-performance microwave absorption materials with strong absorption capacity and broad bandwidth is highly desirable in the field of electromagnetic pollution protection. Herein, ultralight polyimide-based graphene foam with ordered lamellar structure is precisely designed and controllably constructed by bidirectional freezing process. More lamellar interfaces formed inside the foam per unit volume effectively facilitate the layer-by-layer dissipation for the vertical incident electromagnetic waves, thereby endowing the foam with efficient broadband electromagnetic absorption performance. More importantly, electromagnetic absorption performance can be controllably adjusted by optimizing impedance distribution and microstructure of skeletons. As a result, the optimized foam with an ultralow density of 9.10 mg/cm(3) presents a minimum reflection loss value of -61.29 dB at 9.25 GHz and an effective absorption bandwidth of 5.51 GHz (7.06-12.57 GHz, covering the whole X band) when the thickness is 4.75 mm. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.