Biomimetic Multi‐Interface Design of Raspberry‐like Absorbent: Gd‐doped FeNi3@Covalent Organic Framework Derivatives for Efficient Electromagnetic Attenuation

Abstract Structural design and interface regulation are useful strategies for achieving strong electromagnetic wave absorption (EMWA) and broad effective absorption bandwidth ( EAB ). Herein, a monomer‐mediated strategy is employed to control the growth of covalent organic framework (COF) wrapping flower‐shaped Gd‐doped FeNi 3 (GFN), and a novel raspberry‐like absorbent based on biomimetic design is fabricated by thermal catalysis. Further, a unique dielectric‐magnetic synergistic system is constructed by utilizing the COF‐derived nitrogen‐doped porous carbon (NPC) as the shell and anisotropic GFN as the core. The electromagnetic parameters of the GFN@NPC composites can be tuned by adjusting the proportions of GFN and NPC. Off‐axis electron holography results further clarify the interface polarization and microscale magnetic interactions affecting the EMW loss mechanism. As a result, the GFN@NPC samples exhibit broad EMWA performance. The EAB values of all GFN@NPC composites reach up to 6.0 GHz, with the GFN@NPC‐2 sample showing a minimum reflection loss ( RL min ) of −69.6 dB at 1.68 mm. In addition, GFN@NPC‐2 achieves a maximum radar cross–section (RCS) reduction of 29.75 dB·m 2 . A multi‐layer gradient structure is also constructed using metamaterial simulation to achieve an ultra‐wide EAB of 12.24 GHz. Overall, this work provides a novel bio‐inspired design strategy to develop high‐performance EMWA materials.