Synergistic molecular assembly and impedance matching in polyimide-derived porous carbon nanosheets for advanced microwave absorption

Herein, a novel strategy for fabricating microwave absorption materials via molecular-level design that synergistically regulates dielectric and magnetic losses. The method utilizes a polyimide precursor containing both carboxyl and benzimidazole functional groups as the key component. Through an ice-templating process followed by in-situ ion exchange, Ni 2+ ions are uniformly incorporated into the polymeric skeleton. Subsequent thermal imidization and carbonization yield nitrogen-doped two-dimensional carbon nanosheets embedded with uniformly dispersed Ni/NiO nanoparticles (BPCN@Ni/NiO). This material exhibits significantly superior microwave absorption properties compared to its counterpart synthesized without the benzimidazole structure (NPCN@Ni/NiO). BPCN@Ni/NiO achieves a remarkable minimum reflection loss ( RL min ) of −69.02 dB with effective absorption bandwidth ( EAB ) of 8.92 GHz (8.28–17.2 GHz). Microstructural analyses confirm its three-dimensional interconnected nanosheet architecture, highly dispersed Ni/NiO species, and homogeneous elemental distribution. The performance enhancement is attributed to the synergistic complexation of Ni 2+ ions by benzimidazole and carboxyl groups, which enables efficient loading and uniform dispersion of nickel species, thereby optimizing impedance matching. Furthermore, the unique 2D conductive network, abundant heterogeneous interfaces (C/Ni/NiO), defect-induced dipole polarization, and magnetic coupling between Ni and NiO collectively contribute to synergistic multiple loss mechanisms, ultimately endowing the material with excellent microwave attenuation capability. This work offers a new pathway for designing lightweight, efficient, and broadband carbon-based composite absorbers through precise molecular engineering.