Ethanol-mediated synthesis of defective Zn-benzimidazole polymer derived N-doped carbon materials and microwave absorption properties

With the rapid proliferation of electronic devices and microwave communication technologies, severe electromagnetic interference (EMI) and electromagnetic radiation pollution have become pressing issues, urgently requiring the development of high-efficiency microwave absorbers with broad bandwidth and strong attenuation capability. Metal-organic frameworks (MOFs)-derived carbon materials have emerged as promising candidates for advanced microwave absorption by virtue of their tunable morphology, large specific surface area, and controllable heteroatom doping. Herein, hierarchical N-doped porous carbon microwave absorbers were successfully fabricated via a facile ethanol-mediated solvothermal route combined with high-temperature pyrolysis, using a Zn-benzimidazole (Zn-BIM) coordination polymer as the precursor, while concentrated NH₃·H₂O served simultaneously as the alkaline regulator and N source. The microstructure, carbon defect density, and microwave absorption performance were systematically optimized by modulating the Zn/BIM molar ratio and NH₃·H₂O dosage. The optimized sample delivered exceptional microwave absorption performance at a Zn/BIM molar ratio of 1:2 and NH₃·H₂O dosage of 9 mL, achieving a minimum reflection loss (RL_min) of −57.33 dB at 2.41 mm and a broad effective absorption bandwidth (EAB) up to 8.72 GHz, well satisfying the requirements of practical electromagnetic protection applications. The superior absorption performance originates from the synergistic contribution of optimized impedance matching, conductive loss, dipole polarization, and abundant interfacial polarization induced by the hierarchical porous structure and N-doping. This facile and eco-friendly strategy provides a feasible reference for the rational design of high-efficiency microwave absorbers toward 5G/6G electromagnetic protection, aerospace radar stealth, and precision electronic device interference shielding.