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

The as-prepared N-doped porous carbon microwave absorption material derived from Zn-benzimidazole (Zn-BIM) exhibits excellent electromagnetic wave absorption performance, achieving a minimum reflection loss (RL m ᵢ n ) of −57.33 dB with an effective absorption bandwidth (EAB) of 8.72 GHz at a matching thickness of only 2.41 mm. • The effects of Zn 2+ /BIM molar ratio and concentrated NH 3 ·H 2 O dosage on the microstructure and electromagnetic wave absorption performance of Zn-BIM derived carbon are systematically investigated. • The ethanol solvent and strong alkaline conditions facilitate the formation of low-crystallinity Zn-BIM frameworks with abundant defects. Such structure endows the material with abundant defect sites, heterogeneous interfaces and porous structures, thereby enhance its electromagnetic wave absorption capability. • After high-temperature pyrolysis, the Zn-BIM derived N-doped porous carbon effectively optimizes impedance matching and strengthens dielectric loss, realizing synergistic regulation of microwave absorption performance through impedance matching, dipole polarization, interfacial polarization and conductive loss. 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 NH 3 ·H 2 O 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 NH 3 ·H 2 O dosage. The optimized sample delivered exceptional microwave absorption performance at a Zn/BIM molar ratio of 1:2 and NH 3 ·H 2 O 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. In this work, N-doped porous carbon materials were fabricated via high-temperature pyrolysis of Zn-BIM coordination polymers, using ethanol as the solvent and concentrated NH 3 ·H 2 O as the alkali source. The molar ratio of Zn 2+ to BIM ligand and the dosage of NH 3 ·H 2 O were systematically regulated. Experimental results reveal that the as-prepared material delivers excellent microwave absorption performance. When the molar ratio of Zn 2+ to BIM ligand is 1:2 and the NH 3 ·H 2 O dosage of 9 mL. Its minimum reflection loss (RL m ᵢ n ) reaches −57.33 dB, and the effective absorption bandwidth is up to 8.72 GHz. The superior absorption performance originates from the synergistic effect of multiple scattering induced by the structure defects. This work provides a new strategy to design lightweight microwave absorbers with strong absorption and broad bandwidth. Download: Download high-res image (417KB) Download: Download full-size image