Abstract: Compositing magnetic nanoparticles onto one-dimensional (1D) porous carbon matrices is of significant research value. This strategy is essential for fabricating high-efficiency and functionally synergistic microwave absorbers. In this work, 1D carbon materials are derived from tubular porous fibers via hyper-crosslinked polymerization. These materials serve as precursors to construct a series of composite fibers coated with Co/Zn metal-organic frameworks (C-CCNFs@Co/Zn-MOFs). The coating process is optimized, and the regulatory mechanism of Zn²⁺ ions on MOF grain size is revealed. Subsequent carbonization yields magnetic nitrogen-doped carbon-encapsulated cobalt/tubular carbon nanofibers (TCF/Co@NC). The TCF/Co@NC possesses a porous core-shell architecture and 1D morphology with abundant hetero-interfaces. These features facilitate the establishment of conductive loss networks and multiple reflections, resulting in strong energy dissipation capabilities. By adjusting the Co/Zn molar ratio, the electromagnetic parameters of the composite fibers can be optimized, thereby modulating their microwave absorption performance. The as-prepared NCT-3 (Co/Zn = 1 : 1) achieves a minimum reflection loss (RL_min) of -55.5 dB at a thickness of 2.7 mm. Meanwhile, NCT-2 (Co/Zn = 3 : 1) exhibits an effective absorption bandwidth (EAB) of 7.3 GHz at 2.4 mm. This study provides a versatile and referable methodology for designing high-performance magnetic carbon-based microwave absorbing materials.

Key words: Hyper-cross-linked polymers, Tubular fibers, Metal-organic frameworks (MOFs), Magnetic materials, Microwave absorbers