Multifunctional C/Co Aerogels with Integrated Robustness, Hydrophobicity, Flame Retardancy, and Microwave Absorption Performance

To address the challenges posed by complex application scenarios, the development of microwave absorbing materials with hydrophobicity and flame retardancy has become a critical direction for next-generation communication technologies. In this study, poly(vinyl alcohol), a metal–polyphenol framework (Co 2+ –tannic acid), and aramid nanofibers (ANF) were self-assembled into the precursor aerogel through hydrogen and coordination bonds, where ANF enhanced the mechanical robustness. Then, after the carbonization process, porous C/Co aerogels were developed. The magnetic properties and graphitization degree of the C/Co aerogels were precisely tailored by modulating carbonization temperatures, enabling tunable microwave absorption performance. The C/Co aerogel carbonized at 800 °C achieved a minimum reflection loss (RL min ) of −65.2 dB at 2.48 mm thickness along with an effective absorption bandwidth of 4.48 GHz at 1.52 mm thickness. The optimized impedance matching, driven by synergistic magnetic–dielectric loss mechanisms, underpins its exceptional microwave absorption. Furthermore, the C/Co aerogel exhibited remarkable compressive strength (593.1 kPa), hydrophobicity (a hydrophobic angle of 124°), and flame retardancy. This work provides a strategic framework for designing multifunctional high-efficiency microwave absorbers.