Binder-free CNT@Fe₃O₄/CoNi-C superflexible buckypaper derived from metal-organic frameworks as highly efficient microwave absorber

Achieving self-supporting superflexible binder-free composites where all components serve simultaneously as structural backbones and microwave-absorbers is a technical challenge. This study successfully combined several microwave absorbing materials, including Fe₃O₄, NiCo-MOF derivatives, and CNTs, into a binder-free self-supporting superflexible Buckypaper in one step through directional pressure filtration. Fe₃O₄-CoNi-MOF was in-situ grown on a single CNT to form a magnetic MOF-coated CNT (CNT@MOF), which was then subjected to high-temperature carbonization to obtain a magnetic MOF-derived carbon-coated CNT (CNT@Fe₃O₄/CoNi-C). The combination of Fe₃O₄/CoNi-MOF and CNTs simultaneously promotes magnetic loss and dielectric loss, thereby significantly enhancing impedance matching and electromagnetic energy attenuation capabilities. The optimal carbonization temperature for the CNT@Fe₃O₄/CoNi-C Buckypaper is 700 ℃, at which the minimum reflection loss (RL_min) is −58.12 dB and the absorption bandwidth is 5.02 GHz. The interweaving of CNTs forms a robust yet superflexible skeleton, while the in-situ growth of Fe₃O₄/CoNi-MOF derivatives on a single CNT enhances the structural stability of the skeleton. The Buckypaper remains intact after repeated 2 mm-radius curling, knotting, 180° bending. Therefore, this study presents new insights into the preparation of self-supporting, superflexible MOF-derived microwave absorption materials.