Ligand-directed construction of CNTs-decorated metal carbide/carbon composites for ultra-strong and broad electromagnetic wave absorption

Multi-component hierarchical carbon-based materials with large accessible specific surfaces and abundant heterojunctions have been regarded as promising candidates for high-performance electromagnetic wave (EMW) absorbers, yet rational construction is still challenging. Herein, we demonstrate “ligand-directed post-modification” as an effective strategy to transform bimetallic MOFs into well-defined multi-dimensional hierarchical composites. Using l-histidine ligand modified ZIF-8 as novel MOF precursor, Ni2+ can be incorporated in a controlled manner via coordination, leading to the formation of Ni3ZnC0.7/carbon nanotube (CNT)/nano-porous carbon (NPC) composites after pyrolysis. The obtained composites exhibit the optimal reflection loss (RL) of −66.6 dB at 2.58 mm and broad effective absorbing bandwidth (EAB) covering 7.04 GHz at 2.49 mm. Moreover, the EAB range can be further expanded to 7.76 GHz by tuning the Ni content, which outperforms the majority of reported MOF-derived absorbers. The superior microwave absorption performance relies on the synergistic effects based on conduction loss and abundant dipole/interfacial polarization originating from the hierarchical structures composed of 0D Ni3ZnC0.7 nanoparticles, 1D CNT and 3D porous carbon, as well as the optimized impedance matching characteristic arisen from the large specific surface area (≥373 m2/g) of the composites. Hence, this work presents a new strategy to rationally construct hierarchical multi-component carbonaceous materials derived from MOFs with desirable functionalities.