Synergistic regulation and efficient electromagnetic wave absorption of MOF-derived Co/TiO2@C hierarchical structures

• Co/TiO 2 @C composites are derived from bimetallic MOF. • • Minimum reflection loss of −64.5 dB at 1.8 mm thickness is achieved. • • Effective absorption bandwidth of 3.2 GHz in X-band. • • Hierarchical structure boosts interfacial and dipole polarization. In this study, disk-shaped MIL-125(Ti,Co)- x precursors were synthesized via a solvothermal method with varying CoCl 2 ·6H 2 O content, and subsequently Co/TiO 2 @C composites were fabricated through a two-step pyrolysis process. The precursor morphology transforms from intact micron-scale disks into thinner flakes, and ultimately into fragmented structures with increasing the cobalt content. The pyrolysis temperature concurrently governed the composition of TiO 2 phase, the degree of carbon graphitization, and the distribution of nanoparticles. The optimized Co/TiO 2 @C(700)-2 composite achieves a minimum reflection loss of −64.5 dB at a matching thickness of 1.8 mm, and exhibits an effective absorption bandwidth of 3.2 GHz at 2.1 mm. The outstanding electromagnetic wave absorption properties stem from a favorable synergy between adequate attenuation and satisfactory impedance matching, supported by the conductive carbon network, abundant defect sites, multiple TiO 2 /carbon heterointerfaces, and hierarchical porous architecture. These results establish the cooperative regulation of electromagnetic wave absorption properties by cobalt content and pyrolysis temperature, offering a strategy for the design of MOF-derived lightweight absorbers with tunable electromagnetic wave absorption. Download: Download high-res image (139KB) Download: Download full-size image