writer：Ke Yang, Yuhong Cui, Qiang Li, Pei Liu, Qiuyu Zhang, Baoliang Zhang
keywords：Magnetic materials, Yolk-shell structure, Bimetallic MOFs, Microwave absorber, TiO2
source：期刊
specific source：Applied Surface Science
Issue time：2021年

Bimetallic MOFs with core–shell morphology are prepared by feeding step by step. Sandwich type ZIF-67@ZIF-8@TiO2 is prepared by coating TiO2 shell layer on the surface of the obtained ZIF-67@ZIF-8 via hydrolysistechnology. After pyrolysis of ZIF-67@ZIF-8@TiO2, ZnCo/NC@TiO2 composite wave absorber with yolk-shellstructure is fabricated. The evaporation of zinc, volatilization of organic components and shrinkage of carbonlayer at high temperature result in a larger cavity between the core and shell. Large specific surface area, pore volume and cavity structure are favorable for multiple interface reflection. Existence of multiple heterogeneous interfaces, unevenly distribution of space charges accumulated between the interfaces, abundant crystal defects and doped atoms lead to the continuous occurrence of interface/dipole polarization. These make the absorber exhibits excellent microwave absorption performance. The study shows that under the optimum carbonization temperature (700 ℃) and filler content (37%), minimum reflection loss (RLmin) of ZnCo/NC@TiO2 reaches ?? 46.21 dB@9.5 GHz with a matching thickness of 2.8 mm. Meanwhile, by adjusting the thickness of absorber, the effective bandwidth can cover 4.3–18 GHz. Maximum effective absorption bandwidth is up to 4.5 GHz. This work will provide a new strategy for the effective construction of yolk-shell microwave absorbing materials derived from bimetallic MOFs as well as performance optimization of existing microwave absorbing materials.