MOF-Derived Ni(1−x)Co(x)@Carbon with Tunable Nano–Microstructure as Lightweight and Highly Efficient Electromagnetic Wave Absorber

Intrinsic electric-magnetic property and special nano-micro architecture of functional materials have a significant effect on its electromagnetic wave energy conversion, especially in the microwave absorption (MA) field. Herein, porous Ni(1−x)Co(x)@Carbon composites derived from metal-organic framework (MOF) were successfully synthesized via solvothermal reaction and subsequent annealing treatments. Benefiting from the coordination, carbonized bimetallic Ni-Co-MOF maintained its initial skeleton and transformed into magnetic-carbon composites with tunable nano-micro structure. During the thermal decomposition, generated magnetic particles/clusters acted as a catalyst to promote the carbon sp(2) arrangement, forming special core-shell architecture. Therefore, pure Ni@C microspheres displayed strong MA behaviors than other Ni(1−x)Co(x)@Carbon composites. Surprisingly, magnetic-dielectric Ni@C composites possessed the strongest reflection loss value − 59.5 dB and the effective absorption frequency covered as wide as 4.7 GHz. Meanwhile, the MA capacity also can be boosted by adjusting the absorber content from 25% to 40%. Magnetic–dielectric synergy effect of MOF-derived Ni(1−x)Co(x)@Carbon microspheres was confirmed by the off-axis electron holography technology making a thorough inquiry in the MA mechanism. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40820-020-00488-0) contains supplementary material, which is available to authorized users.