MOF-derived yolk-shell Ni@C@ZnO Schottky contact structure for enhanced microwave absorption

Metal-organic frameworks (MOF) derivative used as microwave absorber has been attracting extensive interest due to the diversity of host-guest coordination and unique structure at micro/nano-meters level. However, the accurate adjustment of metal-semiconductor interfaces construct remains a great challenge. Here, a novel hierarchical multi-interfacial Ni@C@ZnO microsphere with special Schottky contact structure was successfully fabricated after annealed the bimetallic Ni-Zn-MOF precursor. The unique yolk-shell microsphere was assembled together by the core-shell Ni@C micro-units and ZnO flakes. The uniformly dispersed ZnO flakes were anchored inside the hierarchical conductive carbon matrix. The yolk-shell Ni@C@ZnO materials displayed high-performance microwave absorption after the micro-nano structure and interfacial design were optimized. In particular, with a low mass additive amount of only 25%, the maximum reflection loss (RL) reached -55.8 dB at 2.5 mm, and the effective absorption bandwidth (RL <= -10 dB) covered as wide as 4.1 GHz. The excellent microwave absorption performance could be attributed to the polarized interfaces of Ni-C-ZnO, which contributes a metallic/semiconductor barrier. Thus, both magnetic-dielectric synergetic effect and interfacial polarization might lead to an evident absorption. This novel lightweight magnetic MOF-derived composites promise great potential in the practical microwave absorption fields.