Honeycomb-like Co/C composites derived from hierarchically nanoporous ZIF-67 as a lightweight and highly efficient microwave absorber

A simple method synthesizing hierarchically porous Co-based zeolitic imidazolate frameworks (ZIF-67) is presented. In approach, polyvinyl pyrrolidone (PVP) aggregates on graphene oxide (GO) surface through H-bond between oxygen-containing groups (-OH and -COOH) on GO and -C=O in PVP and the results GO/PVP composites is used as a template to synthesize hierarchically porous ZIF-67. After in situ postpyrolysis heat treatment in Ar atmosphere, honeycomb-like Co/C composites with abundant hierarchically pores are obtained. The hierarchically porous structure endows the as-obtained Co/C composites with highly efficient microwave absorption performances. The maximum reflection loss can reach -50.7 dB and the effective bandwidth is 4.6 GHz at a filler loading as low as 10 wt%. Notably, the electromagnetic parameters analysis indicates that such excellent microwave absorption properties are mainly ascribed to well-matched impedance combined with strong attenuation property induced by the hierarchically porous structure. More importantly, this strategy could also be used to fabricate other MOF-derived high performance microwave absorbers.