Zn-MOF-derived hierarchical carbon nanorods superstructures with tunable microwave absorption properties

Nanometer/micron scale multilevel superstructure has the potential to be a good microwave absorbing (MWA) materials owning to its large specific surface area and good electrical conductivity, but assemble 1D rod/wire-like into a three-dimensional (3D) hierarchical superstructure with a large controllable radius of curvature spherical tissue, is still a challenge. Here we demonstrate a self-templated strategy through pyrolysis the modulator (urea) modified Zn-MOF 74 to obtain the spherical superstructure of carbon nanorods (SSC). The dielectric constant of SSC absorbers regulated by the amount of urea added. A moderate amount of urea will endow the material a high specific surface area and defect-induced mesopore, thus the excellent MWA properties. The prepared SSC-U2 has a good MWA performance that the minimum reflection loss (R_{L, min}) can reach -54 dB only when the thickness is 2.1 mm. This work designs a new strategy to prepare the 3D hierarchical superstructure carbon by using MOFs and offers insight into the relationship between morphology, surface area and dielectric constant of absorber, promoting rational design of highly efficient microwave absorber.