Hollow Engineering of Fe₃O₄@C Composites via a Self-Templated Etching Strategy for Enhanced Electromagnetic Wave Absorption

Hollow-structured metal–organic frameworks (MOFs)-derived wave-absorption materials have attracted much attention due to their large specific surface area, high porosity, and versatile microinterfaces. However, accurately designing hollow-structured MOFs derivatives remains a challenge. In this work, the morphology and structure of the MOFs are skillfully tuned using the self-templated etching technique to establish a correlation between the structure and microwave absorption properties. The results show that the hollow structure enhances the impedance matching and attenuation, resulting in a significant improvement in the microwave absorption of the hollow Fe3O4@C composites compared to the unetched Fe3O4@C composites. The minimum reflection loss of the hollow Fe3O4@C composite can reach −54.95 dB when the thickness is only 1.73 mm, and the maximum effective absorption bandwidth (≤−10 dB) can reach 5.5 GHz at the thickness of 1.93 mm. This work highlights the self-templated etching method as an effective route to manipulate the morphology and properties of Fe-MOF derivatives.