Polymerization-induced assembly-etching engineering to hollow Co@N-doped carbon microcages for superior electromagnetic wave absorption

Hollow engineering is an effective approach to optimize impedance matching and modify magnetic-dielectric synergy for enhanced wave absorption capability, but the composition and microstructure manipulation of metal-organic frameworks (MOFs)-derived absorbers remains a challenge. Herein, a novel and facile polymerization-induced assembly-etching strategy is proposed for the manufacture of wrinkled zeolitic imidazolate framework-67@polypyrrole (ZIF-67@PPy) microcages using ammonium persulfate catalyzed pyrrole polymerization and concomitant acid etching. Then, hollow cobalt@N-doped carbon microcages (Co@NCMs) with distorted carbon shells, rich core-shell heterojunctions, highly dispersive Co nanoparticles, and abundant heterogeneous interfaces are produced via high-temperature pyrolysis process, which eliminates the need for additional templates and etching agents. Moreover, the hollow microcage structure with interior cavities and mesopores provides superior impedance matching and lightweight characteristics to the absorbers. Therefore, the hollow absorbers demonstrate a minimum reflection loss of −50.4 dB and an effective absorption bandwidth (EAB) of 3.85 GHz at 2.7 mm with a 10 wt% filler loading. In general, the polymerization-indued assembly-etching strategy inspires the hollow engineering of MOF derivatives, and facilitates the development of superior electromagnetic wave absorption (EMA) materials.