MOFs-derived flaky carbonyl iron/Co@C core-shell composites for thin thickness and broadband microwave absorption materials

•Flaky carbonyl iron/Co@C composites are synthesized by polymerization and pyrolysis.•Porous carbon shell greatly contributed to the dielectric loss and impedance match.•Co proportion in porous carbon shell has great effect on electromagnetic properties.•Effective absorption bandwidth of 5.2 GHz is obtained at thickness of only 1.19 mm.•The composites demonstrated broadband absorption and thin thickness in Ku band.