Rhombic dodecahedron Ce–Co/C composites with porous hollow structure for efficient electromagnetic wave absorption

The excellent electromagnetic wave (EMW) absorption performance of metal organic frameworks (MOFs) has attracted a lot of attention. In this work, zeolitic imidazolate framework-67 (ZIF-67) was synthesized hydrothermally using 2-methylimidazole (2-mIm) as the organic ligand, cobalt nitrate hexahydrate (Co(NO3)2·6H2O) as the cobalt source and methanol (MeOH) as the organic solvent. The ZIF-67 was etched with cerium nitrate hexahydrate (Ce(NO3)3·6H2O), leading to rhombic dodecahedron Ce–Co/C composites with porous hollow structure after thermal annealing. In addition, the effect of the content of Ce(NO3)3·6H2O on EMW absorption performance of the Ce–Co/C composites was studied. Specifically, the sample Ce–Co/C-2 (Ce(NO3)3·6H2O): (ZIF-67 = 1:2) showed optimal EMW performance. For the Ce–Co/C-2 based composite with a filling ratio of 45 wt%, a RLmin reached −64.67 dB at 11.12 GHz with a thickness of 2.21 mm. The promising EMW absorption performance of the porous hollow structure was attributed to its large specific surface area and massive defects, multiple reflection/scattering, improved impedance matching and increased dielectric loss. This work provides a reference improve EMW absorption performance of MOF materials through regulating their microstructures.