Three-dimensional FeMZn (M = Co or Ni) MOFs: Ions coordinated self-assembling processes and boosting microwave absorption

Herein, we construct two metal–organic frameworks (MOFs) composite nanoflowers (NFs) with anisotropic binary assembled structures by a facile one-pot method. Different from the two-step epitaxial growth method, the anisotropic assembly of the binary MOFs (MOF-5 and MIL-88B) in the mixed system can be realized without preparing the template MOFs. The ions coordinated self-assembling behaviors during the formation of the three-dimensional (3D) structure are clarified. The absorbing mechanisms of the derivative absorber are elucidated. The results indicate that the special hierarchical assembled structure endows absorbers with rich heterogeneous interfaces, porous structure, suitable impedance matching and complementary loss mechanisms. The optimized absorbers FeCoZn@C NFs and FeNiZn@C NFs exhibit outstanding microwave absorption performance. Only with a matching thickness of 1.9 mm, the effective absorbing bandwidth (EAB, reflection loss (RL) < −10 dB) of the absorber covers 6.0 GHz (12–18 GHz, the entire Ku band). The minimum reflection loss (RL_min) reaches −53.1 dB (loss of electromagnetic waves above 99.999%). This study might shed light on the preparation of high-performance microwave absorbers with sophisticated structures.