Effect of different morphologies induced by in situ semi-conversion strategy on MOF-derived microwave absorbers.

[Display omitted] • Microwave absorbers were synthesized using an in situ semi-conversion strategy. • The maximum effective absorption bandwidth of the MOF derivative is 5.65 GHz. • Effect of micromorphology on microwave absorption properties was investigated. In the process of micro-designing metal organic frameworks (MOFs) to resist electromagnetic contamination, inappropriate parameter selection is likely to lead to skeleton collapse, thus rendering the microwave absorption (MA) performance failure. Herein, we propose an efficient in situ semi-conversion strategy. We etched and annealed the template FeNi-MOF-74 to finally obtain FeNi/graphite composites. Among them, the MOF derivative with a KOH etching concentration of 0.25 mol/L and an annealing temperature of 800 °C has excellent electromagnetic parameters and efficient MA performance, with an effective absorption bandwidth of 5.65 GHz and a minimum reflection loss of −64.11 dB at a thickness of only 1.8 mm. We controlled the electrical conductivity and polarization properties of the materials by varying the concentration of OH−, which effectively improved the impedance matching and enhanced the MA performance of the MOF derivatives. More importantly, this strategy closely related the microscopic nanostructure of MA materials to the macroscopic MA properties, providing unlimited possibilities for the preparation of high-performance MA materials. [ABSTRACT FROM AUTHOR]