Enhancing microwave absorption via ion exchange-regulated metal elemental-alloy transition behavior

Abstract

Metal-organic frameworks (MOFs) are considered as suitable candidates for excellent microwave absorption (MA) materials. However, the influence of the transition behavior from metal to alloy dominated by the metal ion ratio and the accompanying multi-phase coexistence model on the MA mechanism is unclear. This study successfully prepared a series of porous electromagnetic composite materials through ion-exchange in-situ pyrolysis synergistic strategy. The results indicate that the modulation of the Fe/Co ion ratio can easily manipulate the phase transition from Co metal to FeCo alloy-cobalt ferrite and the crystal defects within. The state of metal/alloy coexistence obtained at a low ion exchange degree has the highest concentration of vacancies, which is conducive to wideband absorption (6.03 GHz) and efficient loss (−67.44 dB) of MA performance. In contrast, the MA performance of samples at medium/high ion exchange degrees is not ideal. In addition, the application prospects of this material were demonstrated by simulating the actual absorption situation using radar cross-section. In summary, this work reveals the intrinsic relationship between the phase evolution behavior determined by the ion exchange degree in MOF derivatives and the electromagnetic performance, as well as the MA mechanism, providing a new reference for the preparation and design of outstanding MA materials.