Optimization of multiple attenuation mechanisms by cation substitution in imidazolic MOFs-derived porous composites for superior broadband electromagnetic wave absorption

Metal-organic frameworks (MOFs) derived composites are extremely potential electromagnetic wave (EMW) absorbers. However, the permittivity of absorbers directly derived from MOFs with solid structure is usually relatively low, inevitably limiting their further applications. Cation substitution can primely overcome the problem by regulating the morphology and atomic space occupation to enhance multiple loss mechanisms and impedance matching characteristics. However, universal mechanisms of the effect on EMW absorption performance influenced by cation substitution are still comparatively inadequate, which prospectively requires further exploration. Herein, a series of imidazolic MOFs were fabricated by ultrasonic symbiosis method and tailored by subsequent cation substitution strategy to prepare target porous composites. At a low filling rate and thin thickness, the as-obtained samples reach the optimal reflection loss and effective absorption bandwidth values of -49.81 dB and 7.63 GHz, respectively. The intercoupling between multiple atoms lays a significant foundation for abundant heterogeneous interfaces and defect vacancies, which effectively ameliorate the attenuation mechanisms. Meanwhile, the porous structure introduced by cation substitution reduces the bulk density to enhance the impedance matching and multiple reflections simultaneously. This study provides a helpful idea to exceedingly improve the EMW absorbing performance of imidazolic MOFs-derived composites by cation substitution. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

Metal-organic frameworks derived composites are promising EMW absorbers. Cation substitution can improve their absorption performance by regulating morphology and atomic space occupation. However, the mechanisms of how cation substitution affects EMW absorption performance are still not well understood. In this study, imidazolic MOFs were fabricated and tailored by cation substitution strategy to prepare porous composites. The samples showed optimal reflection loss and effective absorption bandwidth values under low filling rate and thin thickness conditions. The intercoupling between multiple atoms and the porous structure introduced by cation substitution contribute to the improved absorption performance.