A control strategy for microwave absorption performance on a two-dimensional scale

Abstract

Two-dimensional (2D) zeolitic imidazolate frameworks (ZIFs) are promising materials for microwave absorption for their desirable features. However, there has been a lack of a corresponding relationship between the growth pattern of 2D ZIF materials at the micro-scale and the macroscopic microwave absorption performance. This work synthesized 2D ZIF-L and its derivatives via a precise structural regulation strategy. By changing the axial orientation of crystal growth, the synthesis of two-dimensional bladed and rod-shaped precursors with controllable thickness and varying shapes at the macro scale was controlled. The leaf-like structure of ZIF-L derivates with large surface area is beneficial for the exposure of reactive oxygen vacancies, increasing the relaxation loss. While the ultra-thin rod-shaped structure which can shorten the electron migration and jump paths to reduce the energy barrier is advantageous to conductive loss. As a result, the prepared L-7 exhibits superior electromagnetic wave absorption ability with the widest effective absorption bandwidth (EAB) of 5.53 GHz at a thickness of 1.80 mm. When the total thickness is 1.90 mm, R-7 can exhibit the minimum reflection loss (RLmin) value of about −60.40 dB. This study emphasizes the 2D scale regulation for obtaining new generation and environmentally friendly microwave absorbers. Metal-based materials derived from ZIF-L with extremely thin thicknesses and a large surface area have shown great potential in microwave absorbers.