Bimetallic zeolitic imidazolate frameworks-derived porous carbon-based materials with efficient synergistic microwave absorption properties: the role of calcining temperature

The composites of metal Co embedded in porous and N-doped graphitized carbon matrix (Co@pNGC) have been successfully synthesized by thermal decomposition of the bimetallic zeolitic imidazolate frameworks (bi-ZIFs) at different temperatures. The experimental results show that the calcination temperature played a decisive role on the graphitization, specific surface area, pore structure and electromagnetic wave (EM) absorption properties of Co@pNGC. The composites, Co@pNGC-600 and Co@pNGC-700 obtained at 600 degrees C and 700 degrees C, respectively, exhibit an outstanding EM wave absorption performance, which attributes to the synergistic effects of dielectric and magnetic loss, porous structure and multicomponent interfaces. Specifically, the optimal reflection loss of Co@pNGC-600 is -50.7 dB at 11.3 GHz and the widest effective absorption bandwidth (< -10 dB) could reach upto 5.5 GHz (12.3-17.8 GHz). The minimum thickness corresponding to the effective absorption is only 1.2 mm for Co@pNGC-700. Hence, these obtained porous carbon composites are promising microwave absorbing materials due to their lightweight, thin thickness, low filling, broad bandwidth, and strong absorption.