Ternary assembled MOF-derived composite: Anisotropic epitaxial growth and microwave absorption

In recent years, metal-organic framework (MOF)-derived absorbers have attracted much attention in the field of microwave absorption. It is interesting and difficult to construct multiple MOF-on-MOF heterostructures. Herein, we combine two unique anisotropic epitaxial growth strategies to build binary assemblies DUT-52@MIL-88B (DM) and DUT-52@MIL-88C (DMC), and then the ternary assembly DUT-52@MIL-88B@MIL-88C (DMM). The formation mechanisms of the assembled structure are clarified. Besides, they are converted into magnetic porous carbon-based absorbers (DM-700 and DMM-700) through a facile carbonization process. The microwave absorption mechanisms are elucidated. The results indicate that the exquisite multi-element composite structure endows the absorber with suitable impedance matching characteristics, complementary loss mechanisms and excellent electromagnetic loss capabilities. It is worth noting that DM-700 exhibits a remarkable minimum reflection loss (RL_min) of −67.5 dB under a matching thickness of 3.6 mm, corresponding to an effective absorption bandwidth (EAB, RL < −10 dB) of 2.0 GHz and the filler loading of 55%. The optimized absorber DMM-700 successfully achieves the optimization of the above-mentioned microwave absorbing properties. While maintaining the desirable RL_min (−56.4 dB), the matching thickness is reduced (2.4 mm), and at the same time, EAB is doubled (4.0 GHz). This study might provide a new idea for the construction of sophisticated absorbers with multi-MOF-on-MOF structures.