Structure regulating of metal clusters in carbonized metallic organic frameworks for high-efficient microwave absorption via tuning interaction strength between metals and ligands

Carbonized metallic organic frameworks (CMOF) have been attracting attention in microwave absorption (MA) research area because of their diverse structures, tunable compositions, and rich porosity. Herein, structure regulation on metal clusters in CMOF is achieved by tuning the interaction strength between metals and ligands to enhance microwave absorption performance. Due to relatively weak interaction among copper cations and ligands, copper nanoclusters (CuNC) can be uniformly formed and embedded within the cobalt/zinc (Co/Zn) CMOF. Firstly, copper cations are added to the Co/Zn bimetallic zeolitic imidazolate frameworks (ZIFs). Secondly, the CMOF composite particles with CuNCs (CuNCs/CoZn-CMOF) were developed by a pyrolysis process. The CuNCs/CoZn-CMOF with an appropriate amount of CuNCs can harmonize both dielectric and magnetic losses. As a result, the minimum reflection loss (RL_min) reaches –45.1 dB at a matching thickness of 2.30 mm and the effective absorption bandwidth (EAB) is 8.80 GHz at a thickness of 3.10 mm. The broadband response to electromagnetic waves is attributed to interfacial polarization at CuNCs surface and heterogeneous interfaces, impedance matching and multiple scattering of electromagnetic waves. This study provides a feasible method to develop CMOF microwave absorption materials with high EAB values.