Tailoring Self-Polarization of Bimetallic Organic Frameworks with Multiple Polar Units Toward High-Performance Consecutive Multi-Band Electromagnetic Wave Absorption at Gigahertz

Multiple relaxation behaviors are promising for broad frequency band and strong electromagnetic wave (EMW) absorption based on polarization-controlled electromagnetic (EM) attenuation. However, rational selection of materials and structure manipulation through tunable substitution or phase control are challenging toward optimization of EMW absorption. Herein, bi-metallic organic frameworks (B-MOFs) with various morphologies are employed as EMW absorbers. Remarkably, the polar units can be enhanced by introducing Ni-metal nodes into the Cu-coordinated MOFs, rendering the B-MOFs with self-polarized properties and consecutive multifrequency EMW absorption behaviors. The maximum reflection loss of acetylene black (ACET) filled NiCu-MOFs can reach -40.54 dB together with a wide bandwidth (<-10 dB) of 5.87 GHz at a thickness of 2.5 mm. As a counterpart of the Ni/Cu/C derivatives, significantly increased broad band absorption (6.93 GHz) and multifrequency absorbing and polarization characteristics are also maintained in bimetal coexisting carbonized architectures as prepared by calcination of CuNi-MOFs. This work demonstrates that the performance of effective absorbing frequency band can be enhanced in multi-metallic organic frameworks-based architectures, and paves a novel avenue for developing broadband and strong EMW absorbers.