Semiconductor MOF Metamaterials Enable Thin Structures with Robust Electromagnetic Wave Absorption

Developing thin electromagnetic wave (EMW) absorbers with ultra-broadband absorption is challenging, as current designs often struggle to achieve high causality efficiency (R_c), which measures effective absorption bandwidth (EAB) relative to thickness (ideal R_c is 1). Herein, a broadband semiconductor metal-organic framework (SC-MOF) metamaterial is proposed that approaches the R_c limit. The design synergizes both the micro and macro properties of the materials. On the micro scale, a 2D SC-MOF (CuHT) with a few-layer structure and tailored conductivityis synthesized, promoting a balance of attenuation and impedance matching to create an efficient EMW lossy network. On the macro scale, CuHT is dispersed in epoxy resin to form trapezoidal structures, with scattering topological design further enhancing causality efficiency and robustness. The CuHT metamaterial achieves an exceptional EAB of 33.4 GHz at just 3.9 mm thickness (R_c = 1.14), with stable performance under oblique incidence (within ±45°) and various polarizations. This advancement holds tremendous promise for developing robust EMW absorbers with superior performance.