Synergistic enhancement of defect-induced polarization and built-in electric field effect in carbon hybrids towards efficient electromagnetic wave absorption

The incorporation of a built-in electric field (BIEF) in nanocomposites has been well-recognized as a mainstream approach for enhancing the interface polarization. Nevertheless, the effect of sole BIEF on the dielectric loss is insufficient, and its combination with other loss mechanisms is necessary to achieve optimized electromagnetic wave performances. Herein, the nano carbon hybrids with Cu-ZnO Schottky BIEF with abundant defects were designed and derived through an etching and ligand exchange process, which involved the conversion of CuZnBTC into a bimetallic ZIF structure. The conversion process effectively controlled the morphologies and induced a significant density of defects in the derivatives, thereby imparting diverse electrical conductivities and dielectric properties to the composites. This was achieved through the modulation of the cell volumes of Cu-ZnO poly- crystals, the oxygen vacancies in ZnO, the nitrogen defects within the carbon matrix, and the creation of extensive heterointerfaces. The analysis indicated that the polarization relaxation dominated the dielectric loss. When the H2O/methanol in etching solvent was 3:7, the derived composite (S2) exhibited well matched impedance, and synergistic enhancement of BIEF effect and defect-induced polarization. Attributed to these merits, S2 achieved an ultra-wide effective absorption bandwidth (EAB) of 7.12 GHz at 2.3 mm. Notably, the EAB exceeded 6.0 GHz when the matched thickness ranged from 1.8 mm to 2.7 mm. This study can introduce a novel approach for the development of advanced absorbers based on the Schottky BIEF.