Self-sacrificial templating of Zn/Co Bimetallic ZIF derivatives: synergistic dielectric-magnetic engineering for ultra-broadband microwave absorption

Traditional ZnO-based microwave absorbers and monometallic ZIF systems suffer from narrow effective absorption bandwidths due to impedance mismatch and insufficient magnetic-dielectric synergy. To address these limitations, this study proposes a self-sacrificial template strategy for constructing Zn/Co bimetallic zeolitic imidazolate frameworks (ZIFs) using spherical ZnO as a dynamic coordination host. Unlike conventional hard-template routes, the self-sacrificial templating strategy allows atomic-level control over morphology and composition via in-situ dissolution–recrystallization, leading to hierarchical architectures with rich heterointerfaces. By tuning the Co²⁺ content (0.1–0.3 g) and pyrolysis temperature (700–900 °C), the resulting carbon-based composites exhibit precisely regulated microstructures and balanced electromagnetic properties. The structural evolution and composition were systematically investigated using X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM/HRTEM), X-ray Photoelectron Spectroscopy (XPS), and Vibrating Sample Magnetometry (VSM). The optimized derivative pyrolyzed at 800 ℃ (PSE3-2–800) exhibited exceptional microwave absorption performance, achieving a minimum reflection loss (RL_min) of − 51.24 dB at 4.2 mm thickness and an ultra-wide effective absorption bandwidth (EAB) of 7.36 GHz (10.64–18.00 GHz) at 2.3 mm. Structural and compositional analyses revealed that the hollow architecture formed via ZnO carbothermal reduction, coupled with graphitized carbon matrices embedded with Co₃ZnC nanoparticles and atomic Co-Nx sites, synergistically enhanced dielectric polarization, magnetic resonance, and multi-path scattering. This work provides a paradigm for designing lightweight broadband absorbers through defect engineering and bimetallic coordination, overcoming the limitations of single-component systems in balancing impedance matching and multi-loss mechanisms.