Regulating the Asymmetric Coordination Environment of Single‐Atom Cobalt Within Hierarchical Hollow Carbon for Broadband Electromagnetic Wave Absorption

ABSTRACT The development of lightweight and broadband electromagnetic wave (EMW) absorbers with controllable electromagnetic response and integrated multifunctionality remains a critical challenge for next‐generation electromagnetic protection technologies. Herein, we construct hierarchical hollow carbon architectures featuring S–N dual‐anchored Co single atoms (CoSN/HPC) to elucidate the role of asymmetric atomic coordination in regulating EMW attenuation. The hierarchical hollow framework establishes multiscale conductive and dielectric interfaces, enabling optimized impedance matching and prolonged electromagnetic propagation pathways, while the asymmetric Co–N/S coordination environment modulates local electronic structures and generates abundant atomic‐scale polarization centers. The synergistic between structural confinement and electronic regulation promotes polarization relaxation and conductive dissipation, leading to efficient conversion of electromagnetic energy into thermal energy. As a result, CoSN/HPC delivers outstanding EMW absorption performance with a minimum reflection loss of −61.1 dB and an effective absorption bandwidth (EAB 10 ) of 7.0 GHz. Furthermore, the integration of CoSN/HPC into flexible self‐supporting films (CoSN/HPCF) maintains broadband absorption capability (EAB 10 > 7.0 GHz) while simultaneously providing mechanical durability, hydrophobicity, flame retardancy, and infrared camouflage functionality. This work establishes an atomic‐level coordination engineering strategy to manipulate electromagnetic energy conversion through single‐atom electronic regulation, offering new insights into the design of multifunctional EMW absorbers for complex electromagnetic environments.