Nanocurvature‐Activated Dipolar Polarization in M–N ₄ Single‐Atom Sites for High‐Performance Electromagnetic Wave Absorption

ABSTRACT The dielectric response of carbon‐based single‐atom (SA) absorbers is intrinsically constrained by the highly symmetric charge distribution of planar M‐N ₄ coordination motifs, which suppresses dipole polarization and limits electromagnetic wave (EMW) attenuation. Here, a nanocurvature‐driven symmetry‐breaking strategy is proposed to activate latent dielectric polarization at SA sites through geometric regulation. By combining click chemistry with template‐assisted synthesis, metal SAs are anchored onto hollow nitrogen‐doped carbon spheres with precisely tunable diameters, enabling systematic modulation of local nanocurvature. Theoretical calculations and experimental analyses reveal that curvature‐induced surface charge accumulation disrupts the electronic symmetry at Ni‐N ₄ centers, markedly enhancing local charge density, dipole moments, and polarizability. Consequently, the optimized Ni/HNC‐200 absorber achieves an ultralow minimum reflection loss of −74.1 dB, representing a staggering 390% enhancement over HNC‐200 (−15.1 dB), and exhibits a reduced radar cross section of −70.49 dB m ² . A flexible electronic patch further demonstrates over fivefold suppression of electric‐field radiation from mobile phone chips. The universality of this mechanism is validated in Co‐ and Cu‐based systems, establishing nanocurvature as a geometry‐enabled design paradigm for high‐performance SAs EMW absorbers.