Electromagnetic wave radiation disrupts electronic devices and threatens human health. Microwave absorbing materials are essential for addressing electromagnetic pollution and military stealth applications. Advancement of electronics creates demand for absorbers with thin thickness, light weight, wide bandwidth, and strong absorption. Conventional materials suffer from poor impedance matching and limited loss mechanisms in the Ku band. Heterojunction engineering offers solutions through control of band alignment and charge distribution. The built-in electric field serves as a core mechanism for enhancing dielectric loss. However, limitations exist in understanding of formation mechanisms of built-in electric fields in multi-interface systems. This study develops a ZnNiCo-LDH/MXene composite with coral-inspired architecture. Construction of high-density Mott–Schottky interfaces occurs through electrostatic assembly of polar semiconductor units and conductive matrices. Vertical growth of flower-like layered double hydroxide (LDH) on MXene extends propagation paths of electromagnetic waves. This design creates continuous networks of built-in electric fields. Enhanced charge separation and interfacial polarization result. Performance demonstrates −49.6 dB reflection loss at 1.35 mm thickness. Effective bandwidth reaches 3.4 GHz across Ku-band frequencies. Radar cross-section simulations confirm −39.57 dB·m² signal suppression. These achievements meet requirements of advanced absorbers. The work establishes a new paradigm for manipulation of built-in electric fields through multi-interface engineering.