The Matthew effect of defects in microflowers CuS/carbon foam composite optimizes the dielectric response for high-performance microwave absorption

Dielectric loss-type electromagnetic (EM) wave absorption materials have attracted considerable interest owing to their tunable structures and compositions. However, achieving highly efficient absorption performance remains challenging, governed by the complex synergy between polarization (dipole/interface) and conductive loss mechanisms. Herein, lightweight CuS/carbon foam (CF) composites are prepared by integrating CuS microflowers onto KOH-modified CF surfaces via a simple solvothermal method, where defect engineering induces the Matthew effect to optimize dielectric response. The porous structure of CF not only facilitates the in-situ growth of defect-rich CuS but also extends multiple reflection and scattering pathways, synergistically enhancing dielectric loss. Furthermore, the CuS/KCF heterointerface and defect is modulated by varying CuS content. After optimization, conductive loss dominates at low frequency, whereas polarization loss prevails at high frequency. Consequently, the CuS/KCF composite achieves a minimum reflection loss of −69.81 dB at 2.42 mm, with an effective absorption bandwidth of 4.2 GHz at thicknesses ranging from 2.28 to 2.72 mm. Additionally, a radar cross-section reduction value reaches 30.06 dB⋅m², and the optimal compressive strength attains 15.82 MPa, confirming its application potential. This work demonstrates defect-engineering strategy to develop high-efficiency wave-absorption materials.