Room-temperature electrochemical co-deposition of Cu-MOF/CNT heterostructures on carbon fibers for efficient microwave absorption at low filler loading

Carbon fibers (CFs) suffer from poor impedance matching despite strong dielectric loss, limiting their microwave absorption (MA) performance. Here, we developed a novel room-temperature electrochemical cathodic deposition strategy to in situ construct Cu-based metal–organic framework (Cu-MOF) layers on CF surfaces, simultaneously electrostatically assembling carbon nanotubes (CNTs) within these layers. The resulting Cu-MOF/CNT@CF features a heterostructure with an interpenetrating conductive network, maintaining the Cu-MOF's high porosity and intact heterointerfaces to optimize impedance matching, while enhancing conduction and polarization losses through the contribution of CNTs. At an ultralow filler loading of 5 wt%, Cu-MOF/CNT@CF achieves a remarkable maximum reflection loss (RL_min) of −60.6 dB at the thickness of 3.9 mm and an effective absorption bandwidth (EAB) of 4.06 GHz at 2.5 mm, representing 32% and 37% improvements over pristine CF, respectively. This mild, efficient, and damage-free approach provides a promising pathway for designing high-performance, lightweight structural-functional microwave absorbers.