Pervasive mechanical impact is growing requirement for advanced high-performance protective materials, while the electromagnetic interference (EMI) confers severe risk to human health and equipment operation. Bioinspired structural composites achieving outstanding safeguards against a single threat have been developed, whereas the synergistic implementation of impact/EMI coupling protection remains a challenge. This work proposes the concept of nacre-mimetic hierarchical composite duplicating the "brick-and-mortar" arrangement, which consists of freeze-drying constructed chitosan/MXene lamellar architecture skeleton embedded in a shear stiffening polyborosiloxane matrix. The resulting composite effectively attenuates the impact force of 85.9%-92.8% with extraordinary energy dissipation capacity, in the coordinative manner of strain-rate enhancement, structural densification, lamella dislocation and crack propagation. Attributed to the alternate laminated structure promoting the reflection loss of electromagnetic waves, it demonstrates an ultraefficient EMI shielding effectiveness of 47.2-71.8 dB within extremely low MXene loadings of 1.1-1.3 wt %. Furthermore, it serves favorably in impact monitoring and wireless alarm systems and accomplishes performance optimization through the combination of multiple biomimetic strategies. In conclusion, this function-integrated structural composite is shown to be a competitive candidate for sophisticated environments by resisting impact damage and EMI hazards.
Keywords: EMI shielding; MXene; impact resistance; nacre-mimetic; shear stiffening.