Scalable Interfacial Engineering of Covalently Interlocked Hierarchical CNT/Phase Change Composite for Multifunctional Thermal Management and EMI Shielding

Carbon nanotube (CNT)‐based hierarchical architectures offer a promising platform for engineering multifunctional materials with synergistic thermal, electrical, and optical properties. However, weak interfacial coupling between CNTs and growth substrates compromises structural robustness, hindering practical implementation. Here, a scalable dual‐silanization‐assisted chemical vapor deposition strategy is developed to construct a covalently bonded organosilica interlayer, thereby creating a robust interlocked CF@CNTs hierarchical architecture. Experiments and density functional theory calculations reveal that interlayer enhances charge transfer and interfacial binding strength, suppressing CNT detachment. Leveraging this robust architecture, we fabricated a multifunctional phase change composite (PCC) that effectively resolves the inherent trade‐off between latent heat storage and thermal/electrical transport. The resulting PCC maintains a high latent heat of 210.17 J·g −1 while delivering a thermal conductivity of 0.760 W·m −1 ·K −1 and an electrical conductivity of 802.56 S·m −1 . Consequently, it lowers electronic device operating temperatures by 9°C, achieves an average total shielding effectiveness of 41.51 dB·mm −1 , and reaches a photothermal conversion efficiency of 93.36%. Notably, this interfacial engineering strategy is readily extendable to 0D, 1D, 2D, and 3D substrates, enabling scalable integration of CNT‐based architectures. This work establishes interfacial coupling engineering as a versatile design principle for constructing robust CNT‐based architectures, opening new opportunities for multifunctional materials.