In Situ Constructed Pore‐Chain Interlocked Networks in Polyimide‐Covalent Organic Framework Nanocomposites Enable Ultralow k Dielectrics for High‐Fidelity Signal Transmission

The ultralow k porous polymer dielectrics have been widely explored for Integrated circuit (IC) interconnects, 5G/6G communications, and wearable devices. However, disordered pore structures and poor interfacial adhesion remain a major challenge, thus making it difficult to decouple the k ‐tanδ trade‐off. Here, we employ hollow covalent organic frameworks (H‐TD‐COF) as multifunctional molecular anchoring nodes to construct robust pore‐chain interlocked networks in polyimide nanofibrous films. The amino‐functionalized COF shells participate in the in situ growth of polyimide (PI) chains, thus enabling interlocked interfaces that fundamentally restrict segmental mobility and suppress dipolar relaxation. Subsequent electrospinning technique allows anchored chains to be stretched along the fiber axis and immobilizes them within an oriented fibrous architecture. This simultaneously disrupts long‐range charge migration pathways while preserving stress‐transfer and heat‐dissipation continuity. The resulting PI‐g‐COF (4) nanocomposites with 4 wt% H‐TD‐COF loading achieve an ultralow dielectric constant of 1.50 and dielectric loss of 0.001 at 1 kHz, with highly stable dielectric properties up to 250°C. Notably, device‐level measurements further reveal a signal‐to‐noise‐and‐distortion ratio (SINAD) of 22.30 dB under 200 MHz crosstalk interference, showing a 52.2% improvement over commercial polyimide. This work lays solid foundations for nanoscale interfacial regulation in porous polymer nanocomposites towards ultralow k dielectrics.