In Situ Growth of ZIF-8 on Poly( <i>p</i> -phenylene benzobisoxazole) Nanofibers for Flame-Retardant Nanopaper with Ultralow Dielectric Constant and Enhanced Mechanical Strength

To meet the practical application demands in the fields of high-frequency communication and smart building applications, it is imperative to develop low dielectric constant (ε) materials with high mechanical strength and excellent thermal stability. In this work, poly(p-phenylene benzobisoxazole) (PBO) fibers are converted into PBO nanofibers (PNFs) via protonation–deprotonation, followed by in situ growth of ZIF-8 on PNFs through Zn2+ coordination. The resulting ZIF-PNF nanopaper is obtained by vacuum filtration and hot-pressing. Benefiting from the low polarizability and high porosity of ZIF-8, the ZIF-PNF nanopaper exhibits low ε (1.85) and dielectric loss tangent (tanδ, 0.032). The in situ growth approach effectively addressed the issues of ZIF-8 nanoparticle aggregation and poor interfacial compatibility with PNFs. The tensile strength and toughness of the ZIF-PNF nanopaper are 236.1 MPa and 17.6 MJ·m–3, 33.9% and 89.2% higher than those of the PNF nanopaper. In addition, the nanopaper exhibits outstanding thermal conductivity (1.9 W/(m·K)), high thermal stability (significant thermal degradation commencing at approximately 600 °C), and flame-retardant performance (UL-94 VTM-0). Owing to these remarkable properties, the nanopaper ensures the stability and security of signal transmission and equipment operation, which presents great promise for applications in integrated circuits, new energy vehicles, smart buildings, and electronic and electrical systems.