Fluorine-Mediated Carbon Doping in Boron Nitride: Atomic-Level Interface Engineering for Balancing Microwave Absorption and Thermal Management.

The advancement of high-density integrated electronics urgently demands materials that integrate efficient thermal management and microwave absorption. However, conventional design strategies that often rely on materials with multi-component composites face a trade-off between these properties, and a lack of microwave absorption effectiveness study in the polymer matrix. Herein, a fluorine-mediated carbon doping in boron nitride (C-F-BN) is designed to achieve atomic-level interface engineering. Fluoride induces the formation of polarized C─F bonds and promotes ordered sp2-carbon incorporation, which well preserves the BN lattice integrity while establishing strong polarization sites. The resulting C-F-BN shows exceptional microwave absorption with a reflection loss of -43 dB at 2 mm thickness, compared to that of only carbon doping in BN, achieving an effective absorption bandwidth of 3.52 GHz and a remarkable absorption efficiency index of 35 dB· GHz mm-1. The maintained BN crystallinity, ordered sp2-carbon conversion, and enhanced interfacial compatibility between C-F-BN and polyvinyl alcohol (PVA) enable PVA/C-F-BN composites to attain higher through-plane thermal conductivity (0.2599 W·m-1·K-1) at a lower filler loading (5 wt.%). Moreover, the composite exhibits a broader absorption bandwidth of 3.84 GHz with a reflection loss of -32 dB. The design concept offers a feasible route to multifunctional materials for advanced electronic packaging.