Heterostructured BN@Co-C@C Endowing Polyester Composites Excellent Thermal Conductivity and Microwave Absorption at C Band

The trends of miniaturization, lightweight, and high integration in electronics have brought serious issues in heat dissipation and electromagnetic compatibility and also limited the simultaneous use of thermally conductive and microwave absorption materials. Therefore, it is imperative to design materials that possess those dual functions. In this work, one-pot method is used to anchor zeolitic imidazolate framework ZIF-67 coated with polydopamine (PDA) on boron nitride (BN) to obtain BN@ZIF-67@PDA. The pyrolysis product BN@Co-C@C is used as heterostructured thermally conductive/microwave absorption fillers and blended with polyethylene terephthalate (PET) to prepare BN@Co-C@C/PET composites. When the mass ratio of BN to ZIF-67@PDA is 7.5:1 and the mass fraction of BN_7.5@Co-C@C is 45 wt%, the BN_7.5@Co-C@C/PET composites exhibit excellent thermal conductivities and microwave absorption performances. The thermal conductivity coefficient is 5.37 W m⁻¹ K⁻¹, which is 35.8 times higher than that of PET (0.15 W m⁻¹ K⁻¹), and also higher than that of 45 wt% (BN_7.5/Co-C@C)/PET composites (4.03 W m⁻¹ K⁻¹) prepared by directly mixing. The minimum reflection loss of 45 wt% BN_7.5@Co-C@C/PET composites are −63.1 dB at 4.72 GHz, and the corresponding effective absorption bandwidth is 1.28 GHz (4.08–5.36 GHz), achieving excellent microwave absorption performance at C band.