Coal tar pitch-based hyper-crosslinked polymers derived porous carbon for electromagnetic wave absorption

Porous carbon (PC) materials have unique structures and excellent physicochemical properties, which offer significant advantages in the field of electromagnetic wave (EMW) absorption materials. However, how to utilize available raw materials and practical preparation techniques is a major challenge for PC microwave absorption materials to achieve engineering applications. In this study, inexpensive coal tar pitch (CTP) was used as a carbon source to prepare PC microwave absorbers. Firstly, hyper-crosslinked polymers (HCPs) were prepared by selectively crosslinking the aromatic components in CTP via Friedel-Crafts reaction using chloroalkanes as crosslinking agents. Further, PC materials with uniform structure were also prepared by simple high-temperature carbonization. The effects of cross-linker type (CH₂Cl₂, CHCl₃ and CCl₄) and carbonization temperature (600°C, 700°C and 800°C) on the microstructure, crystallization, dielectric and microwave absorption properties of PC materials were systematically studied. After modulation and optimization, all CTP-based PCs have uniform pore structure with a maximum specific surface area of 533.93 m²/g. The PC with CHCl₃ as cross-linking agent carbonized at 700°C showed the exceptional microwave absorption performance, with the minimum refection loss (RL_min) of −43.08 dB and the maximum effective absorption bandwidth (EAB_max) of 5.44 GHz. Meanwhile, the RL_min of CCl₄-PC-800 also achieved −47.28 dB. This work has developed a simple and low-cost method for preparing PC microwave absorption materials, which has the potential to enable the mass production and engineering application of PCs, as well as facilitating processing technology innovation and high value-added utilization of CTP.