Cobalt-cobalt oxide doped lignin-based carbon materials for microwave absorption via microwave carbonization

With the escalating concerns over environmental pollution, effective management of industrial waste has emerged as a critical research focus in modern materials science. In this study, we developed cobalt-cobalt oxide doped lignin-based porous carbon materials (Co@CoO@MPC) by employing zeolitic imidazolate framework-67 (ZIF-67) decorated with industrial black powder—a byproduct rich in lignin and carbon. The synthesis involved potassium hydroxide (KOH)-assisted microwave activation, which enabled the creation of a porous structure, thereby markedly increasing the specific surface area and interfacial properties of the composites. During pyrolysis, ZIF-67 underwent transformation into cobalt (Co) and cobalt oxide (CoO) phases. The synergistic interaction between Co/CoO and the porous carbon significantly enhanced microwave absorption through both dielectric and magnetic loss mechanisms. The Co@CoO@MPC composites demonstrated exceptional microwave absorption properties across a broad frequency range, particularly at higher frequencies. Specifically, the sample after 2-min microwave irradiation exhibits a high EAB value of 5.7 GHz (1.6 mm thickness)  and an RL_min value of -30 dB (2.0 mm thickness). This research not only offers an innovative approach to recovering resources from industrial black powder but also provides groundbreaking strategies for developing high-performance microwave-absorbing materials.