Abstract: The development of high-performance microwave-absorbing materials with integrated thermal management capabilities is critical for advanced electronic and communication systems. In this study, we synthesized hollow core–shell structured composites through controlled pyrolysis of zeolite imidazolate framework (ZIFs). Structural and compositional characterizations confirm the successful formation of highly graphitized carbon frameworks embedded with metallic nanoparticles (Co or Zn) and a protective mesoporous SiO₂ shell. The as-prepared Zn–C@SiO₂ exhibits a minimum reflection loss (RL_min) of −23.77 dB with an effective absorption bandwidth (EAB) of 6.24 GHz at 2.0 mm thickness, while Co–C@SiO₂ demonstrates superior microwave absorption (RL_min = −51.9 dB, EAB = 5.36 GHz). The enhanced dielectric loss attributed to the interfacial polarization effects was systematically investigated. Additionally, the composites exhibit rapid thermal response, highlighting their dual functionality as microwave absorbers and thermal management materials.