Reconstruction of Coal Gangue‐Derived Porous Carbon/Silica‐Alumina for Electromagnetic Wave Absorption

ABSTRACT High‐value utilization of industrial coal gangue (CG) solid waste presents formidable environmental and technical challenges, especially in tailoring charge transport to realize high‐performance electromagnetic wave (EMW) absorption whilst retaining its native structural and chemical attributes. Herein, we propose a carbon ash reconstruction strategy that confines nanoscale SiAl within porous carbon (PC) and tailors component contents to regulate charge behaviors, thereby achieving electromagnetic performance inversion. Specifically, alkali melting coupled with acid picking activates the inert SiAl phase, refining its particle size from 328.35 to 25.78 nm, and enabling homogeneous dispersion within PC while maintaining structural integrity. Furthermore, the dielectric discrepancy between PC and SiAl, together with gelation‐induced interface bridge‐oxygen bonding (C─O─Al and C─O─Si), enhances interfacial polarization and reduces electron migration barriers. Notably, reconstructed CG exhibits a remarkable performance inversion of microwave absorption capacity, expanding the effective absorption bandwidth (EAB) from 0 to 5.05 GHz at an ultrathin thickness of 1.5 mm. This work elucidates the reconstruction strategy roles in spatial confinement, interfacial chemistry, and electronic modulation in solid waste utilization, providing a theoretical foundation and scalable pathway for sustainable materials engineering.