Printable Architected Porous Ceramic Metamaterials Enabling Electromagnetic‐Thermal Coupling

ABSTRACT The coupled demands for electromagnetic interference mitigation and thermal management in aerospace and advanced electronic systems necessitate lightweight materials that integrate broadband microwave absorption with effective thermal insulation under extreme operating conditions. Conventional electromagnetic absorbers and thermal barriers are typically monofunctional, whereas metamaterials, despite their architectural versatility, often exhibit limited thermal protection. Here we introduce a printable porous Silicon‐Boron Oxycarbide (SiBOC) ceramic metamaterial that combines structural precision, multifunctionality, and high‐temperature resilience. By dispersing hollow glass microspheres (HGMs) into a UV‐curable SiBOC pre‐ceramic polymer, we achieve a resin system that simultaneously supports high loading, porosity, and digital light processing printability. During heat treatment, HGMs act as both structural stabilizers and catalytic reservoirs, yielding a hierarchical SiBOC@Graphene@HGM architecture. This unique configuration enhances dielectric loss, promotes multi‐scattering, and suppresses heat conduction. Consequently, the porous SiBOC ceramic metamaterial achieves an ultrabroad effective absorption bandwidth of 35.58 GHz (within 2–40 GHz, at the incident angle of 50°) with a minimum reflection loss of −59.71 dB, along with low thermal conductivity (0.208 W·m −1 ·K −1 ) and light density (0.313 g cm −3 ). This strategy establishes a generalizable paradigm for multifunctional ceramic metamaterials, bridging electromagnetic and thermal protection for next‐generation extreme‐environment applications.