Multi‐Metal Phenolic Network Engineered Low Density Polymeric Ablator for Thermal Protection and Insulation up to 2900K

Planetary‐entry and sample‐return missions demand thermal protection materials that simultaneously minimize mass, suppress recession, and withstand prolonged exposure to ultrahigh‐temperature oxidative environments. Here, we report a metal‐phenolic‐network (MPN) engineered low‐density‐ablator that resolves this longstanding trade‐off through molecularly programmable multimetal ceramization. The material is constructed by controlled ligand exchange between a quasi‐linear Ti/Zr/Hf multimetal polymer and phenolic ligands, followed by polymerization into a nanoporous aerogel‐like‐matrix with low density, low thermal conductivity, and scalable processability. The molecular‐level dispersion of multimetal species governs the in situ evolution of hierarchical ceramic architectures during extreme heating: the surface transforms into a dense interpenetrating oxide protection layer, in which (Hf, Zr)O form a rigid skeleton while (Ti, Si)O fill the intergranular space to suppress oxygen penetration and outward mass transport; meanwhile, the interior develops a mass‐fractal carbon–ceramic network that disrupts heat‐flux propagation. The composite exhibits near‐zero recession at ultrahigh temperatures, with linear ablation rates of 0.0017 mm s −1 at 2800 K and 0.0031 mm s −1 at 2900 K, while sustaining 2500 K for 1500 s with a back‐temperature‐rise of only 369 K. This work establishes an MPN‐based materials platform for lightweight thermal protection systems that integrate ultrahigh‐temperature stability, oxidation resistance, and effective thermal insulation.