Fullerene-derived hierarchical sp² carbon exhibiting united hardness, elasticity, and thermal stability

Carbon materials possess attractive mechanical and thermal properties, yet creating bulk sp²-bonded carbon that unites high hardness, elastic recoverability, and thermal stability has remained elusive. Mechanical anisotropy, low damage tolerance, and structural instability under stress or at high temperatures hinder the development of dense sp²-carbon architectures for demanding environments. Here we report a dual-phase sp² carbon produced from C₆₀ at high pressure through progressive structural reconstruction, yielding a hierarchical structure in which stacked graphene nanoclusters are integrated within a disordered sp²-rich amorphous matrix. This architecture accommodates stress by structurally mediated interlayer sliding and elastic compaction, while retaining structural coherence. The resulting material achieves ~ 20 GPa hardness, > 88% elastic recovery, and oxidation resistance near 960 °C in air, representing an unusual combination of mechanical recoverability and thermal stability among representative carbon materials. Simulations show that the combination of stiffness and resilience arises from interfacial reinforcement between the ordered and disordered domains. This work identifies a structural pathway for engineering sp²-carbon systems that overcome long-standing limits in mechanical and thermal performance.