Constructing High-Strength Three-Dimensional Carbon Solids via Single-Atom π-Metal-π Nanoadhesives.

The fabrication of bulk carbon materials from low-dimensional π-conjugated units remains limited by a central challenge: fragmented components, such as graphene flakes and carbon nanotube segments, are difficult to assemble into cohesive and mechanically reliable solids. Here we introduce a general molecular-level bonding motif, the π-metal-π linkage, in which transition-metal atoms act as single-atom adhesives that convert originally weak van der Waals contacts between π surfaces into robust covalent connections. This approach provides a unified strategy for assembling diverse discrete π systems into continuous three-dimensional lightweight carbon architectures while preserving the excellent in-plane stiffness characteristic of sp2 carbon frameworks. First-principles calculations show that metal-bridged graphene structures exhibit substantially enhanced interlayer strength and form stable carbon solids with improved mechanical integrity. The π-metal-π nanoadhesive concept thus offers a versatile route for constructing high-strength carbon materials from otherwise disconnected molecular fragments and opens new opportunities for carbon-based structural design.