3D carbon crystals: theoretical prediction and experimental preparation.

Sp, sp ² or sp ³ hybridization of carbon atoms results in a linear, triangular or tetrahedral configuration of bonding geometry, respectively. By combining different hybridizations in one structure, a variety of 3D carbon allotropes with periodic crystal structures can be obtained with potential novel properties and applications. With the rapid development of computational capability in recent years, a large number of new 3D carbon structures have been proposed with their properties predicted; the development of new experimental techniques has also led to the successful experimental preparation of several carbon crystals. Observing the rapid advancement of 3D carbons subsequent to the breakthroughs in 2D graphene, this paper reviews the recent progress in constructing carbon crystals by summarizing the structural design and specifically highlighting the preparation using template carbonization, organic synthesis, high-pressure processing and charge injection.