Space-Confined Synthesis of Monolayer Graphdiyne in MXene Interlayer

Graphdiyne (GDY) is an artificial carbon allotrope that is conceptually similar to graphene but composed of sp- and sp2-hybridized carbon atoms. Monolayer GDY (ML-GDY) is predicted to be an ideal 2D semiconductor material with a wide range of applications. However, its synthesis has posed a significant challenge, leading to difficulties in experimentally validating theoretical properties. Here, it is reported that in situ acetylenic homocoupling of hexaethynylbenzene within the sub-nanometer interlayer space of MXene can effectively prevent out-of-plane growth or vertical stacking of the material, resulting in ML-GDY with in-plane periodicity. The subsequent exfoliation process successfully yields free-standing GDY monolayers with micrometer-scale lateral dimensions. The fabrication of field-effect transistor on free-standing ML-GDY makes the first measurement of its electronic properties possible. The measured electrical conductivity (5.1 x 103 S m-1) and carrier mobility (231.4 cm2 V-1 s-1) at room temperature are remarkably higher than those of the previously reported multilayer GDY materials. The space-confined synthesis using layered crystals as templates provides a new strategy for preparing 2D materials with precisely controlled layer numbers and long-range structural order. Monolayer graphdiyne is synthesized by in situ acetylenic homocoupling of hexaethynylbenzene within the sub-nanometer interlayer space of Mxene. Free-standing monolayer graphdiyne flakes with micrometer-scale lateral are exfoliated from MXene interlayer assisted with ion intercalation. The free-standing monolayer graphdiyne presents excellent electronic properties which are superior to various previously reported multilayer graphdiyne materials.image