Graphenylene, a unique two-dimensional carbon network with nondelocalized cyclohexatriene units

Abstract

Over many years chemists have established the general principle that two-dimensional chemical structures constructed with pure sp 2 carbon atoms will definitely form an aromatic system with delocalized electron density. However, based on a recently proposed chemical structure, graphenylene, this rule may finally be broken. Herein, we predict the properties of a new two-dimensional sp 2-carbon network known as graphenylene, which is the first example of non-delocalized sp 2-carbon structure composed of cyclohexatriene units with three quite distinct CC bonds within a C6 ring. In addition, theoretical calculations demonstrate that graphenylene has periodic pores of 3.2 Å in diameter and is a semiconductor with a narrow direct band gap, making it promising for various applications, such as electronic devices and efficient hydrogen separation. This study provides a new perspective on carbon allotropes, leading to a better understanding of [N]phenylene based organic frameworks, as well as clarifying the relationship between benzene and cyclohexatriene. Besides graphite and diamond, which have already been known for thousands years, the family of carbon allotropes has suddenly under gone a rapid expansion in recent decades, particularly with the addition of forms such as fullerenes 1 , carbon nanotubes 2 and graphene 3. With its unique chemical character, carbon can bind with itself or other elements to generate not only countless organic compounds, but also new carbon allotropes. The combination of sp-, sp 2-and sp 3hybridized carbon atoms leads to many possible carbon allotropes 4-6 with different dimensionalities 7-13. Of all of these experimentally obtained or theoretically predicted materials, the family of sp 2-carbon allotropes, which include fullerenes, nanotubes and graphene, is the most fascinating and has recently attracted considerable attention owing to their remarkable properties and potential applications in many emerging technologies. However, it is worth noting that fullerene, nanotubes and graphene all possess delocalized π-conjugated bonding such that they have relatively uniform bond lengths and electron distributions. Graphene can be considered as a building unit that can be wrapped up into fullerenes, rolled into carbon nanotubes or stacked into graphite 14. From a theoretical point of view, all of them are similar carbon networks with the same structural unit. One interesting and scientifically important question is whether sp 2-carbon can form alternative net

Theoretical investigation on electronic properties and carrier mobilities of armchair graphyne nanoribbons

“…The era of carbon allotropes [1] brings us many exciting properties, such as super-hardness and high performance in field effect transistors. Beyond these wellknown allotropes, many other carbon forms, especially for two-dimensional sheets, are predicted [2][3][4][5], such as graphynes (GYs) [6] and graphdiynes (GDYs) [7]. The rich geometrical variety makes carbon a promising material for various potential applications.…”

Band gap engineering of graphenylene by hydrogenation and halogenation: a density functional theory study

“…Seen from Fig. 24 The PBE band structures of hydrogenated graphenylenes at different hydrogen concentrations are presented along the high symmetry lines of the Brillouin zone in Fig. For example, the calculated binding energies are À0.45, À2.21, À0.50 and À0.18 eV per atom for H, F, Cl and Br, respectively, at x ¼ 0.17.…”

Expanded Carbon Lattices and Congener Hydrocarbons with directionally Inserted Triple Bonds

“…The regular polygonal angles are 90°, 120°, and 150°, respectively, adding up to 360°; however, it was expected that the energy factor of aromaticity/antiaromaticity would cause deviations from regularity, and indeed all the 4-membered rings avoid antiaromaticity by having exocyclic double bonds, despite the fact that the bonds in the 6-membered rings become unequal, namely alternatively shorter and longer than the benzene CC bonds, as shown by Müllen and coworkers [39].…”