A new two-dimensional (2D) carbon crystal, different from graphene, has been prepared from 1,3,5-trihydroxybenzene, consisting of 4-carbon and 6-carbon rings in 1:1 ratio, named 4-6 carbophene by authors, in which all carbon atoms possess sp 2 hybrid orbitals with some distortion, forming an extensive conjugated π-bonding planar structure. The angles between the three σ-bonds of the carbon sp 2 orbitals are roughly 120°, 90°, and 150°. Each of the three non-adjacent sides of a 6C-ring is shared with a 4C-ring; and each of the two opposite sides of a 4C-ring is shared with a 6C-ring. Dodecagonal holes with a diameter of approximate 5.8 Å are regularly located throughout the 2D carbon crystal. Even though the bond energies in 4-6 carbophene are weaker than those in the graphene, the new planar crystal is quite stable in ambient conditions. The 4-6 carbophene can be synthetized from 1,3,5-trihydroxybenzene or other benzene derivatives through dehydration and polymerization reactions, and may possess several possible patterns that form a family of 2D carbon crystals. A possible side reaction involving 1,3,5-trihydroxybenzene is also discussed, which may produce a carbon-oxygen two dimensional crystal.Graphene 1,2 is an allotrope of elemental carbon in the form of an atomic-scale, two-dimensional, honey-comb lattice, in which all carbon atoms are in sp 2 electron configuration, resulting in an extensive conjugated π -system. Graphene is the basic structural element of several other carbon allotropes, including graphite 3,4 , carbon nanotubes 5 and fullerenes (C 60 ) 6 . Graphene is an excellent material possessing many outstanding physical and chemical properties, such as high electrical and thermal conductivity 7 , huge specific surface area 8 , good optical transparency 2 , and excellent mechanical strength 9,10 . Therefore, graphene is expected to have many applications in broad areas 11,12 .From material science and structural chemistry viewpoints, graphene is a two-dimensional (2D) crystal and a 2D carbon material 13 . Since the first 2D carbon crystal graphene was found in 2004 1,2 , several other 2D crystals and materials of carbon have emerged 14,15 . In recent years the 2D crystals and materials become a booming research field. A comprehensive review on this field can be found in a review article by Peng et al. 16 . Chemically, a sheet of graphene is a large aromatic molecule consisting of hexagonal planar structural units 17,18 that are similar to anthracene and phenanthrene. In graphene, all carbon atoms are in standard sp 2 electronic configuration so that the angles between the three σ -bonds of carbon sp 2 orbitals are 120°, 120°, and 120°, just as they are in the carbon atoms in benzene and other aromatic molecules 19,20 .Actually, the orbitals in carbon atoms can also be in a distorted sp 2 hybrid form, resulting in planar structural units other than hexagons [21][22][23][24] . This possibility raises an interesting question: "Are there other two-dimensional carbon crystals that are different from gra...

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