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...

Graphene microcrystal (GMC) is a type of glassy carbon fabricated from lignin, in which the microcrystals of graphene are chemically bonded by sp3 carbon atoms, forming a glass-like microcrystal structure. The lignin is refined from sugarcane bagasse using an ethanol-based organosolv technique which is used for the fabrication of GMC by two technical schemes: The pyrolysis reaction of lignin in a tubular furnace at atmospheric pressure; and the hydrothermal carbonization (HTC) of lignin at lower temperature, followed by pyrolysis at higher temperature. The existence of graphene nanofragments in GMC is proven by Raman spectra and XRD patterns; the ratio of sp2 carbon atoms to sp3 carbon atoms is demonstrated by XPS spectra; and the microcrystal structure is observed in the high-resolution transmission electron microscope (HRTEM) images. Temperature and pressure have an important impact on the quality of GMC samples. With the elevation of temperature, the fraction of carbon increases, while the fraction of oxygen decreases, and the ratio of sp2 to sp3 carbon atoms increases. In contrast to the pyrolysis techniques, the HTC technique needs lower temperatures because of the high vapor pressure of water. In general, with the help of biorefinery, the biomass material, lignin, is found to be qualified and sustainable material for the manufacture of GMC. Lignin acts as a renewable substitute for the traditional raw materials of glassy carbon, copolymer resins of phenol formaldehyde, and furfuryl alcohol-phenol.

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Sugarcane bagasse was refined into cellulose, hemicellulose, and lignin using an ethanol-based organosolv technique. The hydrothermal carbonization (HTC) reactions were applied for bagasse and its two components cellulose and lignin. Based on GC-MS analysis, 32 (13+19) organic byproducts were derived from cellulose and lignin, more than the 22 byproducts from bagasse. Particularly, more valuable catechol products were obtained from lignin with 56.8% share in the total GC-MS integral area, much higher than the 2.263% share in the GC-MS integral areas of bagasse. The organic byproducts from lignin make up more than half of the total mass of lignin, indicating that lignin is a chemical treasure storage. In general, bio-refinery and HTC are two effective techniques for the valorization of bagasse and other biomass materials from agriculture and forest industry. HTC could convert the inferior biomass to superior biofuel with higher energy quantity of combustion, at the same time many valuable organic byproducts are produced. Bio-refinery could promote the HTC reaction of biomass more effective. With the help of bio-refinery and HTC, bagasse and other biomass materials are not only the sustainable energy resource, but also the renewable and environment friendly chemical materials, the best alternatives for petroleum, coal and natural gas.