Benzene thermal synthesis and characterization of crystalline carbon nitride

A new solvothermal route has been successfully used to prepare crystalline carbon nitride powder from 1,3,5-trichlorotriazine (C₃N ₃Cl₃) and lithium nitride (Li₃N) in benzene at 360°C and 6-7 MPa. The as-prepared sample was brown and was analyzed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The results show that the powder mainly consists of α-C₃N₄, β-C ₃N₄ and some unidentified carbon-nitrogen crystalline phases. The experimental lattice constants of α-C₃N₄ (a = 6.48 Å, c = 4.72 Å) and β-C₃N₄ (a = 6.43 Å, c = 2.47 Å) match the latest ab-initio calculations (a = 6.47 Å and c = 4.72 Å for α-C₃N₄, a = 6.40 Å and c = 2.40 Å for β-C₃N₄) quite well. The relative nitrogen-to-carbon composition ratio is 0.76. Only C-N and C=N bonds were demonstrated by XPS and FTIR. The feasibility of this synthetic method is discussed and this approach may provide a possible and very effective way to realize the growth of pure crystalline carbon nitride materials, which is quite different from the conventional solid-state reactions (SSR).