Samples of graphitic carbon nitride g-C3N4 have been synthesized by thermal annealing of urea in air at temperatures of 450–600°C. The investigation results of the relationship between the structural and morphological features of the material and the parameters of its intrinsic luminescence have been presented. The found dependences for characteristics of photonic emission on the excitation methods and synthesis modes of thermally polymerized g-C3N4 structures have been discussed.