From urea to melamine cyanurate: Study of a class of thermal condensation routes for the preparation of graphitic carbon nitride

This work presents a survey of the intermediates in the well-known thermal synthesis of graphitic carbon nitride from urea. The analysis of the crystalline phases depicts a successive transformation of the precursor into different substances previously used as starting reactants, whereby melamine cyanurate arises as the ultimate precursor of a class of thermal condensation routes to obtain graphitic carbon nitride. The study of the optical properties of the synthesized materials evidences the simultaneous production of an amorphous phase with a significant presence of melon oligomers. These results are also supported by the further characterization of the materials performed using THz-TDS, FTIR, HRTEM, and XPS techniques, and by theoretical studies conducted using semi-empirical quantum chemistry methods.