Metal-free synthesis of dimethyl carbonate via transesterification of ethylene carbonate catalyzed by graphitic carbon nitride materials

Abstract

Catalytic transesterification reaction between a cyclic carbonate and a low alcohol is the most important and practical strategy for the manufacture of dimethyl carbonate and other alkyl carbonates. However, most developed heterogeneous catalysts have potential metal and halide contamination. Herein, a graphitic carbon nitride (g-C₃N₄) material has been synthesized, thermally exfoliated, and treated with an alkaline solution. The physicochemical properties of eg-C₃N₄ materials have been analyzed by XRD, TG, N₂ adsorption–desorption, FT-IR, UV-vis, and XPS spectroscopy. The characterization results reveal that the exfoliation has effectively enhanced the surface area of g-C₃N₄, and alkaline treatment could lead to the deprotonation of eg-C₃N₄, depending on the treatment temperature and alkaline solution. In the transesterification reaction between ethylene carbonate and CH₃OH, the eg-C₃N₄-NH₃ catalyst demonstrates superior catalytic activity to the pure g-C₃N₄, eg-C₃N₄ and eg-C₃N₄-HCl, affording a maximum DMC yield of 60% at 393 K. Furthermore, the eg-C₃N₄-NH₃ shows good catalytic reproducibility and versatility for other substrates.