Urea-derived graphitic carbon nitride as an efficient heterogeneous catalyst for CO₂ conversion into cyclic carbonates

In order to overcome existing solid catalysts' disadvantages of low stability and activity, urea-derived graphitic carbon nitrides (u-g-C ₃N₄) with higher stabilities and more active centers were prepared under different temperatures (550-450°C). With a decrease in preparation temperature from 550°C to 480°C, a u-g-C₃N ₄ of lower crystallinity with a smaller polymerization degree was obtained and found to have a higher catalytic activity for CO₂ conversion into propylene carbonate. The higher activity of the u-g-C ₃N₄ caused by decreasing the temperature might be ascribed to the lower crystallinity and polymerization degree, which led to more edge defects, wherein the incompletely-coordinated nitrogen atoms served as the main active sites in the cycloaddition reaction. Among all the prepared catalysts, that prepared at 480°C (u-g-C₃N₄-480) showed the highest catalytic activity for CO₂ conversion and exhibited great suitability for other epoxide substrates. This journal is