Metal-free catalytic conversion of CO2 into cyclic carbonate by hydroxyl-functionalized graphitic carbon nitride materials

Graphitic carbon nitride (g-C3N4) contains abundant nitrogen-containing groups and have demonstrated potential catalysis in several CO2-activating reactions. However, the catalytic activity obtained with the bulk and pristine g-C3N4 is quite low. In this work, g-C3N4 was prepared using dicyandiamide as a precursor, thermally exfoliated, and then treated by HCl solution. The synthesized eg-C3N4−OH were analyzed by various characterization techniques including XRD, N2 adsorption, SEM, FT-IR, UV–vis, XPS, and Raman spectroscopy. The characterization results confirmed that the treatment of HCl induced the generation of hydroxyl groups on the surface of eg-C3N4, depending on the treatment conditions. As metal-free catalysts, the eg-C3N4 materials exhibit high catalytic activities in the cycloaddition reactions of CO2. The effects of HCl treatment on the chemical properties of eg-C3N4 materials and the corresponding catalytic performance have been investigated. Furthermore, the catalytic performance of eg-C3N4−OH was compared with other previously reported g-C3N4-based materials.