Metal halides supported on mesoporous carbon nitride as efficient heterogeneous catalysts for the cycloaddition of CO2

• Metal halides were supported on mp-C3N4 supports via simple impregnation methods.
• Metal halide was essentially active sites to activate propylene oxide molecule.
• Various supported metal halides showed high performances in cycloaddition of CO2.

A series of ZnCl2/mp-C3N4 catalysts were prepared through a wet impregnation method using mesoporous g-C3N4 materials as catalytic supports. The physicochemical properties of the ZnCl2/mp-C3N4 catalysts were characterized using several techniques, including N2 adsorption–desorption, X-ray diffraction, Fourier transform infrared, UV–vis diffuse reflectance, and X-ray photoelectron spectroscopy. In the cycloaddition reactions of CO2 with propylene oxide (PO) to propylene carbonate (PC), the ZnCl2/mp-C3N4 materials revealed high catalytic performances at 140 °C and 6 h. Furthermore, other metal halides including ZnBr2, CoCl2, FeCl3, NiCl2, and MgCl2 catalysts supported on mp-C3N4 were fabricated and the synthesized catalysts also demonstrated high performances in the catalytic cycloaddition of CO2. A possible catalytic mechanism has been proposed. The mp-C3N4 material served mainly as a basic support to adsorb CO2 whereas the supported metal halides were active sites to promote the activation of PO and realize its transform into PC.

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