Comprehensive insight into the support effect of graphitic carbon nitride for zinc halides on the catalytic transformation of CO2 into cyclic carbonates

Article abstract of DOI:10.1039/c8cy01688g

Chemical fixation of CO₂ to high-valued chemicals is currently a significant research topic in both the environment and chemistry, and cycloaddition of CO₂ with epoxides is regarded as a sustainable route for the manufacture of cyclic carbonates. Homogeneous catalysts including ionic liquids and organic metal complexes suffer from difficulty in catalyst-product separation despite their excellent catalytic activities. In this work, we utilized graphitic carbon nitride (g-C₃N₄) as a novel support to immobilize zinc halides (ZnX₂) through a simple preparation method. Based on the detailed design of the synthesis of ZnX₂/g-C₃N₄, the chemical bonding information of ZnX₂ on g-C₃N₄ was comprehensively investigated by XPS and FT-IR techniques. In addition to activation of CO₂, g-C₃N₄ can anchor zinc halides via interaction between zinc and nitrogen, thereby effectively alleviating potential leaching of zinc halides. As heterogeneous catalysts, ZnX₂/g-C₃N₄ materials showed good catalytic activities in the cycloaddition reactions of CO₂ with propylene oxide. Furthermore, a wide range of epoxides can be converted to the corresponding cyclic carbonate with good selectivities (>93%) and moderate conversions (50-88%).