Quaternary ammonium salt functionalized copper phthalocyanine-graphene oxide hybrids for cocatalyst-free carbon dioxide cycloaddition

Abstract

Chemical conversion of carbon dioxide (CO₂) into high-value products not only enhances environmental sustainability but also presents economic benefits. The development of novel and effective catalysts is crucial for facilitating the conversion of CO₂ and the synthesis of these chemicals. In this study, we present the preparation of an ionic liquid-functionalized graphene oxide and copper phthalocyanine (CuPc) hybrid (GO-CuPc-IL). This was achieved through the chemical grafting of phthalonitrile groups and quaternary ammonium salts onto graphene oxide (GO), followed by in situ polymerization with phloroglucinol triphenyldinitrile. This hybrid catalyst was employed to catalyze the cycloaddition reaction of CO₂ with epoxides under mild conditions. A series of analytical techniques confirmed the successful synthesis of the GO-CuPc-IL. The presence of abundant hydrogen bond donor groups (urea groups), Lewis acidic sites (coordinated copper rings), phthalocyanine rings, and numerous ionic active sites within the GO-CuPc-IL significantly facilitated the activation of reactants, enabling an efficient cycloaddition reaction of CO₂ and epoxides. Notably, with 3.0 wt% of GO-CuPc-IL, the reaction achieved a yield of 98% and a selectivity of 99% at 1.5 MPa CO₂ and 100 °C for 8 h, along with remarkable stability and reusability. This innovative hybrid catalyst promotes the simultaneous adsorption and activation of CO₂ and epoxide by immobilizing multiple functional groups on the catalyst support, providing new avenues for sustainable CO₂ conversion.