Engineering the activity and stability of ZIF-8(Zn/Co)@g-C3N4 nanocomposites and their synergistic action in converting atmospheric CO2 into cyclic carbonates

The development of novel catalytic materials that integrate multifunctional sites has significant implications for expanding the utilization of CO2 resources. However, simultaneously achieving high activity and stability remains a formidable challenge. In this study, a series of ZIF-8(Zn/Co)@g-C3N4 nanocomposites were prepared by employing a thermo-physical compounding strategy that involved the combination of nitrogen-rich graphitic carbon nitride (g-C3N4) nanosheets with ZIF-8(ZnCo). The influences of different compositions of g-C3N4 and ZIF-8(Zn/Co) on the catalyst structure were systematically investigated. Subsequently, the catalytic activities of these nanocomposites towards the cycloaddition reaction between CO2 and epoxide were examined under different conditions. The presence of abundant Lewis base sites in g-C3N4 facilitates CO2 activation, while multiple Lewis acid sites in ZIF-8(Zn/Co) enable efficient epoxide activation. By working synergistically with a co-catalyst, tetrabutylammonium bromide (TBAB), CO2 and epoxides can be efficiently reacted to synthesize the corresponding cyclic carbonates under mild or even atmospheric pressure conditions. The catalytic reaction conditions were optimized, and both the catalyst's recycling performance and the scope of epoxides with various substituents were investigated. The integration of g-C3N4 and ZIF-8(Zn/Co) endows the catalytic material with exceptional structural stability and remarkable catalytic activity, thereby providing a new platform for highly efficient CO2 conversion.