Nanoporous N-doped Carbon/ZnO hybrid derived from zinc aspartate: An acid-base bifunctional catalyst for efficient fixation of carbon dioxide into cyclic carbonates

Abstract

A nanoporous N-doped carbon/ZnO hybrid material (Zn-Asp-300) is facilely prepared by direct thermolysis of zinc aspartate precursor, which could be used as effective catalyst for the cycloaddition reaction of CO2 and epoxides in the presence of tetrabutylammonium bromide (TBAB) as co-catalyst. At temperature 80 °C and CO2 pressure 1.0 MPa, Zn-Asp-300 demonstrates good catalytic activity for various epoxides as substrates, gives up to 96.7% of yield and ca. 100% of selectivity. A variety of characterizations indicate that the resultant Zn-Asp-300 has abundant zinc oxide, as well as pyridinic and pyrrolic N atoms, which act as Lewis acid and basic sites that enable the activation of CO2 and epoxide, respectively, thus facilitating the cycloaddition reaction. Notably, the cycloaddition reaction also can be completed (92.2% of yield) on Zn-Asp-300 while only using simulated solar light as energy source. Moreover, Zn-Asp-300 also shows good chemical stability and reusability during the cycloaddition reaction. The potential application of Zn-Asp-300 in both thermal and photothermal catalysis of cycloaddition reaction is a promising and sustainable approach towards reducing CO2 emission and the utilization of CO2.