Photocatalytic activation and utilization of CO2 for N-formylation of amines promoted by a zinc(ii) phthalocyanine grafted on g-carbon nitride hybrid

Abstract

The utilization of CO₂ as a sustainable C₁ feedstock to produce fine chemicals is an important and viable approach for CO₂ mitigation. However, the high thermodynamic stability and chemical inertness of CO₂ make its activation tedious and require extensive energy inputs. In the present study, we described a visible light-assisted, highly efficient, and cost-effective approach for the N-formylation of various amines with CO₂ in the presence of phenyl silane at atmospheric pressure using a hybrid photocatalyst consisting of zinc phthalocyanine (ZP) embedded in graphitic carbon nitride (g-C₃N₄). Among the various compositions screened, a hybrid containing 5 wt% ZP on g-C₃N₄ (ZPCN-5) exhibited the maximum efficiency for this transformation. The computational studies and DFT calculations suggested the mode of CO₂ activation and formation of formamide at the surface. These calculations suggested that the work function of ZP was lower than that of CN, which led to an electron flow from ZP to CN and thus confirmed the type II configuration of ZPCN. The developed photocatalyst was highly stable and remained active for at least five runs without any significant loss in efficiency, and no leaching was observed during this course.