A Keggin-based hybrid solid emerged as a promising candidate for CO2-mediated photocatalytic N-formylation of amines

Abstract

Polyoxometalates (POMs) possess unique redox properties, making them effective catalysts for various chemical transformations. Typically, in the N-formylation reaction, POMs can facilitate the conversion of CO₂ and amines into formamide derivatives by activating the CO₂ molecule and promoting its reaction with the amine substrate. POMs, exhibiting photocatalytic activity, can initiate and accelerate chemical reactions under light irradiation. This property is particularly beneficial in the context of CO₂ utilization. The combination of catalytic activity, photocatalytic properties, structural diversity and redox activity makes them promising candidates for catalysing the N-formylation of amines using CO₂. Herein, we present two novel Keggin cluster based solids, (C₅H₇N₂)₅[CoW₁₂O₄₀] (PS-96) and (C₅H₇N₂)₅[CuW₁₂O₄₀] (PS-97), of which PS-97 was active for efficient and photocatalytic N-formylation of various substituted anilines and morpholine with CO₂ using phenyl silane as a reducing agent, under ambient conditions. Out of the array of amines tested, p-toluidine demonstrated the best conversion and yield of 83% and 96%, respectively. PS-97 exhibited robust recyclability, maintaining catalytic activity across 5 successive cycles without notable degradation.