Enhanced selective oxidation of ethylarenes using iron single atom catalysts embedded in Nitrogen-Rich graphene

Abstract

Heavily (19 % wt) Nitrogen doped graphene (N-G), with Nitrogen incorporated mainly as pyridinic species (77.8 %), was obtained by reacting fluorographene with ammonia under solvothermal conditions, at mild temperature (140 °C). N-G was used to stabilize single iron atoms (N-G-Fe) in two different configurations: low spin X-(Fe^IIN₄)-Y and high spin X-(Fe^IIIN₄)-Y. The resulting N-G-Fe single atom catalysts exhibit remarkable efficacy in the selective oxidation of ethylarenes, with activity comparable or even superior to state-of-the-art materials, converting ethylbenzene to acetophenone with an initial turnover frequency of 13400 h⁻¹. Notably, N-G-Fe exhibits genuine catalytic activity since it is able to oxidize ethylbenzene using substoichiometric amount of peroxides, and exploiting molecular oxygen as the final oxidant. Moreover, N-G-Fe can be recycled without any metal leaching, and exhibits a broad catalytic scope. Multi-technique characterizations combined with rationally designed catalytic tests allowed us to identify the active sites and propose a plausible mechanism for the catalytic cycle