A Fe single atom on N,S-doped carbon catalyst for performing N-alkylation of aromatic amines under solvent-free conditions

Abstract

A green and gram-scale strategy has been developed for the synthesis of Fe single atom/N,S-doped carbon catalyst (Fe₂₀-SA@NSC) via the pyrolysis of polyaniline (PAN)-modified Fe,S-doped ZIFs, in which the synthesis of ZIFs can be accomplished in water at room temperature. The as-prepared catalyst exhibits superior activity in the N-alkylation of amines with alcohols via a borrowing strategy under solvent-free conditions (TOF up to 13.9 h⁻¹). Based on the HAADF-STEM and XAFS results, Fe in this material is dispersed as the single-atom Fe₁–N₄S₁ site. According to the experimental and theoretical calculation results, the Fe₁–N₄S₁ site displays a better borrowing hydrogen ability than other Fe sites owing to its higher electron density. In addition, this catalyst has excellent stability and recyclability, and no obvious loss in activity is observed after 7 runs.