Abstract: The catalytic hydrogenation of sulfur-containing nitroaromatic hydrocarbons to their corresponding amino compounds is a crucial reaction for achieving green transformation in pharmaceutical intermediates. However, the strong coordination of sulfur atoms poisons transition metal hydrogenation catalysts, suppressing their catalytic activity. Herein, we selected intrinsically sulfur-resistant MoS2 as the catalyst and modulated its sulfidation behavior by replacing ammonium ions in molybdate precursors with quaternary ammonium cations of varying organic chain lengths to synthesize corresponding MoS2 catalysts. Electron paramagnetic resonance (EPR) and O2 titration in situ infrared (IR) characterization revealed that edge sulfur vacancies in MoS2 increased with the elongation of quaternary ammonium salt carbon chains. In the hydrogenation of the model substrate 5-nitrobenzothiazole (NBZ), the catalyst’s activity is closely related with edge S vacancies. The optimized catalyst outperformed the currently reported Co-Mo-S catalysts. In a fixed-bed continuous flow reactor under 80 oC，3 bar, the catalyst achieved a conversion efficiency of 49 mgNBZ·gcat-1·h-1, surpassing the performance of the supported noble metal catalyst Pt/TiO2 under identical conditions. This study demonstrates that long-chain organic quaternary ammonium cations significantly enhance edge S vacancies in MoS2, highlighting their potential application value in hydrogenating sulfur-containing nitroaromatic compounds.

Key words: MoS₂, Quaternary ammonium cation, S vacancies, Sulfur-Containing nitroarene, Catalytic hydrogenation