Highly selective electrosynthesis of imines via electroreduction coupling of nitroarenes with aryl aldehydes on Co9S8 with positively charged sulfur vacancies

Abstract

The electrocatalytic synthesis of imines through the reductive imination of nitroarenes with aldehydes is a facile, environmentally friendly, and valuable process. In this study, high selectivity electrosynthesis of imines was realized through the electrocatalytic C-N coupling reaction between nitroarenes and aryl aldehydes on Co₉S₈ nanoflowers with rich sulfur vacancies (Co₉S₈-V_s). Comparative experiments revealed that positively charged sulfur vacancies play a pivotal role in boosting catalytic selectivity towards imines. Electron-deficient sulfur vacancies intensified the adsorption of negatively charged Ph-NO₂, thereby enhancing the conversion rate of the electrochemical nitrobenzene-reduction reaction (eNB-RR). Simultaneously, sulfur vacancies augmented the adsorption capability of negatively charged Ph-CHO, enriching Ph-CHO species at the electrode interface and expediting the Schiff base condensation reaction rate. The experimental results show that the reaction conditions can satisfy the different nitroarenes and aryl aldehydes in the electrocatalytic aqueous-phase system under mild conditions to obtain the corresponding imine products in high selectivity. This study provides a facile and environmentally friendly pathway for future electrocatalytic synthesis of imine.