Paired Electrochemical N–N Coupling Employing a Surface-Hydroxylated Ni₃Fe-MOF-OH Bifunctional Electrocatalyst with Enhanced Adsorption of Nitroarenes and Anilines

Abstract

Paired electrolysis employing both anodic and cathodic half reactions for the synthesis of value-added chemicals is an ultimate energy-efficient approach. Here, we show that paired reductive coupling of nitroaromatics into azoxy-aromatics and oxidative coupling of aromatic amines into azo-aromatics can be realized with high efficiency and selectivity employing the surface-hydroxylated Ni3Fe metal–organic framework (Ni3Fe-MOF-OH) bifunctional electrocatalyst. The competitive hydrogen and oxygen evolution reactions are suppressed due to the adsorption of nitroarenes and anilines via surface hydroxyls of the electrocatalyst. Simultaneous cathodic and anodic N–N coupling of a wide range of nitroaromatics and aniline derivatives are realized with high conversion and selectivity at an overall bias of 1.4 V in an undivided cell in 1 M KOH electrolyte. Ni3Fe-MOF-OH displays a high stability and enables gram-scale synthesis of azo- and azoxy-aromatics with a satisfactory yield and Faraday efficiency, offering an efficient synthetic protocol for applications.