Construction of metal-organic tetrahedral cage for boosting selective electrocatalytic reduction of nitrite to ammonium

Abstract

Electrocatalytic reduction of nitrite to ammonium (NO2RR) presents a promising approach for removing harmful NO2- and efficiently synthesizing ammonium but still faces with difficulties, due to the complex six-electron transfer reaction involving various by-products and the hindered by competing hydrogenolysis reactions (HER). Herein, we constructed a metal-organic tetrahedral cage H1 (FeII4L6) with large inner cavity and Fe metal centers surrounded by hydrazide groups that act as hydrogen bond acceptance sites. This enables the cage to efficiently recognise nitrite and thermodynamically activate it under electrocatalytic conditions for efficient reduction to ammonium. The kinetic experinments demonstrated that the catalytic process followed the Michaelis-Menten mechanism, which further verified the key role of host-guest interactions in the mimetic activation of nitrite and the enzyme-like catalyic behavior