Asymmetric Manganese Sites in Covalent Organic Frameworks for Efficient Nitrate‐to‐Ammonia Electrocatalysis

Abstract

Abstract The electrocatalytic nitrate reduction reaction (NO 3 − RR) holds tremendous potential for remediating NO 3 − pollution while enabling clean ammonia (NH 3 ) production. However, most catalysts achieve high conversion efficiency relying on high NO 3 − concentrations. How to catalyze the NO 3 − RR with a low concentration of NO 3 − is still a challenge due to the competing hydrogen evolution reaction (HER). Herein, we constructed a novel asymmetric isolated Mn atom based on N‐coordination covalent organic framework (COF) (ImPy‐COF‐Mn), for efficient NO 3 − RR at a low NO 3 − concentration of 2 mg mL −1 . This bidentate‐coordinated COF featured a robust and chemically stable framework, while the synergistic interaction between asymmetric imine N and pyridine N modified the charge distribution of Mn atoms to optimize catalytic efficiency. ImPy‐COF‐Mn demonstrated remarkable catalytic performance, with 95.64% NH 3 selectivity and a maximum NH 3 yield rate of 1927 mmol h −1 g cat. −1 , exceeding the corresponding parameters of symmetric Mn sites by factors of 1.27 and 1.41, respectively. In situ ATR‐FTIR measurements and theoretical calculations revealed that the asymmetric isolated Mn facilitated a reduction in the energy barrier for *NO‐to‐*NOH conversion, and thus contributed to higher activity and selectivity.