Li Xuewen, Xia Shuai, Yang Shuai, Yang Xiubei, Zheng Shuang, Xu Xiaoyu, Wang Yan, Xu Qing, Jiang Zheng
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230029, P.R. China.
Advanced Separation & Conversion on Engineered Nanopore Dynamics Laboratory, Shanghai Advanced Research Institute (SARI), Chinese Academy of Sciences (CAS), Shanghai, 201210, P.R. China.
Angew Chem Int Ed Engl. 2025 Jul;64(29):e202507479. doi: 10.1002/anie.202507479. Epub 2025 May 24.
The electrocatalytic nitrate reduction reaction (NO RR) holds tremendous potential for remediating NO pollution while enabling clean ammonia (NH) production. However, most catalysts achieve high conversion efficiency relying on high NO concentrations. How to catalyze the NO RR with a low concentration of NO 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 RR at a low NO concentration of 2 mg mL. 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 selectivity and a maximum NH yield rate of 1927 mmol h g , 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.
电催化硝酸盐还原反应（NO RR）在修复NO污染同时实现清洁氨（NH₃）生产方面具有巨大潜力。然而，大多数催化剂依靠高浓度NO来实现高转化效率。由于存在竞争性析氢反应（HER），如何在低浓度NO条件下催化NO RR仍是一项挑战。在此，我们构建了一种基于N配位共价有机框架（COF）的新型不对称孤立Mn原子（ImPy-COF-Mn），用于在2 mg mL⁻¹的低NO浓度下高效进行NO RR。这种双齿配位的COF具有坚固且化学稳定的框架，而不对称亚胺N和吡啶N之间的协同相互作用改变了Mn原子的电荷分布以优化催化效率。ImPy-COF-Mn表现出卓越的催化性能，NH₃选择性达95.64%，最大NH₃产率为1927 mmol h⁻¹ g⁻¹，相应参数分别比对称Mn位点高出1.27倍和1.41倍。原位ATR-FTIR测量和理论计算表明，不对称孤立的Mn促进了NO到NOH转化的能垒降低，从而有助于提高活性和选择性。
