Zhou Jing, Zhao Jiani, Song Dengmeng, Liu Jiquan, Xu Wenhua, Li Jun, Wang Ning
Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an 710069, China.
College of Chemistry and Chemical Engineering, Xi'an Shiyou University, Xi'an 710065, China.
Inorg Chem. 2024 Aug 12;63(32):15177-15185. doi: 10.1021/acs.inorgchem.4c02553. Epub 2024 Aug 1.
The electrocatalytic reduction of nitrate (NO) to ammonia (NH) not only offers an effective solution to environmental problems caused by the accumulation of NO but also provides a sustainable alternative to the Haber-Bosch process. However, the conversion of NO to NH is a complicated process involving multiple steps, leading to a low Faradaic efficiency (FE) for NH production. The structural designability of covalent organic frameworks (COFs) renders feasible and precise modulation at the molecular level, facilitating the incorporation of multiple well-defined catalytic sites with different reactivities into a cohesive entity. This promotes the efficiency of the overall reaction through the coupling of multistep reactions. Herein, heterobimetallic CuP-CoBpy was prepared by postmodification, involving the anchoring of cobalt ions to the CuP-Bpy structure. As a result of the cascade effect of the bimetallic sites, CuP-CoBpy achieved an outstanding NH yield of 13.9 mg h mg with a high FE of 96.7% at -0.70 V versus the reversible hydrogen electrode and exhibited excellent stability during catalysis. A series of experimental and theoretical studies revealed that the CuP unit facilitates the conversion of NO to NO, while the CoBpy moiety significantly prompts the reduction of NO to NH. This study demonstrates that tailoring the structural units for the construction of COFs based on each step in the multistep reaction can enhance both the catalytic activity and product selectivity of the overall process.
将硝酸盐（NO）电催化还原为氨（NH₃）不仅为解决因NO积累而导致的环境问题提供了有效方案，还为哈伯-博施法提供了一种可持续的替代方法。然而，将NO转化为NH₃是一个涉及多个步骤的复杂过程，导致NH₃生产的法拉第效率（FE）较低。共价有机框架（COF）的结构可设计性使得在分子水平上进行可行且精确的调控成为可能，便于将具有不同反应活性的多个明确的催化位点整合到一个凝聚的实体中。这通过多步反应的耦合提高了整体反应的效率。在此，通过后修饰制备了异质双金属CuP-CoBpy，即将钴离子锚定到CuP-Bpy结构上。由于双金属位点的级联效应，CuP-CoBpy在相对于可逆氢电极-0.70 V时实现了13.9 mg h⁻¹ mg⁻¹的出色NH₃产率，FE高达96.7%，并且在催化过程中表现出优异的稳定性。一系列实验和理论研究表明，CuP单元促进NO向NO₂的转化，而CoBpy部分显著促进NO₂向NH₃的还原。这项研究表明，根据多步反应中的每一步定制用于构建COF的结构单元，可以提高整个过程的催化活性和产物选择性。
