新加坡南洋理工大学赵彦利团队开发了用于光催化固氮的锚定金单原子的卟啉基共价有机框架。相关研究成果于2023年3月8日发表在《美国化学会杂志》。

开发用于在环境条件下固定N₂以产生NH₃的高效光催化剂仍然是一个巨大的挑战。由于共价有机框架（COFs）具有预定的化学结构、良好的结晶度和高孔隙率，因此探索其在光催化氮转化中的潜力具有重要意义。

该文中，研究人员报道了一系列负载有Au单原子（COFX–Au，X=1–5）的同构卟啉基COFs用于光催化N₂固定。卟啉构建块充当了固定Au单原子的对接位点以及光收集天线。金催化中心的微环境通过控制卟啉单元近端和远端位置的官能团来精确调节。因此，用强吸电子基团修饰的COF₁–Au对NH₃生成表现出高活性，其速率为333.0±22.4μmol g^–1 h^–1和37.0±2.5 mmol g _Au^–1 h^-1，分别比用给电子官能团修饰的COF4–Au和卟啉–Au分子催化剂高2.8倍和171倍。在具有两种不同类型强吸电子基团的COF₅-Au催化下，NH₃生成速率可进一步提高至427.9±18.7μmol g^–1 h^–1和61.1±2.7 mmol g _Au^–1 h^-1。

结构-活性关系分析表明，吸电子基团的引入促进了整个框架内光生电子的分离和运输。该项工作表明，COF基光催化剂的结构和光电特性可以通过在分子水平上的合理预先设计进行精细调整，从而导高效的NH₃析出。

附：英文原文

Title: Porphyrin-Based Covalent Organic Frameworks Anchoring Au Single Atoms for Photocatalytic Nitrogen Fixation

Author: Ting He, Zhanfeng Zhao, Ruoyang Liu, Xinyan Liu, Bing Ni, Yanping Wei, Yinglong Wu, Wei Yuan, Hongjie Peng, Zhongyi Jiang, Yanli Zhao

Issue&Volume: March 8, 2023

Abstract: The development of efficient photocatalysts for N2 fixation to produce NH3 under ambient conditions remains a great challenge. Since covalent organic frameworks (COFs) possess predesignable chemical structures, good crystallinity, and high porosity, it is highly significant to explore their potential for photocatalytic nitrogen conversion. Herein, we report a series of isostructural porphyrin-based COFs loaded with Au single atoms (COFX–Au, X = 1–5) for photocatalytic N2 fixation. The porphyrin building blocks act as the docking sites to immobilize Au single atoms as well as light-harvesting antennae. The microenvironment of the Au catalytic center is precisely tuned by controlling the functional groups at the proximal and distal positions of porphyrin units. As a result, COF1–Au decorated with strong electron-withdrawing groups exhibits a high activity toward NH3 production with rates of 333.0 ± 22.4 μmol g–1 h–1 and 37.0 ± 2.5 mmol gAu–1 h–1, which are 2.8- and 171-fold higher than that of COF4–Au decorated with electron-donating functional groups and a porphyrin–Au molecular catalyst, respectively. The NH3 production rates could be further increased to 427.9 ± 18.7 μmol g–1 h–1 and 61.1 ± 2.7 mmol gAu–1 h–1 under the catalysis of COF5–Au featuring two different kinds of strong electron-withdrawing groups. The structure–activity relationship analysis reveals that the introduction of electron-withdrawing groups facilitates the separation and transportation of photogenerated electrons within the entire framework. This work manifests that the structures and optoelectronic properties of COF-based photocatalysts can be finely tuned through a rational predesign at the molecular level, thus leading to superior NH3 evolution.

DOI: 10.1021/jacs.2c10233

Source: https://pubs.acs.org/doi/10.1021/jacs.2c10233