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

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

doi:10.1021/jacs.2c10233

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

J Am Chem Soc. 2023 Mar 22;145(11):6057-6066. doi: 10.1021/jacs.2c10233. Epub 2023 Mar 8.

Authors

Ting He¹, Zhanfeng Zhao^{2

3}, Ruoyang Liu⁴, Xinyan Liu⁵, Bing Ni⁶, Yanping Wei⁷, Yinglong Wu¹, Wei Yuan¹, Hongjie Peng⁵, Zhongyi Jiang^{2

3

8}, Yanli Zhao¹

Affiliations

¹ School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore 637371, Singapore.
² Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China.
³ Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, P. R. China.
⁴ Department of Chemistry, Faculty of Science, National University of Singapore, Singapore 117543, Singapore.
⁵ Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, P. R. China.
⁶ Physical Chemistry, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany.
⁷ College of Science, Gansu Agricultural University, Lanzhou 730070, P. R. China.
⁸ Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, P. R. China.

PMID: 36888741
DOI: 10.1021/jacs.2c10233

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 g_Au^-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 g_Au^-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.