Chinese Journal of Catalysis ›› 2025, Vol. 74: 144-154.DOI: 10.1016/S1872-2067(25)64717-6

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Highly conjugated and chemically stable three-dimensional covalent organic frameworks for efficient photocatalytic CO2 reduction

Lin Zhanga,1, Hui Zhanga,1, Jinghong Fangb, Jialin Cuia, Jie Liuc, Hui Liua,*(), Lishui Suna, Qiong Sunb,*(), Lifeng Dongb,*(), Yingjie Zhaoa,*()   

  1. aEngineering Research Center of High-Performance Polymer and Molding Technology, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, Shandong, China
    bCollege of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, Shandong, China
    cCenter for High-Pressure Science and Technology Advanced Research, Beijing 100193, China
  • Received:2024-12-25 Accepted:2025-03-14 Online:2025-07-18 Published:2025-07-20
  • Contact: *E-mail: hliu@qust.edu.cn (H. Liu), sunqiong@qust.edu.cn (Q. Sun), *donglifeng@qust.edu.cn (L. Dong), yz@qust.edu.cn (Y. Zhao).
  • About author:1Contributed equally to this work.
  • Supported by:
    National Natural Science Foundation of China(22205128);National Natural Science Foundation of China(22175101);Shandong Provincial Natural Science Foundation(ZR2022QB054)

Abstract:

Covalent organic frameworks (COFs), as efficient photocatalysts, can convert CO2 and H2O into value-added fuel, thus improving the deteriorating ecological environment. However, achieving high photocatalytic efficiency and selectivity without relying on noble metals or sacrificial agents remains a significant challenge. Here, a highly conjugated three-dimensional (3D) COF 3D-COF-1 with imine linkage is constructed by the combination of two rigid and conjugated orthogonal building blocks (spirobifluorene and bicarbazole) with good photoactivites. Through a simple post-synthetic reduction, a chemically stable and amine-linked 3D-COF-2 which maintains excellent crystallinity and porosity can be obtained. Notably, the 3D-COF-2 exhibits excellent performance in CO2 reduction and exceptional selectivity of CO due to the highly conjugated structure and abundant amine groups as chemisorption sites for selectively capturing CO2. Under the irradiation of visible light and without noble metals and sacrificial agents, 3D-COF-2 produces 1070 μmol g-1 of carbon monoxide in 4.5 h, and the selectivity is close to 100%.

Key words: Covalent organic frameworks, Three-dimensional structure, Photocatalytic CO2 reduction, Metal-free catalysis, Chemically stable structure