Chinese Journal of Catalysis ›› 2020, Vol. 41 ›› Issue (8): 1288-1297.DOI: 10.1016/S1872-2067(20)63572-0

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Asymmetric photocatalysis over robust covalent organic frameworks with tetrahydroquinoline linkage

Chunzhi Lia,b, Yinhua Mab,c, Haoran Liua, Lin Taoa,b, Yiqi Rena,b, Xuelian Chena, He Lia, Qihua Yanga   

  1. a State Key Laboratory of Catalysis, iChEM, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b University of Chinese Academy of Sciences, Beijing 100049, China;
    c State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
  • Received:2019-11-27 Revised:2019-12-23 Online:2020-08-18 Published:2020-08-08
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (21733009, 21621063), and the Strategic Priority Research Program of Chinese Academy of Sciences (XDB17020200).

Abstract: The asymmetric photocatalytic organic synthesis (APOS) process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source. However, it still lacks efficient semiconductors with tunable band structures and has a low recycling stability. Herein, we report the synthesis of tetrahydroquinoline-linked covalent organic frameworks (QH-COFs) with irreversible tetrahydroquinoline linkage as efficient semiconductors for the visible-light-driven asymmetric α-alkylation of aldehydes by merging with a chiral secondary amine. Up to 94% ee was obtained over QH-COFs, and the activity of QH-COFs was significantly higher than those of inorganic semiconductors (e.g., TiO2, BiVO4, and WO3) under similar conditions, which is mainly attributed to their narrow band gap and suitable band edge. As far as we know, QH-COFs are the most active semiconductors for asymmetric α-alkylation of aldehydes ever reported. The QH-COFs were prepared via a one-pot Povarov cascade imine formation and cycloaddition reaction using Sc(OTf)3/Yb(OTf)3 as Lewis acid catalysts. Attributed to the tetrahydroquinoline linkage, QH-COFs showed extremely high recycling stability, which made practicals application possible. This work not only opens up a new avenue for asymmetric photocatalysis but also provides an efficient and general method for the construction of robust COFs.

Key words: Photocatalysis, Covalent organic frameworks, Tetrahydroquinoline linkage, Asymmetric catalysis, Ultrastability