Regulating the Built-In Electric field in Covalent Organic Frameworks for Enhanced CO<sub>2</sub> Photoreduction: Asymmetry Linkage Structures
Qian Zhang, Xiao Zhao, Shuaiqi Gao, Yingying Guo, Huiyong Wang, Zhimin Liu, Jianji Wang
Abstract
Covalent organic frameworks (COFs) are an emerging kind of photocatalysts which convert CO 2 to value-added fuels. However, COFs usually exhibit lower catalytic efficiency without using metal, sacrificial reagent, or photosensitizer due to their easy electron–hole recombination. Herein, a series of imine-linked COFs with different asymmetric linkage structures have been synthesized to enhance the separation efficiency of photoexcited electron–hole pairs in the COFs by tuning the intramolecular built-in electric-field strength. The OH–COF exhibits a high CO production rate of 616 μmol g –1 in the 4 h reaction with ∼100% selectivity, which surpasses most of the metal-free COF photocatalysts reported in the literature. This reveals that the higher polarity of OH–COF with an asymmetric linkage structure leads to a stronger built-in electric-field strength and a faster charge-transfer rate and thus more efficient photocatalytic performance. This work would provide some insights into the built-in electric-field design of COFs for efficient CO 2 photoreduction.