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Enhancing charge transfer efficiency through carboxyl-modification to improve the photocatalytic activity of covalent organic frameworks for hydrogen evolution from water splitting
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DOI：10.1016/j.jcis.2025.01.247.png)
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Abstract
En 中文
The design of photocatalysts based on covalent organic frameworks (COFs) has attracted considerable interest. Nevertheless, the low efficiency in separating photogenerated carriers remains a substantial challenge. Herein, carboxyl modification is employed to enhance the separation efficiency of photogenerated carriers within iminebased porphyrin COFs through the resultant built-in electric field, thereby improving the photocatalytic performance of COFs in hydrogen evolution from water splitting. Spectroscopic and electrochemical analyses reveal that, compared with pristine two-dimensional porphyrin-based COFs (Por-COF), an isostructural carboxyl- modified COF (Por-COOH-COF) exhibits a prolonged excited-state lifetime, reduced exciton binding energy and decreased deactivation probability via radiative processes, and an improved photocurrent response. These improvements result in a hydrogen evolution of 12773 +/- 297 mu mol & sdot;g-1 & sdot;h-1 for Por-COOH-COF, approximately four times higher than that of Por-COF (3351 +/- 197 mu mol & sdot;g- 1 & sdot;h-1), positioning it among the most efficient metal-free COF photocatalysts reported to date. Density functional theory calculations and in situ X-ray photoelectron spectroscopy analyses indicate that carboxyl modification facilitates charge transfer from the porphine core to the active site of the imine bond (-C--N-) under the ultraviolet-visible light irradiation, thereby contributing to the remarkable photocatalytic activity of Por-COOH-COF. This study elucidates how carboxyl groups positively influence photogenerated carrier separation within COFs and provides valuable insights into the development of high-performance metal-free COFs photocatalysts.
Keywords:
Porphyrin covalent organic frameworks
Carboxyl-modified
Hydrogen evolution
Metal-free photocatalysts
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9.7
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3.7W
Citations:
14.7W
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