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Issue 25, 2017

Syntheses of asymmetric zinc porphyrins bearing different pseudo-pyridine substituents and their photosensitization for visible-light-driven H2 production activity

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Abstract

A series of asymmetric zinc porphyrin (ZnPy) derivatives bearing different external substituents were synthesized and used to sensitize Pt-loaded graphitic carbon nitride (Pt/g-C3N4) for photocatalytic H2 production. Among them, ZnPy-1 has one benzoic acid and three phenyls as peripheral substituents, while ZnPy-2, ZnPy-3, and ZnPy-4 contain one benzoic acid and three pseudo-pyridines with different N-atom positions. The experimental results indicate that the pseudo-pyridine substitution for the phenyls in ZnPy-1 lead to enhanced photosensitization with an order of ZnPy-1 < ZnPy-2 < ZnPy-3 < ZnPy-4 under visible light (λ > 420 nm) irradiation. ZnPy-4-sensitized Pt/g-C3N4 (ZnPy-4-Pt/g-C3N4) exhibits the best average H2 production activity of 524 μmol h−1 with an extremely high turnover number (TON) of 11 089 h−1, which is much higher than that (328 μmol h−1) of ZnPy-2-Pt/g-C3N4 with a TON of 6942 h−1. Also, ZnPy-4-Pt/g-C3N4 shows a much higher apparent quantum yield (AQY) of 32.3% than that (11.5%) of ZnPy-2-Pt/g-C3N4 under 420 nm monochromatic light irradiation. The different N-atom positions in the pseudo-pyridines result in different interactions of the ZnPy dyes with a sacrificial reagent, which then strongly influences the photoactivity for H2 production. The present results demonstrate the molecular engineering aspect of ZnPy dyes in which fine-tuning of molecular structures is crucial for improving the photocatalytic H2 production activity of dye-sensitized semiconductors.

Graphical abstract: Syntheses of asymmetric zinc porphyrins bearing different pseudo-pyridine substituents and their photosensitization for visible-light-driven H2 production activity

Supplementary files

Article information


Submitted
22 Mar 2017
Accepted
30 May 2017
First published
30 May 2017

Dalton Trans., 2017,46, 8219-8228
Article type
Paper

Syntheses of asymmetric zinc porphyrins bearing different pseudo-pyridine substituents and their photosensitization for visible-light-driven H2 production activity

Y. Zheng, J. Wang, J. Zhang, T. Peng and R. Li, Dalton Trans., 2017, 46, 8219 DOI: 10.1039/C7DT01029J

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