Two consecutive post-synthetic modifications of benzothiadiazole-based conjugated polymers for enhanced photocatalytic H-2 evolution: the significance of the sulfinyl group

摘要

Donor/acceptor (D-A) conjugated polymers represent a promising platform for photocatalytic H-2 evolution, and a variety of methods have been developed to expand the library of conjugated polymer-based candidates. However, strategies to facilely modulate the electronic structures are still a challenge. Herein, we demonstrate that the replacement of electron-withdrawing fluorine (F) in the F-substituted benzothiadiazole (BT)-based conjugated polymers with more electron-withdrawing methylsulfinyl (CH3SO) groups significantly increases the photocatalytic H-2 evolution rate (HER). To overcome the failure of direct polymerization, an approach involving two consecutive post-synthetic modifications (PSM) was innovatively adopted. F-substituted B-FBT-1,3,5-E was first converted into the electron-donating group methylthio (CH3S)-modified B-SBT-1,3,5-Evia the SNAr reaction, and the subsequent oxidation afforded the CH3SO-substituted B-SOBT-1,3,5-E. Photocatalytic H-2 evolution experiment results revealed that the HER of B-FBT-1,3,5-E, B-SBT-1,3,5-E and B-SOBT-1,3,5-E were 155.2 mu mol h(-1), 92.4 mu mol h(-1) and 280.0 mu mol h(-1), respectively, and the best performance of B-SOBT-1,3,5-E was attributed to the more electron-withdrawing and hydrophilic properties of the CH3SO-group. This protocol can also be extended to three more series of BT-based conjugated polymers with benzene replaced, highlighting the excellent property of the sulfinyl group for designing polymer-based photocatalysts toward solar-to-chemical energy conversion in the near future.