Subphthalocyanines for Visible-Light-Driven Hydrogen Evolution: Tuning Photocatalytic Performance with Molecular Design

In this work, a series of subphthalocyanines (SubPcs)with a carboxylicacid anchoring group at the axial position were used as photosensitizersof TiO2 for photocatalytic hydrogen evolution from waterunder visible light irradiation. SubPc derivatives with various peripheralsubstituents were successfully prepared to systematically investigatethe dependence of photocatalytic performance on electron-donatingunits (i.e., bisthiophene or thioether) at the peripheral positionof the SubPcs. SubPc 2/TiO2/Pt shows the best photocatalyticactivity among the three dye-sensitized photocatalysts, with a hydrogenevolution rate of 1.104 mmol center dot g(-1)center dot h(-1). After 24 h irradiation, SubPc 2/TiO2/Ptachieved a remarkable catalytic activity for the production of H-2 (19.96 mmol center dot g(-1)) with a TON valueof 40 734 and a high STH efficiency of 2.1%. Density functionaltheory (DFT) and time-dependent DFT (TD-DFT) approaches were usedto elucidate further structural and electrical properties, includingthe interaction patterns of tailored SubPcs. It is worth noting thatthe theoretical computations exhibit good conformity with the empiricaldata. The predicted fluctuations in photocatalytic activity detectedin SubPc systems were shown to be closely associated with frontiermolecular orbital (FMO) characteristics, noncovalent interaction (NCI)patterns, and the electron-donating nature of the fragments locatedat the peripheral positions.

Automated summary

In this study, SubPcs with a carboxylic acid anchoring group were utilized as photosensitizers of TiO2 for visible light-driven hydrogen evolution. The impact of various peripheral substituents on the photocatalytic performance of SubPcs was systematically studied. Among the different dye-sensitized photocatalysts, SubPc 2/TiO2/Pt exhibited the highest hydrogen evolution rate of 1.104 mmol center dot g(-1)center dot h(-1). Theoretical calculations based on DFT and TD-DFT methods provided insights into the structural and electrical properties of the tailored SubPcs, showing good agreement with experimental data. The fluctuations in photocatalytic activity observed in SubPc systems were found to be associated with frontier molecular orbital characteristics, noncovalent interaction patterns, and the electron-donating nature of the peripheral groups.