The acceleration of BODIPY dye-sensitized photocatalytic hydrogen production in aqueous ascorbic acid solutions using alkyl-chain formed second coordination sphere effects

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 11; no. 39; pp. 21153 - 2116
• Main Authors: Shen, Xiao-Feng, Watanabe, Motonori, Song, Jun Tae, Takagaki, Atsushi, Abe, Tatsuki, Tanaka, Keiji, Ishihara, Tatsumi
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 10.10.2023
• Subjects: Acceleration; Ascorbic acid; Boron; Catalytic activity; Charge transfer; Coordination; Density functional theory; Dyes; Electromagnetic absorption; Functional groups; Hydrogen; Hydrogen production; Hydrophobicity; Photocatalysis; Photosensitization; Substitution reactions
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d3ta03682k

BODIPY (boron-dipyrromethene) compounds are extensively utilized in various applications. Typically, their activity is modified by altering the functional groups at the α-, β-, and meso-positions of the substituents. However, no systematic information has been provided regarding the effects of substituted F- positions and hydrophobicity on the activity of BODIPY sensitizers in photosensitizing chemistry. Dyes ( 7a-7c ) with different alkyl chain lengths were synthesized and compared with the unsubstituted compound 3 to discuss the effects of -F position substituents and the hydrophobicity of BODIPY dyes on photocatalytic activity. Density functional theory (DFT) calculations showed that -F-substitution induced an intramolecular charge transfer (ICT) effect, enhancing visible-light absorption. Longer alkyl chains provided a favourable second coordination sphere reaction environment for hydrogen production. Experimentally, dye 7c demonstrated the highest activity, with a hydrogen production rate of 496.5 μmol g cat −1 h −1 , which is 3 times higher than that of 3 , and a 9.6 times higher turnover frequency (TOF) than that of 3 . The apparent quantum yield (AQY) at 650 nm was 1.4%. This study highlights the importance of -F position substitution and optimizing hydrophobicity to enhance the photocatalytic activity of metal-free organic dyes through the creation of a new second coordination sphere. Optimizing hydrogen production in ascorbic acid solutions: enhancing BODIPY dye-sensitized processes through alkyl-chain-enhanced second coordination sphere effects.