High-Performance Photocatalytic Hydrogen Generation Using Robust Dianchoring Photosensitizers

A novel series of donor-donor-π-acceptor (D-D-π-A) 9,9'-dihexylfluorene-based dianchoring organic dyes, each featuring distinct bridging electron-donating moieties, have been synthesized and characterized. Their performances in photocatalytic hydrogen evolution (PHE) were evaluated, taking into account of their photophysical and electrochemical attributes. Remarkably, (Z)-3-(5-(4-((4-(5-((E)-2-carboxy-2-cyanovinyl)thiophen-2-yl)phenyl)(9,9-dihexyl-9H-fluoren-2-yl)amino)phenyl)thiophen-2-yl)-2-cyanoacrylic acid achieved an active and robust H₂ generation system with a turnover number (TON) of up to 17 400 in 126 h, with a production of 1090 μmol (26.3 mL) of hydrogen. The initial turnover frequency (TOF_i), initial activity (activity_i), and initial apparent quantum yield (AQY_i) were 808 h^-1, 505 mmol g^-1 h^-1, and 8.65%, respectively, under visible light irradiation in water. This photosensitizer is considered one of the most effective and durable systems for photocatalytic hydrogen production that attached to molecular Pt-TiO₂, as stated out in the literature using organic dyes under visible light, when compared the TOF and TON values. The experimental results demonstrated that the dianchoring dyes with bridging units could significantly enhance PHE performance, maintaining justifiable durability over prolonged irradiation.