Antenna Effect in BODIPY-(Zn)Porphyrin Entities Promotes H₂ Evolution in Dye-Sensitized Photocatalytic Systems

In this study, we report the utilization of BODIPY-(Zn)­Porphyrin hybrids in photocatalytic H₂ production from water. These entities were applied as photosensitizers upon their chemisorption onto the surface of platinum-doped titanium dioxide nanoparticles (Pt-TiO₂), which acted as photocatalysts. To evaluate the impact of the different connectivity between the chromophores in photocatalytic in H₂ evolution, we employed two diverse BODIPY-(Zn)­Porphyrin entities, in which the BODIPY moiety is either covalently attached (BDP-Por) or axially coordinated (BDP­(Im)-Por) with the (Zn)­Porphyrin. The covalently connected dyad (BDP-Por) presented higher catalytic activity (17 500 TONs) compared to the axial coordinated (BDP­(Im)-Por, 13 700 TONs). In BDP-Por dyad, an additional BDP­(Im) moiety was introduced and the formed hybrid (BDP-Por-BDP­(Im)) outperformed the aforementioned systems, due to the enhanced light harvesting ability. Overall, we developed highly efficient dye-sensitized photocatalytic systems (DSPs) based on noble-metal-free photosensitizers reaching 18 600 turnover numbers (TONs) and 225 mmol­(H₂) g­(cat)⁻¹ h^–1.