Panchromatic Sensitization with Zn^II Porphyrin‐Based Photosensitizers for Light‐Driven Hydrogen Production

Abstract

Abstract Three molecular photosensitizers (PSs) with carboxylic acid anchors for attachment to platinized titanium dioxide nanoparticles were studied for light‐driven hydrogen production from a fully aqueous medium with ascorbic acid (AA) as the sacrificial electron donor. Two zinc(II) porphyrin (ZnP)‐based PSs were used to examine the effect of panchromatic sensitization on the photocatalytic H 2 generation. A dyad molecular design was used to construct a difluoro boron‐dipyrromethene (bodipy)‐conjugated ZnP PS (ZnP‐dyad), whereas the other one featured an electron‐donating diarylamino moiety (YD2‐ o ‐C8). To probe the use of the ZnP scaffold in this particular energy conversion process, an organic PS without the ZnP moiety (Bodipy‐dye) was also synthesized for comparison. Ultrafast transient absorption spectroscopy was adopted to map out the energy transfer processes occurring in the dyad and to establish the bodipy‐based antenna effect. In particular, the systems with YD2‐ o ‐C8 and ZnP‐dyad achieved a remarkable initial activity for the production of H 2 with an initial turnover frequency (TOF i ) higher than 300 h −1 under white light irradiation. The use of ZnP PSs in dye‐sensitized photocatalysis for the H 2 evolution reaction in this study indicated the importance of the panchromatic sensitization capability for the development of light absorbing PSs.