Controlled Self-Assembly of Zn-Tetraphenylporphyrins for Efficient Photocatalytic Solar H2 Production and Simultaneous Organic Transformation to Valuable Chemicals

Abstract

Herein, we have designed aqueous dispersed self-assembled nanostructures with diverse morphologies from the zinc tetraphenyl porphyrin (ZnTPP) monomer employing simple solution-based coprecipitation methods. Detailed morphological studies have been carried out by various electron microscopy techniques. Finally, the structural features were correlated with the underpinning photophysical processes using steady-state and time-resolved spectroscopy. Detailed studies suggest that controlled morphology and highly defined intermolecular interactions affect the overall photoinduced charge transfer process. Based on the fundamental investigations, all these different types of nanostructures have been utilized as photocatalysts for solar hydrogen production without using any cocatalysts, and it was found that the spherical nanostructure exhibits significantly higher H₂ production rates of ∼1682 μ mole/g, which is a few folds higher than other 1D and 2D nanostructured materials. The experimental findings were further supported by the TD-DFT study. Furthermore, the detailed computational studies suggest that the spherical aggregates exhibited a more vital interaction between the ZnTPP molecules, causing significant electronic coupling between bright local excited and charge transfer states, which supports our experimental findings. Finally, we have selectively utilized the oxidative half-reaction for the simultaneous transformation of glycerol to valuable chemicals along with photocatalytic H₂ production through reductive half-reaction.