Shape dependent photocatalytic H₂ evolution of a zinc porphyrin

Hydrogen is regarded as a promising molecular fuel in order to produce clean energy, thus it is of great importance to produce and store H₂ in order to replace fossil fuels and to resolve the global energy and environmental problems. One strategy to produce hydrogen is the photocatalytic splitting of water. In this study different supramolecular architectures of a Zn(II) porphyrin, showing "flower", octahedral and "manta ray" shaped structures, were obtained using the "good-bad" solvent self-assembly protocol. More specifically, the bad solvent (methanol) was retained and the good solvent was alerted obtaining diverse assemblies. The different structures were studied by scanning electron microscopy, PXRD, UV-Vis and IR spectroscopies. The prepared structures were capable of proton reduction and production of molecular H₂ in the presence of 5% w/w Pt-nanoparticles as catalysts and ascorbic acid as a sacrificial electron donor. Moreover, depending on the structure of the chromophore that is formed the amount of H₂ produced varies. The maximum H₂ production was obtained with the octahedral structures (185.5 μmol g^-1 h^-1).