Nature-inspired organic semiconductor via solvophobic self-assembly of porphyrin derivative as an effective photocatalyst for degradation of rhodamine B dye

Using photocatalysts to harvest photon energy from sunlight (renewable fuel) is a promising pathway for a wide range of applications, especially for the removal of contaminants from water. Porphyrin and its derivatives are analogs of natural chlorophyll; both compounds have similar structures and photochemical properties. Therefore, various porphyrin derivatives have been extensively studied as effective sensitizers for light energy absorption and as nature-inspired photocatalysts for water treatment. In this study, a simple solvophobic self-assembly protocol is employed to obtain nanostructured porphyrin from monomeric tetrakis-triphenylamine porphyrin (TTPAP) in a mixture of THF/H2O. The porphyrin is assembled into various forms such as rod-like and belt-like microstructures, depending on the water fraction in the THF/H2O mixture. The main driving forces for self-assembly of the TTPAP monomers into nanostructured materials are balanced stacking involving hydrophobic interactions of the periphery and pi-pi interactions of the porphyrin cores. While both porphyrin microstructures (rod-like and belt-like) show reasonable photocatalytic activity toward rhodamine B (RhB) dye in aqueous media under simulated visible irradiation, the belt-like porphyrin aggregates exhibit better performance than the rod-like counterparts under the same reaction conditions. A possible mechanism for the photocatalytic activity of the TTPAP aggregates in RhB degradation is also presented.