Supramolecular nanomaterials with photocatalytic activity obtained via self-assembly of a fluorinated porphyrin derivative

Porphyrin aggregates formed via self-assembly have shown promising photocatalytic activity due to the combination of their optical and morphological properties. The structural and physical properties of porphyrin affect its self-assembly and the properties of the resulting aggregates. The hydrophobicity/hydrophilicity of the porphyrins in solvent mixtures, which affect self-assembly, can be altered by the introduction of fluorine groups. In this work, we report the synthesis of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPFPP). The differing solubilities of TPFPP in organic and aqueous solutions were exploited to promote the self-assembly of monomeric TPFPP in THF/H2O solvent mixtures. The effect of the H2O fraction on the assembly process and resulting morphologies was probed using UV–vis spectroscopy, photoluminescence spectroscopy, and scanning electron microscopy (SEM). It was observed that well-defined TPFPP microrods with a diameter of 1–3 µm and length of 20–100 µm as well as octahedral crystals 30 µm in size were produced with H2O fractions of 70 and 80%, respectively. These TPFPP aggregates with controlled morphologies exhibited high photocatalytic activity, evident in photocatalytic degradation studies with rhodamine B (RhB) which degraded under visible light irradiation with rate constants of 3.76 × 10−3 (with microrods) and 2.93 × 10−3 min−1 (with octahedral crystals). A possible mechanism for the photocatalytic activity of the TPFPP aggregates for RhB degradation was proposed.