Synthesis and characterization of novel unsymmetrical phthalocyanine/TiO₂ composites and their evaluation as photocatalysts for degradation of 4-chlorophenol under visible light

We prepared novel unsymmetrical A 3 B-type zinc and cobalt phthalocyanines bearing monocarboxylic acid groups on peripheral positions using statistical condensation method, especially designed to anchor on the TiO2 semiconductor surface. The novel complexes were anchored on TiO2 semiconductor to prepare effective dye sensitized photoactive composites as heterogeneous catalysts. The results indicated that modified TiO2 nanocrystals possessed only the anatase phase and MPc-TiO2 photocatalysts with loading amount of dye ca. 8.27 µmol/g TiO2 exhibit strong visible light absorption. Photocatalytic degradation of 4-chlorophenol (4-CP) under illumination with visible light (λ > 400 nm) was tested with the composites prepared. The degradation profile indicates that MPc-modified titania nanocrystals are superior to pristine titania under visible light in terms of photocatalytic effect. Photocatalytic reusability efficiency and the stability of photocatalyst composites were also investigated. Additionally, the effect of different substituent groups (such as aromatic vs. aliphatic, alkyl chain length) on photocatalytic efficiency was revealed and also compared to our previous works.