Surface modification of TiO_2 by a ruthenium(Ⅱ) polypyridyl complex via silyl-linkage for the sensitized photocatalytic degradation of carbon tetrachloride by visible irradiation

摘要

A new ruthenium(Ⅱ) photosensitizer, [Ru~Ⅱ(py-pzH)_3]~(2+) (where py-pzH = 3-(2′-pyridyl)pyrazole), has been synthesized. The complex displayed outstanding excited state redox properties (estimated Ru~Ⅲ/Ru~(Ⅱ*)≈-1.24V vs. NHE) and was expected to sensitize the injection of electrons into the conduction band of anatase TiO_2 upon visible irradiation. The photosensitizer was anchored onto the surface of anatase TiO_2 particles via in situ silylation. The silyl-linkage displayed excellent stability in both aqueous media, over a wide pH range, and in common organic solvents. The resultant material, TiO_2-[Ru~Ⅱ(py-pz-Si≡)_3], was found to be able to mediate degradation of CCl_4 in neutral aqueous medium under broad band visible irradiation (λ > 450 nm). The relation between the rate of degradation and concentration of substrate was explored and the mechanism of the photodegradation of the perhalogenated organic was discussed.