As we all know, titanium dioxide (TiO₂) is one of the most promising photocatalysts for degradation of toxic volatile organic compounds (VOC) ideally under environmentally friendly conditions. While H-ZSM-5 zeolites are commonly used in industrial catalysis as an important adsorbent or host material. This paper mainly focused on designing TiO₂-sorbent hybrid photocatalytic materials, especially those supported on ZSM-5 zeolites, with the objective of fabricating efficient photodegradation systems toward organic compounds diluted in air. ZSM-5-TiO₂ composites were fabricated by an impregnation method. First, the TiO₂ nanocrystals with diameter about 5 nm were prepared by solvothermal process. Next, these TiO₂ nanocrystals were loaded on the ZSM-5 zeolites through impregnating at a relatively low temperature about 150 ℃. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The fundamental adsorption- photocatalytic behaviors were investigated in the removal of toluene vapor diluted in air. In the case of hybrid photocatalysts, the initial toluene concentration in gas phase was significantly reduced because of adsorption into the ZSM-5. After photo-irradiation started, toluene was continuously decomposed. The results found that TiO₂ nanocrystals were uniformly distributed on the surface of ZSM-5 zeolites by using of impregnation method. Simultaneously the synergistic effects between adsorption properties and photocatalysis were discussed in this paper, as well as the structure-activity relationship. The weight ratio of TiO₂ and SiO₂/Al₂O₃ ratio of the ZSM-5-TiO₂ composites will significantly affect hydrophobicity index (HI), adsorption and photocatalytic efficiency. The effect of the amount of the adsorbent on the photocatalytic activity was investigated and provided a novel physicochemical insight into adsorption-photocatalytic synergistic removal of organic pollutants. The present study affords a fundamental understanding of hybrid materials of TiO₂ and ZSM-5 zeolite, highlighting an enhancement of photocatalytic activity of supported TiO₂ on such adsorbed materials.

Key words: ZSM-5-TiO₂ composites, adsorption, photocatalysis