Zeolite-Fixed TiO ₂ Nanosheets for Accurate and Shape-Selective Photodegradation of Pollutants

The abilities of a strong redox reaction and efficient selective removal of harmful molecules are two important factors in the photodegradation of organic pollutants for ideal environmental remediation. However, it is still an arduous pursuit to acquire shape-selective photocatalytic performance for photocatalysts owing to the randomly destructive effect of free radicals generated on the surface of catalysts toward both harmful pollutants and eco-friendly organisms in nature. Herein, an eco-friendly photocatalyst (TiO2 NSs@Y-zeolite) was synthesized by engineering the highly active {001} facet exposure of TiO2 nanosheets (NSs) via controlling fluorine doping, followed by fixation inside the Y-zeolite crystals. The as-prepared zeolite-fixed TiO2 NSs demonstrated outstanding eco-friendly capabilities with fairly effective shape-selective photodegradation activity. The aniline pollutant can be completely removed over the catalyst under 360 min UV–vis illumination in the aniline and chlorophyll mixed aqueous solution, while the eco-friendly chlorophyll macromolecules remain nearly unharmed with a lower photodegradation rate of 5%. The excellent shape-selective properties of the photocatalyst are ascribed to the sieving effect of the micropores in the Y-zeolite shelter, which only allows the aniline small molecules to access the catalyst surface while preventing the bulky chlorophyll from passing through. We found that it is photogenerated hole carriers, rather than electrons, that are rapidly transferred to the active {001} facets of TiO2 NSs driven by the built-in internal electric field (IEF) to undergo a strong redox reaction. The strong interaction between aniline and the exposed {001} facets, with some possible planar adsorption state, was also first found due to the dipole–dipole/coordination interactions between the nitrogen atom of the dipolar aniline and the Ti4+ site at the surface of the dipolar TiO2 lattice, which is favorable to the efficient photodegradation of the pollutant aniline.