Surface Modification of TiO 2 by Hyper-Cross-Linked Polymers for Efficient Visible-Light-Driven Photocatalytic NO Oxidation.

Solar-driven photocatalysis offers an environmentally friendly and sustainable approach for the removal of air pollutants such as nitric oxides without chemical addition. However, the low specific surface area and adsorption capacity of common photocatalysts restrict the surface reactions with NO at the ppb-level. In this study, imidazolium-based hyper-cross-linked polymer (IHP) was introduced to modify the surface of TiO 2 to construct a porous TiO 2 /IHP composite photocatalyst. The as-prepared composite with hierarchical porous structure achieves a larger specific surface area as 309 m 2 /g than that of TiO 2 (119 m 2 /g). Meanwhile, the wide light absorption range of the polymer has brought about the strong visible-light absorption of the TiO 2 /IHP composite. In consequence, the composite photocatalyst exhibits excellent performance toward NO oxidation at a low concentration of 600 ppb under visible-light irradiation, reaching a removal efficiency of 51.7%, while the generation of the toxic NO 2 intermediate was suppressed to less than 1 ppb. The enhanced NO adsorption and the suppressed NO 2 generation on the TiO 2 /IHP surface were confirmed by in situ monitoring technology. This work demonstrates that the construction of a porous structure is an effective approach for efficient NO adsorption and photocatalytic oxidation.