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In this article, an ordered two-dimensional (2D) hexagonal mesoporous anatase crystals–silica nanocomposite was first synthesized using synchronous-assembly of surfactant and inorganic precursors molecules, and then a three-dimensional (3D) interconnected mesoporous anatase TiO 2 was prepared via an “ extracting silica ” approach. The results show that the mesopore channels in our titania are highly connected by plenty of 3D uniform intrawall mesopores while retaining mesostructural integrity and regularity. The TiO 2 prepared is completely anatase crystalline with uniform nanocrystals (13.0 nm in size) and a high specific surface area (∼ 145 m 2 /g). This method is mild, simple and can be easily repeatable. The photocatalytic degradation rates of Acid Red 1 (0.173 min −1 ) and microcystin−LR (2.57 min −1 ) on the interconnected mesoporous TiO 2 are very high, which are 41.6 and 2.85 times higher than that of the parent sample; 29.2 and 7.20 times that of P25 photocatalyst, respectively. These results clearly demonstrated that the 3D interconnected mesostructure played a key role in the activity increments. In addition, our photocatalysts are considerably stable and reusable. To the best of our knowledge, such results have not been seen in the literature before. Furthermore, the fundamentals of this study would provide new insights for the rational design and preparation of 3D highly interlinked mesoporous metal-oxides with unique photocatalytic performances. [ABSTRACT FROM AUTHOR]

In this article, a simple and mild preparation of secondary pores are reported, for the first time, with uniform and tunable sizes (in a wide range of 0.9-4.8 nm) in the walls highly connecting the primary mesochannels in 3D mesopore networks. The uniform secondary pores are obtained by using ordered 2D hexagonal mesoporous anatase TiO2-SiO2 nanocomposites as precursors, NaOH as an etchant via an 'extracting SiO2' approach. The strategy here adopts diluted NaOH solution, appropriate extraction temperature, and solid/liquid ratio. The photocatalytic degradation rates of Rhodamine B (0.347 min-1), Acid Red 1 (0.0487 min-1), microcystin-LR (1.66 min-1) on the representative resultant nanocomposite are very high, which are 4.63, 11.7, 1.84 times that of the precursor without secondary mesopores; even up to 18.9, 8.21, 4.66 times that of P25, respectively. These results clearly demonstrate that the secondary mesopores play an overwhelming role to the increments of activities. The mesoporous anatase-silica nanocomposites with secondary mesopores present unprecedented-high degradation activities to various organic pollutants in the mesoporous metal-oxides-based materials reported up to now and are considerably stable and reusable. It is believed that the fundamentals in this study will provide new insights for rational design and preparation of 3D highly interconnected mesoporous metal-oxides-based materials with super-high performances. [ABSTRACT FROM AUTHOR]

Abstract: Ordered 2-D hexagonal mesoporous TiO2–SiO2 nanocomposites consisted of anatase TiO2 nanocrystals and amorphous SiO2 nanoparticles, with large mesochannels and high specific surface areas, have been extensively and detailedly evaluated using various cationic dyes (methylene blue, safranin O, crystal violet, brilliant green, basic fuchsin and rhodamine-6G), anionic dyes (acid fuchsin, orange II, reactive brilliant red X3B and acid red 1) and microcystin-LR. We use mesoporous 80TiO2–20SiO2-900 for the degradation of cationic dyes and MC-LR, due to the dominant adsorption of Si and synergistic role of coupled adsorption and photocatalytic oxidation. For anionic dyes, due to the adsorption results predominantly from Ti, our strategy realizes the enhanced photocatalytic oxidation by strong surface acids and larger available specific surface area. Based on this, we prepared 90TiO2–10SiO2-700 to degrade them. The results show that our samples exhibit excellent degradation activities to all the contaminants, which are much higher than that of P25 photocatalyst. The dyes are not only decolorized promptly but degraded readily as well. It is strongly indicated that our mesoporous nanocomposites are considerably stable and reusable. These results demonstrate that our mesoporous TiO2–SiO2 nanocomposites present extensive and promising application in the fast and highly efficient degradation of various organic pollutants. [Copyright &y& Elsevier]

Abstract: In this paper, we report a synchronous role of coupled adsorption and photocatalytic oxidation on ordered 2-D hexagonal mesoporous TiO2–SiO2 nanocomposites with large pore channels (>4.0nm) and high specific surface areas (>70m2 g−1). These mesoporous frameworks consist of anatase TiO2 nanocrystals and amorphous SiO2 nanomatrixes, which link mutually, coexist to form unique composite-walls, providing unprecedented spaces for “the synchronous role of coupled adsorption and photocatalytic oxidation”. SiO2 nanomatrixes are excellent adsorbents, providing better adsorption centers and enriching organic pollutant molecules; while anatase nanocrystals behave as photocatalytic active sites to oxide the organic molecules pre-enriched by the surrounding SiO2 particles. Moreover, the high accessible surface areas can provide more adsorptive and photocatalytically active sites; and the large mesopore channels allow the reactive molecules to diffuse more easily both into and out of the inner surfaces before and after photocatalytic reactions, respectively. Our strategy realizes the synchronous role by adjusting Ti/Si ratios, the number of surface hydroxyls, the size and crystallinity of the anatase nanocrystals on the unique composite-frameworks. The cationic rhodamine-B (RhB) dye is used as the target pollutant to characterize the adsorption performance and photocatalytic activities. Our results show that the synchronous role results in excellent photocatalytic degradation activity (k =0.231min−1), which is much higher than that of Degussa commercial P25 photocatalyst (k =0.0671min−1). [Copyright &y& Elsevier]