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Graphical abstract Highlights • Mesoporous TiO 2 -SiO 2 nanocomposites with 3D tunable intrawall pores were prepared. • The preparation method is simple, moderate and facilely reproducible. • The photocatalysts with 3D large intrawall pores display quite excellent activities. • The activities are far higher than that of the parent material and P25 photocatalyst. • The photocatalysts with large intrawall mesopores are rather stable and reusable. Abstract Mesoporous anatase crystal-silica nanocomposites with three-dimensional (3D) uniform and tunable intrawall mesopores connecting the mesochannels have been successfully prepared using the approach of first synthesizing titania-silica nanocomposites with ordered two-dimensional hexagonal mesochannels via "synchronous-assembly" of inorganic precursors with surfactant, then "extracting silica". The uniform intrawall pores can be finely tuned in 3.6–5.6 nm by the strategy of adopting a large amount of silica in the walls, a very high crystallization temperature and mild silica extraction. The 3D interconnectivities of the mesochannels increase with extraction, but the mesostructures are retained intact. The average size of uniform anatase nanocrystals is 11.2 nm. This method is moderate, simple and facilely reproducible. The diffusion efficiencies of methylene blue (MB) in the mesostructures elevate with the intrawall mesopore size. The transient steady-state concentrations of •OH radicals rise fast with the intrawall pore size. The degradation rate of MB on the representative photocatalyst possessing large intrawall mesopores is extremely high (0.372 min−1), which is as high as 7.3 times that on the parent material, even up to 38.8 times that upon P25 photocatalyst. Our results clearly illustrate that the large intrawall mesopores play an overwhelming role in the increments of activities, while the matched adsorbability play an important synergetic role. Additionally, our photocatalysts are quite stable and reusable. Such results have not been seen in the literature till now. Furthermore, this approach is generally applicable to other metal-oxides-based materials, opening up a new avenue to rationally design and prepare mesostructures with 3D large intrawall mesopores, suitable adsorption and unexpected photocatalytic performances. [ABSTRACT FROM AUTHOR]

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]

• Mesoporous anatase titania with 3D large secondary mesopores was prepared. • The preparation approach is mild, simple and facilely reproducible. • The photocatalyst with 3D large secondary pores displays quite excellent activities. • The activities are far higher than that of P25 photocatalyst and the parent sample. • The photocatalyst with 3D large secondary mesopores is rather stable and reusable. A mesoporous titania (SN2) with three-dimensional (3D) large secondary mesopores (6.2 nm) highly connecting the mesochannels was prepared employing the method of first synthesizing an ordered 2D hexagonal mesoporous titania-silica nanocomposite (SN1) via "synchronous-assembly" of inorganic precursors with surfactant molecules, then "extracting silica". Our tactic adopts a large amount of silica, a high crystallization temperature and mild silica extraction. The 3D interconnectivities of the resultant mesochannels are quite high, but the mesostructures are retained intact. Titania is fully anatase crystalline with uniform nanocrystals size (11.2 nm) and a high specific surface area (∼ 174 m2 g−1). This strategy is gentle, simple and easily reproducible. SN2 presents extremely-high photocatalytic degradation activities to anionic azo dyes like acid red 1 and reactive brilliant red X3B, which reach 55.9 and 51.1 times that of commercial P25 photocatalyst, even up to 87.0 and 84.7 times that of SN1, respectively; and far higher than that of the contrast sample (CS) possessing 3D small secondary mesopores (2.7 nm). Additionally, SN2 also displays a very high activity to microcystin-LR, which is much higher than that of P25 and CS, respectively. Our results clearly indicate that the large secondary mesopores play a key role in the great increases of activities. Moreover, our photocatalyst is considerably stable and reusable. Such results have hitherto not been seen in the literature. Furthermore, this method would pave the way for the rational design and preparation of ordered mesoporous other metal-oxides with large secondary mesopores and unexpected performances. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a model study of a UV light-emitting-diode (UV-LED) based photocatalytic odor abatement process. It integrated computational fluid dynamics (CFD) modeling of the gas flow in the reactor with LED-array radiation field calculation and Langmuir–Hinshelwood reaction kinetics. It was applied to simulate the photocatalytic degradation of dimethyl sulfide (DMS) in a UV-LED reactor based on experimentally determined chemical kinetic parameters. A non-linear power law relating reaction rate to irradiation intensity was adopted. The model could predict the steady state DMS concentration profiles by calculating the advection, diffusion and Langmuir–Hinshelwood reaction kinetics. By affecting the radiation intensity and uniformity, the position of the LED array relative to the catalyst appeared to be a critical parameter determining DMS removal efficiency. Too small distances might yield low quantum efficiency and consequently poor abatement performance. This study provided an example of LED-based photocatalytic process modeling and gave insights into the optimization of light source design for photocatalytic applications. [Copyright &y& Elsevier]

Abstract: Bi2WO6 multilayer films have been fabricated successfully by a layer-by-layer (LbL) technique from Bi2WO6 nanoplates, which show higher visible-light photoactivity (λ>420nm) than that of Bi2WO6 nanoplate powders and P25 TiO2 films. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV–visible absorption spectroscopy. Photocatalytic activities of the films were evaluated by the rhodamine B (RhB) decomposition under UV and visible-light irradiation. Thickness and photoactivity of the film can be modified easily by changing the deposition cycles. Bi2WO6 films have the spectral selectivity of the photocatalytic degradation of RhB. Under the wavelength greater than 300nm, the RhB molecules tend to be transformed to rhodamine over Bi2WO6 films selectively. However, in the case of shorter wavelength (λ=254nm) light irradiation, the RhB molecules can be photodegraded completely. [Copyright &y& Elsevier]