Temperature-induced structural transformations of layered titanosilicate JDF-L1

Kostov‐Kytin, Vladislav; Mihailova, Boriana; Ferdov, Stanislav; Petrov, Ognyan

doi:10.1016/j.solidstatesciences.2004.04.007

Cited by 20 publications

(13 citation statements)

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“…Diffraction spots for the pristine phase having unit cell dimensions of a = b = 7.374 Å, c = 10.709 Å were indexed based on the room temperature X-ray crystallographic data (29); some of the representative Miller indices are indicated in color. It has been reported that JDF-L1 gradually loses its water upon annealing at a temperature higher than 423 K, and this loss induces a shrinkage of the interlayer space along the c-axis direction perpendicular to the basal plane (28,32). The dehydration process occurs slowly in the high vacuum of the microscope or when the specimen is heated by the laser; diffraction patterns of both structures are shown in Fig.…”

Section: Resultsmentioning

confidence: 95%

“…Here, we report the use of 4D ultrafast electron microscopy (UEM) (24)(25)(26) to trace the spatiotemporal behavior of the Ti(IV) and O 2− ions at the photocatalytic active center in the structurally well-characterized titanosilicate Na 4 Ti 2 Si 8 O 22 ·4H 2 O, known as JDF-L1 (27)(28)(29). JDF stands for Jilin-Davy-Faraday, as the crystalline solid described here was discovered and characterized in joint work involving Jilin University (P. R. China) and the Davy-Faraday Laboratory at the Royal Institution of Great Britain.…”

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confidence: 99%

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On the dynamical nature of the active center in a single-site photocatalyst visualized by 4D ultrafast electron microscopy

Yoo

Thomas

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Understanding the dynamical nature of the catalytic active site embedded in complex systems at the atomic level is critical to developing efficient photocatalytic materials. Here, we report, using 4D ultrafast electron microscopy, the spatiotemporal behaviors of titanium and oxygen in a titanosilicate catalytic material. The observed changes in Bragg diffraction intensity with time at the specific lattice planes, and with a tilted geometry, provide the relaxation pathway: the Ti 4+ =O 2− double bond transformation to a Ti 3+ −O 1− single bond via the individual atomic displacements of the titanium and the apical oxygen. The dilation of the double bond is up to 0.8 Å and occurs on the femtosecond time scale. These findings suggest the direct catalytic involvement of the Ti 3+ −O 1− local structure, the significance of nonthermal processes at the reactive site, and the efficient photo-induced electron transfer that plays a pivotal role in many photocatalytic reactions.ultrafast electron microscopy | single-site photocatalysis | titanium based photocatalyst | ulatrafast phenomena | time-resolved microscopy S ingle-site catalysts of both the thermally and photoactivated kind now occupy a prominent place in industrial-and laboratory-scale heterogeneous catalysis (1-8). Among the most versatile of these are the ones consisting of coordinatively unsaturated transition metal ions (Ti, Cr, Fe, Mn. . .) that occupy substitutional sites in well-defined, three-dimensionally extended, open-structure silicates of the zeolite type. The well-known and most widely used are the 4-or 5-coordinated Ti(IV) ions accommodated within the crystalline phase of silica, silicalite (9-14).Titanosilicates, especially, are used extensively both industrially and in the laboratory for a wide range of chemo-, regio-, and shapeselective oxidations of organic compounds (15-18). These single-site heterogeneous photocatalysts are quite distinct from those typified by TiO 2 , SrTiO 3 , and other titaniferous photocatalysts where the Ti(IV) ions are in 6-coordination; and where, in interpreting the processes involved in harnessing solar radiation, electronic band structure considerations hold sway in preference to the localized states (see, e.g., refs. 19, 20). It has been demonstrated (16-18, 21, 22) that single-site, coordinatively unsaturated Ti(IV)-centered photocatalysts are especially useful in the aerial oxidation of environmental pollutants in the photodegradation of NO (to N 2 and O 2 ), of H 2 O (to H 2 and O 2 ), and in the photocatalytic reduction of CO 2 to yield methanol. There is an exigent need to explore the precise nature of the electronic, temporal, and spatial changes accompanying the initial act of photoabsorption that sets in train the ensuing elementary chemical processes that are of vital environmental significance in, for example, the utilization of anthropogenic CO 2 as a chemical feedstock (23).Here, we report the use of 4D ultrafast electron microscopy (UEM) (24-26) to trace the spatiotemporal behavior of the Ti(IV) and O ...

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Section: Resultsmentioning

confidence: 95%

mentioning

confidence: 99%

On the dynamical nature of the active center in a single-site photocatalyst visualized by 4D ultrafast electron microscopy

Yoo

Thomas

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The relatively high thermal stability for JDF-L1 framework has drawn considerable attention for its potential of wider commercial applications in the future. 33) Based on previous work, the proposed fluoride mediated approaches were investigated to prepare the JDF-L1 type of some layered materials having sizably lamellar textures and further to unveil the role of fluorides in inducing crystal orientation growth of these structural analogues. The use of fluoride ions in low alkalinity and temperature systems leads to the formation of large lamellar JDF-L1 crystals and facilitates the isomorphous incorporation of Al or Fe heteroatoms, giving rise to morphological and structural changes.…”

Section: Introductionmentioning

confidence: 99%

Facile fluoride-mediated syntheses of layered (Al/Fe)-JDF-L1 materials featuring macromorphological square-sheet structures

Zhang

Liang

et al. 2020

J. Ceram. Soc. Japan

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This study aims to prepare the Jilin-Davy-Faraday, Layered solid no.1 (JDF-L1) type of layered materials and to elucidate the role of fluoride mineralizing agents in inducing crystal orientation growth featuring lamellar textures. The layered zeotypes synthesized by fluoride routes were characterized by several techniques, viz. Xray diffraction, fourier transform infrared spectroscopy, field emission scanning electron microscopy, 27 A1 and 29 Si magic angle spinning-nuclear magnetic resonance, etc. The JDF-L1 crystals were shown to crystallize in the uniform habit of square-sheet structures when the fluoride synthesis systems adopted a lower initial alkalinity and reduced crystallization temperatures. This method facilitated both the isostructural incorporation of tetrahedral [AlO 4 ] ¹ or [FeO 4 ] ¹ for unique SiO 4 units and also allowed the orientation growth of lamellar Al(Fe)-JDF-L1 crystals. Isomorphous substitution of trivalent Al or Fe was likely to perturb the JDF-L1 structure and hence caused the orthogonal multiplication of smaller lamellar subindividuals onto the basal crystal surfaces.

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“…They happen easily an ion exchange reaction with quaternary ammonium ions or other organic cation in water [7]. The acid treatment of Na + -titanosilicate can also produce Si-OH groups in interlayer surface by an ion exchange of exchangeable cations for H + .…”

Section: Introductionmentioning

confidence: 99%

Ion Exchange and Application of Layered Silicate

Park¹

2012

Ion Exchange Technologies

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Temperature-induced structural transformations of layered titanosilicate JDF-L1

Cited by 20 publications

References 12 publications

On the dynamical nature of the active center in a single-site photocatalyst visualized by 4D ultrafast electron microscopy

On the dynamical nature of the active center in a single-site photocatalyst visualized by 4D ultrafast electron microscopy

Facile fluoride-mediated syntheses of layered (Al/Fe)-JDF-L1 materials featuring macromorphological square-sheet structures

Ion Exchange and Application of Layered Silicate

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