Synthesis and structure of a layered titanosilicate catalyst with five-coordinate titanium

Roberts, Mark; Sankar, Gopinathan; Thomas, John Meurig; Jones, Richard H.; Du, Hong‐Bin; Chen, J.; Pang, Wenqin; Xu, Ruren

doi:10.1038/381401a0

Cited by 169 publications

(124 citation statements)

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“…1. The hydrated form is known to be a good selective oxidation, single-site heterogeneous catalyst when (27). Detailed comparison of the Bragg spots between the pristine and dehydrated JDF-L1 revealed a ∼4% decrease for the interplanar distance of the pristine's (100) and (010) planes with a change in the angle between a and b axis from 90°to ∼86.5°.…”

Section: Resultsmentioning

confidence: 99%

“…This transfer results in a separation of the titanium and the apical oxygen with a total displacement of up to ∼0.8 Å, which indicates a transformation from the original Ti 4+ =O 2− double bonding state to the dilated Ti 3+ −O 1− single bonding one. The nature of bonding (double or triple) in metal oxides of this type has been elucidated by Gray and colleagues (43), but in the structure studied here the double and single bond characters of the 5-coordinated Ti 4+ has been determined by X-ray methods (27,29). Future extension of our technique to the visualization of the active sites at the atomic level on other various catalytic materials will be beneficial to the de novo design of specific catalysts with improved efficiency as well as the fundamental elucidation of mechanisms in such complex systems.…”

Section: Resultsmentioning

confidence: 99%

“…The hydrated, pristine JDF-L1 is hydrothermally synthesized using previous protocols (27). A microliter drop of aqueous JDF-L1 suspensions was deposited on the 200-mesh holey carbon TEM grid (Electron Microscopy Science), followed by drying in the air for 2-3 d. The as-prepared structure of the tetragonal phase could change into the dehydrated phase with lower symmetry, due to the irreversible loss of water, when ethanol was used to disperse the sample onto the TEM grid.…”

Section: Methodsmentioning

confidence: 99%

“…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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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: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

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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“…Five-coordinate titanium active sites are relatively uncommon (given the propensity for titanium to adopt 4-or 6-coordinated geometries), hence the discovery of JDF-L1 48 was met with great excitement by the heterogeneous catalysis community. Despite this, there are no reports to date of such five-coordinate Ti species being catalytically superior to the tetrahedral Ti analogues (TS-1 and TiMCM-41), as it is highly likely that the pyramidal structure 48 of the active site in JDF-L1 hinders peroxide activation. Similarly octahedral and other 6-coordinate titanium species (such as ETS-4 and ETS-10) are coordinatively saturated, and as such will retard the interaction of oxidants or reagents, rendering the system comparatively inert.…”

Section: Introductionmentioning

confidence: 99%

Predictive design of engineered multifunctional solid catalysts

2014

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The ability to devise and design multifunctional active sites at the nanoscale, by drawing on the intricate ability of enzymes to evolve single-sites with distinctive catalytic function, has prompted complimentary and concordant developments in the field of catalyst design and in situ operando spectroscopy. Innovations in design-application approach have led to a more fundamental understanding of the nature of the active site and its mechanistic influence at a molecular level, that have enabled robust structure-property correlations to be established, which has facilitated the dextrous manipulation and predictive design of redox and solid -acid sites for industrially-significant, sustainable catalytic transformations.

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Microporous Titanosilicates and other Novel Mixed Octahedral-Tetrahedral Framework Oxides

Rocha

Anderson²

2000

Eur. J. Inorg. Chem.

289

158

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Stable microporous materials, such as zeolites, are extremely important for applications in catalysis, adsorption, ion‐exchange, and separation. In this review we describe a new class of stable microporous materials that involves novel mixed octhaedral‐tetrahedral framework oxides. The archetypal material is based on titanosilicates, although there is tremendous scope for introducing many other transition metals. These materials not only have potential novel applications in the fields normally associated with zeolites but also possible applications in the areas of optoelectronics, nonlinear optics, batteries, magnetic materials and sensors.

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Synthesis and structure of a layered titanosilicate catalyst with five-coordinate titanium

Cited by 169 publications

References 23 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

Predictive design of engineered multifunctional solid catalysts

Microporous Titanosilicates and other Novel Mixed Octahedral-Tetrahedral Framework Oxides

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