Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance <sup>119</sup>Sn Precursors

Gunther, William R.; Michaelis, Vladimir K.; Caporini, Marc A.; Griffin, Robert G.; Román‐Leshkov, Yuriy

doi:10.1021/ja502113d

Cited by 142 publications

(179 citation statements)

References 46 publications

Supporting

Mentioning

169

Contrasting

Unclassified

Order By: Relevance

“…Hwang et al (92) also showed with 19 F- 119 Sn CP MAS NMR that even after calcination, Sn-Beta samples may contain some fluorine that associates with hydrated Sn sites. Recently, hyperpolarization techniques, such as DNP, have been successfully applied to characterize natural abundance 119 SnBeta samples (93). This technique allows transfer of the polarization from an exogenous biradical containing unpaired electrons to the Sn sites in the sample through the assistance of microwave radiation and a glassing agent.…”

Section: Direct Detection Of the Metal Centermentioning

confidence: 99%

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

Luo

Lewis

Román‐Leshkov

2016

Annu. Rev. Chem. Biomol. Eng.

Self Cite

151

136

View full text Add to dashboard Cite

Zeolites containing Sn, Zr, Hf, Nb, or Ta heteroatoms are versatile catalysts for the activation and conversion of oxygenated molecules owing to the unique Lewis acid character of their tetrahedral metal sites. Through fluoride-mediated synthesis, hydrophobic Lewis acid zeolites can behave as water-tolerant catalysts, which has resulted in a recent surge of experimental and computational studies in the field of biomass conversion. However, many open questions still surround these materials, especially relating to the nature of their active sites. This lack of fundamental understanding is exemplified by the many dissonant results that have been described in recent literature reports. In this review, we use a molecular-based approach to provide insight into the relationship between the structure of the metal center and its reactivity toward different substrates, with the ultimate goal of providing a robust framework to understand the properties that have the strongest influence on catalytic performance for the conversion of oxygenates.

show abstract

Section: Direct Detection Of the Metal Centermentioning

confidence: 99%

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

Luo

Lewis

Román‐Leshkov

2016

Annu. Rev. Chem. Biomol. Eng.

Self Cite

151

136

View full text Add to dashboard Cite

show abstract

“…[17][18][19][20] Although recent experimental studies evidence a considerable heterogeneity of Sn speciation in different Sn-Beta zeolites, [21][22][23] there is an agreement that the active sites are partially hydrolyzed lattice Sn sites bearing an extraframework OH ligand (open Sn sites). [24][25][26][27][28] DFT calculations show that the cooperative action between the strong Lewis acid sites and neighboring protondonating groups results in a favorable reaction path for the hydride shift reaction, which is the key step in sugar isomerization. 20,[29][30][31][32][33][34] Although theory predicts that confinement should have only minor influence on the intrinsic reactivity of the cooperative reaction centers, zeolite topology will strongly affect the adsorption and diffusion of carbohydrates in the micropores.…”

Section: Introductionmentioning

confidence: 99%

Influence of pore topology on synthesis and reactivity of Sn-modified zeolite catalysts for carbohydrate conversions

Graaff

Tempelman

Pidko

et al. 2017

Catal. Sci. Technol.

View full text Add to dashboard Cite

A range of Sn-modified MWW, MFI, MOR and Beta zeolites were prepared by a post-synthetic Sn functionalization method and their catalytic properties for sugar conversions were evaluated. The focus of this work was to understand the effect of micropore dimensions and additional mesoporosity on the Sn incorporation and on the catalytic properties. The post-synthetic approach, which involves aciddealumination of the parent zeolite followed by SnCl 4 grafting, is highly efficient for the selective incorporation of lattice Sn sites in wide-pore Beta and MOR zeolites. The modification of the medium-pore MWW and MFI is impaired by the more difficult dealumination and hence the lower efficiency of the Sn incorporation. Hierarchical structuring of the zeolites allows the increase of the Sn loading in the final zeolites. The catalytic properties were assessed in the isomerization and retro-aldolization reactions of glucose and the conversion of 1,3-dihydroxyacetone to methyl lactate. The catalytic results depend strongly on the structural and topological properties of the catalysts as well as on the reactant. Glucose isomerization carried out at a relatively low temperature is mainly limited by strong adsorption of carbohydrates to the active sites. This explains why zeolite nanostructuring had little effect on the catalyst activity, which instead depends mainly on the zeolite topology and the nature of the reactive Sn centers. The influence of pore size is most pronounced for Sn-MWW and Sn-MFI zeolites which are inactive in glucose-to-fructose isomerization, but perform in the higher-temperature retro-aldolization of carbohydrates with an activity similar to that of Sn-Beta. Because of the limited accessibility of the Sn sites inside the 1D MOR pore system, Sn-MOR catalysts were only moderately active in all probe reactions considered.

show abstract

“…However, the other two chemical shifts (at -670 and -728 ppm) are ascribed to hydrated, Sn(IV) species in Td sites (closed and/or open sites). 11,22,23 There are, however, somewhat broader features in 6%CoSn-700C sample (Fig. 3A, curve b) suggesting also the presence of multiple Sn environments in this sample.…”

Section: Sn Mas Nmrmentioning

confidence: 83%

“…119 Sn MAS-NMR has been used extensively for probing the nature of Sn species in zeolites, [21][22][23] and these interpretations can be rationally extended for probing analogous species in AlPO-5. In Fig.…”

Section: Sn Mas Nmrmentioning

confidence: 99%

Design and control of Lewis acid sites in Sn-substituted microporous architectures

et al. 2016

View full text Add to dashboard Cite

Monometallic and bimetallic tin-containing framework architectures have been prepared by hydrothermal methods. Structural and spectroscopic techniques were used to probe the nature of the solid-acid sites, at the molecular level, using a combination of XRD, DR UV-Vis, solid state MAS NMR ( 119 Sn, 27 Al and 31 P) and XAFS. The nature and strength of the solidacid sites were experimentaly probed by FT-IR spectroscopy using CD3CN as a probe molecule. To elucidate further the localstructure, the structural characteristics of the Sn sites were probed using DFT calculations, with a view to rationalising the experimental findings. These detailed structural and spectroscopic studies revealed the presence of multiple Sn environments, with the monometallic SnAlPO-5 catalyst displaying a greater number of tetrahedral Sn(IV) active centres. These framework Sn(IV) centres generated stong Lewis acid sites, when compared with their bimetallic Co-Sn analogue, thereby affording attractive possibilities for modulating catalytic reactivity. IntroductionTetrahedral (Td) sites in microporous solids are widely reported as catalytic active centres in selective oxidation and acidcatalysed transformations, 1-4 of which Ti in TS-1, 5 Fe in ZSM-5 6 and Co in AlPO-5 7 are significant examples. Controlling the nature of these active sites allows one to tune the Lewis 8 and Brønsted acidity, 9 and regulate redox 10 centres for oxidation catalysis. The addition of a second heteroatom allows for further optimisation of these properties, as well as influencing the coordination geometry of the initial heteroatom. [2][3][4] The incorporation of Sn into zeolitic 11 and non-zeolitic 1,4 architectures has received significant attention for its promising performance in Baeyer-Villiger oxidations. 11 The activity of these systems was correlated with the presence of Sn in Td sites, with well isolated Lewis acidic centres, which can be used for a wide range of catalytic reactions. [11][12][13] The synthetic findings were supported by a large number of characterization techniques, including DR UV-Vis, 119 Sn MAS NMR and in situ IR spectroscopy. 11,14 Although such materials could be expected to show significant catalytic functionality, the incorporation of Sn into AlPO-5 frameworks in Td sites is, however, very limited and poorly understood.This work focuses on the isomorphous substitution of P(V) with Sn (IV) within AlPO-5 using a modified hydrothermal preparation method. 4 Cobalt (Co 2+ /Co 3+ ) ions can be simultaneously introduced into the AlPO-5 architecture 2,3,15 by the substitution of (Al 3+ ) sites. Recently, a combined DFT and EXAFS study demonstrated the potential of effecting catalytic synergy in Co−Ti bimetallic nanoporous frameworks. 16 However, the prospects of introducing a relatively heavier element like Sn, alongside a redox transition-metal such as Co, could pave the way for probing bifunctional catalytic transformations. Nevertheless, the structural and spectroscopic features of such a system needs to be probed in meticulous detail...

show abstract

Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance ¹¹⁹Sn Precursors

Cited by 142 publications

References 46 publications

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

Influence of pore topology on synthesis and reactivity of Sn-modified zeolite catalysts for carbohydrate conversions

Design and control of Lewis acid sites in Sn-substituted microporous architectures

Contact Info

Product

Resources

About

Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance 119Sn Precursors

Cited by 142 publications

References 46 publications

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

Influence of pore topology on synthesis and reactivity of Sn-modified zeolite catalysts for carbohydrate conversions

Design and control of Lewis acid sites in Sn-substituted microporous architectures

Contact Info

Product

Resources

About

Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance ¹¹⁹Sn Precursors