Reversible Formation of Silanol Groups in Two-Dimensional Siliceous Nanomaterials under Mild Hydrothermal Conditions

Norton, Angela M.; Kim, Donghun; Zheng, Weiqing; Akter, Nusnin; Xu, Yixin; Tenney, Samuel A.; Vlachos, Dionisios G.; Tsapatsis, Michael; Boscoboinik, J. Anibal

doi:10.1021/acs.jpcc.0c03875

Cited by 6 publications

(4 citation statements)

References 40 publications

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“…P-modified SPP, with an atomic ratio Si/P of 27, is a meso/microporous Mobil-5 (MFI)-type zeolite. Consisting of orthogonally intergrown single unit-cell MFI nanosheets (Scheme ), it is hydrothermally stable at moderate temperatures. − Its framework encompasses both conventional MFI micropores located within the 2 nm-thick nanosheets, as well as mesopores formed between the intergrown nanosheets and defined by the external surfaces of the MFI nanosheets, which are mostly terminated by (010) planes. The material shows a complex P-speciation, which varies depending on the extent of hydration.…”

Section: Introductionmentioning

confidence: 99%

P-Site Structural Diversity and Evolution in a Zeosil Catalyst

Jain

Tabassum

et al. 2021

J. Am. Chem. Soc.

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Phosphorus-modified siliceous zeolites, or P-zeosils, catalyze the selective dehydration of biomass derivatives to platform chemicals such as p-xylene and 1,3-butadiene. Water generated during these reactions is a critical factor in catalytic activity, but the effects of hydrolysis on the structure, acidity, and distribution of the active sites are largely unknown. In this study, the Psites in an all-silica self-pillared pentasil (P-SPP) with a low P-loading (Si/P = 27) were identified by solid-state 31 P NMR using frequency-selective detection. This technique resolves overlapping signals for P-sites that are covalently bound to the solid phase, as well as oligomers confined in the zeolite but not attached to the zeolite. Dynamic Nuclear Polarization provides the sensitivity necessary to conduct 29 Si-filtered 31 P detection and 31 P− 31 P correlation experiments. The aforementioned techniques allow us to distinguish sites with P−O−Si linkages from those with P−O− P linkages. The spectra reveal a previously unappreciated diversity of P-sites, including evidence for surface-bound oligomers. In the dry P-zeosil, essentially all P-sites are anchored to the solid phase, including mononuclear sites and dinuclear sites containing the [Si−O−P−O−P−O−Si] motif. The fully-condensed sites evolve rapidly when exposed to humidity, even at room temperature. Partially hydrolyzed species have a wide range of acidities, inferred from their calculated LUMO energies. Initial cleavage of some P− O−Si linkages results in an evolving mixture of surface-bound mono-and oligonuclear P-sites with increased acidity. Subsequent P− O−P cleavage leads to a decrease in acidity as the P-sites are eventually converted to H 3 PO 4 . The ability to identify acidic sites in Pzeosils and to describe their structure and stability will play an important role in controlling the activity of microporous catalysts by regulating their water content.

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Section: Introductionmentioning

confidence: 99%

P-Site Structural Diversity and Evolution in a Zeosil Catalyst

Jain

Tabassum

et al. 2021

J. Am. Chem. Soc.

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“…However, due to the structural complexity and diversity of 3D silica, the chemical properties of hydroxylated silica surfaces remain the subject of intensive investigations. Well-defined 2D-silica films prepared on metal surfaces represent new playgrounds for the mechanism studies of detailed hydroxylation processes, as well as for reactivity studies of different hydroxyls on silica …”

Section: Chemical Modifications Of the 2d-silicamentioning

confidence: 99%

“…It is generally accepted that hydroxylation of silica proceeds via the cleavage of siloxane bonds. , Unlike the defect-caused hydroxylation, significant isotopic mixing occurs in the electron irradiation stimulated hydroxylation as shown in Figure a, which may be caused by opening and reforming siloxane bonds within the film.…”

Section: Chemical Modifications Of the 2d-silicamentioning

confidence: 99%

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Two-Dimensional Ultrathin Silica Films

Zhong

Freund

2022

Chem. Rev.

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Two-dimensional (2D) ultrathin silica films have the potential to reach technological importance in electronics and catalysis. Several well-defined 2D-silica structures have been synthesized so far. The silica bilayer represents a 2D material with SiO2 stoichiometry. It consists of precisely two layers of tetrahedral [SiO4] building blocks, corner connected via oxygen bridges, thus forming a self-saturated silicon dioxide sheet with a thickness of ∼0.5 nm. Inspired by recent successful preparations and characterizations of these 2D-silica model systems, scientists now can forge novel concepts for realistic systems, particularly by atomic-scale studies with the most powerful and advanced surface science techniques and density functional theory calculations. This Review provides a solid introduction to these recent developments, breakthroughs, and implications on ultrathin 2D-silica films, including their atomic/electronic structures, chemical modifications, atom/molecule adsorptions, and catalytic reactivity properties, which can help to stimulate further investigations and understandings of these fundamentally important 2D materials.

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