Studying two-dimensional zeolites with the tools of surface science: MFI nanosheets on Au(111)

Kestell, John; Zhong, Jian; Shete, Meera; Waluyo, Iradwikanari; Sadowski, Jerzy; Stacchiola, Darı́o; Tsapatsis, Michael; Boscoboinik, J. Anibal

doi:10.1016/j.cattod.2016.07.015

Cited by 11 publications

(16 citation statements)

References 34 publications

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“…A photon energy of 750 eV was used in our studies, which was calibrated and referenced to the Fermi level of the Ru(0001) substrates. Infrared reflection absorption spectroscopy (IRRAS) experiments were carried out in a home-built UHV system equipped with a Bruker Vertex 70 spectrometer [17]. This system is also capable of polarization modulation (PM) IRRAS experiments at pressures up to 1 Atm.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Energy Level Shifts at the Silica/Ru(0001) Heterojunction Driven by Surface and Interface Dipoles

et al. 2016

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Charge redistribution at heterogeneous interfaces is a fundamental aspect of surface chemistry. Manipulating the amount of charges and the magnitude of dipole moments at the interface in a controlled way has attracted tremendous attention for its potential to modify the activity of heterogeneous catalysts in catalyst design. Two-dimensional ultrathin silica films with well-defined atomic structures have been recently synthesized and proposed as model systems for heterogeneous catalysts studies. R. Wlodarczyk et al. (Phys. Rev. B, 85, 085403 (2012)) have demonstrated that the electronic structure of silica/ Ru(0001) can be reversibly tuned by changing the amount of interfacial chemisorbed oxygen. Here we carried out systematic investigations to understand the underlying mechanism through which the electronic structure at the silica/Ru(0001) interface can be tuned. As corroborated by both in situ X-ray photoelectron spectroscopy and density functional theory calculations, the observed interface energy level alignments strongly depend on the surface and interfacial charge transfer induced dipoles at the silica/ Ru(0001) heterojunction. These observations may help to understand variations in catalytic performance of the model system from the viewpoint of the electronic properties at the confined space between the silica bilayer and the Ru(0001) surface. The same behavior is observed for the aluminosilicate bilayer, which has been previously proposed as a model system for zeolites.Jian-Qiang Zhong and Mengen Wang contributed equally to this work.

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Section: Experimental and Computational Methodsmentioning

confidence: 99%

Energy Level Shifts at the Silica/Ru(0001) Heterojunction Driven by Surface and Interface Dipoles

et al. 2016

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“…24 In the MFI nanosheets supported on Au(111), we observed a high frequency (HF) mode of 1247 cm −1 and a low frequency (LF) mode of 1174 cm −1 (Figure 1a), which are consistent with the measurements shown in a previous report. 25 Kestell et al previously suggested that the HF mode likely corresponds to Si−O−Si linkages between the pores, while the LF mode corresponds to internal linkages within the pores. 25 The peak position at 3724 cm −1 (Figure 1c) corresponds to SiOH groups.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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

et al. 2020

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Monitoring the effects of mild hydrothermal conditions, in situ, on siliceous materials remains challenging using surface science techniques, which often require electrically conductive substrates. The emergence of two-dimensional (2-D) siliceous nanomaterials deposited on metal single crystals overcomes this limitation. Here, we use infrared reflection absorption spectroscopy (IRRAS) to study the effects of mild hydrothermal conditions, in situ, on 2-D model systems, namely, all-Si MFI nanosheets supported on Au(111) and a polymorphous bilayer silicate supported on Ru(0001). We find that the formation of silanol groups (SiOH) occurs at 473 and 573 K under a H 2 O pressure of 3 mbar in the MFI nanosheets, but not in the polymorphous bilayer silicate. The effects of mild hydrothermal conditions are reversible in the MFI nanosheets and do not result in framework degradation. Implications shown here provide a fundamental understanding of the impact of mild hydrothermal conditions on the 2-D siliceous nanomaterials and serve as a starting point when considering these effects on three-dimensional (3-D) ones.

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“…The nanosheet-seeded MFI nanosheets were coated on an Au(111) crystal and placed in a high-vacuum chamber with BaF 2 windows that allow the passage of IR light to study phonon vibrations of materials and vibrational modes of adsorbed molecules, under a wide range of pressures and temperatures. Under high vacuum (~2 × 10 −4 Pa) and ambient temperature, three phonon modes at 1095, 1176, and 1248 cm −1 are obtained, corresponding to MFI framework vibrations ( 39 ). Exposure to xylene vapor yields additional vibrational modes, which arise from the aromatic ring vibrations of adsorbed xylene molecules.…”

Section: Resultsmentioning

confidence: 99%

Twin-free, directly synthesized MFI nanosheets with improved thickness uniformity and their use in membrane fabrication

et al. 2022

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Zeolite nanosheets can be used for the fabrication of low-defect-density, thin, and oriented zeolite separation membranes. However, methods for manipulating their morphology are limited, hindering progress toward improved performance. We report the direct synthesis (i.e., without using exfoliation, etching, or other top-down processing) of thin, flat MFI nanosheets and demonstrate their use as high-performance membranes for xylene isomer separations. Our MFI nanosheets were synthesized using nanosheet fragments as seeds instead of the previously used MFI nanoparticles. The obtained MFI nanosheets exhibit improved thickness uniformity and are free of rotational and MEL intergrowths as shown by transmission electron microscopy (TEM) imaging. The nanosheets can form well-packed nanosheet coatings. Upon gel-free secondary growth, the obtained zeolite MFI membranes show high separation performance for xylene isomers at elevated temperature (e.g., p -xylene flux up to 1.5 × 10 −3 mol m −2 s −1 and p -/ o -xylene separation factor of ~600 at 250°C).

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Studying two-dimensional zeolites with the tools of surface science: MFI nanosheets on Au(111)

Cited by 11 publications

References 34 publications

Energy Level Shifts at the Silica/Ru(0001) Heterojunction Driven by Surface and Interface Dipoles

Energy Level Shifts at the Silica/Ru(0001) Heterojunction Driven by Surface and Interface Dipoles

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

Twin-free, directly synthesized MFI nanosheets with improved thickness uniformity and their use in membrane fabrication

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