I o ed. - media.nature.com · 3Laboratoire de Cristallographie et Sciences des Matériaux (CRISMAT) Normandie Univ, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France. ‡These authors contributed

In the format provided by the authors and unedited.

© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4941

NATURE MATERIALS | www.nature.com/naturematerials 1

Supporting Online Material for

One-pot synthesis of silanol-free nanosized MFI zeolite

Julien Grand,1,‡ Siddulu Naidu Talapaneni,1,‡ Aurélie Vicente,1 Christian Fernandez,1

Eddy Dib,1 Hristiyan A. Aleksandrov,2 Georgi N. Vayssilov,2 Richard Retoux,3

Philippe Boullay,3 Jean-Pierre Gilson,1 Valentin Valtchev1 and Svetlana Mintova1,*

1Laboratoire Catalyse et Spectrochimie (LCS)

Normandie Univ, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France. 2Faculty of Chemistry and Pharmacy, University of Sofia, 1126 Sofia, Bulgaria. 3Laboratoire de Cristallographie et Sciences des Matériaux (CRISMAT)

Normandie Univ, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France.

‡These authors contributed equally.

Correspondence to: [email protected]

This PDF file includes:

Computational model discussion

Figures S1 to S11

Scheme S1

Tables S1 to S8

References: 2

http://dx.doi.org/10.1038/nmat4941




Computational model discussion

In order to model the incorporation of tungsten moieties in the MFI type

framework, three types of tungsten-containing species, W(OH)4, WO(OH)4, and

WO2(OH)2) are introduced to replace two or four silanols, according to the following

reactions:

MFI-[(OH)4] + W(OH)4 → MFI-[W] + 4 H2O,

MFI-[(OH)4] + WO(OH)4 → MFI-[WO] + 4 H2O,

MFI-[(OH)4] + WO2(OH)2 → MFI-[(O)WO2] + 3 H2O.

The initial silanol nest, denoted MFI-[(OH)4], and the subsequent incorporation of W-

containing moieties are modeled at two T-atom positions in the MFI type structure,

T5 (straight channel) and T11 (intersection of the straight and sinusoidal channels).

The model structure MFI-[W] includes WIV substituting Si in a framework position;

MFI-[WO] includes WVI=O species with tungsten in a framework position. In the last

structure, reported in Table S3, the tungsten center in the O=W=O moiety is bound to

the zeolite framework by only two W-O-Si bridges.

The calculated energies for incorporation of tungsten-containing moieties,

denoted as Einc, and the energy for healing the silanol nest by interaction with Si(OH)4

resulting in the regular MFI-[Si] structure are reported in Table S3.

MFI-[(OH)4] + Si(OH)4 → MFI-[Si] + 4 H2O,

In addition, the relative energy, Erel, of the different tungsten-containing

frameworks with respect to the structure MFI-[WO] at the T11 position (intersection

of the straight and sinusoidal channels) and the calculated energy of water and O2

molecules in the gas phase are determined. A positive value indicates that the process





and the corresponding structure are energetically disfavored.

The binding energy (BE) of the pyridine adsorbate, is determined as

BE[PYR/MFI] = E[PYR/MFI] – E[MFI] – E[PYR],

where E[PYR/MFI] is the total energy of the zeolite system with a pyridine molecule

adsorbed on the active site, while E[MFI] and E[PYR] are the energies of the

corresponding zeolite structure and the pyridine molecule in the gas phase,

respectively. With the above definition, negative values of BE imply a favorable

interaction.

Both periodic and isolated cluster calculations show that WIV species are

energetically less stable notably than WVI species, by more than 350 kJ/mol, in

agreement with the difference in the standard enthalpy of formation of WVIO3 and

WIVO2 species, -369 and -253 kJ/mol, for gas phase species and solid oxides,

respectively.1 Therefore, different species containing WVI, also consistent with the

tungsten source used in the synthesis of W-MFI nanocrystals were computed. Isolated

models describing the formation of dimers with Si-O-W bonding from monomeric

species suggest that the process is exothermic for all simulation in both gas phase and

water (Table S3). For (OH)3Si-O-W(O)2(OH) species, the energy gain is -24 kJ/mol

(both in gas phase and water), essentially the same as for the formation of a Si-O-Si

moiety, while for the other types of W-containing species the energy increases from 9

to 26 kJ/mol (Table S3).

Additionally, the incorporation of W-containing moieties in a three-member

ring (Table S3) is considered where the tungsten species may bind to neighboring

silanol groups on the surface of zeolite nanocrystals. For two models of the WVI-

containing 3R-rings, the process is energetically favorable. The formation of 3R-rings





with only Si as T-atoms is less favorable. Only the formation of the 3R-rings with

WO2 species is an energetically unfavorable process both in gas phase and in water.

These results confirm that the formation of Si-O-W bonds with most of the

modeled WVI-containing species is slightly energetically favorable over the

formation of Si-O-Si bonds (Table S3).

The structures with the closest fit to the experimental results are MFI-[WO] at

T11 (at intersection of the straight and sinusoidal channels) and at T5 (in the straight

channel) positions since in those structures there is not any type of OH groups, neither

silanol, nor tungstenol (Table S4). The stability of the MFI-[WO] structures both in

T11 and T5 positions are notably higher than the that of the other two model

structures MFI-[W] and MFI-[(O)WO2].





Scheme S1. (a) Si-MFI and (b) W-MFI samples before (top panel) and after (bottom

panel) calcination: SiO-…HOSi silanol defects play the role of charge compensators

in the Si-MFI sample (left); water molecules play the stabilizing role in the W-MFI

sample explaining the insertion of the W with higher oxidation degree than the Si in

the MFI type framework (right).





1

Figure S1. Raman spectra of nanosized (a) Si-MFI and (b) W-MFI zeolites in the range

200-1500 cm-1. Inset: spectra in the range 900-1400 cm-1.





2

Figure S2 FTIR spectra of (a) Si-MFI and (b) W-MFI nanosized zeolites in comparison

with (c) defect free F-MFI micron-sized zeolite (diameter of 50 µm). Inset: SEM picture

of F-MFI micron-sized zeolite crystals.





3

Figure S3. Solid-state 29Si MAS NMR spectrum of micron-sized F-MFI zeolite crystals.





4

Figure S4. Solid-state 13C NMR spectra of as-prepared (a) Si-MFI and (b) W-MFI

nanosized zeolites.





5

Figure S5. Solid-state 1H NMR spectra of as-synthesized (a) Si-MFI and (b) W-MFI

nanosized zeolite samples. Inset: 2D NOESY 1H NMR spectrum of as-synthesized W-

MFI nanosized zeolites.





6

Figure S6. Solid state 23Na NMR spectra of as-prepared (a) Si-MFI and (b) W-MFI

nanosized zeolites.





7

T5-MFI-[W] T5-MFI-[WO]

T11-MFI-[W] T11- MFI-[WO]

T11-MFI-[(O)WO2]

Figure S7. Optimized periodic systems with W moieties in T11 and T5 positions in the

W-MFI zeolite structure. Color-coding: H (white), O (red), Si (grey), and W (yellow).





8

Figure S8. Dynamic light scattering (DLS) curves of (a) W-MFI and (b) Si-MFI

nanosized zeolites in water suspensions.





9

Figure S9. EDX-TEM analysis of (a) Si-MFI and (b) W-MFI nanosized zeolites. The

peak at ~8.0 keV is due to the copper grid.





10

Figure S10. Testing the leachability of the W-MFI catalyst during styrene epoxidation:

production of styrene oxide after the W-MFI was filtered off from the reaction batch after

1h reaction time; the leaching test was performed up to 8 h.





11

Figure S11. XRD patterns of newly synthesized W-MFI nanocrystals representing the

thermal stability of the materials treated at (a) 550, (b) 700, (c) 800, (d) 900 °C and (e)

under steaming.





12

Table S1. Unit cell parameters of calcined W-MFI and Si-MFI nanosized zeolites

calculated from powder diffraction data based on a Le Bail profile refinement and

Pseudo-Voigt profile function using the JANA2006 software.

Samples a (Å) b (Å) c (Å) ß (°) Unit cell

volume (Å3)

Space

group

Si-MFI

(calcined) 20.086(1) 19.918(1) 13.392(1) 90 5357.8(6) Pnma

W-MFI

(calcined) 19.906(1) 20.137(1) 13.394(1) 90.600(6) 5368.6(9) P21/n





13

Table S2. Results from 13C NMR spectra of Si-MFI and W-MFI nanosized zeolites

synthesized with tetrapropylammonium hydroxide (C2 and C3 peaks).





14

Table S3. Calculated energies (kJ/mol) of the isolated models (dimer species and three-

member rings).

Models Initial OS(W)a CN(W)b Eincc Erel

d Eincc Erel

d

Dimer speciese Si(OH)4 Gas Water

(OH)3Si-O-Si(OH)3 Si(OH)4 -23 -24

(OH)3Si-O-W(OH)3 W(OH)4 IV 4 -59 358 -36 382

(OH)3Si-O-

W(O)(OH)3

WO(OH)4 VI 5 -34 0 -36 0

(OH)3Si-O-

W(O)2(OH)

WO2(OH)2 VI 4 -24 38 -24 3

Three-member ringse O[Si(OH)3]2 Gas Water

3R-[Si(OH)2] Si(OH)4 8 -6

3R-[W(OH)2] W(OH)4 IV 4 -40 363 -22 389

3R-[W(O)(OH)2] WO(OH)4 VI 5 -20 0 -28 0

3R-[WO2] WO2(OH)2 VI 4 21 70 8 27 aOxidation state of W in the model systems; bCoordination number of W in the model

systems; cIncorporation energies, Einc, of various species (shown in the column Initial),

corresponding to the formation energy of the dimer or three-member ring; dRelative

energies, Erel, of different W-containing systems calculated with respect to the energy of

the systems obtained from WO(OH)4; eAll optimized isolated structures are shown in Fig.

S8.





15

Table S4. Calculated energies (kJ/mol) of the periodic systems modeled with W moieties

in the W-MFI structure (T11 and T5 positions).

Models Initial OS(W)a CN(W)b Eincc Erel

d Eincc Erel

d

Periodic modelse MFI-

[(OH)4]

T11 T5

MFI-[Si] Si(OH)4 13 16

MFI-[W] W(OH)4 IV 4 64 372 56 361

MFI-[WO] WO(OH)4 VI 5 120 0 118 -5

MFI-[(O)WO2] WO2(OH)2 VI 4 197 - a Oxidation state of W in the model systems; b Coordination number of W in the model

systems; c Incorporation energies, Einc, of various species (shown in the column Initial)

into the silanol nest at the corresponding T-atom position; d Relative energies, Erel, of

different W-containing systems calculated with respect to the energy of MFI-[WO]-T11

system for periodic models; e all optimized periodic structures are shown in Fig. S7.





16

Table S5. W-O and Si-O bond lengths (Å), and bond W-O-Si angles (degrees) in the W-

MFI, and the corresponding values for Si-O and Si-O-Si in the Si-MFI determined from

the optimized structures in the periodic calculations.

W-MFI Si-MFI

W-O-Si

W-O

Si-O

Si-O-Si

Si-O

T-site T5 T11 T5 T11 T5 T11 T5 T11 T5 T11

129 132 1.96 1.85 1.62 1.65 148 151 1.61 1.61

136 137 1.91 1.88 1.63 1.63 142 151 1.61 1.61

151 149 1.91 1.90 1.64 1.60 157 156 1.61 1.61

155 130 1.84 1.97 1.65 1.64 158 157 1.62 1.62

Average value 143 137 1.91 1.90 1.64 1.63 151 154 1.61 1.61

W=O distance

1.73 1.74





17

Table S6. Experimental and calculated (periodic models) vibrational frequency shifts

(cm-1) of pyridine coordinated to tungsten in the W-MFI nanosized zeolite.

aBE(P) Frequencies and shifts

Experimental results

Pyridine2 1584 1581 1483 1442

Lewis acid site (LAS) 1614 (35) 1578 (6) 1491 (12) 1454 (14)

Brønsted acid site (BAS) 1597 (20) 1578 (6) - 1446 (7)

Calculated shifts

MFI-[W] -47 18 -50 -1 5

MFI-[WO] -57 32 0 10 17

MFI-[(O)WO2] -38 32 7 21 21 aBE(P): Binding energy (BE) of the pyridine determined as BE[PYR/MFI] =

E[PYR/MFI] - E[MFI] - E[PYR], where E[PYR/MFI] is the total energy of the zeolite

system with pyridine molecule adsorbed at the active site of the structure, while E[MFI]

and E[PYR] are the energies of the corresponding zeolite structure and pyridine molecule

in gas phase, respectively (negative values of BE implies favorable interactions).





18

Table S7. Experimental and calculated (isolated models of the three-member rings)

vibrational frequencies (cm-1) of pyridine coordinated to tungsten.

aBE(P) Frequencies and shifts

Experimental results

Pyridine2 1584 1581 1483 1442

Lewis acid site (LAS) 1614 (35) 1578 (6) 1491 (12) 1454 (14)

Brønsted acid site (BAS) 1597 (20) 1578 (6) - 1446 (7)

Calculated shifts

3R-[W(O)(OH)2] -60 20 2 9 8

3R-[WO2] -108 30 1 8 15





19

Table S8. Catalytic performance of W-MFI, silicalite-1 (W-Silicalite-1) and amorphous

silica (W-SiO2) loaded with 0.5 % W in styrene epoxidation.

Samples ka TOFApp

(1h)b

TOFApp

(2h)c

W-MFI 0.0267 67.9 38.9

W-Silicalite-1 0.0029 4.7 2.7

W-SiO2 0.0015 1.2 1.4 aReaction rate constant (s-1, order is 1) after 1 hour of reaction, b Apparent Turn Over

Frequency (h-1) after 1 hour of reaction, c Apparent Turn Over Frequency (h-1) after 2

hours of reaction.





20

References

1. M. W. Chase Jr., in NIST-JANAF Thermochemical Tables, Fourth Edition, J. Phys.

Chem. 9, 1, (1998).

2. K. N. Wong, S. D. Colson, The FT-IR spectra of pyridine and pyridine-d5 J. Mol.

Spectr. 104, 129-151, (1984).


Documents

I o ed. - media.nature.com · 3Laboratoire de Cristallographie et Sciences des Matériaux (CRISMAT) Normandie Univ, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France. ‡These authors contributed