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1 In the format provided by the authors and unedited. DOI: /NMAT4941 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 Valtchev 1 and Svetlana Mintova 1, * 1 Laboratoire Catalyse et Spectrochimie (LCS) Normandie Univ, ENSICAEN, UNICAEN, CNRS, Caen, France. 2 Faculty of Chemistry and Pharmacy, University of Sofia, 1126 Sofia, Bulgaria. 3 Laboratoire de Cristallographie et Sciences des Matériaux (CRISMAT) Normandie Univ, ENSICAEN, UNICAEN, CNRS, Caen, France. These authors contributed equally. Correspondence to: svetlana.mintova@ensicaen.fr This PDF file includes: Computational model discussion Figures S1 to S11 Scheme S1 Tables S1 to S8 References: 2 NATURE MATERIALS 1

2 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 WO 2 (OH) 2 ) are introduced to replace two or four silanols, according to the following reactions: MFI-[(OH) 4 ] + W(OH) 4 MFI-[W] + 4 H 2 O, MFI-[(OH) 4 ] + WO(OH) 4 MFI-[WO] + 4 H 2 O, MFI-[(OH) 4 ] + WO 2 (OH) 2 MFI-[(O)WO 2 ] + 3 H 2 O. 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 W IV substituting Si in a framework position; MFI-[WO] includes W VI =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 E inc, 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 H 2 O, In addition, the relative energy, E rel, 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 O 2 molecules in the gas phase are determined. A positive value indicates that the process NATURE MATERIALS 2

3 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 W IV species are energetically less stable notably than W VI species, by more than 350 kj/mol, in agreement with the difference in the standard enthalpy of formation of W VI O 3 and W IV O 2 species, -369 and -253 kj/mol, for gas phase species and solid oxides, respectively. 1 Therefore, different species containing W VI, 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) 3 Si-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 W VI - containing 3R-rings, the process is energetically favorable. The formation of 3R-rings NATURE MATERIALS 3

4 with only Si as T-atoms is less favorable. Only the formation of the 3R-rings with WO 2 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 W VI -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)WO 2 ]. NATURE MATERIALS 4

5 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). NATURE MATERIALS 5

6 Figure S1. Raman spectra of nanosized (a) Si-MFI and (b) W-MFI zeolites in the range cm -1. Inset: spectra in the range cm -1. NATURE MATERIALS 6

7 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. NATURE MATERIALS 7

8 Figure S3. Solid-state 29 Si MAS NMR spectrum of micron-sized F-MFI zeolite crystals. NATURE MATERIALS 8

9 Figure S4. Solid-state 13 C NMR spectra of as-prepared (a) Si-MFI and (b) W-MFI nanosized zeolites. NATURE MATERIALS 9

10 Figure S5. Solid-state 1 H NMR spectra of as-synthesized (a) Si-MFI and (b) W-MFI nanosized zeolite samples. Inset: 2D NOESY 1 H NMR spectrum of as-synthesized W- MFI nanosized zeolites. NATURE MATERIALS 10

11 Figure S6. Solid state 23 Na NMR spectra of as-prepared (a) Si-MFI and (b) W-MFI nanosized zeolites. NATURE MATERIALS 11

12 T5-MFI-[W] T5-MFI-[WO] T11-MFI-[W] T11- MFI-[WO] T11-MFI-[(O)WO 2 ] 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). NATURE MATERIALS 12

13 Figure S8. Dynamic light scattering (DLS) curves of (a) W-MFI and (b) Si-MFI nanosized zeolites in water suspensions. NATURE MATERIALS 13

14 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. NATURE MATERIALS 14

15 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. NATURE MATERIALS 15

16 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. NATURE MATERIALS 16

17 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 Space volume (Å 3 ) group Si-MFI (1) (1) (calcined) (1) (6) Pnma W-MFI (calcined) (1) (1) (1) (6) (9) P2 1/n NATURE MATERIALS 17

18 Table S2. Results from 13 C NMR spectra of Si-MFI and W-MFI nanosized zeolites synthesized with tetrapropylammonium hydroxide (C2 and C3 peaks). NATURE MATERIALS 18

19 Table S3. Calculated energies (kj/mol) of the isolated models (dimer species and threemember rings). Models Initial OS(W) a CN(W) b E inc c d c d E rel E inc E rel Dimer species e Si(OH) 4 Gas Water (OH) 3 Si-O-Si(OH) 3 Si(OH) (OH) 3 Si-O-W(OH) 3 W(OH) 4 IV (OH) 3 Si-O- WO(OH) 4 VI W(O)(OH) 3 (OH) 3 Si-O- W(O) 2 (OH) WO 2 (OH) 2 VI Three-member rings e O[Si(OH) 3 ] 2 Gas Water 3R-[Si(OH) 2 ] Si(OH) R-[W(OH) 2 ] W(OH) 4 IV R-[W(O)(OH) 2 ] WO(OH) 4 VI R-[WO 2 ] WO 2 (OH) 2 VI a Oxidation state of W in the model systems; b Coordination number of W in the model systems; c Incorporation energies, E inc, of various species (shown in the column Initial), corresponding to the formation energy of the dimer or three-member ring; d Relative energies, E rel, of different W-containing systems calculated with respect to the energy of the systems obtained from WO(OH) 4 ; e All optimized isolated structures are shown in Fig. S8. NATURE MATERIALS 19

20 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 c E inc MFI- Periodic models e [(OH) 4 ] d c d E rel E inc E rel T11 T5 MFI-[Si] Si(OH) MFI-[W] W(OH) 4 IV MFI-[WO] WO(OH) 4 VI MFI-[(O)WO 2 ] WO 2 (OH) 2 VI a Oxidation state of W in the model systems; b Coordination number of W in the model systems; c Incorporation energies, E inc, of various species (shown in the column Initial) into the silanol nest at the corresponding T-atom position; d Relative energies, E rel, 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. NATURE MATERIALS 20

21 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 T Average value W=O distance NATURE MATERIALS 21

22 Table S6. Experimental and calculated (periodic models) vibrational frequency shifts (cm -1 ) of pyridine coordinated to tungsten in the W-MFI nanosized zeolite. a BE(P) Frequencies and shifts Experimental results Pyridine Lewis acid site (LAS) 1614 (35) 1578 (6) 1491 (12) 1454 (14) Brønsted acid site (BAS) 1597 (20) 1578 (6) (7) Calculated shifts MFI-[W] MFI-[WO] MFI-[(O)WO 2 ] a BE(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). NATURE MATERIALS 22

23 Table S7. Experimental and calculated (isolated models of the three-member rings) vibrational frequencies (cm -1 ) of pyridine coordinated to tungsten. a BE(P) Frequencies and shifts Experimental results Pyridine Lewis acid site (LAS) 1614 (35) 1578 (6) 1491 (12) 1454 (14) Brønsted acid site (BAS) 1597 (20) 1578 (6) (7) Calculated shifts 3R-[W(O)(OH) 2 ] R-[WO 2 ] NATURE MATERIALS 23

24 Table S8. Catalytic performance of W-MFI, silicalite-1 (W-Silicalite-1) and amorphous silica (W-SiO 2 ) loaded with 0.5 % W in styrene epoxidation. Samples k a TOF App TOF App (1h) b (2h) c W-MFI W-Silicalite W-SiO a Reaction 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. NATURE MATERIALS 24

25 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, , (1984). NATURE MATERIALS 25