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1 DOI: /NCHEM.1662 A family of zeolites with controlled pore size prepared using a top-down method Wieslaw J. Roth 1, Petr Nachtigall 2, Russell E. Morris 3, *, Paul S. Wheatley, 3 Valerie Seymour, 3 Sharon E. Ashbrook, 3 Pavla Chlubná 1, Lukáš Grajciar 2, Miroslav Položij 2, Arnošt Zukal 1, Oleksiy Shvets 4, and Jiří Čejka 1* 1 Department of Synthesis and Catalysis, J. Heyrovský Institute of Physical Chemistry Academy of Sciences of Czech Republic, v.v.i., Dolejškova 3, Prague 8 (Czech Republic) 2 Department of Physical and Macromolecular Chemistry, Faculty of Sciences, Charles University, Hlavova 8, Prague 2 (Czech Republic) 3 EaStCHEM School of Chemistry, University of St Andrews, St Andrews KY16 9ST (Scotland) 4 L.V. Pisarzhevskiy Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 pr. Nauky, Kyiv (Ukraine) Supporting Information Contents S1 Synthesis of zeolites page 2 S2 Characterisation of zeolites page 3 S2.1 Structure Solution and Rietveld Refinement of IPC- 4 page 3 S2.2 Structure Solution and Refinement of IPC- 2 page 8 S2.3 Calculations page 12 S2.4 Solid State NMR page 14 S3 Analysis of (Al)IPC- 2 and (Al)IPC- 4 page 17 NATURE CHEMISTRY 1

2 S1 Synthesis of zeolites Synthesis of zeolite UTL and the layered precursor IPC- 1P Synthesis of UTL Preparation of the UTL zeolites was carried using this method. The molar composition of the reaction mixtures was in the range SiO2: GeO2: ROH/Br:30H2O, where ROH is the SDA, (6R,10S)- 6,10- dimethyl- 5- azoniaspiro[4,5] decane hydroxide. Typically, the SDA was dissolved in the distilled water. Then crystalline germanium oxide was added, and the mixture was stirred at room temperature until a clear solution was obtained. After this, silica (Aerosil 300) was added to the obtained solution, and the mixture was stirred at room temperature for 30 min. The resulting fluid gel was charged into 25 ml Teflon- lined autoclaves and heated at 175 o C for 2-23 days under agitation ( 25 rpm). Usually, for appropriate mixing of the reaction mixture, a small Teflon cylinder was inserted into the autoclave. The solid products obtained after preset synthesis times were recovered by filtration, washed out with distilled water, and dried Table 1. To remove the SDA, the as- synthesized zeolites were calcined in a stream of air at 550 o C for 6 h with a temperature ramp of 1 o C/min. Calcined UTL was hydrolyzed in 0.1 M HCl with w/w ratio of about 200/1 at temperature near boiling in a plastic bottle, for overnight. The solid was isolated by filtration and centrifugation, washed with water and dried in air for overnight. Calcination of IPC- 1P to produce IPC- 1 was carried out as above. XRD showed a dominant peak at ca 9.8 deg and broad, much weaker peaks, in positions corresponding to initially interlayer reflections, indicating largely disordered layered structure. Synthesis of IPC- 2 A 0.5 g sample of IPC- 1P in 10 ml of 1 M HNO3 solution containing 0.1 g of Si(CH 3 ) 3 (OCH 2 CH 3 ) 2 was heated at 170ºC for 16 hr. The product was isolated by centrifugation, washed and calcined at 540 C for 2 hrs. Synthesis of IPC- 4 Treatment with octylamine and IPC- 4 preparation. A 0.3 g sample of the precursor IPC- 1P was mixed with 20 g of octylamine, heated at 70 ºC for several hours and then stirred at room temperature for overnight. The solid was isolated by centrifugation, decantation of the supernatant and drying in an open tube in air at 90 ºC. The sample was calcined as above and designated as IPC- 4 as having the unique XRD pattern with relatively narrow peaks. NATURE CHEMISTRY 2

3 S2 Characterization of zeolites X- ray Diffraction The crystallinity of samples under study was determined by powder X- ray diffraction on a Bruker AXS D8 Advance diffractometer with a Vantec- 1 detector in the Bragg- Brentano geometry using CuKα radiation. All samples were gently ground to limit the effect of preferential orientation of individual crystals. Adsorption isotherms Adsorption isotherms of nitrogen at 196 C were determined using an ASAP 2020 (Micromeritics) static volumetric apparatus. Before adsorption experiments the samples were degassed under turbomolecular pump vacuum at the temperature of 250 o C for 8 h. S2.1 Structure Solution and Rietveld Refinement of IPC- 4 On synthesis of the material the structure was solved simply by comparing the experimental X- ray powder pattern of IPC- 4 with the computed patterns for the four possible ways in which the layers can be connected in a fully coordinated zeolite (see Figure S1). A Le Bail was then carried out against the experimental data to confirm that the calculated unit cell was correct. This provided an excellent fit and demonstrated that there were no other crystalline impurities in the sample. A Rietveld refinement was carried out against the experimental X- ray diffraction data using the DFT optimised unit cell and atomic positions (Table S.2) as the starting model. The refinement converged satisfactorily. However, close inspection of the atomic positions however, indicated that the bond distances and angles in the SiO 4 tetrahedra had become significantly distorted (Si- O range from ~1.5 to ~1.9 Å). This is rather more than would be expected in a pure silica zeolite material and so bond angle and bond distance restraints (Si- O distance restrained to 1.60Å and O- O distances along the edges of SiO 4 tetrahedra restrained to 2.55Å were applied with a weighting factor of 50 in GSAS). The structural model refinement then converged to a chemically sensible structure with bond distances (Si- O range from 1.57 to 1.69 Å) with only a small increase in the residuals to final values of R F 2 of and wr p and R p of and respectively. The isotropic displacement factors (Uiso) were constrained to be equal for each atom type and refined to 0.041(4) for Si and 0.047(4) for O. NATURE CHEMISTRY 3

4 ac plane projection ab plane projection a b C2/m E rel = 0 Pm E rel = 105 c P1 E rel = 109 d Pm E rel = 186 Figure S1 The four possible condensation ways of IPC- 1P layers into fully connected, 3D zeolites (IPC- 4 family). There are two possible projections in the ac plane (a column index) and two in the ab plane (a row index). All combinations of these projections are possible leading to the four different calculated powder diffraction patterns. The pattern for IPC- 4 is shown in part a. The relative energies (in kj mol - 1 ) as well as the symmetry of each of four predicted zeolites is also given; complete structure are supplied in cif format. NATURE CHEMISTRY 4

5 Table S1 Structural parameters for IPC- 4 after Rietveld Refinement against X- ray diffraction data Unit cell a = (6) b = (2) c = (2) Å β = (2) o Space Group Cm Atom Name x y z Si (13) (14) (20) Si (11) (16) (20) Si (13) (14) (20) Si (14) (14) (20) Si (13) (13) (20) Si (11) (16) (19) Si (11) (15) (21) Si (14) (15) (21) Si (13) (13) (21) Si (12) (15) (19) Si (17) (26) Si (19) (28) Si (17) (25) Si (16) (26) Si (16) (25) Si (17) (25) Si (18) (28) Si (18) (28) Si (18) (28) Si (17) (26) O (17) (9) 0.366(4) O (18) (18) (22) O (13) (23) 0.942(4) O (14) (18) 0.633(4) O (18) (9) (28) O (22) (21) (31) O (23) (19) (20) O (16) (9) (32) O (19) (9) (29) O (20) (18) (32) O (17) (9) 0.639(4) O (21) (31) (21) O (18) (9) (31) O (20) (9) (23) O (16) (26) (31) O (22) (25) (23) O (10) (30) (32) O (10) (32) 0.327(4) O (19) (9) (30) O (17) (9) (34) O (20) (19) (34) NATURE CHEMISTRY 5

6 O (14) (9) (33) O (25) (27) (22) O (19) (17) (20) O (14) (24) 0.327(4) O (19) (24) O (20) (28) O (19) (27) O (19) (25) O (24) (24) O (25) (24) O (24) (4) O (20) (31) O (17) (24) O (26) (33) Table S2 Structure of IPC- 4 optimised at the DFT level Unit cell a = b = c= Å β= o Spacegroup Cm Atom Name x y Z Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si NATURE CHEMISTRY 6

7 O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O NATURE CHEMISTRY 7

8 Figure S2 Comparison of Rietveld- (red) and DFT- derived (green) structural models for IPC- 4. S2.2 Structure Solution and Refinement of IPC- 2 Essentially the same methodology was used to solve the structure of IPC- 2. The four possible ways of connecting the layers, but this time with the inclusion of an S4R unit, were modelled and the structure of IPC- 2 was solved simply by comparing the experimental X- ray powder pattern of IPC- 2 with the computed patterns for the four possible ways in which the layers can be connected in a fully coordinated zeolite (Figure S3). The computation indicated that there should be a reduction in symmetry compared with the parent UTL and this was confirmed by the experimental XRD pattern. A Le Bail was then carried out against the experimental data to confirm that the calculated unit cell was correct. This provided an excellent fit and demonstrated that there were no other crystalline impurities in the sample. From this point a Rietveld refinement was carried out against the experimental X- ray diffraction data using the DFT optimised unit cell and atomic positions (Table S4) as the starting model. The refinement converged satisfactorily to R F 2 of wrp = and Rp = respectively. Bond distance restraints (Si- O distance restrained to 1.60Å and O- O distances along the edges of SiO 4 tetrahedra restrained to 2.55Å applied with a weighting factor of 100 in GSAS). The isotropic displacement parameters (Uiso) values were fixed as above. The structural model refinement then converged to a chemically sensible structure. However, the fits still shows evidence of significant asymmetry in the low NATURE CHEMISTRY 8

9 angle peaks, and the overall fit is not quite as good as we might expect. However, the connectivity is well established, and the other characteriation (adsorption, NMR) are all in agreement. ab plane projection ac plane projection a P- 1 E rel = 0 b Pm E rel = 294 c P1 E rel = 282 d Pm E rel = 531 Figure S3 The four possible condensation ways of IPC- 1P layers via S4R into fully connected, 3D zeolites (IPC- 2 family). There are two possible projections in the ac plane (a column index) and two in the ab plane (a row index). All combinations of these projections are possible leading to the four different calculated powder diffraction patterns. The pattern for IPC- 2 is shown in part a. The relative energies (in kj mol - 1 ) as well as the symmetry of each of four predicted zeolites is also given; complete structure are supplied in cif format. Table S3 Structural parameters for IPC- 2 after Rietveld Refinement against X- ray diffraction data Unit cell a = (4) b = (8) c = (5) Å α = (30) β = 89.88(9) γ = (5) Space Group P - 1 NATURE CHEMISTRY 9

10 Atom Name x Y z Si (20) (20) (18) Si (20) (21) (18) Si (22) (20) (18) Si (21) (20) (21) Si (20) (21) (21) Si (21) (20) (21) Si (20) (19) (20) Si (21) (24) (21) Si (20) (23) (24) Si (19) (12) (18) Si (19) (11) (15) Si (20) (20) (20) Si (21) (24) (24) Si (20) (22) (24) Si (19) (21) (19) Si (21) (20) (23) Si (20) (22) (21) O (4) 0.486(4) (25) O (23) 0.501(4) 0.636(4) O (26) (22) (23) O (29) (21) (26) O (4) (21) (29) O (28) (23) 0.603(4) O (27) (26) (28) O (33) 0.792(4) 0.365(4) O (28) (26) (19) O (4) (30) (28) O (25) (18) (26) O (20) (20) (31) O (23) 0.208(4) (25) O (29) (32) 0.562(4) O (20) 0.163(4) (24) O (24) (29) (24) O (30) 0.181(4) (18) O (31) 0.161(4) 0.224(4) O (20) (27) (32) O (20) (28) (34) O (4) (31) (25) O (34) (25) (26) O (4) (28) (20) O (4) (22) (16) O (32) 0.887(4) (20) O (25) (35) (34) O (20) (21) 0.293(4 O (22) (27) (31) O (4) (29) 0.702(4) NATURE CHEMISTRY 10

11 O (21) (31) (26) O (34) (26) 0.976(4) O (31) (25) (30) O (20) (22) 0.242(4) O O Table S4 Structure of IPC- 2 optimised at the DFT level Unit cell a = b = c = Å α = β = γ = Spacegroup P- 1 Atom Name x Y z Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si O O O O O O O O O O O O O O O O O O O O O NATURE CHEMISTRY 11

12 O O O O O O O O O O O O O O Figure S4 Comparison of Rietveld- (red) and DFT- derived (green) structural models for IPC- 2. S2.3 Calculations The structure of IPC- 1P layer silicate used as a model of the zeolite layered framework was derived from the parent UTL[1] zeolite; the D4R bridges connecting dense layers of UTL were removed and broken T- O- T connections were terminated with silanols. There are 8 silanol groups in the unit cell, 4 on each side. To study the stacking of the IPC- 1P layers a periodic model of two IPC- 1P layers connected NATURE CHEMISTRY 12

13 via silanol H- bonds, an IPC- 1P silicate bilayer, was adopted. As the simulation cell of the IPC- 1P bilayer, the experimental UTL monoclinic unit cell (a = , b = , c = Å, α = γ = 90 and β = and V = Å) was used. The structure of new zeolites obtained by a condensation of IPC- 1P layers was investigated as schematically depicted in Fig. S5: (i) There are four possible condensation patterns for IPC- 1P lamellae as indicated in the figure; they are obtained by shifting subsequent layers by 0 and ½ (in fractional units) along b and c vectors and by appropriate adjustment of vector a. (ii) Structures of such 3- D zeolites were fully optimized (both lattice parameters and atom positions) using periodic model. (iii) The symmetry of obtained zeolite was determined and structure was symmetrized. The effect of octylamine (OCA) on the ordering of IPC- 1P layers was also investigated computationally. One molecule of OCA was placed in a double UC (enlarged along c vector) between two IPC- 1P layers; geometry optimization (relaxing positions of all ions) was performed for several initial placements of OCA between two IPC- 1P layers along the c direction; both initial arrangements of subsequent layers, corresponding to CDO and FER projections (Fig. S1), were considered. The structure of new zeolites obtained from IPC- 1P layers upon insertion of diethoxy dimethyl silane and calcinations was investigated as above; the S4R unit was inserted between layers in one of four possible connections resulting in condensation of all silanol groups. The geometry of each of four possible new zeolites was optimized at the DFT level. The structures of new zeolites formed from IPC- 1P layered material were investigated using density functional theory (DFT) and a periodic model. Calculations were carried out using projector augmented wave approximation (PAW) of Blöchl 2 as implemented by Kresse and Joubert 3 and PBE exchange- correlation functional 4. Standard PAW for O, Si and H with ENMAX values of 400, 245 and 250 ev, respectively, were used together with 800 ev kinetic energy cutoff for the plane wave basis set. Brillouin- zone sampling was restricted to the Γ point. The geometry optimizations were considered to be converged when the forces on atoms were less than 0.01 ev Å 1. All calculations were carried out with the VASP program. 5 Non- local exchange correlation functional vdw- DF2 was used as implemented in VASP program for the calculations on inter- layer interactions 6. NATURE CHEMISTRY 13

14 Figure S5. Schematic representation of UTL IPC- 1P IPC- 4 transformation; view along c and b crystallographic direction shown in parts a and b, respectively. Adjacent IPC- 1P layers can be shifted by 0 and ½ (in fractional units) along b and c vectors and upon the condensation four different new zeolite structures can be obtained. Projection in ab plane (part a) shows that either FER (altering R10 and R6 channels) or CDO (only R8 channels) projections can be obtained. Similarly, projection in ac plane shows either altering R8 and R6 channels or only R7 channels. The condensation without shifts in b and c directions (FER and R8- R6 projections in ab and ac planes, respectively) leads to the zeolite that is the most stable of four new zeolites considered and that is characterized by diffraction pattern in excellent agreement with experimentally observed one for IPC- 4 zeolite. S2.4 Solid State NMR Solid- state NMR spectra were acquired using Bruker Avance III 400 and 600 MHz spectrometers equipped with widebore 9.4 T and 14.1 T magnets, respectively. Powdered samples were packed into conventional 4 mm ZrO 2 rotors and the MAS rate used was 10 khz. Conventional 29 Si MAS NMR spectra were obtained using single- pulse experiments. 13 C and 29 Si spectra were acquired using CP, with a contact pulse (ramped for 1 H) of 2 and 5 ms, respectively, unless otherwise stated, and 1 H decoupling (CW) applied during acquisition. Spectra chemical shifts were referenced relative to TMS for both 29 Si and 13 C. Results 29 Si MAS NMR spectra for IPC- 2 and IPC- 4 are shown in Figures S6 and S7. NATURE CHEMISTRY 14

15 Figure S6: 29 Si MAS NMR spectra (14.1 T) of (a, b) IPC- 2 and (c, d) IPC- 4. Spectra (a) and (c) are the result of averaging (a) 694 and (c) 882 transients, both with a recycle interval of 120 s. CP spectra (b) and (d) are the result of averaging 8192 transients with a recycle interval of 2 s, and a contact time of 5 ms. The MAS rate was 10 khz. NATURE CHEMISTRY 15

16 Figure S7: 29 Si CP MAS NMR spectra (14.1 T) of (a) IPC- 2 and (b) IPC- 4. Spectra are the result of averaging 8192 transients, with a recycle interval of 2 s, and a contact time of 1 (red), 2 (blue), 3 (green) and 5 (black) ms. The MAS rate was 10 khz. NATURE CHEMISTRY 16

17 S3 Analysis of (Al)IPC- 2 and (Al)IPC- 4 A IIa 0.2 B Absorbance, a. u. IIb Ia 3741 SiOH terminal Ib 3623 Si-(OH)-Al IIa Ia Wavenumber, cm Figure S8 FTIR spectra of Al- IPC- 4 (I) and Al- IPC- 2 (II). Adsorption of acetonitrile, region of hydroxyl vibration (A), region of acetonitrile vibration (B). After (a) and before (b) adsorption; Al- IPC- 4 Si/Al = 70; Al- IPC- 2 - Si/AL = 105. These results indicate that both Lewis and Brønsted acid sites are present. NATURE CHEMISTRY 17

18 Alkylation 250 C, T/P 9.6 Toluene conversion (%) A B Selectivity to cymenes (%) Iso/n-propyltoluenes ratio Al-IPC-2 Al-UTL Al-MFI Al-BEA C D P-cymene in cymenes (%) T-O-S (min) T-O-S (min) Figure S9 Time- on- stream dependence of toluene conversion (A), selectivity to cymenes (B), iso- /n- propyltoluene ratio (C) and p- cymene selectivity (D) in toluene alkylation with isopropyl alcohol at 250 C for Al- IPC- 2 (l ), Al- UTL (l ), Al- MFI (l ) and Al- BEA (l ). These results point out the acid behavior of (Al)IPC- 2 in toluene alkylation with isopropyl alcohol. The activity of (Al)IPC- 2 was similar to MFI, and lower than both zeolite- beta, which has a highly accessible three dimensional 12 x 12 x 12 ring system, and UTL (14 x 12 ring). However, selectivity to all cymenes was higher than MFI and similar to beta and UTL, although selectivity to p- cymenes was similar to MFI. The activity of (Al)IPC- 4 was much lower, consistent with the smaller channels in this structure We see that IPC- 2 ( ring channel system) exhibits similar conversion to other 12- ring zeolites and high selectivity to cymenes (primary alkylation products) but low para- selectivity. IPC- 4 did not show practically any activity, which might be due to the presence of 10- ring system while the 8- ring one is too small to accept aromatic molecules. NATURE CHEMISTRY 18

19 Table S5 Table of CIF files available IPC- 2.cif Atomic positions of experimental IPC- 2 structure IPC- 4.cif Atomic positions of experimental IPC- 4 structure IPC- 2a.cif Calculated atomic positions for IPC- 2 (equivalent to structure a in Figure S3) IPC- 2b.cif Calculated atomic positions for structure b in Figure S3 IPC- 2c.cif Calculated atomic positions for structure c in Figure S3 IPC- 2d.cif Calculated atomic positions for structure c in Figure S3 IPC- 4a.cif Calculated atomic positions for IPC- 4 (equivalent to structure a in Figure S1) IPC- 4b.cif Calculated atomic positions for structure b in Figure S1 IPC- 4c.cif Calculated atomic positions for structure c in Figure S1 IPC- 4d.cif Calculated atomic positions for structure d in Figure S1 References 1. Roth, W. J.; Shvets, O. V.; Shamzhy, M.; Chlubna, P.; Kubu, M.; Nachtigall, P.; Cejka, J., Postsynthesis Transformation of Three-Dimensional Framework into a Lamellar Zeolite with Modifiable Architecture. J. Am. Chem. Soc. 2011, 133 (16), Blochl, P. E., Projector Augmented-Wave Method. Phys. Rev. B 1994, 50 (24), Kresse, G.; Joubert, D., From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 1999, 59 (3), (a) Perdew, J. P.; Burke, K.; Ernzerhof, M., Generalized gradient approximation made simple. Phys. Rev. Lett. 1996, 77 (18), ; (b) Perdew, J. P.; Burke, K.; Ernzerhof, M., Generalized gradient approximation made simple (vol 77, pg 3865, 1996). Phys. Rev. Lett. 1997, 78 (7), Kresse, G.; Hafner, J., Ab-Initio Molecular-Dynamics for Open-Shell Transition-Metals. Phys. Rev. B 1993, 48 (17), K. Lee, E.D. Murray, L.Z. Kong, B.I. Lundqvist and D.C. Langreth, Phys. Rev. B, 82 (2010) NATURE CHEMISTRY 19