Germanosilicate Precursors of ADORable Zeolites Obtained by

Article pubs.acs.org/cm

Germanosilicate Precursors of ADORable Zeolites Obtained by Disassembly of ITH, ITR, and IWR Zeolites Mariya Shamzhy,†,‡ Maksym Opanasenko,†,‡ Yuyang Tian,§ Kateryna Konysheva,‡ Oleksiy Shvets,‡ Russell E. Morris,§ and Jiří Č ejka*,† †

J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of Czech Republic, v.v.i. Dolejškova 3, 182 23 Prague 8, Czech Republic ‡ L.V. Pisarzhevskiy Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 pr. Nauky, Kyiv 03028, Ukraine § EaStChem School of Chemistry, University of St Andrews, Purdie Building, St Andrews, KY16 9ST, U.K. S Supporting Information *

ABSTRACT: Structure transformation of germanosilicate zeolites ITH, ITR, and IWR containing hydrolytically unstable interlayer Ge−O bonds was investigated and is related to the conditions of acidic treatment (i.e., concentration of hydrochloric acid, temperature, duration). The disassembly of ITH (Si/Ge = 2.5), ITR (Si/Ge = 2.4), and IWR (Si/Ge = 6.9) zeolites under appropriate acidic treatment was demonstrated. Low-concentration acid solutions (e.g., 0.01 M HCl) and low temperatures favor the hydrolysis of the zeolites under study. The chemical composition of the parent zeolites strongly influences the efficiency of hydrolysis. For zeolites having sufficient fraction (ca. 50%) of Ge in D4R units (Si/Ge ≤ 6 for ITH and IWR, Si/Ge ≤ 3.7 for ITR), transformation into layered materials (twodimensional zeolites) was successful while the lowering of Ge concentration resulted in only a partial separation of the ITH and ITR crystalline layers. The acidic treatment of medium-pore ITR and ITH zeolites with HCl at ambient temperature for 24 h is optimal for selective cleavage of almost all interlayer Ge−O bonds, while transformation of large-pore IWR zeolite into layered material was observed even after only 5 min of the treatment. These results evidence the general applicability of the ADOR mechanism for the synthesis of new zeolites.

■

INTRODUCTION Zeolites attract significant attention for fundamental and applied studies, with careful and systematic studies of structure−activity relationships contributing important information to support numerous industrial applications as active, selective, and relatively inexpensive catalysts.1−5 The nature of important catalytic, adsorptive, and ion-exchange properties is closely related to the structure and composition of the particular zeolite under study. Although the application of zeolites is so intimately connected with their structural architecture, the major target remains still to control precisely and predictably the porosity of zeolites. The traditional solvothermal preparation of zeolites is complex, and it is difficult or impossible to tailor, a priori, the synthesis to provide zeolites with predictable structures. Recently, we have reported a new mechanism by which zeolites can be prepared, and unlike traditional solvothermal approaches this method does allow the preparation of zeolites with both predicted structure and continuously tunable porosity.6,7 The newly discovered method, which we have named the ADOR process, includes four steps: (i) synthesis of appropriate known zeolite, the Assembly process; (ii) chemically selective cleavage providing layered silicate crystalline © 2014 American Chemical Society

monolayers, the Disassembly process; (iii) Organization of the layers, either spontaneously or by using an appropriate SDA; and finally (iv) calcination of the multilayer material to provide a new 3-D framework, the Reassembly process. The germanosilicate zeolite, IM-12, with the UTL topology (Figure 1A) was the first to be selectively disassembled into the individual crystalline layers (into a material named IPC-1P) with the preservation of the structure of individual layers. The

Figure 1. Structure of zeolite UTL (001 projection, A), ITH (010 projection, B), ITR (100 projection, C), and IWR (100 projection, D). Received: August 11, 2014 Revised: September 17, 2014 Published: September 18, 2014 5789

dx.doi.org/10.1021/cm502953s | Chem. Mater. 2014, 26, 5789−5798

Chemistry of Materials

Article

(TEOS, 98%), hydrochloric acid (37%), hydrofluoric acid (48 wt %), and acetone (≥99.9%) were used for the synthesis and postsynthesis treatment of zeolites. Sodium hydroxide (≥98%), d-mannitol (≥98%), oxalic acid dihydrate (≥99%), ethylenediaminetetraacetic acid (≥99%), zinc sulfateheptahydrate (≥99%), and ammonium hydroxide solution (≥25% in water) were used for analysis of chemical composition of the samples. All reactants were obtained from Sigma-Aldrich and used as received without any further treatment. All manipulations with highly toxic hydrofluoric acid being also a contact poison were performed under the hood using the personal protective equipment (i.e., face shields, gloves, goggles). Synthesis of Templates and Zeolites. Preparation of hexamethonium dibromide (SDA1) and propane-1,3-bis(trimethylphosphonium) dibromide (SDA2) was carried according to refs 32 and 33. Prepared SDA1 and SDA2 were transformed into the hydroxide form using Biorad AG-1X8 anion exchange resin. The solutions of templates were concentrated (evaporated under vacuum at 36 °C) until the hydroxide concentration became 1.0 M. The synthesis of B-containing germanosilicate IWR zeolite was performed according to ref 28 using hexamethonium dihydroxide as SDA. The composition of the reaction mixture was in the range 0.10− 0.15 BO1.5:0.57−0.75 SiO2:0.15−0.30 GeO2:0.25 R(OH)2:5 H2O. The resulting gel was charged into 25 mL Teflon-lined steel autoclaves and heated at 175 °C for 10−18 days under agitation (40 rpm). Propane-1,3-bis(trimethylphosphonium) hydroxide was used in the synthesis of germanosilicate ITR zeolite according to ref 32. The composition of initial gel was varied in the range 0.66−0.91 SiO2:0.09−0.33 GeO2:0.15 R(OH)2:7 H2O. The crystallization was carried out at 175 °C for 7−10 days under agitation (40 rpm). Germanosilicate ITH zeolite was synthesized from reaction mixture 0.8−0.91 SiO2:0.09−0.20 GeO2:0.25 R(OH)2:0.0−0.50 HF:5H2O according to ref 31 using hexamethonium dihydroxide as SDA. The mixture was crystallized at 175 °C for 8−25 days under agitation (40 rpm). Germanosilicate ITH zeolite was also prepared according to ref 34. N,N,N′,N′-Tetramethyl-1,6-hexanediamine (TMHDA) was used as the structure directing agent (SDA3). The synthetic suspension had the composition of (1 − x) SiO2:x GeO2:7 TMHDA:1.4 HF:44 H2O, where x = 0.5 for ITH-1 and x = 0.33 for ITH-2. The suspension was heated at 175 °C for 3 days under static conditions. The as-synthesized samples were washed with distilled water, dried at 65 °C for 12 h, and calcined at 550 °C for 6 h with a temperature ramp of 1 °C·min−1. Obtained zeolites were designed as xB-IWR-y, ITR-y, and ITH-y, where x is mol % of B and y is Si/Ge in the reaction mixture. Hydrolysis. Calcined zeolites were hydrolyzed in the solution of hydrochloric acid (0.01−12 M) at temperatures 25 or 80 °C for 2−72 h with the w/w ratio 1/100. The hydrolyzed material was isolated by centrifugation, washed with deionized water and acetone, and dried at 25 °C. Characterization. Crystallinity of the samples under study was determined by X-ray powder diffraction on a Bruker AXS D8 Advance diffractometer with a Vantec-1 detector in the Bragg−Brentano geometry using Cu Kα radiation (1.54056 Å). A gentle grinding of the samples was performed before measurements. Adsorption isotherms of nitrogen at −196 °C were collected using an ASAP 2020 (Micromeritics) static volumetric apparatus. In order to attain sufficient accuracy in the accumulation of the adsorption data, the ASAP 2020 was equipped with pressure transducers covering the 133 Pa, 1.33 kPa, and 133 kPa ranges. Before adsorption experiments the samples were outgassed under turbomolecular pump vacuum at a temperature of 300 °C for 8 h. The size and shape of zeolite crystals were examined by scanning electron microscopy (SEM, JEOL JSM-5500LV microscope). The B, Si, and Ge content was determined by elemental analysis. For this purpose 0.2−0.3 g of zeolite sample was heated at 70 °C with 5−7 mL of 10 M NaOH in a platinum cup. After total dissolution of the zeolite sample, 10−15 mL of concentrated HCl was added until the pH became 0.6−0.7 and acid solution was evaporated at 50 °C during 1 h. Under these conditions Ge evaporated from the solution in

critical condition is the presence of regions of different compositions in the original UTL zeolite. The germanium is preferentially located between the layers, and the Ge−OSi and Ge−OGe interlayer bonds are more sensitive to degradation in a neutral or acidic medium than intralayer Si−OSi ones.8−11 The differential in sensitivity allows the interlayer Gecontaining species to be removed, leaving the layers intact in the materials IPC-1P. The preparation of IPC-1P afforded the possibility for various treatments toward modifying layer orientation and spacing similar to those developed with layered zeolite precursors, like MCM-22P.12 It included swelling with CTMACl/TPAOH mixtures according to the conventional procedure.13−18 Subsequent pillaring, using TEOS, was shown to result in the formation of layered mesostructured (pillared) material characterized by improved mesopore volume.19 In addition, IPC-1P can be transformed into several different materials, IPC2,20 IPC-4,6 IPC-6,21 and IPC-7, depending on the conditions used. All the new zeolites comprise exactly the same intralayer topology as the parent UTL zeolite, but they differ in the connectivity of the layers, resulting in 2D porous structures of different ring sizes ranging from small pore (8 rings) all the way up to extra-large pore (14 ring). A material very closely related to IPC-2 (COK-14) can also be made via an inverse sigma transformation process.22 Organoalkoxysilanes being widely used for surface modification of inorganic materials and preparation of hybrid materials23 were utilized for pillaring of IPC-1P precursor and resulted in novel organic−inorganic solids with tunable and excellent textural properties.24 Recently, the ADOR principle was extended to show how similar synthetic methodologies can be applied to other materials with similar structural properties to UTL, including zeolites with the IWW topology.25,26 In this paper, we demonstrate the applicability of the ADOR process to a family of germanosilicate zeolites, ITQ-13, ITQ-34, and ITQ-24, with the ITH, ITR, and IWR topologies, respectively, possessing the appropriate structural characteristics (i.e., frameworks containing layers connected by hydrolytically unstable interlayer Ge−O bonds). Germanosilicate zeolites have attracted a lot of attention during the past decade as germanium was found to act as an inorganic structure-directing agent allowing one to synthesize new zeolites, with particular selectivity toward new materials containing germanate double-four-ring (D4R) units.27−30 Recently, new germanosilicate zeolites with the ITH, ITR, and IWR topologies were synthesized in highly concentrated reaction media (H2O/TIV < 10, where T is the zeolite framework tetrahedral atom). Germanosilicate zeolite ITH was formed in a fluoride-containing medium in the presence of hexamethonium as template.31 Zeolite IWR was prepared in boron- and aluminum-containing germanosilicate mixtures,28 and germanosilicate zeolite ITR was prepared in the presence of propane-1,3-bis(trimethylphosphonium) hydroxide.32 The topologies of these materials are all similar to that of UTL in the sense that they can all be viewed as dense two-dimensional (2D) layers separated by D4R bridging units enriched in Ge (Figure 1).

■

EXPERIMENTAL SECTION

Materials. 1,6-Dibromohexane (96%), trimethylamine solution (31−35 wt % in ethanol), 1,3-dibromopropane (99%), trimethylphosphine (97%), N,N,N′,N′-tetramethyl-1,6-hexanediamine (99%), boric acid (99.97%), germanium oxide (99.99%), tetraethylorthosilicate 5790



Article

Table 1. Phase Diagram of Zeolite Formation (T = 175 °C, 7−25 days)

a

SDA/TIV = 0.15.

b)

SDA/TIV = 0.25.

Table 2. Chemical Composition and Textural Properties of Zeolites under Investigation chemical composition, mol % sample

B

Si

Ge

Si/Ge

crystal size (μm)

shape

Vmicro, cm3·g−1

Vtotal, cm3·g−1

SBET, m2·g−1

ITH-1 ITH-2 ITH-4 ITH-10 ITR-2 ITR-3 0.1B-IWR-2 0.1B-IWR-6

− − − − − − 14.8 16.6

71.4 81.4 88.2 90.3 70.2 82.2 74.4 79.7

28.6 18.5 11.8 9.7 29.8 17.8 10.8 3.6

2.5 4.4 7.5 9.3 2.4 4.6 6.9 21.9

n.d. n.d. 1 × 0.1 × 0.5 3 × 0.1 × 0.5 4 6 3 3

platelet-like platelet-like platelet-like platelet-like agglomerated needles agglomerated needles spherical agglomerates spherical agglomerates

0.120 0.137 0.155 0.104 0.030 0.045 0.109 0.125

0.125 0.140 0.250 0.211 0.410 0.390 0.169 0.160

285 313 300 273 200 175 277 300

presence of fluoride anions in the gel (Table 1). IWR zeolite was not obtained as germanosilicate, but only in the presence of 10−15 mol % of boron in the reaction medium. The use of SDA3 resulted in the formation of pure ITH zeolite even in Gerich (Si/Ge = 1 or 2) gels. Zeolite ITR was synthesized from fluoride-free mixtures having Si/Ge molar ratio in the range 2− 10 using SDA2 (Table 1). Samples ITH-1, ITH-2, ITH-4, ITH-10, ITR-2, ITR-3, 0.1BIWR-2, and 0.1B-IWR-6 differing in chemical composition (Table 2) were chosen for investigation of their hydrolytic stabilities. XRD patterns of all as-synthesized zeolites exhibit a high degree of crystallinity without the presence of any other phases (Figure 2). While all investigated ITH and IWR zeolites

the form of GeCl4,35 but volatilization of boron is negligible ( 7. The observation of pure silica D4R in ITH-4 and ITH-10 is consistent with our estimation. The Si/Ge ratio of ITH-2 is about 4.4, which is higher than the estimated ratio of Ge and occupies half of the D4R. In the 19 F MAS NMR spectrum of ITH-2 (Figure 5c), the resonances corresponding to the pure silica units are not present. It shows three resonances at −55 ppm, −20 ppm, and −8 ppm, corresponding to Ge-containing [415262] cages, [7Si, 1Ge] D4R, and [4Si, 4Ge] D4R, respectively. The present resonance due to the [7Si, 1Ge] D4R indicates that although the higher Ge concentration in the ITH framework is achieved, the Ge not only forms 50% Ge distributed D4R but also some high silica D4Rs. The extra Ge goes into the layer and forms the Gecontaining [415262] cages.

ITH-2 zeolite treated with 0.1−12 M HCl in the temperature range from room temperature up to 100 °C for 24 h showed minor structural changes, reflected by the right-shift of 100 diffraction line (corresponding to diminishing of interlayer distance, Figure 6B) and decreasing in intensities of the 102 and 111 reflections. In addition, an increasing degree of amorphization of the ITH structure with increase of the HCl concentration used for hydrolysis (Figure 6B) should be noted. Although the Si/Ge ratio of ITH-2 is in the range of that estimated so that Ge are located in the D4R (Si/Ge < 6), the NMR result indicates the existence of [7Si, 1Ge] D4R. Those high Si D4R units exhibit good hydrolytic stability and prevent the full separation of the ITH layers. ITH-4 zeolite (Si/Ge = 7.5, Table 2) exhibits similar hydrolytic stability as ITH-2. The treatment of ITH-10 zeolite with the highest Si/Ge ratio among the investigated ITH zeolites (Si/Ge = 9.7, Table 2) in 0.01−12 M HCl at 25 °C for 4−24 h did not influence the position of the diffraction lines, which is convincing evidence of even higher structural stability of this zeolite in acid medium. As it was previously shown,45 the as-synthesized layered solids usually compress upon calcination to a materials with a shorter lattice parameter. These layered materials may be either ordered or randomly stacked. The calcination of ITH-1 treated with 0.01 M HCl at 25 °C for 36 h resulted in the disappearance of the interlayer 100 diffraction line (Figure 6A). In contrast, calcination did not cause any structural changes of ITH-10 treated with 0.01 M HCl at 25 °C for 36 h (Figure 7), which indicates that disassembly of the original ITH-10 did not take place under such treatment conditions. These results evidence the role of Ge in hydrolysis and indicate the concentration required for successful transformation to two-dimensional zeolite. 5794



Article

Supporting Information Table SI-1), confirming a major removal of Ge. 2.2.2. ITR Zeolites. For comparison with ITH zeolite and to get a more general picture of the stability of germanosilicates with different structures, zeolites ITR and IWR were treated under the same conditions. The treatment of ITR-3 zeolite characterized by Si/Ge ratio 4.6 (it corresponds to less than 50% population of Ge toms in D4R units) with 0.01 M HCl at 25 °C resulted only in the right-shift of the interlayer 002 diffraction line and decreasing intensities of interlayer 022 and 112 peaks while maintaining all the intralayer reflections (Figure 8A). Similarly to the previously discussed ITH-4

Figure 7. XRD patterns of ITH-1 zeolite hydrolyzed in 12 M HCl at 25 °C for different times (A) and ITH-2 zeolite treated with HCl for 24 h (B). The intralayer reflections, 0kl, are marked by asterisks. Figure 8. XRD patterns of ITR-3 zeolites hydrolyzed for different times (with 0.01 M HCl at 25 °C, A) and concentration of HCl/ temperature (after 12 h, B). The intralayer reflections, hk0, are marked by asterisks.

It was recently reported that the treatment of germanosilicate UTL zeolite in high-concentrated 12 M HCl resulted in an inverse sigma transformation process22 leading to formation of COK-14 material, structurally related to the original UTL zeolite, but possessing layers connected with S4Rs units instead of D4Rs. This effect has been explained as the product of a [H+] dependent two-stage process. Structural transformations of ITH-1 zeolite were also followed in 12 M HCl at room temperature. Figure 7 shows the XRD patterns of ITH-1 containing only [4Si 4Ge] D4R units and a minor concentration of Ge in the layer and the products of its hydrolysis in 12 M HCl for different times at room temperature. While ITH-1 zeolite retains its structure even after 1 h of treatment in 12 M HCl, after 3 h of the treatment with 12 M HCl, a broad peak at 2θ of 8.81° appears. This peak is assumed to be the interlayer diffraction after the removal of the D4R pillaring. Meanwhile, the interlayer reflections (e.g., 100, 102, and 111) are retained, indicating the separation of the layers is incomplete or that the hydrolysis occurred only on a fraction of the crystals. However, prolonging the acidic treatment up to 36 h resulted in disappearance of the 100 diffraction line, centered at 6.91° 2θ as well as 102 and 111 reflections, indicating that complete hydrolysis of interlayer bonds was achieved for ITH-1 zeolite under the conditions (Figure 7A). Noticeably, the left-shift of interlayer diffraction line took place with the prolongation of the treatment with 12 M HCl (3−42 h) indicating the increasing interlayer distance with time. This result can be rationalized by the same mechanism as for UTL, where a rearrangement process has been identified that rebuilds connections between the layers.21 Thus, materials treated for 24, 36, and 42 h (Figure 7) are assumed to contain increasing amount of interlayer Si−O−Si bonds and present partially connected ITH layers. The Si/Ge ratio in the hydrolyzed (12 M HCl, 36 h) ITH-1 sample was significantly higher (Si/Ge = 115, Supporting Information Table SI-1) than in parent ITH-1 zeolite (Si/Ge = 2.5,

zeolite, the structural changes reflected in XRD patterns increased with the prolonged acidic treatment and were suppressed with the increasing temperature or concentration of the acid solution used (Figure 8B, Table 4). It should be noted, that for ITR-2 (Si/Ge = 2.4, Table 2), which in contrast to ITR-3 (Si/Ge = 4.6, Table 2) is expected to have about 50% of Ge in D4R units, we observed more dramatic decrease in the interlayer distance by 1.70 Å and in decreasing intensities of the 111, 112, and 131 peaks with maintenance of all intralayer reflections (Figure 9A) under optimal hydrolysis conditions (Table 4). This result is

Figure 9. XRD patterns of ITR-2 (a) and ITR-3 (b) zeolites treated with 0.01 M HCl at 25 °C for 24 h (blue lines) and subsequently calcined (red lines). 5795



Article

needed to achieve full hydrolysis of interlayer Ge−OSi bonds in ITH and ITR zeolites possessing medium pores. One can infer that the optimal duration of acid treatments determined by diffusion of ions into and out of the micropore system of germanosilicate zeolites, the larger pores, the faster diffusion, and the shorter time, is required for successful hydrolysis. Further prolonged acid treatment of 0.1B-IWR-2 zeolite results in the right-shift of intralayer diffraction lines and decreasing their intensities, indicating structural changes of IWR layers. This may be connected with the hydrolysis of intralayer Ge−O (the possible occupation of T2 and T3 “intralayer” sites by Ge atom shown in ref 42) or B−O bonds. Similarly, the decreasing Ge content in 0.1B-IWR-6 (Si/Ge = 21.9, Table 1) results in the stabilization of IWR framework the negligible shift of interlayer 001 diffraction line was observed even after 8 h of the treatment of the sample with 0.01 M HCl (Figure 10B, Table 5). Chemical analyses evidenced that postsynthesis modifications removed most of B and Ge from the samples (Supporting Information Table SI1). No B was detected in 0.1B-IWR-2 and 0.1B-IWR-6 zeolites treated with 0.01 M HCl at 25 °C (Supporting Information Table SI-1). At the same time, Si/Ge ratio in the treated samples was higher (31−39, Supporting Information Table SI1) than in parent B-IWR zeolites (6.9 and 21.9 for initial 0.1BIWR-2 and 0.1B-IWR-6, respectively, Supporting Information Table SI-1). Increase of a broad halo around 20−25° 2θ on XRD of treated samples with increasing time of hydrolysis indicates the magnification of amorphization processes with prolonged treatment (Figure 10). The calcination of 0.1B-IWR-2 treated with 0.01 M HCl for 5 min resulted in the right-shift of diffraction lines, indicating the contraction of hydrolyzed material upon thermal treatment (Supporting Information Figure SI-2). 2.3. Hydrolysis of Germanosilicate Zeolites: ITH, ITR, and IWR vs UTL. Thus, the population of D4R units with Ge atoms was shown to control the completeness of the transformation of the original 3D germanosilicate zeolites into layered materials (Figure 11). ITH-1 zeolite containing mostly [4Si, 4Ge] D4R units was fully transformed into layered material having the same structure of crystalline layers.

obviously connected with a higher amount of Ge−OT bonds in between ITR-2 layers (i.e., a high population of D4R units with Ge). Chemical analyses (Supporting Information Table SI-1) confirmed that postsynthesis modifications led to a drastic decrease of Ge concentration in ITR-2 (29.8 vs 2.5 mol % of Ge in initial and hydrolyzed samples, respectively, Supporting Information Table SI-1) and ITR-3 samples (17.8 vs 3.3 mol % of Ge in initial and hydrolyzed samples, respectively, Supporting Information Table SI-1) indicating extraction of a substantial part of Ge during the treatment. It can be inferred that particularly D4R units and their connectivities to the original layers were broken. The calcination of ITR-2 treated with 0.01 M HCl resulted in the right-shift of the 002 diffraction line, which may indicate shortening of interlayer distance upon calcination (Figure 9). In contrast, calcination did not affect the position of the (002) diffraction line for ITR-3 treated with 0.01 M HCl, which showed the negligible structural changes after hydrolysis (Figure 9). In contrast to ITH zeolite, hydrolysis of ITR-2 and ITR-3 did not result in the appearance of a significant amount of amorphous phase after the treatments (Figure 9), indicating reasonable stability of intralayer bonds under these conditions. 2.2.3. IWR Zeolites. A substantial shift of the interlayer 001 diffraction line (Table 5) with preservation of intralayer 110 Table 5. Decrease in the Interlayer d-Spacing (ΔD) for 0.1 B-IWR-2 and 0.1B-IWR-6 Zeolites, Hydrolyzed in 0.01 M HCl at 25 °C for Different Times 0.1 B-IWR-2

0.1 B-IWR-6

time of the treatment

2θ, 001

ΔD, Å

2θ, 001

ΔD, Å

0 5 min 20 min 2h 4h 8h

7.04 8.31 8.32 8.37 8.44 −

0 1.92 1.93 n.d. n.d. −

7.02 − − 7.12 7.26 7.35

0 − − 0.17 0.41 0.56

and 200 reflections confirms successful hydrolysis of interlayer Ge−O bonds in large-pore 0.1B-IWR-2 (Si/Ge = 6.9) zeolite even after 5 min of the treatment with 0.01 M HCl at 25 °C (Figure 10A). The transformation of extra-large pore UTL zeolite (Si/Ge = 4.5) to a 2D IPC-1P material was also achieved within 5 min of the treatment with 0.1 M HCl in ref 19. At the same time we found that significantly longer time (i.e., 24 h) is

Figure 11. Structure of ITH (A), ITR (B), and IWR (C) layers.

The decreasing d-spacing after hydrolysis of UTL zeolite to IPC-1P precursor (about 2.75 Å20) can be compared with that for the germanosilicates under investigation (2.62, 1.70, and 1.93 Å for ITH, ITR, and IWR zeolites, respectively). Taking also into account the preservation of the position of intralayer diffraction lines after hydrolysis and the disappearance of all interlayer diffraction lines after calcination, the full transformation of ITH-1 and ITR-2 zeolites into two-dimensional zeolites may be assumed (Figure 12). Boron atoms being presented in the layers of IWR zeolite seem to be the additional centers of instability, preventing the preservation of the structure of original IWR crystalline layers in acidic medium.

Figure 10. XRD patterns of 0.1B-IWR-2 (A) and 0.1B-IWR-6 (B) zeolites treated with 0.01 M HCl at 25 °C for different times. 5796



■

Article

ASSOCIATED CONTENT

S Supporting Information *

A table giving chemical compositions of as-synthesized and hydrolyzed ITH, ITR, and B-IWR zeolites and figure showing the XRD patterns of 0.1B-IWR-2 treated with 0.01 M HCl at 25 °C for 5 min and subsequently calcined. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

Figure 12. Schematic representation for the proofs of the ITH, ITR, and IWR zeolites hydrolysis success.

■

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors thank Dr. Daniel Dawson (University of St Andrews) for the providing of NMR data. J.C. acknowledges the Czech Science Foundation for the project of the Centre of Excellence (P106/12/G015), M.S. acknowledges the Czech Science Foundation for the support of Project 14-30898P. R.E.M. thanks the Royal Society for provision of an industry fellowship and the E.P.S.R.C. for funding (EP/K025112/1 and EP/L014475/1).

CONCLUSIONS

The disassembly of germanosilicate ITH (Si/Ge = 2.5) and ITR (Si/Ge = 2.4) zeolites by chemically selective cleavage of interlayer Ge−OT bonds under appropriate acidic treatment was demonstrated. The obtained layered solids are prospective precursors for the synthesis of new mesostructured materials containing crystalline layers by postsynthetic treatment (e.g., swelling, pillaring) and new zeolites based on the ADOR transformation. The analysis of the influence of the treatment conditions on hydrolysis output allows defining the critical factors controlling the disassembly degree of germanosilicate zeolites ITH, ITR, and IWR: (1) Size of pore system. The disassembly of germanosilicate zeolites containing hydrolytically unstable interlayer bonds is a continuous process developing over time. The length of the optimal hydrolysis is likely determined by diffusion of ions into and out of the pore system of germanosilicate zeolites. The rate of acidic hydrolysis of zeolites containing D4Rs increases with increasing pore size of germanosilicate zeolites being higher for large-pore IWR zeolite in comparison with medium pore ITH and ITR zeolites. (2) Chemical composition. The Si/Ge ratio in the parent zeolite impacting the number of labile Ge−OT interlayer bonds strongly influences its hydrolytic stability, which decreases with the increasing Ge content. For zeolites having ≥50% Ge in D4R units (Si/Ge < 6 for ITH and IWR, Si/Ge < 3.7 for ITR), full transformation into layered material was found, while the lowering Ge concentration resulted in only a partial separation of crystalline layers of ITH, ITR, and IWR zeolites during hydrolysis. Boron atoms being present in the layers of IWR zeolite decrease their stability, limiting the applicability of borogermanosilicate zeolites as precursors for two-dimensional zeolites. (3) Acid concentration and temperature. As for the mechanism of UTL hydrolysis,21 the process for ITH, ITR, and IWR is a complex multistep process including not only hydrolysis but also the possibility of rearrangement to rebuild interlayer connections. The low-concentration acid solutions (0−0.01 M) and low treatment temperature (25 °C) do not promote any rearrangement processes that lead to reconnection of the layers and are therefore more efficient for hydrolysis of germanosilicate zeolites under study.

■

REFERENCES

(1) Zones, S. I. Microporous Mesoporous Mater. 2011, 144, 1. (2) Corma, A.; Navarro, M. T. In Studies in Surface Science and Catalysis; Aiello, R., Giordano, G., Testa, F., Eds.; Elsevier: 2002; Vol. 142, p 487. (3) Kubicka, D.; Kubickova, I.; Cejka, J. Catal. Rev.: Sci. Eng. 2013, 55, 1. (4) Č ejka, J.; Mintova, S. Catal. Rev.: Sci. Eng. 2007, 49, 457. (5) Cejka, J.; Centi, G.; Perez-Pariente, J.; Roth, W. J. Catal. Today 2012, 179, 2. (6) Roth, W. J.; Nachtigall, P.; Morris, R. E.; Wheatley, P. S.; Seymour, V. R.; Ashbrook, S. E.; Chlubna, P.; Grajciar, L.; Polozij, M.; Zukal, A.; Shvets, O.; Č ejka, J. Nat. Chem. 2013, 5, 628. (7) Roth, W. J.; Nachtigall, P.; Morris, R. E.; Č ejka, J. Chem. Rev. 2014, 114, 4807. (8) Gao, F.; Jaber, M.; Bozhilov, K.; Vicente, A.; Fernandez, C.; Valtchev, V. J. Am. Chem. Soc. 2009, 131, 16580. (9) Sastre, G.; Pulido, A.; Corma, A. Microporous Mesoporous Mater. 2005, 82, 159. (10) Li, Q.; Navrotsky, A.; Rey, F.; Corma, A. Microporous Mesoporous Mater. 2003, 59, 177. (11) Jiang, J.; Yu, J.; Corma, A. Angew. Chem., Int. Ed. 2010, 49, 3120. (12) Diaz, U.; Corma, A. Dalton Trans. 2014, 43, 10292. (13) Roth, W. J.; Kresge, C. T.; Vartuli, J. C.; Leonowicz, M. E.; Fung, A. S.; McCullen, S. B. In Studies in Surface Science and Catalysis; Beyer, H. K., Karge, H. G., Kiricsi, I., Nagy, J. B., Eds. 1995; Vol. 94, p 301. (14) Roth, W. J.; Vartuli, J. C.; Kresge, C. T. In Studies in Surface Science and Catalysis; Abdelhamid, S., Mietek, J., Eds.; Elsevier: Amsterdam, 2000; Vol. 129, p 501. (15) Roth, W. J. In Studies in Surface Science and Catalysis; Č ejka, J., van Bekkum, H., Corma, A., Schüth, F., Eds.; Elsevier: 2007; Vol. 168, p 221. (16) Chlubna, P.; Roth, W. J.; Zukal, A.; Kubu, M.; Pavlatova, J. Catal. Today 2012, 179, 35. (17) Roth, W. J.; Chlubna, P.; Kubu, M.; Vitvarova, D. Catal. Today 2013, 204, 8. (18) Shamzhy, M.; Mazur, M.; Opanasenko, M.; Roth, W. J.; Cejka, J. Dalton Trans. 2014, 43, 10548. (19) Chlubna, P.; Roth, W. J.; Greer, H. F.; Zhou, W.; Shvets, O.; Zukal, A.; Č ejka, J.; Morris, R. E. Chem. Mater. 2013, 25, 542. 5797



Article

(20) Roth, W. J.; Shvets, O. V.; Shamzhy, M.; Chlubna, P.; Kubu, M.; Nachtigall, P.; Č ejka, J. J. Am. Chem. Soc. 2011, 133, 6130. (21) Wheatley, P. S.; Chlubná-Eliásǒ vá, P.; Greer, H.; Zhou, W.; Seymour, V. R.; Dawson, D. M.; Ashbrook, S. E.; Pinar, A. B.; McCusker, L. B.; Opanasenko, M.; Č ejka, J.; Morris, R. E. Angew. Chem., Int. Ed. 2014, DOI: 10.1002/anie.201407676. (22) Verheyen, E.; Joos, L.; Van Havenbergh, K.; Breynaert, E.; Kasian, N.; Gobechiya, E.; Houthoofd, K.; Martineau, C.; Hinterstein, M.; Taulelle, F.; Van Speybroeck, V.; Waroquier, M.; Bals, S.; Van Tendeloo, G.; Kirschhock, C. E. A.; Martens, J. A. Nat. Mater. 2012, 11, 1059. (23) Kuroda, K.; Shimojima, A.; Kawahara, K.; Wakabayashi, R.; Tamura, Y.; Asakura, Y.; Kitahara, M. Chem. Mater. 2014, 26, 211. (24) Opanasenko, M.; Parker, W. O. N.; Shamzhy, M.; Montanari, E.; Bellettato, M.; Mazur, M.; Millini, R.; Č ejka, J. J. Am. Chem. Soc. 2014, 136, 2511. (25) Chlubná-Eliásǒ vá, P.; Tian, Y.; Pinar, A. B.; Kubů, M.; Č ejka, J.; Morris, R. E. Angew. Chem., Int. Ed. 2014, 53, 7048. (26) Burel, L.; Kasian, N.; Tuel, A. Angew. Chem., Int. Ed. 2014, 53, 1360. (27) Corma, A.; Puche, M.; Rey, F.; Sankar, G.; Teat, S. J. Angew. Chem., Int. Ed. 2003, 42, 1156. (28) Castaneda, R.; Corma, A.; Fornes, V.; Rey, F.; Rius, J. J. Am. Chem. Soc. 2003, 125, 7820. (29) Dodin, M.; Paillaud, J.-L.; Lorgouilloux, Y.; Caullett, P.; Elkaim, E.; Bats, N. J. Am. Chem. Soc. 2010, 132, 10221. (30) Jiang, J.; Jorda, J. L.; Diaz-Cabanas, M. J.; Yu, J.; Corma, A. Angew. Chem., Int. Ed. 2010, 49, 4986. (31) Vidal-Moya, J. A.; Blasco, T.; Rey, F.; Corma, A.; Puche, M. Chem. Mater. 2003, 15, 3961. (32) Corma, A.; Diaz-Cabanas, M. J.; Jorda, J. L.; Rey, F.; Sastre, G.; Strohmaier, K. G. J. Am. Chem. Soc. 2008, 130, 16482. (33) Sastre, G.; Pulido, A.; Castañeda, R.; Corma, A. J. Phys. Chem. B 2004, 108, 8830. (34) Ren, X.; Liu, J.; Li, Y.; Yu, J.; Xu, R. J. Porous Mater. 2013, 20, 975. (35) Rayner, H. B. Anal. Chem. 1963, 35, 1097. (36) Corma, A.; Diaz-Cabanas, M. J.; Jiang, J.; Afeworki, M.; Dorset, D. L.; Soled, S. L.; Strohmaier, K. G. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 13997. (37) Jiang, J.; Jorda, J. L.; Yu, J.; Baumes, L. A.; Mugnaioli, E.; DiazCabanas, M. J.; Kolb, U.; Corma, A. Science 2011, 333, 1131. (38) O’Keeffe, M.; Yaghi, O. M. Chem.Eur. J. 1999, 5, 2796. (39) Blasco, T.; Corma, A.; Diaz-Cabanas, M. J.; Rey, F.; Vidal-Moya, J. A.; Zicovich-Wilson, C. M. J. Phys. Chem. B 2002, 106, 2634. (40) Schaack, B. B.; Schrader, W.; Schueth, T. Angew. Chem., Int. Ed. 2008, 47, 9092. (41) Castaneda, R.; Corma, A.; Fornes, V.; Martinez-Triguero, J.; Valencia, S. J. Catal. 2006, 238, 79. (42) Jorda, J. L.; Cantin, A.; Corma, A.; Diaz-Cabanas, M. J.; Leiva, S.; Moliner, M.; Rey, F.; Sabater, M. J.; Valencia, S. Z. Kristallogr. 2007, 393. (43) Kosmulski, M. J. Colloid Interface Sci. 1998, 208, 543. (44) Liu, X.; Ravon, U.; Bosselet, F.; Bergeret, G.; Tuel, A. Chem. Mater. 2012, 24, 3016. (45) Roth, W. J.; Dorset, D. L. Microporous Mesoporous Mater. 2011, 142, 32.

5798


Germanosilicate Precursors of ADORable Zeolites Obtained by

Recommend Documents