Ruthenium-Catalyzed Propargylation of Aromatic Compounds with

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PAPER Joseph T. Hupp, Omar K. Farha et al. Efficient extraction of sulfate from water using a Zr-metal–organic framework

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DOI: 10.1039/C7DT03751A

Insight into the ADOR zeolite-to-zeolite transformation: UOV case Valeryia Kasneryk,a Mariya Shamzhy,b Maksym Opanasenko,b Paul S. Wheatley,c Russell E. aJ. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i.,

Dolejškova 3, 182 23 Prague 8, Czech Republic bDepartment

of Physical and Macromolecular Chemistry, Faculty of Science, Charles

University, Hlavova 8, 128 43 Prague 2, Czech Republic cSchool

of Chemistry, University of St Andrews, Purdie Building, St Andrews KY16 9ST UK

KEYWORDS: ADOR, zeolites, germanosilicates, structure rearrangement

Abstract IPC-12 zeolite is the first member of ADOR family produced by the structural transformation of UOV. The details of UOV rearrangement were studied to determine the influence of properties of parent zeolite and treatment conditions on the outcome of IPC-12 formation. It was established that incomplete disassembly of UOV can be caused by insufficient lability of interlayer connectivity in parent material possessing Si-enriched D4Rs or by inhibition of hydrolysis by diluted acid at high temperature. The impacts of specific interactions of the framework with anions on controllable breaking of interlayer connectivity as well as the conditions of the treatment at low pH (< –1) on the characteristics of produced IPC-12 were found to be negligible. Concentration of acid significantly influences the extent and even the direction of UOV transformation. Layers disassembly is inhibited in 1 – 4 M acid solutions, complete hydrolysis to layered precursor can be achieved in 0.1 M, while application of 12 M solution lead to direct formation of IPC-12. Layers reassembly followed using in situ XRD measurement with synchrotron source was found to be gradual process starting already at 40 °C and completing at 200 – 220 °C.

Introduction The history of zeolite synthesis was never linear but consisted of sporadic step-changes in methodologies. During the whole “zeolite century” starting in the 1930s with the systematic investigations of Richard M. Barrer, a lot of innovative approaches resulted in dramatic changes in our understanding of this area. The works of Barrer reported in 1940s1-2 showed the possibility for artificial fabrication of

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Morris,b,c Jiří Čejka*a

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zeolites that was a challenge for almost 200 years since their discovery. The next turning point was the introduction of organic cations as structure-directing agents in 1960s,3-5 which provided a possibility for the synthesis of a number of previously unknown zeolite topologies. The discovery of aluminophosphates dramatic boosts for development of the chemistry of molecular sieves. Despite all the mentioned innovations, which completely changed our perception of zeolites and related materials, none of them can be defined as an approach for really intelligent design of new structures. The reason for that lies in the essence of conventional way to produce zeolites – the arrangement of the desired material is predetermined by the solvothermal synthesis conditions. While millions of zeolite structures are potentially achievable via direct synthesis,11-13 it is almost impossible to predict which one will be next discovered and which factors are responsible for the structure formation. In contrast, the recently proposed ADOR (assembly – disassembly – organization – reassembly) strategy14-16 is an alternative approach to prepare new zeolite structures in rational way since it is based on the idea of predetermined transformation of the extended building units. This method consists of the controllable reorganization of parent zeolite possessing anisotropic lability, e.g. consisting of stable layers and unstable interlayer connections. At the moment, the examples of application of lability in only one direction were reported,14 although the general idea of the ADOR approach does not presume any limitations related to the location of centers of instability. As all methods do, the ADOR has some limitations. Firstly, the outcome of the ADOR is extremely dependent on the characteristics (structure, chemical composition, elements distribution etc.) of the initial material, i.e. only a combination of proper direct synthesis and post-synthesis transformation may lead to the desired structure. Thus, although different germanosilicates were predicted to be applicable for the ADOR methodology (because of their structure properties),17-18 up to now the optimal conditions of disassembly were determined only for IWW19, ITH, ITR20 germanosilicates, while further organization and reassembly steps have been reported only for a few of them, namely UTL21-22, UOV23 and recently SAZ-1.24 Furthermore, ADOR is a costly and complicated multi-step procedure restricting its large-scale application. Despite the mentioned limitations, the ADOR strategy applied for zeolite UTL was shown to be extremely efficient allowing to obtain until now 6 new zeolites21-22,

25

and a wide range of related materials26-30 including “stage-

structured” zeolite-like materials with continuously tunable textural properties31 that have never been achieved before. Particular advantage of this technique is to synthesize “unfeasible” zeolites based on works of Deem and coworkers.13, 22, 32-33



and other non-aluminosilicate solids6-8 as well as ordered mesoporous materials9-10 was among the latest

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Recently, we reported the synthesis of new IPC-12 zeolite (Fig. 1) using the ADOR transformation.23 IPC-12 was the first member of ADOR family produced by the structural transformation of the parent zeolite UOV. UOV germanosilicate (Fig. 1) has a 3-dimentional pore system constituted of intersect medium 10-ring (5.9 × 4.7 Å) pores along [001]. It was synthesized using decamethonium dihydroxide (DMDH) as structure-directing agent (SDA) from the reaction mixtures with Si/Ge = 1.5 – 4.34 This germanosilicate was successfully applied in the approach of framework transformation discussed above because it possesses the ADOR-appropriate structure characteristics: framework contains silica layers connected by hydrolytically unstable double four-member ring (D4R) units preferentially occupied by Ge atoms (Fig. 1).

Fig. 1. Projections of the UOV and IPC-12 structures: top – [100] projection, showing the top view on the layers, which remain intact after UOV–IPC-12 transformation; down – [001] projections for UOV (left) and IPC-12 (right). Unit cell parameter for UOV: a = 12.679(2) Å, b = 22.217(4) Å, c =39.058(6) Å, space group - Amm234. Unit cell parameter for IPC-12: a = 7.511(11) Å, b = 21.638(4) Å, c = 37.736(29) Å, space group - Amm223. The double fourmember ring units (D4R) in initial UOV zeolite are highlighted in red.

In this paper, we discuss the synthetic aspects, which allow producing highly crystalline IPC-12 zeolite. We pay special attention to answering following questions: 1) Which parent UOV material (possessing particular chemical composition and Ge distribution) is the most appropriate for the disassembly to obtain the lamellar precursor IPC-12P without destruction of intralayer connectivity? 2)



large 12- (7.7 × 6.0 Å and 5.9 × 7.1 Å) and small 8- (2.9 × 3.1 Å) ring channels along [100] direction, which

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Which conditions of the treatment (pH, T, duration) are optimal for separation of the UOV layers with subsequent condensation leading to IPC-12 formation?

Materials Decamethonium bromide (> 98.0 %, TCI), germanium oxide (99.99 %, Sigma Aldrich), Cab-O-Sil M5 (Supelco Analytical), hydrochloric acid (37 %, Sigma Aldrich), trichloroacetic acid (99.0 %, Sigma Aldrich), orthophosphoric acid (85 %, Fluka), sulfuric acid (95.0-98.0%, Sigma Aldrich) methanol (99.98 %, Lachner), acetone (99.97 %, Lachner). Hydrofluoric acid (48 wt. % in H2O, ANALPURE®), nitric acid (67 wt. % in H2O, ANALPURE®), hydrochloric acid (36 wt. % in H2O, ANALPURE®) supplied by Analytika, and boric acid (> 99.5 %, Sigma) were used for decomposition of zeolites. Syntheses of UOV zeolites Germanosilicate UOV samples were prepared according to Ref.34 from the reaction mixtures with the following composition: x SiO2 : (1-x) GeO2 : 0.25 DMDH : y H2O, where x = 0.33 – 0.66, y = 5 or 10, using DMDH as SDA. Decamethonium dihydroxide was prepared from the bromide form by ion exchange using Ambersep® 900(OH) anion exchange resin (0.8 mmol of SDA per 1 g of anion exchange resin). The solution of DMDH was concentrated under low pressure (25 Torr) at 30 °C until the hydroxide concentration grown to > 1.5 mol/l. For UOV synthesis, a certain amount of germanium oxide was dissolved in a water solution of DMDH. Silica (Cab-O-Sil M5) was added progressively to the solution, and the mixture was stirred at 25 °C for 30 min. After that, the reaction gels were autoclaved at 175 °C for 7 – 14 days under static conditions. The solid product was recovered by centrifugation, washed out several times with distilled water, dried at 65 °C during 12 h and finally calcined at 550 °C for 6 h with a temperature ramp of 2 °C/min under air flow (200 ml/min). The prepared UOV samples are denoted as UOV-n for diluted starting gels and UOV-n-c for concentrated ones, where n is the Si/Ge ratio in the starting reaction mixture. Treatment of UOV samples 0.1 g of calcined UOV sample was treated with 10 ml of acid solution (0.1 – 12 M HCl, 0.1 M HNO3, 0.146 M CCl3COOH, 1.4 M H3PO4 or 0.09 M H2SO4) under chosen conditions (T = 25 – 145 °C, τ = 5 min – 24 h). The solid products were isolated by centrifugation, washed thoroughly with methanol and acetone, dried at 25 °C overnight. The obtained solid was calcined at 550 °C for 6 h with a temperature ramp of 2 °C/min.



Experimental section

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Characterization The phase purity and structure of zeolites under study were verified by X-ray powder diffraction (XRD) using a Bruker AXS-D8 Advance diffractometer with a graphite monochromator and a position 0.25° (2θ/min). The chemical compositions of UOV-n samples were determined by an ICP/OES (ThermoScientific iCAP 7000) analysis. 50 mg of zeolite were mineralized in a mixture of 2 ml of HF, 4 ml of HNO3, and 4 ml of HCl in the microwave oven. After cooling, the HF excess was eliminated by the complexation with the 15 ml of saturated solution of H3BO3 and final mixture was treated in microwave oven again. Then solutions under analysis were collected and diluted by ultrapure water to total volume of 250 ml. The size and shape of UOV crystals were studied by a scanning electron microscopy (SEM, JEOL JSM-5500LV microscope). For the measurement the crystals were coated with a thin layer of platinum (~ 10 nm) in a BAL-TEC SCD-050 instrument. The

F solid-state MAS NMR spectra were acquired using a Bruker Advance III 600 MHz

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spectrometer equipped with a wide bore 14.1 T magnet. To fluorinate the sample, 0.1 g of zeolite was ground in the mortar with 0.1 g of NH4F and dried overnight. Samples were loaded into 2.5 mm rotors and rotated at MAS rates of 25 kHz. The chemical shift scale was shown relative to CCl3F. FTIR spectra were collected using a Nicolet 6700 spectrometer with a transmission MCT/B detector. The zeolites were pressed into self-supporting wafers with a density of 8.0 – 12 mg/cm2 and activated in situ at T = 450 °C and p = 5∙10–5 Torr for 4 h. All spectra were recorded with a resolution of 4 cm–1 by collecting 128 scans for a single spectrum at room temperature. The in-situ calcination of zeolite UOV hydrolyzed with 0.1 M HCl was undertaken on beamline I11 at Diamond Light Source synchrotron in Oxford, U.K. The precursor material was packed into 0.5 mm quartz capillaries and flame sealed, then heated from 30 to 400 °C in steps of 10 °C and from 400 to 900 °C in 20 °C steps, with a ramp rate of 2 °C /min using an Oxford Cryostreams hot air blower. At each step, a powder X-ray diffraction pattern was collected using a PSD detector. Two patterns were collected from 2 to 90° and from 2.25 to 90° 2θ for 10 seconds each, then summed together. Data was collected using a monochromatic beam of wavelength 0.826037 Å and had a zero point error of 0.0228° vθ.

Results and discussion Synthesis of parent UOV: assembly step



sensitive detector (Våntec-1) using CuKα radiation in Bragg-Brentano geometry at a scan rate of

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We have shown previously for different types of zeolites potentially suitable for application in ADOR20 that factors affecting the disassembly process can be divided into two groups. The first group includes the characteristics of starting material such as chemical composition and distribution of Ttype of reactant, pH, temperature and duration of the treatment. In order to investigate the influence of chemical properties of parent UOV zeolite, Si/Ge ratio (Si/Ge = 0.5 – 6) and water content (H2O/TIV = 10 for diluted and 5 for concentrated gels) were varied in the initial reaction mixtures. Table 1: Chemical compositions and crystal size of parent UOV zeolites Sample name UOV-0.5 UOV-0.5-c UOV-0.75 UOV-1 UOV-1-c UOV-1.5 UOV-2 UOV-2-c UOV-3 UOV-3-c UOV-6-c a

H2O/TIV ratio in reaction mixture 10 5 10 10 5 10 10 5 10 5 10

Starting gel 0.5 0.5 0.75 1 1 1.5 2 2 3 3 6

Si/Ge Final samplea 3.1 1.3 3.0 3.3 1.4 3.1 3.3 3.2 12.6 4.1 6.2

Crystal size, μm 0.5 x 0.4 x 0.1 2.4 x 1.8 x 0.05 0.3 x 0.4 x 0.15 0.6 x 0.2 x 0.1 3.9 x 0.3 x 0.15 0.9 x 0.7 x 0.15 1.3 x 1.3 x 0.25 1.6 x 0.6 x 0.1 1 x 0.8 x 0.15 1 x 1 x 0.2 1 x 0.5x 0.1

Phase composition UOV UOV UOV UOV UOV UOV+BEA UOV+MFI UOV+MFI MFI UOV+MFI UOV+MFI

Si/Ge ratio obtained by ICP/OES analysis.

UOV-n and UOV-n-c zeolites (XRD patterns are shown in Fig. SI-1, 2) have similar crystal morphology and are composed of plate-like crystals (Fig. SI-3, 4). In the case of UOV-n-c (n ≥ 1), crystals formed agglomerates. In contrast to the data reported by Paillaud,34 showing that UOV zeolite can be obtained as the main product at Si/Ge = 1.0 – 1.5 in reaction mixture, we synthesized UOV germanosilicate as a single phase from starting gels with higher Ge content (Si/Ge = 0.5 – 1.0, Table 1), regardless of the water content. For the syntheses carried out in diluted reaction mixtures, Si/Ge ratios in the starting gels varied in the range from 0.5 to 3.0. The highly crystalline UOV zeolites were obtained in reaction mixtures with Si/Ge = 0.5 – 1.0, while the increase in the Si/Ge ratio in the gel resulted in formation of BEA zeolite (Si/Ge = 1.5) and MFI zeolite (Si/Ge = 2) as admixtures or MFI phase even as the only product (Si/Ge = 3, Fig. SI-1). Similarly, in the case of highly-concentrated syntheses (H2O/TIV = 5) the pure phase of UOV crystallized only from gels with Si/Ge ≤ 1.0. The increase in the silicon amount in the reaction mixtures led to the formation of MFI phase along with UOV germanosilicate for UOV-n-c (n = 2.0 – 6.0).



elements (Si and Ge) in the framework; the second group consists of the treatment conditions applied:

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ICP/OES analysis of Ge-rich samples showed that water content in the reaction mixture has a strong impact on the chemical composition of final samples. Si/Ge ratios in samples obtained from concentrated starting gels were found to be twice as low if to compare with the samples isolated from This Ge enrichment of UOV-n-c may indicate that Ge atoms are located not only in the D4R units, but also in the layers, which can increase lability of the zeolite framework. As a result, the SDA-free sample UOV1-c exhibited framework instability upon storage at room temperature and atmospheric moisture for 3 months. Indeed, the XRD pattern of UOV-1-c (Fig. 2) stored for 3 months under ambient conditions shows changing positions and decreasing of all diffraction lines, which indicates recrystallization of the framework. This phenomenon can be explained by hydrolysis of Ge−O bonds by ambient air moisture similar to the behavior of some other germanium-containing zeolites after the removal of organic SDA.3536

The presence of an additional diffraction line at 26° 2θ corresponding to GeO2 indicates the removal of

Ge from the UOV framework. The instability of the layers in UOV-n-c imposed restrictions on the following investigation of these samples in the ADOR.

Fig. 2. The XRD patterns of UOV-1-c samples: as-synthesized and calcined (black) and stored for 3 months under ambient conditions (red).

Despite a remarkable change of the relative concentration of T-elements in the reaction mixture (see Table 1), the resulting materials possessed almost equal amounts of Ge (Si/Ge = 3.0 – 3.3 according to ICP/OES results). However,

F NMR spectroscopy of post-synthetically fluorinated UOV samples

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revealed some differences in the location of Ge atoms in UOV framework. While spectra of all fluorinated



diluted reaction mixtures: Si/Ge = 1.3 – 1.4 for UOV-n-c and Si/Ge = 3.1 – 3.3 for UOV-n (n = 0.5 and 1).

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samples were characterized by peaks around -10 ppm (corresponding to F- occluded in Ge4Si4 D4Rs units37) and -30 ppm (F- located in non-D4R cages, e.g. in the siliceous layer37), the gradual increase in the peak intensity at -20 ppm attributed to the Ge1Si7 units37 can be noticed with increase in the Si/Ge ratio in in 19F MAS NMR spectra of silica zeolites or zeolites not containing Ge-enriched D4R units (e.g. MFI, BEA).38

Fig. 3. A) 19F MAS NMR spectra of fluorinated zeolite samples obtained from reaction mixtures with different Si/Ge; B) characteristic low-angle region of diffraction patterns for the samples hydrolyzed with 0.1 M HCl at 25 °C for 24 h; C) respective calcined samples (full XRD patterns are presented on Fig. SI-5). Orange and grey dotted lines correspond to the positions of (100) and (013) reflections in parent UOV, respectively.

Hydrolysis of UOV: disassembly and reassembly step The structural changes taking place during the hydrolysis step were followed using XRD. For UOV zeolite, (h00) reflections characterize the distance between the individual layers. Following the shift of the positions of these peaks towards high-angles, we can determine the decrease in the interlayer distance, i.e. a completeness of the disassembly step. Thus, we evaluated the intensity and position of the interlayer peak initially located at 6.96° 2θ (100 reflection), while the maintenance of intralayer peak at 7.86° 2θ (013 reflection) evidenced the preservation of intralayer integrity upon hydrolysis step. a) Influence of Ge location in parent UOV germanosilicate. Selection of the initial material The differences in Ge distribution in the UOV samples shown above caused significant changes of UOV stability. The XRD patterns of the samples treated with 0.1 M HCl showed the presence of all intralayer reflections, but different positions of (100) diffraction line (Fig. SI-5). Hydrolysis of the material



reaction mixture from 0.5 to 2 (Fig. 3A). Noticeably, the signals at -10 – -20 ppm have never been observed

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obtained from reaction mixtures with Si/Ge = 0.5 resulted in the maximal right-shift of the interlayer (100) peak (Δ = 0.39° 2θ, Table SI-1) and formation of IPC-12P layered material. In contrast, incomplete disassembly reflected by significantly smaller shift of the respective diffraction lines (Δ = 0.20 – 0.28° 2θ, Si/Ge = 1 – 2 (Fig. 3B). The diffraction patterns of hydrolyzed and calcined UOV-0.5 and 0.75 samples corresponded to the single phase of new zeolite IPC-12 (Fig. 3C), while further increase in the Si/Ge in the initial reaction mixture resulted in the undesired stability of interlayer connectivity in UOV-1 and UOV1.5, evidenced by preservation of the peak at 6.96° 2θ ((100) reflex of original UOV zeolite) in XRD patterns of respective hydrolyzed and calcined derivatives. Based on the results of UOV-x hydrolysis, the UOV-0.5 sample prepared from the reaction mixture with the highest content of germanium (Si/Ge = 0.5) was further investigated. b) Influence of the treatment conditions In order to investigate the influence of conditions applied for disassembly of UOV zeolite, the nature of acid, pH, duration and temperature of treatment have been varied. 1. Type of reactant



Table SI-1) was observed for the samples possessing Si-enriched D4Rs synthesized from initial gels with

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Fig. 4. A) XRD patterns of UOV-0.5 treated with different acids at 25 °C (pH = 1, τ = 16 h); B) respective small-angle region, C) XRD patterns of UOV-0.5 after the treatments and calcination, D) respective small-angle region.

Firstly, solutions of 0.1 M HCl, 0.1M HNO3, 0.146 M CCl3COOH, 1.4 M H3PO4 and 0.09 M H2SO4 characterized by pH = 1 were used for the treatment of UOV-0.5 for 16 h at 25 °C. Regardless of the anion nature (Cl-, CCl3COO-, HxPO4-(3-x), HxSO4-(2-x), NO3-) all intralayer diffraction lines on the XRD patterns of treated UOV-0.5 zeolite were characterized by identical positions and similar intensities (Fig. 4A, B), while the shift of (100) reflection increased in the following order of acids: H2SO4 (0.23° 2θ) < H3PO4 (0.27° 2θ) < CCl3COOH (0.31° 2θ) < HNO3 (0.39° 2θ) = HCl (0.39° 2θ, Table SI-1). Thus, the maximum contraction of the interlayer space was observed for UOV zeolites, treated with HNO3 or HCl. The result can be explained by decreasing radius of anions intercalating IPC-12P layers in the following sequence: SO42- > PO43- > NO3- ~ Cl-.39 Nevertheless, the calcination of all UOV-0.5 samples after the treatment by different acids resulted in the formation of IPC-12 with comparable crystallinity (Fig. 4 C, D), indicating the formation of IPC-12P layered precursor at pH = 2 independently on the nature of the acid solution. In order to compare behavior UOV in acidic and basic environment, UOV-0.5 sample was also treated with 0.1 M NaOH solution at 25 °C for 16h (Fig SI-6, A-D). This resulted in total destruction of UOV framework instead of specific hydrolysis of interlayer bonds. The result reveals the preference of acidic treatment for disassembly of UOV zeolite. 2) pH and duration of the treatment In order to investigate the influence of the pH and duration of the acidic treatment on IPC-12P formation we performed kinetic study of UOV-0.5 hydrolysis with 0.1 – 12 M HCl.



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Fig. 5. XRD patterns of UOV-0.5 treated with A) 0.1 M, B) 12 M HCl at 25 °C for different times (with deconvolution for evaluation of the peak positions).

Table 2. Decrease in the interlayer d-spacing (ΔD) for UOV-0.5 zeolite, hydrolyzed in 0.1 – 12 M HCl at 25 °C for different times Time of the treatment 0 5 min 30 min 1h 3h 24h

0.1 M HCl 2θ, 100 ΔD, Å 6.96 0 7.17 0.37 7.21 0.44 7.25 0.51 7.25 0.51 7.25 0.51

1M HCl 2θ, 100 ΔD, Å 6.96 0 7.15 0.34 7.18 0.39 7.23 0.47 7.23 0.47 7.23 0.47

4M HCl 2θ, 100 ΔD, Å 6.96 0 7.08 0.21 7.08 0.21 7.08 0.21 7.09 0.23 7.09 0.23

12M HCl 2θ, 100 ΔD, Å 6.96 0 7.58 1.04 7.71 1.23 7.74 1.28 7.77 1.32 7.88 1.48

Unlike the type of acid, its concentration dramatically influences the extent and even direction of zeolite framework transformation (independently on the duration of the treatment). The increase in the HCl concentration from 0.1 to 1 and further to 4 M resulted in the suppression of hydrolysis clearly manifested by a decrease in the shift of interlayer (100) peak and preservation of the reflections (111) and (120), especially pronounced for the sample treated with 4 M acid (Table 2, Fig. SI-7 B, SI-8 C). A similar effect of disassembly inhibition with decrease in the pH was reported for ITH and ITR zeolites.20 Further increase in the HCl concentration to 12 M resulted in a maximum decrease in the interlayer distance. The prolongation of the treatment with 12 M HCl unexpectedly led to the formation of IPC-12 material that is the same as after calcination of IPC-12P synthesized using 0.1 M HCl (Fig. 5B). In other words, IPC-12 can be obtained via two different ways – either through consecutive disassembly-reassembly steps (i.e. ADOR)



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or by direct framework rearrangement under highly acidic conditions allowing silica mass-transfer similarly to “inverse sigma transformation” of UTL-to-OKO (Fig. 6).25 Thus, the behavior of UOV zeolite differs from that of UTL, which provide two different materials under direct rearrangement at very low procedure (PCR zeolite possessing interlayer connectivity via O-bridges21).

Fig. 6. Plausible mechanism of UOV-to IPC-12 transformation in 0.1 vs. 12 M HCl.

Study of the effect of the hydrolysis time showed that the interlayer (100) peak was right-shifted even after 5 minutes of the hydrolysis, similarly to UTL31 and other germanosilicate zeolites studied in the ADOR process.20 The prolongation of the acidic treatment (regardless of hydrochloric acid concentration) from 5 min to 24 h caused further shift of (100) interlayer line to high angle region, which indicates the continuing decrease in the interlayer distance in hydrolyzed samples. The maximum shift has been already reached after 1 h of the treatment for 0.1 – 4 M HCl and after that time the values were maintained: 7.25°, 7.23°, 7.09° 2θ for 0.1 M, 1 M and 4 M HCl respectively. In the case of the treatment with 12 M HCl, the maximum shift of (100) line, indicating the formation of final IPC-12 product, was found after 6 h of the treatment (XRD pattern in Fig. SI-8 D). Such rapid hydrolysis (using diluted acid) or UOV-to-IPC-12 transformation (if concentrated HCl was applied) indicates good accessibility of the D4R units via the 3dimensional pore system of UOV zeolite. Due to the high accessibility, the diffusion of hydrated H+ as well as the migration of Ge or Si-containing species is not hindered for UOV framework.



pH (OKO zeolite containing S4R units between the layers25) and multi-step disassembly-reassembly

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Fig. 7. XRD patterns of IPC-12, obtained by two different ways: by the treatment of UOV-0.5 with 0.1 M HCl followed by calcination (black) and by direct treatment with 12 M HCl (red). Diffraction line at 26° 2θ corresponds to GeO2 leached from UOV framework.

IPC-12 sample obtained from UOV-0.5 by the treatment with 12 M HCl was characterized by higher crystallinity when compared with material synthesized using diluted acid (Fig. 7). Diffraction lines of IPC-12-0.1M were less intense when compared with IPC-12-12M. This result can indicate a higher leaching of Ge from the framework of parent UOV during the treatment with 0.1 M HCl. However, chemical analysis revealed relatively close chemical composition of both samples: Si/Ge = 15 and 12 for IPC-12-0.1M and IPC-12-12M, respectively. Nevertheless, the presence of the diffraction line at 26° 2θ on XRD pattern of IPC-12-0.1M corresponding to non-framework GeO2 assumes that the real Si/Ge ratio in the framework is higher (>> 15). UOV-to-IPC-12 transformation practically did not influence the crystal morphology and IPC-12 zeolite exhibit plate-like crystals (Fig. 8).

Fig. 8. SEM images of A) UOV-0.5 and B) IPC-12 zeolites obtained by the ADOR.

FTIR spectroscopy allows us to investigate the evolution of OH groups during UOV-to-IPC-12 transformation. The parent UOV germanosilicate showed two absorption bands at ca. 3740 cm−1



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attributed to silanol groups and 3673 cm−1 related to germanols (Fig. 9). Formation of IPC-12 resulted in enhanced intensities of both bands indicating increasing amount of silanol and germanol defects upon

Fig. 9. FTIR spectra of parent UOV-0.5 (black) and IPC-12 zeolites obtained using 0.1 M HCl (red) and 12 M HCl (blue) in region of hydroxyl vibrations.

3) Temperature of the acidic treatment In order to investigate the impact of the treatment temperature, UOV-0.5 sample was treated with 0.1 and 12 M HCl at 25 °C, 105 °C and 145 °C for 3 h (Fig. 10). The temperature appeared to be a crucial parameter for hydrolysis of UOV by diluted HCl: the increase in the temperature resulted in inhibition of hydrolysis. While (100) interlayer diffraction line was found at 7.25° 2θ for the sample obtained at 25°C, respective positions of (100) reflection for samples treated at 105°C and 145°C reached only 7.10° and 7.05° 2θ, respectively. Furthermore, the diffraction lines of sample hydrolyzed at 145 °C were characterized by lower intensities, which indicate partial framework destruction. Calcination of all obtained samples at 550 °C revealed that IPC-12 can be formed just in the case of hydrolysis under ambient conditions, while calcination of samples treated at high temperature led to the reconstruction of UOV framework. The structures were defective and XRD reflections were less intensive and broader if we compare with initial UOV. Thus, the increase in the treatment temperature inhibits the disassembly process in 0.1M HCl similar to the application of acid solutions with intermediate concentrations (1 – 4M) at ambient conditions.



UOV-to IPC-12 transformation regardless the way of synthesis.

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DOI: 10.1039/C7DT03751A

In contrast, the increase in the temperature for the treatment by 12 M HCl resulted in acceleration of IPC-12 formation, but no principal difference in the outcome of transformation has been found. All reflections on XRD patterns have the same positions and similar intensities despite the difference in the



temperature (Fig. 10).

Dalton Transactions


Fig. 10. XRD patterns of UOV-0.5 treated for 3 h at different temperatures with 0.1 M HCl A) before calcination; C) after calcination; B) and D) respective small-angle region; E) XRD patterns of UOV-0.5 treated with 12 M HCl; F) respective small-angle region. Positions of (100) and (013) reflections in parent UOV are shown as orange and grey dotted lines, respectively.

In-situ calcination experiment We followed the process of IPC-12 formation from UOV sample hydrolyzed with 0.1 M HCl using in situ XRD measurement with synchrotron source during calcination from 30 to 900 °C. Obtained data (Fig. 11) indicate the right-shift of interlayer (100) and (120) peaks from 3.94° to 3.98° 2θ and from 5.81° to 5.83° 2θ at 40 °C. Further heating resulted in continuous shift of the (100) diffraction line until its merging with (013) intralayer peak at 4.26° 2θ at 200 °C. That was accompanied with the increase in intensity of (013) reflection on XRD pattern, reaching maximum value at 150 – 220 °C. For (120) diffraction line along with peak broadening the intensity decreased with increasing temperature till 440 °C, after which peak disappeared.

Fig. 11. Results of in situ XRD study upon continuous heating of IPC-12P obtained by UOV-0.5 hydrolysis with 0.1 M HCl. Merging of (100) and (013) reflections at 40 °C < T < 200 °C is shown as insert (x-axis is reverse for clarity).



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The similar phenomenon of increased peak intensity was also observed for the diffraction lines at 2.47 and 4.99° 2θ, corresponding to the (002)+(011) and (022)+(004) reflections, respectively. In contrast, the intensity of the (019) reflection at 11.29 was decreased accompanied with the peak broadening. The disappearance of interlayer (206) reflection at 10.79 can be also noticed. Calcination at high temperatures (> 700 °C) resulted in collapse of the IPC-12 framework, indicated by the loss of crystallinity after reaching the critical temperature.

Conclusions Synthetic aspects determining the extent of disassembly of germanosilicate UOV and formation of its daughter zeolite IPC-12 were addressed. Variation of parameters (chemical composition and Ge distribution in parent UOV, nature of acid, pH, temperature and duration of the treatment) allowed to establish that UOV-to-IPC-12 transformation can be carried out using two principally different approaches: by combination of hydrolysis at pH = 1 followed by calcination or by direct disassemblyreassembly at pH < –1. For success of IPC-12 formation, starting sample should possess an appropriate composition of D4R units: Ge4Si4 have to be the dominant component, while Ge1Si7 should be absent. In contrast to the nature of acid, the temperature of hydrolysis is a key parameter if diluted HCl is used and the increase in the temperature resulted in inhibition of hydrolysis. In the case of the treatment with 12 M HCl, the increase in the temperature resulted in acceleration of IPC-12 formation. According to the results of in situ XRD study, condensation of zeolite sheets of layered IPC-12P precursor to IPC-12 started at low temperature (≈ 40 °C) allowing the complete reassembly at about 200 °C. Despite UOV-to-IPC-12 transformation did not affect the crystal morphology, it resulted in significant increase in the concentration of silanol and germanol defects in the zeolite structure regardless the way of synthesis. This fact can be used for post-synthesis incorporation of heteroelements into IPC12 framework in order to design functional materials for application in catalysis or adsorption. Acknowledgements M.S. and M.O. thank the Czech Science Foundation for the support of the project 17-06524Y. M.O. and R.E.M. acknowledge OP VVV “Excellent Research Teams” project No.CZ.02.1.01/0.0/0.0/15_003/0000417– CUCAM. REM thanks the EPRSC (Grant EP/K025112) for funding work in this area. J.Č. acknowledges the Czech Science Foundation for the support of the project P106/12/G015. Authors thank Dr. D. Dawson (University of St. Andrews) for the help with NMR data.

Notes and References



DOI: 10.1039/C7DT03751A

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Electronic supplementary information (ESI) available: XRD patterns and SEM images of UOV zeolite samples obtained from diluted and concentrated reaction mixtures; XRD patterns of UOV-x (x = 0.5; 0.75; 1.0; 1.5; 2.0) samples hydrolyzed with 0.1 M HCl; XRD patterns of UOV-0.5 sample treated with 0.1; 1; 4 and 12 M HCl. For ESI see DOI:



DOI: 10.1039/C7DT03751A

Dalton Transactions


Optimization of the synthesis conditions allows top-down synthesis of novel IPC-12 zeolite by disassembly-reassembly of UOV germanosilicate



DOI: 10.1039/C7DT03751A

Ruthenium-Catalyzed Propargylation of Aromatic Compounds with

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