Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in

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Guest #ontrolled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene Loadings Daniil I. Kolokolov, Alexander Grigorievich Stepanov, and Herve Jobic J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/jp506010p • Publication Date (Web): 30 Jun 2014 Downloaded from http://pubs.acs.org on July 3, 2014

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The Journal of Physical Chemistry

Guest Сontrolled Rotational Dynamics of Terephthalate Phenylenes in Metal-Organic Framework MIL-53(Al): Effect of Different Xylene Loadings Daniil I. Kolokolov, *,†,‡ Alexander. G. Stepanov,*,†,‡ and Hervé Jobic§ †

Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090, Russia

‡

Novosibirsk State University, Faculty of Natural Sciences, Department of Physical Chemistry, Pirogova Street 2, Novosibirsk 630090, Russia §

Institut de Recherches sur la Catalyse et l’Environnement de Lyon, UMR CNRS 5256, Université Lyon 1, 2. Av. A. Einstein, 69626 Villeurbanne, France.

ACS Paragon Plus Environment

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ABSTRACT: MIL-53 is an interesting metal-organic framework (MOF) with

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“breathing”

framework which is envisioned for a number of potential applications. It is suggested that the processes of hydrocarbon adsorption, diffusion and separation by this material

is strongly

influenced by flexibility of framework and fastly moving terephtalate phenylene fragments, representing the array of molecular rotors. To govern the mentioned processes we need to learn how to monitor the flexibility of the framework and identify the specific effects of particular hydrocarbons on the rotational motion of phenylene fragments. Here we demonstrate that flexibility, i.e., Large Pore (LP) and Narrow Pore (NP) crystalline state interconversions of the framework can be monitored by following with 2H solid-state nuclear magnetic resonance the evolution of phenylene fragments dynamics with temperature. We have established that dynamics of phenylene fragments is very sensitive to the loading of xylene guests and the MOF structural state. The rotation rate is higher and the activation barrier is lower for LP state of the guest-free or loosely loaded material, whereas the NP and LP states with high loadings and dense guest packing show the decrease of the rotation rates and increase of rotation energetic barrier.

KEYWORDS Metal-Organic Frameworks, MIL-53 (Al), terephthalate phenylenes rotational dynamics, xylenes adsorption,

2

H NMR Spectroscopy.


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1. INTRODUCTION Porous metal-organic frameworks (MOFs) received much attention due to their capabilities for gas storage and hydrocarbons separation,1-2 catalysis,3 controlled drug delivery,4 optical5 and electrical properties.6-8 A distinct feature of some of MOFs, e.g., MIL-53 or MIL-88, is the flexibility of their frameworks.9-12 The peculiarities of the flexibility is strongly related with nature of the organic linker used to associate the inorganic nodes5,13-15 Depending on the structure of organic linker, some of them can exhibit internal mobility within a flexible MOF framework.16 Probing the linker internal local dynamics enables vast opportunities to reveal the response of the MOF flexible framework to the presence of guest molecules and other physical external actions like heating, mechanical stress, light irradiation or electricity. Such knowledge can be important for a deeper understanding the nature of flexibility of MOFs framework, adsorption and separation processes and be essential for characterizing controllable nano-scale molecular rotors based on MOFs2,5,16-21 MIL-53(Al) built of the aluminum terephthalates is one of the impressive representatives of flexible MOFs. It forms an array of parallel 1D rhombic microchannels with terephthalate linkers constituting the channel walls. MIL-53 is known to undergo temperature and/or adsorbate induced structural transition with a significant hysteresis.13,22-27 The reversible changes (“breathing”) occur between large-pore (LP) and narrow-pore (NP) crystalline states with the cell volumes being 1427.5(3) and 863.9(2) Å3,22 respectively. MIL-53 (Al) was shown to efficiently separate o-xylene from other isomers25 in gas phase. The framework exhibits also a complex structural phase change upon increasing the loading of the xylenes (the so called “hydrocarbon pressure” effect25) but interestingly the selectivity in separation occurs only at high loadings.25


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The terephthalate linkers in MIL-53 are capable to exhibit rotational degrees of freedom in the phenylene groups.16 These phenylene groups connected to the inorganic nodes in their para positions can perform either π-flips around the C2 symmetry axis, a continuous free diffusion around the same axis or a restricted libration in a sector.16,18,20 The rotational dynamics of terephthalate phenylenes can be sensitive to the flexibility of the MOF framework structure, i.e. to the transitions between LP and NP crystalline states. On the other hand both flexibility of the MOF framework and rotational dynamics of terephthalate phenylenes can be strongly influenced by the nature and the quantity of adsorbate molecules. In this paper, we have analyzed the MIL-53 (Al) frameworks phenylene rings rotational dynamics at different loadings of xylene isomers by solid-state 2H nuclear magnetic resonance NMR (2H NMR). 2H NMR spectroscopy is a well established and versatile tool to probe experimentally molecular mobility in different physical states including liquids28, molecular crystals,29-32 polymers33-35 and acid catalysts.36-37 It is especially adapted to study the dynamical phenomena in systems based on porous materials such as zeolites38-40 or metal-organic frameworks.16,18,20 2H NMR allows to probe the dynamics of deuterated molecules occluded in the porous materials within a broad time scale, ranging between 10-3 – 10-10 s. Here we demonstrate that transitions between LP and NP crystalline states in MIL-53 (Al) can be displayed and controlled by analyzing the evolution of rotational dynamics of terephthalate phenylenes with temperature. The hysteresis of structural transition can also be monitored by this approach for probing LP↔NP transitions. We show how the framework flexibility and dynamics of terephthalate phenylenes response on the presence of guest molecules. We have found that the rotational dynamics of phenylene rings is very sensitive to xylenes loading and this guest packing density, by slowing down the torsional motion and increasing its rotational barrier.


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2. EXPERIMENTAL SECTION 2.1 Materials. MIL-53 (Al) was prepared via hydrothermal synthesis as described earlier,26,4142

using a perdeuterated ligand (d4-Benzene-1,4-dicarboxylic acid). The synthesized material

showed a BET surface area SBET = 1250 m2 g-1. Commercially available (Sigma-Aldrich) xylene isomers were used without further purification. 2.2 Sample preparation. The preparation of the sample for

NMR

experiments was

performed by the following manner. The powder of deuterated MIL-53 (Al) (~ 0.06 g)

was

placed into a special glass cell of 5 mm diameter and 3 cm length. Then the cell was connected to the vacuum line and activated at 523 K for 6 h under vacuum. After cooling the sample back to room temperature, the material was exposed to the vapor of previously degassed xylene isomer in the calibrated volume (439 cm3) under liquid nitrogen conditions. The quantity of the adsorbed xylene isomer was regulated by the initial vapor pressure created inside the calibrated volume. In case of necessity to reach high loading of xylene (3.5 mol/u.c.), the adsorption was performed by several time steps from the calibrated volume with xylenes vapor pressure of 6 mbar. After adsorption, the neck of the tube was sealed off, while the material sample was maintained in liquid nitrogen in order to prevent its heating by the flame. Prior to NMR investigations all sealed samples were kept at 423 K for 72 hours to allow even redistribution of the guest xylene inside the porous material. 2.3 NMR measurements. 2H NMR experiments were performed at 61.424 MHz on a Bruker Avance-400 spectrometer using a high power probe with a 5 mm horizontal solenoid coil. All 2H NMR spectra were obtained by Fourier transformation of the quadrature-detected phase-cycled quadrupole echo arising in the pulse sequence (90x − τ 1 − 90 y − τ 2 − acquisition − t ) , where τ1= 20


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µs, τ2= 21 µs and t is a repetition time of the sequence during the accumulation of the NMR signal. The duration of the π/2 pulse was 1.8-2.1 µs. Spectra of deuterated MIL-53 (Al) were typically obtained with 5000-50000 scans with repetition time 1 -10 s. To capture all dynamical features of the system, the measurements were performed over a broad temperature range, from 103 K to 513 K. The temperature of the samples was controlled with a variable-temperature unit BVT-3000 with a precision of ±1 K. The sample was allowed to equilibrate at least 15 min at a given temperature before the NMR signal was acquired. Description of approaches to perform the simulations of experimental 2H NMR spectra are provided in Supporting Information.

3. RESULTS AND DISCUSSION The experimental results on deuterated phenylene rings dynamics for the large pore (LP)25 state of guest-free MIL-53 (Al) are shown in Figure 1. The 2H NMR spectrum line shape exhibits a powder pattern typical for static molecules with quadrupole constant of 176 kHz at room temperature. Above 350 K the spectrum reflects the mobility of the phenylene rings. A progressive line shape evolution with temperature is described perfectly by 2-site jump exchange with geometry corresponding to π-flip of a phenylene ring about it C2 symmetry axis. Rotational motion is performed with activation energy Ea1 = 37±1 kJ mol-1 and preexponential factor k01 =(0.6±0.2)×1010 s-1.


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Figure 1. Experimental (left columns) and simulated (right columns) temperature dependence of 2

H NMR spectrum line shape of the phenylene rings in guest-free MIL-53(Al), k is the π-flip rate

constant.

Upon adsorption of xylene the mechanism of the rotation persists but the rate drastically decreases depending on the loading (Figure 2, see also Supporting Information Figures S2, S3, S4, S5). At loading of 3.5 mol/u.c. for both para and ortho isomers of xylene the motion becomes detectable only above 473 K (k ~ 10 kHz), whereas the motion of phenylene rings is close to the fast exchange regime (k = 700 kHz at 492 K) in the guest-free (unloaded) material. Both para and ortho isomers show similar line shape evolution

with temperature

(see

Supporting Information Figures S2, S3). For loading of o-xylene with 1.5 mol/u.c. the decrease in the flipping rate is less pronounced but still obvious.


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Figure 2. Experimental (left columns) and simulated (right columns) 2H NMR spectrum line shape of the phenylene rings in MIL-53(Al) at different xylenes loadings (k is the π-flip rate constant) (T=492 K): unloaded material (a); material loaded with o-xylene: 3.5 mol/u.c (b) and 1.5 mol/u.c (d); material loaded with p-xylene: 3.5 mol/u.c (c). As in the guest-free material, at all loadings the mobile phenylene fragments involved in πflips are characterized by a single flipping rate constant k (except for the low temperature region 300-450 K and 1.5 mol/u.c loading, see Supporting Information). The temperature dependences of the flipping rate constants for all loadings are summarized in the Figure 3.


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Figure 3. Arrhenius plots of the flipping rate constants k for different loadings of xylenes: MIL53 (Al) loaded with 3.5 mol/u.c. of para (∆) and the ortho (∇) xylenes; MIL-53 (Al) loaded with 1.5 mol/u.c. of ortho xylene with measurements performed at increase of temperature from 390 to 500 K (□) and at decrease of temperature from 530 to 430 K ( ); Guest free (unloaded) MIL53(Al) ( ).

Following Finsy et al.25 it is known that upon xylenes adsorption the MOF MIL-53 exhibits consecutive phase transitions: starting from the Large Pore (LP) state to the Narrow Pore (NP) state (or the iX phase25) at loading of about 1.5 mol/u.c and then again to the LP state at loading of more than 2.5 mol/u.c. The XRD results suggest that at loading of more than 2.5 mol/u.c. the xylenes form a double layer packing inside the LP MOF channels with packing density presumably different for ortho- and para- isomers.42 The rotational parameters, rotational barriers and pre-exponential factors, derived from the Arrhenius plots are Ea2 = 51±3 kJ mol-1 , k02 = (2 ± 1)×1010 s-1 and Ea3 = 52 ±3 kJ mol-1 , k03 = (2 ± 1)×1010 s-1

for the para- and

ortho- isomers, correspondingly. Decrease of the rate and increase of activation energy for

phenylene rotations with respect to these parameters in LP state of guest-free material is


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accounted by the influence of the loaded xylene on these rotational parameters. Hence, we conclude that the dense packing (3.5 mol/u.c) of xylene affects the phenylene rings mobility by increasing the rotational barrier and decreasing the rate of rotation with respect to the guest-free material in the same LP state (vide supra). Similar influence of both isomers on rotational parameters, Ea and k0, can indicate that the packing densities of both isomers are similar at loading of 3.5 mol/u.c. At loading of 1.5 mol/u.c. one can see a more peculiar picture. The temperature dependence of the rate constant exhibits two regions. At low temperature region (390 - 430 K) the Arrhenius plot shows a higher slope with rotational parameters, Ea4 = 55 ±1 kJ mol-1 and k04 = (2.3±0.3) ×1011 s-1, which are similar to those with 3.5 mol/u.c loading case. At high temperature region (430 - 530 K) the Arrhenius plot slope is found to be less steep. It shows the rotational parameters, Ea5 = 39±1 kJ mol-1 and k05 = (0.74 ± 0.25)×1010 s-1, which are similar to those found for the guest-free material. Such result correlate with NP → LP crystalline states (phase) transitions occurring at loadings of 1.5 mol/u.c. xylene.25 This implies that the change of the slope at ~430 K of the Arrhenius plot for rotation constant is indicative of NP → LP state transition. From this result we infer that monitoring the evolution of rotational dynamics of terephthalate phenylenes with temperature can be used to follow the NP → LP state transitions in MIL-53 (Al). At low temperature region, the framework is found in the NP state and the xylene guest molecules form a monolayer.25. Xylene appears to be a relatively dense packed at NP state as the rotational barrier of 55 kJ mol-1 for phenylenes dynamics corresponds to the rotational barrier detected for the material saturated with 3.5 mol/u.c. of xylene (see Figure 4). Despite this, the


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phenylenes rings are more mobile than at high loadings of 3.5 mol/u.c. as the preexponential factor is 10 times higher. Above the transition point (~480 K), at the high temperature region, the effect of guest molecules is not sufficient to keep the NP state stable and the framework switches back to the LP state. The relatively dense packing (for NP state) of the xylenes is broken as the guest molecules have more space to move in LP state. This change is reflected in the phenylene rings dynamics, the barrier decreases from 55 to 39 kJ mol-1, i.e. it becomes only ~ 2 kJ mol-1 higher than the barrier for the guest-free material. This indicates that a xylene loading of 1.5 mol/u.c. affords no effects on rotational dynamics of phenylene rings in LP state of MIL-53(Al). The schematic representation of the effect of xylene guest loading on phenylene ring torsional barriers in NP and LP states is shown in Figure 4.

Figure 4. The effect of xylene loading on rotational barrier of terephthalate phynelenes in MIL53 (Al) channels: The guest-free material in LP phase shows (black squares) the rotational barrier ~ 37 kJ mol-1. An intermediate loading of ~1.5 mol./u.c. (blue squares) creates a loose packing which is reflected in very small increase of the torsional barriers by ~ 2 kJ mol-1. In contrast when packing density is high (3.5 mol/u.c. of p-/o-xylene LP phase or 1.5 mol/u.c. of o-xylene in NP phase) (red squares), the rotational barrier increases significantly by ~ 12 kJ mol-1.


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The observed change of phenylenes dynamics is reversible. However, the change of the slope of the Arrhenius plot for the rotation rate constant k occurs at notably lower temperature ( ~460 K). Thus, a hysteresis in the change of phenylene groups dynamics is observed. It reflects the hysteresis in reversible LP ↔NP state transitions. By scanning the temperature loop we can monitor how the terephthalate phenylene dynamics is affected by both the xylenes loadings (packing density) and different LP and NP crystalline states.

Figure 5. The hysteresis loop of the temperature driven NP→ LP phase transition at 1.5 mol/u.c. o-xylene loading is probed by the terephthalate phenylenes torsional mobility in MIL-53 (Al).

It should be noted that the spectrum line shape at transition temperatures (459 K, LN → NP; 480 K, NP → LP) reflects the co-existence of the NP and LP phases. The fit to the experimental spectrum with a single flipping rate constant (shown in the Figure 5) does not reproduce all the


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details of experimental line shape, while the best fit is reached when the fit is performed by a weighted sum of two spectral line shapes calculated with flipping rates expected for superposition of LP and NP states (see Figure 5 and additionally Supporting Information, Figures S6,S7). Such experimental finding of the NP and LP states co-existence at the phase transition hysteresis loop supports the recent theoretical studies of phase transition27,43 and is coherent with experimental findings of transition hysteresis loop in the adsorption-desorption experiments performed at fixed temperatures.16,25,27,43 Lastly we would like to discuss the observed kinetic parameters for phenylenes torsional mobility with those in other MOF type materials, in which metal oxide centers are linked together by the similar way, i.e. by terephtalate phenylenes. In Table 1, we compare our results with the results for guest-free MOFs MIL-53 (Cr) and MIL-47 (V) with similar 1D channels framework geometry and MOF-5 (Zn) and UiO-66 (Zr) that exhibit 3D porous network.


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Table 1. Activation energies and pre-exponential factors for phenylene group rotation by πflipping around CPhenyl − CCOO- bond in terephthalate linker for different MOF materials. Compound

Ea, kJ mol-1

k0, s-1

MOF-5 (Zn)

47 ± 8

0.2×1012 *

18

30 ± 2

(0.5±0.8)×1012

20

45 ± 1

(1.4±0.3)×1010*

16

41 ± 1

(2.0±0.3)×1010*

16

37±1

(0.6±0.2)×1010

This work

39±1

(0.74±0.25)×1010

This work

55±1

(2.3±0.3)×1011

This work

52±3

(2.0±1.0)×1010

This work

51±3

(2.0±1.0)×1010

This work

Reference

guest-free

UiO-66 (Zr) guest-free

MIL-47 (V) guest-free

MIL-53 (Cr) guest-free

MIL-53 (Al) guest-free

MIL-53 (Al) 1.5 mol/u.c. o-xylene LP state

MIL-53 (Al) 1.5 mol/u.c. o-xylene NP state

MIL-53 (Al) 3.5 mol/u.c. o-xylene

MIL-53 (Al) 3.5 mol/u.c. p-xylene

*

Here, the value of elementary flipping rate k0

was corrected by factor 2π (see ref. 44), which

was not taken into account in earlier estimations of k0 in refs.16 and 18.


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The comparison of the kinetic parameters among guest-free materials shows, that both the activation barrier and the pre-exponential factors depend on the framework geometry and the metal center nature. MIL-53 (Cr) and MIL-53 (Al) materials are known to have exactly the same breathing-type framework, geometry and similar structural changes with temperature and guests adsorption. At changing Al for Cr we observe a small increase of the rotational barrier by ~ 4 kJ mol-1 and increase of the preexponential factor by ~ 3 times. The steric restrictions due to intramolecular interactions of neighbor phenylenes are similar for both materials, therefore the observed difference should be purely due to the effect of electronic contributions that depend on the nature of the metal cation. The next comparison target is the MIL-47 (V). Its framework geometry is similar to the geometry of MIL-53 (Cr) and MIL-53 (Al) in the LP state, but it is rigid and there are no OH groups, which are present in MIL-53 type materials. The difference is again not so remarkable. Pre-exponential factor

for MIL-47(V) is ca. 1.4 times smaller than

that for the MIL-53 (Cr), the activation barrier is larger by 4 kJ mol-1. This leads to a slower phenylenes rotation in MIL-47 (V) compared to MIL-53 (Cr)

by 4-5 times within the

temperature range of 370-480 K. Hence we may conclude that, within one framework type, the electronic contributions may influence to a certain degree the mobility of the framework linkers, affecting both pre-exponential factor and barrier of rotation.. The situation drastically changes when we regard the MOFs with a 3D porous network, the MOF-5 and UiO-66. The pre-exponential factors for both materials are ~100 times higher than those for frameworks with 1D porous network. At the same time the activation barrier changes in a completely different manner. It increases up to 47 kJ mol-1 for the Zn based MOF-5, whereas it decreases down to 30 kJ mol-1 for the Zr based MOF UiO-66. This means that the


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barrier is very sensitive to both the electronic contributions provided by the nature of metal center and the structure of the framework. The pre-exponential factor can be interpreted as the barrierless flipping rate of the phenylene fragment. It seems natural that any intra-framework sterical effects would tend to influence pre-exponential factor.45 In 3D framework of MOF-5 and UiO-66 the phenylene fragments are rather distanced from each other and therefore might be counted as the less hindered by neighbor fragments for rotation. In MOFs with the framework composed by 1D channels the distance between linkers is considerably smaller and hence the steric restrictions are stronger. We believe this aspect is very important and should be explored further from both experimental (by synthesis of new or modified frameworks) and computational (by applying more accurate methods capable to predict the mobility of framework materials) sides. Once we introduce the guest molecules we induce additional steric restrictions for phenylene rotations. On one hand we create additional potential barrier that phenylenes need to overcome to rotate. Since the molecules adsorbed are mobile this barrier is of dynamical nature and reflects the average packing density of guests. It follows from our results that the barrier dependence on loading is of step-like manner. On the other hand we modify the pre-exponential factor by additional collisions of the rotating phenylene with guests. These collisions may increase pre-exponential factor thus increasing in average the rate of rotation. The exact value of this increase could depend on the packing density and its prediction is of fundamental interest that requires further investigations.


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4. CONCLUSIONS By means of 2H NMR we have demonstrated that the flexibility of MIL-53 (Al) framework can be detected by monitoring the evolution of the dynamics of fragments (terephthalate phenylenes)

of MOF framework with temperature. This dynamics is very sensitive to the

crystalline state (LP or NP state) of MIL-53 (Al) and loading of xylene and follows guest molecules packing density. The rate is lower and rotational barrier is higher for NP state compared to the same parameters in LP state. At loading 3.5 mol/u.c. of p-/o-xylene MIL-53 (Al) exists only in LP state for the temperature range studied. The rate is slower and barrier is higher than these parameters in the guest-free material. At loading of 1.5 mol/u.c., xylene does not produce strong effect on rotational parameters of phenylene groups for LP state, the rate is only slightly slower than that for guest-free material, while the activation energy Ea5 is similar to Ea1 (LP state) of the guest-free material. For NP state with loading of 1.5 mol/u.c., the activation energy Ea4 is similar to Ea2 for (LP state) MIL-53 with higher loading of xylene. Nevertheless phenylene rings rotate faster compared to their

rotations in LP state with higher loading. The

data obtained offers an opportunity to control the dynamics of terephthalate phenylenes in MIL53 by guest molecules loading and monitor framework flexibility of this MOF by analyzing the dynamics of the framework fragments.

ASSOCIATED CONTENT Supporting Information Details of 2H NMR spectra simulation and additional experimental 2H NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org


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AUTHOR INFORMATION Corresponding Author E-mail address: [email protected] (D.I. Kolokolov); [email protected]. (A.G. Stepanov) Fax: +7 383 330 8056

Author Contributions The manuscript was written through contributions of all authors.

Notes The authors declare no competing financial interests. ACKNOWLEDGMENT The authors would like to thank Dr. T.Yu. Kardash for characterization of MIL-53 (Al) with XRD, Dr. M.M. Tokarev for material porosity characterization and Dr. A.V. Toktarev for valuable advises and assistance in preparation of deuterated MIL-53 (Al). This work was supported in part by Russian Foundation for Basic Research (Grant No. 14-03-91333).


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REFERENCES

(1)

Férey, G. Hybrid Porous Solids: Past, Present, Future. Chem. Soc. Rev. 2008, 37,

191-214. (2)

Li, H.; Eddaoudi, M.; O'Keeffe, M.; Yaghi, O. M. Design and Synthesis of an

Exceptionally Stable and Highly Porous Metal-Organic Framework. Nature 1999, 402, 276-279. (3)

Ranocchiari, M.; van Bokhoven, J. A. Catalysis by Metal-Organic Frameworks:

Fundamentals and Opportunities. Phys. Chem. Chem. Phys. 2011, 13, 6388-6396. (4)

Horcajada, P.; Serre, C.; Maurin, G.; Ramsahye, N. A.; Balas, F.; Vallet-Regí, M.;

Sebban, M.; Taulelle, F.; Férey, G. Flexible Porous Metal-Organic Frameworks for a Controlled Drug Delivery. J. Am. Chem. Soc 2008, 130, 6774-6780. (5)

Horike, S.; Matsuda, R.; Tanaka, D.; Matsubara, S.; Mizuno, M.; Endo, K.;

Kitagawa, S. Dynamic Motion of Building Blocks in Porous Coordination Polymers. Angew. Chem.-Int. Ed. 2006, 45, 7226-7230.

(6)

Yoon, M.; Suh, K.; Natarajan, S.; Kim, K. Proton Conduction in Metal-Organic

Frameworks and Related Modularly Built Porous Solids. Angew. Chem.-Int. Ed. 2013, 52, 26882700. (7)

Ponomareva, V. G.; Kovalenko, K. A.; Chupakhin, A. P.; Dybtsev, D. N.;

Shutova, E. S.; Fedin, V. P. Imparting High Proton Conductivity to a Metal-Organic Framework Material by Controlled Acid Impregnation. J. Am. Chem. Soc. 2012, 134, 15640-15643. (8)

Sen, S.; Nair, N. N.; Yamada, T.; Kitagawa, H.; Bharadwaj, P. K. High Proton

Conductivity by a Metal-Organic Framework Incorporating Zn8O Clusters with Aligned Imidazolium Groups Decorating the Channels. J. Am. Chem. Soc. 2012, 134, 19432-19437.


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(9)

Page 20 of 25

Llewellyn, P. L.; Maurin, G.; Devic, T.; Loera-Serna, S.; Rosenbach, N.; Serre,

C.; Bourrelly, S.; Horcajada, P.; Filinchuk, Y.; Férey, G. Prediction of the Conditions for Breathing of Metal-Organic Framework Materials Using a Combination of X-ray Powder Diffraction, Microcalorimetry, and Molecular Simulation. J. Am. Chem. Soc. 2008, 130, 1280812814. (10)

Ma, M.; Bétard, A.; Weber, I.; Al-Hokbany, N. S.; Fischer, R. A.; Metzler-Nolte,

N. Iron-Based Metal–Organic Frameworks MIL-88B and NH2-MIL-88B: High Quality Microwave Synthesis and Solvent-Induced Lattice “Breathing”. Cryst. Growth Des. 2013, 13, 2286-2291. (11)

Surble, S.; Serre, C.; Mellot-Draznieks, C.; Millange, F.; Ferey, G. A New

Isoreticular Class of Metal-Organic-Frameworks with the MIL-88 Topology. Chem. Comm. 2006, 284-286. (12)

Xiao, J.; Wu, Y.; Li, M.; Liu, B.-Y.; Huang, X.-C.; Li, D. Crystalline Structural

Intermediates of a Breathing Metal–Organic Framework That Functions as a Luminescent Sensor and Gas Reservoir. Chem. - Eur. J. 2013, 19, 1891-1895. (13)

Férey, G.; Serre, C. Large Breathing Effects in Three-Dimensional Porous Hybrid

Matter: Facts, Analyses, Rules and Consequences. Chem. Soc. Rev. 2009, 38, 1380. (14)

Kitagawa, S.; Kitaura, R.; Noro, S. Functional Porous Coordination Polymers.

Angew. Chem. Int. Ed. 2004, 43, 2334.

(15)

Long, J. R.; Yaghi, O. M. The Pervasive Chemistry of Metal-Organic

Frameworks. Chem. Soc. Rev. 2009, 38, 1213-1214. (16)

Kolokolov, D. I.; Jobic, H.; Stepanov, A. G.; Guillerm, V.; Devic, T.; Serre, C.;

Férey, G. Dynamics of Benzene Rings in MIL-53(Cr) and MIL-47(V) Frameworks Studied by 2H NMR Spectroscopy. Angew. Chem. Int. Ed. 2010, 49, 4791-4794.


20

Page 21 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(17)

Kottas, G. S.; Clarke, L. I.; Horinek, D.; Michl, J. Artificial Molecular Rotors.

Chem. Rev. 2005, 105, 1281-1376.

(18)

Gould, S. L.; Tranchemontagne, D.; Yaghi, O. M.; Garcia-Garibay, M. A.

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment. J. Am. Chem. Soc. 2008, 130, 3246-3247. (19)

Comotti, A.; Bracco, S.; Valsesia, P.; Beretta, M.; Sozzani, P. Fast Molecular

Rotor Dynamics Modulated by Guest Inclusion in a Highly Organized Nanoporous Organosilica. Angew. Chem., Int. Ed. 2010, 49, 1760-1764.

(20)

Kolokolov, D. I.; Stepanov, A. G.; Guillerm, V.; Serre, C.; Frick, B.; Jobic, H.

Probing the Dynamics of the Porous Zr Terephthalate UiO-66 Framework Using 2H NMR and Neutron Scattering. J. Phys. Chem. C 2012, 116, 12131-12136. (21)

Comotti, A.; Bracco, S.; Ben, T.; Qiu, S. L.; Sozzani, P. Molecular Rotors in

Porous Organic Frameworks. Angew. Chem., Int. Ed. 2014, 53, 1043-1047. (22)

Liu, Y.; Her, J. H.; Dailly, A.; Ramirez-Cuesta, A. J.; Neumann, D. A.; Brown, C.

M. Reversible Structural Transition in MIL-53 with Large Temperature Hysteresis. J. Am. Chem. Soc. 2008, 130, 11813-11818.

(23)

Mendt, M.; Jee, B.; Stock, N.; Ahnfeldt, T.; Hartmann, M.; Himsl, D.; Poppl, A.

Structural Phase Transitions and Thermal Hysteresis in the Metal−Organic Framework Compound MIL-53 As Studied by Electron Spin Resonance Spectroscopy. J. Phys. Chem. C 2010, 114, 19443–19451. (24)

Coudert, F. X.; Mellot-Draznieks, C.; Fuchs, A. H.; Boutin, A. Double Structural

Transition in Hybrid Material MIL-53 upon Hydrocarbon Adsorption: The Thermodynamics Behind the Scenes. J. Am. Chem. Soc. 2009, 131, 3442-3443.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(25)

Page 22 of 25

Finsy, V.; Kirschhock, C. E. A.; Vedts, G.; Maes, M.; Alaerts, L.; De Vos, D. E.;

Baron, G. V.; Denayer, J. F. M. Framework Breathing in the Vapour-Phase Adsorption and Separation of Xylene Isomers with the Metal-Organic Framework MIL-53. Chem. -Eur. J. 2009, 15, 7724-7731.

(26)

Loiseau, T.; Serre, C.; Huguenard, C.; Fink, G.; Taulelle, F.; Henry, M.; Bataille,

T.; Ferey, G. A Rationale for the Large Breathing of the Porous Aluminum Terephthalate (MIL53) upon Hydration. Chem.- Eur. J. 2004, 10, 1373-1382. (27)

Triguero, C.; Coudert, F. X.; Boutin, A.; Fuchs, A. H.; Neimark, A. V.

Understanding Adsorption-Induced Structural Transitions in Metal-Organic Frameworks: From the Unit Cell to the Crystal. J. Chem. Phys. 2012, 137, 184702-184709. (28)

Hindman, J. C.; Svirmick.A. Relaxation Processes in Water - Spin-Lattice

Relaxation of D2O in Supercooled Water. J. Phys. Chem. 1973, 77, 2487-2489. (29)

Wittebort, R. J.; Usha, M. G.; Ruben, D. J.; Wemmer, D. E.; Pines, A.

Observation of Molecular Reorientation in Ice by Proton and Deuterium Magnetic Resonance. J. Am. Chem. Soc. 1988, 110, 5668-5671.

(30)

Collins, M. J.; Ratcliffe, C. I.; Ripmeester, J. A. 2H Nmr and 33S Nmr Line-Shape

Studies of the Molecular-Motion in the Liquid and Solid-Phases of Hydrogen-Sulfide and the Solid II Phase of Hydrogen Selenide. J. Phys. Chem. 1989, 93, 7495-7502. (31)

Kolokolov, D. I.; Glaznev, I. S.; Aristov, Y. I.; Stepanov, A. G.; Jobic, H. Water

Dynamics in Bulk and Dispersed in Silica CaCl2 Hydrates Studied by 2H NMR. J. Phys. Chem. C 2008, 112, 12853-12860. (32)

Nishchenko, A. M.; Kolokolov, D. I.; Stepanov, A. G. Mobility of Solid tert-Butyl

Alcohol Studied by Deuterium NMR. J. Phys. Chem. A 2011, 115, 7428-7436.


22

Page 23 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(33)

Jelinski, L. W. Deuterium NMR of Solid Polymers. In High Resolution NMR

Spectroscopy of Synthetic Polymers in Bulk (Methods and Stereochemical Analysis); Komoroski,

R. A., Ed.; VCH Publishers: New York, 1986; Vol. 7; pp 335. (34)

Wendoloski, J. J.; Gardner, K. H.; Hirschinger, J.; Miura, H.; English, A. D.

Molecular-Dynamics in Ordered Structures - Computer-Simulation and Experimental Results for Nylon-66 Crystals. Science 1990, 247, 431-436. (35)

De Paul, S. M.; Zwanziger, J. W.; Ulrich, R.; Wiesner, U.; Spiess, H. W.

Structure, Mobility, and Interface Characterization of Self-Organized Organic-Inorganic Hybrid Materials by Solid-State NMR. J. Am. Chem. Soc. 1999, 121, 5727-5736. (36)

Di Benedetto, S.; Chidichimo, G.; Golemme, A.; Imbardelli, D. Water Dynamics

in Na3PW12O40 nH2O: a 2H-NMR and 31P-NMR Investigation. J. Phys. Chem. 1996, 100, 80798084. (37)

Kolokolov, D. I.; Kazantsev, M. S.; Luzgin, M. V.; Jobic, H.; Stepanov, A. G.

Direct 2H NMR Observation of the Proton Mobility of the Acidic Sites of Anhydrous 12Tungstophosphoric Acid. ChemPhysChem 2013, 14, 1783-1786. (38)

Stepanov, A. G.; Shubin, A. A.; Luzgin, M. V.; Shegai, T. O.; Jobic, H. Dynamics

of n-Hexane Inside Silicalite, as Studied by 2H NMR. J. Phys. Chem. B 2003, 107, 7095-7101. (39)

Saengsawang, O.; Schuring, A.; Remsungnen, T.; Loisruangsin, A.; Hannongbua,

S.; Magusin, P.; Fritzsche, S. Rotational Motion of Pentane in the Flat Gamma Cages of Zeolite KFI. J. Phys. Chem. C 2008, 112, 5922-5929. (40)

Nishchenko, A. M.; Kolokolov, D. I.; Gabrienko, A. A.; Stepanov, A. G. Mobility

of tert-Butyl Alcohol in MFI Framework Type Studied by Deuterium NMR. J. Phys. Chem. C 2012, 116, 8956-8963.


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(41)

Page 24 of 25

Lieder, C.; Opelt, S.; Dyballa, M.; Henning, H.; Klemm, E.; Hunger, M.

Adsorbate Effect on AlO4(OH)2 Centers in the Metal-Organic Framework MIL-53 Investigated by Solid-State NMR Spectroscopy. J. Phys. Chem. C 2010, 114, 16596-16602. (42)

Alaerts, L.; Maes, M.; Giebeler, L.; Jacobs, P. A.; Martens, J. A.; Denayer, J. F.

M.; Kirschhock, C. E. A.; De Vos, D. E. Selective Adsorption and Separation of orthoSubstituted Alkylaromatics with the Microporous Aluminum Terephthalate MIL-53. J. Am. Chem. Soc. 2008, 130, 14170-14178.

(43)

Boutin, A.; Springuel-Huet, M. A.; Nossov, A.; Gedeon, A.; Loiseau, T.;

Volkringer, C.; Férey, G.; Coudert, F. X.; Fuchs, A. Breathing Transitions in MIL-53(Al) MetalOrganic Framework Upon Xenon Adsorption. Angew. Chem. Int. Ed. 2009, 48, 8314. (44)

Hirschinger, J.; Miura, H.; Gardner, K. H.; English, A. D. Segmental Dynamics in

the Crystalline Phase of Nylon-66: Solid-State 2H NMR. Macromol. 1990, 23, 2153-2169. (45)

Shustova, N. B.; Ong, T. C.; Cozzolino, A. F.; Michaelis, V. K.; Griffin, R. G.;

Dinca, M. Phenyl Ring Dynamics in a Tetraphenylethylene-Bridged Metal-Organic Framework: Implications for the Mechanism of Aggregation-Induced Emission. J. Am. Chem. Soc. 2012, 134, 15061-15070.


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Guest Controlled Rotational Dynamics of Terephthalate Phenylenes in

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