Mechanism of AlcoholâWater Separation in MetalâOrganic Frameworks

Article pubs.acs.org/JPCC

Mechanism of Alcohol−Water Separation in Metal−Organic Frameworks Guilherme F. de Lima,†,‡ Andreas Mavrandonakis,† Heitor A. de Abreu,‡ Hélio A. Duarte,‡ and Thomas Heine*,† †

Center for Functional Nanomaterials (NanoFun), School of Engineering and Science, Jacobs University Bremen gGmbH, Campus Ring 1, 28759 Bremen, Germany ‡ GPQIT, Departamento de Química − ICEx, Universidade Federal de Minas Gerais, Avenida Antônio Carlos, 31270-901, Belo Horizonte − MG, Brazil S Supporting Information *

ABSTRACT: The metal−organic framework Zn2(BDC)2(TED) (1) has been reported to be water-stable and highly selective toward the adsorption of water and alcohols, suggesting the application of this material as a separation membrane for the production of bioethanol. We have studied the adsorption mechanism of water, methanol, ethanol, and dimethylether in this framework by means of density-functional theory with corrections for London dispersion. We show that the combination of the hydrogen bond between the hydroxyl group in ethanol with the oxy group in 1 and the van der Waals interaction between the ethanol alkyl chain with the phenyl ring in 1 is responsible for the preferential adsorption of ethanol over water in the framework. The calculated enthalpy of adsorption for the four compounds in 1 is in excellent agreement with experimental results. We further note that the computational approach has to be chosen with care: It is essential to account for London dispersion interactions, as well as the use of large models, preferably the full periodic structure, to obtain correct adsorption geometries and energies.

1. INTRODUCTION Global climate change and limitations of the supply of fossil fuels require renewable energy sources to satisfy the demand of the industrialized societies. One possibility is the use of biofuels, derivates from plants such as sugar cane, corn, soy, and so on.1−3 The production of bioethanol as gasoline replacement has a tradition of more than 40 years in Brazil,4 where sugar cane is fermented, enriched, and purified to be used as car fuel.3,5 In this process, the net energy balance (NEB), the difference between the energy produced by the fuel and the energy spent to make it, is only ∼25% due to large energy demands in the distillation and purification process.6 This value is significantly lower than that of biodiesel with a NEB of almost 95%. The low NEB of bioethanol is caused mainly by the fact that energy-demanding distillation is used for ethanol enrichment and that a molecular sieve,5,7−10 typically a zeolite like NaA or T,11,12 is required to purify ethanol above the azeotropic point, and high temperatures are necessary to break the strong water−ion interactions inside the zeolite pores tin order to recycle these molecular sieves. An alternative production method, where a molecular sieve directly separates fuel-grade (98 wt %) ethanol from the filtered fermentation product, would hence increase the NEB significantly and provide an enormous economic and ecological impact.5,9,10,13 Metal organic frameworks (MOFs) are a relatively new class of crystalline porous materials discovered in the mid-1990s. They are formed by an inorganic metal or metal oxide unit connected by organic linkers.14 The possibility to change the © XXXX American Chemical Society

metal atoms and also the organic linkers makes MOFs a materials class with very large diversity, thus offering the possibility of application in several fields. Much attention has been paid to the performance of these materials for hydrogen storage,15−17 with some MOFs showing remarkable hydrogen uptake,18−20 and they have also been explored for carbon dioxide capture,21 sensors,22 biomedicine,23 heterogeneous catalysis,24 and chemical separation.25−27 Some MOFs show the ability to distinguish between ethanol and water,8,28 and this property could be used to produce membranes for bioethanol purification. In 2007, Lee and coworkers reported an MOF that adsorbs ethanol (EtOH), methanol (MeOH), and dimethylether (DME), but not water, at room temperature and ambient pressure.28 The framework of composition Zn2(BDC)2(TED) (1) [BDC: benzene-1,4-dicarboxylate; TED: triethylenediamine] is a MOF formed by a Zn2(COO)4 paddle wheel (PW) connected to BDC linkers along the x and y directions and the TED pillars along the z direction (structure V in Scheme 1). This material has a hydrophobic cavity formed by two interlacing channels with sizes 7.5 × 7.5 Å and 4.8 × 3.2 Å and it does not decompose at temperatures up to 300 °C.28 Few studies have been dedicated to understand the mechanism of separation of water−alcohol mixtures by Zn2(BDC)2(TED). Received: December 14, 2012 Revised: January 31, 2013

A

dx.doi.org/10.1021/jp312323b | J. Phys. Chem. C XXXX, XXX, XXX−XXX

The Journal of Physical Chemistry C

Article

D3,40,41 and B3LYP-D341,42 functionals with the Def2TZVPP basis, as implemented in Turbomole.43 The adsorption energy was evaluated considering the process described by eq 1, in which the first and second terms in the left-hand side are the models used to describe the MOF (I−IV) and the guest molecule, respectively. The term in the right-hand side is the complex formed by the adsorbed molecule in 1.

Scheme 1. (I) TED and (II) BDC Linkers of 1, (III) Cluster Models 1−2 and (IV) 1−6, and (V) Periodic Model of 1

1(g) + guest(g) → [1···guest](g)

(1)

The Gibbs free energy (ΔG) of adsorption was calculated by eq 2 ΔG = ΔE + ΔHT − T ΔS

(2)

In eq 2, ΔE is the total electronic energy corrected by the counterpoise method proposed by Boys and Bernardi.44 The second term, in the right-hand side of eq 2, is the thermal correction for enthalpy, which includes the zero-point energy and the pV term, and the third term is the entropy contribution. Both were calculated from the harmonic analysis performed on the optimized structures. The enthalpy of adsorption (ΔH) was calculated according eq 3.

Chen et al.29 applied grand canonical Monte Carlo calculations to analyze the adsorption and separation of methanol and water in 1. With this study, they were able to define three different sites of interactions, and also a selectivity of 20 for methanol− water mixtures at 1 kPa, which decreases with the increase in temperature, has been reported. Although this material provides the selectivity, unfortunately, the idea to use it as molecular sieve for ethanol−water separation has not been followed intensively. Because industrial application requires the production of large amounts of MOF material and because the production of water-stable MOFs is not always straightforward, one needs to be able to propose alternative frameworks with similar or even improved selectivity. Therefore, it is imperative to understand the separation mechanism in 1. In this work, we identify the MOF components that enable the selectivity of 1 and provide insights to design alternative frameworks that may separate liquid mixtures with phases of different functional groups.

ΔH = ΔE + ΔHT

(3)

A comparison in terms of geometry and energy of the complexes optimized at different DFT levels and at the MP2/ Def2-TZVPP level is presented in the Supporting Information (SI). The adsorption of the guest molecules in III and IV was calculated using the same strategy described above with the DFT functionals PBE-D3 and BLYP-D3 and the Def-SV(P) basis set. A comparison of geometries and energies of the optimized structures is shown in the SI. Calculations of the periodic MOF structure were carried out with the PBE functional using the Grimme’s dispersion correction of 2006 (D2),45 as implemented in VASP 5.2.46 The geometric structure and lattice parameters of one unit cell (V, in Scheme 1) were fully optimized without any symmetry constrains. The optimized lattice parameters agree within 1% with the experimental ones;47 details are shown in the SI. The core electrons were described by projected-augmented waves (PAWs),48 whereas the valence electrons were expanded in plane waves with a cutoff of 800 eV in the kinetic energy. A grid of 2 × 2 × 2 k-points, centered at Γ-point, was sampled in the Brillouin zone using the Monkhorst-pack scheme.49 The vibrational frequencies were obtained through a harmonic analysis within the Γ-point approximation. They confirm that the optimized structures are minima in the potential energy surface and enable us to calculate the zero point energy and thermodynamic functions. The adsorption of the guest molecules in the solid structure of 1 was calculated considering the process indicated in eq 4.

2. MODELS AND COMPUTATIONAL DETAILS The adsorption of EtOH, MeOH, DME, and H2O in 1 was investigated considering different models to describe the MOF, as shown in Scheme 1. In our simplest models (I and II in Scheme 1), 1 is described just by its linkers TED and BDC, respectively. The strategy of using only linkers to represent the MOF was widely used to study H2 adsorption in MOF-5, for example.30−37 Although these models allow the study of the weak interactions between the aromatic ring in BDC and the ethyl group in TED with the guest molecules, they neglect any information about the porous structure of 1. They do not permit, in addition, the study of hydrogen bonds between the guest molecules with oxy group in 1. Models III (cluster 1−2) and IV (cluster 1−6) were built to analyze these hydrogen bonds. Both models contain the Zn2(COO)4 PW structure and two TED linkers in the axial positions (Scheme 1). The carboxylates are saturated either by hydrogen atoms (model III) or by phenyl linkers (model IV). Finally, model V is the unit cell of 1 considered for periodic calculations. DFT calculations using the dispersion correction proposed by Grimme et al.38 (D3) in 2010 were carried out to analyze the adsorption of the guest molecules at the distinct molecular models built to describe 1. For models I and II, several van der Waals complexes considering different conformations of the guest molecules were optimized using PBE-D3,39 BLYP-

V(s) + guest(g) → [V ···guest](s)

(4)

In eq 4, V(s) corresponds to the solid structure of 1, the second term in the left-hand side is the guest molecule calculated in a box with the same dimension and the k-points used to calculate the solid structure, and the term on the right-hand site is the solid with the guest molecule adsorbed in its pores. Because the guest molecules are considered in the gas phase, the thermal corrections for enthalpy and entropy were added separately,50 as discussed in detail in the SI. B



Article

3. RESULTS AND DISCUSSION The preferential selectivity of 1 for EtOH, MeOH, and DME in comparison with H2O was investigated by analyzing the adsorption of these guest molecules in 1 considering different models to describe the MOF, as shown in Scheme 1. For the molecular models (I−IV) used to represent 1, the adsorption process is calculated considering eq 1. Because DFT does not describe weak interactions correctly, the use of dispersion-corrected methods like those proposed by Grimme38,45,51 are essential for the description of the adsorption process. First, the performance of three dispersion-corrected functionals was analyzed. Using models I and II, the interaction with the guest molecules was calculated considering the generalized gradient approximations (GGAs) PBE-D3, BLYP-D3, the hybrid functional B3LYP-D3, and the second-order perturbation theory of Møller and Plesset (MP2). First, a series of different adsorption complexes were optimized considering different adsorption sites between the guest molecules with I and II. The geometrical parameters of the complexes, optimized at the different levels of theory, are in very close agreement with each other (see Figures S1 and S2 in the SI). In Table 1, the adsorption energies, that is, the

Figure 1. Optimized structures of (a) H2O, (b) EtOH, and (c) MeOH adsorbed in cluster model 1−2. Zn (orange), C (green), O (red), N (blue), and H (white).

as shown in Figures S3 and S4 (see SI). Both functionals give very similar energies, as shown in Tables S3 and S4 in the SI. With these findings, we conclude that London-dispersioncorrected GGA (i.e., PBE) is an excellent choice for the further calculations. The selectivity of a MOF is related to the Gibbs free energy of adsorption (ΔG = ΔH − TΔS) differences of the guest molecules with the framework at the thermodynamic conditions applied. When introducing the concept of reticular chemistry,52,53 the properties of MOFs appear to be strongly linked to those of their individual building blocks. In our case, models I and II do not lead to conclusive results (Table 2). Obviously, in the case of host−guest interactions with larger guests, it is an oversimplification to approximate the MOF functionality by individual building blocks. This shortcoming gets evident if larger MOF models, incorporating three and even seven building blocks, as shown in Figures 1 and 2, are considered: the guest molecules arrange in such way that their functional hydroxyl group forms a hydrogen bond with an oxygen atom of the connector, whereas the remainder is oriented to a hydrophobic linker site. When approaching a large cluster model for 1, the calculated heats of adsorption get similar to the experimental ones reported by Lee et al.28 Excellent agreement with experiment is achieved for the periodic model, where heats of adsorption agree within 10 kJ mol−1 (Table 2). The difference in the enthalpy of adsorption of ethanol and methanol in 1 is calculated to be −4.5 and −7.2 kJ mol−1 using models IV and V, respectively. These values are in very good agreement with the differences of 6.3 kJ mol−1 measured by Lee et al. for 128 and similar to the 5.0 kJ mol−1 estimated by Bourrelly et al. for a different MOF, MIL53(Cr).54 We have estimated the contribution of the dispersion energy to the interaction between the guest molecules and 1. For the small models I and II, the London dispersion was estimated as the MP2 correlation energy.36Our results (Table S7 in the SI) indicate that this contribution is dominant in the interaction energy (Table 1), suggesting that the interaction between the guest molecules with I and II in governed by dispersion. Because the PBE functional already includes a part of the London dispersion,55 the D3 corrections cannot be understood as the entire London dispersion contribution to the electronic energy. As shown in Table S7 in the SI, especially in calculations with model II, the dispersion contribution should be higher due to the aromatic ring of BDC. However, the results indicate the importance of the dispersion corrections to the density functional, as lacking this substantial energy

Table 1. Interaction Energies between Guest Molecules and Models I and IIa,b,c ΔE complex

PBE-D3

BLYP-D3

B3LYP-D3

MP2

I−H2O I-EtOH I-MeOH I-DME II−H2O II-EtOH II-MeOH II-DME

−10.4 −14.9 −12.4 −13.9 −11.0 −15.7 −21.3 −14.6

−9.6 −15.1 −13.3 −14.9 −6.8 −12.1 −15.1 −11.7

−9.7 −14.3 −12.3 −14.4 −10.6 −15.2 −19.6 −14.8

−7.5 −10.5 −9.8 −11.3 −8.2 −14.9 −16.4 −13.3

a All values are in kilojoules per mole. bCalculations were carried out with Def2-TZVPP basis set. cFor a comparison between the thermodynamics properties, see Tables S1 and S2 in the Supporting Information.

interaction energies between the guest molecules EtOH, MeOH, DME, and H2O and models I and II, respectively, are presented for the lowest energy complexes found in our study. Again, the agreement between the different DFT methods is very good, with differences no larger than 2 kJ mol−1. The MP2 method gives systematically larger interaction energies with differences of ∼3 kJ mol−1. The same good agreement was obtained for the thermodynamic properties and hence for the interaction free enthalpy, as shown in Tables S1 and S2 in the SI. We can conclude that the London-dispersioncorrected GGA methods are sufficient to describe the studied host−guest interactions with the linkers very well. Models III and IV were designed to represent the PW structure. It is an important structural element because the guest molecules can interact with oxygen atoms in the PW via hydrogen bonds. Figures 1 and 2 show the optimized structures of the most stable complexes formed by the guest molecules with III and IV, respectively, at the PBE-D3 level. Analogue calculations were performed at the BLYP-D3 level, resulting in very similar structures. Both functionals give equivalent complexes with differences in the hydrogen bond length no larger than 0.03 Å and angles O(OH)−H(OH)···O(PW) within 5°, C



Article

Figure 2. Optimized structures of (a) H2O, (b) EtOH, and (c) MeOH adsorbed in cluster model 1−6. Zn (orange), C (green), O (red), N (blue), and H (white).

Table 2. Enthalpy of Adsorption and Gibbs Free Energy (in Parentheses) for the Adsorption of H2O, EtOH, MeOH, and DME in Different Molecular Models (I−IV) and in the Periodic Structure (V) of 1a,b Ic −5.2 −9.6 −7.1 −8.5

H2O EtOH MeOH DME

IIc −7.0 −10.8 −15.5 −9.6

(16.9) (22.8) (22.2) (21.9)

(16.0) (21.0) (15.6) (24.5)

IIId

IVd

Ve

exp.f

−32.3 (7.9) −37.8 (9.1) −36.7 (8.9)

−37.0 (10.7) −48.3 (1.7) −43.8 (5.5)

−42.9 (−4.2) −57.4 (−15.8) −50.2 (−7.0)

−45.4 −65.8 −59.5 −30.3

a

Values in kilojoules per mole. bThermodynamic properties calculated at 298.15 K and 0.1 MPa. cCalculated at PBE-D3/Def2-TZVPP level. Calculated at PBE-D3/def-SV(P) level. eCalculated at PBE-D2/plane waves, cutoff 800 eV level. fQuoted from isosteric heat of adsorption in the Henry’s Law region in ref 28. d

nation of the heat of adsorption,28 we can now provide detailed atomistic understanding of this process: The Zn2(COO)4 PW, the principal constituents of the connectors of 1, provides in the form of its oxygen atoms the hydrophilic sites that are necessary to attract the protons of the hydroxyl groups that are present in water as well as in the alcohols. The phenyl rings, present in the BDC ligands, provide a hydrophobic element that attracts the alkyl chains of the alcohols but not the remaining proton of water. Figures 2b and 3b show the alkyl chain of EtOH bended toward the phenyl ring to increase the van der Waals interaction between the guest molecule and the linker. Similar conclusions have been obtained by Bourrelly et al. in their study about water/alcohol adsorption in MIL53(Cr), with the difference that this MOF has not only the oxygen of carboxyl groups as hydrophilic sites but also OH groups linking chains of octahedra, which will also interact with the guest molecules.54 It is important to note that the correct geometry of the adsorbed molecules can only be understood if a large MOF model, at least incorporating the connector and six ligand units (cluster model 1−6 as IV, in Scheme 1), or even better the full periodic structure, is taken into account. For the smaller models, even in cluster model 1−2 that incorporates the connector with two pillar molecules, the distance of the protons of water to the hydrophilic site, O−H(H2O)···O(PW), is 1.94 Å, whereas this bond is significantly shortened in the larger models (1.78 and 1.80 Å for cluster model 1−6 and the periodic model, respectively); see Figures S3 and S4 in the SI. In the insufficient model 1−2, both hydrogen atoms of water interact with oxygen atoms in the PW (Figure 1a), forming an angle ∠O···H−O of ∼150°. For the larger model 1−6 and the periodic structure, just one hydrogen atom interacts with the PW with an angle close to 180°, as shown in Figure 2a. Details of the structural parameters of the adsorbed molecules are given in the SI. In agreement with the experiment of Lee et al.,28 our calculated heats of adsorption indicate stronger interaction of

contribution would alter the conclusions of this study. To understand this, the London dispersion correction between the framework models and the guest molecules have been calculated (D3 contribution for finite models III and IV and D2 contribution for periodic model V). Our results, shown in Table 3, indicate that indeed the dispersion correction is a Table 3. Interaction Energy and London Dispersion Energy for the Interaction between the Guest Molecules and III, IV, and Va IIIb

IVb

Vc

guest molecules

ΔE

ΔEdisp

ΔE

ΔEdisp

ΔE

ΔEdisp

H2O EtOH MeOH

−41.1 −44.7 −43.8

−11.9 −21.1 −16.6

−45.8 −56.2 −51.7

−19.7 −33.9 −24.0

−46.4 −61.4 −53.6

−17.9 −35.3 −30.6

a

All values in kilojoules per mole. bCalculated at PBE-D3/Def2TZVPP level. cCalculated at PBE-D2/plane waves (cutoff = 900 eV) level.

significant component of the interaction energy. For the interaction between the water molecule, with models III, IV, and V, for example, the dispersion correction accounts for 30, 43, and 40% of the interaction energy, respectively. For ethanol, which can interact with the aromatic ring on BDC with the ethyl group, the dispersion correction reaches values around 50% (Table 3). The D2 contribution to the interaction energy between EtOH with V is ∼5 kJ mol−1 stronger than that for the interaction between MeOH and V. This is, approximately, the observed difference in ΔG (Table 2). Therefore, the inclusion of dispersion corrections into the density functional is crucial for a correct description of the interaction between the guest molecules and 1. Whereas the selectivity of 1 was manifested experimentally by adsorption measurements and rationalized by the determiD



Article

London-dispersion corrections contribute a large amount to the host−guest interaction energy. On the basis of dispersion-corrected DFT calculations, we can now suggest a design concept for MOF-based molecular sieves with this property: The water stable framework requires spatially isolated hydrophilic sites that allow hydrogen bonding with the guest molecules. To separate water from ethanol or other alcohols, a hydrophobic site needs to be placed nearby to attract the alkyl group of the alcohol molecule. The size of this site may further be used to discriminate between alcohols with different alkyl chains as the length of the hydrophobic linker should match the chain length of the alcohol. With these insights, it may be possible to design further frameworks that may serve as molecular sieves for biofuel production. Further calculations and experimental work should be carried out to confirm, extend, and improve this concept.

■

ASSOCIATED CONTENT

S Supporting Information *

Geometric and structural comparison for the complexes between I, II, III, and IV and the guest molecules at PBE-D3, BLYP-D3, B3LYP-D3, and MP2 level, details about the solid state calculations, and the coordinates of the optimized structures. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Author Contributions

The manuscript was written through contributions of all authors. Notes

The authors declare no competing financial interest.

■

Figure 3. View along [001] and [100] directions for (a) water, (b) ethanol, and (c) methanol adsorption in 1. Zn (orange), C (green), O (red), N (blue), and H (white).

ACKNOWLEDGMENTS Financial support by joint CAPES/DAAD action PROBRAL, DFG SPP 1362 (HE 3543/7-2, MA 532/1), and the European Commission FP7Marie Curie TEMM1P PIRSES-GA-2011295172, the European Research Council through FP7-IDEASERC-StG-256962, and the Brazilian National Institute of Science and Technology − INCT-Acqua is gratefully acknowledged.

ethanol than methanol with the MOF; however, the adsorption isotherms indicate that 1 adsorbs almost two times more MeOH than EtOH molecules. This can be rationalized in the following way: both molecules interact through their hydroxyl groups with the PW of the MOF, but the EtOH bends toward the aromatic ring to increase its hydrophobic van der Waals interactions. This geometric arrangement is occupying a bigger space and results in a lower number of EtOH molecules inside the pores. Our rationalization would suggest that also other well-known MOFs, such as MOF-5,56 should offer reasonably high water− ethanol selectivity. However, a crucial property of a sieve to purify bioethanol is water stability, a property that is unfortunately not present in MOF-5 and many other MOF materials.

■

REFERENCES

(1) Balat, M.; Balat, H.; Ö z, C. Progress in Bioethanol Processing. Prog. Energy Combust. Sci. 2008, 34, 551−573. (2) Balat, M.; Balat, H. A Critical Review of Bio-Diesel as a Vehicular Fuel. Energy Convers. Manage. 2008, 49, 2727−2741. (3) Demirbas, A. Progress and Recent Trends in Biodiesel Fuels. Energy Convers. Manage. 2009, 50, 14−34. (4) Goldemberg, J. The Ethanol Program in Brazil. Environ. Res. Lett. 2006, 1, 014008−014013. (5) Huang, H.-J.; Ramaswamy, S.; Tschirner, U. W.; Ramarao, B. V. A Review of Separation Technologies in Current and Future Biorefineries. Sep. Purif. Technol. 2008, 62, 1−21. (6) Hill, J.; Nelson, E.; Tilman, D.; Polasky, S.; Tiffany, D. Environmental, Economic, and Energetic Costs and Benefits of Biodiesel and Ethanol Biofuels. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 11206−11210. (7) Shigematsu, A.; Yamada, T.; Kitagawa, H. Selective Separation of Water, Methanol, and Ethanol by a Porous Coordination Polymer Built with a Flexible Tetrahedral Ligand. J. Am. Chem. Soc. 2012, 13145−13147.

4. CONCLUSIONS The production of bioethanol could be significantly improved with an efficient purification step with molecular sieves based in MOFs able to discriminate between ethanol and water. In Zn2(BDC)2(TED), the discrimination is due to the ability of ethanol to interact, simultaneously, via hydrogen bond with the Zn2(COO)4 PW and also by van der Waals forces with the aromatic ring. These conclusions could be achieved only using sufficiently large cluster models or the periodic structure. E



Article

Integrated Experimental and Simulation Study. J. Phys. Chem. C 2010, 114, 6602−6609. (30) Sillar, K.; Hofmann, A.; Sauer, J. Ab Initio Study of Hydrogen Adsorption in MOF-5. J. Am. Chem. Soc. 2009, 131, 4143−4150. (31) Bordiga, S.; Vitillo, J. G.; Ricchiardi, G.; Regli, L.; Cocina, D.; Zecchina, A.; Arstad, B.; Bjørgen, M.; Hafizovic, J.; Lillerud, K. P. Interaction of Hydrogen with MOF-5. J. Phys. Chem. B 2005, 109, 18237−18242. (32) Sagara, T.; Klassen, J.; Ortony, J.; Ganz, E. Binding Energies of Hydrogen Molecules to Isoreticular Metal-Organic Framework Materials. J. Chem. Phys. 2005, 123, 014701−014705. (33) Sagara, T.; Klassen, J.; Ganz, E. Computational Study of Hydrogen Binding by Metal-Organic Framework-5. J. Chem. Phys. 2004, 121, 12543−12547. (34) Hübner, O.; Glöss, A.; Fichtner, M.; Klopper, W. On the Interaction of Dihydrogen with Aromatic Systems. J. Phys. Chem. A 2004, 3019−3023. (35) Klontzas, E.; Mavrandonakis, A.; Froudakis, G. E.; Carissan, Y.; Klopper, W. Molecular Hydrogen Interaction with IRMOF-1: A Multiscale Theoretical Study. J. Phys. Chem. C 2007, 111, 13635− 13640. (36) Kuc, A.; Heine, T.; Seifert, G.; Duarte, H. A. H2 Adsorption in Metal-Organic Frameworks: Dispersion or Electrostatic Interactions? Chem.Eur. J. 2008, 14, 6597−6600. (37) Kuc, A.; Heine, T.; Seifert, G.; Duarte, H. A. On the Nature of the Interaction Between H2 and Metal-Organic Frameworks. Theor. Chem. Acc. 2008, 120, 543−550. (38) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A Consistent and Accurate Ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104−154123. (39) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (40) Becke, A. D. Density-Functional Exchange-Energy Approximation with Correct Asymptotic Behavior. Phys. Rev. A 1988, 38, 3098−3100. (41) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti Correlation-Energy Formula into a Functional of the Electron Density. Phys. Rev. B 1988, 37, 785−789. (42) Becke, A. D. Density-Functional Thermochemistry. III. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648−5652. (43) Ahlrichs, R.; Bär, M.; Häser, M.; Horn, H.; Kölmel, C. Electronic Structure Calculations on Workstation Computers: The Program System Turbomole. Chem. Phys. Lett. 1989, 162, 165−169. (44) Boys, S. F.; Bernardi, F. The calculation of Small Molecular Interactions by the Differences of Separate Total Energies. Some Procedures with Reduced Errors. Mol. Phys. 1970, 19, 553−566. (45) Grimme, S. Semiempirical GGA-Type Density Functional Constructed with a Long-Range Dispersion Correction. J. Comput. Chem. 2006, 27, 1787−1799. (46) Kresse, G. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169−11186. (47) Dybtsev, D. N.; Chun, H.; Kim, K. Rigid and Flexible: a Highly Porous Metal-Organic Framework with Unusual Guest-Dependent Dynamic Behavior. Angew. Chem., Int. Ed. 2004, 43, 5033−5036. (48) Kresse, G. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758−1775. (49) Monkhorst, H. J.; Pack, J. D. Special Points for Brillouin-Zone Integrations. Phys. Rev. B 1976, 13, 5188−5192. (50) McQuarrie, D.; Simon, J. Molecular Thermodynamics; University Science Books: Sausalito, CA, 1999. (51) Grimme, S. Accurate Description of van der Waals Complexes by Density Functional Theory Including Empirical Corrections. J. Comput. Chem. 2004, 25, 1463−1473. (52) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Reticular Synthesis and the Design of New Materials. Nature 2003, 423, 705−714.

(8) Nalaparaju, A.; Zhao, X. S.; Jiang, J. W. Biofuel Purification by Pervaporation and Vapor Permeation in Metal−Organic Frameworks: a Computational Study. Energy Environ. Sci. 2011, 4, 2107−2116. (9) He, Y.; Bagley, D. M.; Leung, K. T.; Liss, S. N.; Liao, B.-Q. Recent Advances in Membrane Technologies for Biorefining and Bioenergy Production. Biotechnol. Adv. 2012, 30, 858−817. (10) Lipnizki, F. Membrane Process Opportunities and Challenges in the Bioethanol Industry. Desalination 2010, 250, 1067−1069. (11) Cui, Y.; Kita, H.; Okamoto, K.-I. Zeolite T Membrane: Preparation, Characterization, Pervaporation of Water/Organic Liquid Mixtures and Acid Stability. J. Membr. Sci. 2004, 236, 17−27. (12) Shah, D.; Kissick, K.; Ghorpade, A.; Hannah, R.; Bhattacharyya, D. Pervaporation of Alcohol−Water and Dimethylformamide−Water Mixtures Using Hydrophilic Zeolite NaA Membranes: Mechanisms and Experimental Results. J. Membr. Sci. 2000, 179, 185−205. (13) Frolkova, A. K.; Raeva, V. M. Bioethanol Dehydration: State of the Art. Theor. Found. Chem. Eng. 2010, 44, 545−556. (14) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; O’Keeffe, M.; Yaghi, O. M. Modular Chemistry: Secondary Building Units as a Basis for the Design of Highly Porous and Robust Metal− Organic Carboxylate Frameworks. Acc. Chem. Res. 2001, 34, 319−330. (15) Murray, L. J.; Dincă, M.; Long, J. R. Hydrogen Storage in MetalOrganic Frameworks. Chem. Soc. Rev. 2009, 38, 1294−1314. (16) Rowsell, J. L. C.; Yaghi, O. M. Strategies for Hydrogen Storage in Metal-Organic Frameworks. Angew. Chem., Int. Ed. 2005, 44, 4670− 4679. (17) Suh, M. P.; Park, H. J.; Prasad, T. K.; Lim, D.-W. Hydrogen Storage in Metal-Organic Frameworks. Chem. Rev. 2012, 112, 782− 835. (18) Furukawa, H.; Ko, N.; Go, Y. B.; Aratani, N.; Choi, S. B.; Choi, E.; Yazaydin, A. O.; Snurr, R. Q.; O’Keeffe, M.; Kim, J.; Yaghi, O. M. Ultrahigh Porosity in Metal-Organic Frameworks. Science 2010, 329, 424−428. (19) Farha, O. K.; Yazaydın, A. Ö .; Eryazici, I.; Malliakas, C. D.; Hauser, B. G.; Kanatzidis, M. G.; Nguyen, S. T.; Snurr, R. Q.; Hupp, J. T. De Novo Synthesis of a Metal-Organic Framework Material Featuring Ultrahigh Surface Area and Gas Storage Capacities. Nat. Chem 2010, 2, 944−948. (20) Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Hydrogen Storage in Microporous MetalOrganic Frameworks. Science 2003, 300, 1127−1129. (21) Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T.-H.; Long, J. R. Carbon Dioxide Capture in Metal-Organic Frameworks. Chem. Rev. 2012, 112, 724− 781. (22) Kreno, L. E.; Leong, K.; Farha, O. K.; Allendorf, M.; Van Duyne, R. P.; Hupp, J. T. Metal-Organic Framework Materials as Chemical Sensors. Chem. Rev. 2012, 112, 1105−1125. (23) Horcajada, P.; Gref, R.; Baati, T.; Allan, P. K.; Maurin, G.; Couvreur, P.; Férey, G.; Morris, R. E.; Serre, C. Metal-Organic Frameworks in Biomedicine. Chem. Rev. 2012, 112, 1232−1268. (24) Yoon, M.; Srirambalaji, R.; Kim, K. Homochiral Metal-Organic Frameworks for Asymmetric Heterogeneous Catalysis. Chem. Rev. 2012, 112, 1196−1231. (25) Li, J.-R.; Sculley, J.; Zhou, H.-C. Metal-Organic Frameworks for Separations. Chem. Rev. 2012, 112, 869−932. (26) Peralta, D.; Chaplais, G.; Simon-Masseron, A.; Barthelet, K.; Chizallet, C.; Quoineaud, A.-A.; Pirngruber, G. D. Comparison of the Behavior Metal-Organic Frameworks and Zeolites for Hydrocarbon Separations. J. Am. Chem. Soc. 2012, 134, 8115−8126. (27) Li, J.-R.; Kuppler, R. J.; Zhou, H.-C. Selective Gas Adsorption and Separation in Metal-Organic Frameworks. Chem. Soc. Rev. 2009, 38, 1477−1504. (28) Lee, J. Y.; Olson, D. H.; Pan, L.; Emge, T. J.; Li, J. Microporous Metal−Organic Frameworks with High Gas Sorption and Separation Capacity. Adv. Funct. Mater. 2007, 17, 1255−1262. (29) Chen, Y. F.; Lee, J. Y.; Babarao, R.; Li, J.; Jiang, J. W. A Highly Hydrophobic Metal−Organic Framework Zn(BDC)(TED)0.5 for Adsorption and Separation of CH3OH/H2O and CO2/CH4: An F



Article

(53) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe, M.; Yaghi, O. M. Systematic Design of Pore Size and Functionality in Isoreticular MOFs and their Application in Methane Storage. Science 2002, 295, 469−472. (54) Bourrelly, S.; Moulin, B.; Rivera, A.; Maurin, G.; DevautourVinot, S.; Serre, C.; Devic, T.; Horcajada, P.; Vimont, A.; Clet, G.; Daturi, M.; Lavalley, J.-C.; Loera-Serna, S.; Denoyel, R.; Llewellyn, P. L.; Férey, G. Explanation of the Adsorption of Polar Vapors in the Highly Flexible Metal Organic Framework MIL-53(Cr). J. Am. Chem. Soc. 2010, 132, 9488−9498. (55) Heine, T.; Zhechkov, L.; Seifert, G. Hydrogen Storage by Physisorption on Nanostructured Graphite Platelets. Phys. Chem. Chem. Phys. 2004, 6, 980−984. (56) 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.

G


Mechanism of AlcoholâWater Separation in MetalâOrganic Frameworks

Recommend Documents

Mechanism of AlcoholâWater Separation in MetalâOrganic Frameworks