Phenol from

Article pubs.acs.org/Langmuir

Highly Selective Adsorption and Separation of Aniline/Phenol from Aqueous Solutions by Microporous MIL-53(Al): A Combined Experimental and Computational Study Yuanlong Xiao,† Tongtong Han,† Gang Xiao,‡ Yunpan Ying,† Hongliang Huang,† Qingyuan Yang,*,† Dahuan Liu,† and Chongli Zhong*,† †

State Key Laboratory of Organic−Inorganic Composites, Beijing University of Chemical Technology, Chaoyang, Beijing 100029, China ‡ PetroChina Jilin Petrochemical Company, Jiefang Bei, Jilin 132022, China S Supporting Information *

ABSTRACT: Experimental measurements have been combined with molecular simulations to investigate the adsorption and separation of aniline/phenol mixtures from aqueous solutions by the aluminum terephthalate MIL-53. The results show that the framework flexibility of this material plays a crucial role in the adsorption process and thus can greatly enhance the separation of the aniline/phenol mixture from their solutions. Compared with the conventional adsorbents, MIL-53(Al) shows the best performance for such systems of interest, from the points of view of both the adsorption capacities and the selectivities for aniline. The findings obtained in this work may facilitate more investigations in connection with the application of flexible nanoporous materials for the separation of organic compounds from liquid-phase environments.

1. INTRODUCTION In recent years, efficient treatment of wastewater containing organic compounds has become a serious environmental concern. Among these pollutants, aniline (An) and phenol (Ph) are potential carcinogens and have been listed as the top priority contaminants by most national Environmental Protection Agencies.1,2 The two aromatic compounds can be simultaneously detected in the effluents of industrial processes, for example, ammonolysis of phenol to manufacture aromatic amine.1 Therefore, their removal from wastewater is of great significance. On the other hand, aniline and phenol are also two important chemicals that can have many distinctively different applications in the industrial fields. For instance, aniline has been widely used for the preparation of diphenylmethane diisocyanate, which is heavily employed in the manufacture of polyurethanes,3 whereas one of the major uses of phenol is the condensation with formaldehyde to produce phenolic resins, in which the most famous one is Bakelite.4 This leads to the necessity of understanding the separation behavior of aniline over phenol from wastewater, which also will help to improve the design of treatment processes. Among the available techniques for removing and separating these organic chemicals from waste streams, it is generally recognized that adsorption on the basis of porous adsorbents is an effective method.5,6 Up to now, conventional adsorbents, such as polymeric resins5 and graphite,6 and carbonaceous materials7 have been investigated toward this end. However, they bear some drawbacks including limited working capacity and/or selectivity. Metal-organic frameworks (MOFs) represent a relatively novel family of hybrid nanoporous materials, constructed by © XXXX American Chemical Society

bridging metal-containing nodes with organic ligands through coordination bonds.8−10 More recently, MOFs have shown potential versatilities in liquid-phase applications such as adsorption,11−19 separation,20−25 and catalysis.26,27 Among these materials, the MIL-53 family has received intensive attention due to the distinct framework flexibilities and exceptional stabilities under various chemical environments including water.18−20 The latter features may be attributed to the hard or soft character of the constituents in the frameworks,28 which are very crucial for the practical utility of adsorbents under industrial conditions.17,29−31 Such types of MIL-53 materials consist of hard trivalent cations (Al3+, Cr3+, and Fe3+) and hard terephthalate ligands, resulting in structures with a 1D lozenge-shaped channel.32,33 According to the hard− soft acid−base theory of Pearson,34 the robust coordination bonds can be formed between the metal nodes and ligands, making the MIL-53 series less water-susceptible than most of the MOFs, like Cu-BTC and IRMOFs.28 In contrast to those MOFs with rigid bodies, the frameworks of MIL-53 materials can be differently responsive to guest molecules, depending on their polar nature.35 To the best of our knowledge, there are no studies on the adsorption behavior of aniline/phenol mixtures from aqueous solutions using MOFs up to date. Therefore, this topic was for the first time investigated in this work by combining experimental measurements and molecular simulations with MIL-53(Al) as the nanoporous material. The Received: March 11, 2014 Revised: September 22, 2014

A

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Figure 1. Effect of contact time on the adsorption of aniline (a) and phenol (b) on MIL-53(Al) at 298 K for different initial concentrations.

current study shows that such a flexible material can exhibit promising application for separating aniline/phenol from their mixed aqueous solutions. The knowledge obtained may also stimulate more efforts toward the applications of flexible MOFs for recovering similar organic compounds from industrial effluents.

the revised Widom’s test particle method.46 NVT Monte Carlo simulations were also run at the full loadings to calculate the radial distribution functions (RDFs) between the guest molecules and the framework atoms of MIL-53(Al). More simulation details can be found in the Supporting Information.

3. RESULTS AND DISCUSSION 3.1. Adsorption of Single-Compound Solution. Prior to adsorption measurements, we first compared the XRD patterns measured on the hydrated and dehydrated materials with those calculated for the two forms of MIL-53(Al), as shown in Figure S2 in the Supporting Information. Obviously, the starting hydrated material is in the NP structure, and the XRD pattern of MIL-53(Al)dehydra also matches well the one calculated for the LP structure. Furthermore, nitrogen adsorption measurements at 77 K (Supporting Information, Figure S3) give a BET surface area of 1344 m2 g−1, which is close to the theoretical accessible surface area of 1408 m2 g−1.37 Such a validation step allows us to confidently carry out the further explorations. To probe the adsorption behaviors of aniline and phenol in MIL-53(Al), we first performed kinetic measurements on the single-compound adsorption from their respective solutions in the initially hydrated material MIL-53(Al)hydra. From the results shown in Figure 1a for the two initial concentrations, the adsorption process of aniline proceeds very rapidly (with the NP form being reopened to the LP structure under an initial concentration of 3000 ppm, see below), and the amount adsorbed almost reaches the equilibrium even in the first minute. Hence, the interactions between the framework and the preadsorbed water molecules are not strong enough to inhibit the adsorption of aniline from the solutions, which may be to some extent reflected from the simulated adsorption enthalpy of pure aniline at the limit of zero coverage in the LP structure (−64.7 kJ mol−1) and that of water in the NP structure (−34.0 kJ mol−1). In regard to phenol, it exhibits much lower capacities than those of aniline under the same conditions of initial concentrations, as shown in Figure 1b. Especially, there is a negligible uptake for phenol at the initial concentration of 500 ppm in the solution. To understand these differences, we further performed the XRD measurements for the samples after adsorption, as shown in Figure S4 in the Supporting Information, together with those calculated for the NP and LP structures for comparison. Obviously, when the adsorbent is in contact with the 3000 ppm solution of aniline or phenol, the initial NP structure transforms into the LP form. In contrast, both the NP and LP phases coexist in the loaded sample when in contact with the 500 ppm solution of aniline, whereas only the NP phase exists for the case of phenol. In addition, our calculations show that the adsorption enthalpy of pure phenol (−65.7 kJ mol−1) at the limit of zero coverage in the LP

2. EXPERIMENTS AND COMPUTATIONS 2.1. Material Synthesis. MIL-53(Al) was synthesized and activated according to the literature protocol with a slight modification.33,36 Briefly, a mixture of Al(NO3)3·9H2O, terephthalic acid (H2BDC), and deionized water was heated at 493 K for 3 days. The resulting white powder was filtered off, washed with deionized water, and dried at 373 K. Then, the sample was treated by an alternative activation method at the elevated temperature to remove the excess of unreacted H2BDC molecules in the channels. The MIL53(Al) solid was calcined in air at 423 K for an overnight period to ensure complete removal of the solvent molecules. Part of the sample was cooled down in air and rehydrated into the narrow-pore (NP) form33 (designated as MIL-53(Al)hydra), while the other part was cooled down under vacuum so as to maintain the initial structure in the large-pore (LP) form (designated as MIL-53(Al)dehydra). More details about synthesis and characterization (X-ray diffraction (XRD) and Brunauer−Emmett−Teller (BET)) are given in the Supporting Information. 2.2. Adsorption Experiments. Liquid-phase batch adsorption experiments were performed at 298 K, similar to our previous procedure.37,38 For each measurement, a 10 mL glass vial with 0.05 g of adsorbents was filled with single-compound solutions of aniline or phenol or their mixed solutions and they were stirred magnetically. The preadsorption (C0) and postadsorption concentrations (Ce) in the solutions were determined spectrophotometrically, from which the amount of aniline or phenol adsorbed in the adsorbents was calculated from their difference. More experimental details can be found in the Supporting Information. For convenience, the aniline/phenol mixtures with the initial concentration ratios of 25:75, 50:50, and 75:25 are denoted as [An]0/[Ph]0 = 25:75, [An]0/[Ph]0 = 50:50, and [An]0/ [Ph]0 = 75:25, respectively. 2.3. Computational Details. The configurational-bias Monte Carlo (CBMC) simulations in the grand canonical ensemble39−43 were performed to investigate the adsorption of single-compound solutions of aniline and phenol and their mixed solutions on MIL-53(Al) at 298 K, using our in-house simulation code CADSS (Complex Adsorption and Diffusion Simulation Suite). The adsorbate−adsorbate and adsorbate−MOF interactions were both described by a combination of site−site Lennard−Jones (LJ) and Coulombic potentials.44,45 An all-atom rigid model was used to describe aniline and phenol molecules as well as the large and narrow pore structures of the adsorbent. Details of the force fields used for the adsorbates and the adsorbent are given in the Supporting Information. All the LJ crossinteraction parameters were determined by the Lorentz−Berthelot mixing rules. For the calculation of the adsorption enthalpies of pure aniline, phenol, and water at the limit of zero coverage, CBMC simulations in the canonical (NVT) ensemble were performed using B

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outperforms many conventional adsorbents including activated carbons and zeolites (Table S1 in the Supporting Information). For the case of phenol, the threshold shifts to 500 ppm, and the full opening of the structure requires a higher concentration, indicating that the flexibility of the framework can have a significant effect on the adsorption process. To rationalize the similar results observed for the adsorption of N/S-containing heterocyclic organic molecules in MIL-53(Fe), Van de Voorde et al. suggested that the guest/host H-bond acceptor abilities are responsive for such different structural transitions.13 Figure 2 also shows that the adsorption uptakes of aniline are larger than those of phenol within the whole range of concentrations examined. Thus, besides framework flexibility, the influence of water molecules adsorbed in the channels should also be taken into account. The presence of coadsorbed water molecules can reduce the uptakes of both aniline and phenol. However, due to the stronger H-bond interactions of phenol with water than that of aniline,47 our simulations indicate that more water molecules can also be trapped in the cavities of MIL-53(Al) accompanied with the adsorption of phenol (0.64 and 0.11 H2O molecules per unit cell for the cases of phenol and aniline, respectively), as can be reflected from the typical snapshots shown in Figure 3. Consequently, the above observations may be attributed to the reason that aniline probably has a larger interaction with the material in the presence of water as compared to phenol. Because the host structure undergoes a remarkable transformation, the so-called phase mixture model48−50 was adopted in this work to understand the adsorption behaviors of aniline and phenol in MIL-53(Al). We began with grand canonical Monte Carlo (GCMC) simulations for obtaining the adsorption isotherms of aniline and phenol from their respective solutions in both the rigid NP and LP structures. Then, the composite isotherm for each solution was constructed by following the simulated curve in the NP form up to the equilibrium transition concentration observed experimentally (as shown in Figure 2, 50 ppm for aniline and

structure is similar to that of aniline under the same conditions, demonstrating comparative adsorption affinity of this host structure toward both guest molecules. Therefore, although the final structures of MIL-53(Al) are both in the LP form when the adsorption experiments were performed at 3000 ppm for aniline and phenol from their respective solutions, the much larger adsorption capacity of the former relative to the latter (see Figure 1) indicates that other factors than merely the guest−framework interactions should play important roles during the adsorption process. Figure 2 compares the adsorption amounts of aniline and phenol as a function of the equilibrium concentrations in their

Figure 2. Single-compound adsorption isotherms of aniline and phenol in MIL-53(Al)hydra at 298 K, as a function of their equilibrium concentrations in the respective solutions. The curved lines are used for guiding the eyes.

respective solutions on MIL-53(Al)hydra, where a semilogarithmic scale is used to highlight the steps in the isotherms. For each compound, there is a certain threshold of concentration before substantial uptake occurs. For aniline solutions, the pore of MIL-53(Al)hydra starts to reopen at the concentration of 50 ppm and subsequently transforms into the fully expanded structure with a high adsorption capacity of 445 mg g−1, which

Figure 3. Two views of the LP structure of MIL-53(Al) with the adsorbed aniline (a, b) or phenol (c, d) and water molecules. The framework of MIL-53 is shown in line style (Al, pink; O, red; C, gray; H, white). To highlight the positions of guests, water and aniline/phenol are represented by yellow ball and green stick model, respectively. C

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Figure 4. RDFs of (a) N atom in aniline (denoted as N1An) and O atom in phenol (O1Ph) with the H atoms (H2MOF) in the μ2-OH groups of the MIL-53(Al) framework and (b) C atom linked by the −NH2 group in aniline (C2An) and by the −OH group in phenol (C2Ph) with the C atoms (C2MOF) linked by the carbonyl group in the BDC linkers at the full loadings.

500 ppm for phenol, respectively), and then switching to the one in the LP form. Such a method has also been used to study adsorption of aromatic hydrocarbons in the silicalite48 and the breathing effect of MIL-53(Al) upon CO2 adsorption.49 As shown in Figure 2, the so-constructed composite isotherms can fairly reproduce the experimental ones; this allows us to explore the microscopic adsorption mechanisms. Because of the steric constraints, the NP structure of MIL-53(Al) cannot accommodate aniline or phenol molecules. In the LP structure, the two types of guest molecules adsorbed are arranged in a zigzag manner along the channel direction but not fully parallel to the pore wall, while the water molecules locate in the vicinity of the μ2-OH groups of the framework and the functional groups of guest molecules (Figure 3). The RDFs for aniline and phenol molecules with the interacting sites on MIL-53(Al) at their respective full loadings are plotted in Figure 4. One can observe that aniline and phenol molecules form strong H-bonds between their respective functional groups (−NH2 or −OH) and the H atoms of μ2-OH groups in the framework with characteristic distances of 1.88 and 1.86 Å, respectively (Figure 4a). The characteristic distances between the benzene-ring centers of guest molecules and the BDC linkers of MIL-53(Al) are both ∼4.81 Å (see Figure 4b), which is indicative of forming the weak π−π interactions.51 This value is comparable to that observed for liquid-phase adsorption of pure aniline in the isotypical material MIL-47(V).52 These observations clearly demonstrate that both species have the identical adsorption sites in MIL-53(Al). Thus, it can be expected that competitive adsorption will occur in the mixtures. 3.2. Adsorption of Aniline/Phenol Mixed Solution. To investigate the adsorption behavior of aniline/phenol mixture from their solution, we performed competitive experiments at various initial concentrations with a molar ratio of [An]0/[Ph]0 = 50:50 in MIL-53(Al)hydra, as shown in Figure 5 (the adsorbed amount as a function of initial concentrations is given in Figure S5 in the Supporting Information). The uptake of aniline increases monotonically with the increase of the equilibrium concentration, whereas the isotherm of phenol shows a maximum. Similar behaviors have also been found for the adsorption of the cymene isomers in this MOF.20 As noted previously, the larger interactions between aniline and the flexible material versus that of phenol in the presence of water could also be used to account for the different shapes of the isotherms as well as the larger adsorption capacities of the former, as shown in Figure 5. For comparison, this figure shows the performance of the initially dehydrated MIL-53(Al)dehydra (LP form) for separating these mixtures. It can be observed that, when the adsorption of the two components takes place

Figure 5. Partial adsorption isotherms of aniline and phenol from their mixtures of aqueous solutions in MIL-53(Al)hydra (solid symbols) and MIL-53(Al)dehydra (empty symbols): adsorption amount (mg g−1) vs equilibrium concentration (ppm). The curved lines are used for guiding the eyes.

from aqueous solutions, the MIL-53(Al)dehydra has very similar uptakes to the initially hydrated counterpart. This can be attributed to the fact that the dehydrated sample can quickly adsorb some traces of water to form again the NP form.32 The experimental results measured on MIL-53(Al)hydra at two other initial molar ratios ([An]0/[Ph]0 = 25:75 and 75:25) are given in Figure S6 (see the Supporting Information), showing similar trends to those in Figure 5. The corresponding total adsorption isotherms of aniline/ phenol mixtures at the above three initial ratios are shown in Figure S7 (see the Supporting Information) to characterize the overall performance of the adsorbent. It can be found that the total adsorption capacities can become higher than those of the individual ones at high equilibrium concentrations. Such results have also been observed by Zhang et al.,1 which was attributed to the fact that aniline and phenol molecules can partially form aniline+−phenol− complex in the aqueous phase via Lewis acid−base interactions. This complex is electroneutral as a whole, and the positive/negative notations indicate that there is partial electron transfer from aniline to phenol. The hydrophobic nature of such a complex may be in favor of enhancing the guest/host affinities.1 Thus, both the synergistic and competitive effects exist during the adsorption of aqueous solution of aniline and phenol mixtures. Furthermore, Figure S7 in the Supporting Information indicates that the threshold of the total equilibrium concentration for reopening the NP pore structure of MIL-53(Al) depends on the initial [An]0/[Ph]0 molar ratio in the mixture; that is, the higher the initial content of aniline, the lower the total equilibrium concentration will be for the NP to LP transformation. D

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keep a value of ∼7 up to 1000 ppm for the equilibrium concentration of aniline in the solutions, while the separation will be not possible at even higher concentrations due to very low selectivities. Taking the system with the molar ratio of [An]0/[Ph]0 = 50:50 as an example, Figure 6 also shows the selectivities obtained from molecular simulations on the basis of the rigid LP structure of MIL-53(Al). Compared to the experimental results, the simulated selectivities change slightly within the whole range of concentrations examined and exhibit much lower values under the same adsorption conditions. This can be attributed to the absence of the structural evolution of the material in the simulations, the occurrence of which can provide a more suitable environment to enhance the interactions of aniline with the adsorbent than that of phenol. Similar observations have also been found in the experimental study of Alaerts et al.20 where MIL-53(Al) shows better performance than its rigid isotypical material MIL-47(V) for the separation of ortho-substituted alkylaromatics. Figure S11 in the Supporting Information presents the snapshots for the aniline/phenol mixture adsorbed in the rigid LP structure, showing that both types of molecules stack in a zigzag manner along the channel, similar to those observed for the singlecompound solutions shown in Figure 3. These comparisons highlight the importance of the framework flexibility of MIL53(Al), which can induce distinctively different responsive behaviors of the adsorbent upon the adsorption of guest species that have dissimilar interactions with the host material. Because the structural evolution of MIL-53(Al) is more positively responsive to the adsorption of aniline than phenol (see Figure 2), the resulting environment in the host material can facilitate the more favorable adsorption of aniline, thus greatly enhancing the separation of aniline over phenol from their mixed solutions. Compared with those reported for the traditional adsorbents, the uptake of aniline in MIL-53(Al) is significantly higher under similar conditions, as can be seen from Table 1.

Generally, the competitive adsorption of aniline over phenol from solution can be characterized by the adsorption selectivity, as given by20 ⎛q ⎞ ⎛C ⎞ αAn/Ph = ⎜⎜ An ⎟⎟ × ⎜ Ph ⎟ ⎝ qPh ⎠ ⎝ CAn ⎠

(1)

where qi and Ci (i = An or Ph) are the equilibrium amounts of component i in the adsorbed and bulk-liquid phases, respectively. Figures 6 and S8 in the Supporting Information

Figure 6. Adsorption selectivity of aniline over phenol measured experimentally in MIL-53(Al)hydra, as a function of the equilibrium concentration of aniline in the bulk solution. The simulation results for the rigid LP structure are also shown for comparison.

show the results on the basis of the data obtained from the competitive experiments, as a function of the equilibrium concentration of aniline in the external solution. One can observe that MIL-53(Al) is more preferentially selective adsorption of aniline over phenol for all the mixtures, and the selectivity depends on both the concentrations and molar ratios of the two compounds in the aqueous solutions. The changing trends of the selectivity show similar behaviors for the mixture solutions at the three initial molar ratios examined; they exhibit a sharp decrease at low concentrations, an increase with further increasing concentration, and a decrease at high concentrations. Within the range of low concentrations, it is difficult to largely expand the initial NP structure of MIL53(Al) due to the weak forces exerted by the molecules in the solutions. In this situation, the experimental data show that, with increasing the concentration in the external solution, the ratios of the equilibrium amounts of aniline to that of phenol decrease in both the adsorbed and bulk phases, but the decreasing magnitude is much larger in the former phase, leading to the first sharp decreasing trend in the selectivity. With further increasing the concentration, the pores in the sample are gradually reopened but not all are in the fully expanded forms (as can be reflected from Supporting Information, Figure S7). Such intermediate structures can facilitate the adsorption of aniline so as to favor their expansion, which results in the second increasing trend. At high concentrations, because the pores can be more easily transformed into the LP form by both aniline and phenol molecules (see Figure 1), the preferentially enhanced interactions for aniline are offset greatly, and the strength of adsorbate/adsorbent interactions will be trailed off when most strong adsorption sites are occupied.14 As a consequence, a decreasing trend can be expected for selectivity in this region. In addition, Figures 6 and S8 in the Supporting Information indicate that the selectivities of aniline over phenol still can

Table 1. Comparison of the Selectivity of Aniline over Phenol and the Uptakes of Aniline (mg g−1) on Various Adsorbents in the Mixture with Initial Molar Ratio of 50:50 materials

αAn/Ph

uptake of aniline

refs

NDA-16 NDA-1800 MN200 HSAGox activated carbon MIL-53(Al)

1.1 1.3 1.4 10.8 1.0a 9.4

52 55 67 26 20 280

2 2 5 6 7 this work

a

The highest equilibrium concentration of aniline is 55 ppm; for other cases, the equilibrium concentration of aniline is ∼150 ppm.

The performance of this MOF can also be regarded as one of the best in terms of the selectivity. Given that ideal adsorbents should require both high working capacity and selectivity, flexible MIL-53(Al) can be considered as a promising candidate for efficiently separating aniline and phenol from the industrial effluents.

4. CONCLUSIONS In this work, the adsorption behaviors of aniline, phenol, and their mixtures from the respective aqueous solutions were investigated in MIL-53(Al) by a combination of experiments and molecular simulations. The results show that the E

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framework flexibility of the MOF plays a crucial role in the adsorption process and can greatly enhance the separation of the aniline/phenol mixtures from solutions. Compared with traditional adsorbents, this material shows excellent performance, exhibiting both high adsorption capacity and selectivity for aniline over phenol from their mixed solutions. However, the mechanism of reopening the initial NP structure remains not very clear, which may be either pushed to open by guest molecules gradually entering the pores or pulled to open from the material’s external surfaces through a layer-by-layer shear; it may also result from their cooperative effects. Currently, more efforts are being devoted to make this clear.

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(9) Li, J.-R.; Sculley, J.; Zhou, H.-C. Metal-Organic Frameworks for Separations. Chem. Rev. 2012, 112, 869−932. (10) Bew, S. P.; Burrows, A. D.; Düren, T.; Mahon, M. F.; Moghadam, P. Z.; Sebestyen, V. M.; Thurston, S. Calix[4]arene-Based Metal-Organic Frameworks: Towards Hierarchically Porous Materials. Chem. Commun. 2012, 48, 4824−4826. (11) Khan, N. A.; Hasan, Z.; Jhung, S. H. Ionic Liquids Supported on Metal-Organic Frameworks: Remarkable Adsorbents for Adsorptive Desulfurization. Chem.Eur. J. 2014, 20, 376−380. (12) Ahmed, I.; Hasan, Z.; Khan, N. A.; Jhung, S. H. Adsorptive Denitrogenation of Model Fuels with Porous Metal-Organic Frameworks (MOFs): Effect of Acidity and Basicity of MOFs. Appl. Catal., B 2013, 129, 123−129. (13) Van de Voorde, B.; Munn, A. S.; Guillou, N.; Millange, F.; De Vos, D. E.; Walton, R. I. Adsorption of N/S Heterocycles in the Flexible Metal−Organic Framework MIL-53(FeIII) Studied by In Situ Energy Dispersive X-ray Diffraction. Phys. Chem. Chem. Phys. 2013, 15, 8606−8615. (14) Nalaparaju, A.; Jiang, J. W. Recovery of Dimethyl Sulfoxide from Aqueous Solutions by Highly Selective Adsorption in Hydrophobic Metal−Organic Frameworks. Langmuir 2012, 28, 15305−15312. (15) Khan, N. A.; Jhung, S. H. Remarkable Adsorption Capacity of CuCl2-Loaded Porous Vanadium Benzenedicarboxylate for Benzothiophene. Angew. Chem., Int. Ed. 2012, 51, 1198−1201. (16) Haque, E.; Jun, J.; Jhung, S. H. Adsorptive Removal of Methyl Orange and Methylene Blue from Aqueous Solution with a MetalOrganic Framework Material, Iron Terephthalate (MOF-235). J. Hazard. Mater. 2011, 185, 507−511. (17) Cychosz, K. A.; Matzger, A. J. Water Stability of Microporous Coordination Polymers and the Adsorption of Pharmaceuticals from Water. Langmuir 2010, 26, 17198−17202. (18) Patil, D. V.; Rallapalli, P. B. S.; Dangi, G. P.; Tayade, R. J.; Somani, R. S.; Baja, H. C. MIL-53(Al): An Efficient Adsorbent for the Removal of Nitrobenzene from Aqueous Solutions. Ind. Eng. Chem. Res. 2011, 50, 10516−10524. (19) Maes, M.; Schouteden, S.; Alaerts, L.; Depla, D.; De Vos, D. E. Extracting Organic Contaminants from Water Using the Metal− Organic Framework CrIII(OH){O2C−C6H4−CO2}. Phys. Chem. Chem. Phys. 2011, 13, 5587−5589. (20) Alaerts, L.; Maes, M.; Giebeler, L.; Jacobs, P. A.; Martens, J. A.; Denayer, J. F.; Kirschhock, C. E. A.; De Vos, D. E. Selective Adsorption and Separation of ortho-Substituted Alkylaromatics with the Microporous Aluminum Terephthalate MIL-53. J. Am. Chem. Soc. 2008, 130, 14170−14178. (21) Cychosz, K. A.; Ahmad, R.; Matzger, A. J. Liquid Phase Separations by Crystalline Microporous Coordination Polymers. Chem. Sci. 2010, 1, 293−302. (22) Moghadam, P. Z.; Düren, T. Origin of Enantioselectivity in a Chiral Metal−Organic Framework: A Molecular Simulation Study. J. Phys. Chem. C 2012, 116, 20874−20881. (23) Hu, Z.; Chen, Y.; Jiang, J. W. Liquid Chromatographic Separation in Metal−Organic Framework MIL-101: A Molecular Simulation Study. Langmuir 2013, 29, 1650−1656. (24) Gutiérrez-Sevillano, J. J.; Dubbeldam, D.; Bellarosa, L.; López, N.; Liu, X.; Vlugt, T. J. H.; Calero, S. Strategies to Simultaneously Enhance the Hydrostability and the Alcohol−Water Separation Behavior of Cu-BTC. J. Phys. Chem. C 2013, 117, 20706−20714. (25) Van de Voorde, B.; Bueken, B.; Denayer, J.; De Vos, D. E. Adsorptive Separation on Metal−Organic Frameworks in the Liquid Phase. Chem. Soc. Rev. 2014, 43, 5766−5788. (26) Alkordi, M. H.; Liu, Y.; Larsen, R. W.; Eubank, J. F.; Eddaoudi, M. Zeolite-like Metal Organic Frameworks as Platforms for Applications: On Metalloporphyrin-Based Catalysts. J. Am. Chem. Soc. 2008, 130, 12639−12641. (27) Lalonde, M. B.; Farha, O. K.; Scheidt, K. A.; Hupp, J.T. NHeterocyclic Carbene-Like Catalysis by a Metal-Organic Framework (MOF) Material. ACS Catal. 2012, 2, 1550−1554. (28) Shah, M.; McCarthy, M. C.; Sachdeva, S.; Lee, A. K.; Jeong, H.K. Current Status of Metal-Organic Framework Membranes for Gas

ASSOCIATED CONTENT

S Supporting Information *

Experimental details, characterization results of XRD and N2 physisorption measurements, comparison with other adsorbents, partial isotherms and adsorption selectivity of aniline and phenol, and computational sections. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

* E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the Natural Science Foundation of China (Nos. 21136001, 21121064, and 21322603), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Contract 20110010130001), and the National Key Basic Research Program of China (“973”) (2013CB733503).

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