Adsorption of Pyridine over Amino-Functionalized Metal–Organic

Article pubs.acs.org/JPCC

Adsorption of Pyridine over Amino-Functionalized Metal−Organic Frameworks: Attraction via Hydrogen Bonding versus Base−Base Repulsion Zubair Hasan,† Minman Tong,‡ Beom K. Jung,† Imteaz Ahmed,† Chongli Zhong,*,‡ and Sung Hwa Jhung*,† †

Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 702-701, Republic of Korea ‡ State Key Laboratory of Organic−Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China S Supporting Information *

ABSTRACT: Pyridine (Py) was adsorbed over metal−organic frameworks (MOFs) (UiO-66 and UiO-66-NH2 with different incorporated amino group content) in both vapor and liquid phases to understand the interactions between the basic adsorbate Py and a basic or neutral adsorbent. Py was adsorbed more favorably over UiO-66-NH2 than over the pristine UiO-66. Not only the adsorbed amount of Py but also adsorption kinetics increased with increasing amino group content in UiO-66s, showing that amino groups in the MOFs benefit the adsorption of Py in both vapor and liquid phases. To understand the favorable interaction between Py and basic UiO-66, calculations were also carried out. The results, including calculations, suggested that hydrogen bonding is important for improving the adsorption of Py over UiO-66s. However, the expected repulsive interaction between basic Py and amino groups of UiO-66NH2 was not observed. Therefore, it is vital that specific interaction mechanisms should be considered in order to understand selective adsorption processes. Moreover, the amount of adsorbed Py in the vapor phase increased with increasing adsorption temperature, suggesting that the window size of UiO-66 is very similar to the kinetic diameter or critical dimension of Py and that the window size probably is slightly increased with increasing temperature because of lattice vibrations. tion20,21 processes. However, there has been only one report22 thus far regarding the adsorption of Py on MOFs, despite MOFs having been widely utilized in various adsorptions and separations. In this paper, we report for the first time the adsorption of Py from both vapor and liquid phases with stable and wellcharacterized MOFs to understand the adsorption mechanism and evaluate their potential as adsorbents for the removal of Py. In particular, we investigate how hydrogen bonding and base− base repulsion (between the basic adsorbent and Py) contribute to adsorption. Calculations were also carried out to understand Py adsorption over the MOFs. Among the various MOFs reported to date, we chose porous zirconium-benzenedicarboxylates (Zr-BDCs) called UiO-66 and amino-functionalized UiO-66s for the adsorption of Py (UiO stands for the University of Oslo).23,24

1. INTRODUCTION The development of nanoporous materials has been quite rapid in recent years because of emerging functional materials1−8 such as metal−organic frameworks (MOFs).4,7,8 Porous MOFs have attracted considerable attention because of their high and regular porosity. Therefore, they have many potential applications, including gas adsorption and storage, separation, and adsorption of organic molecules.4,7,8 Pyridine (Py) is a weak basic heterocyclic compound that can be used as a solvent or precursor to produce pharmaceuticals, dyes, or agrochemicals. Recently, compounds containing Py moieties (such as pyridine-2,6-dicarboxylic acid and pyridine2,4,6-tricarboxylic acid) have been of interest because of their ability to coordinate and produce MOFs.9,10 Moreover, MOFs can be modified by grafting with a Lewis base (such as Py and ethylenediamine) having nonbonding electron pairs.11,12 Py has also been widely used as a probe molecule to analyze the acidity of a material (Brønsted and Lewis acid sites) by using mainly Fourier transfrom infrared (FTIR) spectroscopy.13 However, Py is a hazardous material that should be removed from air and water.14 MOFs have also been investigated for the adsorptive removal of hazardous materials,15,16 including adsorptive desulfurization17−19 and adsorptive denitrogena© 2014 American Chemical Society

Received: July 16, 2014 Revised: August 8, 2014 Published: August 21, 2014 21049

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Figure 1. Effect of temperature and amino group content of the UiO-66s on the kinetics of Py adsorptions at 45, 50, and 60 °C.

2. EXPERIMENTAL SECTION 2.1. Materials and Characterization Procedures. All the solvents and reagents used were commercially available and used as received. Zirconium chloride (ZrCl2, 99.5%), benzenedicarboxylic acid (C8H6O4, H2−BDC, 98.0%), and aminobenzenedicarboxylic acid (C8H7NO4, NH2−H2−BDC, 99.0%) were purchased from Sigma-Aldrich. N,N-Dimethylformamide (C3H7NO, 99.0%), pyridine (C5H5N, 99.5%), and toluene (C7H8, 99.5%) were obtained from OCI chemicals. The UiO-66s were prepared by following previously reported methods24 and were named UiO-66, UiO-66-NH2(50), and UiO-66-NH2(100) depending on the ratio of NH2−H2−BDC/ H 2 −BDC used in the synthesis of UiO-66s (BDC, benzenedicarboxylate). The figures of 50 and 100 indicate that the quantity of NH2−H2−BDC in the linker (H2−BDC/ NH2−H2−BDC) was 50 mol % and 100 mol %, respectively. The X-ray diffraction (XRD) patterns of the adsorbents were obtained using an X-ray diffractometer D2 Phaser (Bruker, with Cu Kα radiation). The nitrogen adsorption isotherms of the adsorbents were analyzed using a surface area and porosity analyzer (Micromeritics, Tristar II 3020) after evacuation at 150 °C for 12 h, and the Brunauer−Emmett−Teller (BET) surface area and total pore volume were calculated using the nitrogen adsorption isotherms. The FTIR spectra of UiO-66s were obtained using a Jasco FTIR-4100 (ATR; maximum resolution, 0.9 cm−1). 2.2. Adsorption Procedures. Vapor phase adsorptions of Py were carried out at 45−110 °C using a custom-built volumetric adsorption apparatus25 consisting of a constanttemperature oven, capacitance manometer, and turbo-molecular pump. The MOFs and adsorbates (in a glass ball) were put

in the oven for the entire experiment (excluding pretreatment) to maintain a constant temperature. The calibration of the equipment was carried out using a stainless steel ball with a predetermined volume. The samples (∼100 mg) were dehydrated for 6 h at 250 °C under high vacuum (∼10−6 Torr) and cooled to a constant temperature before adsorption. The Py was purified by the freeze−pump−thaw method. The dead volume of the equipment was measured with helium every time after pretreatment of a sample. The adsorption capacity was calculated by the ideal gas law after adsorption for a sufficient time (>30 min) for each pressure at the constant temperature. The pressure was checked after 30 min of adsorption and continuously rechecked every 5 min until there was no change of pressure greater than 0.2 Torr, and this final pressure was regarded as an equilibrium pressure. The sorption kinetics of Py on dehydrated MOFs (∼50 mg) was studied at a constant temperature by continuously (interval, 1 s) measuring the pressure of Py vapor from a constant pressure (about 90% of the vapor pressure at a temperature) during adsorption for 1 h. Toluene was also adsorbed in a similar manner to check the adsorption kinetics and adsorption capacities. Liquid phase adsorption of Py was carried out in a beaker with magnetic stirring at 25 °C. Prior to adsorption, the adsorbents were dried overnight under vacuum at 150 °C and stored in a desiccator. An exact amount of the adsorbents (5 mg) was added into aqueous solutions (50 mL) of fixed Py concentrations ranging from 50 to 1000 ppm. The aqueous Py solutions containing the adsorbents were mixed by magnetic stirring and maintained at 25 °C for 1−12 h. The adsorption isotherms of Py were obtained from adsorption (for 12 h) of aqueous solution of Py at various concentrations. After 21050

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Figure 2. Py adsorption isotherms over various UiO-66s at temperatures of 60, 80, and 100 °C.

3. RESULTS The XRD patterns and nitrogen adsorption isotherms (Figure S1a,b of the Supporting Information) of the synthesized UiO66s were similar to the results reported in the literature.24 Moreover, FTIR spectra (Figure S1c of the Supporting Information) showed the presence of C−N stretching absorption at 1257 and N−H wagging at 764 cm−1 that ultimately confirm the successful incorporation of amino groups in the UiO-66s prepared with NH2−H2−BDC.32 The textural properties (Table S1 of the Supporting Information) of the adsorbents show that the materials are highly porous and are in agreement with reported values.33 To understand the relative adsorption kinetics and amount of Py adsorption, the amount of adsorbed Py over UiO-66s with adsorption time (up to 60 min) was measured at 45−60 °C, as shown in Figure 1. The amount of adsorbed Py over UiO-66s increased steadily with time up to 60 min at 45 °C. However, the adsorbed amounts nearly reached saturation after 2 min (root of adsorption time, 11.0 s1/2 in Figure 1) at 60 °C. Interestingly, the adsorbed amounts increased with increasing the amount of amino group in the linker of UiO-66s even though a repulsive interaction between the basic amino group and basic Py could be expected. Moreover, the adsorbed amount also increased with adsorption temperature (between 45 and 60 °C), which is difficult to understand for physisorption in vapor phase (usually an exothermic process).25,34 As shown in Figure S2 of the Supporting Information, the relative adsorption kinetics also increased with increasing the basic amino group content in the linker of UiO-66s at temperatures up to at least 50 °C. Figure 2 shows the adsorption isotherms, which were obtained after sufficient time to achieve equilibrium in the adsorption, of Py over UiO-66s within 60−80 °C. Adsorption

adsorption for a predetermined amount of time, the solution was separated from the adsorbents using a syringe filter (PTFE, hydrophobic, 0.5 μm) and the Py concentrations were measured by using high-performance liquid chromatography (Waters e2695; elution with acetonitrile/water = 8/2; flow rate, 1 mL/min; retention time, 2.8 min; λmax, 256 nm). The adsorption data in liquid phase were analyzed to understand kinetics by using a pseudo-second-order nonlinear model.26 Detailed methods can be found in the Supporting Information. 2.3. Calculation of Py Adsorption Energy. Periodic density functional theory (DFT) calculations were performed on Py as well as UiO-66(Zr)-NH2 with and without Py. The initial atomic coordinates of the UiO-66(Zr)-NH2 structure with empty pores were taken from a previous report.27 One Py molecule was introduced to each cage in a simulation box consisting of one primitive cell to determine the adsorption configuration as well as the binding energy. All the calculations were performed using Dmol3 in Materials Studio,28 and the PBE functional29 with the Grimme correction30 and the double numerical plus (DNP) polarization basis set were employed. Previous work has shown that the above methods work well for hydrogen-bonded systems.31 The convergence threshold parameters for the optimization were set as 2.72 × 10−4 eV (energy), 0.054 eV/Å (gradient), and 0.005 Å (displacement). The binding energy was calculated as the energy difference between the products and the reactants in the adsorption process, as defined in eq 1 binding energy = EMOF−adsorbate − EMOF − Eadsorbate

(1)

where EMOF−adsorbate is the total energy of the MOF−adsorbate sorption system at equilibrium and EMOF and Eadsorbate are the energies of the adsorbate-free MOF structure and the adsorbate, respectively. 21051

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isotherms at other temperatures (50, 70, and 110 °C) are shown in Figure S3 of the Supporting Information. The two figures show that the adsorbed amount increased with the contents of amino group in the linker of UiO-66s, in accordance with the results of Figure 1 that were obtained in the experiments for adsorption kinetics. Figure 3 summarizes

because the adsorbed amount slightly decreased with the presence of amino group (Figure 4b). A slightly lower adsorbed amount over UiO-66-NH2(100), compared with that of the pristine UiO-66, might be due to lower surface area and pore volume of UiO-66-NH2(100) (Table S1 of the Supporting Information). Figure 5 compares the results of Py adsorption in liquid phase from aqueous solutions. The kinetic constants (pseudosecond-order, nonlinear kinetic model26) for adsorption were summarized in Table S2 of the Supporting Information. Like the vapor phase adsorption, the kinetic constant of Py (Table S2 of the Supporting Information) and the adsorbed amount (Figure 5a) of UiO-66-NH2(100) were higher than those of the pristine UiO-66 without amino groups. Adsorption isotherms (Figure 5b) show that the adsorbed Py with UiO-66-NH2(100) was generally higher than that with pristine UiO-66. Therefore, in accordance with vapor phase adsorptions, not only adsorption kinetics but also adsorbed amount of Py increased with the quantity of amino groups in UiO-66s.

4. DISCUSSION Not only the amount of adsorbed Py but also adsorption kinetics increased, both in vapor and liquid phases, as the amino group content of UiO-66s increased. This observation is quite different than our expectation of a repulsive interaction between basic Py and basic amino groups (which might lead to a decreased and slow adsorption of Py). On the other hand, the amino group did not have any noticeable influence on the adsorption kinetics (Figure 4a, inset) and adsorbed amount (Figure 4b) in the adsorption of toluene because there is no specific interaction between toluene and UiO-66s, irrespective of the presence of amino groups. Moreover, similar kinetics of adsorption over pristine UiO-66 was observed with Py and toluene (Figure S5 of the Supporting Information), again suggesting that there are no significant interactions between adsorbates (Py or toluene) and the adsorbents without amino groups (pristine UiO-66). This result is understandable because of similar critical dimensions (Py, 0.66 nm; toluene, 0.66 nm35) or kinetic diameters (Py, ∼0.6 nm; toluene, ∼0.6 nm36) of Py and toluene. There are several interaction mechanisms between organic adsorbates and MOFs, such as electrostatic interaction, coordination, and acid−base interaction.37−39 However, none of these mechanisms can explain our observations. Because the

Figure 3. Effect of temperature on the adsorbed amount of Py over the UiO-66s at a partial pressure of P/P0 = 0.5.

the changes in the adsorbed amount (at P/P0 = 0.5, derived from Figures 2 and Figure S3 of the Supporting Information) of Py with adsorption temperature for the three UiO-66s (i.e., UiO-66, UiO-66-NH2(50), and UiO-66-NH2(100)). From this figure, it was once again confirmed that the adsorbed Py increased with the increasing content of basic amino group. Interestingly, the adsorbed Py increased as the temperature rose to 80 °C, but decreased with any further increase in the temperature. Even though the amount of adsorbed Py was generally less than that (∼12 mmol/g) over a highly porous MOF (MIL-101),22 UiO-66s may still be useful for the removal of Py from the environment. On the other hand, the results of toluene adsorption in the vapor phase (Figure 4) are very different than those of Py adsorption in terms of the adsorption kinetics and the adsorbed amounts. Amino groups in UiO-66s had little favorable effect (or very small decrease in adsorption kinetics with amino group) on the relative kinetics of toluene adsorption, as shown in the inset of Figure 4a. Similarly, amino groups in UiO-66 exert little favorable effect on the amount of adsorbed toluene

Figure 4. (a) Kinetics of toluene adsorption over UiO-66s at 50 °C and (b) adsorption isotherms of toluene over UiO-66s at 50 °C. Inset of panel a shows the relative kinetics of the adsorption. 21052

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Figure 5. (a) Amount of adsorbed Py at various times and (b) adsorption isotherms of Py over UiO-66s. The adsorption was done in liquid phase from aqueous solution of Py.

amino group and Py have hydrogen and electronegative nitrogen, respectively, hydrogen bonding may be a potential mechanism for the favorable adsorption of Py over UiO-66s having amino groups. Theoretical calculations have been used as a tool to gain deep insight into the Py adsorption on the surface of solids.40−43 In this study, calculations were carried out to understand the interactions between Py and UiO-66s, especially basic UiO-66NH2(100). The calculation results show that the N on Py does form a hydrogen bond with the H on the amino group of UiO66-NH2(100), with a binding energy of −74.2 kJ/mol (see Figure 6). On the other hand, when we arranged the N atom

Figure 7. Mulliken charges of −NH2 in UiO-66-NH2(100) (left panel) and N in Py (right panel) (N, blue).

Scheme 1. Schematic Representation of H-Bond and Base− Base Repulsion between Py and UiO-66-NH2

for the case of p-nitrophenol (where the nitro group interacts with amino group of an MOF),44 ammonia (interaction with zinc oxide tetrahedra),45 and CO2 (interaction with amino group)46 even though no repulsion between basic adsorbate and basic adsorbent was expected in those cases. Similarly, hydrogen bonding in functionalized MOFs was utilized very recently in adsorptive denitrogenation and desulfurization of fuel.47 Moreover, it is important to consider the various mechanisms such as hydrogen bonding in the interpretation of adsorption or interaction because Py, for example, is widely used as a probe molecule to characterize acidity by FTIR.13 As shown in Figure 3, the amount of adsorbed Py increased with temperature up to 80 °C and then decreased as the adsorption temperature continued to rise. The increased adsorption with increasing temperature (up to 80 °C) is very unusual in the physisorption of vapor/gas phases (after preevacuation of adsorbents) because adsorption over a clean surface is usually exothermic in such phases.25,34 Even though “gate-opening” with increasing pressure (in other words, adsorption increased abruptly above a certain pressure) has been reported several times by Kitagawa et al.,48,49 a similar

Figure 6. Configuration of Py adsorbed on UiO-66-NH2(100) (Zr, light blue; N, blue; O, red; C, gray; H, white).

on Py to face the N atom on the UiO-66-NH2(100) as the initial configuration, the optimized geometry indicated that the N on Py will again move away to form a hydrogen bond, as shown in Figure 6. This is because both N atoms have negative charges (as shown in Figure 7); thus, they cannot approach each other easily, while the hydrogen bond shown in Figure 6 formed instead because of the favorable adsorption/binding energy. Therefore, it may be suggested that hydrogen bonding is the primary interaction mechanism between Py and basic UiO-66s, and there is no expected repulsive interaction between basic Py and basic UiO-66s because of the very favorable hydrogen bonding. This concept of adsorption mechanism is summarized in Scheme 1. Adsorption of adsorbates over MOFs or MOF composites via hydrogen bonding has been reported recently 21053

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effect with temperature is very rare for an exothermic physisorption process.34 The size of triangular windows of UiO-66 (0.5−0.7 nm)50,51 is quite similar to the critical dimension of Py (0.66 nm)35 or the kinetic diameter of Py (0.60 nm).36 Therefore, the adsorption of Py over UiO-66 may be difficult, especially at low temperatures (for example, 50 °C). Consequently, the amount of adsorbed Py may increase with temperature up to a certain range, while higher temperatures (above 80 °C, for example) will decrease the adsorption in accordance with the observation because of exothermic adsorption over adsorbent surfaces and because the pore size of UiO-66s at high temperatures is wide enough for ready Py adsorption. Zhou et al. demonstrated a fine-tuning of pore sizes of MOFs with changing temperature and introduced the concepts of “adjustable mesh MOFs”52 and “thermosensitive gating effect”.34 We also observed an increase in the adsorption of 1,3,5-trimethylbenzene over a MOF (MIL-96) with increasing temperature, which we explained based on the increased effective pore size of the MOF because of the wide vibrations of MOF lattices at high temperatures.25 The increase of effective pore size of UiO-66s may be also confirmed by the rates of Py adsorption. As shown in Figure S4 of the Supporting Information, the adsorption kinetics increased with increasing temperatures from 45 to 60 °C for all three UiO-66s, and the kinetics for all three UiO-66s are also similar at 60 °C (as shown in Figure S2 of the Supporting Information). Interestingly, the kinetics increased abruptly as the temperature changed from 45 to 50 °C (much larger than the change with the temperature changing from 50 to 60 °C), which shows that a sudden increase in diffusivity (similar to a gate opening) occurs at about 50 °C. Further temperature increases will probably smoothly increase the diffusivity because of the normal temperature effect on diffusion and the expected slight increase of the pore window of UiO-66. Therefore, the unusual increase in Py adsorption with increasing temperature up to 80 °C might be explained by the variable pore size of UiO-66 and increased lattice vibration at high temperatures.

AUTHOR INFORMATION

Corresponding Authors

*Phone: 86-10-64419862. Fax: 86-10-64419862. E-mail: [email protected]. *Phone: 82-10-28185341. Fax: 82-53-950-6330. E-mail: sung@ knu.ac.kr. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (Grant 2013R1A2A2A01007176). The authors thank the beneficial comments of Dr. Nazmul Abedin Khan.

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ABBREVIATIONS Py, Pyridine; MOFs, metal−organic frameworks; BDC, benzenedicarboxylate REFERENCES

(1) Ariga, K.; Ishihara, S.; Abe, H.; Lia, M.; Hill, J. P. Materials Nanoarchitectonics for Environmental Remediation and Sensing. J. Mater. Chem. 2012, 22, 2369−2377. (2) Zhou, Z.; Hartmann, M. Progress in Enzyme Immobilization in Ordered Mesoporous Materials and Related Applications. Chem. Soc. Rev. 2013, 42, 3894−3912. (3) Vinu, A.; Ariga, K. New Ideas for Mesoporous Materials. Adv. Porous Mater. 2013, 1, 63−71. (4) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The Chemistry and Applications of Metal-Organic Frameworks. Science 2013, 341, 1230444. (5) Ariga, K.; Yamauchi, Y.; Rydzek, G.; Ji, Q.; Yonamine, Y.; Wu, K.C.-W.; Hill, J. P. Layer-by-layer Nanoarchitectonics: Invention, Innovation, and Evolution. Chem. Lett. 2014, 43, 36−68. (6) Ariga, K.; Vinu, A.; Yamauchi, Y.; Ji, Q.; Hill, J. P. Nanoarchitectonics for Mesoporous Materials. Bull. Chem. Soc. Jpn. 2012, 85, 1−32. (7) Yang, Q.; Liu, D.; Zhong, C.; Li, J. R. Development of Computational Methodologies for Metal-Organic Frameworks and Their Application in Gas Separations. Chem. Rev. (Washington, DC, U.S.) 2013, 113, 8261−8323. (8) Wu, H.; Gong, Q.; Olson, D. H.; Li, J. Commensurate Adsorption of Hydrocarbons and Alcohols in Microporous Metalorganic Frameworks. Chem. Rev. (Washington, DC, U.S.) 2012, 112, 836−868. (9) Liu, M.-S.; Yu, Q.-Y.; Cai, Y.-P.; Su, C.-Y.; Lin, X.-M.; Zhou, X.X.; Cai, J.-W. One-, Two-, and Three-dimensional Lanthanide Complexes Constructed from Pyridine-2,6-Dicarboxylic Acid and Oxalic Acid Ligands. Cryst. Growth Des. 2008, 8, 4083−4091. (10) Das, M. C.; Ghosh, S. K.; Sañudo, E. C.; Bharadwaj, P. K. Coordination Polymers with Pyridine-2,4,6-Tricarboxylic Acid and Alkaline-earth/Lanthanide/Transition Metals: Synthesis and X-ray Structures. Dalton Trans. 2009, 1644−1658. (11) Hwang, Y.-K.; Hong, D.-Y.; Chang, J.-S.; Jhung, S. H.; Seo, Y.K.; Kim, J.; Vimont, A.; Daturi, M.; Serre, C.; Férey, G. Amine Grafting on Coordinatively Unsaturated Metal Centers of MOFs: Consequences for Catalysis and Metal Encapsulation. Angew. Chem., Int. Ed. 2008, 47, 4144−4148. (12) Bae, Y.-S.; Liu, J.; Wilmer, C. E.; Sun, H.; Dickey, A. N.; Kim, M. B.; Benin, A. I.; et al. The Effect of Pyridine Modification of Ni− DOBDC on CO2 Capture under Humid Conditions. Chem. Commun. (Cambridge, U.K.) 2014, 50, 3296−3298. (13) Lee, J. S.; Yoon, J. W.; Halligudi, S. B.; Chang, J.-S.; Jhung, S. H. Trimerization of Isobutene over WOx/ZrO2 Catalysts. Appl. Catal., A 2009, 366, 299−303.

5. CONCLUSIONS The following conclusions can be drawn from this study: First, the adsorption kinetics and the amount of adsorbed Py (both in the vapor and liquid phases) increased as the amino group content in UiO-66s increased because of a favorable interaction of hydrogen bonding between Py and amino group of the MOFs. Second, the expected repulsion between basic Py and basic MOFs with amino groups was not observed because of this favorable interaction (hydrogen bond). Third, the amount of adsorbed Py increased with increasing temperature up to 80 °C probably because of the similar size of Py and the pore window of UiO-66 coupled with a small increase in the pore size of UiO-66 with increasing temperature. Finally, specific interactions should be carefully considered in order to understand selective adsorption or a mechanism for an adsorption.

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ASSOCIATED CONTENT

S Supporting Information *

Textural properties, kinetic constants, XRD patterns, nitrogen adsorption isotherms, and FTIR spectra of the UiO-66s; adsorption isotherm, effect of temperature, and relative kinetics of Py and toluene adsorption over UiO-66s. This material is available free of charge via the Internet at http://pubs.acs.org. 21054

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Acetalization of Benzaldehyde with Methanol. Appl. Catal., A 2014, 471, 91−97. (34) Zhao, D.; Yuan, D.; Krishna, R.; van Baten, J. M.; Zhou, H.-C. Thermosensitive Gating Effect and Selective Gas Adsorption in a Porous Coordination Nanocage. Chem. Commun. (Cambridge, U.K.) 2010, 46, 7352−7354. (35) Webster, C. E.; Drago, R. S.; Zerner, M. C. Molecular Dimensions for Adsorptive. J. Am. Chem. Soc. 1998, 120, 5509−5516. (36) Davis, T. M.; Chen, C.-Y.; Ž ilková, N.; Vitvarová-Procházková, D.; Č ejka, J.; Zones, S. I. The Importance of Channel Intersections in the Catalytic Performance of High Silica Stilbite. J. Catal. 2013, 298, 84−93. (37) Khan, N. A.; Hasan, Z.; Jhung, S. H. Adsorptive Removal of Hazardous Materials Using Metal-Organic Frameworks (MOFs): A Review. J. Hazard. Mater. 2013, 244−245, 444−456. (38) Khan, N. A.; Hasan, Z.; Jhung, S. H. Adsorption and Removal of Sulfur or Nitrogen Containing Compounds with Metal-Organic Frameworks (MOFs). Adv. Porous Mater. 2013, 1, 91−102. (39) Ahmed, I.; Jhung, S. H. Composites of Metal-Organic Frameworks: Preparation and Application in Adsorption. Mater. Today 2014, 17, 136−146. (40) Mollenhauer, D.; Gaston, N.; Voloshina, E.; Paulus, B. Interaction of Pyridine Derivatives with a Gold (111) Surface as a Model for Adsorption to Large Nanoparticles. J. Phys. Chem. C 2013, 117, 4470−4479. (41) Isvoranu, C.; Wang, B.; Ataman, E.; Schulte, K.; Knudsen, J.; Andersen, J. N.; Bocquet, M.-L.; Schnadt, J. Pyridine Adsorption on Single-Layer Iron Phthalocyanine on Au(111). J. Phys. Chem. C 2011, 115, 20201−20208. (42) Ng, W. K. H.; Liu, J. W.; Liu, Z.-F. Reaction Barriers and Cooperative Effects for the Adsorption of Pyridine on Si(100). J. Phys. Chem. C 2013, 117, 26644−26651. (43) Li, Y.; Guo, W.; Zhu, H.; Zhao, L.; Li, M.; Li, S.; Fu, D.; Lu, X.; Shan, H. Initial Hydrogenations of Pyridine on MoP(001): A Density Functional Study. Langmuir 2012, 28, 3129−3137. (44) Liu, B.; Yang, F.; Zou, Y.; Peng, Y. Adsorption of Phenol and pNitrophenol from Aqueous Solutions on Metal-Organic Frameworks: Effect of Hydrogen Bonding. J. Chem. Eng. Data 2014, 59, 1476−1482. (45) Petit, C.; Bandosz, T. J. Enhanced Adsorption of Ammonia on Metal-Organic Framework/Graphite Oxide Composites: Analysis of Surface Interactions. Adv. Funct. Mater. 2010, 20, 111−118. (46) Planas, N.; Dzubak, A. L.; Poloni, R.; Lin, L.-C.; McManus, A.; McDonald, T. M.; Neaton, J. B.; Long, J. R.; Smit, B.; Gagliardi, L. The Mechanism of Carbon Dioxide Adsorption in an AlkylamineFunctionalized Metal-Organic Framework. J. Am. Chem. Soc. 2013, 135, 7402−7405. (47) De Voorde, B. V.; Boulhout, M.; Vermoortele, F.; Horcajada, P.; Cunha, D.; Lee, J. S.; Chang, J.-S.; Gibson, E.; Daturi, M.; Lavalley, J.C.; et al. N/S-Heterocyclic Contaminant Removal from Fuels by the Mesoporous Metal-Organic Framework MIL-100: The Role of the Metal Ion. J. Am. Chem. Soc. 2013, 135, 9849−9856. (48) Fukushima, T.; Horike, S.; Inubushi, Y.; Nakagawa, K.; Kubota, Y.; Takata, M.; Kitagawa, S. Solid Solutions of Soft Porous Coordination Polymers: Fine-Tuning of Gas Adsorption Properties. Angew. Chem., Int. Ed. 2010, 49, 4820−4824. (49) Tanaka, D.; Nakagawa, K.; Higuchi, M.; Horike, S.; Kubota, Y.; Kobayashi, T. C.; Takata, M.; Kitagawa, S. Kinetic Gate-Opening Process in a Flexible Porous Coordination Polymer. Angew. Chem., Int. Ed. 2008, 47, 3914−3918. (50) Bárcia, P. S.; Guimarães, D.; Mendes, P. A. P.; Silva, J. A. C.; Guillerm, V.; Chevreau, H.; Serre, C.; Rodrigues, A. E. Reverse Shape Selectivity in the Adsorption of Hexane and Xylene Isomers In MOF UiO-66. Microporous Mesoporous Mater. 2011, 139, 67−73. (51) Cunha, D.; Gaudin, C.; Colinet, I.; Horcajada, P.; Maurin, G.; Serre, C. Rationalization of the Entrapping of Bioactive Molecules into a Series of Functionalized Porous Zirconium Terephthalate MOFs. J. Mater. Chem. B 2013, 1, 1101−1108.

(14) Zhang, Y.; Chang, L.; Yan, N.; Tang, Y.; Liu, R.; Rittmann, B. E. UV photolysis for Accelerating Pyridine Biodegradation. Environ. Sci. Technol. 2014, 48, 649−655. (15) Supronowicz, B.; Mavrandonakis, A.; Heine, T. Interaction of Small Gases with the Unsaturated Metal Centers of the HKUST-1 Metal Organic Framework. J. Phys. Chem. C 2013, 117, 14570−14578. (16) Luebbers, M. T.; Wu, T.; Shen, L.; Masel, R. I. Trends in the Adsorption of Volatile Organic Compounds in a Large-pore Metalorganic Framework, IRMOF-1. Langmuir 2010, 26, 11319−11329. (17) Cychosz, K. A.; Wong-Foy, A. G.; Matzger, A. J. Enabling Cleaner Fuels: Desulfurization by Adsorption to Microporous Coordination Polymers. J. Am. Chem. Soc. 2009, 131, 14538−14543. (18) 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. (19) Wu, L.; Xiao, J.; Wu, Y.; Xian, S.; Miao, G.; Wang, H.; Li, Z. A Combined Experimental/Computational Study on the Adsorption of Organosulfur Compounds over Metal−Organic Frameworks from Fuels. Langmuir 2014, 30, 1080−1088. (20) Maes, M.; Trekels, M.; Boulhout, M.; Schouteden, S.; Vermoortele, F.; Alaerts, L.; Heurtaux, D.; Seo, Y.-K.; Hwang, Y. K.; Chang, J.-S.; et al. Selective Removal of N-Heterocyclic Aromatic Contaminants from Fuels by Lewis Acidic Metal-organic Frameworks. Angew. Chem., Int. Ed. 2011, 50, 4210−4214. (21) Ahmed, I.; Khan, N. A.; Jhung, S. H. Graphite Oxide/MetalOrganic Framework (MIL-101): Remarkable Performance in the Adsorptive Denitrogenation of Model Fuels. Inorg. Chem. 2013, 52, 14155−14161. (22) Kim, M. J.; Park, S. M.; Song, S.-J.; Wonc, J.; Lee, J. Y.; Yoon, M.; Kim, K.; Seo, G. Adsorption of Pyridine onto the Metal-Organic Framework MIL-101. J. Colloid Interface Sci. 2011, 361, 612−617. (23) Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P. A New Zirconium Inorganic Building Brick Forming Metal-Organic Frameworks with Exceptional Stability. J. Am. Chem. Soc. 2008, 130, 13850−13851. (24) Kandiah, M.; Nilsen, M. H.; Usseglio, S.; Jakobsen, S.; Olsbye, U.; Tilset, M.; Larabi, C.; Quadrelli, E. A.; Bonino, F.; Lillerud, K. P. Synthesis and Stability of Tagged UiO-66 Zr-MOFs. Chem. Mater. 2010, 22, 6632−6640. (25) Lee, J. S.; Jhung, S. H. Vapor-Phase adsorption of Alkylaromatics on Aluminum-Trimesate MIL-96: An Unusual Increase of Adsorption Capacity with Temperature. Microporous Mesoporous Mater. 2010, 129, 274−277. (26) Hasan, Z.; Jeon, J.; Jhung, S. H. Adsorptive Removal of Naproxen and Clofibric Acid from Water Using Metal-Organic Frameworks. J. Hazard. Mater. 2012, 209−210, 151−157. (27) Yang, Q.; Wiersum, A. D.; Llewellyn, P. L.; Guillerm, V.; Serre, C.; Maurin, G. Functionalizing Porous Zirconium Terephthalate Uio66(Zr) for Natural Gas Upgrading: A Computational Exploration. Chem. Commun. (Cambridge, U.K.) 2011, 47, 9603−9605. (28) Accelrys, Inc. Materials Studio, 5.5 V; Accelrys, Inc.: San Diego, 2010. (29) Perdew, J. P.; Wang, Y. Accurate and Simple Analytic Representation of the Electron-Gas Correlation Energy. Phys. Rev. B: Condens. Matter Mater. Phys. 1992, 45, 13244−13249. (30) Grimme, S. Accurate Description of Van der Waals Complexes by Density Functional Theory Including Empirical Corrections. J. Comput. Chem. 2004, 25, 1463−1473. (31) Ireta, J.; Neugebauer, J.; Scheffler, M.; Rojo, A.; Galván, M. Density Functional Theory Study of the Cooperativity of Hydrogen Bonds in Finite and Infinite α-Helices. J. Phys. Chem. B 2003, 107, 1432−1437. (32) Kandiah, M.; Usseglio, S.; Svelle, S.; Olsbye, U.; Lillerud, K. P.; Tilset, M. Post-synthetic Modification of the Metal-organic Framework Compound UiO-66. J. Mater. Chem. 2010, 20, 9848−9851. (33) Timofeeva, M. N.; Panchenko, V. N.; Jun, J. W.; Hasan, Z.; Matrosova, M. M.; Jhung, S. H. Effects of Linker Substitution on Catalytic Properties of Porous Zirconium Terephthalate Uio-66 in 21055

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The Journal of Physical Chemistry C

Article

(52) Ma, S.; Sun, D.; Wang, X.-S.; Zhou, H.-C. A Mesh-Adjustable Molecular Sieve for General Use in Gas Separation. Angew. Chem., Int. Ed. 2007, 46, 2458−2462.

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