Enhanced Hydrothermal Stability and Catalytic Performance of

Jun 7, 2016 - ... hydrothermal stability of Cu MOF by post synthetic modification with amino acids. Reetu Rani , Akash Deep , Boris Mizaikoff , Suman ...
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Enhanced Hydrothermal Stability and Catalytic Performance of HKUST‑1 by Incorporating Carboxyl-Functionalized Attapulgite Bo Yuan, Xiao-Qian Yin, Xiao-Qin Liu,* Xing-Yang Li, and Lin-Bing Sun* Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing 210009, China

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S Supporting Information *

ABSTRACT: Much attention has been paid to metal−organic frameworks (MOFs) due to their large surface areas, tunable functionality, and diverse structure. Nevertheless, most reported MOFs show poor hydrothermal stability, which seriously hinders their applications. Here a strategy is adopted to tailor the properties of MOFs by means of incorporating carboxyl-functionalized natural clay attapulgite (ATP) into HKUST-1, a wellknown MOF. A new type of hybrid material was thus fabricated from the hybridization of HKUST-1 and ATP. Our results indicated that the hydrothermal stability of the MOFs as well as the catalytic performance was apparently improved. The frameworks of HKUST-1 were severely destroyed after hydrothermal treatment (hot water vapor, 60 °C), while that of the hybrid materials was maintained. For the hybrid materials containing 8.4 wt % of ATP, the surface area reached 1302 m2·g−1 and was even higher than that of pristine HKUST-1 (1245 m2·g−1). In the ring-opening of styrene oxide, the conversion reached 98.9% at only 20 min under catalysis from the hybrid material, which was obviously higher than that over pristine HKUST-1 (80.9%). Moreover, the hybrid materials showed excellent reusability and the catalytic activity was recoverable without loss after six cycles. Our materials provide promising candidates for heterogeneous catalysis owing to the good catalytic activity and reusability. KEYWORDS: carboxyl functionalization, natural clay, hydrothermal stability, ring-opening reaction, reusability

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INTRODUCTION

Attapulgite is a kind of natural clay and belongs to hydrous magnesium−aluminum silicate minerals. The theoretical formula of attapulgite is Al 2 Mg 2 Si 8 O 20 (OH) 2 (OH 2 ) 4 · 4H2O.40−42 There are significant attapulgite reserves in various countries such as China, America, and Spain. In recent years, much attention has been given to the application of attapulgite, owing to its eco-friendly nature, low-cost, and particular morphologies. The structure of attapulgite is shown in Figure S1 in Supporting Information, in which two bands of silica tetrahedra are linked by aluminum ions in octahedral coordination. Additionally, there are abundant active OH groups on the surface that can be used for modification.43−45 Moreover, it has one-dimensional fibrous morphology, and each fiber has a length ranging from several hundred nanometers to several micrometers, as displayed in Figures S2 and S3, Supporting Information.43,46 Meanwhile, MOFs have a three-dimensional network structure with a crystal size that varies from nanometers to micrometers and even to millimeters.47−49 Taking HKUST-1 as an example, it is a typical member of the MOF family and composed of 1,3,5benzenetricarboxylate (H3BTC) organic linkers bound by a dicopper tetracarboxylate paddlewheel secondary building unit (SBU). HKUST-1 has an octahedral shape with a width of 15−

MOFs are highly porous and crystalline solids whose framework is constructed from metal ions and organic ligands. 1−6 Owing to their high surface area, tunable functionality, and diverse structure, MOFs show interesting properties for gas storage7−9 and separation,10−13 as well as use as catalysts14−17 and sensors.18−20 However, MOFs are formed by metal−organic coordination bonds, and their hydrothermal stability is poor. Taking MOF-5 as an example, the collapse of structure occurs irreversibly when exposed to an atmospheric environment for 10 min.21 Water molecules can attack the coordination bonds in the frameworks of MOFs, resulting in the collapse of structure.22−24 In addition, the structure is unrecoverable even if the water is taken away.25,26 Since the discovery of MOFs, many methods have been attempted to overcome the drawback of weak hydrothermal stability. One is the modification of ligands,27−29 in which hydrophobic ligands are introduced to prevent the coordination bonds from being attacked by water molecules. Another method is the hybridization of MOFs with some materials including silica,30−32 graphite oxide (GO),33−36 and carbon nanotubes (CNT).37−39 Hybridization can improve the properties such as adsorption capacity or hydrothermal stability. However, these silica and carbon hybrids require artificial synthesis, and the use of low-cost and eco-friendly natural materials is highly desired. © 2016 American Chemical Society

Received: April 7, 2016 Accepted: June 7, 2016 Published: June 7, 2016 16457

DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464

Research Article

ACS Applied Materials & Interfaces 50 μm.50 As a result, the distinction in size makes it probable to construct MOF crystals in the presence of attapulgite fibers. In this study, a strategy is developed to tailor the properties of HKUST-1 by hybridizing with carboxyl-functionalized attapulgite (ATP). The ATP was mixed with a solution that included the precursors Cu(NO3)2·3H2O and H3BTC to participate in the crystallization of HKUST-1 (Figure 1). A

ranges from 1 to 4, relying on the content of ATP used. The actual ATP contents (varied from 3.6 wt % to 25.9 wt %) were determined by Jarrell-Ash 1100 inductively coupling plasma (ICP) and thermogravimetric (TG) analysis. The results obtained from ICP and TG are in good agreement with each other as depicted in Table 1. For comparison, HKUST-1 was prepared following a similar process for HKUST-1/ATP hybrid materials except that no ATP was added.

Table 1. ATP Contents and Structural Properties of Different Samples sample

ATP content (wt %)

SBET (m2·g−1)

Vp (cm3·g−1)

HKUST-1 HA-1 HA-2 HA-3 HA-4 ATP

0 3.6 (4.0)a 8.4 (8.9)a 18.3 (18.5)a 25.9 (26.1)a 100

1245 1258 1302 978 851 123

0.68 0.75 0.82 0.72 0.69 0.54

a

The content of ATP was measured by ICP, and the value in parentheses was measured by TG.

Materials Characterization. X-ray diffraction (XRD) measurements were conducted on a Bruker D8 Avance diffractometer with Cu Kα at 40 kV and 40 mA. Scanning electronic microscopy (SEM) was carried out on a Hitachi S4800 electron microscope operating at 20 kV. To avoid charging, a thin layer of gold was applied on samples. Fourier transform infrared (IR) spectra were measured on a Nicolet Nexus 470 spectrometer with a KBr wafer, where the proportion of KBr to sample is 150:1. TG and derivatives (DTG) were conducted using a thermobalance (STA-499C, NETZSCH) heating from 40 °C to 600 °C in a flow of N2 (25 mL·min−1). The N2 adsorption− desorption isotherms were undertaken at −196 °C, employing an ASAP 2020 instrument. Prior to each analysis, the samples were outgassed at 150 °C for 4 h. The Brunauer−Emmett−Teller (BET) model was used to calculate the surface areas, and the relative pressure ranged from 0.04 to 0.20. Total pore volumes were determined at a relative pressure of 0.99. Through the density-functional-theory (DFT) method, the pore diameters were calculated from the adsorption isotherms. The hydrothermal stability of materials was examined as follows. To separate the water from the solids, the samples (0.02 g) were transferred into an open vial and then put inside an autoclave that contained 2 mL of deionized water. The autoclave was kept at 60 °C for 12 h, and the vapor pressure in the closed autoclave was 19.92 kPa. The resultant solids were dried and characterized by XRD. The hydrothermal stability was evaluated by the alterations in XRD patterns. Catalytic Tests. The ring-opening of styrene oxide was conducted in a hermetic flask. The catalysts were stored under vacuum prior to reactions. All of the reactions were performed in nitrogen atmosphere. The catalyst (0.1 g) and styrene oxide (2.5 mmol) were dissolved in methanol (15 mL) and kept at 50 °C with stirring. After reacting for 5, 20, 45, and 80 min, the supernatant liquor was taken out and analyzed. An Agilent Technologies 7890A gas chromatograph (GC) equipped with an HP-5 capillary column and a flame ionization detector (FID) was used for analysis. A moderate amount of methanol was applied to wash away the physisorbed reagents. The resulting catalyst was dried and reused in a new reaction, in which the conditions were the same as in the first run.

Figure 1. Schematic illustrations for the preparation of (a) HKUST-1 and (b) HKUST-1/ATP hybrid materials.

new sort of hybrid material related to MOFs and ATP was thus constructed. It is noticeable that the hydrothermal stability of the hybrid materials is greatly enhanced in contrast to pure HKUST-1. For the hybrid material which has 8.9 wt % of ATP, the surface area is even higher than that of HKUST-1. Furthermore, the hybrid material showed excellent catalytic activity in the ring-opening reaction. The conversion reached 98.9%, which was apparently higher than that over HKUST-1 (80.9%) and ATP (1.0%). In addition, the catalytic activity was recoverable without loss after six cycles.

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EXPERIMENTAL SECTION

Chemicals. Copper nitrate trihydrate [Cu(NO3)2·3H2O, 99.5%], vinyltrimethoxysilane (C 5 H 12 O 3 Si, 98%), KMnO 4 (>99.5%), NaHSO3(58.5%), N,N-dimethylformamide (DMF, ≥99.5%), dichloromethane (≥99.5%), ethanol (≥99.7%), and absolute methanol were supplied by Sinopharm Chemical Reagent Co., Ltd. Styrene oxide (>98%), H3BTC(98%), and sodium periodate (NaIO4, >99%) were purchased from Aladdin Industrial Co. Attapulgite was provided by Xuyi Jiuchuan Clay Technology Co. Toluene (C7H8, >99.5%) and hydrochloric acid (37%) were supplied by Lingfeng Chemical Reagent Co., Ltd. In all experiments, deionized water was employed. Materials Synthesis. Attapulgite (0.6 g) was put into toluene (20 mL), and a homogeneous solution was prepared by sonicating for 30 min. Then vinyltrimethoxysilane (C5H12O3Si, 1 mL) was slowly added to the solution with stirring. The mixture was stirred at 75 °C for 8 h and then filtered with toluene and ethanol. After being dried, the product was added into a solution containing KMnO4 (0.16 g), NaIO4 (4.2 g), and deionized water (200 mL). The whole mixture was stirred at room temperature for 24 h. Then the mixture was filtered, washed with a solution containing NaHSO3, and dried. Cu(NO3)2·3H2O (0.6 g), H3BTC (0.3 g), and a prescribed amount of ATP were transferred into a mixture containing ethanol (10 mL), deionized water (10 mL), and DMF (10 mL). The resulting mixture was sonicated for 15 min to form a homogeneous solution and then heated at 85 °C for 24 h with mild stirring. The precipitate was filtered and washed with DMF and methanol. The product was immersed in CH2Cl2 solvent, which was changed two times in 3 days. The obtained solids were kept in a desiccator and are referred to as HA-n, where n

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RESULTS Surface Functionalization of Attapulgite. Attapulgite was first grafted with CC groups followed by the oxidation of CC groups to COOH groups. Figure 2A shows the IR spectra of the surface functionalization process of attapulgite. For pristine attapulgite, the characteristic bands are located at 1200−930 cm−1. Owing to the stretching vibration of OH in 16458

DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464

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Figure 3. XRD patterns of HKUST-1, HKUST-1/ATP hybrid materials, and ATP.

1. The elemental composition of hybrid materials was analyzed by ICP (Table S1, Supporting Information). The element Cu derived from HKUST-1 as well as Al and Mg originating from ATP were detected. Moreover, the amounts of Al and Mg keep increasing with the increase of ATP content. These results demonstrate that ATP is part of the framework. The morphologies of HKUST-1, ATP, and hybrid materials were measured by SEM and are displayed in Figure 4, and Figure S8, Supporting Information. For ATP, fibrous shapes with a length of about 1 μm can be seen. Instead of the conventional synthesis under static conditions, all of the samples were synthesized during stirring. This is responsible for the relatively poor crystal quality. Nevertheless, the stirring condition is beneficial to the hybridization of ATP with MOFs. Similar results have been reported in the literature.36,51,52 In the case of hybrid materials, ATP can be easily found on the surface from the SEM images. For HA-1, a few fibers can be viewed on the surface owing to the low content of ATP. However, more ATP fibers become visible as the content of ATP increases. In the case of HA-4, few isolated ATP fibers appear, indicating that an excess of ATP has been introduced. Moreover, elemental mapping of HA-3 is shown in Figure S9, Supporting Information. The elemental Cu derived from HKUST-1 as well as Al and Mg originating from ATP are observable throughout the sample. This confirms that ATP is well hybridized with HKUST-1. IR spectra of HKUST-1/ATP hybrid materials are shown in Figure 5. For HKUST-1, the bands at 1645 and 1590 cm−1 are ascribed to the carboxylate asymmetric stretch, while the symmetric stretch can be observed at 1450 and 1370 cm−1.53 In comparison with HKUST-1, the IR spectra of hybrid materials show bands at 1200−930 cm−1 derived from ATP, suggesting the incorporation of ATP. Moreover, these characteristic bands of ATP become progressively intense in the hybrid materials when the content of ATP increases. IR spectra of hybrid materials clearly show the disappearance of the band at 1755 cm−1 in ATP, which is derived from the stretching vibrations of COOH groups. This means that the COOH groups in ATP chelate the copper metal in HKUST-1. Besides, the band at 3546 cm−1 disappears, which indicates that the OH groups in ATP may coordinate with copper, too. The hybrid material HA-2 shows a contact angle of 35.6° (Figure S10, Supporting Information), which is between that of carboxyl-functionalized attapulgite (10.8°) and HKUST-1 (55.3°). This suggests that ATP is well hybridized with HKUST-1. Figure 6 shows N2 adsorption isotherms and pore size distributions of the materials. Only a small amount N2 is

Figure 2. (A) IR spectra and (B) water contact angle images of (a) pure attapulgite, (b) attapulgite grafted with CC groups, and (c) attapulgite grafted with COOH groups.

dioctahedral coordination (Al2OH) and water coordinated to Mg, the band at 3620 cm−1 can be observed. In addition, the band at 3546 cm−1 originating from stretching vibrations of OH was associated with (Al, Mg)−OH.43 These results indicate that there are abundant OH groups in attapulgite. For attapulgite grafted with CC groups, the vibration of CC can be observed at 1605 cm−1. Two bands at 1407 and 3000 cm−1 originate from the vibration of C−H related to CC groups. For attapulgite grafted with COOH groups, the vibration of CO can be seen at 1755 cm−1. In addition, the bands at 1407 and 3000 cm−1 disappear, which means that the CC groups are totally transformed to COOH groups. The introduction of different groups may lead to a change in hydrophilic−hydrophobic properties; thus, water contact angles of different samples were measured (Figure 2B). For original attapulgite possessing OH groups, the contact angle is 22.6°, indicating a hydrophilic surface. However, the contact angle of CC group-grafted attapulgite becomes 95.2°, which indicates that the surface has become hydrophobic. Interestingly, after grafting COOH groups, the contact angle is only 10.8°, which is even smaller than that of original attapulgite and suggests a more hydrophilic surface. The results of IR spectroscopy and contact angle measurement thus demonstrate that COOH groups are successfully grafted onto the surface of attapulgite through the intermediate containing CC groups. Structural and Surface Properties of Hybrid Materials. The XRD patterns of HKUST-1, ATP, and hybrid materials are displayed in Figure 3. For HKUST-1, the diffraction lines of HKUST-1 are in line with that reported previously.50 ATP exhibits a relatively strong diffraction peak at about 8.5°, along with some weak ones at high degrees. For the hybrid materials, the patterns of both HKUST-1 and ATP can be observed. To facilitate observations, enlarged figures focusing on the ATP signature peak at 8.5° in the hybrid materials and the individual XRD patterns are provided (Figures S4−S7, Supporting Information). It is clear that with increasing loading amount of ATP, the diffraction peaks for HKUST-1 become weakened and the diffraction peaks of ATP increase gradually. This indicates that ATP does not obstruct the formation of HKUST16459

DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464

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Figure 4. SEM images of (a) HKUST-1, (b) HA-1, (c) HA-2, (d) HA-3, (e) HA-4, and (f) ATP.

Figure 5. IR spectra of HKUST-1, HKUST-1/ATP hybrid materials, and ATP.

adsorbed on ATP when the relative pressures are low. When the relative pressures are higher than 0.8, the uptake increases obviously and a hysteresis loop is visible. Unlike ATP, HKUST1 is a typical microporous material and shows an isotherm of type I. The hybrid materials show isotherms similar to that for pure HKUST-1. In addition, a small hysteresis loop can be observed when the relative pressures are high. This implies that some meso/macropores are formed after the incorporation of ATP. The network of HKUST-1 is made of 8.6 Å square

Figure 6. (A) N2 adsroption isotherms and (B) pore size distributions of HKUST-1, HKUST-1/ATP hybrid materials, and ATP.

channels, as shown in Figure 6B.54 With the increase of ATP, for HA-3 especially, the main pore diameters reveal a tendency 16460

DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464

Research Article

ACS Applied Materials & Interfaces to diminish. More obviously, for HA-4 containing 25.9 wt % of ATP, a new pore generated by ATP at 40 nm can be observed. These results demonstrate that the incorporation of ATP affects the formation of HKUST-1. Table 1 presents pore structure parameters calculated from isotherms. For HA-1 and HA-2, the surface areas are even higher than that of HKUST-1, which should be caused by new pores created after the incorporation of ATP. However, when the content of ATP is excessive (e.g., in HA-4), the surface areas decrease due to the low surface area of ATP. On the basis of characterization results, a new sort of hybrid material has been constructed by incorporating ATP into HKUST-1. The hybrid materials possess the crystal structure of MOFs whereas ATP participates in the formation of crystals. By incorporating an apporporiate amount of ATP, the surface areas and pore volumes of the MOFs can be improved. Stability Examination. Figure 7 shows the TG and DTG curves of samples to evaluate the thermal stability. For ATP,

Figure 8. XRD patterns of HKUST-1 and HKUST-1/ATP hybrid materials after hydrothermal treatment.

disappeared and a new peak at 10.1° arose. This indicates damage to the crystal structure. Surprisingly, the hybrid materials show an obvious improvement of the hydrothermal stability. Regardless of the ATP content, all of the treated hybrid materials present XRD patterns comparable to the untreated one. To further examine the stability of the hybrid materials, N2 adsorption−desorption isotherms were measured before and after treatment. As shown in Figure S11, Supporting Information, the N2 uptake of HKUST-1 after treatment obviously decreased, while the treated hybrid material HA-2 shows an uptake comparable to the untreated one. These indicate that the crystal structure for the hybrid materials can be well preserved when subjected to hydrothermal treatment. Catalytic Performance. The resulting materials were utilized to catalyze the ring-opening of styrene oxide for the preparation of 2-methoxy-2-phenylethanol (MPE).55 Traditionally, homogeneous acids or bases, such as FeCl3 and CuCl2, are applied to catalyze the reaction, resulting in problems of separation and waste disposal. Because of large surface areas and a high content of copper metal, HKUST-1 and hybrid materials are potential candidates to catalyze the reaction.56 The results are displayed in Figure 9. For ATP, only a negligible

Figure 7. (A) TG and (B) DTG profiles of HKUST-1, HKUST-1/ ATP hybrid materials, and ATP. For clarity, curves are drawn offset.

three weight losses are observed. The desorption of physically adsorbed water and hybrid water takes place at about 60 °C and 160 °C, respectively. The removal of coordinated water occurs at temperatures ranging from 325 °C to 375 °C. For HKUST1, the removal of free water and crystallization water occurs at 100 °C and around 300 °C, respectively. The sharp peak occurring at 360 °C is derived from the decomposition of organic ligands (BTC), which indicates the collapse of frameworks. In the case of the hybrid materials, the TG and DTG curves are similar to that of pure HKUST-1, which implies that the incorporation of ATP does not compromise the thermal stability of HKUST-1. In practical applications, hydrothermal stability of MOFs is a concern. To test it, materials were kept at 60 °C for 12 h in water vapor. The treated samples were characterized by XRD, and the results are displayed in Figure 8. In the case of HKUST-1, the main diffraction peaks at 9.7° and 11.6° almost

Figure 9. Ring-opening of styrene oxide under catalysis from HKUST1, HKUST-1/ATP hybrid materials, and ATP.

amount of styrene oxide is converted even at 80 min because of the absence of active sites. When HKUST-1 is used as the catalyst, the conversion of styrene oxide is 80.9%, implying that there are catalytically active sites. It is obvious that the conversion over the hybrid materials increases first and then decreases with the increasing content of ATP. The conversion reached 98.9% under catalysis from HA-2, which was obviously higher than that over pristine HKUST-1 (80.9%). Reusability of heterogeneous catalysts is of great importance for practical applications. Figure 10 shows the catalytic activity 16461

DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464

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two hybridization modes, ATP may keep the coordinated bonds (Cu−O) away from the water molecules. Furthermore, the hybrid materials show excellent catalytic activity in the ring-opening of styrene oxide. The conversion over HA-2 can reach 98.9%, which is even higher than that over HKUST-1 (80.9%). One factor that should be considered for the enhanced catalytic performance is the change of pore structure by ATP incorporation. As shown in N2 adsorption− desorption isotherms, some meso/macropores are generated after hybridizing with ATP. This leads to the exposure of more active sites to catalyze the reaction. Besides, for the hybrid materials comprising a suitable amount of ATP, the surface areas also increase, which may also account for the enhanced catalytic activity. Because the same amount of catalysts were used for the reaction, the hybrid materials HA-1 and HA-2 possess less active sites than HKUST-1. To further examine the factors affecting the activity, the turnover frequency (TOF) which represents the turnover number of copper per unit time was calculated. The TOF of HKUST-1, HA-1, and HA-2 is 3.32, 4.17, and 4.44 h−1, respectively. Obviously, the hybrid materials HA-1 and HA-2 display activity higher than that of HKUST-1. On the basis of the above analysis, the enhanced activity should be ascribed to newly generated pores and higher surface areas, which make the active sites in HA-1 and HA-2 more accessible to the reactants.

Figure 10. Reusability of the hybrid material HA-2 in the ring-opening reaction.

of recovered hybrid materials. The conversion of styrene oxide remains nearly constant over HA-2 in the six continuous cycles. The catalytic activity of the recovered catalyst is comparable to that of the fresh one. The conversion is 98.8% after six cycles, which is somewhat higher than that on the fresh catalyst (98.2%). This discrepancy should be caused by experimental error. The excellent catalyst reusability for the ring-opening of styrene oxide is thus demonstrated by the aforementioned results.

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DISCUSSION Due to their large surface areas, abundant active sites, and tunable functionality, MOFs are promising candidates in diverse fields including adsorption and catalysis. However, poor hydrothermal stability seriously obstructs their practical applications. In the present study, hybridizing with ATP enhances the hydrothermal stability of MOFs. A new sort of hybrid material originating from MOFs and ATP was thus constructed. The hydrothermal stability of HKUST-1 is greatly improved by hybridization with ATP. When the samples were exposed to water vapor at 60 °C for 12 h, the framework of HKUST-1 was impaired, while hybrid materials maintained their structure well. Obviously, the improved hydrothermal stability is attributed to the introduction of ATP. In the preparation of the hybrid materials, ATP first coordinates with MOF precursors, leading to nucleation followed by crystal growth. Incorporation of ATP results in a change of pore structure and hydrothermal stability. By using the SEM technique, the ATP fibers on the surface of the MOFs are easily observed. Moreover, two hybridization modes are revealed by IR spectroscopy. The peak at 3546 cm−1, derived from the vibrations of OH in (Al, Mg)−OH, and the band at 1755 cm−1 related to the vibrations of COOH groups in ATP, disappear. These results imply that the COOH groups of ATP and the OH groups in (Al, Mg)−OH may coordinate with the copper in HKUST-1, yielding a structure such as COO−Cu and (Al, Mg)−O−Cu, respectively. In other words, ATP chelates the metal followed by growth of the MOFs. A reference sample, Cu-ATP, was also synthesized by the reaction of Cu(NO3)2 with ATP in the absence of BTC. The synthetic process was similar to that for HKUST-1/ATP hybrid materials except that no BTC was added. The obtained sample was characterized by XRD and ICP. The XRD pattern of Cu-ATP is comparable to that of pristine ATP, and no new diffraction peak is observed (Figure S12, Supporting Information). ICP results show the presence of Cu (1.4%) in the Cu-ATP sample. This means the formation of a few discontinuous fragments due to the coordination of Cu2+ with COOH in ATP. Through the

CONCLUSIONS A natural clay, ATP, was incorporated into HKUST-1, producing a new kind of hybrid material. In contrast to silica and carbon materials employed for hybridization, ATP is ecofriendly and inexpensive. After incorporation of ATP, the framework of HKUST-1 can be well preserved and the hydrothermal stability is greatly improved. When an appropriate amount of ATP is introduced, the surface areas of the hybrid materials are even higher than that of pure HKUST-1. Such hybrid materials exhibit good catalytic activity in the ringopening reaction of styrene oxide. Furthermore, the catalytic activity of recovered hybrid materials retains about 100% activity even after six cycles. These new and stable MOF-based materials with excellent activity and improved hydrothermal stability are highly promising for practical applications.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.6b04127. XRD, SEM, TEM, N2 adsorption/desorption isotherms, element mapping, and water contact angle images of different samples (PDF)

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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 Financial support from the National High Technology Research and Development Program of China (863 Program, 2013AA032003), the National Natural Science Foundation of China (21576137), the Distinguished Youth Foundation of 16462

DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464

Research Article

ACS Applied Materials & Interfaces

layer Colloidal Crystals for Highly Efficient Vapor Sensing. Chem. Mater. 2015, 27, 7601−7609. (21) Kaye, S. S.; Dailly, A.; Yaghi, O. M.; Long, J. R. Impact of Preparation and Handling on the Hydrogen Storage Properties of Zn4O(1,4-Benzenedicarboxylate)3 (MOF-5). J. Am. Chem. Soc. 2007, 129, 14176−14177. (22) Burtch, N. C.; Jasuja, H.; Walton, K. S. Water Stability and Adsorption in Metal−Organic Frameworks. Chem. Rev. 2014, 114, 10575−10612. (23) Gupta, K. M.; Zhang, K.; Jiang, J. W. Water Desalination through Zeolitic Imidazolate Framework Membranes: Significant Role of Functional Groups. Langmuir 2015, 31, 13230−13237. (24) Zhang, J. W.; Zhang, H. T.; Du, Z. Y.; Wang, X. Q.; Yu, S. H.; Jiang, H. L. Water-Stable Metal-Organic Frameworks with Intrinsic Peroxidase-Like Catalytic Activity as a Colorimetric Biosensing Platform. Chem. Commun. 2014, 50, 1092−1094. (25) Ahmed, I.; Jhung, S. H. Composites of Metal−Organic Frameworks: Preparation and Application in Adsorption. Mater. Today 2014, 17, 136−146. (26) Kang, I. J.; Khan, N. A.; Haque, E.; Jhung, S. H. Chemical and Thermal Stability of Isotypic Metal−Organic Frameworks: Effect of Metal Ions. Chem. - Eur. J. 2011, 17, 6437−6442. (27) Jasuja, H.; Huang, Y. G.; Walton, K. S. Adjusting the Stability of Metal−Organic Frameworks under Humid Conditions by Ligand Functionalization. Langmuir 2012, 28, 16874−16880. (28) Ma, D. Y.; Li, Y. W.; Li, Z. Tuning the Moisture Stability of Metal-Organic Frameworks by Incorporating Hydrophobic Functional Groups at Different Positions of Ligands. Chem. Commun. 2011, 47, 7377−7379. (29) Li, S.; Huo, F. Metal−Organic Framework Composites: From Fundamentals to Applications. Nanoscale 2015, 7, 7482−7501. (30) Ahmed, A.; Forster, M.; Clowes, R.; Bradshaw, D.; Myers, P.; Zhang, H. F. Silica SOS@HKUST-1 Composite Microspheres as Easily Packed Stationary Phases for Fast Separation. J. Mater. Chem. A 2013, 1, 3276−3286. (31) Zhu, Q. L.; Xu, Q. Metal-Organic Framework Composites. Chem. Soc. Rev. 2014, 43, 5468−5512. (32) Zhao, M. T.; Deng, K.; He, L. C.; Liu, Y.; Li, G. D.; Zhao, H. J.; Tang, Z. Y. Core−Shell Palladium Nanoparticle@Metal−Organic Frameworks as Multifunctional Catalysts for Cascade Reactions. J. Am. Chem. Soc. 2014, 136, 1738−1741. (33) Petit, C.; Mendoza, B.; Bandosz, T. J. Reactive Adsorption of Ammonia on Cu-Based MOF/Graphene Composites. Langmuir 2010, 26, 15302−15309. (34) 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. (35) Petit, C.; Bandosz, T. J. MOF-Graphite Oxide Composites: Combining the Uniqueness of Graphene Layers and Metal-Organic Frameworks. Adv. Mater. 2009, 21, 4753−4757. (36) Zu, D.-D.; Lu, L.; Liu, X.-Q.; Zhang, D.-Y.; Sun, L.-B. Improving Hydrothermal Stability and Catalytic Activity of Metal−Organic Frameworks by Graphite Oxide Incorporation. J. Phys. Chem. C 2014, 118, 19910−19917. (37) Wen, P.; Gong, P. W.; Sun, J. F.; Wang, J. Q.; Yang, S. R. Design and Synthesis of Ni-MOF/CNT Composites and rGo/Carbon Nitride Composites for an Asymmetric Supercapacitor with High Energy and Power Density. J. Mater. Chem. A 2015, 3, 13874−13883. (38) Lin, R. J.; Ge, L.; Liu, S. M.; Rudolph, V.; Zhu, Z. H. MixedMatrix Membranes with Metal−Organic Framework-Decorated CNT Fillers for Efficient CO2 Separation. ACS Appl. Mater. Interfaces 2015, 7, 14750−14757. (39) Han, T. T.; Xiao, Y. L.; Tong, M. M.; Huang, H. L.; Liu, D. H.; Wang, L. Y.; Zhong, C. L. Synthesis of CNT@MIL-68(Al) Composites with Improved Adsorption Capacity for Phenol in Aqueous Solution. Chem. Eng. J. 2015, 275, 134−141. (40) Ma, J. F.; Zou, J.; Li, L. Y.; Yao, C.; Kong, Y.; Cui, B. Y.; Zhu, R. L.; Li, D. L. Nanocomposite of Attapulgite-Ag3PO4 for Orange II Photodegradation. Appl. Catal., B 2014, 144, 36−40.

Jiangsu Province (BK20130045), the Fok Ying-Tong Education Foundation (141069), the National Basic Research Program of China (973 Program, 2013CB733504), and the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions is greatly acknowledged.

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REFERENCES

(1) Liu, J. W.; Chen, L. F.; Cui, H.; Zhang, J. Y.; Zhang, L.; Su, C. Y. Applications of Metal-Organic Frameworks in Heterogeneous Supramolecular Catalysis. Chem. Soc. Rev. 2014, 43, 6011−6061. (2) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The Chemistry and Applications of Metal-Organic Frameworks. Science 2013, 341, 1230444−1230444. (3) Sun, L. B.; Li, J. R.; Park, J.; Zhou, H. C. Cooperative TemplateDirected Assembly of Mesoporous Metal-Organic Frameworks. J. Am. Chem. Soc. 2012, 134, 126−129. (4) Wang, C.; Liu, D. M.; Lin, W. B. Metal-Organic Frameworks as a Tunable Platform for Designing Functional Molecular Materials. J. Am. Chem. Soc. 2013, 135, 13222−13234. (5) Furukawa, H.; Gandara, F.; Zhang, Y. B.; Jiang, J. C.; Queen, W. L.; Hudson, M. R.; Yaghi, O. M. Water Adsorption in Porous MetalOrganic Frameworks and Related Materials. J. Am. Chem. Soc. 2014, 136, 4369−4381. (6) Li, J. R.; Sculley, J.; Zhou, H. C. Metal-Organic Frameworks for Separations. Chem. Rev. 2012, 112, 869−932. (7) Mason, J. A.; Veenstra, M.; Long, J. R. Evaluating Metal-Organic Frameworks for Natural Gas Storage. Chem. Sci. 2014, 5, 32−51. (8) Yan, Y.; Yang, S. H.; Blake, A. J.; Schroder, M. Studies on MetalOrganic Frameworks of Cu(II) with Isophthalate Linkers for Hydrogen Storage. Acc. Chem. Res. 2014, 47, 296−307. (9) 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. (10) Zhang, Z. J.; Yao, Z. Z.; Xiang, S. C.; Chen, B. L. Perspective of Microporous Metal-Organic Frameworks for CO2 Capture and Separation. Energy Environ. Sci. 2014, 7, 2868−2899. (11) Zhang, T.; Lin, W. B. Metal-Organic Frameworks for Artificial Photosynthesis and Photocatalysis. Chem. Soc. Rev. 2014, 43, 5982− 5993. (12) Xia, W.; Mahmood, A.; Zou, R. Q.; Xu, Q. Metal-Organic Frameworks and Their Derived Nanostructures for Electrochemical Energy Storage and Conversion. Energy Environ. Sci. 2015, 8, 1837− 1866. (13) Qiu, S. L.; Xue, M.; Zhu, G. S. Metal-Organic Framework Membranes: From Synthesis to Separation Application. Chem. Soc. Rev. 2014, 43, 6116−6140. (14) Ahmed, I.; Khan, N. A.; Jhung, S. H. Graphite Oxide/Metal− Organic Framework (MIL-101): Remarkable Performance in the Adsorptive Denitrogenation of Model Fuels. Inorg. Chem. 2013, 52, 14155−14161. (15) Zhao, M.; Ou, S.; Wu, C. D. Porous Metal-Organic Frameworks for Heterogeneous Biomimetic Catalysis. Acc. Chem. Res. 2014, 47, 1199−1207. (16) Gascon, J.; Corma, A.; Kapteijn, F.; Llabrés i Xamena, F. X. Metal Organic Framework Catalysis: Quo Vadis? ACS Catal. 2014, 4, 361−378. (17) Mo, K.; Yang, Y. H.; Cui, Y. A Homochiral Metal-Organic Framework as an Effective Asymmetric Catalyst for Cyanohydrin Synthesis. J. Am. Chem. Soc. 2014, 136, 1746−1749. (18) Cui, Y. J.; Chen, B. L.; Qian, G. D. Lanthanide Metal-Organic Frameworks for Luminescent Sensing and Light-Emitting Applications. Coord. Chem. Rev. 2014, 273, 76−86. (19) Hu, Z. C.; Deibert, B. J.; Li, J. Luminescent Metal-Organic Frameworks for Chemical Sensing and Explosive Detection. Chem. Soc. Rev. 2014, 43, 5815−5840. (20) Li, L. M.; Jiao, X. L.; Chen, D. R.; Lotsch, B. V.; Li, C. Facile Fabrication of Ultrathin Metal−Organic Framework-Coated Mono16463

DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464

Research Article

ACS Applied Materials & Interfaces (41) Pan, J. M.; Li, L. Z.; Hang, H.; Wu, R. R.; Dai, X. H.; Shi, W. D.; Yan, Y. S. Fabrication and Evaluation of Magnetic/Hollow DoubleShelled Imprinted Sorbents Formed by Pickering Emulsion Polymerization. Langmuir 2013, 29, 8170−8178. (42) Chen, H. C.; Zhao, C. S.; Yu, W. W. Calcium-Based Sorbent Doped with Attapulgite for CO2 Capture. Appl. Energy 2013, 112, 67− 74. (43) Li, X.-Y.; Zhang, D.-Y.; Liu, X.-Q.; Shi, L.-Y.; Sun, L.-B. A Tandem Demetalization−Desilication Strategy to Enhance the Porosity of Attapulgite for Adsorption and Catalysis. Chem. Eng. Sci. 2016, 141, 184−194. (44) Mu, B.; Wang, A. One-Pot Fabrication of Multifunctional Superparamagnetic Attapulgite/Fe3O4/Polyaniline Nanocomposites Served as an Adsorbent and Catalyst Support. J. Mater. Chem. A 2015, 3, 281−289. (45) Deng, Y. H.; Gao, Z. Q.; Liu, B. Z.; Hu, X. B.; Wei, Z. B.; Sun, C. Selective Removal of Lead from Aqueous Solutions by Ethylenediamine-Modified Attapulgite. Chem. Eng. J. 2013, 223, 91−98. (46) Lu, L.; Li, X.-Y.; Liu, X.-Q.; Wang, Z.-M.; Sun, L.-B. Enhancing the Hydrostability and Catalytic Performance of Metal−Organic Frameworks by Hybridizing with Attapulgite, a Natural Clay. J. Mater. Chem. A 2015, 3, 6998−7005. (47) Eddaoudi, M.; Sava, D. F.; Eubank, J. F.; Adil, K.; Guillerm, V. Zeolite-Like Metal-Organic Frameworks (ZMOFs): Design, Synthesis, and Properties. Chem. Soc. Rev. 2015, 44, 228−249. (48) Zhang, W. N.; Lu, G.; Cui, C. L.; Liu, Y. Y.; Li, S. Z.; Yan, W. J.; Xing, C.; Chi, Y. R.; Yang, Y. H.; Huo, F. W. A Family of MetalOrganic Frameworks Exhibiting Size-Selective Catalysis with Encapsulated Noble-Metal Nanoparticles. Adv. Mater. 2014, 26, 4056−4060. (49) Sindoro, M.; Yanai, N.; Jee, A. Y.; Granick, S. Colloidal-Sized Metal-Organic Frameworks: Synthesis and Applications. Acc. Chem. Res. 2014, 47, 459−469. (50) Rowsell, J. L. C.; Yaghi, O. M. Effects of Functionalization, Catenation, and Variation of the Metal Oxide and Organic Linking Units on the Low-Pressure Hydrogen Adsorption Properties of Metal−Organic Frameworks. J. Am. Chem. Soc. 2006, 128, 1304−1315. (51) Liu, S.; Sun, L.; Xu, F.; Zhang, J.; Jiao, C.; Li, F.; Li, Z.; Wang, S.; Wang, Z.; Jiang, X.; Zhou, H.; Yang, L.; Schick, C. Nanosized CuMOFs Induced by Graphene Oxide and Enhanced Gas Storage Capacity. Energy Environ. Sci. 2013, 6, 818−823. (52) Li, L.; Liu, X. L.; Gao, M.; Hong, W.; Liu, G. Z.; Fan, L.; Hu, B.; Xia, Q. H.; Liu, L.; Song, G. W.; Xu, Z. S. The Adsorption on Magnetic Hybrid Fe3O4/HKUST-1/GO of Methylene Blue from Water Solution. J. Mater. Chem. A 2014, 2, 1795−1801. (53) Vinu, A.; Ariga, K.; Mori, T.; Nakanishi, T.; Hishita, S.; Golberg, D.; Bando, Y. Preparation and Characterization of Well-Ordered Hexagonal Mesoporous Carbon Nitride. Adv. Mater. 2005, 17, 1648− 1652. (54) Campbell, J.; Szekely, G.; Davies, R. P.; Braddock, D. C.; Livingston, A. G. Fabrication of Hybrid Polymer/Metal Organic Framework Membranes: Mixed Matrix Membranes Versus in Situ Growth. J. Mater. Chem. A 2014, 2, 9260−9271. (55) Dhakshinamoorthy, A.; Alvaro, M.; Garcia, H. Metal-Organic Frameworks as Efficient Heterogeneous Catalysts for the Regioselective Ring Opening of Epoxides. Chem. - Eur. J. 2010, 16, 8530− 8536. (56) Jiang, D.; Mallat, T.; Krumeich, F.; Baiker, A. Copper-Based Metal-Organic Framework for the Facile Ring-Opening of Epoxides. J. Catal. 2008, 257, 390−395.

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DOI: 10.1021/acsami.6b04127 ACS Appl. Mater. Interfaces 2016, 8, 16457−16464