Hybridization of Metal Nanoparticles with MetalâOrganic Frameworks

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Hybridization of metal nanoparticles with metal-organic frameworks using protein as amphiphilic stabilizer Hui Mao, Weina Zhang, Weiqiang Zhou, Binghua Zou, Bing Zheng, Shilin Zhao, and Fengwei Huo ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b06754 • Publication Date (Web): 10 Jul 2017 Downloaded from http://pubs.acs.org on July 11, 2017

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ACS Applied Materials & Interfaces

Hybridization of metal nanoparticles with metal-organic frameworks using protein as amphiphilic stabilizer Hui Mao*b, Weina Zhanga, Weiqiang Zhoua, Binghua Zoua, Bing Zhenga, Shilin Zhaob and Fengwei Huo*a a

Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for

Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816, P.R. China. Email: [email protected] b

College of Chemistry and Materials Science, The Engineering Center for the Development of

Farmland Ecosystem Service Function, Sichuan Normal University, Chengdu 610068, P. R. China. Email: [email protected] KEYWORDS: nanoparticles, metal-organic frameworks, protein, amphiphilic, catalysts.

ACS Paragon Plus Environment 1


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ABSTRACT

Here, a facile strategy is reported to efficiently hybridize metal nanoparticles (MNPs) with typical metal-organic frameworks (MOFs) of ZIF-8 (zeolitic imidazolate framework-8), which employs bovine serum albumin (BSA, a serum albumin protein derived from cows) as the amphiphilic stabilizer to increasing the affinity of MNP towards MOFs. For instance, the as-synthesized PdNPs/ZIF-8 composites with diameter from 100 to 200 nm always maintain well-define crystalline structure, and the PdNPs with small size of ~2 nm are well dispersed in the crystal of MOFs without serious aggregations due to the BSA stabilizer. In Suzuki cross-coupling reactions of aryl halide, the PdNPs/ZIF-8 as catalysts have exhibited high activity and satisfied reusability owing to the use of BSA stabilizer as well as the fixing of MOFs matrixes. In addition, the strategy also can be extended to synthesize other kinds of MNPs/MOFs hybrid composites with tunable particle size, which brings the more opportunity for functional MOFs hybrid materials. INTRODUCTION Metal-organic frameworks (MOFs)1,2 synthesized by self-assembly of metal ions coordinated with organic ligands have garnered great interests in gas storage,3,4 battery,5 sensor technologies,6,7 and catalysis8-10 owing to their distinct properties, such as large internal surface area, tunable cavities and adjustable porosity. Especially, the use of MOFs to prepare heterogeneous catalysts has been intensively investigated.11,12 Over the past decades, various types of heterogeneous catalysts have been successfully prepared by loading metal nanoparticles (MNPs) on different MOFs matrixes via various methods.13-15 These researches mostly focused on the utilization of crystalline porous frameworks of MOFs to control the size of MNPs as well


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as restrain the migration and aggregation of MNPs. So far, progressive achievements have been made by supporting monometallic and bimetallic MNPs on MOFs.16,17 However, the MNPs supported on MOFs as catalysts still suffer from activity loss during the reaction cycles. Similar like other heterogeneous catalysts, the MNPs supported on the outer surface of MOFs may suffer from particle diffusion or falling off from the MOFs host during catalytic reactions, inevitably leading to poor cycling stability. For example, PdNPs supported on MIL-101(Cr) as catalysts exhibited poor reusability in the cycle reaction of phenol hydrogenation. The phenol conversion was decreased from ~90 % to ~75 % after three cycles.17 Thus, it is desired to fabricate highly-stable MNPs/MOFs hybrid composites to improve their reusability in the field of heterogeneous catalysis. Although some pioneer works have been carried out by embedding MNPs into MOFs,18 new preparation approaches of incorporating MNPs within MOFs with good stability are still attractive. To achieve this goal, one possible resolution is to introduce the MNPs modified with stabilizers into the MOFs growing solutions. Previous investigations demonstrated that amphiphilic stabilizers, especially some amphiphilic polymers, can facilitate the encapsulation of MNPs inside MOFs by increasing the affinity of MNPs towards MOFs.2,19 The amphiphilic nature of these polymers serves as a general surfactant to stabilize various nanoparticles in kinds of polar solvents.20,21 The investigation to these amphiphilic stabilizers exclusively focus on the organic polymer (Polyvinyl Pyrrolidone, PVP) while less attention has been paid to other stabilizers, especially nature macromolecules, such as proteins. Actually, proteins are ideal candidate stabilizers for the hybridization of MNPs in MOFs. These proteins contain abundant functional groups (-OH, -COOH, and -CO-NH-) in their molecule structure, which is proved to have high affinity towards metal species.22,23 In literatures, various MNPs have been successfully



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prepared by using proteins as the stabilizers, including AuNPs, AgNPs and PdNPs, etc.24-26 Moreover, the size of these MNPs can be conveniently controlled by change the ratio of metal precursors and proteins. In addition, proteins are featured with amphiphilic properties,27 which is the key factor for the protein-stabilized MNPs to absorb onto continuously growing MOF crystals. Consequently, it is possible to rationally control the morphology and spatial distribution of MNPs within the MOFs matrixes by employing proteins as stabilizers of MNPs. Herein, we report an efficient strategy for hybridization of MNPs with MOFs, which employs bovine serum albumin (BSA, a serum albumin protein derived from cows) as the amphiphilic stabilizer. As a typical protein, BSA has extremely high affinity to metal species, which is very suitable and convenient for stabilization of diverse MNPs. Hence, we employed BSA as the amphiphilic stabilizer. The as-prepared MNPs/MOFs catalysts exhibited well crystal structure of the ZIF-8 as well as the high porosity. The PdNPs/ZIF-8 exhibited superior cycling stability in Suzuki reaction compared with the catalysts prepared by conventional supported heterogeneous catalysts. In addition, we also extended our method to the synthesis of AuNPs/MOFs hybrid composites, which the size and distribution of AuNPs can be rationally controlled.

EXPERIMENTAL SECTION General information. All of the chemicals are purchased from Sigma/Aldrich and used as received. Scanning electron microscope (SEM) images were carried out by JEOL JSM-7600. Transmission electron microscope (TEM) images were taken by JEOL JEM 2010F. Power X-ray diffraction (XRD) patterns were characterized with a Bruker AXS D8 Advance diffractometer using nickel-filtered Cu Kα radiation (λ = 1.5406 Å). The BET surface area was performed in


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Micromeritics ASAP 2020 adsorption apparatus at 77 K up to 1 bar. The UV-vis characterization was taken at Shimadzu UV-2501PC. Synthesis of BSA-AuNPs and BSA-PdNPs. 1 mL of BSA aqueous solution (50 mg of BSA) was diluted with 2.8 mL of deionized water, then 0.2 mL of HAlCl4 (100 µmol Au3+) aqueous solution was added into the diluted solution. The mixed solution was stirred for half an hour at room temperature and 1 mL of NaOH aqueous solution was added into the mixture. After half an hour, the 5 mL of BSA-AuNPs colloid was obtained with red fluorescence under ultra violet light with λ = 365 nm. 1 mL of PdCl2 aqueous solution (100 µmol Pd2+) was added into 3.8 mL of BSA aqueous solution (50 mg of BSA). The mixed solution was stirred for half an hour at room temperature and 0.2 mL of NaBH4 aqueous solution was added into the mixture, then the BSA-PdNPs was synthesized. Synthesis of AuNPs/ZIF-8, PdNPs/ZIF-8, PdNPs/ZIF-8* and PdNPs/ZIF-8**. 1 mL of 2-methylimidazole (250 µmol) aqueous solution was mixed with 0.5 mL of BSA-AuNPs solution. The mixture was stirred for 5 min at room temperature, then Zn(NO3)2 solution which contained 250 µmol Zn2+ was added into the mixture. Subsequently, the mixture was centrifuged and fully washed with deionized water. The as-prepared AuNPs/ZIF-8 sample was dried at 60 oC for 24 h in vacuum oven. The AuNPs/ZIF-8 sample which encapsulated AuNPs with particle size of ~20 nm was put into the 2-methylimidazole aqueous solution for 24 h. The PdNPs/ZIF-8 was synthesized in the same approach. Based on ICP measurements, the content of PdNPs and AuNPs in PdNPs/ZIF-8 and AuNPs/ZIF-8 were determined to be 6.3 wt% and 10.87 wt%, respectively. The PdNPs/ZIF-8* was prepared by loading 0.5 mL of BSA-PdNPs (10 µmol Pd) solution onto synthesized 5 mg of ZIF-8 powders and dried in vacuum. The PdNPs/ZIF-8** was prepared by impregnating 10 µmol of Pd2+ on ZIF-8, followed by reduction using NaBH4.



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Typical procedure for Suzuki reaction. Iodobenzene (0.5 mmol), phenylboronic acid (0.75 mmol), base (1.5 mmol) and PdNPs/ZIF-8 catalysts (Pd 10 µmol) were added to the mixture of 4 mL of H2O and 2 mL of ethanol. The reaction mixture was stirred at the desired temperature under N2 atmosphere. After reaction, the catalyst was centrifuged and fully washed with deionized water, then dried in a vacuum oven for reusing. The solution was washed with brine and diethyl ether. The organic phase was subsequently extracted with diethyl ether, dried over MgSO4. The product was quantified by GC-MS analysis. Typical procedure for hydrogenation of styrene. Styrene (5 mmol) and PdNPs/ZIF-8 (Pd 10 µmol) were added into 10 mL of ethanol. The hydrogenation reaction was carried out in a Parr reactor equipped with mechanical stirring. Pressure the reactor to 2 MPa with hydrogen and vent for 3 times. Then keep the pressure of 2 MPa and begin stirring at desired temperature. After reaction, the mixture was centrifuged and the organic phase was quantified by GC.

RESULTS AND DISCUSSION The BSA-stabilized MNPs with controlled size were hybridized with MOFs (Figure 1) via employing protein as stabilizer to enhance the affinity of MNPs towards MOFs as well as ingenious encapsulation strategy. Here, the zeolitic imidazolate framework material-8 (ZIF-8) and palladium nanoparticles (PdNPs) were taken as an example to study the hybridization strategy. The BSA-stabilized PdNPs (denoted as BSA-PdNPs) colloid solutions were obtained by reduction of Pd2+ with NaBH428,29 as well as utilization of BSA as the stabilizer. The BSA-PdNPs with spherical morphology have an average diameter of 2 ± 0.5 nm (Figure S1). The Zn2+ solution was added into the aqueous mixture of BSA-MNPs and 2-methylimidazole


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(2-MI). This allowed the Zn2+ coordinating with 2-MI by accepting the electrons donated from the N atom of 2-MI, giving rise to building-block of MOFs. Notably, the BSA-PdNPs would be absorbed on the growing ZIF-8 sphere because the amphiphilic BSA stabilized on the surface of PdNPs (or AuNPs) strengthened the interactions between the metal NPs and the ZIF-8 crystalline. Meanwhile, the high affinity of BSA to Zn2+ also induced the growth of ZIF-8 micro-crystal on the surface of MNPs.30 Finally, the PdNPs were stably hybridized with the ZIF-8 matrixes until the growth of MOFs was completed. The framework of ZIF-8 still characterized by sodalite-type cages accessible via two types of windows (a four-membered ring and a six-membered ring), although the surfactant-like properties of BSA may influence the self-assembly of ZIF-8 to form perfect crystals. The size and morphology of the as-synthesized PdNPs/ZIF-8 were investigated by field-emission scanning electron microscopy (FESEM). As shown in Figure 2a, the PdNPs/ZIF-8 composites have good uniformity with diameter from 100 nm to 200 nm, which preserves well the typical morphology of ZIF-8 crystals with typical rhombic dodecahedron (RD) shape with 12 exposed {110} faces. The magnified FESEM images in Figure 2b show an individual PdNPs/ZIF-8 particle. These differences in morphology reveal that the amphiphilic nature of BSA indeed influences the crystallization of ZIF-8 in self-assembling to form perfect crystals. However, no obvious change was found on the X-ray diffraction (XRD) patterns of PdNPs/ZIF-8 and pure ZIF-8 (Figure S2). All the diffraction peaks of the PdNPs/ZIF-8 in the 2θ range of 10-50o match well with pure ZIF-8, indicating the PdNPs/ZIF-8 composites with well-defined crystal structure. In addition, no diffraction peaks are indexed to metallic PdNPs species, probably due to the low content of PdNPs.31



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Figure 1. The preparation approach of MNPs/ZIF-8 (M = Pd and Au).

Actually, the following TEM observations confirm the formation of small PdNPs within the ZIF-8. Based on N2 adsorption/desorption analysis (Figure S3), the PdNPs/ZIF-8 is still featured with high specific surface area (1010 m2 g-1), demonstrating its highly porous characteristics. Compared with pure ZIF-8 (1249 m2 g-1), the specific surface area of PdNPs/ZIF-8 is relatively low, as expected due to the contribution of nonporous BSA-PdNPs to the masses of ZIF-8 composites. The PdNPs with size of ~2 nm are well dispersed within the MOFs matrixes, and no obvious aggregations of these MNPs are observed (Figure 2c-e and Figure S4). The size and morphology of PdNPs have no obvious change compared with BSA-PdNPs. The characteristic peak of BSA can still be observed in the FTIR spectrum of PdNPs/ZIF-8 (Figure S5), which confirms the presence of the BSA in the PdNPs/ZIF-8. We also investigated the influence of mixing conditions of precursors on the morphology and distribution of PdNPs in the MOFs. As


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shown in Figure S6, the BSA-PdNPs mainly self-aggregated to form supramolecular structures rather than hybridized with MOFs if the BSA-PdNPs were first mixed with Zn2+ in aqueous solution, followed by the addition of 2-methylimidazole ligands. The main reason for these results could be the salting out effect of Zn(NO3)2 to BSA. Moreover, the use of organic solvent (such as methanol) as reaction media also failed to incorporate the NPs with ZIF8 due to the precipitation effect of organic solvent to BSA (Figure S7). We also prepared PdNPs/ZIF-8** by impregnation method without the use of BSA. As shown in Figure S8, the PdNPs are mainly located on the surface of ZIF-8, and the aggregation of PdNPs is quite evident due to the absence of BSA. These results manifest the essential role of BSA as amphiphilic stabilizer for encapsulating PdNPs into ZIF-8.

Figure 2. (a-b) SEM images and (c-e) TEM images of PdNPs/ZIF-8. The inset in (a) shows the photos of ZIF-8 (left) and PdNPs/ZIF-8 (right).

Suzuki cross-coupling reactions of aryl halide are very important to constructing biaryl compounds in organic synthesis as versatile routes.32-34 Suzuki reactions catalyzed by



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heterogeneous Pd catalysts are more attractive compare to that catalyzed by homogeneous catalysts due to their easy recovery and good reusability.35,36 Herein, iodobenzene was employed as the substrate to calculate the catalytic activity of PdNPs/ZIF-8 catalyst in the Suzuki reaction (Table 1). The nature of the base is crucial in this reaction,37 and thus, three kinds of bases were utilized in the reaction. The reaction was first carried out without any base at 80 oC. No product was detected after 6 h. The Na2CO3, K2CO3 and NaOH were used as base in the reaction respectively, the yield of biphenyl is gradually increased at reaction time of 6 h under the same reaction condition.

Higher yield was observed with a prolonged reaction time of 20 h by using

the NaOH as base. In addition to the additive of base, the atmosphere also played a crucial role in the Suzuki cross-coupling reaction.38 The coupling reaction of iodobenzene with phenylboronic acid performed in air exhibited lower yield than the reaction performed under a nitrogen atmosphere. The yield of biphenyl was almost twice in the nitrogen compared to that in the air. According to the literature,39,40 the molecular oxygen dissolved in the water/EtOH solvent often lead to oxidation of phenylboronic acid, which would form phenol instead of biphenyl. The effect of molecule size to the catalytic activity was also investigated. Under the same experimental conditions, the 2-iodoanisde and 4-iodoanisde both exhibited much lower yield for the Suzuki coupling reaction, which delivered the corresponding product yield of 12.5 % and 18.7 %, respectively (Table 2). Without the substituent, the iodobenzene exhibited a product yield of 24.8 %. These differences in catalytic activity could be attributed to the deactivation and steric hindrance, derived from the synergy effect of ZIF-8 framework and the active PdNPs. Subsequently, the reusability of PdNPs/ZIF-8 catalyst was conducted under 80 oC in the nitrogen atmosphere. As shown in Table S1, the PdNPs/ZIF-8 has exhibited a satisfied reusability in 5 cycles. The catalyst can be easily recovered and reused in the Suzuki reaction for


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five times without significant loss of efficiency. In the 5th cycle, the yield of biphenyl product can still reach 21.6 % (1st cycle, 24.8 %). TEM observations suggest that the PdNPs in the PdNPs/ZIF-8 catalyst were still highly dispersed in ZIF-8, and the crystalline structure of ZIF-8 was also intact after five cycles (Figure S9). No aggregating and leaching of PdNPs were observed due to the efficient stabilization of the ZIF-8. These results confirm the high stability of the catalyst. We applied BSA-PdNPs as catalysts in Suzuki cross-coupling reactions of iodobenzene with phenylboronic acid. Although the yield of biphenyl is >99 % under the same condition, it is impossible for the catalyst to separate from the reaction system for further recycles.

Table 1. Catalytic activity of PdNPs/ZIF-8 in Suzuki cross-coupling reactions of iodobenzene with phenylboronic acid.

Entry

Base

Atmosphere

Time (h)

Yield (%)

1

K2CO3

air

6

2.1

2

K2CO3

N2

6

4.1

3

Na2CO3

air

6

1.7

4

Na2CO3

N2

6

3.2



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5

NaOH

air

6

10.6

6

NaOH

N2

6

24.8

7

NaOH

N2

20

40.7

8a

NaOH

N2

20

77.3

Conditions: iodobenzene 0.5 mmol, phenylboronic acid 0.75 mmol, Base 1.5 mmol, water 4 mL, EtOH 2 mL, 80 oC, 10 µmol Pd. a Catalyzed by PdNPs/ZIF-8*.

Furthermore, BSA-PdNPs were also directly supported on the pre-synthesized ZIF-8 by conventional impregnation method to prepare heterogeneous PdNPs/ZIF-8* catalyst. We found that the PdNPs/ZIF-8* catalyst exhibited higher activity than PdNPs/ZIF-8 catalyst under the same reaction conditions in Suzuki reaction, as shown in Table S1. This may be due to the fact that most of PdNPs were located on the outer surface of ZIF-8 in the PdNPs/ZIF-8* catalyst. The substrate molecular of iodobenzene and phenylboronic acid could react with each other easily, resulting a higher yield of biphenyl. In the reaction catalyzed by PdNPs/ZIF-8, the PdNPs were stably incorporated within the ZIF-8 frameworks. Thus, the PdNPs/ZIF-8 should exhibit slower reaction kinetics compared with PdNPs/ZIF-8*. However, the PdNPs/ZIF-8* catalyst suffered a serious loss of activity during the cycles. The yield of biphenyl has decreased dramatically in the following two cycles when to reuse the PdNPs/ZIF-8* catalyst. In the 4th cycle, there is no biphenyl detected under the same experimental conditions. Indeed, the reusability of PdNPs/ZIF-8 was significantly enhanced compared to PdNPs/ZIF-8*. In addition, the reusability of PdNPs/ZIF-8 was further investigated in hydrogenation of styrene. As shown in Table S1, the


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catalyst could still be reused five times without any significant loss of activity, even under the conditions of 80 oC and of 2 MPa H2. In this case, our encapsulation strategy not only increases the stability of MNPs on the MOFs, but also enhances the cycling stability of the catalysts. Additionally, our method can be extended for the synthesis of other MNPs-based hybrid composites. AuNPs were first prepared by the reduction of Au3+ with BSA (Figure 3 and Figure S10). Subsequently, the AuNPs/ZIF-8 was prepared by the similar procedures adopted for the synthesis of PdNPs/ZIF-8. As show in Figure 3, the AuNPs/ZIF-8 has rough surface owing to the presence of BSA influenced the growth of ZIF-8. The AuNPs show good dispersion within the AuNPs/ZIF-8 crystals, which still keeps the diameter of ~2.0 nm, close to the pre-synthesized BSA-AuNPs (Figure S10). Both the solution and dried powder of AuNPs/ZIF-8 can give fluorescence emission under 365 nm ultraviolet light, and the fluorescence emission spectra of BSA-AuNPs and AuNPs/ZIF-8 both show similar peaks (Figure S11). The XRD pattern of ZIF-8 is still maintained after the hybridization with AuNPs (Figure S2). The BET specific surface area of AuNPs/ZIF-8 is still as high as 913 m2 g-1 (Figure S12). It should be noted that large AuNPs with particle size of ~20 nm can even be entrapped inside ZIF-8 by using BSA as the stabilizer. To obtain the large size AuNPs, we mixed BSA with Au3+ precursors together, and then standing the mixture for 4 weeks. Then the resultant samples were mixed with 2-methylimidazole, followed by the addition of Zn2+, which allows the encapsulation of ~20 nm AuNPs. After that, the AuNPs/ZIF-8 was put in methanol solvent for further growth of the ZIF-8 crystal. As shown in Figure S13, the AuNPs with diameter of 20 nm can be partially entrapped inside ZIF-8 crystals.



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Table 2. Catalytic activity of PdNPs/ZIF-8 in Suzuki cross-coupling reactions of aryl iodine with phenylboronic acid.

Entr

Aryl Product

y

Yield (%)

iodine

1

24.8

2

18.7

3

12.5

Conditions: aryl iodine 0.5 mmol, phenylboronic acid 0.75 mmol, NaOH 1.5 mmol, water 4 mL, EtOH 2 mL, 80 oC, N2 atmosphere, PdNPs/ZIF-8 containing 10 µmol Pd.


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Figure 3. (a) SEM images and (b-d) TEM images and (e-h) photos of AuNPs/ZIF-8. Photographs were taken with ambient light (e) and 365 nm ultraviolet light (f-h). CONCLUSION AND OUTLOOK In conclusion, the BSA can be used as amphiphilic stabilizer to incorporate PdNPs and AuNPs with ZIF-8 framework. The resultant materials well retained the crystalline structure of the ZIF-8 as well as the high porosity. The PdNPs/ZIF-8 exhibited superior cycling stability in Suzuki reaction compared with the catalysts prepared by conventional supported heterogeneous catalysts. The encouraging findings might open up a new avenue in hybridizing various metal NPs with MOFs by modification the NPs with other amphiphilic biopolymers. Furthermore, the noble metal NPs hybridized with MOFs might bring new opportunities in the development heterogeneous catalyst with high reusability in C-C coupling and hydrogenation reactions.

Supporting Information. TEM images, XRD patterns, SEM images, FTIR spectra, N2 adsorption-desorption measurements and catalytic data.

AUTHOR INFORMATION Corresponding Author Prof. Fengwei Huo, Email: [email protected] Prof. Hui Mao, Email: [email protected] Notes The authors declare no competing financial interest.



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Funding Sources The project was supported by the National Science Foundation for Distinguished Young Scholars (21625401), the National Natural Science Foundation (21574065, 21604038), the Jiangsu Provincial Founds for Distinguished Young Scholars (BK20140044), the Program for Outstanding Young Scholars from the Organization Department of the CPC Central Committee, and the National Key Basic Research Program of China (2015CB932200). REFERENCES (1) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Reticular Synthesis and the Design of New Materials. Nature 2003, 423, 705-714. (2) Zhu, Q. L.; Xu, Q. Metal–Organic Framework Composites. Chem. Soc. Rev. 2014, 43, 5468-5512. (3) Fernandez, M.; Boyd, P. G.; Daff, T. D.; Aghaji, M. Z.; Woo, T. K. Rapid and Accurate Machine Learning Recognition of High Performing Metal Organic Frameworks for CO2 Capture. J. Phys. Chem. Lett. 2014, 5, 3056-3060. (4) Sumida, K.; Rogow, D. L.; Chem, J.; Mason, A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T. H.; Long, J. R. Carbon Dioxide Capture in Metal–Organic Frameworks. Chem. Rev. 2012, 112, 724-781. (5) Zhang, L.; Wu, H. B.; Lou, X. W. Metal–Organic-Frameworks-Derived General Formation of Hollow Structures with High Complexity. J. Am. Chem. Soc. 2013, 135, 10664-10672. (6) Lu, G.; Hupp, J. T. Metal−Organic Frameworks as Sensors: a ZIF-8 based Fabry-Pérot Device as a Selective Sensor for Chemical Vapors and Gases. J. Am. Chem. Soc. 2010, 132, 7832-7833.


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Martin,

R.;

Buchwald,

S.

L.

Palladium-Catalyzed

Suzuki−Miyaura

Cross-Coupling Reactions Employing Dialkylbiaryl Phosphine Ligands. Acc. Chem. Res. 2008, 41, 1461-1473. (36) Herrmann, W. A.; Ofele, K.; Schneider, S. K.; Herdtweck, E.; Hoffmann, S. D. A Carbocyclic Carbene as an Efficient Catalyst Ligand for C=C Coupling Reactions. Angew. Chem. Int. Ed. 2006, 45, 3859-3862. (37)

Amatore,

C.;

Transmetalation/Reductive

Jutand,

A.;

Elimination

Le Duc, in

G.

Kinetic

Palladium-Catalyzed

Data

for

the

Suzuki–Miyaura


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Table of Contents We successfully hybridized Pd and Au nanoparticles in zeolitic imidazolate framework-8 (ZIF-8) by using bovine serum albumin (BSA) as the amphiphilic stabilizer of metal nanoparticles, which promoted the affinity of metal nanoparticle towards the ZIF-8 framework. The resultant materials well retained the crystalline structure of the ZIF-8 as well as the high specific surface area.


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