MetalâOrganic Framework@Microporous Organic Network as

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Metal–Organic Framework@Microporous Organic Network as Adsorbent for Solid-Phase Microextraction Yuqian Jia, Hao Su, Zhenhua Wang, Y.-L. Elaine Wong, Xiangfeng Chen, Minglin Wang, and T.-W. Dominic Chan Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.6b03156 • Publication Date (Web): 16 Sep 2016 Downloaded from http://pubs.acs.org on September 18, 2016

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Analytical Chemistry

Metal–Organic Framework@Microporous Organic Network as Adsorbent for Solid-Phase Microextraction

Yuqian Jia,†# Hao Su,†# Zhenhua Wang,† Y.-L. Elaine Wong,‡ Xiangfeng Chen,*,† Minglin Wang,† T.-W. Dominic Chan**,‡ †

Key Laboratory for Applied Technology of Sophisticated Analytical Instruments,

Shandong Academy of Sciences, Shandong, P. R. China ‡

Department of Chemistry, The Chinese University of Hong Kong, Hong Kong SAR

Address correspondence to: Dr. X.F. Chen, Shandong Academy of Sciences, Jinan, China. E-mail: [email protected]. Professor T.-W. D. Chan, Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China. E-mail: [email protected]. # equal contribution

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Abstract The practical applications of moisture sensitive metal-organic frameworks (MOFs) in the extraction technique are faced with avoided challenges related to competitive adsorption and hydrostability. The target analytes cannot be effectively extracted under humid conditions because of the competitive moisture adsorption and/or framework structure collapse of MOFs. In this Letter, metal–organic framework (MOF)@microporous organic network (MON) hybrid materials were explored for the first time as fiber coatings for solid-phase microextraction (SPME). Microporous materials with hydrophobic surface was formed by coating the MOFs (MIL-101 and MOF-5) with MON through sonogashira coupling reaction. MON acted as a hydrophobic “shield” to hinder the competitive moisture adsorption and improve moisture resistance and stability of the fiber. The sorbent exhibited higher enrichment factors (1215–3805) towards PAHs than other analytes in the water samples. An SPME method using MOF@MON-based fiber was developed to quantitatively determine PAHs. The proposed method was successfully applied to analyze PAHs in environmental water, particulate matter (PM 2.5 ) and food samples. A successful technique is proposed to chemically control MOF for applications in solid-phase sorption-based extraction techniques.

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1. Introduction Solid-phase microextraction (SPME) has been widely applied in environmental,1 food,2 clinical, and biological analysis3,4 since the pioneering work of Pawliszyn and Arthur in the early 1990s.5 This technique integrates sampling and sample pretreatment into one step. This solvent-free process is easy to operate and has high enrichment factors (EFs).6 The extraction ability of SPME is primarily determined by the nature of the sorbent coated on the fiber.7,8 Therefore, novel coating development is a key focus for current research on SPME.9,10 Metal–organic frameworks (MOFs) have drawn special attention in analytical chemistry because of their large surface area and unique chemical properties.11,12 Many types of MOFs,13-22 such as ZIF-8,19 MIL-53,14 and ZIF-90,22 have been explored as sorbent in SPME. Hydrostability of MOFs is critical for their application as fiber coatings in SPME.23 Taking MOF-5 as an example, it has been reported that the water molecule attack would result in the phase transformation and structure collapse of the framework.24 This phenomenon limits the practical application of moisture sensitive MOFs in SPME and pollutant removal under humid conditions. Moreover, the competitive moisture adsorption prior to the adsorption of target analytes would also result in low extraction efficiency.25,26 Microporous organic networks (MONs) are a class of organic molecules formed by sonogashira coupling.27 The chemical tuning of the surface of MOF can be achieved by hybridizing MON with MOF. Coating the MOF with MON forms microporous materials with a hydrophobic surface.28. The MON may hinder the competitive moisture adsorption by repelling water molecules and improve the hydrophobic properties of the fiber. In this Letter, we combined the MON with MOFs to form novel hybrid 3



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microporous nano-materials. Two kinds of MOFs (MOF-5 and MIL-101) with different moisture response properties were selected. Then, the moisture-resistant coatings were successfully applied as sorbent for SPME. 16 polycyclic aromatic hydrocarbons (PAHs) were selected as target analytes to evaluate the performance of fibers. The concentrations of PAHs from environmental water, particulate matter (PM 2.5 ) and food samples were determined using the developed fiber based SPME method. The objective of this Letter is to provide an novel analytical application of MOF@MON hybrid material as sorbent for solid-phase sorption based extraction techniques. 2. Experimental Section 2.1 Synthesis of MOF@MON MOF-5 and MIL-101-NH 2 were used as models of moisture sensitive and moisture resistant MOFs, respectively. The synthetic procedure for the preparation of nano-composite (MIL-101@MON) is shown in Figure 1. MIL-101-NH 2 and MOF-5 were first synthesized, and then sonogashira coupling reaction27 was used to coat the MON on the surface of the MOF. The chemicals, detailed synthetic procedure and characterization of the nano-composites are described in the Supplementary Information. 2.2 SPME procedure The physical adhesive method was adopted in this study to prepare the fiber.14 The water sample (10 mL) was added into a 20 mL glass vial equipped with a Teflon-coated magnetic stirrer bar and covered with a cap. For PM 2.5 and smoked meat samples, the PAHs were firstly ultrasonically extracted by extract phase. Then, the collected extract was evaporated and reconstituted by de-ionized water to form the 4


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solution for SPME. The detailed fiber fabrication and sample preparation procedures are described in the Supplementary Information. 3. Results and discussion Figures 2(a) and (b) showed that MIL-101@MON had rougher micro-surface with fuzzier edges after coating with MON. The TEM image in Figure 2(c) illustrates that the hybrid materials have a dark inner with bright marginal features. A clear hollow structure was observed in Figure 2(d) after the inner MOF was etched with HF. The shape and size of the hollow MON matched the original MOF. Figures 1(e) and (f) revealed that MIL-101(Fe)@MON was coated on the surface of the fiber. The thickness of the coating was approximately 30 μm. Figure 2(g) demonstrates that MIL-101@MON has the desirable structures both of the MOFs and MON. TGA images in Figure 2(h) show that MOF@MON coated fiber had little weight loss from 50°C to 360°C. Although MIL-101-NH 2 is a water stable MOF, the surface is hydrophilic. As shown in the inset in Figure 2(h), the water contact angle of MIL-101 increased to 131°, which indicated that the surface became hydrophobic after coating with MON. The SEM, PXRD and water contact angle images of MOF-5@MON were shown in Figure S-1 and described in the Supplementary Information. The retain of PXRD patterns after water treatment and the increases of water contact angles for MOF-5@MON indicated that the existence of framework and the hydrophobic nature of the surface. The EFs of PAHs using MOF@MON-coated fibers were compared with those of pristine MOF coatings and MON (obtained by chemical etching) coatings. The EFs results of PAHs using these fibers were summarized in Table S-2. The MOF@MON based fibers gave generally higher EFs than those of two pristine MOFs, which 5



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demonstrated that modification obviously improved the extraction performance. Poor extraction performance of MOF-5 fiber should be caused by the collapse of the framework, which is in accordance with changes of PXRD patterns of MOF-5 before and after water treatment (Figure S-1c).24 The EFs for PAHs obtained by using MON as coating were lower than MOF@MON, indicating that the inner MOF should also make a major contribution to the enrichment. These results demonstrate that both the MON and inner MOF play important role in the adsorption process. The contribution of glue to the EFs was excluded by direct SPME with glue coated fiber. The improvement of extraction performance using MON@MOF as the fiber coating can be rationalized by considering the structural characteristics of the sorbent. (i) The MON coating acted as a hydrophobic shield to hinder competitive moisture adsorption and improve the moisture resistance of the fiber. (ii) Strong π–π interaction and hydrophobic interactions between the PAHs and benzene ring structural moiety of MON enhanced the PAHs affinity of the hybrid material. The EFs of PAHs obtained using MOF-5@MON are smaller than that of MIL-101@MON. This difference was tentatively attributed to the small pore size of MOF-5@MON as compared with that of MIL-101(Fe) (Figure S-2). Therefore, MIL-101@MON based fiber was used for the following experiment. The selectivity of the developed sorbent was tested using PAHs along with phenol, n-hexane, n-dodecane, chloroform, n-octanol, and butanol as analytes. As shown in Table S-3, the hydrophilic analytes, such as phenol, n-octanol, and butanol, could not be effectively extracted by the fiber. The EFs for the hydrophobic analytes were positively correlated with the hydrophobicity of the analytes, except n-hexane and n-dodecane.29-31 The EFs of n-hexane and n-dodecane were much smaller than that of Nap although their log K ow values were higher than that of Nap. This behavior 6


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indicated that the presence of π-electron in the analytes also played an important role in the determining the selectivity of the fiber. The analytical parameters for 16 PAHs using the proposed method are listed in Table S-4. The linear ranges were from 0.1 ng L−1 to 500 ng L−1, and the correlation coefficients (R2) were between 0.9887 and 0.9996. The limits of detection (S/N=3) and limits of quantification (S/N=10) ranged from 0.03 ng L−1 to 0.30 ng L−1 and from 0.10 ng L−1 to 1.25 ng L−1, respectively. The relative standard deviations (RSDs) for the six replicate tests using a single fiber ranged from 4.6% to 8.4%. The fiber to fiber reproducibility for three parallel fibers ranged from 6.5% to 8.7%. The comparative results of the developed methods with previous reported methods are listed in Table S-5.13-15,32-37 It can be found that the proposed method using MOF@MON based fiber exhibit low LODs, short extraction time and high enrichment factors compared with the other sorbent based methods. In addition, the fiber could be reused for more than 60 times without observable decrease in the extraction performance. The proposed method was applied to determine PAHs in food and environmental samples. Figure 3 shows the typical extracted chromatogram of 16 PAHs of waste water samples detected by the developed method. As shown in Table S-6, the PAHs concentrations in water samples ranged from 0.5 ng L−1 to 9.2 ng L−1. Three samples were used to test the applicability of the developed method for PAHs determination in PM 2.5 . The recoveries for spiked water, PM 2.5 and smoked meat samples ranged from 71.2% to 109.7% (Table S-6 and 7). As shown in Table S-8, the total PAHs concentration in sample 1 (5th April 2015) was 645.9 ng m−3. The high PAHs concentration was attributed to the severe haze on the sampling day. The diagnostic ratios of Flu/(Flu+Phe) were lower than 0.50, which indicated that the source of PAHs was gasoline and diesel engine.38-40 The PAHs concentration in sample 2 (collected on 7



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11th April 2015, severe haze dissipated) decreased to 183.5 ng m−3. The total concentration of PAHs in sample 3 (23th Aug 2015) was 77.9 ng m−3, which was lower than the average value in Jinan. These results demonstrated that the control of traffic and industrial activities for the opening of the 22nd International Congress of Historical Science in Jinan effectively decreased the emission of PAHs and improved air quality. As shown in Table S-8, the concentration of PAHs detected in smoked meat samples ranged from 0.25 μg kg−1 to 18.6 μg kg−1. The sum of PAHs in beef, pork, and lamb samples of PAHs were 75.5, 84.4, and 96.1 μg kg−1. These results are in accordance with PAHs formation during grilling, which was dependent on the fat content of the meat, cooking time, and temperature. 4.

Conclusion In this Letter, we reported the synthesis and application of MOF@MON as fiber

coatings for SPME. The moisture-resistant MON shell could repel water molecules and enhanced the hydrophobic properties of MOFs, thereby improving the extraction performance of SPME. This study has demonstrated the utility of MOF@MON hybrid material in solid-phase sorption-based extraction techniques through chemical control. Acknowledgements Financial supports from the National Natural Science Foundation of China (21277084, 21205071, 21477068), Natural Science Foundation of Shandong Province (ZR2012BQ009) and Funds for Fostering Distinguished Young Scholar and Fundamental Research Funds of Shandong Academy of Sciences are gratefully acknowledged. Supporting Information 8


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sample

collection

and

preparation;

fiber

fabrication;

instrumentation;

optimization of extraction parameters; SPME procedures References (1) Souza-Silva, E. A.; Jiang, R.; Rodriguez-Lafuente, A.; Gionfriddo, E.; Pawliszyn, J. Trends Anal. Chem. 2015, 71, 224-235. (2) Souza-Silva, E. A.; Gionfriddo, E.; Pawliszyn, J. TrAC Anal. Chem. 2015, 71, 236-248. (3) Souza-Silva, E. A.; Reyes-Garces, N.; Gomez-Rios, G. A.; Boyaci, E.; Bojko, B.; Pawliszyn, J. Trends Anal. Chem. 2015, 71, 249-264. (4) Spietelun, A.; Kloskowski, A.; Chrzanowski, W.; Namiesnik, J. Chem. Rev. 2013, 113, 1667-1685. (5) Arthur, C. L.; Pawliszyn, J. Anal. Chem. 1990, 62, 2145-2148. (6) Ouyang, G.; Vuckovic, D.; Pawliszyn, J. Chem. Rev. 2011, 111, 2784-2814. (7) Xu, J.; Zheng, J.; Tian, J.; Zhu, F.; Zeng, F.; Su, C.; Ouyang, G. Trends Anal. Chem. 2013, 47, 68-83. (8) Silva, E. A. S.; Risticevic, S.; Pawliszyn, J. Trends Anal. Chem. 2013, 43, 24-36. (9) Zhang, S.; Du, Z.; Li, G. Anal. Chem. 2011, 83, 7531-7541. (10) Liu, Q.; Shi, J.; Jiang, G. Trends Anal. Chem. 2012, 37, 1-11. (11) Furukawa, H.; Ko, N.; Go, B.; Aratani, N.; Choi, B.; Choi, E.; Yazaydin, O.; Snurr, Q.; O’Keeffe, M.; Kim, J.; Yaghi, M. Science 2010, 329, 424-428. (12) Gu, Z.-Y.; Yang, C.-X.; Chang, N.; Yan, X.-P. Acc. Chem. Res. 2012, 45, 734−745. (13) Wan, G. H.; Lei, Y. Q.; Song, H. C. Talanta. 2015, 144, 369–374. (14) Chen, X. F.; Zang, H.; Wang, X.; Cheng, J. G.; Zhao, R. S.; Cheng, C. G.; Lu, X. Q. Analyst. 2012, 137, 5411–5419. (15) Xie, L. J.; Liu, S. Q.; Han, Z. B.; Jiang, R. F.; Liu, H.; Zhu, F.; Zeng, F.; Su, C. Y.; Ouyang, G. F. Anal. Chim. Acta. 2015, 853, 303–310. (16) Cui, X. Y.; Gu, Z. Y.; Jiang, D. Q.; Li, Y.; Wang, H. F.; Yan, X.-P. Anal. Chem. 2009, 81, 9771-9777. (17) He, C.-T.; Tian, J.-Y.; Liu, S.-Y.; Ouyang, G.; Zhang, J.-P.; Chen, X.-M. Chem. Sci. 2013, 4, 351-356. (18) Li, Y.-A.; Yang, F.; Liu, Z.-C.; Liu, Q.-K.; Dong, Y.-B. J. Mater. Chem. A 2014, 2, 13868-13872. (19) Chang, N.; Gu, Z.-Y.; Wang, H.-F.; Yan, X.-P. Anal. Chem. 2011, 83, 7094-7101. (20) Shang, H.-B.; Yang, C.-X.; Yan, X.-P. J. Chromatogr. A 2014, 1357, 165-171. (21) Wu, Y.-Y.; Yang, C.-X.; Yan, X.-P. J. Chromatogr. A 2014, 1334, 1-8. (22) Yu, L.-Q.; Yan, X.-P. Chem. Commun. 2013, 49, 2142-2144. (23) Zhang, Z.; Huang, Y.; Ding, W.; Li, G. Anal. Chem. 2014, 86, 3553-3540. (24) Li, H.; Shi, W.; Zhao, K.; Li, H.; Bing, Y.; Cheng, P. Inorg. Chem. 2012, 51, 9200-9207. (25) Castillo, J. M.; Vlugt, T. J. H.; Calero, S. J. Phys. Chem. C. 2008, 112, 9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

15934−15939. (26) Supronowicz, B.; Mavrandonakis, A.; Heine, T. J. Phys. Chem. C. 2013, 117, 14570−14578. (27) Sonogashira, K. J. Organomet. Chem. 2002, 653, 46–49. (28) Chun, J.; Kang, S.; Park, N. J.; Park, E. J.; Jin, X.; Kim, K. D.; Seo, H. O.; Lee, S. M.; Kim, H. J.; Kwon, W. H.; Park, Y. K.; Kim, J. M. J. Am. Chem. Soc. 2014, 136, 6786−6789. (29) Ryu, S. A.; Park, S. J. Fluid Phase Equilib. 1999, 161, 259-304. (30) Xu, H. L.; Li, Y.; Jiang, D. Q.; Yan, X.-P. Anal. Chem. 2009, 81, 4971–4977. (31) Ma, Y. G.; Lei, Y. D.; Xiao, H.; Wania, F.; Wang, W. H. J. Chem. Eng. Data. 2010, 55, 819–825. (32) King, A. J.; Readman, J. W.; Zhou, J. L. Anal. Chim. Acta. 2004, 523, 259–267. (33) Martin, D.; Ruiz, J. Talanta. 2007, 71, 751–757. (34) Fan, J.; Dong, Z.; Qi, M.; Fu, R.; Qu, L. J. Chromatogr. A. 2013, 1320 , 27–32. (35) Zhang, G. J.; Zang, X. H.; Li, Z.; Wang, C.; Wang, Z. Talanta. 2014, 129, 600–605. (36) Li, Q.-L.; Wang, X.; Chen, X.-F.; Wang, M.-L.; Zhao, R.-S. J. Chromatogr. A. 2015, 1415 , 11–19. (37) Zhang, S.; Li, Z.; Yang, X.; Wang, C.; Wang, Z. Rsc. Adv. 2015, 5, 54329-54337. (38) Li, Y.; Shao, M.; Lu, S.; Chang, C.; Dasgupta, P.K. Atmos. Environ. 2010, 44, 632–2639. (39) Gu, Z.; Feng, J.; Han, W.; Li, L.; Wu, M.; Fu, J.; Sheng, G. China Environ. Sci. 2010, 3, 389–396. (40) Ravindra, K.; Sokhi, R.; Grieken, R.V. Atmos. Environ. 2008, 42, 2895–2921.

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Figure 1 Synthesis of MOF@MON and fabrication of solid-phase microextraction fibers

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Figure 2 Scanning electron micrographs of (a) MIL-101 (Fe) and (b) MIL-101 (Fe)@ microporous organic network (MON); transmission electron micrographs of (c) MIL-101 (Fe)@MON and (d) MON; scanning electron micrographs of (e) SPME fiber and (f) fiber coating; (g) powder X-ray diffraction spectra of MIL-101 (Fe)@MON; (h) thermogravimetric curve of MIL-101 (Fe) and MIL-101 (Fe)@MON fibers

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Figure 3 Typical extracted chromatogram of 16 PAHs of the water samples obtained by the developed method: waste water spiked at (a) 0, (b) 5, (c) 50, and (d) 100 ng L−1

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