DOI: 10.1021/cg1004352
Efficient Detection of Organophosphate Pesticide Based on a Metal-Organic Framework Derived from Biphenyltetracarboxylic Acid
2010, Vol. 10 2835–2838
Li-Li Wen,*,†,‡ Feng Wang,† Xiao-Ke Leng,† Cheng-Gang Wang,† Lian-Yi Wang,† Jing-Ming Gong,*,† and Dong-Feng Li*,†,‡ †
Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, P. R. China, and ‡Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China Received April 1, 2010; Revised Manuscript Received May 15, 2010
ABSTRACT: A new conjugated metal-organic framework based on 2,20 ,4,40 -biphenyltetracarboxylic acid with a uninodal fiveconnected hexagonal boron nitride net (bnn) was synthesized, which represented the first example of metal-organic frameworks capable of adsorbing a trace level of organophosphate pestcide for efficient detection via stripping voltammetric analysis. A detection limit of 0.006 μg 3 mL-1 was obtained with the calculation based on a signal-noise ratio equal to 3.
*Author to whom correspondence should be addressed. E-mail:
[email protected] (L.-L.W.),
[email protected] (J.-M.G.),
[email protected] (D.-F.L.). Fax: þ86 27 67867232. Telephone: þ86 27 67862900.
thermally stable and luminescence active, and it exhibits great potential as an SPE material for detection of a trace level of organophosphate pestcide via stripping voltammetric analysis. As-synthesized, compound 1 (Figure 1a) is insoluble in water and common organic solvents. It was characterized by elemental microanalysis, IR spectroscopy, and single-crystal X-ray diffraction; phase purity was confirmed by powder X-ray diffraction (PXRD) (Figure S1 of the Supporting Information). The presence of an absorption peak at around 1700 cm-1 in its IR spectrum showed the existence of a protonated carboxylic group. Thermal gravimetric analysis (TGA) (Figure S2) indicated that the framework of 1 was thermally stable up to 330 °C, where the organic groups start to decompose. The PXRD pattern of an assynthesized power of 1 was identical to that calculated from the single-crystal structure. Compound 1 crystallizes in the orthorhombic space group Pbcn12 and displays a complicated 3D network. As depicted in Figure S3a, the asymmetric unit of 1 contains half a Cd(II) ion and half a 2,20 ,4,40 -bptcH22- anion. As to 2,20 ,4,40 -bptcH22-, the dihedral angle between two phenyl rings is 68.2°, and 2- and 4-carboxylate groups have 41.1° and 11.5° dihedral angles with the plane of the corresponding linking phenyl rings, respectively. Each Cd(II) ion is in a slightly distorted octahedral environment, coordinated by six carboxylate oxygen atoms from five distinct 2,20 ,4,40 -bptcH22- anions. The Cd-O bond lengths range from 2.2398(15) to 2.3330(16) A˚. In 1, the partially deprotonated ligand coordinates to five Cd(II) centers, with both two full deprotonated carboxylate groups (2,20 -COO-) in the trans conformation adopting μ2-η1:η1 modes and both two nondeprotonated carboxylate moieties (4,40 -COOH) adopting monodentate fashions (Figure S3b). The 2,20 ,4,40 -bptcH22- anions thus link cadmium ions to form a dense 3D framework (Figure 1b). In addition, strong hydrogen bonds between the nondeprotonated carboxylate oxygen atom (O3) and the deprotonated carboxylate oxygen atom (O1#6) [symmetry code: (#6) 1/2 þ x, 3/2 - y, 1 - z] with a separation of 2.550(2) A˚ increase the stability of 1. A better insight into the nature of 1 can be achieved by the application of TOPOS. Taking the centroid of the ligand and Cd1 as nodes and connections between them as rods, the 3D framework topology representation for 1 is illustrated in Figure 1c, which can be described as a uninodal five-connected hexagonal boron nitride net (bnn) with the Sch€ afli symbol of (46)(64).13 The solid-state luminescence of complex 1 and the free ligand 2,20 ,4,40 -bptcH4 (L) were investigated at room temperature and are shown in Figure S4. The emission spectra for 1 exhibit a main
r 2010 American Chemical Society
Published on Web 05/24/2010
The extensive use of organophosphates pesticides (OPs) for pest control has raised serious public concern regarding the healthiness, environment, and food safety, owing to the high toxicity.1 Therefore, rapid determination and reliable quantification of a trace level of OP compounds have become increasingly important for public security and health protection. Traditional analytical instruments, such as gas/liquid chromatography and mass spectroscopy, have been widely used for the determination of OPs.2 More recently, enzyme-based biosensors have emerged as a promising alternative to detect pesticides.3 Nevertheless, the analytical methods mentioned above have their obvious limitations. In search of more convenient and cost-effective alternatives, stripping voltammetric analysis combined with a preconcentration of OPs appears to be an ideal and highly sensitive technology.4 In particular, the efficient preconcentration of OPs onto a certain substrate is critical for stripping analysis. In this regard, the selection of solid-phase extraction (SPE) is very important.5 Recently, the design and synthesis of metal-organic frameworks (MOFs) has attracted much attention from chemists, not only for their great potential for a wide range of applications, such as gas storage and separation, and catalysis and sensing, but also owing to their intriguing framework architectures and topologies.6-9 All of these properties have been shown to be heavily reliant on the specific pore size and (or) the inherent conjugated framework structure. Nowadays, intriguing recognition and sensing functions of MOFs with respect to small solvent molecules, ions, and high explosives have been achieved.10 However, work on MOFs as solid-phase extraction materials for the efficient detecting of OPs has not been reported until now. Conjugated MOFs with high dimensionality may be considered as sorbents for SPE of nitroaromatic OPs by direct physical adsorption, due to the synergetic effect of weak interactions, such as hydrogen bond and π 3 3 3 π stacking interactions between MOFs and OPs. Therefore, MOFs may be expected as sorbents for SPE of OPs onto the surface of the electrode and then further realize their stripping voltammetric detection. In this Communication, we present a new MOF, namely [Cd(2,20 ,4,40 -bptcH2)]n (1), prepared via hydrothermal conditions of Cd(NO3)2 3 6H2O with the ligand 2,20 ,4,40 -biphenyltetracarboxylic acid (2,20 ,4,40 bptcH4), as colorless block-shaped crystals.11 The compound is
pubs.acs.org/crystal
2836
Crystal Growth & Design, Vol. 10, No. 7, 2010
peak at 500 nm. Since a similar emission (λmax = 430 nm) is also observed for L, the luminescence of the complex is tentatively assigned to ligand-to-ligand charge-transfer (LLCT).14 More interestingly, a strong adsorption property was found for complex 1 in our study, which motivates us to use 1 as a sorbent for solid-phase extraction (SPE) of organophosphate compounds and their detection. Among OP compounds, nitroaromatic OP compounds, such as methyl parathion (MP), paraoxon, and fenitrothion, exhibit good redox activities at the electrode surface.
Figure 1. (a) Coordination geometry of the Cd2þ ions in 1. (b) 3D framework of 1. (c) Topology analysis of 1: pink spheres represent Cd1 nodes, blue spheres represent the centroid of the ligand. Symmetry codes: (#1) - x, y, 3/2 - z ; (#2) -x, 2 - y, 1 - z; (#3) -1/2 þ x, 1/2 þ y, 3/2 - z; (#4) 1/2 - x, 1/2 þ y, z; (#5) x, 2 - y, 1/2 þ z.
Wen et al. Hence, we have selected MP as a model to demonstrate the effectiveness of 1 for detecting electroactive OP compounds. The redox mechanism of MP is attributed to a two-electron-transfer process after the reduction of the nitro group to the hydroxylamine group (Scheme 1). Therefore, the stripping voltammetric performances of MP adsorbed on the surface of 1 were evaluated by square-wave voltammetric (SWV) analysis, which has been proven to be more highly sensitive than other electrochemical techniques. The determination of MP as a model included two main steps: (a) MP adsorption and (b) electrochemical stripping detection of adsorbed MP (Scheme 2). Complex 1 (3 mg) was added to 3.0 mL of doubly distilled water and sonicated thoroughly until a homogeneous suspension was obtained. The compound 1 modified glass carbon electrode (labeled as MOF/GCE) was prepared by casting 10.0 μL of the above homogeneous suspension onto a GCE surface and drying in air. The MOF/GCE was immersed into a sample solution containing the desired MP concentration, and the peak currents increased rapidly with an increase of immersion time and then tended to be stable at approximately 12 min, which indicates that the adsorption of MP into 1 reaches saturation. As shown in Figure 2, a very sharp and well-defined stripping peak at a potential of about 0.08 V vs saturated calomel electrode (SCE) appeared with the adsorption of MP into MOF (curve b). Compared with the direct adsorption of MP onto the bare GCE (curve a), the stripping peak current at MP adsorbed MOF/GCE was greatly enhanced, exhibiting a strong accumulation effect of MOF towared MP. The rapid and highly effective accumulation was attributed to the strong affinity of compound 1 to pesticide MP, which may be ascribed to the synergetic effect of weak interactions, such as the hydrogen bonds between the nondeprotonated carboxylate of 1 and the nitro group of MP, in combination with the π 3 3 3 π stacking interaction between the highly conjugated backbone of 1 and the flat molecular structure of MP. Figure 3 displays the SWV response of adsorbed MP by the SPE process at MOF/GCE. Well-defined peaks, proportional to the concentration of the corresponding MP, were observed in the range from 0.01 to 0.5 μg 3 mL-1. The linearization equation was i/μA=0.27 þ 2.15c μg 3 mL-1, with the correlation coefficients of 0.9958 (inset of Figure 2). A detection limit of 0.006 μg 3 mL-1 was obtained with the calculation based on a signal-noise ratio equal to 3. This detection limit is distinctly lower than 0.0132 μg 3 mL-1 at a carbon-paste electrode by using stripping analysis and is comparable with that of 0.0048 μg 3 mL-1 at the hanging mercury drop electrode.4,15 Our results suggest that the reported MOF in the case is reliable for the determination of OP pesticides. The relative standard deviation was 5.2% for 10 replicate determinations of 0.1 μg 3 mL-1 MP, indicating acceptable reproducibility. After electrochemical stripping detection, the MOF/ GCE was rinsed with water and then transferred into the blank electrolyte (0.1 M, pH 5.7 phosphate buffer solutions (PBS)) for SWV measurements. Multiple successive SWV scanning was used to remove the bound MP until the anodic stripping response disappeared. Therefore, the regeneration of the MOF/GCE was accomplished. Furthermore, no obvious interferences
Scheme 1. Redox Mechanism of MP
Communication
Crystal Growth & Design, Vol. 10, No. 7, 2010
2837
Scheme 2
platform for determination of OP compounds based on MOFs will emerge. An in depth study is currently underway to fully understand the adsorption mechanism between MP and this material. Acknowledgment. We greatly appreciate financial support from the National Nature Science Foundation of China (Nos. 20801021, 20802022 and 20803026), the Program for New Century Excellent Talents in University of China (NCET-10-040), Natural Science Foundation of Hubei Province (Nos. 2008CDZ039 and 2008CDB032), Program for Innovation Group of Hubei Province of China (2009CDA048), and Open Fund of Hubei Key Laboratory of Catalysis and Materials Science (CHCL 08005).
Figure 2. Stripping voltammograms obtained at the solution containing 0.1 μg 3 mL-1 MP absorbed (a) onto the bare GCE and (b) onto the MOF/GCE. SWV conditions: scanning potential range, -0.2 to 0.2 V; frequency, 25 Hz; potential increment, 4 mV; amplitude of the square-wave, 20 mV. Electrolyte: 0.1 M PBS, pH 5.7.
Figure 3. Stripping voltammograms of increasing MP concentrations (from bottom to top: 0, 0.01, 0.05, 0.1, 0.2, and 0.5 μg 3 mL-1, respectively). The inset shows the calibration curve. SWV conditions: scanning potential range, -0.25 to 0.25 V; frequency, 25 Hz; potential increment, 4 mV; amplitude of the square-wave, 20 mV. Electrolyte: 0.1 M PBS, pH 5.7.
were observed from the electroactive derivatives, such as nitrobenzene, and other oxygen-containing inorganic ions (PO43-, SO42-, NO3-) with the peak currents of MP varied slightly. To the best of our knowledge, this is the first successful attempt at the determination of OPs by using MOF as SPE based on the SWV method. In summary, we have prepared the first crystalline metalorganic polymer that can act as a good solid-phase extraction material capable of adsorbing and concentrating trace OP compounds for an efficient detection through SWV analysis. The remarkable preliminary results point to a new and important application of metal-organic framework materials. We anticipate that a fertile and exciting field toward developing a highly sensitive
Supporting Information Available: Experimental details, plots of XRD, TGA, and fluorescent emission spectra for 1, and crystallographic information files (CIF). This material is available free of charge via the Internet at http://pubs.acs.org.
References (1) (a) Arduini, F.; Ricci, F.; Tuta, C. S.; Moscone, D.; Amine, A.; Palleschi, G. Anal. Chim. Acta 2006, 580, 155. (b) Li, B. X.; He, Y. Z.; Xu, C. L. Talanta 2007, 72, 223. (c) Li, X. H.; Xie, Z. H.; Min, H.; Xian, Y. Z.; Jin, L. T. Electroanalysis 2007, 24, 2257. (2) (a) Chen, P. S.; Huang, S. D. Talanta 2006, 69, 669. (b) Leandro, C. C.; Hancock, P.; Fussell, R. J.; Keely, B. J. J. Chromatorgr., A 2006, 1103, 94. (c) Rotiroti, L.; Stefano, L. D.; Rendina, I.; Moretti, L. Biosens. Bioelectron. 2005, 20, 2136. (3) (a) Jeanty, G.; Marty, J. L. Biosens. Bioelectron. 1998, 13, 213. (b) Vakurov, A.; Simpson, C. E.; Daly, C. L.; Gibson, T. D.; Millner, P. A. Biosens. Bioelectron. 2004, 20, 1118. (c) Sotiropoulou, S.; Fournier, D.; Chaniotakis, N. A. Biosens. Bioelectron. 2005, 20, 2347. (d) Gong, J. M.; Wang, L. Y.; Zhang, L. Z. Biosens. Bioelectron. 2009, 24, 2285. (4) (a) Gong, J. M.; Wang, L. Y.; Song, D. D.; Zhu, X. L.; Zhang, L. Z. Biosens. Bioelectron. 2009, 25, 493. (b) Du, D.; Ye, X. P.; Zhang, J. D.; Zeng, Y.; Tu, H. Y.; Zhang, A. D.; Liu, D. L. Electrochem. Commun. 2008, 10, 686. (c) Liu, G. D.; Lin, Y. H. Electrochem. Commun. 2005, 7, 339. (d) Liu, G. D.; Lin, Y. H. Anal. Chem. 2005, 77, 5894. (5) (a) Hennion, M. C. J. Chromatogr., A 2000, 855, 73. (b) Shi, L. H.; Liu, X. Q.; Li, H. J.; Niu, W. X.; Xu, G. B. Anal. Chem. 2006, 78, 1345. (6) Mueller, U.; Schubert, M.; Teich, F.; Puetter, H.; Schierle-Arndt, K.; Pastre, J. J. Mater. Chem. 2006, 16, 626. (7) (a) Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem., Int. Ed. 2004, 43, 2334. (b) Kitaura, R.; Kitagawa, S.; Kubota, Y.; Kobayashi, T. C.; Kindo, K.; Mita, Y.; Matsuo, A.; Kobayashi, M.; Chang, H.; Ozawa, T. C.; Suzuki, M.; Sakata, M.; Takata, M. Science 2002, 298, 2358. (c) Higuchi, M.; Tanaka, D.; Horike, S.; Sakamoto, H.; Nakamura, K.; Takashima, Y.; Hijikata, Y.; Yanai, N.; Kim, J.; Kato, K.; Kubota, Y.; Takata, M.; Kitagawa, S. J. Am. Chem. Soc. 2009, 131, 10336. (d) Hasegawa, S.; Horike, S.; Matsuda, R.; Furukawa, S.; Mochizuki, K.; Kinoshita, Y.; Kitagawa, S. J. Am. Chem. Soc. 2007, 129, 2607. (8) (a) Li, K. H.; Olson, D. H.; Seidel, J.; Emge, T. J.; Gong, H. W.; Zeng, H. P.; Li, J. J. Am. Chem. Soc. 2009, 131, 10368. (b) Lan, A. J.; Li, K. H.; Wu, H. H.; Kong, L. Z.; Nijem, N.; Olson, D. H.; Emge, T. J.; Chabal, Y. J.; Langreth, D. C.; Hong, M. C.; Li, J. Inorg. Chem. 2009, 48, 7165. (c) Li, K. H.; Lee, J.; Olson, D. H.; Emge, T. J.; Bi, W. H.; Eibling, M. J.; Li, J. Chem. Commun. 2008, 46, 6123. (d) Pan, L.; Parker, B.; Huang, X. Y.; Olson, D. H.; Lee, J. Y.; Li, J. J. Am. Chem. Soc. 2006, 128, 4180. (e) Pan, L.; Olson, D. H.; Ciemnolonski, L. R.; Heddy, R.; Li, J. Angew. Chem., Int. Ed. 2006, 45, 616.
2838
Crystal Growth & Design, Vol. 10, No. 7, 2010
(9) (a) Ma, S. Q.; Zhou, H. C. Chem. Commun. 2010, 46, 44. (b) Kuppler, R. J.; Timmons, D. J.; Fang, Q. R.; Li, J. R.; Makal, T. A.; Young, M. D.; Yuan, D. Q.; Zhao, D.; Zhuang, W. J.; Zhou, H. C. Coord. Chem. Rev. 2009, 253, 3042. (c) Ma, S. Q.; Simmons, J. M.; Yuan, D. Q.; Li, J. R.; Weng, W.; Liu, D. J.; Zhou, H. C. Chem. Commun. 2009, 27, 4049. (d) Li, J. R.; Kuppler, R. J.; Zhou, H. C. Chem. Soc. Rev. 2009, 38, 1477. (e) Henninger, S. K.; Habib, H. A.; Janiak, C. J. Am. Chem. Soc. 2009, 131, 2776. (f) Janiak, C. Dalton Trans. 2003, 2781. (10) (a) Qiu, Y. C.; Deng, H.; Mou, J. X.; Yang, S. H.; Zeller, M.; Batten, S. R.; Wu, H. H.; Li, J. Chem. Commun. 2009, 36, 5415. (b) Lan, A. J.; Li, K. H.; Wu, H. H.; Olson, D. H.; Emge, T. J.; Ki, W.; Hong, M. C.; Li, J. Angew. Chem., Int. Ed. 2009, 48, 2334. (c) Chen, B.; Wang, L.; Zapata, F.; Qian, G.; Lobkovsky, E. B. J. Am. Chem. Soc. 2008, 130, 6718. (d) Zhao, B.; Chen, X. Y.; Cheng, P.; Liao, D. Z.; Yan, S. P.; Jiang, Z. H. J. Am. Chem. Soc. 2004, 126, 15394. (e) Zhao, B.; Gao, H. L.; Chen, X. Y.; Cheng, P.; Shi, W.; Liao, D. Z.; Yan, S. P.; Jiang, Z. H. Chem.-Eur. J. 2006, 12, 149. (11) Synthesis of [Cd(2,20 ,4,40 -bptcH2)]n: A mixture of Cd(NO3)2 3 6H2O (34.4 mg, 0.1 mmol), 2,20 ,4,40 -bptcH4 (30.1 mg, 0.1 mmol), and one drop of 6 M HCl in H2O (5 mL) was placed in a parr Teflon-lined stainless steel vessel (25 cm3), and then the vessel was sealed and heated at 180 °C for 3 days. After the mixture was slowly
Wen et al.
(12)
(13)
(14) (15)
cooled to room temperature, colorless block crystals of 1 were obtained (yield: 56% based on Cd). Anal. Calcd for [Cd(2,20 , 4,40 -bptcH2)]n (Found): C, 43.61 (43.55); H, 1.83 (1.89). IR data (KBr, cm-1): 3434(w), 1704 (m), 1650(s), 1566(s), 1412(s), 1370(s), 1268(w), 1239(s), 1131(w), 1003(w), 788(m), 694(m), 654(w), 527(w). Crystal data for 1: formula C16H8CdO8, M = 440.62, orthorhombic, space group Pbcn, a = 15.9934(12) A˚, b = 9.1122(7) A˚, c = 9.9053(8) A˚, V=1443.55(19) A˚3, Z=4, μ(Mo KR)=1.560 mm-1, F = 2.027 g 3 cm-3, reflection numbers collected = 11557, unique reflections (Rint) = 1670 (0.030), R1 [I > 2σ(I)] = 0.0205, wR2 (all data) = 0.0563, GOF = 1.04. CCDC 760917. (a) Blatov, V. A.; O’Keeffe; Proserpio, D. M. CrystEngComm 2010, 12, 44. (b) Blatov, V. A.; Proserpio, D. M. Acta Crystallogr., A 2009, 65, 202. (c) Rosi, N. L.; Kim, J.; Eddaoudi, M.; Chen, B. L.; O'Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2005, 127, 1504. (d) Ockwig, N. W.; Delgado-Friedrichs, O.; O'Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2005, 38, 176. (a) Jia, T. T.; Zhu, S. R.; Shao, M.; Zhao, Y. M.; Li, M. X. Inorg. Chem. Commun. 2008, 11, 1221. (b) Kurtz, S. K.; Perry, T. T. J. Appl. Phys. 1968, 39, 3798. Ni, Y. N.; Qiu, P.; Kokot, S. Anal. Chim. Acta 2004, 516, 7.
