Two Tetranuclear Zinc(II) Coordination Polymers Based on 3,5-Bis(2-carboxylphenoxy)benzoic Acid with Highly Selective Sensing of Nitrobenzene①

FANGKe-GongZHAOQin-NnLIMio-MioHUTuo-Ping,

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Two Tetranuclear Zinc(II) Coordination Polymers Based on 3,5-Bis(2-carboxylphenoxy)benzoic Acid with Highly Selective Sensing of Nitrobenzene①

FANG Ke-GongaZHAO Qian-NanbLI Miao-MiaobHU Tuo-Pinga, b②

a(,030001)b(030051)

Two novel zinc(II) coordination polymers,[Zn2(BCB)(CH3OH)(3-OH)]n(1) and{[Zn2(BCB)(3-OH)(H2O)2]·CH3OH}n(2), have been constructed from 3,5-bis(2-carboxyl- phenoxy)benzoic acid (H3BCB)and characterized by elemental analysis (EA), IR, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Structural analysis reveals that complexes 1 and 2 are both 1D polymeric chains with unprecedented tetranuclear {Zn4(COO)4(3-OH)2} clusters, which were further expanded into a 2D structure.Fluorescence measurements show that 1 and 2 have highly selective and sensitive detection of nitrobenzene.

3,5-bis(2-carboxylphenoxy)benzoic acid, tetranuclear cluster, zinc, luminscence, sensing;

1 INTRODUCTION

Being a prominent representative of inorganic- organic hybrid materials, the coordination polymers (CPs) have attracted more and more attention of materials scientists and chemists for their fascinating structures and potential applications in the fields of gas adsorption and separation, catalysis and photocatalysis, molecule sensing and fluorescent probe, molecular switch, and so on[1-4].

With the development in the level of industria- lization and the social activities of human beings, environmental problems have become major issues[5]. Lots of toxic organic molecules and heavy metal ions have caused a lot of adverse effects on the health of human being. Nitroaroma- tics (NACs), a kind of important chemical raw materials widely used in leather, dyes, fireworks, and the glass industry, are explosive and hazardous[6]. Therefore, effective detection of NACs is important to environmental safety.

In general, CPs can be constructed form organic linkers and inorganic nodes under suita- ble situation. However, many influence factors, including internal and external factors, greatly affected the assembly of CPs[7, 8]. Among them, the backbone of organic linkers occupied an important position without a shadow of a doubt. A myriad of obtained CPs has been proved that the reasonable design of organic linkers is an efficiently route in building CPs[9]. To our knowledge, the tripodal linkers have been widely selected in building functional CPs for their interesting backbone and various coordination modes[10, 11]. Moreover, the flexible backbone usually endows the linkers more freedom to adjust themselves when coordinating with the metal ions. And the large conjugated rings of linker have high sensitivity and selectivity because of the high binding strength to the nitroaromatic compounds as electron donors, and benefit for electron transfer[12].Thus, the investi- gation of flexible tripodal linkers based CPs seems interesting and meaningful.

Inspired by the above mentioned points and followed our recent research, we selected a flexible tripodal ligand of 3,5-bis(2-carboxylphenoxy)- benzoic acid (H3BCB) to react with transition metal salts, finally obtaining two CPs with tetranuclear {Zn4(COO)4(3-OH)2} SBUs based 1D polymeric chain (1 & 2). And theluminescence and sensing of small molecules of 1 and 2have been investigated.

2 EXPERIMENTAL

2. 1 Generals

All chemicals were purchased from Jinan Henghua Sci. & Tec. Co. Ltd. without further purification.IR spectrawere measured on a FTIR-8400S spectrometer in the range of 400～4000 cm-1(Fig. S1, see ESI). Elemental analyses were carried out on a Vario MACRO cube elemen- tal analyzer. TGA was measured from 25 to 800oC on a ZCTA analyzer at a heating rate 10oC/min under air atmosphere.X-ray powder diffractions of the title complexes were measured on a Rigaku D/Max-2500 PC diffractometer with Mo-radiation over the 2range of 5～50° at room temperature. Fluorescence spectra were performed on an F-2700 FL spectrophotometer at room temperature.

2. 2 Synthesis of [Zn2(BCB)(CH3OH)(μ3-OH)]n (1)

The H3BCB (0.010 mmol, 3.9 mg) was dissolved in 2 mL MeOH, and a dorp of 0.05 mol/L NaOH aqueous solution was added to deprotonate. After that, 2 mL aqueous solution of Zn(NO3)2·6H2O (0.06 mmol, 17.8 mg) was added into the solution, then the mixed reactantswere sealed in a 15 mL Teflon-lined stainless-steel vessel, which was heated to130 °C for 2 days and then cooled to room temperature slowly.Colorless block crystals of 1were obtained. Yield: 40% based on H3BCB. Anal. Calcd. (%) for C22H16O10Zn2: C, 42.26; H, 2.82. Found(%): C, 42.31; H, 2.94. IR (KBr pellet, cm-1): 3554 (m), 1591 (s), 1561 (s), 1475 (m), 1393 (s), 1282 (w), 1207 (s), 1125 (m), 1096 (w), 997 (m), 863 (w), 706 (w), 659 (w).

2. 3 Synthesis of {[Zn2(BCB)(μ3-OH)(H2O)2]·CH3OH}n (2)

A mixture of Zn(NO3)2·6H2O (0.015 mmol, 4.5 mg), H3BCB (0.005 mmol, 2.0 mg), H2O/MeOH (1 mL, v/v = 1/1), and two drops of ammonia water was added to a hard glass tube, pumped into a near-vacuum, and heated at 130 °C for 2 days, and then cooled to room temperature. Colorless block crystals of 2were obtained. Yield: 36% based on H3BCB. Anal. Calcd. (%) for C22H20O12Zn2: C, 43.52; H, 3.32. (%): C, 43.37; H, 3.41. IR (KBr pellet, cm-1): 3566 (m), 3426 (m), 1592 (s), 1557 (s), 1476 (w), 1394 (s), 1272 (w), 1207 (m), 1126 (m), 1092 (w), 998 (m), 864 (m), 765 (m), 701 (w), 653 (w).

2. 4 Structure determination

Intensity data collection was carried out on a Siemens SMART diffractometer equipped with a CCD detector using a graphite-monochromatized Moradiation (= 0.71073 ?) at 296(2) K. The absorption correction was based on multiple and symmetry-equivalent reflections in the data set using the SADABS program based on the method of Blessing[13]. The structure was solved by direct methods and refined by full-matrix least-squares using the SHELXS-97 package, and further refined by SHELXL-97 procedure[14]. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms bound to carbon were refined using ariding model with C–H = 0.93 ? andiso= 1.2eo(C). The H atoms of water molecules were located from difference density maps and refined with restraints of O–H = 0.82(2) and H–H = 1.38(2) ?.Crystallo- graphic data for complexes 1 and 2are given in Table S1, and their elected bond lengths and bond angles are listed in Table 1 and Table S2.

Scheme 1. Coordination modes of H3BCB in 1 and 2, with,andcorresponding to the dihedral angles between rings A/B, B/C, and A/C of the deprotonated H3BCBligand

Table 1. Selected Bond Lengths (?) and Bond Angles (o) for 1 and 2

Symmetry codes:#1–+1, –, –+1 for 1;#1–+1, –+1, –for 2

3 RESULTS AND DISCUSSION

3. 1 Description of the [Zn2(BCB)(CH3OH)(μ3-OH)]n (1)

Structural analysis reveals thatcomplex 1 crystallizesin the monoclinic system, space group21/. As shown in Fig. 1a, the asymmetric unitconsists oftwo crystallographically independent ZnIIions, one BCB3-ligand, one3-OH-anion, and one coordinated CH3OH molecule. Zn(1) is pentacoordinated by fiveO atoms from two dif- ferent BCB3-ligands, two3-OH-anions, and one coordinated CH3OH molecule, exhibiting a distortedtrigonal bipyramidgeometry (5= 0.53(0),5= |–|/60°[15a],andare the two largest bond angles in the five-coordinated complex). Zn(2)locates in a distorted tetrahedron {ZnO4} coor- dination environment with the4parameter being 0.86(2) (4= [360°–()]/141°[15a], whereandare the two largest bond angles in the four- coordinate complex.),completed by four O atoms from three BCB3-ligands and one3-OH-anion. Besides, the Zn–O bond lengths range from 1.971(7) to 2.214(4) ?, respectively, which are similar to the reported reference[15b].

In the assembly of complex 1, the H3BCB is completely deprotonated and connects five ZnIIions by adopting a (1-0)-(1-1)-(1-1)-coordination mode (Mode I, Scheme 2), in which the dihedral angles of,, andare 76.18(5)°, 83.48(6)° and 44.94(3)° (here,,andcorrespond to the dihedral angles between rings A/B, B/C, and A/C of the BCB3-ligand). With the help of tricoordinated3-OH-anions, the bridging carboxyl groups connected four ZnIIions, obtaining an interestingly tetranuclear {Zn4(COO)4(3-OH)2} cluster, with the nearestZn···Zn distances being 3.347 ? for Zn(1)···Zn(2) and 3.230 ? for Zn(1)···Zn(2A) (Fig. 1b), which are close to the literature[15b]. Then, the BCB3-ligands linked the {Zn4(COO)4(3-OH)2} clusters, thus successfully forming an unprece- dented 1D polymeric chain with the separated {Zn4(COO)4(3-OH)2} cluster distance to be 8.112 ? (Fig. 2). Those 1D polymeric chains interacted with each other through hydrogen bonds (C(1)– H(1)···O(36i) = 3.564(3) ?, C(32)–H(32)···O(22ii) = 3.856(2) ?, Symmetry codes: i: 1/2 +,3/2 –, 1/2 +; ii: 3/2 –,–1/2 +, 3/2 –), leaving a 2D supramolecular structure (Fig. 3).

Fig. 1. (a) Asymmetric unit of complex 1. (b) Tetranuclear{Zn4(COO)4(3-OH)2} SBUs. (Symmetry codes: A: 1–, –, 1–; B: 1–, 1–, 1–; D:, 1+,)

Fig. 2. Schematic view of the 1Dpolymeric chain of 1 along thedirection

Fig. 3. Hydrogen-bond expanded 2D sheet of 1 viewed along thedirection

3. 2 Description of {[Zn2(BCB)(μ3-OH)(H2O)2]n·CH3OH}n(2)

In complex 2, the BCB3-ligand adopted a (1-1)-(1-1)-(1-1)-coordination mode (Mode II, Scheme 2) to connect four ZnIIions, with the dihedral angles of,, andbeing 75.72(1)°, 73.62(7)°, and 37.63(3)°, respectively. It is notewor- thy that four 2-position carboxyl groups from two different BCB3-ligands interacted with four ZnIIions with the help of3-OH-anions, constructing a similar {Zn4(COO)4(3-OH)2} cluster with the Zn···Zn distances being 3.345 ? for Zn(1)···Zn(2) and 3.344 ? for Zn(1)···Zn(2A) (Fig. 4b). Then the BCB3-ligands linked the {Zn4(COO)4(3-OH)2} clusters, leaving a 1D polymeric chain with the separated {Zn4(COO)4(3-OH)2} cluster distance to be 13.068 ? (Fig. 5). Those 1D polymeric chains further interacted with the adjacent ones through hydrogen bonds (O(1W)–H(1WA)···O(8i) = 3.158(5) ?, C(9)–H(9)···O(1i) = 3.598(4) ?, O(2W)–H(2WA)···O(9ii) = 3.207(4) ?, C(3)– H(3)···O(9ii) = 3.447(7) ?, C(18)–H(18)···O(8iii) = 3.408(8) ?. Symmetry codes: i: –,1–, –; ii:,–1+,; iii: 1+,,), finally leaving a 2D sheet (Fig. 6).

Fig. 4. (a) Asymmetric unit of complex 2. (b) Tetranuclear{Zn4(COO)4(3-OH)2} SBUs.(Symmetry codes: A: 1–, 1–, –; B: –, 2–, –)

Fig. 5. Schematic view of the 1Dpolymeric chain of 2

Fig. 6. Hydrogen-bond expanded 2D sheet of 2

3. 3 Powder X-ray diffraction and thermogravimetric analysis

In order to check the phase purity of this complex, the PXRD patterns of the title complexes were checked at room temperature. As shown in Fig. S2, the peak positions of the simulated and experimental PXRD patterns are in agreement with each other, demonstrating good phase purity of the complexes. The dissimilarities in intensity may be due to the preferred orientation of the crystalline powder samples.

In order to investigate thermal stability of the title complexes, thermogravimetric analysis was carried out and the TG curve is depicted in Fig. S3. For 1, the preliminary weight loss below 200oCcorres- ponds to the release of coordinated methanol molecules and3-water molecules (obsd: 8.31%; calcd: 8.58%) and then the architecture can exist stablely until the temperature is up to 450 °C.For2, the first weight loss in the temperature range of 120～210 °C can be attributed to the release of coordinated water molecules,3-water molecules, as well as the free methanol molecules(obsd: 13.23%; calcd: 14.00%). No obvious weight loss is observed until the decomposition of the architecture occurs at about 380 °C.

Fig. 7. Emission spectra of complexes 1 and 2 inthe solid state at room temperature

3. 4 Photoluminescence and sensing of small molecules

The fluorescence spectra of fresh complexes 1 and 2were performed on an F-4600 FL spectro- photometer in the solid state at room temperature in the scan range of 280～560 nm, as shown in Fig. 7. For complexes 1 and 2, the emission spectra exhibit strong blue-fluorescent emission peaks at 353 nm (ex= 300 nm) for 1 and357 nm (ex= 300 nm) for 2, respectively.The emission is neither metal-to-ligand charge transfer (MLCT) norligand-to-metal transfer (LMCT) in nature since theZnIIion is difficult to oxidize or reduce due to its10con-figuration.Thus, they can be assigned to intraligand (*→or→*)emission[16].

Fig. 8. Luminescence intensity of complex 1 dispersed in different organic solvents

Fig. 9. (a) Effect on the emission spectra of 1 dispersed in DMSO upon incremental addition of NB analyte. (b) Fluorescence quenching linearity relationship at low concentration of NB

To further explore the sensing sensitivity of fresh complexes 1 and 2 for small solvent molecules, six kinds of solvent molecules, including DMF, DMSO, CH3OH, CH3CN, N-butyl alcohol and nitrobenzene (NB), are selected for the luminescent sensing studies. Here, finely ground samples of complexes 1 and 2 (2 mg) were dispersed in 2 mL various organic solvents. As shown in Figs. 8 and 10, complexes 1 and 2 dispersed in DMSO display the strongest luminescent intensity, which exhibits the weakest emission in NB. To further research the recognition of complexes 1 and 2 for NB, the luminescence of series NB solutions with different concentrations was tested. Complex 1 presents obvious quenching effects of fluorescence intensity with increasing the addition of NB, and the quenching rate of the emission reaches as much as 89.4% when the concentration of NB in the suspension solution is 0.30 mM (Fig. 9). The quenching effect can be rationalized by the Stern-Volmer equation: (/) =K[Q] + 1, whereandare the luminescence intensities of DMSO suspensions before and after adding NB, respectively;Kis the quenching constant (M?1); [Q] is the molar concentration of NB[17].The Stern-Volmer plots are nearly linear at low concentration. For complex 2, the quenching percentage for NB is 76.0% (Fig. 11). And theKvalues with NB are 2.33 × 104M?1for 1 and 2.07 × 104M?1for 2[18]. This phenomenon shows that complexes 1 and 2 may be both good candidates to detect nitrobenzene.The luminescence quenching of CPs for NB may be interpreted by the photoinduced electrontransfer mechanism caused by inductive effect or the fluorescence resonance energy transfer (FRET) mechanism[19].

Fig. 10. Luminescence intensities of complex 2 dispersed in different organic solvents

Fig. 11. (a) Effect on the emission spectra of 2 dispersed in DMSO upon incremental addition of NB analyte. (b) Fluorescence quenching linearity relationship at low concentration of NB

(1) (a) Gai, Y.; Guo, Q.; Xiong, K.; Jiang, F.; Li, C.; Li, X.; Chen, Y.; Zhu, C.; Huang, Q.; Yao, R.; Hong, M. Mixed-lanthanide metal-organic frameworks with tunable color and white light emission.2017, 17, 940–944;(b) Hu, Z.; Deibert, B. J.; Li, J. Luminescent metal-organic frameworks for chemical sensing and explosive detection.2014, 43, 5815?5840.

(2) (a) Lustig, W. P.; Mukherjee, S.; Rudd, N. D.; Desai, A. V.; Li, J.; Ghosh, S. K. Metal-organic frameworks: functional luminescent and photonic materials for sensing applications.2017, 46, 3242?3285; (b) Fan, L.; Fan, W.; Li, B.; Liu, X.; Zhao, X.; Zhang, X. Structural diversities and related properties of four coordination polymers synthesized from original ligand of 3,3?,5,5?-azobenzenetetracarboxylic acid.2015, 44, 2380?2389.

(3) (a) Feng, X.; Feng, Y.; Guo, N.; Sun, Y.; Zhang, T.; Ma, L.; Wang, L. Seriesheteronuclear metal-organic frameworks: color tunability and luminescent probe with switchable properties.2017, 56, 1713–1721; (b) Zhang, X. T.; Fan, L. M.; Sun, Z.; Zhang, W.; Fan, W. L.; Sun, L. M.; Zhao, X. Syntheses, structures, and luminescence of four lanthanide metal-organic frameworks based on lanthanide-oxide chains with2- or3-symmetric trigonal-planar polycarboxylate ligands.2013, 124910?4916.

(4) (a) Huo, L.; Zhang, J.; Gao, L.; Wang, X.; Fan, L.; Fang, K.; Hu, T. Two cadmium coordination polymers based on tris(-carboxyphenyl) phosphane oxide with highly selective sensing of nitrobenzene derivatives and Hg2+cations.2017, 19, 5285?5292; (b) Zhang, X.; Fan, L.; Fan, W.; Li, B.; Zhao, X. Assembly of a series of10coordination polymers based on W-shaped 1,3-di(2?,4?-dicarboxyphenyl)benzene: from syntheses, structural diversity, luminescence, to photocatalytic properties.2015, 17, 6681?6692; (c) Liu, G. Z.; Chen, H. T.; Zhang, X. T. Syntheses, crystal structures, and fluorescence properties of three coordination polymers constructed based on benzoic acid and its derivatives.2017, 36, 2058-2066.

(5) (a) Chowdhury, A.; Howlader, P.; Mukherjee, P. S. Aggregation-induced emission of platinum(II) metallacycles and their ability to detect nitroaromatics.2016, 22, 7468?7478; (b) Meng, Q.; Xin, X.; Zhang, L.; Dai, F.; Wang, R.; Sun, D. A multifunctional Eu MOF as a fluorescent pH sensor and exhibiting highly solvent-dependent adsorption and degradation of rhodamine B.2015, 3, 24016?24021; (c) Kong, Z. G.; Liu, D. X.; Song, M. Y.; Zhang, L. Y.; Feng, S. S.; Xu. Z. L. A two-dimensional supramolecular complex constructed by 1,10-phenanthroline derivative ligand: synthesis, structure and luminescence.2017, 36, 1859-1863.

(6) (a) Li, W. J.; Lu, J.; Gao, S. Y.; Li, Q. H.; Cao, R. Electrochemical preparation of metal-organic framework films for fast detection of nitro explosives2014, 2, 19473?19478; (b) Wang, G. Y.; Song, C.; Kong, D. M.; Ruan, W. J.; Chang, Z.; Li, Y. Two luminescent metal-organic frameworks for the sensing of nitroaromatic explosives and DNA strands2014, 2, 2213?2220; (c) Wang, Z.; Tang, C. C.; Ren, X. M.; Mao, Y. R.; Yao, Q. X.; Li, D. C.; Dou, J. M. Syntheses, crystal structures and luminescent properties of two lanthanide coordination polymersbased on bifunctional ligand.2017, 36, 1631-1638.

(7) (a) Fan, L. M.; Zhang, X. T.; Li, D. C.; Sun, D.; Zhang, W.; Dou, J. M. Supramolecular isomeric flat and wavy honeycomb networks: additive agent effect on the ligand linkages.2014, 16, 9191?9197; (b) Fan, L.; Fan, W.; Li, B.; Liu, X.; Zhao, X.; Zhang, X. Structural diversities and related properties of four coordination polymers synthesized from original ligand of 3,3?,5,5?-azobenzenetetracarboxylic acid.2015, 44, 2380?2389.

(8) (a) Hu, T.; Zeng, B.; Wang, X.; Hao, X. Syntheses, structures and magnetic properties of four manganese(II) and cobalt(II) complexes.2015, 17, 9348?9356; (b) Fan, L.; Fan, W.; Li, B.; Liu, X.; Zhao, X.; Zhang, X. Structural diversity of five coordination polymers based on 2,6-bis(3,5-dicarboxyphenyl)pyridine ligand: solvothermal syntheses, structural characterizations, and magnetic properties.. 2015, 17, 4669?4679.

(9) (a) Zhang, X.; Fan, L.; Fan, W.; Li, B.; Zhao, X. Assembly of a series of10coordination polymers based on W-shaped 1,3-di(2?,4?-dicarboxyphenyl)benzene: from syntheses, structural diversity, luminescence, to photocatalytic properties.2015, 17, 6681?6692; (b) Huo, L.; Zhang, J.; Gao, L.; Wang, X.; Fan, L.; Fang, K.; Hu, T. Selective sensing of two novel coordination polymers based on tris(4-carboxylphenyl)phosphine oxide for organic molecules and Fe3+and Hg2+ions.2017, 256, 168?175.

(10) (a) Wang, X. X.; Wang, X. Q.; Niu, X. Y.; Hu, T. P.Three novel metal-organic frameworks based on an unsymmetrical rigid carboxylate ligand for luminescence sensing of nitrobenzene derivatives and magnetic properties.2016, 18, 7471?7477; (b) Fan, L.; Zhang, X.; Sun, Z.; Zhang, W.; Ding, Y.; Fan, W.; Sun, L.; Zhao, X.; Lei, H. Ancillary ligands dependent structural diversity of a series of metal-organic frameworks based on 3,5-bis(3-carboxyphenyl)pyridine.2013, 13, 2462–2475.

(11) (a) Zhang, X.; Fan, L.; Fan, W.; Li, B.; Liu, G.; Liu, X.; Zhao, X. Structural diversity, luminescence and photocatalytic properties of six coordination polymers based on designed bifunctional 2-(imidazol-1-yl)terephthalic acid.2016, 18, 6914?6925; (b) Fan, L.; Fan, W.; Song, W.; Sun, L.; Zhao, X.; Zhang, X. Structural diversity and magnetic properties of six metal-organic polymers based on semirigid tricarboxylate ligand of 3,5-bi(4-carboxyphenoxy)benzoic acid.2014, 43, 15979?15989.

(12) Thomas, S.W.; Joly, G.D.; Swager,T. M. Chemical sensors based on amplifying fluorescent conjugated polymers.2007, 107, 1339?1386.

(13) Bruker AXS.;Bruker: Madison, WI 1998.

(14) Sheldrick, G. M..University of G?tingen, Germany 1997.

(15) (a)Yang, L.; Powell, D. R.; Houser, R. P. Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index,4.2007, 955–964; (b) Wan, X. Y.; Jiang, F. L.; Chen, L.; Pan, J.; Zhou, K.; Su, K. Z.; Pang, J. D.; Lyu, G. X.; Hong, M. C. Structural variability, unusual thermochromic luminescence and nitrobenzene sensing properties of five Zn(II) coordination polymers assembled from a terphenyl-hexacarboxylate ligand.. 2015, 17, 3829–3837.

(16) Cui, Y. J.; Yue, Y. F.; Qian, G. D.; Chen, B. L. Luminescent functional metal-organic frameworks.2012, 112, 1126?1162.

(17) (a) Han, L. H.; Yan, W.; Chen, S. G.; Shi, Z. Z.; Zheng, H. G. Exploring the detection of metal ions by tailoring the coordination mode of V-shaped thienylpyridyl ligand in three MOFs.2017, 56, 2936–2940; (b) Wang, K.; Tian, X.; Jin, Y.; Sun, J.; Zhang, Q. Heterometallic hybrid open frameworks: synthesis and application for selective detection of nitro explosives.2017, 17, 1836–1842.

(18) (a) Lin, X. M.; Niu, J. L.; Wen, P. X.; Pang, Y.; Hu, L.; Cai, Y. P. A polyhedral metal-organic framework based on supramolecular building blocks: catalysis and luminescent sensing of solvent molecules.2016, 16, 4705–4710; (b) Zhang, S. R.; Du, D. Y.; Qin, J. S.; Li, S. L.; He, W. W.; Lan, Y. Q.; Su, Z. M. 2D Cd(II)-lanthanide(III) heterometallic-organic frameworks based on metalloligands for tunable luminescence and highly selective, sensitive, and recyclable detection of nitrobenzene.2014, 53, 8105–8113.

(19) (a) Hu, Z. C.; Deibert, B. J.; Li, J. Luminescent metal-organic frameworks for chemical sensing and explosive detection.2014, 43, 5815?5840; (b) Nagarkar, S. S.; Joarder, B.; Chaudhari, A. K.; Mukherjee, S.; Ghosh, S. K.Highly selective detection of nitro explosives by a luminescent metal-organic framework.2013, 52, 2881?2885.

9 October 2017;

11 January 2018 (CCDC 1528962 for 1 and 1528963 for 2)

① This work was supported by the Foundation of State Key Laboratory of Coal Conversion (No. J17-18-611) and the National Natural Science Foundation of China (No. 21676258)

. Hu Tuo-Ping, born in 1969, professor, majoring in coordination chemistry. E-mail: hutuopingsx@126.com

10.14102/j.cnki.0254-5861.2011-1841