Experimental Studies and Mechanism Analysis of High-Sensitivity

Article pubs.acs.org/JPCC

Experimental Studies and Mechanism Analysis of High-Sensitivity Luminescent Sensing of Pollutional Small Molecules and Ions in Ln4O4 Cluster Based Microporous Metal−Organic Frameworks Jing-Min Zhou, Wei Shi,* Hui-Min Li, Han Li, and Peng Cheng* Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (MOE) and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, P. R. China S Supporting Information *

ABSTRACT: Two new isostructural 3D lanthanide metal− organic frameworks (Ln-MOFs) {[Ln4(μ3OH)4(BPDC)3(BPDCA)0.5(H2O)6]ClO4·5H2O}n (Ln = Tb (1) and Gd (2), BPDC2− = 3,3′-dicarboxylate-2,2′-dipyridine anion and BPDCA2− = biphenyl-4,4′-dicarboxylate anion) based on cubane-shaped [Ln4(μ3-OH)4]8+ clusters were successfully synthesized and fully characterized. There are two kinds of micropores with dimensions of 3.0 × 7.0 Å2 along the b-axis and 4.5 × 5.5 Å2 along the c-axis in the cationic framework. Ln-MOF 1 exhibits an intensive green luminescence triggered by the efficient antenna effect of ligands under UV light. Luminescent studies illustrate that Ln-MOF 1 could be an efficient multifunctional luminescent material for high-sensitivity sensing of small organic molecules, metal cations, and anions, especially for benzene and acetone, Cu2+, and CrO42−. The mechanism of the sensing properties was studied in detail as well. Additionally, this cationic framework also displays fast capture of pollutant CrO42− by anion exchange.

1. INTRODUCTION As a new type of porous material, metal−organic frameworks (MOFs) have been given considerable attention due to their great potentials, gas storage/separation,1 catalysis,2 and sensing.3 For sensing applications, lanthanide MOFs (LnMOFs) are more attractive because Ln-MOFs, especially Eu and Tb-MOFs, have sharp and characteristic emissions as well as long luminescent lifetimes.4 Since the unique luminescent mechanism of Ln-MOFs involves ligand-to-metal energy transfer (LMET), their emission intensities can be tuned by both substrate−metal and substrate−ligand interactions.5 With the development of modern society and industry, hazardous chemicals, like toxic ions and organic small molecules, are increasingly released from industrial facilities and other anthropogenic activities, which cause adverse effects on human health and the environment. Environmental pollutants, such as poisonous gases, oragnic solvent vapors, heavy metals, and anions, have both acute and chronic effects on human health and consequently lead to heart attacks, lung cancer, hepatosis, and other serious diseases.6 It is of great challenge and significance to indentify and monitor these environmental pollutants directly detected by the eyes via the development of advanced materials. Considering the intense luminescent signal and visible luminescent colors, Ln-MOFs could be good candidates as luminescent sensing materials for environmental pollutants. To explore the luminescent properties of Ln-MOFs in sensing, luminescent Ln3+ centers and judicious selected ligands are keys to obtain luminescent Ln-MOFs with proper porosity © 2013 American Chemical Society

and functional groups to provide potential open Lewis acid or base sites for specific host−guest interactions that can tune the luminescent properties. There are several reported Ln-MOFs for sensing functions highlighting the significance of the luminescent MOFs, as summarized in Table 1. Importantly, Eu(BTC),5a Tb(BTC),5b and Eu(pdc)1.55c reported by the Chen groups exhibit interesting sensing of organic smallmolecule solvents, anions, and metal cations, respectively. The porosity and potential open metal/organic group sites within Ln-MOFs have played a significant role on their sensing functionality, like open Eu3+ sites for small molecule-sensing, hydrogen bonding interactions for F−, and open Lewis basic pyridyl sites for Cu2+. As our continuous work on the luminescent sensing function of microporous MOFs,3e,f,7 herein we report interesting LnMOFs {[Ln4(μ3-OH)4 (BPDC)3(BPDCA) 0.5(H 2O) 6 ]ClO4· 5H2O}n (Ln = Tb (1 or 1a·5H2O) and Gd (2), BPDC2− = 3,3′-dicarboxylate-2,2′-dipyridine anion and BPDCA2− = biphenyl-4,4′-dicarboxylate anion) based on cubane-shaped [Ln4(μ3-OH)4]8+ secondary building units (SBUs). Two types of micropores with dimensions of 3.0 × 7.0 Å2 along the b-axis and 4.5 × 5.5 Å2 along the c-axis exist in the framework. Except the counteranion of ClO4−, there are potential Lewis base sites, the uncoordinated pyridyl N atoms, providing a platform for luminescent sensing research. Ln-MOF 1 exhibits highReceived: October 1, 2013 Revised: December 3, 2013 Published: December 10, 2013 416

dx.doi.org/10.1021/jp4097502 | J. Phys. Chem. C 2014, 118, 416−426

The Journal of Physical Chemistry C

Article

2. EXPERIMENTAL SECTION Materials and Methods. H2BPDC and terbium(III) perchlorate hexahydrate were prepared by the literature methods,8 and the other chemicals purchased were of reagent grade and used without further purification. Analyses for C, H, and N were carried out on a PerkinElmer 240 CHN elemental analyzer. IR spectra were recorded in the range 400−4000 cm−1 on a Bruker TENOR 27 spectrophotometer using KBr pellets. Powder X-ray diffraction measurements were recorded on a Rigaku D/Max-2500 X-ray diffractometer using Cu Kα radiation. TGA were performed on a Labsys NETZSCH TG 209 Setaram apparatus with a heating rate of 10 °C/min in a nitrogen atmosphere. UV−vis spectroscopic studies were collected on a Jasco V-570 spectrophotometer to monitor the exchange progress. ICP data were obtained on a ICP-9000(N +M) inductively coupled plasma emission spectrometer. X-ray photoelectron spectra were recorded on an Axis Ultra DLD Xray photoelectron spectroscopy of Kratos Analytical Ltd. Atomic absorption spectra were determined on a Hitachi 180-80. Synthesis of {[Ln4(μ3-OH)4(BPDC)3(BPDCA)0.5(H2O)6]ClO4·5H2O}n (Ln = Tb (1 or 1a·5H2O) and Gd (2)). A mixture containing H2BPDC (0.20 mmol, 0.0488 g), 4,4′H2BPDCA (0.10 mmol, 0.0242 g), NaOH (0.80 mmol, 0.0320 g), and Ln(ClO4)3·6H2O (0.40 mmol) in 8 mL of H2O and 2 mL of EtOH was stirred for several minutes at room temperature. The resulting suspension was put into a 25 mL Teflon-lined stainless steel reactor at 120 °C for 72 h, and then the reaction system was slowly cooled to room temperature. Colorless block-shaped single crystals suitable for X-ray data collection were obtained by filtration, washed with H2O, and air-dried. Yield: 23% and 20% based on H2BPDC for 1 and 2, respectively. Elemental analysis. Found (calcd) for Tb4C43H48N6O33Cl (1): C, 27.60 (27.95); H, 2.78 (2.62); N, 4.97 (4.55). Gd4C43H48N6O33Cl (2): C, 28.40 (28.05); H, 2.91 (2.63); N, 4.51 (4.56). IR bands (KBr, ν/cm−1) for 1: 3398 (br), 1592 (vs), 1457 (s), 1393 (s), 1161 (m), 1105 (m), 1054 (s), 851 (m), 767 (s), 688 (s), 536 (s), 424 (m). 2: 3391 (br), 1601 (vs), 1456 (s), 1399 (s), 1156 (m), 1108 (m), 1061 (s), 852 (m), 772 (s), 691 (s), 543 (s), 423 (m). Preparation of 1a and 1a-Dye. A sample of 1 (1a·5H2O) was heated at 100 °C in the oven for 24 h to afford 1a. Elemental analysis. Found (calcd) for Tb4C43H38N6O28Cl (1a): C, 29.60 (29.38); H, 2.08 (2.18); N, 4.77 (4.78). The FTIR spectrum of 1a is similar to that of 1, demonstrating that the basic framework is retained after channel dehydration, which was confirmed by the PXRD result. Dehydrated sample 1a was soaked ovenight in a ethanol solution of 10−2 M dye of 4,4′azpy (4,4′-azobispyridine). The resulting colored sample was washed with ethanol thoroughly until supernatant was colorless and light orange sample 1a-Dye was obtained through drying at 100 °C in the oven. Then 1a and 1a-Dye were analyzed by TGA. Single-Crystal Structural Characterization. Diffraction intensity data of 1 and 2 were collected on a Agilent Technologies SuperNova single-crystal diffractometer at 293(2) K equipped with graphite-monochromatic Mo Kα radiation (λ = 0.710 73 Å). The structures were solved by direct methods (SHELXS) and refined by full matrix least-squares techniques (SHELXL) with anisotropic thermal factors for all non-hydrogen atoms. Theoretical models fixed the hydrogen

Table 1. Selected Luminescent Ln-MOFs Materials for Sensing Functionality Ln-MOFs luminescent materials Eu(BTC)a [Tb(FDA)1.5(DMF)]b Yb(BPT)(H2O)c Eu3(MFDA)4(NO3)(DMF)3d Eu2(BDC)3(H2O)2e Eu(pdc)1.5f Eu2(FMA)2(OX)g {[Ln(PDA)3Mn1.5(H2O)3] (Ln = Eu or Tb)h {[Dy(PDA)3Mn1.5(H2O)3] [Ln−Fe(II)] (Ln = Eu or Tb) [Eu2L3(H2O)4]i Tb(BTC) Eu0.0069Tb0.9931−DMBDCj

luminescent substrates

ref

organic small molecules organic small molecules small molecules nitro explosives nitroaromatic explosives Cu2+ Cu2+ Zn2+

5a 7c 3n 3w 3o

Mg2+ Mg2+ DMF vapor F− temperature

3f 7a 3r 5b 3q

5c 3j 3e

a

BTC = benzene-1,3,5-tricarboxylate. bFDA = furan-2,5-dicarboxylate. BPT = biphenyl-3,4′,5-tricarboxylate. dMFDA = 9,9-dimethylfluorene-2,7-dicarboxylate. eBDC = benzene-1,4-dicarboxylate. fpdc = pyridine-3,5-dicarboxylate. gFMA = fumarate, OX = oxalate. hPDA = pyridine-2,6-dicarboxylate. iL = 2′,5′-bis(methoxymethyl)-[1,1′:4′,1″terphenyl]-4,4″-dicarboxylate. jDMBDC = 2,5-dimethoxy-1,4-benzenedicarboxylate. c

sensitivity sensing of pollutants organic small molecules, metal cations, and anions (Scheme 1). This work possesses significant Scheme 1. Schematic Diagram of Synthetic Routes

potential for detecting indoor air and water pollutants through a high-selective and easy-to-use sensor as well as detection of trace amounts of metal cations, especially for Cu2+ ions, which is one of the most essential and important metal ions in living biological systems. Further luminescent study and mechanism analysis will enlighten us to rational design and construct luminescent MOFs materials through proper ligand selection for the high-selective sensing of the substrate by substrate− ligand interaction. 417



Article

Figure 1. Structural analysis of Ln-MOF 1: (a, b) distorted cubane-shaped core unit [Tb4(μ3-OH)4]8+ surrounded by six BPDC2− and one BPDCA2− ligands, view the linkages between cubane-shaped core units (c) along the b-axis and (d) along the c-axis, (e) the 3D framework of 1 along the b-axis. Color codes: yellow for Tb, bright green/dark green/violet for C, blue for N, and red for O.

Figure 2. Ln-MOF 1 with two types of micropores: (a) 3.0 × 7.0 Å2 along the b-axis and (b) 4.5 × 5.5 Å2 along the c-axis. Water molecules are removed for clarity.

atoms and all calculations were performed using the program package Olex2.9 Luminescent Experiments. The luminescent spectra were measured on a Varian Cary Eclipse fluorescence spectrophotometer. The luminescent decay curves and low-temperature spectra were obtained from an Edinburgh fluorescence spectrometer FLS920P using a μF920H pulsed xenon flashlamp. The luminescent properties were investigated in both the solid state and suspensions at room temperature. The suspensions of 1a/solvent were prepared by introducing each sample (3.0 mg) as a powder into different solvents (each 2.0 mL) and were then vigorously agitated using ultrasound. For the experiments of sensing small molecules, different amounts of benzene and acetone were added into a standard suspension of 1a/ethanol, while the concentration of the

lanthanide ions was kept constant. The PL spectra of the suspensions were measured after aging overnight. Luminescent properties of 1a/M and 1a/anion were investigated in the solid state. 1a/M or 1a/anion was prepared as a powder by introducing 1a powder (25 mg) into aqueous solution (6.00 mL) of MClx (M = Na+, K+, Mg2+, Ca2+, Cr3+, Mn2+, Fe2+, Co2+, Cu2+, Zn2+, or Cd2+) or anion (anion = F−, Cl−, Br−, I−, NO3−, SO42−, CO32−, CrO42−, or OAc−) at various concentrations (10−4−10−2 M). After treatment, the powder was obtained by filtration, washing, and drying in the air.

3. RESULTS AND DISCUSSION 3.1. Crystal Structure. Since Ln-MOFs 1 and 2 are isostructural, the single crystal structure of 1 is only analyzed here. Ln-MOF 1 crystallizes in monoclinic space group C2/c, 418



Article

The energy transfer from the ligands to Tb3+ center magnified the f−f transition significantly.15 Compared the photoluminescent (PL) spactra of 1 with 1a, the emission intensities of 1a are enhanced because of the removing of channel H2O molecules.16 Before further luminescent sensing measurement, study about the porosity of 1a was performed by measuring dye uptake.17 The TGA analyses indicated Ln-MOF 1a adsorbed 6.5 wt % 4,4′-azpy (Figure S4). The experimental porosity of 1a was compatible with the result of single crystal data and provided suitable platform for further luminescent sensing of solvents and ions. 3.2.1. Organic Small Molecule Sensing. Organic pollutants are increasingly concerned because of their environmental biological hazards.18 As a promising new type of sensing materials, luminescent MOFs have been explored to detect organic small pollutants in the environmental and biological sysytem, in view of the obvious luminescent signals and eyeable luminescent colors induced by additional organic small molecules.3,5a To examine the potential of 1a for the sensing of small organic molecules, its luminescent properties in different solvent suspensions were investigated. Before the luminescent measurements, PXRD patterns illustrated good solvent-stability of 1a treated by different solvents (Figure S5). As shown in Figure 4, its PL spectra are significantly dependent on the solvent molecules, particularly in the case of benzene and acetone, which exhibit clearly enhancing and quenching effects, respectively. The relative change of the emission color of 1a after treatment by benzene and acetone are shown in

featuring a three-dimensional (3D) framework based on the unique cubane-shaped [Tb4(μ3-OH)4]8+ cluster as a secondary building unit (SBU).10 There are four crystallographically unique eight-coordinated Tb3+ ions in the asymmetric unit (Figure S1). The semiquantitative method of polytopal analysis11 indicates that the coordination geometries of Tb1, Tb2, and Tb4 can be viewed as slightly distorted triangular dodecahedrons, while the coordination geometry of Tb3 can be described as a slightly distorted square antiprism (Table S1). The Tb−O bond lengths vary from 2.265 to 2.502 Å. Four triply bridging μ3-hydroxyl oxygen atoms link four Tb3+ ions to form a cubane-shaped tetranuclear [Tb4(μ3-OH)4]8+ SBU, which is surrounded by six BPDC2− and one BPDCA2−. The adjacent distorted cubane-shaped core units are connected through four (κ1-κ1)-(κ1-κ1)-μ4-BPDC2−, two (κ2)-(κ1-κ1)-μ3BPDC2−, and one (κ1-κ1)-(κ1-κ1)-μ4-BPDCA2− along different directions to form a 3D cationic framework (Scheme S1 and Figure 1) with ClO4− as counteranions. There are two types of micropores of about 3.0 × 7.0 Å2 along with the b-axis and 4.5 × 5.5 Å2 along with the c-axis excluding the van der Waals radii of the channel-wall atoms, and these micropores are filled with the water molecules and counteranions (Figure 2). In order to simplify this cationic framework, the network topology has been analyzed by the freely available computer program TOPOS.12 If each [Tb4(μ3-OH)4]8+ cluster is considered as a six-connected node which is linked with six BPDC2− and one BPDCA2−, and all of BPDC2− and BPDCA2− serve as bridging linkers, the structure can be viewed as a 6connected pcu net with the point symbol {412·63} (Figure S2). As far as we know, the 6-connected pcu net with cubane-shaped clusters as nodes is extremely rare, although pcu net is common in the MOFs chemsitry.13 3.2. Luminescent Properties. Desolvated 1a was obtained by heating Ln-MOF 1 (1a·5H2O) at 100 °C for 24 h (Experimental Section). PXRD of 1a is almost identical to that of 1, demonstrating that the basic framework of 1 is retained after activation (Figure S3). The excitation and emission spectra of 1 and 1a are shown in Figure 3. The excitation peak around 313 nm can be ascribed to the absorption of the ligands. When excited at 300 nm, four characteristic emission bands of 489, 544, 583, and 622 nm were observed in the visible region coming from 5D4 → 7FJ (J = 6−3) transitions of Tb3+ ion.14

Figure 4. (a) Suspension-state PL spectra and (b) the relative intensities of 5D4 → 7F5 at 544 nm for 1a dispersed in different organic solvents when excited at 300 nm.

Figure 3. Excitation spectrum of 1 and comparison of the emission spectra for 1 and 1a. 419



Article

Scheme S2, and their emission color can be quantitatively characterized by using the color coordinates according to the Commission Internationale de L’Eclairage (CIE) 1931 diagram.19 The CIE XYZ color space was derived from a series of experiments done in the late 1920s by William19a and John,19b and the coordinates x and y represent red and green color components, respectively. The FT-IR spectrum of 1a/ acetone (powder of 1a treated by acetone) presents obvious infrared absorption peak around 1700 cm−1 that belong to ν(CO) from acetone, and the frame vibration absorption of benzene ring in 1a/benzene is overlapped with the ligands around 1400 and 1600 cm−1 (Figure S6). Such solventdependent luminescent property is of interest for sensing of benzene and acetone solvent molecules, which are very harmful to human beings. These harmful small-molecule solvents have been examined in detail further. Ln-MOF 1a was dispersed in EtOH as the standard suspension,3n,v,5a,7 while the content of benzene/acetone was gradually increased to detect the emissive response. It was found that the luminescent intensity of the suspension of 1a increased with the addition of benzene (Figure S7a). The enhancement was nearly proportional to the concentration of benzene. On the other hand, addition of acetone to the suspension of 1a resulted in a significant decrease of the luminescent intensity, which almost disappeared at an acetone content of 21 vol % (Figure S7b). The decreasing trend of the luminescent intensity of the 5D4 → 7F5 transition of Tb3+ at 544 nm versus the volume ratio of acetone could be well fitted with a first-order exponential decay (Figure S8), indicating that luminescent quenching of 1a by acetone is diffusion-controlled. Comparing the luminescent lifetimes, benzene clearly increase the lifetime of 1a, whereas acetone affects it oppositely (Figure S9). 3.2.2. Ions Sensing. Ln-MOF 1a was treated by different amounts of MClx (M = Na+, K+, Ca2+, Mg2+, Mn2+, Zn2+, Cd2+, Cr3+, Fe2+, Ni2+, Co2+, or Cu2+) aqueous solution to form the metal ion loaded 1a/M powder solids. These metal ions loaded frameworks are almost identical to the as-synthesized one and hence suitable for further luminescent studies (Figure S10). The luminescent intensity of 1a/M is significantly dependent on metal ion. Alkaline metal ions and alkaline-earth metal ions have a slight effect on the luminescent intensity, while others have different levels of quenching effects on the luminescent intensity, especially Cu2+ with the most significant quenching effect (Figure 5). The luminescent intensity of 1a/Cu2+ activated from 10−2 M CuCl2 aqueous solution is more than 4 times weaker than that of the original sample. Comparing the sensing of Cu2+ ions, the sensitivity of 1a for the sensing of Cu2+ is much higher than that of the reported Eu(PDC)1.55c and slightly lower than that of Eu2(FMA)2(OX)(H2O)4.3j Atomic absorption spectroscopy (AAS) and inductively coupled plasma (ICP) measurements demonstrate that the content of copper in 1a/Cu2+ sample is about 3.12% (AAS) and 2.58% (ICP). Such a high sensitivity can be definitely used to easily detect a small amount of Cu2+ ion by naked-eye observation, since the emissive visible green light from 1a/Cu2+ is obviously darker than that from 1a under UV light (Scheme S2) and the luminescent lifetime of 1a/Cu2+ is less than 1a (Figure S9). This quenching effect can be approximatively illustrated by the Stern−Volmer equation: I0/I = 1 + Ksv[M].20 The values I0 and I are the luminescent intensity of metal-ion-free 1a/H2O (1) and metal-ion-incorporated 1a/M, respectively. [M] is the

Figure 5. (a) Solid PL spectra of 1a treated by different concentrations of CuCl2 aqueous solution and (b) comparison of the 5D4 → 7F5 transition intensity of 1a treated by 10−2 M MClx (M = Na+, K+, Ca2+, Mg2+, Mn2+, Zn2+, Cd2+, Cr3+, Fe2+, Ni2+, Co2+, Cu2+) aqueous solutions.

molar concentration of the metal ion, and Ksv is the quenching effect coefficient of the metal ion. It is assumed that the decrease in luminescent intensity is proportional to the concentration of the metal ion. The values of Ksv can be calculated from the luminescent data (Table S2). Cu2+ ion with the largest Ksv value 344.9 ± 10.2 M−1 demonstrates its obvious quenching effect on the luminescent intensity of 1. Due to the high selective and sensitive sensing of Cu2+ in aqueous solution of 1a, the sensing function of 1a was further performed under simulated physiological conditions. A physiological aqueous buffer solution was well established by preparing 0.02 M 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) aqueous solution with pH 7 to simulate the living cell solution.21 1a was immersed in the simulated physiological aqueous solution containing different amounts of MCl2 (M = Cr3+, Fe2+, Ni2+, Co2+, Cu2+) to form 1a/M@ HEPES powder samples for PXRD and luminescent studies. The PXRD patterns of the activated MOFs 1a/M@HEPES have slight difference with the original one (Figure S11), illustrating that the basic framework of 1a almost keeps unchanged in such a simulated physiological aqueous solution. The sensing function of 1a for Cu2+ ion in this simulated physiological aqueous solution is comparable to that of 1a observed in pure aqueous solution, indicating the potential of 420



Article

Figure 6. (a) Solid PL spectra of 1a treated by different concentrations of K2CrO4 aqueous solution and (b) comparison of the 5D4 → 7F5 transition intensity of 1a treated by 10−2 M anion (F−, Cl−, Br−, I−, SO42−, CO32−, NO3−, CrO42−, and OAc−) aqueous solutions.

Figure 7. (a) UV−vis spectra of the K2CrO4 aqueous solution during exchange with 1a and (b) PL spectra of 1a during exchange with K2CrO4 at room temperature (1a/ K2CrO4 with 2/1 molar ratio).

cationic framework.23 Therefore, the exchange and capture capacity of 1a with CrO42− anion was further studied. When 0.01 mmol of 1a was placed into an aqueous solution containing 0.005 mmol of K2CrO4, the exchange process was carried out at room temperature with slow stirring. The exchanged solution was detected by liquid UV−vis spectroscopy at intervals. It is observed that the absorption intensity of the main characteristic band of CrO42− in the K2CrO4 solution around 370 nm distinctly decreased as time was going on,24 demonstrating that CrO42− in solution was gradually exchanged into the channel of 1a with original anion ClO4−. By exchanging for 12 h, the UV−vis absorption intensity of CrO 4 2− in solution almost kept unchanged, and the corresponding concentration reduced by about 54% (Figure 7a). Hence, the capture capacity of 1a was 0.3 mol/mol (20.09 mg/g), verified by AAS and ICP results (Table S3). With the exchange process, the luminescent intensity of 1a gradually decreased, coinciding with the quenching effect of CrO42− (Figure 7b). Compared with the reported works,23d,25 1a has relative fast exchange and a high capture capacity of CrO42−

1a for the sensing of Cu2+ ion in a biological system (Figure S12). Simultaneously, various anions were selected to carry out the anion-sensing function in view of the cationic framework and porosity of 1a. 1a was soaking in different anion aqueous solutions (anion = F−, Cl−, Br−, I−, SO42−, CO32−, NO3−, CrO42−, and OAc−), and anion-exchange samples were obtained. The original framework almost kept unchanged as confirmed by PXRD (Figure S13). The luminescent measurements illustrate that the difference of anions has a great influence on the luminescent intensity of 1a. Remarkably, CrO42− has the largest quenching effect on the luminescent emission (Figure 6) and has reduced the luminescent lifetime of 1a (Figure S9). CrO42− as a toxic anion is badly harmful to human health and environment and can be accumulated in the living organisms leading to kinds of serious diseases.22 Although several literatures have been reported about the exchange of anions based on MOFs, it is still rare to explore the exchange and capture of pollutant anions using a lanthanide luminescent 421



Article

Figure 8. (a) Absorption spectra of Ln-MOF 1 and target solvents (benzene and acetone) in n-hexane and (b) comparison of PL spectra of 1a in benzene and acetone with EtOH as a standard.

Scheme 2. Simplified Schematic Diagrams Showing (a) Ligand−Metal Energy Transformation (LMET) for Luminescent Emission (1ππ* and 3ππ* are the Singlet State and Triplet State of Ligands) and (b) the Influence of Benzene and Acetone on LMET

in the channel are gradually replaced by benzene and acetone, leading to the luminescent enhancing and quenching, respectively.5a,7d To deeply understand the luminescent response induced by benzene and acetone, the UV−vis spectra of benzene and acetone are measured in n-hexane (Figure 8a). It is obvious that the absorption peak of ligands within LnMOF 1 are almost mantled by the wide absorption of acetone while the absorption band of benzene is located at blue side of the absorption peaks of ligands and partially overlaps with the absorption band of ligands. When 1a/benzene and 1a/acetone suspensions are excited at 300 and 340 nm, which are not at the UV−vis absorption region of themselves, the luminescent intensities are obviousely enhanced and quenched, respectively, indicating the LMET efficiency is affected by the interaction of ligands with solvents in the channel and thus leads to different luminescent response (Figure 8b). Considering the oppsite luminescent response, it can be speculated that two different LMET machanisms in benzene and acetone systems.

(Table S4). Subsequently, the influence of the temperature factor on the exchange ratio also has been studied. The UV−vis absorption intensities of CrO42− in solutions at 40 and 60 °C decreased more quickly than that at room temperature (∼20 °C) within first half an hour, indicating that the exchange ratio of CrO42− with ClO4− in 1a was directly rational to the temperature (Figure S14). After exchanging for 12 h, the concentrations of CrO42− in solutions decreased by 62% and 68% for 40 and 60 °C, respectively, indicating that the exchange ratio of CrO42− with ClO4− in 1a can obviously be improved by raising the temperature. 3.3. The Mechanism of Luminescent Response. Up to date, the mechanism for such enhancing and quenching effects of small solvent molecules is still not very clear. Nevertheless, the influence of the guest solvents on ligand−metal energy transformation (LMET) definitely plays an important role, since the efficiency of LMET is crucial to determine the emission of lanthanide.26 It is expected that the guest molecules 422



Article

Figure 9. (a) UV−vis absorption of aqueous solution containing different metal cations and (b) PL spectra of Ln-MOF 1a treated by different metal cation aqueous solutions.

Figure 10. (a) XPS for 1a, 1a/Cu2+, and 1a/CrO42− and (b) N 1s XPS for 1a and 1a/Cu2+.

A simplified ligand (1ππ*) → ligands (3ππ*) → Tb* energy transformation is shown in Scheme 2a. When the energy gap ΔE(1ππ* → 3ππ*) between the singlet-state (1ππ*) and tripletstate (3ππ*) energy levels of the ligands is greater than the lowest value of 5000 cm−1, the intersystem crossing process will be effective according to Reinhoudt′s empirical rule.27a The singlet-state energy level of the ligands in Ln-MOF 1 was 33 333 cm−1 (300 nm) based on the UV−vis absorption spectra of ligands (Figure S15a). The triplet-state energy (3ππ*) level of the ligands was found to be 22 936 cm−1 (436 nm) based on the low-temperature (77 K) phosphorescence spectrum of LnMOF 2 (Figure S15b).27b,c Therefore, the energy gap ΔE(1ππ* → 3ππ*) is 10 397 cm−1, indicating that the intersystem crossing process in Ln-MOF 1 is effective. The energy transfer from 3ππ* to 5D4 (18 382 cm−1) of Tb3+ contributed directly to the luminescence of Ln-MOF 1 (Figure S15c).27a,28 Benzene may have similar excited energy level with ligands BPDC2− or BPDCA2− because of their parallel benzene and pyridine rings. The overlap between the UV−vis absorption of benzene and ligands is likely to lead to the energy transformation from

benzene to ligands, which will increase in the efficiency of intersystem crossing 1ππ* → 3ππ* and then results in the enhance of LMET. Combined with the UV absorption and luminescent spectra, it is evident that the energy transfer happened between ligands and acetone in view of the luminescent response by addition of acetone.29 Due to the physical intermolecular interations between ligands and acetone, such as ion−dipole, dipole−dipole, dipole−induced dipole, and hydrogen bonding,30 the energy absorbed by ligands BPDC2− or BPDCA2− is transferred to acetone molecules, resulting in decrease in the efficiency of intersystem crossing 1ππ* → 3ππ* (Scheme 2b). Additionally, the wide UV−vis absorption of acetone itself can directly hinder the UV−vis absorption of ligands within Ln-MOF 1 and thus reduce the LMET efficiency, leading to the quenching effect on the luminescent intensity. This mechanism of luminescent reduction induced by metal ions can be proposed that metal ions weakly interact with potential Lewis basic sites of Ln-MOF 1 and affects the efficiency of energy transformation from ligands to metal 423



Article

Figure 11. (a) Liqiud UV−vis absorption of different anions and (b) PL spectra of Ln-MOF 1a treated by different anion aqueous solutions.

centers.31 The weak bonding between Cu2+ and organic component is likely to partly quench the excited state 1ππ* and/or 3ππ* of ligands and then reduce the energy transfer efficiency from ligands BPDC2− and BPDCA2− to Tb3+ luminescent center. Alkali and alkaline earth metal ions with saturated electron configuration almost have no effect on the luminescent intensity and the small quenching effect of Zn2+/ Cd2+ can result from the weak interation of metal ions with Lewis basic sites. Other metal ions have different quenching effects on the luminescent intensity because of their unsaturated electron configuration. When 330 nm at which no UV−vis absorption peak from metal ion is chosen as excited wavenumber, the luminescent intensity is also reduced by metal ion (Figure 9), further demonstrating that weak interactions of metal ions with potential Lewis basic sites within this MOF play an important role in the luminescent response. The microporosity of 1a might as well enhance the sensing of Cu2+ ions via the interactions of Cu2+ ions with the carboxylate and/or pyridyl Lewis basic sites on the pore surfaces. To confirm this hypothesis, X-ray photoelectron spectroscopy (XPS) was performed. The N 1s peak from free pyridyl nitrogen atoms at 397.3 eV in 1a is shifted to 397.9 eV induced by addition of Cu2+ in 1a/Cu2+, suggesting the weak interaction between metal cations and pyridyl Lewis basic sites in 1a/Cu2+ (Figure 10). Such interactions of Cu2+ ions with pyridyl Lewis basic sites decrease the antenna efficiency of ligands to magnify the f−f transitions of Tb3+, leading to the quenching of the luminescence. The luminescent signal induced by anion can be partially attributed to the UV−vis absorption of anion itself (Figure 11a). Further studies show that the luminescent intensity is also reduced by anion when the excited wavenumber was selected at which no UV−vis absorption peak from anions is chosen. As shown in Figure 11b, the luminescent intensity of 1a treated by NO3− is obviously weakened when excited at 261 nm. For other anions, the luminescent intensities of activated samples correspondingly decrease when excited at 312 nm. This result indicates that the weak interaction of different anions with the cationic framework may influence the efficiency of LMET and lead to the change of the luminescent signals. Especially for the sample treated by CrO42−, its luminescent intensity exhibit very remarkable reduction when excited at different wavelength,

suggesting 1a as a greatly promising and high-sensitivity luminescent sensor for pollutant CrO42−.

4. CONCLUSION In summary, a novel lanthanide luminescent cationic framework material has been successfully synthesized and characterized. There are two kinds of micropores in this framework. The IR, PXRD, UV, XPS, and luminescent measurements demonstrate that this framework can be explored as potential multifunctional luminescent material for sensing of organic small-molecule solvents, metal cations, and anions, especially for benzene and acetone, Cu2+, and CrO42−. In addition, this cationic framework material exhibits relative fast exchange and high capture capacity of CrO42−, which is significant to monitor and reduce CrO42− pollutant in the environment. Further study and speculation of the mechanism illustrate that the majority of the luminescent response to solvents and ions can result from the interaction of substrate (like benzene, acetone, Cu2+, or CrO42−) with ligands, that shift the excited state energy level of ligands, thus affect the LMET efficiency, and consequently lead to different luminescent emission. The luminescent mechanism will inspire us to build lanthanide luminescent MOFs material through proper ligand and high-selective sensing of the substrate by substrate−ligand interaction. More efforts are needed to design luminescent Ln-MOFs materials with pores and proper organic or metal open sites for targeting substrates.

■

ASSOCIATED CONTENT

S Supporting Information *

Structural analysis (Figures S1 and S2, Scheme S1, and Table S1); PXRD patterns (Figures S3, S5, S10, S11, and S13); luminescent color change and CEI chromaticity diagram (Scheme S2); IR spectra (Figure S6); PL spectra (Figures S7, S12, and S15−21); the fitting of PL intensity (Figure S8); the lifetimes (Figure S9); quenching effect coefficients of metal ions (Table S2); AAS and ICP results (Table S3); capture capacity of sorbents (Table S4); UV−vis spectra (Figures S14 and S15); TGA curves (Figures S4 and S22); crystal data and structural refinement details (Table S5). This material is available free of charge via the Internet at http://pubs.acs.org. 424



■

Article

(3) Sensing: (a) Allendorf, M. D.; Bauer, C. A.; Bhaktaa, R. K.; Houk, R. J. T. Chem. Soc. Rev. 2009, 38, 1330. (b) Chen, B. L.; Xiang, S. C.; Qian, G. D. Acc. Chem. Res. 2010, 43, 1115. (c) Cui, Y. J.; Yue, Y. F.; Qian, G. D.; Chen, B. L. Chem. Rev. 2012, 112, 1126. (d) Albrecht, M.; Lutz, M.; Spek, A. L.; Koten, G. Nature 2000, 406, 970. (e) Zhao, B.; Chen, X.-Y.; Cheng, P.; Liao, D.-Z.; Yan, S.-P.; Jiang, Z.-H. J. Am. Chem. Soc. 2004, 126, 15394. (f) 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. (g) Huang, Y.; Ding, B.; Song, H.; Zhao, B.; Ren, P.; Cheng, P.; Wang, H.; Liao, D.; Yan, S. Chem. Commun. 2006, 42, 4906. (h) Lan, A.; Li, K.; Wu, H.; Olson, D. H.; Emge, T. J.; Ki, W.; Hong, M.; Li, J. Angew. Chem., Int. Ed. 2009, 48, 2334. (i) Lu, W.-G.; Jiang, L.; Feng, X.-L.; Lu, T.-B. Inorg. Chem. 2009, 48, 6997. (j) Xiao, Y.; Cui, Y.; Zheng, Q.; Xiang, S.; Qian, G.; Chen, B. Chem. Commun. 2010, 46, 5503. (k) Lu, Z.-Z.; Zhang, R.; Li, Y.-Z.; Guo, Z.-J.; Zheng, H.-G. J. Am. Chem. Soc. 2011, 133, 4172. (l) An, J.; Shade, C. M.; ChengelisCzegan, D. A.; Petoud, S.; Rosi, N. L. J. Am. Chem. Soc. 2011, 133, 1220. (m) Takashima, Y.; Martñez, V. M.; Furukawa, S.; Kondo, M.; Shimomura, S.; Uehara, H.; Nakahama, M.; Sugimoto, K.; Kitagawa, S. Nat. Commun. 2011, 2, 168. (n) Liu, S.; Xiang, Z.; Hu, Z.; Zheng, X.; Cao, D. J. Mater. Chem. 2011, 21, 6649. (o) Guo, Z.; Xu, H.; Su, S.; Cai, J.; Xiang, S.; Qian, G.; Xhang, H.; Keeffe, M. O.; Chen, B. Chem. Commun. 2011, 47, 5551. (p) Xu, H.; Liu, F.; Cui, Y. J.; Chen, B.; Qian, G. Chem. Commun. 2011, 47, 3153. (q) Cui, Y.; Xu, H.; Yue, Y.; Guo, Z.; Yu, J.; Chen, Z.; Gao, J.; Yang, Y.; Qian, G.; Chen, B. J. Am. Chem. Soc. 2012, 134, 3979. (r) Li, Y.; Zhang, S.; Song, D. Angew. Chem., Int. Ed. 2013, 125, 738. (s) Zhu, X.; Zheng, H.; Wei, X.; Lin, Z.; Guo, L.; Qiu, B.; Chen, G. Chem. Commun. 2013, 49, 1276. (t) Wang, J.-H.; Li, M.; Li, D. Chem. Sci. 2013, 4, 1793. (u) Mohapatra, S.; Rajeswaran, B.; Chakraborty, A.; Sundaresan, A.; Maji, T. K. Chem. Mater. 2013, 25, 1673. (v) Liu, G.-L.; Qin, Y.-J.; Jing, L.; Wei, G.-Y.; Li, H. Chem. Commun. 2013, 49, 1699. (w) Zhou, X.; Li, H.; Xiao, H.; Li, L.; Zhao, Q.; Yang, T.; Zuo, J.; Huang, W. Dalton Trans. 2013, 42, 5718. (4) (a) Alaoui, I. M. J. Phys. Chem. 1995, 99, 13280. (b) Choppin, G. R.; Petreman, D. R. Coord. Chem. Rev. 1998, 174, 283. (c) Werts, M. H. V.; Jukes, R.T. F.; Verhoeven, J. W. Phys. Chem. Chem. Phys. 2002, 4, 1542. (5) (a) Chen, B.; Yang, Y.; Zapata, F.; Lin, G.; Qian, G.; Lobkovsky, E. B. Adv. Mater. 2007, 19, 1693. (b) Chen, B.; Wang, L.; Zapata, F.; Qian, G.; Lobkovsky, E. B. J. Am. Chem. Soc. 2008, 130, 6718. (c) Chen, B.; Wang, L.; Xiao, Y.; Fronczek, F. R.; Xue, M.; Cui, Y.; Qian, G. Angew. Chem., Int. Ed. 2009, 48, 500. (6) (a) Harada, M. Crit. Rev. Toxicol. 1995, 25, 1. (b) Cohen, A. J.; Ross Anderson, H.; Ostro, B.; Pandey, K. D.; Krzyzanowski, M.; Kunzli, N.; Gutschmidt, K.; Pope, A.; Romieu, I.; Samet, J. M.; Smith, K. J. Toxicol. Environ. Health, Part A 2005, 68, 1301. (c) Kampa, M.; Castanas, E. Environ. Pollut. 2008, 151, 362. (d) Martinez, J. L. Environ. Pollut. 2009, 157, 2893. (7) (a) Chen, X.-Y.; Zhao, B.; Shi, W.; Xia, J.; Cheng, P.; Liao, D.-Z.; Yan, S.-P.; Hui, Z.-Z. Chem. Mater. 2005, 17, 2866. (b) Zhao, B.; Chen, X.-Y.; Chen, Z.; Shi, W.; Cheng, P.; Yan, S.-P.; Liao, D.-Z. Chem. Commun. 2009, 3113. (c) Zhao, X.-Q.; Zhao, B.; Shi, W.; Cheng, P. CrystEngComm 2009, 11, 1261. (d) Li, H.-H.; Shi, W.; Zhao, K.-N.; Niu, Z.; Li, H.-M.; Cheng, P. Chem.Eur. J. 2013, 19, 3358. (e) Zhou, J.-M.; Shi, W.; Xu, N.; Cheng, P. Inorg. Chem. 2013, 52, 8082. (8) (a) Kanungo, B. K.; Baral, M.; Bhattacharya, S.; Sahoo, Y. Synth. Commun. 2003, 33, 3159. (b) An, J. J.; Chen, Z. C. In Inorganic Compounds Synthesis Handbook; The Chemical Society of Japan (SCJ), Chemical Industrial Press: Tokyo, 1986; Vol. 2, p 258. (9) (a) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112. (b) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339. (10) (a) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319. (b) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Nature 2003, 423, 705.

AUTHOR INFORMATION

Corresponding Authors

*E-mail [email protected]; Fax (+86) 22-23502458; Tel +86-22-23503059 (W.S.). *E-mail [email protected]; Fax (+86) 22-23502458; Tel +86-22-23503059 (P.C.). Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We gratefully acknowledge the “973” program (2012CB821702), NSFC (21171100 and 90922032), and 111 Project (B12015).

■

REFERENCES

(1) Gas storage/separation: (a) Morris, R. E.; Wheatley, P. S. Angew. Chem., Int. Ed. 2008, 47, 4966. (b) Murray, L. J.; Dincă, M.; Long, J. R. Chem. Soc. Rev. 2009, 38, 1294. (c) Li, J.-R.; Kuppler, R. J.; Zhou, H.C. Chem. Soc. Rev. 2009, 38, 1477. (d) Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Science 2003, 300, 1127. (e) Maji, T. K.; Uemura, K.; Chang, H.-C.; Matsuda, R.; Kitagawa, S. Angew. Chem., Int. Ed. 2004, 43, 3269. (f) Matsuda, R.; Kitaura, R.; Kitagawa, S.; Kubota, Y.; Belosludov, R. V.; Kobayashi, R. C.; Sakamoto, H.; Chiba, T.; Takata, M.; Kawazoe, Y.; Mita, Y. Nature 2005, 436, 238. (g) Férey, G.; Mellot-Draznieks, C.; Serre, C.; Millange, F.; Dutour, J.; Surblé, S.; Margiolaki, I. Science 2005, 309, 2040. (h) Custelcean, R.; Gorbunova, M. G. J. Am. Chem. Soc. 2005, 127, 16362. (i) Rowsell, J. L. C.; Yaghi, O. M. Angew. Chem., Int. Ed. 2005, 44, 4670. (j) Chun, H.; Dybtsev, D. N.; Kim, H.; Kim, K. Chem.Eur. J. 2005, 11, 3521. (k) Pan, L.; Olson, D. H.; Ciemnolonski, L. R.; Heddy, R.; Li, J. Angew. Chem., Int. Ed. 2006, 45, 616. (l) Chen, B.; Liang, C.; Yang, J.; Contreras, D. S.; Clancy, Y. L.; Lobkovsky, E. B.; Yaghi, O. M.; Dai, S. Angew. Chem., Int. Ed. 2006, 45, 1390. (m) Sun, D.; Ma, S.; Ke, Y.; Collins, D. J.; Zhou, H.-C. J. Am. Chem. Soc. 2006, 128, 3896. (n) Pan, L.; Parker, B.; Huang, X.; Olson, D. H.; Lee, J.; Li, J. J. Am. Chem. Soc. 2006, 128, 4180. (o) Panella, B.; Hirscher, M.; Pütter, H.; Müller, U. Adv. Funct. Mater. 2006, 16, 520. (p) Furukawa, H.; Millerb, M. A.; Yaghi, O. M. J. Mater. Chem. 2007, 17, 3197. (q) Li, J. R.; Tao, Y.; Yu, Q.; Bu, X. H.; Sakamoto, H.; Kitagawa, S. Chem.Eur. J. 2008, 14, 2771. (r) Ma, S.; Wang, X.-S.; Yuan, D.; Zhou, H.-C. Angew. Chem., Int. Ed. 2008, 47, 4130. (s) Si, X.; Jiao, C.; Li, F.; Zhang, J.; Wang, S.; Liu, S.; Li, Z.; Sun, L.; Xu, F.; Gabelicad, Z.; Schicke, C. Energy Environ. Sci. 2011, 4, 4522. (t) Liu, S.; Sun, L.; Xu, F.; Zhang, J.; Jiao, C.; Li, F.; Li, Z.; Wang, S.; Wang, Z.; Jiang, X.; Zhou, H.; Yange, L.; Schic, C. Energy Environ. Sci. 2013, 6, 818. (u) Wilmer, C. E.; Farha, O. K.; Yildirim, T.; Eryazici, I.; Krungleviciute, V.; Sarjeant, A. A.; Snurr, R. Q.; Hupp, J. T. Energy Environ. Sci. 2013, 6, 1158. (2) Catalysis: (a) Ma, L.; Abney, C.; Lin, W. Chem. Soc. Rev. 2009, 38, 1248. (b) Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K. J. Am. Chem. Soc. 1994, 116, 1151. (c) Pan, L.; Liu, H.; Lei, X.; Huang, X.; Olson, D. H.; Turro, N. J.; Li, J. Angew. Chem., Int. Ed. 2003, 42, 542. (d) Hu, A.; Ngo, H. L.; Lin, W. J. Am. Chem. Soc. 2003, 125, 11490. (e) Hu, A.; Ngo, H. L.; Lin, W. Angew. Chem., Int. Ed. 2003, 42, 6000. (f) Wu, C.-D.; Hu, A.; Zhang, L.; Lin, W. J. Am. Chem. Soc. 2005, 127, 8940. (g) Cho, S.-H.; Ma, B.; Nguyen, S. B. T.; Hupp, J. T.; AlbrechtSchmitt, T. E. Chem. Commun. 2006, 42, 2563. (h) Wu, C.-D.; Lin, W. Angew. Chem., Int. Ed. 2007, 119, 1093. (i) Hwang, Y. K.; Hong, D.-Y.; Chang, J.-S.; Jhung, S. H.; Seo, Y.-K.; Kim, J.; Vimont, A.; Daturi, M.; Serre, C.; Férey, G. Angew. Chem., Int. Ed. 2008, 47, 4144. (j) Hong, D.-Y.; Hwang, Y. K.; Serre, C.; Férey, G.; Chang, J.-S. Adv. Funct. Mater. 2009, 19, 1537. (k) Ma, L.; Wu, C.-D.; Wanderley, M. M.; Lin, W. Angew. Chem., Int. Ed. 2010, 122, 8420. (l) Song, F.; Wang, C.; Lin, W. Chem. Commun. 2011, 47, 8257. (m) Vermoortele, F.; Vandichel, M.; de Voorde, B. V.; Ameloot, R.; Waroquier, M.; Speybroeck, V. V.; De Vos, D. E. Angew. Chem., Int. Ed. 2012, 51, 4887. 425



Article

(11) (a) Muetterties, E. L.; Guggenberger, L. J. J. Am. Chem. Soc. 1974, 96, 1748. (b) Drew, M. G. B.; Coord. Chem. Rev. 1977, 24, 179. (c) Zabrodsky, H.; Peleg, S.; Avnir, D. J. Am. Chem. Soc. 1992, 114, 7843. (d) Pinsky, M.; Avnir, D. Inorg. Chem. 1998, 37, 5575. (12) (a) Blatov, V. A. Multipurpose crystallochemical analysis with the program package TOPOS. IUCr Comp. Comm. Newsl. 2006, 7, 4. Available at http://iucrcomputing.ccp14.ac.uk/iucr-top/comm/ccom/ newsletters/2006nov/. (b) Blatov, V. A. http://www.topos.ssu.samara. ru/starting.html, 2006. (c) O’Keeffe, M. Reticular Chemistry Structure Resource (http://rcsr.anu.edu.au/). (13) (a) Li, D.; Wu, T.; Zhou, X.-P.; Zhou, R.; Huang, X.-C. Angew. Chem., Int. Ed. 2005, 44, 4175. (b) Wang, X.-L.; Qin, C.; Wang, E.-B.; Li, Y.-G.; Su, Z.-M.; Xu, L.; Carlucci, L. Angew. Chem., Int. Ed. 2005, 44, 5824. (c) Li, Z.; Li, M.; Zhan, S.-Z.; Huang, X.-C.; Ng, S. W.; Li, D. CrystEngComm 2008, 10, 978. (d) Perry, J. J., IV; Perman, J. A.; Zaworotko, M. J. Chem. Soc. Rev. 2009, 38, 1400. (e) Natarajan, S.; Mahata, P. Chem. Soc. Rev. 2009, 38, 2304. (f) Hu, S.; Liu, J.-L.; Meng, Z.-S.; Zheng, Y.-Z.; Lan, Y.; Powell, A. K.; Tong, M.-L Dalton Trans. 2011, 40, 27. (14) (a) Arnaud, N.; Vaquer, E.; Georges, J. Analyst 1998, 123, 261. (b) Vicentini, G.; Zinner, L. B.; Zukerman-Schpector, J.; Zinner, K. Coord. Chem. Rev. 2000, 196, 353. (c) Tedeschi, C.; Azema, J.; Gornitzka, H.; Tisnes, P.; Picard, C. Dalton Trans. 2003, 1738. (15) (a) Dias, A. B.; Viswanathan, S. Chem. Commun. 2004, 40, 1024. (b) Sun, Y.-Q.; Zhang, J.; Chen, Y.-M.; Yang, G.-Y. Angew. Chem., Int. Ed. 2005, 44, 5814. (16) Haas, Y.; Stein, G. J. Phys. Chem. 1971, 75, 3677. (17) (a) Ma, L.; Lin, W.-B. J. Am. Chem. Soc. 2008, 130, 13834. (b) Carboni, M.; Abney, C. W.; Liu, S. B.; Lin, W.-B. Chem. Sci. 2013, 4, 2396. (18) (a) Mcdonald, R. W.; Ikonomou, M. G.; Paton, D. W. Environ. Sci. Technol. 1998, 32, 331. (b) Alcock, R. E.; Jones, K. C.; McLachlan, M. S.; Johonston, A. E. Environ. Sci. Technol. 1999, 33, 206. (c) Jones, K. C.; de Voogt, P. Environ. Pollut. 1999, 100, 209. (d) Lallas, P. L. The Stockholm Convention on Persistent Organic Pollutants. Am. J. Int. Law 2001, 95, 692. (19) (a) Wright, W. D. Trans. Opt. Soc. 1928, 30, 141. (b) Guild, J. Philos. Trans. R. Soc. London, Ser. A 1932, 230, 149. (c) Phosphor Handbook; Shionoya, S., Yen, W. M., Eds.; CRC Press: Boca Raton, FL, 1999. (20) (a) Boaz, H.; Rollefson, G. K. J. Am. Chem. Soc. 1950, 72, 3435. (b) Keizer, J. J. Am. Chem. Soc. 1983, 105, 1494. (c) Gauthier, T. D.; Sham, E. C.; Guerln, W. F.; Rudolf Seltz, W.; Gran, C. L. Environ. Sci. Technol. 1986, 20, 1162. (21) (a) He, Q.; Miller, E. W.; Wong, A. P.; Chang, C. J. J. Am. Chem. Soc. 2006, 128, 9316. (b) Yoon, S.; Miller, E. W.; He, Q.; Do, P. H.; Chang, C. J. Angew. Chem., Int. Ed. 2007, 46, 6658. (c) Domaille, D. W.; Que, E. L.; Chang, C. J. Nat. Chem. Biol. 2008, 4, 168. (d) Lippert, A. R.; Gschneidtner, T.; Chang, C. J. Chem. Commun. 2010, 46, 7510. (e) Lippert, A. R.; Van de, B. G. C.; Chang, C. J. Acc. Chem. Res. 2011, 44, 793. (f) Karunadasa, H. I.; Montalvo, E.; Sun, Y.; Majda, M.; Long, J. R.; Chang, C. J. Science 2012, 335, 698. (g) Thoi, V. S.; Sun, Y.; Long, J. R.; Chang, C. J. Chem. Soc. Rev. 2013, 42, 2388. (h) Lin, V. S.; Lippert, A. R.; Chang, C. J. Proc. Natl. Acad. Sci. U. S. A. 2013, 110, 7131. (22) (a) US Department of Health and Human Services, Toxicological Profile for Chromium, Public Health Service Agency for Toxic Substances and Diseases Registry, Washington, DC, 1991. (b) Costa, M.; Klein, C. B. Crit. Rev. Toxicol. 2006, 36, 155. (23) (a) Yang, Q. Y.; Li, K.; Luo, J.; Pan, M.; Su, C. Y. Chem. Commun. 2011, 47, 4234. (b) Fu, J. H.; Li, H. J.; Mu, Y. J.; Hou, H. W.; Fan, Y. T. Chem. Commun. 2011, 47, 5271. (c) Ma, J.-P.; Yu, Y.; Dong, Y.-B. Chem. Commun. 2012, 48, 2946. (d) Shi, P.-F.; Zhao, B.; Xiong, G.; Hou, Y.-L.; Cheng, P. Chem. Commun. 2012, 48, 8231. (24) Wojcik, G.; Neagu, V.; Bunia, I. J. Hazard. Mater. 2011, 190, 544. (25) (a) Fei, H.; Rogow, D. L.; Oliver, S. R. J. J. Am. Chem. Soc. 2010, 132, 7202. (b) Fei, H.; Bresler, M. R.; Oliver, S. R. J. J. Am. Chem. Soc. 2011, 133, 11110.

(26) Weissman, S. I. J. Chem. Phys. 1942, 10, 214. (27) (a) Steemers, F. J.; Verboom, W.; Reinhoudt, D. N.; Vander Tol, E. B.; Verhoeven, J. W. J. Am. Chem. Soc. 1995, 117, 9408. (b) Cook, S. P.; Dieke, G. H. J. Chem. Phys. 1957, 27, 1213. (c) Dielre, G. H.; Leopold, L. J. Opt. Soc. Am. 1957, 47, 944. (28) (a) Dexter, D. L. J. Chem. Phys. 1953, 21, 836. (b) Sato, S.; Wada, M. Bull. Chem. Soc. Jpn. 1970, 43, 1955. (c) Li, C.; Quan, Z.; Yang, J.; Yang, P. P.; Lin, J. Inorg. Chem. 2007, 46, 6329. (d) Li, X.; Wang, C. Y.; Hu, H. M. Inorg. Chem. Commun. 2008, 11, 345. (29) Xiao, Y.; Wang, L.; Cui, Y.; Chen, B.; Zapatab, F.; Qian, G. J. Alloys Compd. 2009, 484, 601. (30) Reichardt, C.; Welton, T. Solvents and Solvent Effects in Organic Chemistry; 4th Updated and Enlarged ed.; Wiley-VCH: Weinheim, Germany, 2011; Chapter 2. (31) (a) Bünzli, J.-C. G.; Piguet, C. Chem. Soc. Rev. 2005, 34, 1048. (b) Rocha, J.; Carlos, L. D.; Paza, F. A. A.; Ananias, D. Chem. Soc. Rev. 2011, 40, 926.

426


Experimental Studies and Mechanism Analysis of High-Sensitivity

Recommend Documents