A Dual-emitting EY@Zr-MOF Composite as Self-calibrating

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A Dual-emitting EY@Zr-MOF Composite as Self-calibrating Luminescent Sensor for Selective Detection of Inorganic Ions and Nitroaromatics Yankun Li, Zihao Wei, Ye Zhang, Zhifen Guo, Dashu Chen, Peiyun Jia, Peng Chen, and Hongzhu Xing ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06500 • Publication Date (Web): 19 Feb 2019 Downloaded from http://pubs.acs.org on February 19, 2019

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ACS Sustainable Chemistry & Engineering

A Dual-emitting EY@Zr-MOF Composite as Selfcalibrating Luminescent Sensor for Selective Detection of Inorganic Ions and Nitroaromatics Yankun Li †, Zihao Wei †, Ye Zhang †, Zhifen Guo ‡, Dashu Chen*, †, Peiyun Jia †, Peng Chen§, and Hongzhu Xing*, ‡ †College

of Science, Department of Chemistry and Chemical Engineering, Northeast Forestry

University, 26 Hexing Road, Harbin, 150040, China. ‡College

of Chemistry, Provincial Key Laboratory of Advanced Energy Materials, Northeast

Normal University, 5268 Renmin Street, Changchun, 130024, China. §School

of Chemistry and Materials Science, Key Laboratory of Functional Inorganic Material

Chemistry (Heilongjiang University), Ministry of Education, Heilongjiang University, 74 Xuefu Road, Harbin, 150080, China.

1 Environment ACS Paragon Plus

ACS Sustainable Chemistry & Engineering 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

ABSTRACT

A dual-emitting dye@MOF composite has been synthesized by incorporating a fluorescent dye Eosin Y (EY) within a UiO-type zirconium based metal-organic framework (Zr-MOF) through a synthetic encapsulation method. The Zr-MOF prevents the aggregation of EY molecules and keeps EY molecules stably included after synthesis. As expected, an energy transfer from ZrMOF to EY molecules was occurred due to the good overlap between the emission of Zr-MOF and the absorption of EY. As a result, the obtained EY@Zr-MOF composite features a weak blue emission at 446 nm and a strong yellow emission at 553 nm. By using the relative height of the two emission peaks replace absolute peak height as detecting signals, EY@Zr-MOF composite acts as a self-calibrating luminescent sensor for selectively detecting Fe3+, Cr2O72- and 2nitrophenol. Furthermore, the observed fluorescence responses of the composite toward analyte are highly stable and reversible after recycling experiments. To the best of our knowledge, this is the first example of an dye@MOF-implicated self-calibrating sensor for Fe3+, Cr2O72- and 2nitrophenol detection.

KEYWORDS: Metal-organic framework, Self-calibrating sensor, Energy transfer, Eosin Y, Dual-emitting dye@MOF composite

INTRODUCTION Due to the needs of environmental monitoring and national defense security, the importance of sensing some kinds of cations, anions, and nitroaromatic compounds at a trace level has been increasingly emphasized.1-6 Luminescent sensors displayed numerous advantages, such as distinct signal outputs, low cost, quick response and high sensitivity.7-10 Luminescent molecular 2 Environment ACS Paragon Plus

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dyes have always been of concern as sensing agents where they are typically less expensive and even outperform organometallic or inorganic luminescent materials in some cases.11 However, molecular dyes easily pollute the liquid detection system and are difficult to separate from the system. In addition, the aggregation state of dyes will strongly diminish their luminescence via quenching effect.12,13 These characteristics of molecular dyes limited their further utilization in luminescence-related applications. Hence, it is necessary to develop molecular dyes that combine supporting materials to overcome above challenges. Metal-organic frameworks (MOFs) as an emerging type of hybrid materials exhibit advanced priority as supporting materials to combine with molecular dyes.11 Self-assembly from a variety of organic ligands and metal centers, MOFs exhibited unique properties including intrinsic crystallinity, porosity, structural diversity and tunability.14,15 By using post-insertion or synthetic encapsulation method,11 luminescent dyes can be loaded in the pores, channels or cavities of MOFs, which not only can effectively restrict aggregation-induced quenching of organic dyes, but also can protect dyes and keep their structural stability in harsh conditions.16-19 Meanwhile, the assembly of dye molecules into long-range ordered MOF materials diversifies their luminescent properties through different loading content or various interactions.20-22 More importantly, the combinations between MOFs and molecular dyes provide a fascinating platform to study the host-guest related energy transfer issues.23-25 So far, a majority of luminescent MOFs with single emission peak have been served as sensors to detect analyte.7,26,27 However, the absolute luminescence intensity of MOFs is not accurate signals to evaluate the detecting results because unstable instrumental parameters, optical occlusion and spatial concentration inhomogeneity can influence their final luminescence intensities.28-30 As an alternative method to overcome these problems, the combination of MOFs



with luminescent dyes usually makes materials afford dual-emitting or multi-emitting peaks where the emission intensity from MOF and dyes can be referenced with each other and construct a self-calibrating system to omit lots of environmental or methodological interferences.31-33 Recent years, some dye-loaded MOF-based self-calibrating sensors have been applied in sensing temperature,34 volatile organic molecules35,36 or explosives37 through luminescent quenching process. Nevertheless, there is no report for eosin Y (EY) loaded MOFbased composite with host-guest interactions as multi-responsive probe for detecting cations, anions, and nitroaromatic compounds. In this work, we fabricated a MOF-based luminescent sensor through embedding fluorescent EY molecules into a porous blue-emitting Zr-MOF. The resulting EY@Zr-MOF composite exhibits a dual-emitting luminescent property relying on host-guest energy transfer because of the good overlap between the emission of Zr-MOF and the absorbance of guest EY. The analytedependent quenching of fluorescence from encapsulated EY molecules, calibrated by the relatively weak emission of host Zr-MOF, has been utilized for reliable sensing of different cations, anions and nitroaromatic compounds. As a self-calibrating sensor, EY@Zr-MOF composite exhibits excellent sensitivity and selectivity for the detection of Fe3+ cations, Cr2O72anions and 2-nitrophenol showing significant Stern-Volmer quenching constants. RESULTS AND DISCUSSION EY molecule, a classic xanthene dye, is widely used as cell staining and sensing. Due to the presence of the bromine atoms attached to the xanthene skeleton, the photophysical properties of EY differ significantly from those of other dyes composed exclusively of light atoms, namely rhodamine, oxazine, fluorescein or acridine.38 In order to effectively combine the targeted EY dyes with MOFs to construct a dual-emitting composite, MOFs with UiO-type structures may be


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preferred because their relatively large cavity and narrow pore opening can restrict the loaded dyes in the voids, preventing the release of dyes from the framework.39 Thus Zr-MOFs become good candidates in view of their typical structures and good chemical stabilities.

Figure 1. (a) The diagram of fabricating EY@Zr-MOF composite via the in-situ synthetic encapsulation method. The pictures on the right are the optical photographs of Zr-MOF (solid state), EY@Zr-MOF (solid state) and EY@Zr-MOF immersed in DMF solution. (b) PXRD patterns of synthesized EY@Zr-MOF, synthesized Zr-MOF and the simulated Zr-MOF. (c) N2 sorption isotherms of EY@Zr-MOF composite at 77 K. The Zr-MOF constructed from Zr6 oxo cluster and 4,4’-stilbenedicarboxylic acid (H2L) was employed here as it shows UiO-type structure with large cavity size and small pore window,40 suitable for the loading of EY molecule (ca. 0.7×1.3×1.4 nm3). The in-situ synthetic



encapsulation method was adopted to prepare target EY@Zr-MOF composite. As shown in Figure 1a, the color of synthesized EY@Zr-MOF composite is pink instead of milky white shown by pristine Zr-MOF. Then the EY@Zr-MOF composite was soaked in clean DMF, it showed no release of EY molecules (Figure 1a, insert). Control experiments showed that the EY molecules can neither diffuse into the framework nor be adsorbed on the surface of Zr-MOF (Figure S1). These results suggest the confinement effect of this UiO-type Zr-MOF for the loading of EY molecules. By referring standard absorbance curve of EY solution and the absorbance of solution which is prepared by thermally decomposing a certain amount of EY@Zr-MOF composite under alkaline conditions, the loaded proportion of EY in synthesized composite is 1.6 % (Figure S2-S3). Nevertheless, it is difficult to get the detailed location of EY in the framework of Zr-MOF from single crystal data due to its very low occupancy. The powder X-ray diffraction pattern of EY@Zr-MOF matches well with that shown by Zr-MOF, indicating that the framework structure of the composite is consistency with the Zr-MOF (Figure 1b). The N2 sorption isotherms have revealed that EY@Zr-MOF composite is still porous and the Brunauer–Emmett–Teller (BET) surface area is 444 m2 g-1 (Figure 1c), which is smaller than the pristine Zr-MOF (2667 m2 g-1)40 due to the encapsulation of EY molecules in the framework. Pore size distribution suggests a repartition of pore owing to the loading of EY molecules where a smaller pore centered at ca. 6.3 Å has been observed (Figure S4).41 Luminescence Properties of EY@Zr-MOF Composite. The solid-state emission spectra of EY@Zr-MOF were first investigated at room temperature. As expected, the EY@Zr-MOF presents a dual-emitting luminescent property, which shows a weak emission centered at 446 nm and a strong emission centered at 553 nm when excited at 365 nm (Figure 2a). Control experiment illustrates the emission band of Zr-MOF centered at 446 nm, indicating the emission


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at 446 nm for EY@Zr-MOF composite is based on pristine Zr-MOF. As the experiment shows, EY in the solid state is nearly non-fluorescent, which can be ascribe to the aggregation-caused quenching effect (Figure 2a).13 Moreover, EY shows concentration-dependent fluorescence in solution (Figure S5). The dilute solution of EY in ethanol (0.25 g L-1) displays yellow emission centered at 553 nm (Figure 2a), which is similar to the main emission of EY@Zr-MOF composite. Hence the emission peaks of EY@Zr-MOF at 553 nm originate from the loaded EY molecules and are more close to the molecular states of EY.

Figure 2. (a) Fluorescent spectra of Zr-MOF (solid state), EY@Zr-MOF (solid state), EY (solid state) and EY (ethanol solution, 0.25 g L-1). Inset: optical photographs of Zr-MOF and EY@ZrMOF dispersed in ethanol solution under a UV lamp excited at 365 nm. (b) Normalized fluorescent spectra of Zr-MOF in the solid state (blue, λex = 365 nm) and the UV-vis absorption spectra of EY ethanol solution (green, 0.25 g L-1). (c) Semilog plots of florescence decay versus time of EY@Zr-MOF (solid state) and EY (ethanol solution, 0.25 g L-1). It is remarkable that the fluorescence intensity of EY@Zr-MOF at 553 nm is 10 times higher than that at 446 nm, indicating the fluorescence of the resulting composite dominated by the emission of loaded EY molecules. The emission from EY molecule in EY@Zr-MOF should result from efficient energy transfer from luminescent Zr-MOF. This is confirmed by the good spectral overlap between the fluorescence emission of Zr-MOF and the absorption of EY molecules (Figure 2b). The energy transfer process is also confirmed by the declined emission at



446 nm in EY@Zr-MOF as compared with that shown by Zr-MOF. To further verify this situation, the fluorescence lifetime of EY@Zr-MOF and EY molecule was monitored at 553 nm. As shown in Figure 2c, the lifetime of EY in ethanol solution is 1.42 ns, while the lifetime of EY loaded in Zr-MOF is lengthened to 2.73 ns. The longer lifetime shown by EY@Zr-MOF indicates the existence of energy transfer from Zr-MOF to EY molecules. Sensing Measurements. It is found that the fluorescence peaks towards EY@Zr-MOF nearly unchanged when it was immersed in different solvents, including water, ethanol, methanol and acetonitrile (Figure S6). In addition, the locations of two emission peaks are relatively far apart from each other (107 nm) and the two emission peaks are without overlap (Figure 2a), which is in favor of fluorescence sensing test and avoiding unnecessary interferences.


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Figure 3. (a) Fluorescent emission spectra and (b) Relative luminescence intensities of EY@ZrMOF dispersed into aqueous solutions containing different metal ions (1 mM) when excited at 365 nm. (c) The concentration-dependent fluorescent emission spectra upon the different contents of Fe3+ in aqueous solutions. Inset: optical photographs of excited EY@Zr-MOF suspensions before and after adding the Fe3+ aqueous solution (1 mM). (d) Stern-Volmer plot of (I0R /IR) versus Fe3+ concentration in aqueous solution for EY@Zr-MOF. Hence as the potential fluorescent probe, EY@Zr-MOF composite with dual-emitting luminescent characteristics was tested with ions and nitroaromatic compounds as analyte. At first, we investigated the sensing ability of EY@Zr-MOF composite towards various metal cations in water. Before the luminescent sensing measurements, the stability of the EY@Zr-MOF composite in water was confirmed by PXRD (Figure S7). After immersed in water for 24h, the EY@Zr-MOF composite still maintains its structure. Subsequently, the suspensions of the EY@Zr-MOF were added to solutions (1 mM, 3 mL) containing different metal ions (Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Fe2+, Ni2+, Cu2+, Hg2+, Zn2+, Cr3+, Pb2+, Al3+, Fe3+). The analyte liquor containing only EY@Zr-MOF was served as the fluorescent standard solution to evaluate the response of different cations. As shown in Figure 3a, the introduction of metal ions caused a different degree of fluorescence quenching compared with that of standard solution. Notably, the intensity of emission peak at 446 nm for EY@Zr-MOF composite changed little, while the intensity of emission peak at 553 nm decreased significantly. In view of this situation, the EY@Zr-MOF composite can be used as a self-calibrating sensor for testing metal ions, where the emission peak at 446 nm serves as a reference peak to calibrate the fluorescence quenching detection happened at 553 nm by measuring the relative peak-height of both emissions. As shown in Figure S8, the relative peak-height is defined as the difference value between



fluorescence intensity at 553 nm and 446 nm. The relative peak-height of EY@Zr-MOF in solution without analyte is represented as I0R, while this value is represented as IR in the presence of analyte. The relative luminescence intensity (RLI) for sensing different analyte was defined as (IR / I0R). As shown in Figure 3a and 3b, Fe3+ ions afforded the most significant quenching effect with a lowest RLI value (0.14). Metal ions of Cu2+, Hg2+, Fe2+ show moderate RLI values in the range of 0.4-0.53. While, other 11 metal ions in Figure 3b display a high RLI values ranging from 0.7-0.98. This result reveals the fluorescence of EY@Zr-MOF composite is very sensitive to Fe3+ ions. Then the luminescence spectra towards different concentrations of Fe3+ ions were tested through the titration method. The fluorescence of EY@Zr-MOF decreases sharply with an increase of Fe3+ from 0.01 to 1 mM (Figure 3c). The quenching effect of Fe3+ on EY@Zr-MOF in dark condition is also easily observed by the naked eye (Figure 3c, inset). The quenching constants Ksv of the analyte can be calculated from the Stern–Volmer (SV) equation (I0R / IR) = 1 + Ksv × [M],42 where [M] is the molar concentration of the analyte, I0R and IR are the same as previous definitions. As depicted in Figure 3d, the presence of Fe3+ results in linear SV plots in a broad concentration range, indicating it is suitable for the calculation of Ksv from the SV equation. The value of the quenching constants Ksv is estimated to be 1.02 × 104 M-1 for Fe3+.


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Figure 4. (a) Fluorescent emission spectra and (b) Relative luminescence intensities of EY@ZrMOF dispersed into aqueous solutions containing different anions (0.1 mM) when excited at 365 nm. (c) The concentration-dependent fluorescent emission spectra upon the different contents of Cr2O72- in aqueous solutions. Inset: optical photographs of excited EY@Zr-MOF suspensions before and after adding the Cr2O72- aqueous solution (0.1 mM). (d) Stern-Volmer plot of (I0R /IR) versus Cr2O72- concentration in aqueous solution for EY@Zr-MOF. After the detection of various cations, the anions sensing of EY@Zr-MOF composite was conducted by the same method. The luminescent intensity changes of EY@Zr-MOF in different anions (0.1 mM) were shown in Figure 4a. Among the 13 tested anions, Cr2O72- exhibited the



largest quenching effect on the emission of EY@Zr-MOF. The RLI value for sensing 0.1 mM Cr2O72- is as small as 0.06 while the RLI values are larger than 0.74 for other 12 anions (Figure 4b). The high selectivity of EY@Zr-MOF toward Cr2O72- was further probed by concentrationdependent luminescence measurement. The EY@Zr-MOF composite produced a gradual decrease in the luminescence intensity with an increase in the content of Cr2O72- from 5×10-4 to 0.1 mM (Figure 4c). The SV plots for EY@Zr-MOF in the presence of Cr2O72- also present a linearity in the tested concentration range (Figure 4d). According to the SV equation, the calculated quenching effect constants Ksv is 1.44 × 105 M-1 for Cr2O72-. This result showed that EY@Zr-MOF could also serve as a good anionic sensor for highly selective recognizing Cr2O72-.


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Figure 5. (a) Fluorescent emission spectra and (b) Relative luminescence intensities of EY@ZrMOF dispersed into ethanol solutions containing different nitroaromatic compounds (1 mM) when excited at 365 nm. (c) The concentration-dependent fluorescent emission spectra upon the different contents of 2-NP in ethanol solutions. Inset: optical photographs of excited EY@ZrMOF suspensions before and after adding the 2-NP ethanol solution (1 mM). (d) Stern-Volmer plot of (I0R /IR) versus 2-NP concentration in ethanol solution for EY@Zr-MOF. The remarkable sensing performances of synthesized EY@Zr-MOF composite toward different cations and anions arouse our enormous interest in detecting nitroaromatics in solution. To check its characteristics and affinity towards different nitroaromatic compounds, a batch of suspensions of EY@Zr-MOF with various nitroaromatics was prepared. As shown in Figure 5a, the analyte liquor of EY@Zr-MOF exhibited markedly different luminescence intensities in the presence of these nitroaromatics. Among these 11 nitroaromatics, 2-nitrophenol (2-NP) afforded the most significant quenching effect and the lowest RLI value (0.03 for 2-NP) (Figure 5b). Although the fluorescence of EY@Zr-MOF composite is also quenched by its isomers 3nitrophenol (3-NP) and 4-nitrophenol (4-NP), the RLI value for 3-NP (0.28) and 4-NP (0.20) is 7-9 times larger than that of 2-NP, indicating high selectivity of EY@Zr-MOF for 2-NP (Figure 5b). The fluorescence intensity of EY@Zr-MOF composite gradually decreases with an increase of 2-NP from 0.01 to 1 mM (Figure 5c). The Stern–Volmer plots for 2-NP also exhibit quasilinear correlations in the tested concentration area where the calculated Ksv is 1.33 × 104 M-1 (Figure 5d). These results demonstrated that the synthesized EY@Zr-MOF composite is a multi-response fluorescence sensor to detect analyte, such as cations, anions or nitroaromatics. Although EY molecules also can exhibit the fluorescence response for cations, anions and nitroaromatics



(Figure S9-S11), the recycling of EY molecules is relative cumbersome. Importantly, the sensing based on measurement of relative peak-height makes the sensing process more reliable as compared with single-emission quenching detection, due to the character of self-calibrating. We further interpret the possible sensing mechanism between EY@Zr-MOF composite and analyte. We measured the light absorption of all the analytes. As shown in Figure S12-S14, Fe3+, Cr2O72and 2-NP showed obvious light absorption in the range of 400-500 nm. As mentioned above, the first fluorescence band of EY@Zr-MOF belonging to Zr-MOF emission locates also at this region. The excellent spectrum overlap between the luminescence of Zr-MOF and the absorption of these analytes is indeed helpful to the fluorescence resonant energy transfer (FRET) from ZrMOF to analyte.43 In this case, the emission of EY would be significantly quenched and hence showing desirable sensing performance in high sensitivity. In addition, EY@Zr-MOF composite can be at least regenerated up to 5 cycles by centrifuging the suspension after detecting Fe3+, Cr2O72- ions or 2-NP (Figure S15-S17). The PXRD patterns of the recyclable EY@Zr-MOF composite demonstrate it still keep structural integrity (Figure S18). The performance of EY@Zr-MOF composite for sensing Fe3+, Cr2O72- ions and 2-NP is comparable with some recently reported dye-loaded MOF composites and single-emission MOF sensors.32,43-47 CONCLUSIONS In conclusion, an EY@Zr-MOF composite has been successfully synthesized by using simple insitu synthetic encapsulation method, and the synthesized composite is of high stability and porosity. The encapsulation of EY molecules enables the resulting material feature a weak blue emission at 446 nm and a strong yellow emission at 553 nm. The dual-emission of the material is based on effective energy transfer from Zr-MOF to EY due to the good spectral overlap between the emission of Zr-MOF and the absorption of loaded EY molecules. The large distinction in


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height and location of two emission peaks makes EY@Zr-MOF composite act as a selfcalibrating luminescent sensor for the detection of various analytes including cations, anions and nitroaromatic compounds. The utilization of relative peak intensity as detection signal make the sensing process more stable and reliable. This study demonstrated that the combination of ZrMOFs with EY not only make composite inherit, improve luminescent properties of dye molecules and show excellent performance in multi-responsive sensing, but also the heterogeneity and stability of composite make it easier to use and recycle in view of the concept of green chemistry. EXPERIMENTAL SECTION Materials and Methods. Eosin Y (AR) was purchased from Aladdin. Zirconium(IV) chloride (ZrCl4, 99.5%) and 4,4’-stilbenedicarboxylic acid (H2L) were purchased from Alfa. Other reagents and chemicals were of analytical grade and used without further purification. The powder X-ray diffraction (PXRD) patterns of the products were recorded on a Rigaku D-MAX 2550 diffractometer (Cu Kα radiation, λ = 0.15417 nm), employing a scanning rate of 5° min-1 and the 2θ range from 3° to 40°. Thermogravimetric analysis (TGA) was carried out using a PerkinElmer TG-7 system at a heating rate of 10 °C min−1 from room temperature to 800 °C under atmosphere. N2 sorption measurements were measured at the liquid nitrogen temperature, using a Micrometritics ASAP 2020 system. The samples were immersed in methanol for guestexchange and further degassed at 100 oC for 10 h before the measurements. The UV/Vis absorption spectra were obtained using a HITACHIU-4100 spectrophotometer in the wavelength range of 200-800 nm. Fluorescence spectra were recorded on the LS-55 spectrophotometer at room

temperature.

Fluorescence

lifetime

of

samples

spectrophotometer at room temperature.


was

tested

on

the

FLS980


Synthesis of EY@Zr-MOF Composite. A mixture of ZrCl4 (104 mg, 0.448 mmol), H2L (120 mg, 0.448 mmol), eosin Y (372 mg for Na2-EY or 349 mg for neutral EY, 0.538 mmol), acetic acid (3.3 mL) and DMF (18 mL) was equally placed in six Teflon autoclave (20 mL) and stirred for 30 min at room temperature. The autoclave was heated at 100 °C for 72 h. After the autoclave was gradually cooled to ambient temperature, pink crystals were obtained and washed with DMF and ethanol several times for further use. Yield: ca. 60% based on H2L. Synthesis of Zr-MOF. A mixture of ZrCl4 (104 mg, 0.448 mmol), H2L (120 mg, 0.448 mmol), acetic acid (2.4 mL) and DMF (18 mL) was equally placed in six Teflon autoclave (20 mL) and stirred for 30 min at room temperature. The autoclave was heated at 100 °C for 72 h. After the autoclave was gradually cooled to ambient temperature, white crystals of octahedral shape were obtained and washed with DMF and ethanol several times for further use. Yield: ca. 70% based on H2L. Sensing of metal cations. The finely ground EY@Zr-MOF composite (10 mg) was immersed in aqueous solution (10 mL), treated by ultrasonication for 5 min, and subsequently aged to make the suspension stable enough. The above suspension (600 μL) was added to the 3 ml aqueous solutions containing different metal ions for luminescence studies. After mixing thoroughly at room temperature for 60 s, the fluorescence spectra were recorded with an emission wavelength in the range from 380 to 700 nm (excitation at λ = 365 nm). Aqueous solutions of Na+, K+, Ag+, Ca2+, Cr3+, Ba2+, Zn2+, Mg2+, Ni2+, Al3+, Pb2+, Cu2+, and Fe3+ were prepared from nitrate salts; solution of Hg2+ was prepared from chlorate salts, Fe2+ solution was prepared from ferrous sulfate and used immediately. The concentration of metal salts was 1 mM. Sensing of anions. The procedure of sensing anions was same to the metal cations. Aqueous solutions of HOOC-, IO3-, F-, Cl-, Br-, I-, NO3-, NO2-, SO32-, SO42-, HSO3-, Cr2O72- were prepared


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from sodium salts, solution of SCN- was prepared from potassium salt and used immediately. The concentration of anions was 0.1 mM. Sensing of nitroaromatic compounds. The procedure of sensing nitroaromatic compounds was same to the metal cations except that aqueous solution was changed to ethanol solution. Nitroaromatic compounds of 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), 1,2-dinitrobenzene (1,2-DNB), 1,3- dinitrobenzene (1,3-DNB), 1,4- dinitrobenzene (1,4-DNB), 2-nitrotoluene (2-NT), 3-nitrotoluene (3-NT), 4-nitrotoluene (4-NT), nitrobenzene (NB), 2-nitrom-xylene (NX) were dissolve in ethanol solution and the concentration of nitroaromatic compounds was 1 mM. Typical procedure for fluorescence titration studies. The powder sample of EY@Zr-MOF composite was dispersed in corresponding solvent and subsequently transferred 3 mL suspensions to a quartz cell. Quenching tests were carried out by gradually adding the analyte (Fe3+, Cr2O72- aqueous solution or 2-NP ethanol solution).

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: Standard absorbance curve, TG curve, pore size distribution, emission spectra, PXRD patterns, the definition of relative peak-height, UV/Vis absorption spectra, and recycling test. (PDF) AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] (D. Chen) * E-mail: [email protected] (H. Xing) 17 Environment ACS Paragon Plus


ORCID Dashu Chen: 0000-0002-9685-4566 Hongzhu Xing: 0000-0001-7179-0394 Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work is supported by the Natural Science Foundation of Heilongjiang Province (QC2018007) and Open Project Funds for Key Laboratory of Functional Inorganic Material Chemistry (Heilongjiang University), Ministry of Education. REFERENCES (1) Sun, X. C.; Wang, Y.; Lei, Y. Fluorescence based explosive detection: from mechanisms to sensory materials. Chem. Soc. Rev. 2015, 44, 8019-8061. (2) Carter, K. P.; Young, A. M.; Palmer, A. E. Fluorescent Sensors for Measuring Metal Ions in Living Systems. Chem. Rev. 2014, 114, 4564-4601. (3) Chen, G. Q.; Guo, Z.; Zeng, G. M.; Tang, L. Fluorescent and colorimetric sensors for environmental mercury detection. Analyst 2015, 140, 5400-5443. (4) Kim, H. N.; Ren, W. X.; Kim, J. S.; Yoon, J. Fluorescent and colorimetric sensors for detection of lead, cadmium, and mercury ions. Chem. Soc. Rev. 2012, 41, 3210-3244. (5) Salinas, Y.; Martinez-Manez, R.; Marcos, M. D.; Sancenon, F.; Costero, A. M.; Parra, M.; Gil, S. Optical chemosensors and reagents to detect explosives. Chem. Soc. Rev. 2012, 41, 1261-1296. 18 Environment ACS Paragon Plus

Page 18 of 26

Page 19 of 26 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


(6) Yan, B. Lanthanide-Functionalized Metal-Organic Framework Hybrid Systems To Create Multiple Luminescent Centers for Chemical Sensing. Acc. Chem. Res. 2017, 50, 27892798. (7) Lustig, W. P.; Mukherjee, S.; Rudd, N. D.; Desai, A. V.; Li, J.; Ghosh, S. K. Metalorganic frameworks: functional luminescent and photonic materials for sensing applications. Chem. Soc. Rev. 2017, 46, 3242-3285. (8) Xing, S. H.; Bing, Q. M.; Qi, H.; Liu, J. Y.; Bai, T. Y.; Li, G. H.; Shi, Z.; Feng, S. H.; Xu, R. R. Rational Design and Functionalization of a Zinc Metal-Organic Framework for Highly Selective Detection of 2,4,6-Trinitrophenol. ACS Appl. Mater. Interfaces 2017, 9, 23828-23835. (9) Yi, F. Y.; Chen, D. X.; Wu, M. K.; Han, L.; Jiang, H. L. Chemical Sensors Based on Metal-Organic Frameworks. ChemPlusChem 2016, 81, 675-690. (10)Senthilkumar, S.; Goswami, R.; Obasi, N. L.; Neogi, S. Construction of Pillar-Layer Metal-Organic Frameworks for CO2 Adsorption under Humid Climate: High Selectivity and Sensitive Detection of Picric Acid in Water. ACS Sustain. Chem. Eng. 2017, 5, 1130711315. (11)Ryu, U.; Lee, H. S.; Park, K. S.; Choi, K. M. The rules and roles of metal–organic framework in combination with molecular dyes. Polyhedron 2018, 154, 275-294. (12)Kim, T. W.; Park, J. H.; Hong, J. I. Self-quenching mechanism: the influence of quencher and spacer on quencher-fluorescein probes. Bull. Korean Chem. Soc. 2007, 28, 1221-1223.



(13)Munkholm, C.; Parkinson, D. R.; Walt, D. R. Intramolecular Fluorescence Self-Quenching of Fluoresceinamine. J. Am. Chem. Soc. 1990, 112, 2608-2612. (14)Furukawa, H.; Muller, U.; Yaghi, O. M. "Heterogeneity within order" in metal-organic frameworks. Angew. Chem. Int. Ed. 2015, 54, 3417-3430. (15)Furukawa, H.; Cordova, K. E.; O'Keeffe, M.; Yaghi, O. M. The chemistry and applications of metal-organic frameworks. Science 2013, 341, 1230444. (16)Wei, Y.; Dong, H.; Wei, C.; Zhang, W.; Yan, Y.; Zhao, Y. S. Wavelength-Tunable Microlasers Based on the Encapsulation of Organic Dye in Metal-Organic Frameworks. Adv. Mater. 2016, 28, 7424-7429. (17)Zhang, Y.; Li, B.; Ma, H.; Zhang, L.; Zhang, W. An RGH–MOF as a naked eye colorimetric fluorescent sensor for picric acid recognition. J. Mater. Chem. C 2017, 5, 4661-4669. (18)Liu, J.; Zhuang, Y.; Wang, L.; Zhou, T.; Hirosaki, N.; Xie, R. J. Achieving Multicolor Long-Lived Luminescence in Dye-Encapsulated Metal-Organic Frameworks and Its Application to Anticounterfeiting Stamps. ACS Appl. Mater. Interfaces 2018, 10, 18021809. (19)Wang, C.; Tian, L.; Zhu, W.; Wang, S.; Wang, P.; Liang, Y.; Zhang, W.; Zhao, H.; Li, G. Dye@bio-MOF-1 Composite as a Dual-Emitting Platform for Enhanced Detection of a Wide Range of Explosive Molecules. ACS Appl. Mater. Interfaces 2017, 9, 20076-20085.


Page 20 of 26

Page 21 of 26 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


(20)Wan, Y. T.; Cui, Y. J.; Yang, Y.; Qian, G. D. Dye confined in metal-organic framework for two-photon fluorescent temperature sensing. Microporous Mesoporous Mater. 2018, 268, 202-206. (21)Chen, D. M.; Zhang, N. N.; Liu, C. S.; Du, M. Dual-Emitting Dye@MOF Composite as a Self-Calibrating Sensor for 2,4,6-Trinitrophenol. ACS Appl. Mater. Interfaces 2017, 9, 24671-24677. (22)Ryu, U.; Yoo, J.; Kwon, W.; Choi, K. M. Tailoring Nanocrystalline Metal-Organic Frameworks as Fluorescent Dye Carriers for Bioimaging. Inorg. Chem. 2017, 56, 1285912865. (23)Lee, C. Y.; Farha, O. K.; Hong, B. J.; Sarjeant, A. A.; Nguyen, S. T.; Hupp, J. T. Lightharvesting metal-organic frameworks (MOFs): efficient strut-to-strut energy transfer in bodipy and porphyrin-based MOFs. J. Am. Chem. Soc. 2011, 133, 15858-15861. (24)Son, H. J.; Jin, S.; Patwardhan, S.; Wezenberg, S. J.; Jeong, N. C.; So, M.; Wilmer, C. E.; Sarjeant, A. A.; Schatz, G. C.; Snurr, R. Q.; Farha, O. K.; Wiederrecht, G. P.; Hupp, J. T. Light-harvesting and ultrafast energy migration in porphyrin-based metal-organic frameworks. J. Am. Chem. Soc. 2013, 135, 862-869. (25)u, D.; Ma, L.; Papanikolas, J. M.; Meyer, T. J.; Lin, W. Light harvesting in microscale metal-organic frameworks by energy migration and interfacial electron transfer quenching. J. Am. Chem. Soc. 2011, 133, 12940-12943. (26)Wang, B.; Lv, X. L.; Feng, D. W.; Xie, L. H.; Zhang, J.; Li, M.; Xie, Y. B.; Li, J. R.; Zhou, H. C. Highly Stable Zr(IV)-Based Metal-Organic Frameworks for the Detection and



Removal of Antibiotics and Organic Explosives in Water. J. Am. Chem. Soc. 2016, 138, 6204-6216. (27)Hu, Z. C.; Deibert, B. J.; Li, J. Luminescent metal-organic frameworks for chemical sensing and explosive detection. Chem. Soc. Rev. 2014, 43, 5815-5840. (28)Smaldone, R. A.; Forgan, R. S.; Furukawa, H.; Gassensmith, J. J.; Slawin, A. M. Z.; Yaghi, O. M.; Stoddart, J. F. Metal-Organic Frameworks from Edible Natural Products. Angew. Chem. Int. Ed. 2010, 49, 8630-8634. (29)Zhai, L.; Yang, Z. X.; Zhang, W. W.; Zuo, J. L.; Ren, X. M. Dual-emission and thermochromic luminescence alkaline earth metal coordination polymers and their blend films with polyvinylidene fluoride for detecting nitrobenzene vapor. J. Mater. Chem. C 2018, 6, 7030-7041. (30)Ye, J. W.; Lin, J. M.; Mo, Z. W.; He, C. T.; Zhou, H. L.; Zhang, J. P.; Chen, X. M. MixedLanthanide Porous Coordination Polymers Showing Range Tunable-Ratiometric Luminescence for O2 Sensing. Inorg. Chem. 2017, 56, 4238-4243. (31)Cui, Y.; Song, R.; Yu, J.; Liu, M.; Wang, Z.; Wu, C.; Yang, Y.; Wang, Z.; Chen, B.; Qian, G. Dual-emitting MOF supersetdye composite for ratiometric temperature sensing. Adv. Mater. 2015, 27, 1420-1425. (32)Fu, H.-R.; Zhao, Y.; Xie, T.; Han, M.-L.; Ma, L.-F.; Zang, S.-Q. Stable dye-encapsulated indium–organic framework as dual-emitting sensor for the detection of Hg2+/Cr2O72− and a wide range of nitro-compounds. J. Mater. Chem. C 2018, 6, 6440-6448.


Page 22 of 26

Page 23 of 26 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


(33)Wu,

P.;

Hou,

X.

D.;

Xu,

J.

J.;

Chen,

H.

electrochemiluminescence,

and

photoelectrochemical

Y.

Ratiometric

chemo/biosensing

fluorescence, based

on

semiconductor quantum dots. Nanoscale 2016, 8, 8427-8442. (34)Zhou, Y.; Zhang, D.; Zeng, J.; Gan, N.; Cuan, J. A luminescent Lanthanide-free MOF nanohybrid for highly sensitive ratiometric temperature sensing in physiological range. Talanta 2018, 181, 410-415. (35)Dong, M. J.; Zhao, M.; Ou, S.; Zou, C.; Wu, C. D. A luminescent dye@MOF platform: emission fingerprint relationships of volatile organic molecules. Angew. Chem. Int. Ed. 2014, 53, 1575-1579. (36)Xie, W.; He, W. W.; Li, S. L.; Shao, K. Z.; Su, Z. M.; Lan, Y. Q. An Anionic Interpenetrated Zeolite-Like Metal-Organic Framework Composite As a Tunable DualEmission Luminescent Switch for Detecting Volatile Organic Molecules. Chem. -Eur. J. 2016, 22, 17298-17304. (37)Bagheri, M.; Masoomi, M. Y.; Morsali, A.; Schoedel, A. Two Dimensional Host-Guest Metal-Organic Framework Sensor with High Selectivity and Sensitivity to Picric Acid. ACS Appl. Mater. Interfaces 2016, 8, 21472-21479. (38)Rodriguez, H. B.; San Roman, E.; Duarte, P.; Machado, I. F.; Ferreira, L. F. Eosin Y triplet state as a probe of spatial heterogeneity in microcrystalline cellulose. Photochem Photobiol 2012, 88, 831-839.



(39)Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P. A new zirconium inorganic building brick forming metal organic frameworks with exceptional stability. J. Am. Chem. Soc. 2008, 130, 13850-13851. (40)Naeem, A.; Ting, V. P.; Hintermair, U.; Tian, M.; Telford, R.; Halim, S.; Nowell, H.; Holynska, M.; Teat, S. J.; Scowen, I. J.; Nayak, S. Mixed-linker approach in designing porous zirconium-based metal-organic frameworks with high hydrogen storage capacity. Chem. Commun. 2016, 52, 7826-7829. (41)Zhang, J.; Yao, S.; Liu, S.; Liu, B.; Sun, X. D.; Zhang, B.; Li, G. H.; Li, Y.; Huo, Q. S.; Liu, Y. L. Enhancement of Gas Sorption and Separation Performance via Ligand Functionalization within Highly Stable Zirconium-Based Metal-Organic Frameworks. Cryst. Growth Des. 2017, 17, 2131-2139. (42)Cho, W.; Lee, H. J.; Choi, G.; Choi, S.; Oh, M. Dual changes in conformation and optical properties of fluorophores within a metal-organic framework during framework construction and associated sensing event. J. Am. Chem. Soc. 2014, 136, 12201-12204. (43)He, T.; Zhang, Y. Z.; Kong, X. J.; Yu, J.; Lv, X. L.; Wu, Y.; Guo, Z. J.; Li, J. R. Zr(IV)Based Metal-Organic Framework with T-Shaped Ligand: Unique Structure, High Stability, Selective Detection, and Rapid Adsorption of Cr2O72- in Water. ACS Appl. Mater. Interfaces 2018, 10, 16650-16659. (44)Chen, M.; Xu, W. M.; Tian, J. Y.; Cui, H.; Zhang, J. X.; Liu, C. S.; Du, M. A terbium(III) lanthanide-organic framework as a platform for a recyclable multi-responsive luminescent sensor. J. Mater. Chem. C 2017, 5, 2015-2021.


Page 24 of 26

Page 25 of 26 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


(45)Hu, J.; Cheng, T.; Dong, S.; Zhou, C.; Huang, X.; Zhang, L. Multifunctional luminescent Cd (II)-based metal-organic framework material for highly selective and sensitive sensing 2,4,6-trinitrophenol (TNP) and Fe3+ cation. Microporous Mesoporous Mater. 2018, 272, 177-183. (46)Huo, J. Z.; Su, X. M.; Wu, X. X.; Liu, Y. Y.; Ding, B. Hydrothermal synthesis and characterization of a series of luminescent Ag(i) coordination polymers with two new multidentate

bis-(1,2,3-triazole)

ligands:

structural

diversity,

polymorphism

and

photoluminescent sensing. CrystEngComm 2016, 18, 6640-6652. (47)Yi, F. Y.; Wang, S. C.; Gu, M. L.; Zheng, J. Q.; Han, L. Highly selective luminescent sensor for CCl4 vapor and pollutional anions/cations based on a multi-responsive MOF. J. Mater. Chem. C 2018, 6, 2010-2018.



For Table of Contents Use Only Synopsis A dual-emitting EY@Zr-MOF composite acts as a self-calibrating luminescent sensor for detecting Fe3+, Cr2O72- and 2-nitrophenol.


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A Dual-emitting EY@Zr-MOF Composite as Self-calibrating

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