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Tb3+ hybrids based with metal-organic frameworks and zeolites A
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117107
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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Multi-component luminescence responsive Eu3+/Tb3+ hybrids based with metal-organic frameworks and zeolites A Jing Ma b, Bing Yan a,b,⁎ a b
School of Materials Science and Engineering, Liaocheng University, Liaocheng 252059, China School of Chemical Science and Engineering, Tongji University, Shanghai 200092, China
a r t i c l e
i n f o
Article history: Received 29 November 2018 Received in revised form 4 May 2019 Accepted 9 May 2019 Available online 10 May 2019 Keywords: Multi-component hybrid material Lanthanide ion Zeolite A Metal-organic frameworks Luminescence
a b s t r a c t Both Zeolite A (ZA) and two kinds of 2,2′-bipyridine-5,5′-dicarboxylic acid (H2bpydc) linking meta-organic frameworks (MOFs) (MOF-253 (Al(OH)(bpydc)) and UiO-67 ([Zr6O4(OH)4(bpydc)6])) have been used to construct novel photofunctional multi-component lanthanide hybrid materials through covalent-coordination cooperative assembly. Microporous ZA is firstly functionalized by covalently grafting of the surface hydroxyl groups using special silane crosslinking reagent 3-methacryloxypropyltrimethoxysilane (MPTMS). Then the multicomponent assembly are realized by coordination interaction between lanthanide ions (Eu3+/Tb3+), ZA through the carbonyl group of MPTMS unit and MOF-253 (or UiO-67) through the double nitrogen of bpydc linker. Subsequently, the obtained multicomponent hybrid materials (ZA-MPTMS-Eu/Tb-MOF-253(UiO-67)) are characterized by means of XRD, FT-IR, SEM and especially the photoluminescence properties are studied in details. These hybrids with both ZA and MOFs host show the main characteristic crystal framework morphology of ZA together with the composition of MOFs. They display the feature luminescence of Eu3+/Tb3+ ions for the energy transfer from bpydc linker of MOFs. Furthermore, ZA-MPTMS-Eu-UiO-67 hybrid material is selected to check the luminescence response to volatile substances, whose luminescence quenching is found for ammonia vapor. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Lanthanide coordination compounds have attracted extensive interest for their special luminescent feature such as intense and wide emission bands, broad range of decay lifetime and high color purity [1,2]. Nevertheless, organolanthanide complexes are difficult to be used directly in practical applications due to the limit of their poor thermal and photo stability. In order to solve this problem, lanthanide inorganic–organic hybrid materials are developed to integrate the respective characteristics of inorganic and organic components and produce the eminent properties [3]. All kinds of building units introduced into these hybrids make them to have the expected potential applications in the practical fields such as in devices, amplifiers and chemical sensors etc. [4–7] To presence, much research works have been done on lanthanide i hybrid materials by incorporating special host materials such as non-crystalline silica, mesoporous silica, polymer or polymersilica composite, etc. [8–11] Furthermore, the other photoactive building units can be incorporated to assemble the multi-component lanthanide hybrid materials [12–14].
⁎ Corresponding author at: School of Chemical Science and Engineering, Tongji University, Shanghai 200092, China. E-mail address: [email protected] (B. Yan).
https://doi.org/10.1016/j.saa.2019.05.012 1386-1425/© 2019 Elsevier B.V. All rights reserved.
The above-mentioned hybrid materials are mainly the amorphous materials, whose exact composition and structure are hard to determine exactly. So as to overcome the shortcoming of the non-crystalline hybrids, the inorganic crystalline units are tried to be introduced in the hybrid system to further improve the physical and chemical property of them for their crystalline state nature. Nowadays, some typical functional crystalline units are utilized to prepare complicated luminescent lanthanide hybrids. For instance, some semiconductor nanocrystals such as metal oxides and sulfides behave as photoactive species in the construction of multicomponent hybrid materials [15–17]. On the other hand, some structural crystalline units are also introduced into the hybrid materials, such as microporous zeolites or metal-organic frameworks (MOFs). Zeolites are crystalline microporous materials with highly regular nanometer-sized channels or cavities inside, which are widely used in a variety of applications for their unique porous properties [18]. Assembly of organolanthanide complexes into different types of zeolite microcrystals (particularly zeolite L) has attracted much attention in recent years because they can be further modified to be applied as hosts for supramolecular organization of guest molecules or nanostructures [19]. Lanthanide complexes can also be fabricated into zeolite A (ZA) crystals for that it is an aluminosilicate with unique pore size and high capacity of ion exchange to possess a great potential in the encapsulation and assembly of lanthanide complexes [20]. MOFs are an important class of hybrid inorganic–organic
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materials, [21] whose porous crystalline structures can be controlled with a wide range of metal ions and especially organic ligands as linkers [22]. The versatile choice of different building blocks provides the great potential for MOFs materials to embody unique performance of the host–guest interactions within the framework. This enables a wide range of emissive phenomena to be found: linker-based luminescence, the coordinated metal ions based luminescence, antenna effects for energy transfer and sensitization luminescence, excimer and exciplex formation emission, and so on [23–25]. These abundant luminescent behaviors of MOFs materials provide the benefit of them for valuable application for chemical sensing [26,27]. To presence, the effort has been done for the assembly of different units such as mesoporous silica and microporous zeolite or MOFs [28,29]. Particularly, MOFs units are readily to be composed with other building units to achieve the multicomponent hybrid materials [30–33]. These research results provide the strategy to assemble novel kind of multi-component hybrid materials. Herein, we prepare a series of lanthanide micro-mesoporous hybrid materials based with both ZA and MOFs, which are named as ZA-MPTMS-Eu-MOF (Ln = Eu/Tb, MOF = UiO-67 ([Zr6O4(OH)4(bpydc)6]), MOF-253 (Al(OH)(bpydc))) through the chemical assembly strategy. The motivation behind the idea is to study the practicality of different microporous hosts composed together and the photophysical properties of the hybrid systems. The physical characterization and luminescent properties are discussed in details.
conditions. Then the mixture was transferred into a 100 mL Teflonlined stainless steel container and heated at 393 K for 24 h. Sample was washed with DMF and methanol, followed by drying at 80 °C under vacuum. 2.4. Synthesis of MOF-253 A solution of AlCl3·6H2O (151 mg, 0.625 mmol) and sodium acetate (123 mg, 1.5 mmol) in 10 mL DMF. H2bpydc (153 mg, 0.625 mmol) was mixed by stirring for 30 min. The mixture was heated at 393 K for 24 h. The sample was washed with DMF. The product was held under vacuum for 6 h [36]. 2.5. Synthesis of ZA-MPTMS-Ln Firstly Ln(NO3)3·6H2O (Ln = Eu, Tb, 1.0 mmol) was dissolved in ethanol, and then MPTMS (3.0 mmol) was added with the molar ratio 3:1. After being stirred for 1 h, ZA (200 mg) was mixed to be dispersed in toluene and then mixed with above solution. Then final mixture suspension was refluxed at 100 °C for 20 h under argon atmosphere to form ZA-MPTMS-Ln hybrid material. The product was collected by centrifugation, and then washed three times with ethanol and dried at 80 °C under normal atmosphere condition. 2.6. Synthesis of ZA-MPTMS-Ln-UiO-67/MOF-253
2. Experimental section 2.1. Chemicals All of the chemicals were commercially available and used without further purification. AlCl3·6H2O and 2,2′ -bipyridine-5,5′-dicarboxylic acid (H2bpydc) were purchased from Aldrich and used to synthesize MOF-253(Al(OH)(bpydc)). Other chemicals were purchased from Aladdin. H2bpydc, ZrCl4, and glacial acetic acid were used to synthesize UiO67 ([Zr6O4(OH)4(bpydc)6]). Chemically pure and highly crystalline zeolite A (ZA) was synthesized and characterized as described previously [34]. Ln(NO3)3·xH2O (Ln = Eu, Tb) was prepared from their oxides by dissolving in concentrated nitric acid. 3Methacryloxypropyltrimethoxysilane (MPTMS) as bridging monomer was used to modify ZA surface. 2.2. Instrumentation Powder X-ray diffraction patterns (PXRD) were recorded with a Bruker D8 diffractometer using CuKα radiation with 40 mA and 40 kV and the data were collected within the 2θ range of 3–50°. Fourier transform infrared (FTIR) spectra were recorded in the range 4000–500 cm−1 on a Nexus 912 AO446 spectrophotometer using KBr pellets. The elemental analyses (N) of the ternary lanthanide hybrids were measured with a CARIO-ERBA 1106 elemental analyzer. Inductively coupled plasma-mass spectrometry (ICP-MS) data for metal elements were obtained on an X-7 series inductively coupled plasmamass spectrometer (Thermo Elemental, Cheshire, UK). Transmission electron microscopy (TEM) was carried out on a JEOL JEM-2100F electron microscope and operated at 200 kV. Scanning electron microscope (SEM) images were carried out on a Hitachi S-4800. Luminescence excitation and emission spectra of the samples were obtained on Edinburgh FLS920 spectrophotometer using a 450 W xenon lamp as excitation source. 2.3. Synthesis of Uio-67 UiO-67 was prepared by a modified procedure from the literature [35]. We mixed the ligand H2bpydc (0.248 g, 1 mmol), ZrCl4 (0.233 g, 1 mmol), and glacial acetic acid (2.0 g, 33.33 mmol) together in 60 mL N,N′-dimethylformamide (DMF) for 30 min stirring under ambient
ZA-MPTMS-Ln (2.0 g) and UiO-67 (MOF-253) (350 mg) were dispersed in toluene, and the resulting mixture suspension was stirred for 18 h. The solid samples of ZA-MPTMS-Ln-UiO-67/MOF-253 hybrid materials were obtained. The contents of elements (Eu, Tb, Al, and Zr) in the composites were determined with ICP-OES. The content of N was determined by elemental analysis. For ZA-MPTMS-Eu-UiO-67: Eu 4.78%, Zr 5.01%, N 1.45%; for ZA-MPTMS-Tb-UiO-67: Tb 4.71%, Zr 4.80%, N 1.40%; for ZA-MPTMS-Eu-MOF-253: Eu 4.25%, Al 1.40%, N 1.33%; for ZA-MPTMS-Tb-MOF-253: Tb 4.30%, Al 1.40%, N 1.35%. The contents of Ln3+ and N elements are determined to be close to the molar ratio of 1: 2 for Ln3+: MOF-253/UiO-67, corresponding to the reaction ratio of them. 2.7. Fluorescent sensing vapor of ZA-MPTMS-Ln-UiO-67 The ZA-MPTMS-Eu-UiO-67 was used for vapor sensing experiments. Each luminescent spectrum of ZA-MPTMS-Eu-UiO-67 was tested before and after being exposed to various organic solvent vapors (cyclohexane, methanol, ammonia, acetone and ether). ZA-MPTMS-Eu-UiO-67 hybrid material was fixed on the glass through its suspension precipitation, and then it was put into about 25 mL sealed container glass bottle with 6 mL organic solvent, as shown in Fig. S1. Then sealed container glass bottle was put into the oven carefully for 1 h at 30 °C. Then ZA-MPTMS-EuUiO-67 was removed from the container, and its emission spectrum was measured immediately again in the same condition. 3. Results and discussion Fig. 1 shows the scheme of the preparation procedure and basic composition of the multi-component hybrids ZA-MPTMS-Ln-UiO-67/ MOF-253 (Ln = Eu, Tb). Zeolite A (ZA) was firstly modified by silane crosslinking reagent 3-methacryloxypropyltrimethoxysilane (MPTMS) through the covalently grafting, which depends on the hydrolysis and condensation reaction between the surface hydroxyl group over ZA and the alkoyl group of MPTMS. So the MPTMS modified ZA host possesses the covalent linker MPTMS, whose carbonyl group is coordinated to lanthanide ions (Ln3+, Ln = Eu, Tb). MOF-253 and UiO-67 both have the same linker of 2,2′ -bipyridine-5,5′-dicarboxylic acid (H2bpydc), whose two free bipyridine nitrogen atoms can be functionalized by lanthanide ions' chelation [37,38]. Finally, the ternary lanthanide hybrid
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Fig. 1. Scheme for the synthesis procedure of the hybrid (ZA-MPTMS-Ln-UiO-67/MOF253; Ln = Eu, Tb).
material systems were assembled through the coordination interaction, which is identical to the ternary lanthanide complexes of small organic molecules. ZA belongs to microporous crystalline aluminosilicates with a threedimensional network of cavities formed by [AlO4]5− and [SiO4]4− tetrahedra linked via bridging oxygen atoms [34]. The stoichiometry of the synthetized ZA is Na96[(AlO2)96(SiO2)96]·216H2O and its cations Na+ can be readily exchanged by various ions such as Ln3+. MOF-253 belongs to a one-dimensional infinite chains of AlO6 corner-sharing octahedral built by connecting bpydc linkers to construct rhombic shaped pores [35]. UiO-67 is characterized by the fcu structure with two types of cages (the octahedral cages and the tetrahedral cages) [36]. The two MOFs were chosen for the following reasons. Firstly, they display inherent intense ligand-centered emission. Secondly, they have good thermal and chemical stability when exposed to air; and thirdly, their bipyridyl moieties are incorporated as free Lewis basic sites and so can serve as scaffolds to anchor and sensitize lanthanide cations. The selected BET curves and TEM images of the two MOFs are shown in Figs. S2 and S3, respectively. The Langmuir surface areas of Eu-UIO-67 and Eu-MOF-253 were calculated to be 2285 and 330 m2/g. Fig. S4 shows the selected PXRD patterns of ZA-MPTMS-Ln-UiO-67 hybrids: a and b are for Eu and Tb, respectively. Fig. S5 gives the PXRD patterns of ZA-MPTMS-Eu-MOF-253 (top) and ZA-MPTMS-Tb-MOF-253 (bottom). The crystal framework belonging to ZA still can be observed except for its crystallinity becomes weak as pure ZA for the introduction of other functionalized components in the hybrid system. The PXRD of the whole hybrid materials show the main character of ZA host rather than MOFs units for the contents of latter little. The selected SEM pattern of UiO-67 and ZA-MPTMS-Ln-UiO-67 further prove the above result (Fig. S6), which shows the main crystal framework microstructure of ZA with irregular composited MPTMS-Ln-UIO-67 fragments. The IR spectra of ZA, MOF-253/UiO-67, ZA-MPTMS-Ln-MOF-253/ UiO-67 are shown in Fig. S7(a) and (b). The strongest absorption band appearing at 1000 cm−1 is attributed to the T–O bonds (where T = Si or Al) in TO4 tetrahedra of the ZA host structure. The peak at 556 cm−1 is the typical vibrations of the double four-membered rings, which are a part of the secondary building unit forming ZA [39]. It is demonstrated that ZA is successfully covalently grafted to form the
hybrid material ZA-MPTMS-Ln-MOF-253/UiO-67, showing similar infrared absorption bands as the ZA framework. The decrease of the peak intensity at 1719 cm−1 belongs to the carbonyl group of MPTMS, and a new narrow band appears at 1384 cm−1 in IR spectrum. It implies that Ln3+ are coordinated to two oxygen atoms simultaneously respectively from carbonyl groups and the adjacent oxypropyl groups of MPTMS [40]. The coordination between Ln3+ and MPTMS is evidenced. Decrease of the peak intensity at 1420 cm−1 is observed in the FT-IR spectra, which is ascribed to the absorption of bipyridine in MOF-253/ UiO-67 [37,38]. This demonstrates that bipyridine group in MOF-253/ UiO-67 and Ln3+ are coordinated to form the final hybrids ZAMPTMS-Ln- MOF-253/UiO-67. Figs. S8, S9 and S10 show the excitation emission spectra of the units ZA, UiO-67 and MOF-253, respectively. The luminescence spectrum of ZA host under the excitation of 358 nm shows the wide emission bands at the rage of 400–650 nm with two maximum emission peaks at around 440 and 475 nm, respectively (Fig. S8). This is ascribed to the luminescence originated from Si\\O and Al\\O network in ZA host. Figs. S7 and S8 show the similar excitation (368, 376 nm) and emission bands (528, 538 nm) of the two MOFs, which is due to the same bpydc linker to exhibit the identical luminescence of ligand. The little band shift is attributed to the disturbance from different coordinated framework metal ions (Zr4+ and Al3+). More interesting, MOFs and ZA host show the large overlap for both excitation and emission bands. Fig. 2 shows the excitation and emission spectra of ZA-MPTMS-EuUiO-67 (a) and ZA-MPTMS-Tb-UiO-67 (b) hybrids. The two kinds of excitation spectra are obtained by selectively monitoring the 5D0 → 7F2 transition line at 614 nm of Eu3+ and the 5D4 → 7F5 transition line at 545 nm of Tb3+, respectively. For the excitation spectra for Eu3+ and Tb3+, they show the similar feature with a wide broad excitation covering 275–375 nm with the maximum wavelength at 335 nm. This belongs to the excitation of bpydc linker, whose blue shifts to the excitation of UiO-67 are due to the coordination effect of Eu3+ and Tb3 + . No charger transfer state appears in the excitation spectrum of ZAMPTMS-Eu-UiO-67 hybrid. Besides, the weak excitation lines at 397 and 465 nm of Eu3+ ions can be observed from the excitation spectrum (Fig. 2(a)), corresponding to the f-f (7F0 → 5L6 and 7F0 → 5D2) transitions
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Fig. 3(a) and (b) shows the excitation and emission spectra of europium and terbium hybrid materials ZA-MPTMS-Eu-MOF-253 and ZAMPTMS-Tb-MOF-253, respectively. For the excitation spectra of europium hybrid material (Fig. 3(a)), two kinds of excitation bands can be observed. Firstly, a series of sharp lines appear at the range of 300 to 450 nm, which can be ascribed to f–f transitions of Eu3+ ion (394 nm, 7 F0 → 5L6, strongest; 467 nm, 7F0 → 5D2) [41]. Secondly, broad bands ranging from 275 to 375 nm arise from the π–π* transition of the bypdc linker of MOF-253 unit. As a result, the sharp emission peaks assigned to the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions can be seen at about 581, 591, 615, 653 and 685 (702) nm, respectively for Eu3+ ions, indicating that energy transfer occurs in ZA-MPTMS-Eu-MOF-253 hybrid material. While the emission lines assigned to 5D0 → 7F2 transitions are the most intense for the europium hybrid materials, indicating that Eu3+ ion occupies a site without inversion symmetry. Fig. 3(b) for the excitation spectra of hybrid material ZA-MPTMS-Tb-MOF-253 consist of the broad band at the ultraviolet region of 275 to 450 nm, corresponding to the absorption of bypdc linker of MOF-253. The f-f transitions of Tb3+ 4f8 configuration in the longer ultraviolet region are overlapped with the broad bands. The corresponding emission
Fig. 2. (a) Excitation (black line) and emission (red line) spectra of ZA-MPTMS-Eu-UiO-67. (b) Excitation (black line) and emission (green line) spectra of ZA-MATP-Tb-UiO-67.
of Eu3+ ions [41]. The excitation spectrum of ZA-MPTMS-Tb-UiO-67 hybrid also exhibits the sharp excitation lines of f-f transitions of Tb3+ [42]. Checking the two excitation spectra, 335 nm is selected as excitation wavelength to measure the emission spectra of Eu3+ and Tb3+ hybrid system for it is both effective excitation of the two ions. There is no apparent broad emission bands to be observed for either ZA or UiO-67, suggesting that the effective energy transfer take place from bpydc linker to Eu3+ and Tb3+ ions within the hybrid material systems. ZA-MPTMS-Eu-UiO-67 hybrid material exhibits characteristic emissions of Eu ions. Five narrow emission peaks centered at 582, 591, 613, 651, 688 (700) nm, are assigned to 5D0 → 7F0 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 transitions, respectively. Among the peaks, the emission at 613 nm from the 5 D0 → 7F2 induced electronic dipole transition is the strongest, suggesting that the chemical environment around Eu3+ ions has not an inversion center. The emission lines of the hybrid materials ZA-MPTMS-Tb-UiO67 are assigned to the transitions from the 5D4 → 7FJ (J = 6, 5, 4, 3) transitions at around 489, 543, 582 and 623 nm for terbium ions. Among these emission peaks, the green luminescence (5D4 → 7F5) is most striking, which indicates that the effective energy transfer take place between bpydc of UiO-67 and the chelated Tb3+ ions.
Fig. 3. (a) Excitation (black line) and emission (red line) spectra of ZA- MPTMS -EuMOF253. (b) Excitation (black line) and emission (green line) spectra of ZA-MATP-TbMOF253.
J. Ma, B. Yan / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117107
spectra of the terbium hybrid materials present the sharp emission peaks assigned to the transitions 5D4 → 7FJ (J = 6, 5, 4, 3) at 490, 545, 582 and 620 nm, respectively for Tb3+ ions, indicating that the conjugated systems form between bypdc linker of MOF-253 unit in ZAMPTMS-Tb-MOF-253 hybrids. ZA-MPTMS-Eu-UiO-67 is selected to check the possible photo response to different solvent vapors. The film fabricated with ZAMPTMS-Eu-UiO-67 is prepared over a glass substrate, which is exposed to various volatile solvents for 1 h. It is evident that the luminescent intensities of the hybrid film display the apparent response to ammonia, which exhibits a significant quenching effect. Both the luminescent spectra (a) and the corresponding histograms (b) are shown in Fig. 4. The histograms are obtained by comparing the spectral band intensity of the 5D0 → 7F2 transition at 614 nm for Eu3+ ion upon the hybrid system exposure to several solvent molecule vapors. The hybrid film shows luminescence quenching when exposing it to ammonia vapors. Luminescence intensity is invariable upon exposing to vapors of acetone, cyclohexane, ether and methanol. Furtherly, the concentration test is taken in order to investigate the luminescence intensities of the ZA-MPTMS-Eu-UiO-67 hybrid film for ammonia. The fluorescence changes are shown in Fig. 5a by exposing
Fig. 4. Emission spectra (a) and the intensity change of luminescence spectra of the 5D0 → 7F2 transition at 614 nm (b) of ZA-MPTMS-Eu-UiO-67 hybrid under 327 nm exposure to several vapors (blank, ammonia, cyclohexane, methanol, acetone and ether).
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to various concentrations of ammonia gas, whose results verify that the Eu3+ emission intensity of ZA-MPTMS-Eu-UiO-67 gradually decreases with the successive increasing ammonia concentration. Fig. 5b plots the dependence of Ik/I0 (K = 40, 80, 120, 160, 200 ppm) on the ammonia concentration, whose relative ratios (Ik/I0) are calculated based on the data shown in histograms (b) are shown inFig. 5a. The final result data reveals that Ik/I0 and ammonia concentration have a good linear relationship in the range of 0–200 ppm. The linear relationship is fitted as a function of Eq. (1) with a correlation coefficient (R2) of 0.99308, whose limit of detection (LOD) for ammonia vapors is 8.4238 ppm, calculated as 3σ/k [43] (σ for the standard deviation for ten replicating detections of the blank, and k for the slope of the calibration curve). The result implies that ZA-MPTMS-Eu-UiO-67 is a luminescent sensor for the quantitative analysis of ammonia. Ik =I0 ¼ 1:01413−0:00346Cammonia
ð1Þ
Then we do the concentration test of other organic solvent vapors (cyclohexane, methanol, acetone and ether) in Figs. S11 and S12. The results show that the intensity is barely change of luminescence spectra of the 5D0 → 7F2 transition at 614 nm upon ZA-MPTMS-Eu-UiO-67 exposure to various concentrations (0, 40, 80, 120, 160, 200 ppm) solvent molecule vapors (cyclohexane, methanol, acetone and ether). It is that
Fig. 5. The emission intensity comparison of ZA-MPTMS-Eu-UiO-67 under excitation of 327 nm when exposing to various concentrations of ammonia gas (a); and the relationship between the relative ratios (Ik/I0, K = 40, 80, 120, 160, 200 ppm) and the concentration of ammonia (b).
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the Eu3+ emission intensity of ZA-MPTMS-Eu-UiO-67 is barely related to the concentration of acetone, cyclohexane, methanol and ether. In order to test the response rate of ZA-MPTMS-Eu-UiO-67 hybrid film as gas sensor, the real-time sensing of NH3 vapors is implemented by the hybrid film (see the time-dependent fluorescence quenching profile in Fig. S13a). The results show that the luminescence intensity of the film is significantly reduced and the luminescence quenching reaches a maximum with a quenching percentage of 73% at 240 s, which is a very fast luminescence response of the sensor to NH3. Repeatability for a sensory material is a very important parameter to assess the sensor's practicability. After detection of NH3, the luminescence intensity of the hybrid film gradually return to its initial value after exposure to ambient air for 10 min due to the volatilization of NH3 (Fig. S13b). 4. Conclusions In summary, the multi-component assembly based with two different microporous units (zeolite A (ZA) and metal-organic framework MOFs) have been achieved to lanthanide hybrid materials. 3Methacryloxypropyltrimethoxysilane (MPTMS) covalently modified ZA and 2,2′ -bipyridine-5,5′-dicarboxyliate (bpydc) linked MOFs (UiO67 and MOF-253) are assembled together with lanthanide ions (Eu3+, Tb3+) through the coordination interaction. These hybrid materials ZA-MPTMS-Eu(Tb)-UiO-67(MOF-253) display the characteristic luminescence of lanthanide ions themselves, suggesting the effective energy transfer from the linker bpydc of MOFs to lanthanide ions. Furthermore, ZA-MPTMS-Eu(Tb)-UiO-67 hybrid system is selected to check its luminescent response to volatile solvent vapor, revealing the luminescence quenching effect on ammonia, while not one volatile organic solvents. These research results provide the strategy to assemble novel kind of multi-component hybrid materials, which is useful to have potential applications in optical material or sensing. Acknowledgment This work was supported by the National Natural Science Foundation of China (21571142), and the Developing Science Funds of Tongji University. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.saa.2019.05.012. References [1] J.M. Stanley, B.J. Holliday, Luminescent lanthanide-containing metallopolymers, Coord. Chem. Rev. 256 (2012) 1520–1530. [2] J.C.G. Bunzli, On the design of highly luminescent lanthanide complexes, Coord. Chem. Rev. 293 (2015) 19–47. [3] B. Yan, Photofunctional Rare Earth Hybrid Materials, Springer, Singapore, 2017. [4] L.D. Carlos, R.A.S. Ferreira, V.D. Bermudez, S.J.L. Ribeiro, Lanthanide-containing lightemitting organic-inorganic hybrids: a bet on the future, Adv. Mater. 21 (2009) 509–534. [5] K. Binnemans, Lanthanide-based luminescent hybrid materials, Chem. Rev. 109 (2009) 4283–4374. [6] B. Yan, Recent progress in photofunctional lanthanide hybrid materials, RSC Adv. 2 (2012) 9304–9324. [7] J. Feng, H.J. Zhang, Hybrid materials based on lanthanide organic complexes: a review, Chem. Soc. Rev. 42 (2013) 387–411. [8] L.M. Zhao, X. Shao, Y.B. Yin, W.Z. Li, Luminescence of novel terbium complex/inorganic/polymeric hybrid materials based on sol–gel technology, Mater. Sci. Eng. B 177 (2012) 257–262. [9] Y. Li, J.L. Wang, W. Chain, X. Wang, J. Zhao, X.Q. Li, Coordination assembly and characterization of europium(III) complexes covalently bonded to SBA-15 directly functionalized by modified polymer, RSC Adv. 3 (2013) 14057–14065. [10] Q.P. Li, B. Yan, Multi-walled carbon nanotube-based ternary rare earth (Eu3+, Tb3+) hybrid materials with organically modified silica-oxygen bridge, J. Colloid Interface Sci. 380 (2012) 67–74. [11] Y.Y. Li, B. Yan, Q.P. Li, Bifunctional heterometallic Ln3+-Gd3+ (Ln = Eu, Tb) hybrid silica microspheres: luminescence and MRI contrast agent property, Dalton Trans. 42 (2013) 1678–1686.
[12] Y.J. Li, B. Yan, Preparation, characterization and luminescence properties of the ternary europium complexes covalently bonded to titania and mesoporous SBA-15, J. Mater. Chem. 21 (2011) 8129–8136. [13] B. Yan, Y.J. Li, Photoactive lanthanide (Eu3+, Tb3+) centered hybrid systems with titania-mesoporous silica/aluminum mesoporous silica based hosts, J. Mater. Chem. 21 (2011) 18454–18461. [14] J. Cuan, B. Yan, Photofunctional hybrid materials with polyoxometalates and benzoate modified mesoporous silica through double functional imidazolium ionic liquid linkage, Microporous Mesoporous Mater. 183 (2014) 9–16. [15] B. Yan, Y.F. Shao, Multifunctional nanocomposites of lanthanide (Eu3+, Tb3+) complex functionalized magnetic mesoporous silica nanospheres covalently bonded with ZnO-polymer, Dalton Trans. 42 (2013) 9565–9573. [16] Y. Mei, Y. Lu, B. Yan, Multi-component hybrid soft gels containing Eu3+ complexes and MS (M = Zn, Cd) nanoparticles assembled with mercapto- ion liquid linkage: adjustable color and white luminescence, New J. Chem. 37 (2013) 2619–2623. [17] Y. Zhao, B. Yan, Rare earth (Eu3+, Tb3+)/β-diketonate functionalized mesoporous SBA-15/GaN nanocomposites: multi-component chemical bonding assembly, characterization and luminescence, J. Colloid Interface Sci. 395 (2013) 145–153. [18] E.M. Flanigen, Zeolites and molecular sieves. An historical perspective, in: H. Van Bekkum, E.M. Flanigen (Eds.), Introduction to Zeolite Science and Practice, 2nd edi, Stud. Surf. Sci. Catal, vol. 137, Jensen JC, Jacobs PA 2001, pp. 11–35. [19] H.R. Li, Y. Wang, P.P. Cao, Y.X. Ding, H.H. Zhang, X.J. Hu, T.T. Wen, Recent progress in host–guest luminescent functional materials based on lanthanide/zeolite L, Sci. China Chem. 42 (2012) 1–18 in Chin. [20] J.N. Hao, B. Yan, Photofunctional host-guest hybrid materials and thin film of lanthanide complexes covalently linked to functionalized zeolite A, Dalton Trans. 43 (2014) 2810–2818. [21] D. Zhao, D.J. Timmons, D.Q. Yuan, H.C. Zhou, Tuning the topology and functionality of metal-organic frameworks by ligand design, Acc. Chem. Res. 44 (2011) 123–133. [22] M. O'Keeffe, O.M. Yaghi, Deconstructing the crystal structures of metal-organic frameworks and related materials into their underlying nets, Chem. Rev. 112 (2012) 675–702. [23] M.D. Allendorf, C.A. Bauer, R.K. Bhakta, R.J.T. Houk, Luminescent metal–organic frameworks, Chem. Soc. Rev. 38 (2009) 1330–1352. [24] Y.J. Cui, Y.F. Yue, G.D. Qian, B.L. Chen, Luminescent functional metal-organic frameworks, Chem. Rev. 112 (2012) 1126–1162. [25] J. Rocha, L.D. Carlos, F.A. Almeida Paz, D. Ananiasa, Luminescent multifunctional lanthanides-based metal-organic frameworks, Chem. Soc. Rev. 40 (2011) 926–940. [26] W.P. Lustig, S. Mukherjee, N.D. Rudd, A.V. Desai, J. Li, S.K. Ghosh, Metal-organic frameworks: functional luminescent and photonic materials for sensing applications, Chem. Soc. Rev. 46 (2017) 2132–3285. [27] B. Yan, Lanthanie functionalized metal-organic frameworks hybrid systems to create multiple luminescent centers for chemical sensing, Acc. Chem. Res. 50 (2017) 2789–2798. [28] L. Chen, B. Yan, Multi-component assembly and luminescence tuning of lanthanide hybrids based with both zeolite L/A and SBA-15 through two organically grafted linkers, Dalton Trans. 43 (2014) 14123–14131. [29] X. Lian, B. Yan, Multi-component luminescent lanthanide hybrids of both functionalized IR-MOF-3 and SBA-15, New J. Chem. 39 (2015) 5898–5901. [30] X.Y. Xu, B. Yan, Novel photofunctional hybrid materials (alumina and titania) functionalized with both MOF and lanthanide complexes through coordination bonds, RSC Adv. 4 (2014) 38761–38768. [31] J. Ma, B. Yan, Multi-component hybrid soft ionogels for photoluminescence tuning and sensing organic solvent vapors, J. Colloid Interface Sci. 513 (2018) 133–140. [32] J. Ma, B. Yan, Novel hybrid materials of lanthanide coordination polymers ion exchanged Mg-Al layered double hydroxide: multi-color photoluminescence and white color thin film, Dyes Pigments 153 (2018) 266–274. [33] J. Ma, B. Yan, Multi-component hybrid films based on covalent post-synthetic functionalization of silicon chip using both ZIF-90 and lanthanide complexes for luminescence tuning, New J. Chem. 42 (2018) 15061–15067. [34] P. Laine, R. Seifert, R. Giovanoli, G. Calzaferri, A convenient preparation of closepacked monograin layers of pure zeolite A microcrystals, New J. Chem. 21 (1997) 453–460. [35] L.J. Li, S.F. Tang, C. Wang, X.X. Lv, M. Jiang, H.Z. Wu, X.B. Zhao, High gas storage capacities and stepwise adsorption in a UiO type metal–organic framework incorporating Lewis basic bipyridyl sites, Chem. Commun. 50 (2014) 2304–2307. [36] E.D. Bloch, D. Britt, C. Lee, C.J. Doonan, F.J. Uribe-Romo, H. Furukawa, J.R. Long, O.M. Yaghi, Metal insertion in a microporous metal-organic framework lined with 2,2′bipyridine, J. Am. Chem. Soc. 132 (2010) 14382–14384. [37] Y. Lu, B. Yan, A novel luminescent monolayer thin film based on postsynthetic method and functional linker, J. Mater. Chem. C 2 (2014) 5526–5532. [38] Y. Zhou, B. Yan, Ratiometric detection of temperature using responsive dualemissive MOF hybrids, J. Mater. Chem. C 3 (2015) 9353–9358. [39] J.N. Hao, B. Yan, Hybrid polymer thin films with a lanthanide–zeolite a host–guest system: coordination bonding assembly and photo-integration, New J. Chem. 38 (2014) 3540–3547. [40] Q.M. Wang, B. Yan, From molecules to materials: a new way to construct luminescent chemical bonded hybrid systems based with ternary lanthanide complexes of 1,10-phenanthroline, Inorg. Chem. Commun. 7 (2004) 1124–1127. [41] W.T. Carnall, P.R. Fields, K. Rajnak, Electronic energy levels of the trivalent lanthanide aquo ions. IV. Eu3+, J. Chem. Phys. 49 (1968) 4450–4455. [42] W.T. Carnall, P.R. Fields, K. Rajnak, Electronic energy levels of the trivalent lanthanide aquo ions. III. Tb3+, J. Chem. Phys. 49 (1968) 4447–4449. [43] A. M. Committee, Recommendations for the definition, estimation and use of the detection limit, Analyst 112 (1987) 199–204.
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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Multi-component luminescence responsive Eu3+/Tb3+ hybrids based with metal-organic frameworks and zeolites A Jing Ma b, Bing Yan a,b,⁎ a b
School of Materials Science and Engineering, Liaocheng University, Liaocheng 252059, China School of Chemical Science and Engineering, Tongji University, Shanghai 200092, China
a r t i c l e
i n f o
Article history: Received 29 November 2018 Received in revised form 4 May 2019 Accepted 9 May 2019 Available online 10 May 2019 Keywords: Multi-component hybrid material Lanthanide ion Zeolite A Metal-organic frameworks Luminescence
a b s t r a c t Both Zeolite A (ZA) and two kinds of 2,2′-bipyridine-5,5′-dicarboxylic acid (H2bpydc) linking meta-organic frameworks (MOFs) (MOF-253 (Al(OH)(bpydc)) and UiO-67 ([Zr6O4(OH)4(bpydc)6])) have been used to construct novel photofunctional multi-component lanthanide hybrid materials through covalent-coordination cooperative assembly. Microporous ZA is firstly functionalized by covalently grafting of the surface hydroxyl groups using special silane crosslinking reagent 3-methacryloxypropyltrimethoxysilane (MPTMS). Then the multicomponent assembly are realized by coordination interaction between lanthanide ions (Eu3+/Tb3+), ZA through the carbonyl group of MPTMS unit and MOF-253 (or UiO-67) through the double nitrogen of bpydc linker. Subsequently, the obtained multicomponent hybrid materials (ZA-MPTMS-Eu/Tb-MOF-253(UiO-67)) are characterized by means of XRD, FT-IR, SEM and especially the photoluminescence properties are studied in details. These hybrids with both ZA and MOFs host show the main characteristic crystal framework morphology of ZA together with the composition of MOFs. They display the feature luminescence of Eu3+/Tb3+ ions for the energy transfer from bpydc linker of MOFs. Furthermore, ZA-MPTMS-Eu-UiO-67 hybrid material is selected to check the luminescence response to volatile substances, whose luminescence quenching is found for ammonia vapor. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Lanthanide coordination compounds have attracted extensive interest for their special luminescent feature such as intense and wide emission bands, broad range of decay lifetime and high color purity [1,2]. Nevertheless, organolanthanide complexes are difficult to be used directly in practical applications due to the limit of their poor thermal and photo stability. In order to solve this problem, lanthanide inorganic–organic hybrid materials are developed to integrate the respective characteristics of inorganic and organic components and produce the eminent properties [3]. All kinds of building units introduced into these hybrids make them to have the expected potential applications in the practical fields such as in devices, amplifiers and chemical sensors etc. [4–7] To presence, much research works have been done on lanthanide i hybrid materials by incorporating special host materials such as non-crystalline silica, mesoporous silica, polymer or polymersilica composite, etc. [8–11] Furthermore, the other photoactive building units can be incorporated to assemble the multi-component lanthanide hybrid materials [12–14].
⁎ Corresponding author at: School of Chemical Science and Engineering, Tongji University, Shanghai 200092, China. E-mail address: [email protected] (B. Yan).
https://doi.org/10.1016/j.saa.2019.05.012 1386-1425/© 2019 Elsevier B.V. All rights reserved.
The above-mentioned hybrid materials are mainly the amorphous materials, whose exact composition and structure are hard to determine exactly. So as to overcome the shortcoming of the non-crystalline hybrids, the inorganic crystalline units are tried to be introduced in the hybrid system to further improve the physical and chemical property of them for their crystalline state nature. Nowadays, some typical functional crystalline units are utilized to prepare complicated luminescent lanthanide hybrids. For instance, some semiconductor nanocrystals such as metal oxides and sulfides behave as photoactive species in the construction of multicomponent hybrid materials [15–17]. On the other hand, some structural crystalline units are also introduced into the hybrid materials, such as microporous zeolites or metal-organic frameworks (MOFs). Zeolites are crystalline microporous materials with highly regular nanometer-sized channels or cavities inside, which are widely used in a variety of applications for their unique porous properties [18]. Assembly of organolanthanide complexes into different types of zeolite microcrystals (particularly zeolite L) has attracted much attention in recent years because they can be further modified to be applied as hosts for supramolecular organization of guest molecules or nanostructures [19]. Lanthanide complexes can also be fabricated into zeolite A (ZA) crystals for that it is an aluminosilicate with unique pore size and high capacity of ion exchange to possess a great potential in the encapsulation and assembly of lanthanide complexes [20]. MOFs are an important class of hybrid inorganic–organic
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materials, [21] whose porous crystalline structures can be controlled with a wide range of metal ions and especially organic ligands as linkers [22]. The versatile choice of different building blocks provides the great potential for MOFs materials to embody unique performance of the host–guest interactions within the framework. This enables a wide range of emissive phenomena to be found: linker-based luminescence, the coordinated metal ions based luminescence, antenna effects for energy transfer and sensitization luminescence, excimer and exciplex formation emission, and so on [23–25]. These abundant luminescent behaviors of MOFs materials provide the benefit of them for valuable application for chemical sensing [26,27]. To presence, the effort has been done for the assembly of different units such as mesoporous silica and microporous zeolite or MOFs [28,29]. Particularly, MOFs units are readily to be composed with other building units to achieve the multicomponent hybrid materials [30–33]. These research results provide the strategy to assemble novel kind of multi-component hybrid materials. Herein, we prepare a series of lanthanide micro-mesoporous hybrid materials based with both ZA and MOFs, which are named as ZA-MPTMS-Eu-MOF (Ln = Eu/Tb, MOF = UiO-67 ([Zr6O4(OH)4(bpydc)6]), MOF-253 (Al(OH)(bpydc))) through the chemical assembly strategy. The motivation behind the idea is to study the practicality of different microporous hosts composed together and the photophysical properties of the hybrid systems. The physical characterization and luminescent properties are discussed in details.
conditions. Then the mixture was transferred into a 100 mL Teflonlined stainless steel container and heated at 393 K for 24 h. Sample was washed with DMF and methanol, followed by drying at 80 °C under vacuum. 2.4. Synthesis of MOF-253 A solution of AlCl3·6H2O (151 mg, 0.625 mmol) and sodium acetate (123 mg, 1.5 mmol) in 10 mL DMF. H2bpydc (153 mg, 0.625 mmol) was mixed by stirring for 30 min. The mixture was heated at 393 K for 24 h. The sample was washed with DMF. The product was held under vacuum for 6 h [36]. 2.5. Synthesis of ZA-MPTMS-Ln Firstly Ln(NO3)3·6H2O (Ln = Eu, Tb, 1.0 mmol) was dissolved in ethanol, and then MPTMS (3.0 mmol) was added with the molar ratio 3:1. After being stirred for 1 h, ZA (200 mg) was mixed to be dispersed in toluene and then mixed with above solution. Then final mixture suspension was refluxed at 100 °C for 20 h under argon atmosphere to form ZA-MPTMS-Ln hybrid material. The product was collected by centrifugation, and then washed three times with ethanol and dried at 80 °C under normal atmosphere condition. 2.6. Synthesis of ZA-MPTMS-Ln-UiO-67/MOF-253
2. Experimental section 2.1. Chemicals All of the chemicals were commercially available and used without further purification. AlCl3·6H2O and 2,2′ -bipyridine-5,5′-dicarboxylic acid (H2bpydc) were purchased from Aldrich and used to synthesize MOF-253(Al(OH)(bpydc)). Other chemicals were purchased from Aladdin. H2bpydc, ZrCl4, and glacial acetic acid were used to synthesize UiO67 ([Zr6O4(OH)4(bpydc)6]). Chemically pure and highly crystalline zeolite A (ZA) was synthesized and characterized as described previously [34]. Ln(NO3)3·xH2O (Ln = Eu, Tb) was prepared from their oxides by dissolving in concentrated nitric acid. 3Methacryloxypropyltrimethoxysilane (MPTMS) as bridging monomer was used to modify ZA surface. 2.2. Instrumentation Powder X-ray diffraction patterns (PXRD) were recorded with a Bruker D8 diffractometer using CuKα radiation with 40 mA and 40 kV and the data were collected within the 2θ range of 3–50°. Fourier transform infrared (FTIR) spectra were recorded in the range 4000–500 cm−1 on a Nexus 912 AO446 spectrophotometer using KBr pellets. The elemental analyses (N) of the ternary lanthanide hybrids were measured with a CARIO-ERBA 1106 elemental analyzer. Inductively coupled plasma-mass spectrometry (ICP-MS) data for metal elements were obtained on an X-7 series inductively coupled plasmamass spectrometer (Thermo Elemental, Cheshire, UK). Transmission electron microscopy (TEM) was carried out on a JEOL JEM-2100F electron microscope and operated at 200 kV. Scanning electron microscope (SEM) images were carried out on a Hitachi S-4800. Luminescence excitation and emission spectra of the samples were obtained on Edinburgh FLS920 spectrophotometer using a 450 W xenon lamp as excitation source. 2.3. Synthesis of Uio-67 UiO-67 was prepared by a modified procedure from the literature [35]. We mixed the ligand H2bpydc (0.248 g, 1 mmol), ZrCl4 (0.233 g, 1 mmol), and glacial acetic acid (2.0 g, 33.33 mmol) together in 60 mL N,N′-dimethylformamide (DMF) for 30 min stirring under ambient
ZA-MPTMS-Ln (2.0 g) and UiO-67 (MOF-253) (350 mg) were dispersed in toluene, and the resulting mixture suspension was stirred for 18 h. The solid samples of ZA-MPTMS-Ln-UiO-67/MOF-253 hybrid materials were obtained. The contents of elements (Eu, Tb, Al, and Zr) in the composites were determined with ICP-OES. The content of N was determined by elemental analysis. For ZA-MPTMS-Eu-UiO-67: Eu 4.78%, Zr 5.01%, N 1.45%; for ZA-MPTMS-Tb-UiO-67: Tb 4.71%, Zr 4.80%, N 1.40%; for ZA-MPTMS-Eu-MOF-253: Eu 4.25%, Al 1.40%, N 1.33%; for ZA-MPTMS-Tb-MOF-253: Tb 4.30%, Al 1.40%, N 1.35%. The contents of Ln3+ and N elements are determined to be close to the molar ratio of 1: 2 for Ln3+: MOF-253/UiO-67, corresponding to the reaction ratio of them. 2.7. Fluorescent sensing vapor of ZA-MPTMS-Ln-UiO-67 The ZA-MPTMS-Eu-UiO-67 was used for vapor sensing experiments. Each luminescent spectrum of ZA-MPTMS-Eu-UiO-67 was tested before and after being exposed to various organic solvent vapors (cyclohexane, methanol, ammonia, acetone and ether). ZA-MPTMS-Eu-UiO-67 hybrid material was fixed on the glass through its suspension precipitation, and then it was put into about 25 mL sealed container glass bottle with 6 mL organic solvent, as shown in Fig. S1. Then sealed container glass bottle was put into the oven carefully for 1 h at 30 °C. Then ZA-MPTMS-EuUiO-67 was removed from the container, and its emission spectrum was measured immediately again in the same condition. 3. Results and discussion Fig. 1 shows the scheme of the preparation procedure and basic composition of the multi-component hybrids ZA-MPTMS-Ln-UiO-67/ MOF-253 (Ln = Eu, Tb). Zeolite A (ZA) was firstly modified by silane crosslinking reagent 3-methacryloxypropyltrimethoxysilane (MPTMS) through the covalently grafting, which depends on the hydrolysis and condensation reaction between the surface hydroxyl group over ZA and the alkoyl group of MPTMS. So the MPTMS modified ZA host possesses the covalent linker MPTMS, whose carbonyl group is coordinated to lanthanide ions (Ln3+, Ln = Eu, Tb). MOF-253 and UiO-67 both have the same linker of 2,2′ -bipyridine-5,5′-dicarboxylic acid (H2bpydc), whose two free bipyridine nitrogen atoms can be functionalized by lanthanide ions' chelation [37,38]. Finally, the ternary lanthanide hybrid
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Fig. 1. Scheme for the synthesis procedure of the hybrid (ZA-MPTMS-Ln-UiO-67/MOF253; Ln = Eu, Tb).
material systems were assembled through the coordination interaction, which is identical to the ternary lanthanide complexes of small organic molecules. ZA belongs to microporous crystalline aluminosilicates with a threedimensional network of cavities formed by [AlO4]5− and [SiO4]4− tetrahedra linked via bridging oxygen atoms [34]. The stoichiometry of the synthetized ZA is Na96[(AlO2)96(SiO2)96]·216H2O and its cations Na+ can be readily exchanged by various ions such as Ln3+. MOF-253 belongs to a one-dimensional infinite chains of AlO6 corner-sharing octahedral built by connecting bpydc linkers to construct rhombic shaped pores [35]. UiO-67 is characterized by the fcu structure with two types of cages (the octahedral cages and the tetrahedral cages) [36]. The two MOFs were chosen for the following reasons. Firstly, they display inherent intense ligand-centered emission. Secondly, they have good thermal and chemical stability when exposed to air; and thirdly, their bipyridyl moieties are incorporated as free Lewis basic sites and so can serve as scaffolds to anchor and sensitize lanthanide cations. The selected BET curves and TEM images of the two MOFs are shown in Figs. S2 and S3, respectively. The Langmuir surface areas of Eu-UIO-67 and Eu-MOF-253 were calculated to be 2285 and 330 m2/g. Fig. S4 shows the selected PXRD patterns of ZA-MPTMS-Ln-UiO-67 hybrids: a and b are for Eu and Tb, respectively. Fig. S5 gives the PXRD patterns of ZA-MPTMS-Eu-MOF-253 (top) and ZA-MPTMS-Tb-MOF-253 (bottom). The crystal framework belonging to ZA still can be observed except for its crystallinity becomes weak as pure ZA for the introduction of other functionalized components in the hybrid system. The PXRD of the whole hybrid materials show the main character of ZA host rather than MOFs units for the contents of latter little. The selected SEM pattern of UiO-67 and ZA-MPTMS-Ln-UiO-67 further prove the above result (Fig. S6), which shows the main crystal framework microstructure of ZA with irregular composited MPTMS-Ln-UIO-67 fragments. The IR spectra of ZA, MOF-253/UiO-67, ZA-MPTMS-Ln-MOF-253/ UiO-67 are shown in Fig. S7(a) and (b). The strongest absorption band appearing at 1000 cm−1 is attributed to the T–O bonds (where T = Si or Al) in TO4 tetrahedra of the ZA host structure. The peak at 556 cm−1 is the typical vibrations of the double four-membered rings, which are a part of the secondary building unit forming ZA [39]. It is demonstrated that ZA is successfully covalently grafted to form the
hybrid material ZA-MPTMS-Ln-MOF-253/UiO-67, showing similar infrared absorption bands as the ZA framework. The decrease of the peak intensity at 1719 cm−1 belongs to the carbonyl group of MPTMS, and a new narrow band appears at 1384 cm−1 in IR spectrum. It implies that Ln3+ are coordinated to two oxygen atoms simultaneously respectively from carbonyl groups and the adjacent oxypropyl groups of MPTMS [40]. The coordination between Ln3+ and MPTMS is evidenced. Decrease of the peak intensity at 1420 cm−1 is observed in the FT-IR spectra, which is ascribed to the absorption of bipyridine in MOF-253/ UiO-67 [37,38]. This demonstrates that bipyridine group in MOF-253/ UiO-67 and Ln3+ are coordinated to form the final hybrids ZAMPTMS-Ln- MOF-253/UiO-67. Figs. S8, S9 and S10 show the excitation emission spectra of the units ZA, UiO-67 and MOF-253, respectively. The luminescence spectrum of ZA host under the excitation of 358 nm shows the wide emission bands at the rage of 400–650 nm with two maximum emission peaks at around 440 and 475 nm, respectively (Fig. S8). This is ascribed to the luminescence originated from Si\\O and Al\\O network in ZA host. Figs. S7 and S8 show the similar excitation (368, 376 nm) and emission bands (528, 538 nm) of the two MOFs, which is due to the same bpydc linker to exhibit the identical luminescence of ligand. The little band shift is attributed to the disturbance from different coordinated framework metal ions (Zr4+ and Al3+). More interesting, MOFs and ZA host show the large overlap for both excitation and emission bands. Fig. 2 shows the excitation and emission spectra of ZA-MPTMS-EuUiO-67 (a) and ZA-MPTMS-Tb-UiO-67 (b) hybrids. The two kinds of excitation spectra are obtained by selectively monitoring the 5D0 → 7F2 transition line at 614 nm of Eu3+ and the 5D4 → 7F5 transition line at 545 nm of Tb3+, respectively. For the excitation spectra for Eu3+ and Tb3+, they show the similar feature with a wide broad excitation covering 275–375 nm with the maximum wavelength at 335 nm. This belongs to the excitation of bpydc linker, whose blue shifts to the excitation of UiO-67 are due to the coordination effect of Eu3+ and Tb3 + . No charger transfer state appears in the excitation spectrum of ZAMPTMS-Eu-UiO-67 hybrid. Besides, the weak excitation lines at 397 and 465 nm of Eu3+ ions can be observed from the excitation spectrum (Fig. 2(a)), corresponding to the f-f (7F0 → 5L6 and 7F0 → 5D2) transitions
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Fig. 3(a) and (b) shows the excitation and emission spectra of europium and terbium hybrid materials ZA-MPTMS-Eu-MOF-253 and ZAMPTMS-Tb-MOF-253, respectively. For the excitation spectra of europium hybrid material (Fig. 3(a)), two kinds of excitation bands can be observed. Firstly, a series of sharp lines appear at the range of 300 to 450 nm, which can be ascribed to f–f transitions of Eu3+ ion (394 nm, 7 F0 → 5L6, strongest; 467 nm, 7F0 → 5D2) [41]. Secondly, broad bands ranging from 275 to 375 nm arise from the π–π* transition of the bypdc linker of MOF-253 unit. As a result, the sharp emission peaks assigned to the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions can be seen at about 581, 591, 615, 653 and 685 (702) nm, respectively for Eu3+ ions, indicating that energy transfer occurs in ZA-MPTMS-Eu-MOF-253 hybrid material. While the emission lines assigned to 5D0 → 7F2 transitions are the most intense for the europium hybrid materials, indicating that Eu3+ ion occupies a site without inversion symmetry. Fig. 3(b) for the excitation spectra of hybrid material ZA-MPTMS-Tb-MOF-253 consist of the broad band at the ultraviolet region of 275 to 450 nm, corresponding to the absorption of bypdc linker of MOF-253. The f-f transitions of Tb3+ 4f8 configuration in the longer ultraviolet region are overlapped with the broad bands. The corresponding emission
Fig. 2. (a) Excitation (black line) and emission (red line) spectra of ZA-MPTMS-Eu-UiO-67. (b) Excitation (black line) and emission (green line) spectra of ZA-MATP-Tb-UiO-67.
of Eu3+ ions [41]. The excitation spectrum of ZA-MPTMS-Tb-UiO-67 hybrid also exhibits the sharp excitation lines of f-f transitions of Tb3+ [42]. Checking the two excitation spectra, 335 nm is selected as excitation wavelength to measure the emission spectra of Eu3+ and Tb3+ hybrid system for it is both effective excitation of the two ions. There is no apparent broad emission bands to be observed for either ZA or UiO-67, suggesting that the effective energy transfer take place from bpydc linker to Eu3+ and Tb3+ ions within the hybrid material systems. ZA-MPTMS-Eu-UiO-67 hybrid material exhibits characteristic emissions of Eu ions. Five narrow emission peaks centered at 582, 591, 613, 651, 688 (700) nm, are assigned to 5D0 → 7F0 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 transitions, respectively. Among the peaks, the emission at 613 nm from the 5 D0 → 7F2 induced electronic dipole transition is the strongest, suggesting that the chemical environment around Eu3+ ions has not an inversion center. The emission lines of the hybrid materials ZA-MPTMS-Tb-UiO67 are assigned to the transitions from the 5D4 → 7FJ (J = 6, 5, 4, 3) transitions at around 489, 543, 582 and 623 nm for terbium ions. Among these emission peaks, the green luminescence (5D4 → 7F5) is most striking, which indicates that the effective energy transfer take place between bpydc of UiO-67 and the chelated Tb3+ ions.
Fig. 3. (a) Excitation (black line) and emission (red line) spectra of ZA- MPTMS -EuMOF253. (b) Excitation (black line) and emission (green line) spectra of ZA-MATP-TbMOF253.
J. Ma, B. Yan / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117107
spectra of the terbium hybrid materials present the sharp emission peaks assigned to the transitions 5D4 → 7FJ (J = 6, 5, 4, 3) at 490, 545, 582 and 620 nm, respectively for Tb3+ ions, indicating that the conjugated systems form between bypdc linker of MOF-253 unit in ZAMPTMS-Tb-MOF-253 hybrids. ZA-MPTMS-Eu-UiO-67 is selected to check the possible photo response to different solvent vapors. The film fabricated with ZAMPTMS-Eu-UiO-67 is prepared over a glass substrate, which is exposed to various volatile solvents for 1 h. It is evident that the luminescent intensities of the hybrid film display the apparent response to ammonia, which exhibits a significant quenching effect. Both the luminescent spectra (a) and the corresponding histograms (b) are shown in Fig. 4. The histograms are obtained by comparing the spectral band intensity of the 5D0 → 7F2 transition at 614 nm for Eu3+ ion upon the hybrid system exposure to several solvent molecule vapors. The hybrid film shows luminescence quenching when exposing it to ammonia vapors. Luminescence intensity is invariable upon exposing to vapors of acetone, cyclohexane, ether and methanol. Furtherly, the concentration test is taken in order to investigate the luminescence intensities of the ZA-MPTMS-Eu-UiO-67 hybrid film for ammonia. The fluorescence changes are shown in Fig. 5a by exposing
Fig. 4. Emission spectra (a) and the intensity change of luminescence spectra of the 5D0 → 7F2 transition at 614 nm (b) of ZA-MPTMS-Eu-UiO-67 hybrid under 327 nm exposure to several vapors (blank, ammonia, cyclohexane, methanol, acetone and ether).
5
to various concentrations of ammonia gas, whose results verify that the Eu3+ emission intensity of ZA-MPTMS-Eu-UiO-67 gradually decreases with the successive increasing ammonia concentration. Fig. 5b plots the dependence of Ik/I0 (K = 40, 80, 120, 160, 200 ppm) on the ammonia concentration, whose relative ratios (Ik/I0) are calculated based on the data shown in histograms (b) are shown inFig. 5a. The final result data reveals that Ik/I0 and ammonia concentration have a good linear relationship in the range of 0–200 ppm. The linear relationship is fitted as a function of Eq. (1) with a correlation coefficient (R2) of 0.99308, whose limit of detection (LOD) for ammonia vapors is 8.4238 ppm, calculated as 3σ/k [43] (σ for the standard deviation for ten replicating detections of the blank, and k for the slope of the calibration curve). The result implies that ZA-MPTMS-Eu-UiO-67 is a luminescent sensor for the quantitative analysis of ammonia. Ik =I0 ¼ 1:01413−0:00346Cammonia
ð1Þ
Then we do the concentration test of other organic solvent vapors (cyclohexane, methanol, acetone and ether) in Figs. S11 and S12. The results show that the intensity is barely change of luminescence spectra of the 5D0 → 7F2 transition at 614 nm upon ZA-MPTMS-Eu-UiO-67 exposure to various concentrations (0, 40, 80, 120, 160, 200 ppm) solvent molecule vapors (cyclohexane, methanol, acetone and ether). It is that
Fig. 5. The emission intensity comparison of ZA-MPTMS-Eu-UiO-67 under excitation of 327 nm when exposing to various concentrations of ammonia gas (a); and the relationship between the relative ratios (Ik/I0, K = 40, 80, 120, 160, 200 ppm) and the concentration of ammonia (b).
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J. Ma, B. Yan / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117107
the Eu3+ emission intensity of ZA-MPTMS-Eu-UiO-67 is barely related to the concentration of acetone, cyclohexane, methanol and ether. In order to test the response rate of ZA-MPTMS-Eu-UiO-67 hybrid film as gas sensor, the real-time sensing of NH3 vapors is implemented by the hybrid film (see the time-dependent fluorescence quenching profile in Fig. S13a). The results show that the luminescence intensity of the film is significantly reduced and the luminescence quenching reaches a maximum with a quenching percentage of 73% at 240 s, which is a very fast luminescence response of the sensor to NH3. Repeatability for a sensory material is a very important parameter to assess the sensor's practicability. After detection of NH3, the luminescence intensity of the hybrid film gradually return to its initial value after exposure to ambient air for 10 min due to the volatilization of NH3 (Fig. S13b). 4. Conclusions In summary, the multi-component assembly based with two different microporous units (zeolite A (ZA) and metal-organic framework MOFs) have been achieved to lanthanide hybrid materials. 3Methacryloxypropyltrimethoxysilane (MPTMS) covalently modified ZA and 2,2′ -bipyridine-5,5′-dicarboxyliate (bpydc) linked MOFs (UiO67 and MOF-253) are assembled together with lanthanide ions (Eu3+, Tb3+) through the coordination interaction. These hybrid materials ZA-MPTMS-Eu(Tb)-UiO-67(MOF-253) display the characteristic luminescence of lanthanide ions themselves, suggesting the effective energy transfer from the linker bpydc of MOFs to lanthanide ions. Furthermore, ZA-MPTMS-Eu(Tb)-UiO-67 hybrid system is selected to check its luminescent response to volatile solvent vapor, revealing the luminescence quenching effect on ammonia, while not one volatile organic solvents. These research results provide the strategy to assemble novel kind of multi-component hybrid materials, which is useful to have potential applications in optical material or sensing. Acknowledgment This work was supported by the National Natural Science Foundation of China (21571142), and the Developing Science Funds of Tongji University. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.saa.2019.05.012. References [1] J.M. Stanley, B.J. Holliday, Luminescent lanthanide-containing metallopolymers, Coord. Chem. Rev. 256 (2012) 1520–1530. [2] J.C.G. Bunzli, On the design of highly luminescent lanthanide complexes, Coord. Chem. Rev. 293 (2015) 19–47. [3] B. Yan, Photofunctional Rare Earth Hybrid Materials, Springer, Singapore, 2017. [4] L.D. Carlos, R.A.S. Ferreira, V.D. Bermudez, S.J.L. Ribeiro, Lanthanide-containing lightemitting organic-inorganic hybrids: a bet on the future, Adv. Mater. 21 (2009) 509–534. [5] K. Binnemans, Lanthanide-based luminescent hybrid materials, Chem. Rev. 109 (2009) 4283–4374. [6] B. Yan, Recent progress in photofunctional lanthanide hybrid materials, RSC Adv. 2 (2012) 9304–9324. [7] J. Feng, H.J. Zhang, Hybrid materials based on lanthanide organic complexes: a review, Chem. Soc. Rev. 42 (2013) 387–411. [8] L.M. Zhao, X. Shao, Y.B. Yin, W.Z. Li, Luminescence of novel terbium complex/inorganic/polymeric hybrid materials based on sol–gel technology, Mater. Sci. Eng. B 177 (2012) 257–262. [9] Y. Li, J.L. Wang, W. Chain, X. Wang, J. Zhao, X.Q. Li, Coordination assembly and characterization of europium(III) complexes covalently bonded to SBA-15 directly functionalized by modified polymer, RSC Adv. 3 (2013) 14057–14065. [10] Q.P. Li, B. Yan, Multi-walled carbon nanotube-based ternary rare earth (Eu3+, Tb3+) hybrid materials with organically modified silica-oxygen bridge, J. Colloid Interface Sci. 380 (2012) 67–74. [11] Y.Y. Li, B. Yan, Q.P. Li, Bifunctional heterometallic Ln3+-Gd3+ (Ln = Eu, Tb) hybrid silica microspheres: luminescence and MRI contrast agent property, Dalton Trans. 42 (2013) 1678–1686.
[12] Y.J. Li, B. Yan, Preparation, characterization and luminescence properties of the ternary europium complexes covalently bonded to titania and mesoporous SBA-15, J. Mater. Chem. 21 (2011) 8129–8136. [13] B. Yan, Y.J. Li, Photoactive lanthanide (Eu3+, Tb3+) centered hybrid systems with titania-mesoporous silica/aluminum mesoporous silica based hosts, J. Mater. Chem. 21 (2011) 18454–18461. [14] J. Cuan, B. Yan, Photofunctional hybrid materials with polyoxometalates and benzoate modified mesoporous silica through double functional imidazolium ionic liquid linkage, Microporous Mesoporous Mater. 183 (2014) 9–16. [15] B. Yan, Y.F. Shao, Multifunctional nanocomposites of lanthanide (Eu3+, Tb3+) complex functionalized magnetic mesoporous silica nanospheres covalently bonded with ZnO-polymer, Dalton Trans. 42 (2013) 9565–9573. [16] Y. Mei, Y. Lu, B. Yan, Multi-component hybrid soft gels containing Eu3+ complexes and MS (M = Zn, Cd) nanoparticles assembled with mercapto- ion liquid linkage: adjustable color and white luminescence, New J. Chem. 37 (2013) 2619–2623. [17] Y. Zhao, B. Yan, Rare earth (Eu3+, Tb3+)/β-diketonate functionalized mesoporous SBA-15/GaN nanocomposites: multi-component chemical bonding assembly, characterization and luminescence, J. Colloid Interface Sci. 395 (2013) 145–153. [18] E.M. Flanigen, Zeolites and molecular sieves. An historical perspective, in: H. Van Bekkum, E.M. Flanigen (Eds.), Introduction to Zeolite Science and Practice, 2nd edi, Stud. Surf. Sci. Catal, vol. 137, Jensen JC, Jacobs PA 2001, pp. 11–35. [19] H.R. Li, Y. Wang, P.P. Cao, Y.X. Ding, H.H. Zhang, X.J. Hu, T.T. Wen, Recent progress in host–guest luminescent functional materials based on lanthanide/zeolite L, Sci. China Chem. 42 (2012) 1–18 in Chin. [20] J.N. Hao, B. Yan, Photofunctional host-guest hybrid materials and thin film of lanthanide complexes covalently linked to functionalized zeolite A, Dalton Trans. 43 (2014) 2810–2818. [21] D. Zhao, D.J. Timmons, D.Q. Yuan, H.C. Zhou, Tuning the topology and functionality of metal-organic frameworks by ligand design, Acc. Chem. Res. 44 (2011) 123–133. [22] M. O'Keeffe, O.M. Yaghi, Deconstructing the crystal structures of metal-organic frameworks and related materials into their underlying nets, Chem. Rev. 112 (2012) 675–702. [23] M.D. Allendorf, C.A. Bauer, R.K. Bhakta, R.J.T. Houk, Luminescent metal–organic frameworks, Chem. Soc. Rev. 38 (2009) 1330–1352. [24] Y.J. Cui, Y.F. Yue, G.D. Qian, B.L. Chen, Luminescent functional metal-organic frameworks, Chem. Rev. 112 (2012) 1126–1162. [25] J. Rocha, L.D. Carlos, F.A. Almeida Paz, D. Ananiasa, Luminescent multifunctional lanthanides-based metal-organic frameworks, Chem. Soc. Rev. 40 (2011) 926–940. [26] W.P. Lustig, S. Mukherjee, N.D. Rudd, A.V. Desai, J. Li, S.K. Ghosh, Metal-organic frameworks: functional luminescent and photonic materials for sensing applications, Chem. Soc. Rev. 46 (2017) 2132–3285. [27] B. Yan, Lanthanie functionalized metal-organic frameworks hybrid systems to create multiple luminescent centers for chemical sensing, Acc. Chem. Res. 50 (2017) 2789–2798. [28] L. Chen, B. Yan, Multi-component assembly and luminescence tuning of lanthanide hybrids based with both zeolite L/A and SBA-15 through two organically grafted linkers, Dalton Trans. 43 (2014) 14123–14131. [29] X. Lian, B. Yan, Multi-component luminescent lanthanide hybrids of both functionalized IR-MOF-3 and SBA-15, New J. Chem. 39 (2015) 5898–5901. [30] X.Y. Xu, B. Yan, Novel photofunctional hybrid materials (alumina and titania) functionalized with both MOF and lanthanide complexes through coordination bonds, RSC Adv. 4 (2014) 38761–38768. [31] J. Ma, B. Yan, Multi-component hybrid soft ionogels for photoluminescence tuning and sensing organic solvent vapors, J. Colloid Interface Sci. 513 (2018) 133–140. [32] J. Ma, B. Yan, Novel hybrid materials of lanthanide coordination polymers ion exchanged Mg-Al layered double hydroxide: multi-color photoluminescence and white color thin film, Dyes Pigments 153 (2018) 266–274. [33] J. Ma, B. Yan, Multi-component hybrid films based on covalent post-synthetic functionalization of silicon chip using both ZIF-90 and lanthanide complexes for luminescence tuning, New J. Chem. 42 (2018) 15061–15067. [34] P. Laine, R. Seifert, R. Giovanoli, G. Calzaferri, A convenient preparation of closepacked monograin layers of pure zeolite A microcrystals, New J. Chem. 21 (1997) 453–460. [35] L.J. Li, S.F. Tang, C. Wang, X.X. Lv, M. Jiang, H.Z. Wu, X.B. Zhao, High gas storage capacities and stepwise adsorption in a UiO type metal–organic framework incorporating Lewis basic bipyridyl sites, Chem. Commun. 50 (2014) 2304–2307. [36] E.D. Bloch, D. Britt, C. Lee, C.J. Doonan, F.J. Uribe-Romo, H. Furukawa, J.R. Long, O.M. Yaghi, Metal insertion in a microporous metal-organic framework lined with 2,2′bipyridine, J. Am. Chem. Soc. 132 (2010) 14382–14384. [37] Y. Lu, B. Yan, A novel luminescent monolayer thin film based on postsynthetic method and functional linker, J. Mater. Chem. C 2 (2014) 5526–5532. [38] Y. Zhou, B. Yan, Ratiometric detection of temperature using responsive dualemissive MOF hybrids, J. Mater. Chem. C 3 (2015) 9353–9358. [39] J.N. Hao, B. Yan, Hybrid polymer thin films with a lanthanide–zeolite a host–guest system: coordination bonding assembly and photo-integration, New J. Chem. 38 (2014) 3540–3547. [40] Q.M. Wang, B. Yan, From molecules to materials: a new way to construct luminescent chemical bonded hybrid systems based with ternary lanthanide complexes of 1,10-phenanthroline, Inorg. Chem. Commun. 7 (2004) 1124–1127. [41] W.T. Carnall, P.R. Fields, K. Rajnak, Electronic energy levels of the trivalent lanthanide aquo ions. IV. Eu3+, J. Chem. Phys. 49 (1968) 4450–4455. [42] W.T. Carnall, P.R. Fields, K. Rajnak, Electronic energy levels of the trivalent lanthanide aquo ions. III. Tb3+, J. Chem. Phys. 49 (1968) 4447–4449. [43] A. M. Committee, Recommendations for the definition, estimation and use of the detection limit, Analyst 112 (1987) 199–204.