Terbium (III) loaded zinc-based metal organic framework and preparation and application thereof

文档序号:2729 发布日期:2021-09-17 浏览:37次 中文

1. A terbium (III) -loaded zinc-based metal organic framework which is characterized in that the general formula is Tb3+@ Zn-MOF; wherein Zn-MOF represents a chemical formula of [ (CH)3)2NH2][Zn2(DMTDC)2(3-mtz)]·4DMF·3H2A zinc-based metal organic framework of O; wherein, DMTDC2-Represents 3, 4-dimethylthieno [2,3-b ]]Anion of thiophene-2, 5-dicarboxylic acid after deprotonation of two protons, 3-mtz-Represents an anion of 3-methyl-3H-1, 2, 4-triazole after deprotonation, and DMF represents N, N-dimethylformamide; organic ligand DMTDC2-And 3-mtz-Zn is added2+Connecting into a three-dimensional anion framework structure containing one-dimensional pore channels, wherein the pore rate of the three-dimensional anion framework structure is 61.0 percent, and the pore channels are balanced by charge [ (CH)3)2NH2]+The uncoordinated solvent molecule N, N-dimethylformamide and water.

2. The terbium (iii) -loaded zinc-based metal-organic framework according to claim 1, characterized in that it belongs to the monoclinic system, space group is C2/C, and unit cell parameters are respectively: α=γ=90°、β=90.205(2)°、

3. a method for preparing a terbium (iii) -supported zinc-based metal-organic framework as defined in claim 1 or 2, comprising the steps of:

s1, adding 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid, 3-methyl-3H-1, 2, 4-triazole and zinc nitrate hexahydrate into a pure N, N-dimethylformamide solvent, and uniformly mixing to obtain a mixed solution;

s2, sealing the mixed liquid obtained in the step S1, carrying out solvent thermal reaction at 90-120 ℃, reacting for 12-48 hours, and cooling to room temperature at the speed of 5 ℃ per hour to obtain colorless needle-like transparent crystals;

s3, washing the colorless needle-shaped transparent crystal obtained in the step S2 with N, N-dimethylformamide, and naturally airing to obtain a zinc-based metal organic framework Zn-MOF;

s4, adding the Zn-MOF obtained in the step S3 into 0.25mol/L Tb (NO)3)3·6H2Soaking in an ethanol solution of O for 72 hours, filtering, washing with ethanol for multiple times, and drying to obtain the terbium (III) -loaded zinc-based metal organic framework Tb3+@Zn-MOF。

4. The terbium (III) -loaded zinc-based metal-organic framework according to claim 3, wherein, in step S1, the molar ratio of 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid, 3-methyl-3H-1, 2, 4-triazole and zinc nitrate hexahydrate is 1:0.5: 1.

5. The terbium (iii) -supported zinc-based metal-organic framework according to claim 3, wherein in step S1, the ratio of the amount of 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid to the pure solvent of N, N-dimethylformamide is 0.1 mmol: 4 ml.

6. The terbium (III) -supported zinc-based metal-organic framework according to claim 3, wherein in step S4, Zn-MOF and Tb (NO)3)3·6H2The dosage ratio of the ethanol solution of O is 50 mg: 4 ml.

7. Use of a zinc-based metal-organic framework loaded with terbium (iii) according to any one of claims 1 to 2 or a zinc-based metal-organic framework loaded with terbium (iii) prepared according to any one of claims 3 to 6, as a fluorescent probe for rapid-response recognition of iron ions.

8. Use of the terbium (III) -loaded zinc-based metal-organic framework according to claim 7, characterized in that Fe is selectively rapidly fluorescence recognized by the naked eye under an ultraviolet lamp3+Ions.

Background

Iron is one of the essential trace elements for human body, and plays an important role in the life process. For example, it is an indispensable part of hemoglobin and is involved in the transport and storage of oxygen. Thus, deficiency and excess of iron elements can lead to various serious biological diseases, such as anemia, cirrhosis, endotoxemia, and hereditary hemochromatosis. From this viewpoint, it is necessary to develop a sensor for detecting iron quickly and accurately.

Compared with the traditional detection methods such as atomic absorption spectrometry, voltammetry, X-ray dispersion method and ion mobility spectrometry, the fluorescence sensing based on Luminescent Metal-Organic Frameworks (LMOF) has the advantages of high sensitivity, short response time, simplicity, convenience, low cost and the like. Luminescent metal organic frameworks have therefore been widely used for monitoring ions, biomolecules, gas molecules and nitro explosives (US20210002304a 1; US010830722B 2; EP3599239a 1; coord chem.rev.2018,354, 28-45; coord.chem.rev.2020,415,213299). Among the various luminescent metal-organic frameworks reported so far, lanthanide metal-organic frameworks (Ln-MOFs), especially Eu-MOF and Tb-MOF, have sharp and characteristic emission, large Stokes shift, relatively long luminescence lifetime, and macroscopic fluorescence color, and are considered to be an effective recognition of Fe3+The fluorescent probe of (1). For example, patent document CN111777630A discloses rare earth terbium (III) complex and its preparation method and applicationThe rare earth terbium (III) framework compound can be used as a fluorescent probe for identifying Fe3+(ii) a Bai et al, a highly sensitive detection of Fe using lanthanide metal ions to construct three white emitting lanthanide metal organic frameworks3+Ions (crystal. growth des.2018,18,5353); zhu et al synthesized a rare multifunctional Ln-MOF capable of detecting Fe simultaneously3+Ions, aspartic acid and dimethyl sulfoxide (Dalton Trans.2020,49,7514).

At present, most of metal organic frameworks containing rare earth ions are directly synthesized by adopting rare earth ions and organic ligands, and lanthanide is utilized to modify the metal organic frameworks and is used for identifying Fe by fluorescence3+For example, patent document CN108546551A, "a fluorescent probe for identifying iron ions in water and a preparation method and application thereof" provides a metal organic framework Cd-MOF, and rare earth Eu is subjected to post-modification and in-situ reduction3+Ions are introduced into the frame pore canal, the fluorescence characteristic of the frame is enhanced, and Eu is formed2+And the doped fluorescent probe is used for detecting ferric ions in the water body. Therefore, the fluorescent probe or the optical sensor for developing and synthesizing the novel lanthanide ion-supported framework compound has application prospect in iron ion recognition.

Disclosure of Invention

In view of the above, the invention aims to provide a terbium (III) -loaded zinc-based metal-organic framework, and a preparation method and an application thereof, wherein the terbium (III) -loaded zinc-based metal-organic framework can emit stronger green fluorescence and can emit stronger green fluorescence in Fe3+The sensor has the characteristic of fluorescence quenching under the action, can be distinguished by naked eyes under an ultraviolet lamp, and can be used as a fluorescence sensor for rapidly responding and identifying iron ions.

In order to solve the technical problems, the invention adopts the following technical scheme:

in a first aspect, a terbium (III) -loaded zinc-based metal-organic framework of the general formula Tb3+@ Zn-MOF; wherein Zn-MOF represents a chemical formula of [ (CH)3)2NH2][Zn2(DMTDC)2(3-mtz)]·4DMF·3H2A zinc-based metal organic framework of O; wherein, DMTDC2-Represents3, 4-dimethylthieno [2,3-b ]]Anion of thiophene-2, 5-dicarboxylic acid after deprotonation of two protons, 3-mtz-Represents an anion of 3-methyl-3H-1, 2, 4-triazole after deprotonation, and DMF represents N, N-dimethylformamide; organic ligand DMTDC2-And 3-mtz-Zn is added2+The three-dimensional anion framework structure is connected to form a three-dimensional anion framework structure containing one-dimensional pore channels, the pore rate of the three-dimensional anion framework structure is 61.0 percent, and the pore channels are balanced with charges [ (CH)3)2NH2]+The uncoordinated solvent molecule N, N-dimethylformamide and water.

The zinc-based metal organic framework belongs to a monoclinic system, a space group is C2/C, and unit cell parameters are respectively as follows: α=γ=90°、β=90.205(2)°、

in a second aspect, a method of making a terbium (iii) supported zinc-based metal-organic framework, as described above, includes the steps of:

s1, adding 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid, 3-methyl-3H-1, 2, 4-triazole and zinc nitrate hexahydrate into a pure N, N-dimethylformamide solvent, and uniformly mixing to obtain a mixed solution;

s2, sealing the mixed liquid obtained in the step S1, carrying out solvent thermal reaction at 90-120 ℃, wherein the reaction time is 12-48 hours, and cooling to room temperature at a speed of about 5 ℃ per hour to obtain colorless needle-shaped transparent crystals;

s3, washing the colorless needle-shaped transparent crystal obtained in the step S2 with N, N-dimethylformamide, and naturally airing to obtain a zinc-based metal organic framework Zn-MOF;

s4, adding the Zn-MOF obtained in the step S3 into 0.25mol/L Tb (NO)3)3·6H2Soaking in ethanol solution of O for 72 hours, filtering, washing with ethanol for multiple times, and drying to obtain the terbium (III) -loaded zinc-based goldBelongs to an organic framework Tb3+@Zn-MOF。

Preferably, in step S1, the molar ratio of 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid, 3-methyl-3H-1, 2, 4-triazole and zinc nitrate hexahydrate is 1:0.5: 1.

Preferably, in step S1, the ratio of the amount of 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid to the pure solvent of N, N-dimethylformamide is 0.1 mmol: 4 ml.

Preferably, in step S4, Zn-MOF and Tb (NO)3)3·6H2The dosage ratio of the ethanol solution of O is 50 mg: 4 ml.

Preferably, the steps S1 to S4 are:

s1, adding 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid, 3-methyl-3H-1, 2, 4-triazole and zinc nitrate hexahydrate into an N, N-dimethylformamide solvent according to a molar ratio of 1:0.5:1, wherein the dosage ratio of the 3, 4-dimethylthieno [2,3-b ] thiophene-2, 5-dicarboxylic acid to the N, N-dimethylformamide solvent is 0.1 millimole: 4 ml, and uniformly mixing to obtain a mixed solution;

s2, sealing the mixed liquid obtained in the step S1, carrying out solvent thermal reaction at 90-120 ℃, wherein the reaction time is 12-48 hours, and cooling to room temperature at a speed of about 5 ℃ per hour to obtain colorless needle-shaped transparent crystals;

s3, washing the colorless needle-shaped transparent crystal obtained in the step S2 with N, N-dimethylformamide, and naturally airing to obtain a zinc-based metal organic framework Zn-MOF;

s4, adding 50 mg of Zn-MOF obtained in the step S3 into 4 ml of 0.25mol/L Tb (NO)3)3·6H2Soaking in ethanol solution of O for 72 hours, filtering, washing with ethanol for multiple times, and drying to obtain the zinc-based metal organic framework Tb loaded with terbium (III)3+@Zn-MOF。

In a third aspect, the use of a terbium (iii) loaded zinc-based metal-organic framework as described above: fluorescent probes for the rapid responsive identification of iron ions, particularly Fe, by the selective rapid fluorescence of the naked eye under uv lamps3+Ions.

The invention provides a novel structure, stability, good selectivity, high sensitivity and quick monitoringRapid fluorescence sensing material-terbium (III) loaded zinc-based metal organic framework Tb3+@ Zn-MOF. The material is to Fe3+Tb with ions having selective recognition capability and loaded on zinc-based metal organic framework Zn-MOF3+Can react with Fe3+Partial ion exchange takes place, thereby converting Fe3+Loaded on Zn-MOF, and further generates obvious fluorescence quenching, the phenomenon is visible under an ultraviolet lamp, and the rapid response identification can be realized in less than 15 seconds, so that the fluorescent probe can be used as a rapid response iron ion identification fluorescent probe which identifies Fe3+K ofsvThe value reaches 3.26 multiplied by 104M-1Compared with the existing Fe3+Fluorescent identification materials have made great progress. In addition, the preparation method provided by the invention is simple and feasible, the preparation period is short, the recovery is easy, the purity of the product crystal is high, and the crystal yield can reach more than 60%.

Compared with the prior art, the invention has the following beneficial effects: the terbium (III) -loaded zinc-based metal organic framework material is a stable fluorescent sensing material, the preparation method provided by the invention is simple and feasible, the preparation period is short, the recovery is easy, the crystal yield can reach more than 60 percent, and the method is used for preparing Fe3+The ions have selective recognition ability, which recognizes Fe3+K ofsvThe value reaches 3.26 multiplied by 104M-1Compared with the existing Fe3+Fluorescent identification materials have made great progress. The experimental Zn-MOF powder diffraction pattern is basically consistent with the theoretical simulation, and proves that the Zn-MOF powder diffraction pattern has higher phase purity and Tb3+The powder diffraction pattern of the @ Zn-MOF and the powder diffraction pattern of the Zn-MOF have no obvious change, which indicates that the crystal structure of the terbium (III) loaded crystal has no great change, is basically maintained, can be used as a fluorescent sensor for rapidly responding and identifying iron ions, and has good application prospect in the field of iron ion detection.

Drawings

FIG. 1 is a diagram showing the coordination structure of zinc ions in a zinc-based metal organic framework.

FIG. 2 is a three-dimensional block diagram of a zinc-based metal organic framework.

FIG. 3 shows a sample of a pure single crystal with a zinc-based metal-organic framework, a single crystal simulation, terbium (III) -loaded zinc-based goldBelongs to an organic framework, and Fe (NO) is added into a zinc-based metal organic framework loaded by terbium (III)3)3Diffraction contrast of the powder after.

FIG. 4 is an EDS energy spectrum of a terbium (III) -supported zinc-based metal-organic framework.

FIG. 5 shows a zinc-based metal organic framework, a terbium (III) -loaded zinc-based metal organic framework, and Fe (NO) added in the terbium (III) -loaded zinc-based metal organic framework3)3XPS spectra thereafter.

FIG. 6 is the addition of Fe (NO) to a terbium (III) -supported zinc-based metal-organic framework3)3The EDS energy spectrum after the reaction.

FIG. 7 is a thermogravimetric plot of a zinc-based metal organic framework.

FIG. 8 is a solid state excitation and emission spectra of a zinc-based metal organic framework and a terbium (III) -loaded zinc-based metal organic framework (inset is a photograph under an ultraviolet lamp).

FIG. 9 is an excitation and emission spectra of a zinc-based metal-organic framework (3mg) dispersed in ethanol (5mL) solvent with terbium (III) loaded zinc-based metal-organic framework (3mg) (inset is a photograph under a UV lamp).

FIG. 10 is a fluorescence emission spectrum (excitation wavelength 328nm) of terbium (III) -loaded zinc-based metal-organic framework (3mg) dispersed in ethanol (5mL) with the addition of 100. mu.L of each metal cation (10 mM).

FIG. 11 is a graph of the fluorescence emission intensity of terbium (III) -loaded zinc-based metal-organic frameworks (3mg) dispersed in ethanol (5mL) after the addition of 100. mu.L of various metal cations (10mM) (excitation light wavelength of 328 nm).

FIG. 12 is a photograph under an ultraviolet lamp of terbium (III) -supported zinc-based metal-organic framework (3mg) dispersed in ethanol (5mL) after addition of 100. mu.L of each metal cation (10 mM).

FIG. 13 shows ultrasound dispersion of terbium (III) -loaded zinc-based metal-organic framework (3mg) in ethanol (5mL), and dropwise addition of Fe (NO) at different concentrations to 3mL of suspension3)3(6×10-3M) fluorescence emission spectrum under ethanol solution (excitation light wavelength is 328 nm).

FIG. 14 is a terbium (III) loaded zinc-based metal-organic frameFluorescence intensity ratio of the shelves I0I to Fe3+Concentration curves and Stern-Volmer plots.

FIG. 15 is a terbium (III) loaded zinc-based metal-organic framework pair Fe3+Time response curve (inset: time ≦ 2 minutes).

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention is further described in detail with reference to the following specific embodiments.

Preparation of terbium (III) -loaded zinc-based metal organic framework material

Example 1

25.6 mg (0.1 mmol) of 3, 4-dimethylthieno [2,3-b ] are introduced]Thiophene-2, 5-dicarboxylic acid, 4.2 mg (0.05 mmol) of 3-methyl-3H-1, 2, 4-triazole and 30 mg (0.1 mmol) of Zn (NO)3)2·6H2Adding O into 4 ml of N, N-Dimethylformamide (DMF) pure solvent and uniformly mixing; sealing the obtained mixed liquid, carrying out solvothermal reaction at 90 ℃, cooling to room temperature at the speed of 5 ℃ per hour after 12 hours of reaction to obtain colorless acicular transparent crystals, washing with N, N-dimethylformamide, naturally airing to obtain the zinc-based metal organic framework material Zn-MOF, adding 50 mg of the Zn-MOF material into 4 ml of 0.25mol/L Tb (NO)3)3·6H2Soaking in ethanol solution of O for 72 hours, filtering, washing with ethanol for multiple times, and drying in the air to obtain the zinc-based metal organic framework material Tb loaded with terbium (III)3+@Zn-MOF。

Example 2

51.2 mg (0.2 mmol) of 3, 4-dimethylthieno [2,3-b ] are introduced]Thiophene-2, 5-dicarboxylic acid, 8.4 mg (0.1 mmol) of 3-methyl-3H-1, 2, 4-triazole and 60 mg (0.2 mmol) of Zn (NO)3)2·6H2Adding O into 8 ml of N, N-Dimethylformamide (DMF) pure solvent and uniformly mixing; sealing the obtained mixed liquid, carrying out solvent thermal reaction at 120 ℃, cooling to room temperature at the speed of 5 ℃ per hour after 48 hours of reaction to obtain colorless needle-like transparent crystals, washing with N, N-dimethylformamide, and naturally airing to obtain the zinc-based metal organic framework materialZn-MOF, 50 mg of Zn-MOF material was added to 4 ml of 0.25mol/L Tb (NO)3)3·6H2Soaking in ethanol solution of O for 72 hours, filtering, washing with ethanol for multiple times, and drying in the air to obtain the zinc-based metal organic framework material Tb loaded with terbium (III)3+@Zn-MOF。

Determination of structures of zinc-based metal-organic frameworks (II) and terbium (III) -loaded metal-organic frameworks (III)

Both examples allow to obtain single crystals of Zn-MOF. Selecting Zn-MOF single crystal with proper size under microscope, performing Cu-Kalpha ray monochromatization by graphite monochromator on Bruker Apex CCD diffractometer at temperature T ═ 100K To be provided withThe diffraction data is collected. The absorbance correction was performed by the SADABS program and refined using the full matrix least squares technique with SHELXTL package. The anisotropic thermal parameters were applied to all non-hydrogen atoms. The volume fraction of large numbers of disordered cations or solvents in the lattice pores cannot be modeled on atomic sites, but is processed using the SQUEEZE program in the PLATON software package. Some of the parameters for crystallographic diffraction point data collection and structure refinement are shown in table 1 below.

Table 1: parameter table of zinc-based metal organic framework crystal

Fig. 1 to 2 are structural diagrams of the zinc-based metal organic framework, in which fig. 1 shows a structural diagram of a coordination of a metal zinc ion, and fig. 2 is a three-dimensional structural diagram of the zinc-based metal organic framework.

Powder diffraction characterization phase purity: collecting powder diffraction data on a MiniFlex600 automatic diffractometer, wherein the operating voltage of the instrument is 40KV, the current is 15mA, and graphite monochromatized copper target X-rays are used; the continuous scan is completed in the range of 5 deg. to 50 deg., and the scan speed is 5 deg./min. Single crystal structure powder diffraction spectrum simulated transformation Mercury 1.4.2 was used.

FIG. 3 shows a sample of a zinc-based metal organic framework Zn-MOF single crystal, a single crystal simulation, terbium (III) -loaded zinc-based metal organic framework Tb3+@ Zn-MOF, addition of Fe to a terbium (III) -loaded zinc-based metal-organic framework3+Diffraction contrast of the powder after. The figure shows that: the experimental Zn-MOF powder diffraction pattern is basically consistent with the theoretical simulation, and the phase purity is proved to be higher. Terbium (III) loaded zinc-based metal organic framework Tb3+Adding Fe into a zinc-based metal organic framework loaded with @ Zn-MOF and terbium (III)3 +The powder diffraction pattern of the rear part is compared with that of the zinc-based metal organic framework Zn-MOF, the main peak positions are basically maintained, and the terbium (III) loaded zinc-based metal organic framework and the addition of Fe in the framework are illustrated3+The latter structure substantially maintains the three-dimensional structure of the metal-organic framework Zn-MOF.

Fig. 4 shows the EDS spectrum of a terbium (iii) -supported zinc-based metal-organic framework. EDS spectrum shows that soaking Zn-MOF in terbium nitrate ethanol solution can successfully load terbium (III) ions on a zinc-based metal organic framework through ion exchange to form Tb3+@Zn-MOF。

FIG. 5 shows a sample of a Zn-MOF single crystal, a terbium (III) -supported zinc-based metal-organic framework Tb3+@ Zn-MOF and addition of Fe to terbium (III) -loaded zinc-based metal-organic framework3+The XPS spectrum after the test. XPS spectrum shows that soaking Zn-MOF in terbium nitrate ethanol solution can successfully load terbium (III) ions on a zinc-based metal organic framework through ion exchange to form Tb3+@ Zn-MOF, addition of Fe to a terbium (III) -loaded zinc-based metal-organic framework3+After that, there is a part Tb3+With Fe3+Ion exchange takes place to convert Fe3+Loaded on Zn-MOFThe above.

FIG. 6 shows a terbium (III) -loaded zinc-based metal-organic framework incorporating Fe3+The EDS spectrum after the reaction. The spectrum shows that Fe is added into a sample of a zinc-based metal organic framework loaded by terbium (III)3+By Fe3+And Tb3+Partial ion exchange takes place and Fe is again reacted3+Supported on Zn-MOF.

Thermal stability of zinc (tri) based metal organic frameworks

The thermal stability of the zinc-based metal organic framework is detected by a thermogravimetric analysis method. Thermogravimetric curves were obtained using a TA SDT-650C synchronous thermal analyzer in the united states under nitrogen. The thermogravimetric curve is shown in fig. 7, and it can be seen from fig. 7 that the prepared zinc-based metal organic framework can be stabilized to 300 ℃, and the sample molecule of the zinc-based metal organic framework crystal can be calculated to contain 4N, N-Dimethylformamide (DMF) and 3 water molecules according to the weight loss.

Fluorescence properties of (tetra) terbium (III) -loaded zinc-based metal-organic frameworks

The fluorescence spectrum experiment was carried out using an F-4600 fluorescence spectrophotometer manufactured by Hitachi, Inc.

FIG. 8 shows solid state excitation and emission spectra of zinc-based metal organic frameworks Zn-MOF and terbium (III) loaded zinc-based metal organic frameworks. The graph shows that the fluorescence of Zn-MOF is very weak, but the zinc-based metal organic framework loaded with terbium (III) emits stronger green fluorescence, and the zinc-based metal organic framework loaded with terbium (III) emits the green fluorescence which is obviously observed by naked eyes under an ultraviolet lamp.

Fig. 9 shows excitation and emission spectra of a zinc-based metal organic framework (3mg) ultrasonically dispersed in ethanol (5mL) solvent with a terbium (iii) loaded zinc-based metal organic framework (3 mg). The graph shows that the Zn-MOF dispersed in ethanol has weak fluorescence, but the zinc-based metal organic framework loaded with terbium (III) emits stronger green fluorescence, and the zinc-based metal organic framework loaded with terbium (III) can obviously emit green fluorescence under an ultraviolet lamp.

(V) research on selective recognition of iron ions

3mg of Tb3+@ Zn-MOF was dispersed in 5ml ethanol solution and sonicated for 30 min to removeTo form a suspension, and then 100. mu.L of nitrate M (NO) was added3)x(10mM;M=Na+,Mg2+,Ca2+,Pb2+,Zn2+,Cd2+,Ag+,Mn2+,Co2+,Ni2+,Cu2+,Al3+,Cr3+,Fe3+) The above-mentioned 3ml suspensions were added with the ethanol solutions, and the luminescence spectra (FIG. 10) and the peak intensity contrast of the maximum emission (FIG. 11) after addition of each metal ion were measured by a fluorescence spectrophotometer. After adding other metal ions, the luminous intensity of the compound is basically kept unchanged, and Cr is added3+Rear Tb of ion3+The fluorescence intensity of @ Zn-MOF is reduced to a certain extent, and Fe is added3+After ionization, Tb3+The fluorescence intensity of @ Zn-MOF shows a pronounced quenching phenomenon. At the same time, a photograph was taken of the suspension under UV light after addition of ions (FIG. 12), and Tb was also evident3+@ Zn-MOF addition of Fe3+Significant quenching of the post-fluorescence occurred, indicating Tb3+@ Zn-MOF for Fe3+The ions have selective recognition capabilities.

For a better understanding of Tb3+@ Zn-MOF for Fe3+And (3) carrying out a fluorescence titration experiment in the ion identification process. To Tb3 +In a suspension of @ Zn-MOF (3mL) Fe was gradually added dropwise3+(6×10-3M), the fluorescence spectrum of the process is measured and recorded. As shown in fig. 13, with Fe3+Increase in ion concentration, Tb3+The luminescence intensity of @ Zn-MOF gradually decreased. When Fe3+Tb when the ion addition amount is 190. mu.M3+The fluorescence of @ Zn-MOF was essentially completely quenched (quenching efficiency 96.7%). Meanwhile, the fluorescence titration process can use Stern-Volmer equation (I)0/I=1+Ksv[Fe3+]) To make a reasonable explanation for the quenching effect, wherein I0And I is each Fe3+Tb in presence and absence3+Fluorescence intensity of @ Zn-MOF suspension, KsvIs the quenching constant. It can be seen from FIG. 14 that in the low concentration range, Fe3+Concentration of ions and Tb3+The @ Zn-MOF has a good linear relationship with respect to fluorescence intensity, and K thereofsvThe value is calculated as 3.26104M-1This value is larger than that of other reported iron ion recognition sensors based on a framework compound, for example, patent document "a rare earth-based metal organic framework compound having a lamellar structure, a method for producing the same, and use thereof" in patent publication No. CN109021247A3+K ofsvThe value is 1.905X 104M-1(ii) a The patent document CN111253582A entitled "a zirconium-based metal organic framework material, a preparation method and applications thereof" proposes the identification of Fe by a zirconium-based metal organic framework3+K ofsvThe value was 6.05X 103M-1(ii) a The patent document CN111187423A entitled "novel stabilized zirconium-based metal organic framework material, preparation method and application" proposes the identification of Fe by zirconium-based metal organic framework3+K ofsvThe value is 1.4X 104M-1. This indicates Tb3+@ Zn-MOF for Fe3+Has good identification effect.

FIG. 15 is Tb3+@ Zn-MOF for Fe3+Can be seen, this Tb3+@ Zn-MOF for Fe3+Can respond quickly to identification in less than 15 seconds, indicating Tb3+@ Zn-MOF for Fe3+Has the characteristics of high sensitivity and rapid sensing.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

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