CN114349971A

CN114349971A - Metal organic framework material and preparation method and application thereof

Info

Publication number: CN114349971A
Application number: CN202111580090.2A
Authority: CN
Inventors: 王恋; 石静; 杨晓占; 洪文健; 贺肖; 阮心; 陈星宇
Original assignee: Guangzhou Special Pressure Equipment Inspection and Research Institute
Current assignee: Guangzhou Special Pressure Equipment Inspection and Research Institute
Priority date: 2021-12-22
Filing date: 2021-12-22
Publication date: 2022-04-15
Anticipated expiration: 2041-12-22
Also published as: CN114349971B

Abstract

The invention discloses a metal organic framework material and a preparation method and application thereof. The metal organic framework material has Tb as the central metal ion³⁺The organic ligand is terephthalic acid and thiophene-2, 5-dicarboxylic acid. The metal organic framework material can rapidly and specifically detect Bi in aqueous solution³⁺And has the advantages of quick response time, high selectivity, high sensitivity and low detection limit, and can be used as a very potential for quickly detecting the metal Bi in water³⁺The fluorescence sensor of (1).

Description

Metal organic framework material and preparation method and application thereof

Technical Field

The invention relates to the field of materials and analysis and detection, in particular to a metal organic framework material and a preparation method and application thereof.

Background

In recent years, metal organic framework Materials (MOFs) have been developed, and the MOFs are porous materials bridged by metal ions and organic ligands, and have the characteristics of adjustable structure, simplicity and convenience in synthesis, good stability, large specific surface area and the like. The diverse structural possibilities of MOFs make them have great application prospects in many fields such as chemical sensing, catalysis, gas storage and separation, and drug loading. In these applications, fluorescence sensing technology has received a great deal of attention. This is because the detection of analytes by fluorescence has some unique advantages such as high selectivity, high sensitivity, rapid response, non-destructive, easy handling and simple sample preparation.

Bismuth compounds are widely used in pharmaceutical preparations such as antibacterial agents and anti-HIV and radiotherapeutic agents. Bismuth is also used in cosmetics, metallurgy and alloys, the semiconductor industry, and in recycling uranium nuclear fuels and contact lens cleaning solutions, among others. With the use of bismuth and its compounds, bismuth may leak into the environment. However, bismuth compounds have toxicity to human body, and may have effects on human body including nephropathy, osteoarthropathy, hepatitis, neuropathy, etc. when ingested in too high a content. Therefore, the rapid detection of bismuth ions in water has great significance for guaranteeing the safety of human bodies. Various methods for bismuth detection include liquid-liquid extraction procedures, hydride generation Inductively Coupled Plasma (ICP), electrothermal evaporation ICP mass spectrometry, atomic absorption spectroscopy, potentiometric stripping analysis, anodic stripping voltammetry, and cathodic stripping voltammetry. However, most of these methods suffer from the problems of equipment unavailability, high cost, time consumption, and uncontrollable reaction conditions. Thus, fluorescence sensing methods are used to monitor Bi in aqueous solutions³⁺Is a convenient and feasible means. But is currently about Bi³⁺Fluorescent probes are rarely reported, so that the high-selectivity and high-sensitivity fluorescent probe for detecting Bi is designed³⁺The fluorescent probe of (2) is not very slow.

Disclosure of Invention

Based on the above, the invention provides a metal organic framework material, which can rapidly and specifically detect Bi in an aqueous solution³⁺And response time is fast, selectHigh in sensitivity and low in detection limit, and can be used as a very potential for rapidly detecting metal Bi in water³⁺The fluorescence sensor of (1).

The specific technical scheme is as follows:

a metal organic frame material has Tb as central metal ion³⁺The organic ligand is terephthalic acid and thiophene-2, 5-dicarboxylic acid.

In some of these examples, the metal-organic framework material was prepared from terbium nitrate hexahydrate, terephthalic acid, and thiophene-2, 5-dicarboxylic acid.

In some of these embodiments, the molar ratio of the reaction feeds of terbium nitrate hexahydrate, terephthalic acid, and thiophene-2, 5-dicarboxylic acid is 1: 0.8-1.2: 0.8-1.2.

In some of these embodiments, Tb in the crystal structure of the metal organic framework material³⁺Coordinates with the surrounding eight oxygen atoms in an 8-coordinate mode, where four oxygen atoms are from two terephthalic acids and four oxygen atoms are from four thiophene-2, 5-dicarboxylic acids.

In some of these embodiments, the terbium-metal organic framework material has a crystal structure of an orthorhombic system, a space group of Fmmm, and lattice parameters as follows:

the Z value was 8.

In some of these embodiments, the four oxygen atoms from the two terephthalic acids are chelated with Tb using symmetric chelation³⁺Coordination having a Tb-O bond length of

Four oxygen atoms from four thiophene-2, 5-dicarboxylic acids bridged with Tb³⁺Coordination having a Tb-O bond length of

In some embodiments, the bond angles in the crystal structure of the metal-organic framework material are as follows:

wherein O004 is an oxygen atom derived from terephthalic acid; o005 is oxygen atom derived from thiophene-2, 5-dicarboxylic acid, Tb01 is central metal ion Tb³⁺。

In some of these examples, the metal-organic framework material has diffraction peaks at 2 θ of 9.5500 °, 10.1616 °, 19.6972 ° as determined using an X-ray powder diffraction method of Cu — K α.

In some of these embodiments, the relative intensities of the diffraction peaks are as follows:

2θ(°)	relative strength
		9.5500	100％
10.1616	75.59％
		19.6972	60.56％。

The invention also provides a preparation method of the metal organic framework material. The preparation method can prepare the metal organic framework material by a very simple process.

The specific technical scheme is as follows:

the preparation method of the metal organic framework material comprises the following steps:

(1) dissolving terbium nitrate hexahydrate, terephthalic acid and thiophene-2, 5-dicarboxylic acid in an organic solvent respectively to obtain a terbium nitrate hexahydrate solution, a terephthalic acid solution and a thiophene-2, 5-dicarboxylic acid solution respectively;

(2) and mixing the terbium nitrate hexahydrate solution, the terephthalic acid solution and the thiophene-2, 5-dicarboxylic acid solution, and removing the organic solvent after reaction to obtain the metal organic framework material.

In some of these embodiments, the organic solvent is N, N-dimethylformamide.

In some of these embodiments, the concentration of the terbium nitrate hexahydrate solution, the terephthalic acid solution, and the thiophene-2, 5-dicarboxylic acid solution are each 0.8mmol/mL to 1.2 mmol/mL.

In some of these embodiments, the removing the organic solvent comprises the steps of: and cooling the obtained reaction solution to room temperature, removing supernatant, transferring the solid phase into a centrifuge tube, centrifugally washing by using an organic solvent, and drying the solid phase product for 8-12h at the temperature of 60-80 ℃ after washing.

In some of these embodiments, the reaction in step (2) is at a temperature of 145 ℃ to 155 ℃ for a time of 44 hours to 52 hours.

The invention also provides application of the metal organic framework material.

The specific technical scheme is as follows:

the metal organic framework material is used as a fluorescent probe for detecting Bi³⁺Application in metal ions.

The metal organic framework material is used as a fluorescent probe for detecting Bi in aqueous solution³⁺Application in metal ions.

The invention also provides Bi in the aqueous solution³⁺The method for the detection of (1) is,the detection method can rapidly and specifically detect Bi in the aqueous solution³⁺And the response time is fast, the selectivity is high, the sensitivity is high, and the detection limit is low.

The specific technical scheme is as follows:

bi in aqueous solution³⁺The detection method comprises the following steps:

and adding the metal organic framework material into the aqueous solution to be tested, dispersing uniformly, and testing the luminescence spectrum of the metal organic framework material.

In some embodiments, the ratio of the aqueous solution to be tested to the metal-organic framework material is 1mL:0.8mg-1.2 mg.

In some of these embodiments, the pH of the aqueous solution to be tested is adjusted to 2-6.

In some of these embodiments, the pH of the aqueous solution to be tested is adjusted to 2-3.

The invention uses terephthalic acid (H)₂BDC), thiophene-2, 5-dicarboxylic acid (H)₂TDC) and terbium nitrate hexahydrate are taken as raw materials, a solvothermal method is adopted, and a novel Tb-based catalyst is successfully synthesized³⁺Metal organic framework material (Tb-MOF) taking terephthalic acid and thiophene-2, 5-dicarboxylic acid as organic ligands as central metal ions. The crystal analysis shows that the structure is an orthorhombic system, and the orthorhombic system is characterized by means of PXRD, TG, IR and the like, so that the synthesized material is proved to be well coincident with the crystal and to have good thermal stability and water stability. Through SEM analysis, the Tb-MOF has larger porosity and abundant reaction sites. Because the ligand in the metal organic framework material is connected with H₂The Tb-MOF synthesized by the invention can show bright green fluorescence in water by an intramolecular proton transfer process between O molecules.

The inventor further researches to find that Tb-MOF synthesized by the invention can quickly, effectively and specifically detect Bi in aqueous solution³⁺And has the advantages of quick response time (9s), high selectivity, strong anti-interference capability, high sensitivity and low detection limit (4.83 mu M), and can be used as a very potential for quickly detecting the metal Bi in water³⁺The fluorescent probe of (1).

Drawings

FIG. 1 is a crystal structure diagram of Tb-MOF, wherein (a) and (b) are Tb³⁺A coordination environment diagram of (a); (c) is a 2D structural diagram of Tb-MOF; (d) 3D Structure of Tb-MOF.

FIG. 2 is an SEM image of Tb-MOF.

FIG. 3 shows Tb-MOF, Tb-MOF @ Bi³⁺The powder X-ray diffraction pattern of (1), in which simullate is the simulation result of the single crystal of Tb-MOF prepared in example 2.

FIG. 4 is a TG map of Tb-MOF.

FIG. 5 is an infrared spectrum of Tb-MOF.

FIG. 6 is an emission spectrum of Tb-MOF at an excitation wavelength of 320 nm.

FIG. 7 is a graph showing the results of the measurement of the sensing performance of Tb-MOF on metal ions, wherein (a) is the fluorescence emission spectrum of Tb-MOF in different metal ion solutions; (b) normalized emission intensity; (c) is Tb-MOF in Bi³⁺And other metals in the mixed solution of luminescence intensity histogram; (d) is fluorescence emission spectrum of Tb-MOF in mixed metal ion water solution.

FIG. 8 shows Bi at different concentrations³⁺Effect of aqueous solutions on the fluorescence quenching Effect of Tb-MOF, wherein (a) is Tb-MOF at different concentrations of Bi³⁺(ii) an overall emission spectrum in aqueous solution; (b) an emission spectrum for detecting a peak around 547 nm; (c) is the luminous intensity of Tb-MOF and Bi³⁺Concentration (0-1000. mu.M), as an inset, the luminescence intensity of Tb-MOF is related to Bi³⁺Linear relationship of concentration (0-10 uM); (d) i being Tb-MOF₀I and Bi³⁺Concentration (0-1000. mu.M), I of Tb-MOF₀I and Bi³⁺Concentration (0-10. mu.M).

FIG. 9 is a graph of the effect of pH on the luminescence intensity of Tb-MOF materials, where (a) is the fluorescence intensity of Tb-MOF at different pH; (b) bi of Tb-MOF at different pH values³⁺Fluorescence intensity in solution.

FIG. 10, (a) shows Tb-MOF in Bi³⁺Fluorescence spectra of different response times in aqueous solution, (b) water stability results of Tb-MOF.

FIG. 11 is a graph showing XPS test results, IR spectra and luminescence lifetime, wherein (a) is Bi addition³⁺Front and rear Tb-XPS total spectra of MOFs; (b) is Bi³⁺XPS spectroscopy of (a); (c) for adding Bi³⁺Front and back Tb-MOF infrared spectrograms; (d) is Tb-MOF and Tb-MOF @ Bi³⁺The emission lifetime map of (1).

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, article, or device that comprises a list of steps is not limited to only those steps or modules listed, but may alternatively include other steps not listed or inherent to such process, method, article, or device.

The "plurality" referred to in the present invention means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.

The experimental reagents used in the following examples are as follows

Terbium nitrate hexahydrate (Tb (NO)₃)₃·6H₂O) (99.9%) from michelin reagent; thiophene-2, 5-dicarboxylic acid (H)₂TDC) (98%), terephthalic acid (H)₂BDC), N-dimethylformamide (DMF, AR) were purchased from the avastin reagent. All reagents were not further purified prior to use and the deionized water used for the experiments was generated by a cell type-1820 a water purifier from Chongqing Moore Water treatment facilities, Inc.

The characterization instruments and test conditions used in the following examples are as follows:

single crystal diffraction data were recorded at Ga-K.alpha.using a German Bruker D8Advance X-ray diffractometer, and powder X-ray diffraction Patterns (PXRD) of samples were recorded at Cu-K.alpha.using a PANALYTIC EMPYREan Series 2 diffractometer from Cibach instruments systems Ltd, UK, in the 2 theta range of 5-50 DEG, operating voltage of 40KV, current of 40mA, step size and scanning speed of 0.026 DEG and 7 DEG min, respectively^-1(ii) a Observing the appearance of the sample by using a JSM-7800F field emission scanning electron microscope of Japan Electron Co; recording TGA data of a sample by using a TGA Q-50 thermogravimetric analyzer of American TA company, wherein the temperature rise rate is 10 ℃/min under the nitrogen atmosphere, and the temperature range is 10-700 ℃; recording the excitation and emission spectra of the sample by a Hitachi F4600 luminescence spectrophotometer; luminescence lifetime and quantum yield were tested by the Edinburgh company FLS 980; measuring an absorption spectrum by a Japanese Shimadzu ultraviolet spectrometer UV-3600; the metal ion content was determined by Agilent 7700(ICP-MS) -element.

The following are specific examples.

EXAMPLE 1 preparation of Metal organic framework Material Tb-MOF

1mmol of Tb (NO)₃)₃·6H₂O, 1mmol of H₂TDC and 1mmol H₂BDC is dissolved in 10mLN of N-Dimethylformamide (DMF) respectively to be completely dissolved, and then the three solutions are mixed together and stirred for ten minutes, and then the mixture is transferred to a high-temperature reaction kettle and reacted for 48 hours in a forced air drying box at 150 ℃. And after the reaction is finished, cooling the solid phase to room temperature, removing supernatant, transferring the solid phase into a centrifugal tube, centrifugally washing the solid phase for 3 times by using DMF (dimethyl formamide) at the rotating speed of 5000r/min, and after the washing is finished, putting the solid phase product into an air drying oven at 70 ℃ for drying for 10 hours to finally obtain white powder, namely Tb-MOF.

Example 2 Structure and Performance characterization of Tb-MOF

(1) Single crystal XRD analysis

1mmol of Tb (NO)₃)₃·6H₂O, 1mmol of H₂TDC and 1mmol H₂BDC was dissolved in 10mLN, N-Dimethylformamide (DMF) respectively to make it completely dissolvedAnd mixing the three solutions together, stirring for ten minutes, transferring to a 40 ℃ forced air drying oven, volatilizing the solvent, and separating out crystals to obtain the Tb-MOF single crystal.

The prepared Tb-MOF single crystal was subjected to single crystal diffraction data testing at Ga-Ka using a German Bruker D8Advance X-ray diffractometer. The test method is as follows: selecting a single crystal with better quality, namely a transparent, crack-free, clean and glossy crystal, measuring the unit cell parameters and the diffraction intensity of the single crystal to obtain an analyzed file, correcting the atomic coordinates and the structure, and finally describing the structure. The results are shown in FIG. 1, Table 1 and Table 3, wherein the crystallographic data of Tb-MOF are shown in Table 1, and the main bond lengths and bond angles of the crystals are shown in Table 2 and Table 3 respectively; tb³⁺The coordination environment diagram and the 2D and 3D structures of (a) are shown in fig. 1.

The single crystal analysis result shows that the GOF value of the crystal is 1.194, which shows that the fitting degree of the analysis result is high. Tb-MOF has the molecular formula C₁₄H₆O₈STb, relative molecular mass 493.17, belongs to orthorhombic system, space group Fmmm, lattice parameter

Form Tb as the ion center, H₂TDC and H₂BDC is the three-dimensional structure of the organic frame. Tb³⁺The coordination environment (A) and (B) in FIG. 1 show that the asymmetric unit contains two H₂BDC and four H₂And (4) TDC. Tb01 coordinates in 8 coordination mode to the surrounding eight oxygen atoms, four of which are derived from two H₂BDC, four oxygen atoms from four H₂TDC from H₂Four O004 s of BDC with Tb by symmetric chelation³⁺Coordination having a Tb-O bond length of

From four H₂Four O005 of TDC are bridged with Tb³⁺Coordination having a Tb-O bond length of

As shown in (c) of FIG. 1Show Tb³⁺And H₂BDC forms a one-dimensional structure and then forms a one-dimensional structure with H₂TDC is bonded to form a two-dimensional structure, and finally a two-dimensional layer is formed by H₂The TDC bridges form a three-dimensional structure, as in (d) of fig. 1.

TABLE 1 Main crystallographic data of Tb-MOF

TABLE 2 partial bond lengths of Tb-MOF crystal structures

Note: the value in the bracket () representing the error of the last digit, e.g.

Finger-shaped

TABLE 3 partial bond angles in Tb-MOF Crystal Structure

Note: the values in brackets () represent the error of the last digit, e.g., 125.9(5) means 125.4-126.4.

(2) Tb-MOF Scanning Electron Microscopy (SEM) morphology analysis

The Tb-MOF powder prepared in example 1 was observed for morphology using a JSM-7800F field emission scanning electron microscope (Nippon electronics Co., Ltd.). And (3) placing the Tb-MOF powder on an observation platform, and setting the magnification of a scanning electron microscope to 20000 times and 100000 times for local topography observation.

The Scanning Electron Microscope (SEM) morphology analysis test result is shown in figure 2, and the prepared Tb-MOF is formed by stacking a large number of irregular blocks, and the structure of the Tb-MOF is porous and spongy, so that the Tb-MOF has a large specific surface area. The Tb-MOF prepared by the invention has high porosity and abundant reaction sites.

(3) PXRD analysis of Tb-MOF

The powder X-ray diffraction Pattern (PXRD) of the sample was measured using 2mg of Tb-MOF prepared in example 1 using a PANALYTICAL Empyrean Series 2 diffractometer from Cibach instruments systems, Inc. of UK under Cu-K α by the following test method: the 2 theta scanning range of PXRD is set to be 5-50 degrees, the working voltage and current are respectively set to be 40KV and 40mA, and the steps of 0.02626 degrees and 5 degrees min are carried out^-1The Tb-MOF powders were tested separately for their scanning speed.

The three strong peaks of the X-ray diffraction Pattern (PXRD) of the Tb-MOF powder are located at 9.5500 °, 10.1616 ° and 19.6927 ° respectively, and their intensities are 13844.7837a.u., 10465.6489a.u., and 8384.2239a.u., respectively, as shown in fig. 3, taking the intensity of the strongest peak as 100%, the relative intensities of the diffraction peaks are as follows:

2θ(°)	relative strength
		9.5500	100％
10.1616	75.59％
		19.6972	60.56％

(4) Thermal stability testing of Tb-MOF

Tb-MOF prepared in example 1 was tested for thermal stability using a TGA Q-50 thermogravimetric analyzer from TA of USA, and TGA data was recorded and tested under nitrogen atmosphere at a temperature rise rate of 20 deg.C/min and a temperature range of 10 deg.C-800 deg.C.

The test result is shown in fig. 4, the first weight loss occurs at 40 ℃ to 286 ℃, the weight loss is about 13%, the weight loss is mainly caused by volatilization of water molecules and solvent molecules in pore channels, and the thermogravimetric curve is kept relatively flat in the temperature range of 286 ℃ to 390 ℃, which proves that Tb-MOF can be kept relatively stable in this temperature range. The second significant weight loss occurred at 390-800 c due to the collapse of the Tb-MOF framework. It can be seen that Tb-MOF can maintain its spatial configuration below 390 ℃ and has good thermal stability.

(5) Infrared spectroscopic characterization of Tb-MOF

Tb-MOF and Tb-MOF @ Bi prepared in example 1³⁺400cm for Nicolet iS50 by Fourier transform infrared spectrometer^-1And (5) performing infrared spectrum characterization.

Its infrared spectrum is characterized by being 1570cm as shown in FIG. 5^-1、1382cm^-1The peak of (a) corresponds to the stretching vibration of C ═ O that has been coordinated.

(6) Luminescence property test of Tb-MOF

The 10mg Tb-MOF powder prepared in example 1 was subjected to excitation and emission spectra measurement by a Hitachi F4600 luminescence spectrophotometer; and the luminescence lifetime was measured by the Edinburgh FLS980, and the quantum yield was measured by the Edinburgh FLS 980.

As shown in FIG. 6, it can be seen that there are four peaks at an excitation wavelength of 320, which correspond to Tb at 494nm, 549nm, 590nm and 624nm³⁺The 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, 5D4 → 7F3 transition. Description of Tb³⁺Successful entry into the organic framework also indicates that the organic linking agent induces Tb through the antenna effect³⁺The light emission of (1). The quantum yield of this material was 48.42% when Tb-MOF powder was measured using the Edinburgh FLS 1000.

Example 3 testing of Metal ion sensing Performance by Tb-MOF

Tb-MOF prepared by the invention has excellent luminescence property, and the metal ion Bi is tested by the embodiment³⁺The detection capability of (1).

(1) Deionized water is used as solvent, and the concentration is respectively prepared to be 1 multiplied by 10^-3mol/L of M (NO)₃)_x(M＝Ag⁺，Al³⁺，Ba² ⁺，Bi³⁺，Ca²⁺，Cd²⁺，Co²⁺，NH⁴⁺，Sr²⁺，Zn²⁺，Y³⁺) An aqueous solution. Then, 2mL of the prepared aqueous solution of metal ions was added with 2mg of each of the Tb-MOF powders prepared in example 1, the powders were uniformly dispersed by sonication for five minutes, and then the luminescence spectra thereof were measured in a quartz cuvette using a Hitachi F-4600 fluorescence spectrophotometer.

FIG. 7 (a) is a histogram of the luminescence intensity of Tb-MOF suspension containing different metal ions at an excitation wavelength of 310nm, FIG. 7 (b) is a normalized fluorescence intensity of the fluorescence intensity of Tb-MOF at 547nm in an aqueous solution of different metal ions, and it can be seen that some metals have only a slight influence on Tb-MOF with respect to the emission spectrum of Tb-MOF in water, but Bi has a slight influence on Tb-MOF³⁺The fluorescence of Tb-MOF is quenched in the aqueous solution of (1).

(2) The anti-interference capability is an important index for measuring the detection performance of the sensing material in a complex external environment, and on the basis of the first experiment, the experiment tests the coexisting ion pair Bi³⁺The effect of fluorescence sensing was turned off. Preparation of a composition containing 1mM Bi according to the method of example (1)³⁺And 1mM of aqueous solution of different metal ions, 2mL of the prepared aqueous solution of the metal ions is added with 2mg of Tb-MOF powder prepared in example 1 respectively, and after the powder is dispersed uniformly by ultrasonic treatment for five minutes, the luminescence spectrum of the powder is tested in a quartz cuvette by using a Hitachi F-4600 fluorescence spectrophotometer.

The test results are shown in FIGS. 7 (c) and (d), by detecting Bi³⁺The fluorescence intensity in the presence of other metal ions shows that most of the cations are Bi³⁺The influence of the sensing can be negligible or slightly influenced; by detecting Bi³⁺Separate from various metalsFluorescence intensity in the presence of both ions indicates that other metal ions are coupled to Bi³⁺The influence of the quenching effect of (A) is negligible, which indicates that Tb-MOF still has an influence on Bi under the interference of external ions³⁺Has excellent selectivity to Bi in practical environment³⁺The detection has certain application value.

(3) Bi of different concentrations³⁺Effect of aqueous solution on fluorescence quenching of Tb-MOF: 2mg of Tb-MOF powder was placed in 2mL of Bi (NO) (0, 2, 4, 6, 8, 10, 20, 40, 60, 80, 100, 200, 400, 600, 800, 1000. mu.M) with different concentrations₃)₃In the water solution, the powder is dispersed evenly by ultrasonic for five minutes, and then the fluorescence spectrum of the powder is detected in a quartz cuvette by a Hitachi F-4600 fluorescence spectrophotometer.

The emission spectrum of Tb-MOF is shown in (a), (b) of FIG. 8, and it can be seen that with Bi³⁺Increase in concentration, Tb³⁺Gradually decrease in emission peak intensity of Bi³⁺At a concentration of 1mM, the luminescence of Tb-MOF was completely quenched.

(4) Calculation of Bi³⁺The sensing sensitivity of (2): different Bi³⁺The luminescence intensity of Tb-MOF at the concentration was fitted, and as shown in (c) of FIG. 8, Bi was present in the concentration range of 0 to 1000. mu.M³⁺The relationship between concentration and luminescence intensity of Tb-MOF is exponential, and satisfies the function y ═ 0.43exp (-x/-219.9) +1992exp (-x/436.46) +2012exp (-x/436.37) -325.21, and the degree of fitting R is²0.9972. Then to 0-10 mu M Bi³⁺The intensity of light emission in the concentration range was linearly fitted, and as shown in (c) of fig. 8, the curve satisfied the linear relationship of y-117.96 x +4862.29, R²0.996. According to the slope of the inner curve of 0-10 mu M and the detection limit formula, the Tb-MOF to Bi can be calculated³⁺Limit of detection (LOD). Such as formula (1)

Wherein N represents the absence of Bi³⁺When the fluorescence intensity of Tb-MOF in the aqueous solution is measured, F represents the average value of F0, F0 is the fluorescence intensity of Tb-MOF in the aqueous solution, S_bIs standard deviation, S is Bi in the figure³⁺The slope of the fitted curve at concentrations between 0 and 10. mu.M. Substituting the above numerical values to calculate Bi of Tb-MOF in water³⁺Has a limit of detection (LOD) of about 4.83. mu.M, indicating that Tb-MOF prepared is coupled to Bi³⁺Has a lower detection limit.

Tb-MOF detection of Bi³⁺The quenching constant of (A) can be calculated by the Stern-Volmer equation, as shown in formula (3),

wherein I₀Showing the fluorescence intensity of Tb-MOF in water, I showing that Tb-MOF contains Bi³⁺The fluorescence intensity in the aqueous solution of (1). [ M ] A]Is the corresponding Bi³⁺The Ksv represents the quenching constant of the sample. When Bi is present as shown in (d) of FIG. 8³⁺The concentration is in the range of 0-1000. mu.M, the variation relation satisfies the exponential relation of y ═ 0.43exp (-x/-219.9) +0.86, the degree of fitting R²0.9996; when Bi is present as shown in (d) of FIG. 8³⁺At a concentration in the range of 0-10. mu.M, Bi³⁺The Stern-Volmer curve of (a) satisfies the linear relationship y of 0.99+0.031x, and the linearity is about 0.9964. Substituting into equation to obtain Bi³⁺Quenching constant Ksv 0.02678 μ M for Tb-MOF^-1The result shows that Tb-MOF can detect Bi in water by the principle of fluorescence quenching³⁺。

(5) Tb-MOF was tested for fluorescence intensity at different pH values:

NaOH and HCl were used as test materials, and aqueous solutions having different pH values (3, 4, 5, 6, 7, 8, 9, 10, and 11) were prepared using a pH meter. 2mg of Tb-MOF powder was placed in 2mL of aqueous solution of different pH values and sonicated for 5 minutes to disperse the powder evenly in the aqueous solution. The fluorescence intensity of Tb-MOF in aqueous solutions of different pH values was measured by Hitachi F-4600 fluorescence spectrophotometer.

As a result of the test, as shown in FIG. 9 (a), it can be seen that the fluorescence intensity was highest at pH 6, and the fluorescence intensity decreased to different degrees as the pH increased or decreased. When the pH value is reduced, the fluorescence intensity is reduced because the Tb-MOF surface is protonated, and a conjugated p-electron system is not harmonious, so that the luminous intensity is influenced.

(6) Testing different pH values to Bi³⁺Influence of quenching effect of (1):

first, Bi (NO) with different pH values (2.76, 2.98, 3.89, 4.42 and 5.45) is prepared₃)₃Aqueous solution, 2mg of Tb-MOF powder was added to 2mL of Bi (NO) of different pH values₃)₃In the aqueous solution, and the powder was dispersed uniformly by sonication for 5 minutes. Bi (NO) of Tb-MOF powder at different pH values was tested by Hitachi F-4600 fluorescence spectrophotometer₃)₃Fluorescence intensity in aqueous solution.

The results of the measurement are shown in FIG. 9 (b), and 1mM Bi was measured at room temperature³⁺The pH of the aqueous solution was 2.76, and it can be seen that with Bi³⁺The increase in the pH of the aqueous solution also increases the fluorescence intensity, which can be attributed to the fact that higher pH values are detrimental to free Bi³⁺And (4) generating.

(7) Testing Tb-MOF vs Bi³⁺Response time of and Water stability of Tb-MOF

2mg of Tb-MOF powder was added to 2mL of Bi (NO)₃)₃In the aqueous solution, and the powder was dispersed uniformly by sonication for 5 minutes. Testing of Tb-MOF powder in Bi by Hitachi F-4600 fluorescence spectrophotometer³⁺Fluorescence intensity of the aqueous solution to test its response time. As a result of the test shown in FIG. 10 (a), the fluorescence intensity reached equilibrium from the ninth second, indicating that Tb-MOF is a substance capable of rapidly detecting Bi in water³⁺The fluorescence sensor of (1).

Putting 3mg of Tb-MOF into 3mL of deionized water, performing ultrasonic treatment for 10 minutes, and respectively testing fluorescence spectra at intervals of one week, two weeks, three weeks and four weeks, wherein as shown in (b) in FIG. 10, the fluorescence intensity is not greatly reduced along with the increase of time, and Tb-MOF still keeps strong green fluorescence after four weeks, which indicates that Tb-MOF has good water stability.

EXAMPLE 4 investigationTb-MOF on Bi³⁺Sensing mechanism of

Generally, the reasons for the quenching of the fluorescence of the MOFs can be divided into: (1) collapse of MOFs structure, (2) replacement of the central ion of MOFs by the target detection substance, (3) competitive absorption of photons between the detection ion and MOFs, and (4) interaction between the target molecule and the ligand.

(1) 50mg of Tb-MOF was placed in 50mL of 1mM Bi (NO)₃)₃Reacting in water solution for five minutes, centrifuging, taking a solid phase, drying in an air drying oven at 70 ℃ for 6 hours to obtain Tb-MOF @ Bi³⁺The powder X-ray diffraction Pattern (PXRD) was measured using a PANALYTIC EMPYREAN Series 2 diffractometer from Cibach instruments systems, Inc. of UK under the following test conditions: the 2 theta range is 5-50 degrees, the working voltage is 40KV, the current is 40mA, and the step length and the scanning speed are 0.02626 degrees and 7 degrees min respectively^-1。

The results of the tests are shown in FIG. 3 by comparing Tb-MOF in Bi³⁺The position of main diffraction peaks of PXRD before and after soaking in the solution is basically consistent with that of the main diffraction peaks of PXRD before and after soaking in the solution, which shows that Tb-MOF has basically unchanged structure in the sensing process and contains Bi³⁺The Tb-MOF and the Tb-MOF have the same structure.

(2) 20mg of Tb-MOF was placed in 20mL of 1mM Bi (NO)₃)₃Reacting the aqueous solution for five minutes, centrifuging, taking the solid phase, drying the solid phase in an air drying oven at 70 ℃ for 6 hours to obtain Tb-MOF @ Bi³⁺And then carrying out XPS test on the strain: the sample was tested using ESCALB 250Xi X-ray photoelectron spectroscopy, by Seimer Feishell technology, using 1mg of Tb-MOF @ Bi³⁺The powder sample is adhered to the double-sided carbon conductive adhesive, the conductive adhesive is adhered to a sample table, the sample is irradiated by X-rays, and photoelectrons are emitted by ionization to analyze the electron binding energy.

As shown in FIGS. 11 (a), (b), XPS showed that Bi appeared at 164.3eV and 159eV on the spectrum³⁺Shows that there is Bi in the material³⁺Are present. The Auger peak of Tb in (a) in FIG. 11 disappeared, and it can be presumed that its disappearance was attributable to the addition of Bi³⁺Before and after Tb, the coordination environment is changed. Addition of Bi by comparison with Tb-MOF³⁺Front and rear infraredSpectrum, as shown in (c) of FIG. 11, wherein 1570cm^-1And 1382cm^-1Peaks at (a) can be assigned to symmetric stretching and asymmetric stretching of the bridging carboxylate groups, respectively; Tb-MOF in Bi can be seen³⁺Soaking in water solution at 1570cm^-1And 1382cm^-1The peak of (A) is almost disappeared because Bi³⁺Coordination with-COO-attenuates stretching vibration of C ═ O.

(3) For Tb-MOF and Tb-MOF @ Bi³⁺The fluorescence lifetime of (a):

50mg of Tb-MOF was placed in 50mL of 1mM Bi (NO)₃)₃Reacting in water solution for five minutes, centrifuging, taking a solid phase, drying in an air drying oven for 6 hours to obtain Tb-MOF @ Bi³⁺. Tb-MOF @ Bi by utilizing Edinburgh FLS980 transient fluorescence spectrometer³⁺The powder was subjected to a luminescence time test to test its fluorescence lifetime.

As shown in FIG. 11 (d), the luminescence lifetime of Tb-MOF was about 0.42ms, and Tb-MOF @ Bi³⁺Has a luminescence lifetime of about 0.24ms, Tb-MOF in Bi³⁺After the material is soaked in an aqueous solution, the luminescence life is obviously reduced, the static quenching mechanism is met, and a new non-luminescent compound is formed by Tb-MOF and a quencher, so that fluorescence quenching is caused.

(4) Testing the content of metal ions in the solution by inductively coupled plasma: 5mL of Bi (NO) 1mM were each collected₃)₃The aqueous solution was put into two centrifuge tubes, 5mg of Tb-MOF powder was added to one of the centrifuge tubes, and the mixture was centrifuged to obtain a supernatant. Separately testing Bi in two tubes³⁺And Tb³⁺And (4) content.

The results are shown in Table 4, from which it can be seen that Bi is present after the addition of Tb-MOF³⁺Bi in aqueous solution³⁺The content is sharply reduced, and simultaneously Tb³⁺The content of (A) is obviously increased.

TABLE 4 ICP data for each metal content in aqueous Bi3+ solutions after Tb-MOF addition

In conclusion, causeThe mechanism of fluorescence quenching of Tb-MOF is Bi³⁺With Tb in Tb-MOF³⁺The replacement reaction is carried out, and the synthesized novel Tb-MOF can react with Bi³⁺Effective detection is carried out, and the method is very potential and can quickly detect Bi³⁺The fluorescent probe of (1).

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A metal organic frame material is characterized in that the central metal ion is Tb³⁺The organic ligand is terephthalic acid and thiophene-2, 5-dicarboxylic acid.

2. The metal-organic framework material of claim 1, prepared from terbium nitrate hexahydrate, terephthalic acid, and thiophene-2, 5-dicarboxylic acid.

3. The metal-organic framework material according to claim 2, wherein the molar ratio of the reaction charge of terbium nitrate hexahydrate, terephthalic acid and thiophene-2, 5-dicarboxylic acid is 1: 0.8-1.2: 0.8-1.2.

4. The metal-organic framework material of claim 1, wherein Tb is in the crystal structure of the metal-organic framework material³⁺In 8 coordination mode with the surrounding eight oxygensThe atoms are coordinated in that four oxygen atoms are derived from two terephthalic acids and four oxygen atoms are derived from four thiophene-2, 5-dicarboxylic acids.

5. The metal-organic framework material of claim 4, wherein the crystal structure of the metal-organic framework material is orthorhombic, the space group is Fmmm, and the lattice parameters are as follows:

the Z value is 8;

four oxygen atoms from two terephthalic acids in the crystal structure of the metal organic framework material adopt symmetric chelation and Tb³⁺Coordination having a Tb-O bond length of

The bond angles in the crystal structure of the metal-organic framework material are shown in the following table:

wherein O004 is an oxygen atom derived from terephthalic acid; o005 isOxygen atom from thiophene-2, 5-dicarboxylic acid, Tb01 as central metal ion Tb³⁺。

6. The metal-organic framework material of claim 1, wherein the metal-organic framework material has diffraction peaks at 2 θ -9.5500 °, 10.1616 °, 19.6972 ° as measured by X-ray powder diffraction method of Cu-K α, the relative intensities of the diffraction peaks are as follows:

2θ(°) relative strength 9.5500 100％ 10.1616 75.59％ 19.6972 60.56％。

7. A method for preparing a metal organic framework material according to any one of claims 1 to 6, comprising the steps of:

8. The method for preparing a metal organic framework material according to claim 7, wherein the organic solvent is N, N-dimethylformamide; and/or the presence of a gas in the gas,

the concentrations of the terbium nitrate hexahydrate solution, the terephthalic acid solution and the thiophene-2, 5-dicarboxylic acid solution are all 0.8mmol/mL-1.2 mmol/mL; and/or the presence of a gas in the gas,

the reaction temperature in the step (2) is 145-155 ℃, and the reaction time is 44-52 hours.

9. Use of the metal-organic framework material of any one of claims 1 to 6 as a fluorescent probe in the detection of Bi³⁺Application in metal ions.

10. Use of the metal-organic framework material of any one of claims 1 to 6 as a fluorescent probe for detecting Bi in an aqueous solution³⁺Application in metal ions.

11. Bi in aqueous solution³⁺The detection method is characterized by comprising the following steps:

adding the metal organic framework material of any one of claims 1 to 6 into an aqueous solution to be tested, uniformly dispersing, and testing the luminescence spectrum of the metal organic framework material.

12. The method of claim 11 wherein Bi is present in said aqueous solution³⁺The detection method is characterized in that the ratio of the aqueous solution to be detected to the metal organic framework material is 1mL and 0.8mg-1.2 mg.

13. The aqueous solution of claim 11 or 12 of Bi³⁺The detection method of (1), characterized in that the pH of the aqueous solution to be detected is adjusted to 2 to 6.

14. The method of claim 13 wherein Bi is present in said aqueous solution³⁺Characterized in that the aqueous solution to be measured is adjustedThe pH is 2-3.