A crystal material based on fluorene ring ligand, its preparation method and application in luminescence-enhanced detection of Hg 2+ ​

Abstract

The application discloses a crystal material based on a fluorene ring ligand, a preparation method thereof and application of the crystal material in luminescence-enhanced detection of Hg 2+ . A luminescent metal-organic framework crystal material [Cd3(L)2(NDA)3(H2O)2.L] is prepared based on a 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine functional ligand for the first time. n The method is simple, the synthesis route is simple and easy to control, the yield of the product can reach 42.3%, and the method is suitable for industrial production. Compared with the prior art, the material can first luminescence-enhanced detect Hg 2+ , has extremely high sensitivity, has a high quenching constant of up to -2.12*10 2+ M 4 for luminescence-enhanced detection of Hg ‑1 in an aqueous phase, and has a low detection limit of 3.51*10 ‑7 M, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of luminescent detection functional materials, and particularly relates to a crystal material based on fluorene ring ligand and a preparation method thereof and application of the crystal material in luminescent enhancement detection of Hg 2+ . BACKGROUND

[0002] Mercury ion (Hg 2+ ) is a heavy metal ion, which is usually released into the nature through geological activities or industrial production. Since Hg 2+ is difficult to degrade, it is easy to accumulate in the human body through the food chain. Many studies have shown that long-term intake of Hg 2+ may cause various nervous system diseases and eventually lead to human death. At present, the detection of mercury ions is realized through various analysis technologies such as voltammetry, chromatography, inductively coupled plasma mass spectrometry, atomic absorption spectrometry, etc. These analysis methods are costly and the instrument operation is complex, and in complex water environment, their sensing sensitivity and selectivity are also challenged. Therefore, it is necessary and urgent to develop detection materials based on low cost, high selectivity and rapid detection of mercury ions.

[0003] Luminescent metal-organic framework sensing materials have the advantages of convenient detection, rapidness, sensitivity, high selectivity, etc., and have been developed and applied to luminescent detection of metal ions. The organic ligand plays a decisive role in the luminescent detection performance of the metal-organic framework crystal material, and the fluorene ring organic structure has a large rigid plane and luminescent performance, which is conducive to improving the stability and luminescent performance of the metal-organic framework crystal material constructed. Therefore, it is of great significance to develop fluorene ring ligand to synthesize metal-organic framework crystal materials with luminescent detection function. SUMMARY

[0004] This section aims to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title. Such simplifications or omissions cannot be used to limit the scope of the present application.

[0005] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0006] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art, and to provide a crystal material based on fluorene ring ligand, comprising,

[0007] The chemical formula of the crystal material is [Cd3(L)2(NDA)3(H2O)2·L] n ,

[0008] wherein L is a fluorene ring ligand, NDA2- is 1,4-naphthalenedicarboxylate anion ligand, n is any value;

[0009] The structure of the fluorene ring ligand is shown as formula (I):

[0010]

[0011] The crystal system of the crystal material is triclinic, the space group is P-1, and the cell parameters are Alpha=109.942(4) degrees, beta=93.638(3) degrees, gamma=100.064(4) degrees, and Z=2.

[0012] Another object of the present application is to overcome the deficiencies in the prior art and provide a preparation method of a crystal material based on a fluorene ring ligand.

[0013] To solve the above technical problems, the present application provides the following technical solutions: comprising,

[0014] The cadmium acetate dihydrate, 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine and 1,4-naphthalenedicarboxylic acid are added to a mixed solvent of water and methanol to prepare a mixed solution by stirring;

[0015] The mixed solution is placed in a sealed reaction kettle for heating reaction, and then cooled to room temperature. The product is filtered, washed and dried to obtain a luminescent metal-organic framework crystal material [Cd3(L)2(NDA)3(H2O)2·L] n .

[0016] As a preferred scheme of the preparation method of the crystal material based on the fluorene ring ligand, the molar ratio of the cadmium acetate dihydrate, 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine and 1,4-naphthalenedicarboxylic acid is 1:0.5-2:0.5-2.

[0017] As a preferred scheme of the preparation method of the crystal material based on the fluorene ring ligand, the volume ratio of water and methanol in the mixed solvent is 1:0.5-2.

[0018] As a preferred scheme of the preparation method of the crystal material based on the fluorene ring ligand, the volume of the mixed solvent of water and methanol required for 0.1 mmol of cadmium acetate dihydrate is 4-12 ml.

[0019] As a preferred scheme of the preparation method of the crystal material based on the fluorene ring ligand, the heating reaction is carried out at a temperature of 120-180 DEG C for 48-72 h.

[0020] As a preferred scheme of the preparation method of the crystal material based on the fluorene ring ligand according to the present application, wherein: the temperature is reduced to room temperature, and the temperature reduction rate is 2-5 DEG C / h.

[0021] Another object of the present application is to overcome the deficiencies in the prior art and provide an application of the crystal material based on the fluorene ring ligand in luminescence-enhanced detection of Hg 2+ .

[0022] As a preferred scheme of the application of the crystal material based on the fluorene ring ligand according to the present application in luminescence-enhanced detection of Hg 2+ , wherein: the quenching constant of the crystal material based on the fluorene ring ligand in luminescence-enhanced detection of Hg 2+ in aqueous phase is -2.12*10 4 M -1 .

[0023] As a preferred scheme of the application of the crystal material based on the fluorene ring ligand according to the present application in luminescence-enhanced detection of Hg 2+ , wherein: the detection limit of the crystal material based on the fluorene ring ligand in luminescence-enhanced detection of Hg 2+ in aqueous phase is 3.51*10 -7 M.

[0024] The present application has the following beneficial effects:

[0025] (1) The present application first obtains a luminescent metal-organic framework crystal material based on the fluorene ring ligand 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine, the synthesis route of the material is simple and easy to control, the product yield can reach 42.3%, and the material is suitable for industrialized production and promotion.

[0026] (2) The material [Cd3(L)2(NDA)3(H2O)2*L] n prepared by the present application is first used in luminescence-enhanced detection of Hg 2+ , compared with the prior art, the crystal material is simple and reliable in application, the quenching constant of the crystal material in luminescence-enhanced detection of Hg 2+ in aqueous phase reaches -2.12*10 4 M -1 , the detection limit is as low as 3.51*10 -7 M, and the material has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0028] Figure 1 The 1H NMR spectrum of ligand L, namely 4,4'-((2,7-di-tert-butyl-9H-fluorene-9-yl)methylene)dipyridine, prepared in Example 1 of this invention.

[0029] Figure 2 The luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Example 1 of this invention n The two-dimensional crystal structure diagram.

[0030] Figure 3 The luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Example 1 of this invention n X-ray diffraction pattern of the powder.

[0031] Figure 4 The luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Example 1 of this invention n Excitation and emission spectra of an aqueous suspension (0.1 mg / mL).

[0032] Figure 5 The luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Example 1 of this invention. n The graph shows the changes in luminescence intensity when different volumes of mercury ion aqueous solution (1 mmol / L) are added to an aqueous suspension.

[0033] Figure 6 The luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Example 1 of this invention n A quenching constant curve for detecting mercury ions.

[0034] Figure 7 The luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Example 1 of this invention n Detection limit curve for mercury ions.

[0035] Figure 8 The luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Comparative Example 1 of this invention is shown in Example 1 of this invention. n Quenching efficiency diagram when different cations are added to an aqueous suspension. Detailed Implementation

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0037] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without the specific details set forth in this description. In other instances, well-known methods have not been described in detail in order to avoid obscuring the present application. Therefore, the present application is not intended to be limited by the specific embodiments disclosed below, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0038] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is independent or alternative to other embodiments.

[0039] The chemical reagents used in the embodiments of the present application are all ordinary commercially available analytical pure, unless otherwise specified.

[0040] The calculation method of the yield in the embodiments of the present application is based on L to calculate the yield, and the calculation steps are:

[0041] m (actual crystal) / m (L complete reaction)

[0042] Embodiment 1

[0043] The present embodiment provides a preparation method of a crystal material based on fluorene ring ligand:

[0044] 1) Synthesis of 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine:

[0045] 2,7-di-tert-butyl-9-fluorenone (5.848 g, 20.0 mmol), carbon tetrabromide (13.270 g, 40.0 mmol), triphenylphosphine (17.530 g, 80.0 mmol) were dissolved in 150 mL of toluene and stirred, heated at 60°C for 24 h; after filtration, vacuum distillation was carried out, anhydrous ethanol was added, and it was recrystallized overnight to obtain bright yellow crystals of 2,7-di-tert-butyl-9-(dibromomethyl)-9-fluorenone, with a yield of 80%;

[0046] 2,7-di-tert-butyl-9-(dibromomethyl)-9-fluorenone (448.24 mg, 1.00 mmol), 4-pyridine boronic acid (615 mg, 5.00 mmol), sodium carbonate (690 mg, 5.00 mmol), tetrakis(triphenylphosphine)palladium (115.6 mg, 0.10 mmol) were added to 50 mL of mixed solvent 1,4-dioxane / water (V dioxane:V water = 4:1), heated to 120°C for 24 h under nitrogen atmosphere;

[0047] After extraction, the organic components were purified by flash column chromatography using ethyl acetate / petroleum ether as the mobile phase to obtain the pure product ligand (L, 444.6 mg, 1.00 mmol).

[0048] The structural formula of the prepared ligand L is shown as formula (I):

[0049]

[0050] Figure 1 The nuclear magnetic hydrogen spectrum of the ligand L prepared in this example is shown in the following table: 1 H NMR (400 MHz, CDCl3) δ 8.77-8.70 (m, 4H), 7.53 (d, J = 7.9 Hz, 2H), 7.40-7.33 (m, 4H), 7.29 (dd, J = 8.0, 1.7 Hz, 2H), 6.68 (d, J = 1.7 Hz, 2H), 1.06 (s, 18H), indicating the successful preparation of ligand L.

[0051] 2) Preparation of luminescent crystalline material [Cd3(L)2(NDA)3(H2O)2·L] n .

[0052] 0.05 mmol of cadmium acetate dihydrate, 0.025 mmol of 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine, and 0.05 mmol of 1,4-naphthalenedicarboxylic acid were added to 3 mL of a mixed solvent (V water:V methanol = 1:1) and stirred to prepare a mixed solution;

[0053] The prepared mixed solution was placed in a sealed reaction kettle and heated to 150°C for 48 h. After slowly cooling to room temperature at a rate of 2°C / h, the product was filtered and washed with deionized water and methanol in sequence to obtain the crystalline material [Cd3(L)2(NDA)3(H2O)2·L] n .

[0054] The calculated yield was 42.3%.

[0055] The single crystal structure of the crystalline material of this example was determined using an ApexII single crystal diffractometer of Bruker Company. The specific crystal structure determination data are shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] As shown in Table 1, the molecular formula of the prepared luminescent metal-organic framework crystalline material is C 132 H118 Cd3N6O 14 Crystal system: triclinic; space group: P-1; unit cell parameters: α=109.942(4)°, β=93.638(3)°, γ=100.064(4)°, Z=2.

[0060] Figure 2 The crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in this embodiment. n A two-dimensional crystal structure diagram (hydrogen atoms are omitted).

[0061] Figure 3 The crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in this embodiment. n The powder X-ray diffraction pattern, upon comparison, is basically consistent with the theoretically calculated X-ray diffraction pattern, indicating that the crystal material prepared in this embodiment has high purity.

[0062] Figure 4 The crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in this embodiment. n The fluorescence properties in the aqueous suspension were analyzed, and the maximum excitation wavelength for detecting mercury ions was found to be 320 nm and the maximum emission wavelength was 480 nm.

[0063] Application testing

[0064] Figure 5 To prepare 2.5 mL of the crystalline material [Cd3(L)2(NDA)3(H2O)2·L] with a concentration of 0.1 mg / mL in this example. n The luminescence intensity curves of adding different volumes of 1 mmol / L mercury ion aqueous solution to the aqueous suspension were obtained. The luminescence intensity of the aqueous suspension of the crystal material was measured at an excitation wavelength of 320 nm. It can be seen that the luminescence intensity of the suspension gradually increases with the gradual increase of the amount of mercury ions.

[0065] Figure 6 , Figure 7 The crystal materials [Cd3(L)2(NDA)3(H2O)2·L] prepared in this embodiment are respectively. n Detection of Hg in aqueous phase 2+ The quenching constant curve and detection limit curve were obtained, and the results showed that the material could enhance the detection of Hg in the aqueous phase. 2+ The quenching constant is -2.12 × 10⁻⁶. 4 M -1 The detection limit is 3.51 × 10⁻⁶. -7M, which indicates that the crystal material prepared in this example can detect water-phase Hg2+ with extremely sensitive luminescence enhancement 2+ .

[0066] Comparative Example 1

[0067] To the water suspension of the luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in Example 1, different cations (Na+, Mg2+, Al3+, Ag+, Cd2+, Zn2+, Cr3+, Hg2+) of the same concentration and the same volume were added, and the quenching efficiency was detected, and a comparison chart of quenching efficiency was obtained, as shown in Figure 1. It can be seen that only Hg2+ can obviously cause the luminescent crystal material [Cd3(L)2(NDA)3(H2O)2·L] prepared in the application to have a significant emission enhancement phenomenon, that is, the [Cd3(L)2(NDA)3(H2O)2·L] obtained in the application has a specific detection effect on Hg2+. n + 2+ 3+ + 2+ 2+ 3+ 2+ Figure 8 2+ n n 2+

[0068] Example 2

[0069] The difference between this example and Example 1 is that the amount of cadmium acetate dihydrate added in step 2) of Example 1 is adjusted to 0.025 mmol, and the rate of cooling to room temperature is adjusted to 3°C / h, and the rest of the preparation process is the same as that of Example 1, and the crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example is obtained, and the calculated yield is 36.2%. n

[0070] Example 3

[0071] The difference between this example and Example 1 is that the amount of 1,4-naphthalene dicarboxylic acid added in step 2) of Example 1 is adjusted to 0.025 mmol, and the heating time in the reaction kettle is adjusted to 72 h, and the rest of the preparation process is the same as that of Example 1, and the crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example is obtained, and the calculated yield is 33.0%. n

[0072] Comparative Example 2

[0073] ​​​​​​​​​​​​​​​​The difference between this comparative example and Example 1 is that the molar ratio of cadmium acetate dihydrate, 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine, and 1,4-naphthalene dicarboxylic acid in step 2) of Example 1 is adjusted to 3:1:3, and the rest of the preparation process is the same as that of Example 1. The solution is turbid, no crystal is generated, and the preparation is unsuccessful.

[0074] Table 2 is the synthesis conditions of Examples 1-3 and Comparative Example 2 and the yield under the corresponding conditions.

[0075] Table 2

[0076]

[0077] As can be seen from Table 2, the yield of the synthesized product is related to the molar ratio of cadmium acetate dihydrate and organic complex and 1,4-naphthalene dicarboxylic acid, and the luminescent crystal material cannot be successfully synthesized when the molar ratio is 3:1:3.

[0078] Example 4

[0079] The difference between this example and Example 1 is that the amount of cadmium acetate dihydrate added in step 2) of Example 1 is adjusted to 0.025 mmol, the amount of 1,4-naphthalene dicarboxylic acid added is adjusted to 0.025 mmol, the amount of mixed solvent added is adjusted to 1.5 mL, and the heating reaction time in the reaction kettle is adjusted to 72 h, and the rest of the preparation process is the same as that of Example 1, obtaining the crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example. n , and the calculated yield is 13.9%.

[0080] Example 5

[0081] The difference between this example and Example 1 is that the amount of mixed solvent added in step 2) of Example 1 is adjusted to 6 mL, the heating reaction time in the reaction kettle is adjusted to 72 h, and the cooling rate to room temperature is adjusted to 3°C / h, and the rest of the preparation process is the same as that of Example 1, obtaining the crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example. n , and the calculated yield is 23.1%.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 1 is that the volume of mixed solvent in step 2) of Example 1 is adjusted to 1 mL (Vwater:Vmethanol=1:1), and the rest of the preparation process is the same as that of Example 1. The solution is turbid, no crystal is generated, and the preparation is unsuccessful.

[0084] Comparative Example 4

[0085] The difference between this comparative example and Example 1 is that the volume of the mixed solvent in step 2) of Example 1 is adjusted to 7 mL (Vwater:Vmethanol = 1:1), and the rest of the preparation process is the same as that of Example 1. The solution is turbid, and no crystal is generated, and the preparation is unsuccessful.

[0086] Table 3 is the synthesis conditions of Example 1, Examples 4-5 and Comparative Examples 3-4 and the yield under the corresponding conditions.

[0087] Table 3

[0088]

[0089] As can be seen from Table 3, the yield of the synthesized product is related to the volume of the mixed solvent, and the synthesis of the luminescent crystal material cannot be successfully carried out when the volume of the mixed solvent is too high or too low.

[0090] Example 6

[0091] The difference between this example and Example 1 is that the amount of cadmium acetate dihydrate added in step 2) of Example 1 is adjusted to 0.025 mmol, the amount of 1,4-naphthalene dicarboxylic acid added is adjusted to 0.025 mmol, the volume ratio of water and methanol in the mixed solvent is adjusted to 1:2, the heating temperature in the reaction kettle is adjusted to 120°C, and the heating reaction time in the reaction kettle is adjusted to 72 h, and the rest of the preparation process is the same as that of Example 1. The crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example is obtained. n , and the calculated yield is 19.5%.

[0092] Example 7

[0093] The difference between this example and Example 1 is that the volume ratio of water and methanol in the mixed solvent in step 2) of Example 1 is adjusted to 1:0.5, and the rest of the preparation process is the same as that of Example 1. The crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example is obtained. n , and the calculated yield is 15.1%.

[0094] Comparative Example 5

[0095] The difference between this comparative example and Example 1 is that the volume ratio of water and methanol in the mixed solvent in step 2) of Example 1 is adjusted to 1:3, and the rest of the preparation process is the same as that of Example 1. The solution is clear, no crystal is generated, and the preparation is unsuccessful.

[0096] Comparative Example 6

[0097] The difference between this comparative example and Example 1 is that no methanol is added in the mixed solvent in step 2) of Example 1, and the rest of the preparation process is the same as that of Example 1. The solution is turbid, there is a large amount of precipitate, no crystal is generated, and the preparation is unsuccessful.

[0098] Table 4 is the synthesis conditions of Example 1, Examples 6-7 and Comparative Examples 5-6 and the yield under the corresponding conditions.

[0099] Table 4

[0100]

[0101]

[0102] As can be seen from Table 4, the yield of the synthesized product is related to the volume ratio of water and methanol in the mixed solvent, and the volume ratio of water and methanol in the mixed solvent is too large or too small, which cannot successfully synthesize the luminescent crystal material.

[0103] Example 8

[0104] The difference between this example and Example 1 is that the heating temperature in the reaction kettle in step 2) of Example 1 is adjusted to 130°C, and the heating reaction time in the reaction kettle is adjusted to 72h, and the rest of the preparation process is the same as Example 1, and the crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example is obtained. n The calculated yield is 27.7%.

[0105] Comparative Example 7

[0106] The difference between this comparative example and Example 1 is that the reaction temperature in step 2) of Example 1 is adjusted to 100°C, and the rest of the preparation process is the same as Example 1. The crystal growth is not complete enough, and the quality is poor, which cannot be tested subsequently.

[0107] Table 5 is the synthesis conditions of Example 1, Example 8 and Comparative Example 7 and the yield under the corresponding conditions.

[0108] Table 5

[0109]

[0110] As can be seen from Table 5, the yield of the synthesized product is related to the heating temperature, and the heating temperature is too low, which cannot successfully synthesize the luminescent crystal material.

[0111] Example 9

[0112] The difference between this example and Example 1 is that the amount of the mixed solvent added in step 2) of Example 1 is adjusted to 6mL, the volume ratio of water and methanol in the mixed solvent is adjusted to 1:2, and the rate of cooling to room temperature is adjusted to 5°C / h, and the rest of the preparation process is the same as Example 1. The crystal material [Cd3(L)2(NDA)3(H2O)2·L] of this example is obtained. n The calculated yield is 11.2%.

[0113] Comparative Example 8

[0114] The difference between the present comparative example and Example 1 is that the cooling rate in step 2) of Example 1 is adjusted to 1℃ / h, and the rest of the preparation process is the same as that of Example 1. The yield is not obviously improved, and the experimental process is slow, which causes unnecessary waste of resources.

[0115] Comparative Example 9

[0116] The difference between the present comparative example and Example 1 is that the cooling rate in step 2) of Example 1 is adjusted to 6℃ / h, and the rest of the preparation process is the same as that of Example 1. The crystallization of the crystal is affected, and the quality is poor, so that the subsequent test cannot be carried out.

[0117] Table 6 is the synthesis conditions of Example 1, Example 9 and Comparative Examples 8-9 and the yield under the corresponding conditions.

[0118] Table 6

[0119]

[0120] As can be seen from Table 6, the yield of the synthesized product is related to the cooling rate. When the cooling rate is 2-5℃ / h, the luminescent crystal material can be successfully prepared, while the cooling rate is too high or too low, and the luminescent crystal material cannot be well synthesized.

[0121] Comparative Example 10

[0122] The difference between the present comparative example and Example 1 is that the ligand used in step 2) of Example 1 is 4,4'-((9H-fluoren-9-yl)methylene)dipyrimidine, and the rest of the preparation process is the same as that of Example 1. A relatively clear solution is obtained, and basically no crystal is precipitated, and the quality is poor, so that the subsequent test cannot be carried out.

[0123] In summary, the present application provides, for the first time, a luminescent metal-organic framework crystal material capable of extremely sensitive luminescent enhancement detection of Hg 2+ in aqueous solution based on the fluorene ring ligand 4,4'-((2,7-di-tert-butyl-9H-fluoren-9-yl)methylene)dipyridine, a preparation method and product thereof. The synthesis route is simple and easy to control, the yield of the product can reach 42.3%, and it is suitable for industrialized production and popularization. Compared with the prior art, the crystal material can be used for luminescent enhancement detection of Hg 2+ for the first time, with extremely high sensitivity. The quenching constant for luminescent enhancement detection of Hg 2+ in aqueous solution is-2.12×10 4 M -1 , and the detection limit is as low as 3.51×10 -7 M, which has a broad application prospect.

[0124] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the present application, which should be covered in the scope of the present application.

Claims

1. A crystal material based on fluorene ring ligands, characterized in that: The chemical formula of the crystalline material is [Cd3(L)2(NDA)3(H2O)2·L]. n , Where L is a fluorene cyclic ligand, NDA 2- It is a 1,4-naphthoic acid anion ligand, where n is any value; The structural formula of the fluorene ring ligand is shown in formula (I): The crystal material has a triclinic crystal system; space group P-1; and unit cell parameters are as follows: α=109.942(4)°, β=93.638(3)°, γ=100.064(4)°, Z=2.

2. The method for preparing crystal materials based on fluorene ring ligands as described in claim 1, characterized in that: include, Cadmium acetate dihydrate, 4,4'-((2,7-di-tert-butyl-9H-fluorene-9-yl)methylene)dipyridine, and 1,4-naphthalenedicarboxylic acid were added to a mixed solvent of water and methanol and stirred to prepare a mixed solution. The mixture was placed in a sealed reactor and heated to room temperature. The product was then filtered, washed, and dried to obtain the luminescent metal-organic framework crystal material [Cd3(L)2(NDA)3(H2O)2·L]. n ; The molar ratio of cadmium acetate dihydrate, 4,4'-((2,7-di-tert-butyl-9H-fluorene-9-yl)methylene)dipyridine, and 1,4-naphthalenedicarboxylic acid is 1:0.5-2:0.5-2. The volume ratio of water to methanol in the mixed solvent is 1:0.5 to 2; The required volume of the mixed solvent of water and methanol for each 0.1 mmol of cadmium acetate dihydrate is 4–12 mL. The heating reaction is wherein the heating temperature is 120–180°C and the heating time is 48–72 h; The temperature is reduced to room temperature, wherein the cooling rate is 2–5 °C / h.

3. The fluorene ring ligand-based crystal material prepared by the method described in claim 2 exhibits enhanced luminescence detection of Hg. 2+ Applications in [the context of the text].

4. The fluorene ring ligand-based crystal material as described in claim 3 for enhanced luminescence detection of Hg 2+ The application of this technology is characterized by: The luminescence-enhanced detection of aqueous Hg based on fluorene ring ligand crystal materials 2+ The quenching constant is -2.12 × 10⁻⁶. 4 M -1 .

5. The fluorene ring ligand-based crystal material as described in claim 3 for enhanced luminescence detection of Hg 2+ The application of this technology is characterized by: The luminescence-enhanced detection of aqueous Hg based on fluorene ring ligand crystal materials 2+ The detection limit is 3.51 × 10⁻⁶. -7 M.

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