A cadmium coordination polymer and its preparation method and application

Abstract

The present invention relates to the field of metal complex molecular luminescent materials, in particular to a cadmium coordination polymer and its preparation method and application. The chemical formula of the cadmium coordination polymer is [Cd(TPPA)3(1,4-ndc)2] n TPPA is tris(4-(pyridin-4-yl)phenyl)amine and 1,4-ndc is 1,4-naphthalenedicarboxylic acid. The cadmium coordination polymer is obtained by hydrothermal synthesis in the presence of metal salt Cd(OAc)2·2H2O. In the coordination mode of the triphenylamine derivative ligand cadmium coordination polymer studied in the present invention, Cd 2+ As the central coordinating atom, it connects with three nitrogen atoms and four oxygen atoms to form a 7-coordinate complex with a stable structure. The material's synthesis process is simple, with readily available raw materials and high yield. This cadmium coordination polymer has the potential to be used as a photofunctional material. Its thermochromic properties also lend themselves to widespread applications in anti-counterfeiting and secure data storage.

Description

Technical Field

[0001] The invention relates to the technical field of metal coordination polymer molecular luminescent materials, in particular to a cadmium coordination polymer and a preparation method and application thereof. Background Art

[0002] Stimuli-responsive functional materials with specific properties have garnered significant attention in recent years. Various external stimuli, such as light, mechanical or pressure, steam, solvents, or temperature, have been widely used to induce changes in physical properties. Among these stimuli, changes in physical properties can be caused by a combination of multiple external stimuli. Thermal triggering is perhaps the most widespread external stimulus found in nature, with color change being the most notable phenomenon. These color changes are often collectively referred to as "chromophilia."

[0003] Temperature, as the most fundamental parameter, is considered an effective stimulus for triggering luminescence changes. This thermal, stimulus-responsive luminescence change is known as luminescence thermochromism. Theoretically, due to the Boltzmann distribution of excited-state electrons, the luminescence of all materials is temperature-dependent. As temperature increases, the rate of non-radiative transitions increases, resulting in a decrease in luminescence intensity. This patented material relates to the synthesis and application of luminescent thermochromic materials containing metal crystals.

[0004] Luminescent thermochromism is a reversible luminescent switch triggered by temperature stimulation. Current research focuses on the luminescence change of metal-containing complexes or coordination polymers in response to thermal stimulation. Metal ions play a vital role in determining the physical properties of the complexes or coordination polymers. Luminescent thermochromic materials emit light in response to temperature stimulation. Metal-containing complexes composed of inorganic and organic components have great advantages in constructing luminescent thermochromic materials: based on d 8 / d 10 The electronic structure of polynuclear metal clusters or coordination polymers has metal-philic interactions. Small changes in these interactions can lead to significant changes in their photophysical properties, resulting in unique intrinsic optical properties. In order to assemble stable, efficient, and easily visible luminescent thermochromic materials, it is essential to understand the relationship between molecular structure and its synthetic properties.

[0005] Thermochromic luminescence is characterized by a reversible change in emission wavelength with temperature. Hardt and colleagues first coined the term "fluorescent thermochromism" to refer to this temperature-dependent emission behavior. To date, significant efforts have been devoted to developing novel luminescent thermochromic materials. Furthermore, thermochromic thermometers have been investigated in the fields of biochemical activity, polymers, and nanoparticles. Several large families of metal-containing luminescent thermochromics have been identified for numerous applications in temperature-dependent luminescent probes and sensors.

[0006] While significant progress has been made in recent years in the development of metal-containing luminescent thermochromic crystalline materials, there is still considerable room for development. In the field of molecular luminescent materials, the design and synthesis of new luminescent coordination polymers holds significant research value and application prospects. This paper proposes a cadmium coordination polymer fluorescent material based on a triphenylamine derivative ligand. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a cadmium coordination polymer and a preparation method and application thereof. The preparation method of the present invention is simple and has a high yield. The cadmium coordination polymer prepared by the present invention, as a new molecular luminescent material, exhibits excellent performance in thermochromism and has broad potential application prospects.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a cadmium coordination polymer, the chemical formula of the cadmium coordination polymer is [Cd(TPPA)3(1,4-ndc)2]n, wherein: TPPA is tris(4-(pyridin-4-yl)phenyl)amine, 1,4-ndc is 1,4-naphthalene dicarboxylic acid, and n is any positive integer;

[0009] The cadmium coordination polymer belongs to the triclinic system, and the space group is The unit cell parameters are α=69.504(2)°, β=86.2350(10)°, γ=78.0320(10)°, Z=2,

[0010] A method for preparing the above-mentioned cadmium coordination polymer specifically comprises the following steps:

[0011] Step S1, Synthesis of Ligand TPPA: Pyridine-4-boric acid, tris(4-bromophenyl)amine, tetrakis(triphenylphosphine)palladium and potassium carbonate were added to a flask, and 1,4-dioxane and water as a solvent were added. The mixture was degassed three times in a vacuum state, and an inert gas was introduced under vacuum. The mixture was heated to reflux at 100° C. for 24 hours. The heating source was turned off and the mixture was cooled to room temperature. The reaction product was filtered through diatomaceous earth and the filtrate was removed under vacuum. The residue was redissolved in CH2Cl2 and washed with water several times. The obtained organic layer was dried over magnesium sulfate for 1 hour, and the organic solvent was concentrated. Ether was added to form a light yellow solid and purified by recrystallization from methanol / ethyl acetate to obtain tris(4-(pyridin-4-yl)phenyl)amine;

[0012] Step S2, synthesis of a cadmium coordination polymer: tris(4-(pyridin-4-yl)phenyl)amine, 1,4-naphthalenedicarboxylic acid, and Cd(OAc)2·2H2O prepared in step S1 were added to N,N-dimethylformamide, and the mixture was placed in a sealed kettle, which was then sealed in a programmed oven. The temperature was raised for 12 h, kept at a constant temperature for 72 h, and cooled for 24 h before the power was turned off to form [Cd(TPPA)3(1,4-ndc)2] n The crystals were collected by filtration, washed with DMF (N,N-dimethylformamide) and dried in air to obtain the finished product.

[0013] Furthermore, in step S1, the amount of pyridine-4-boric acid used is 34.3-35.2 mmol, the amount of tri(4-bromophenyl)amine used is 6.0-6.23 mmol, the amount of tetrakis(triphenylphosphine)palladium used is 0.29-0.33 mmol, the amount of potassium carbonate used is 49.3-50 mmol, the amount of 1,4-dioxane used is 140-150 ml, and the amount of water used is 7-10 ml.

[0014] Furthermore, in step S2, the molar ratio of tri(4-(pyridin-4-yl)phenyl)amine, 1,4-naphthalenedicarboxylic acid, and Cd(OAc)2·2H2O is 1:1:1.

[0015] Furthermore, in step S2, the amount of tri(4-(pyridin-4-yl)phenyl)amine used is 0.04-0.06 mmol, the amount of 1,4-naphthalenedicarboxylic acid used is 0.04-0.06 mmol, and the amount of Cd(OAc)2·2H2O used is 0.04-0.06 mmol.

[0016] Furthermore, in step S2, heating for 12 hours means heating from room temperature to 95-105°C for 12 hours, constant temperature heating for 72 hours means constant temperature heating at 95-105°C, and cooling for 24 hours means cooling from 95-105°C to room temperature for 24 hours.

[0017] An application of the cadmium coordination polymer as described above, wherein the cadmium coordination polymer has thermochromic properties and can be used in anti-counterfeiting and secure data storage.

[0018] The beneficial effects of the present invention are as follows: the present invention has reasonable design and simple operation; tri(4-(pyridin-4-yl)phenyl)amine and 1,4-naphthalenedicarboxylic acid are used as organic ligands, Cd(OAc)2·2H2O is used as a metal salt, N,N-dimethylformamide is used as a reaction solvent, and a hydrothermal method is adopted to cause a coordination reaction between the organic ligand and the cadmium salt to prepare a cadmium coordination polymer based on a triphenylamine derivative ligand; in the present invention, a cadmium coordination polymer based on a triphenylamine derivative ligand is obtained by controlling the raw material ratio of the reaction, selecting a suitable solvent, and controlling the reaction time; the cadmium coordination polymer has good structural stability when placed at room temperature for several months; in addition, the cadmium coordination polymer in the present invention has excellent fluorescence properties and can be used as a potential optical functional material; and the thermochromic properties thereof can be widely used in anti-counterfeiting and secure data storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and examples.

[0020] Figure 1 1a is a diagram of the crystal structure of the cadmium coordination polymer of the present invention, wherein 1a is a diagram of the single molecule crystal structure of the cadmium coordination polymer, and 1b is a diagram of the three-dimensional network structure of the cadmium coordination polymer;

[0021] Figure 2 is the infrared spectrum of the cadmium coordination polymer in Example 1;

[0022] Figure 3 is the thermogravimetric spectrum of the cadmium coordination polymer in Example 1;

[0023] Figure 4 is a normalized excitation-emission spectrum of the cadmium coordination polymer in Example 1;

[0024] Figure 5 is a temperature-variable fluorescence spectrum of the cadmium coordination polymer in Example 1;

[0025] Figure 6 is a temperature-variable fluorescence three-dimensional spectrum of the cadmium coordination polymer in Example 1;

[0026] Figure 7 is a thermochromic diagram of the cadmium coordination polymer in Example 1;

[0027] Figure 8 This is a bar graph of the quantum efficiency of the cadmium coordination polymer in Example 1. DETAILED DESCRIPTION

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and preferred embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0029] Example 1

[0030] A cadmium coordination polymer (D-1) having a chemical formula of [Cd(TPPA)3(1,4-ndc)2]n, wherein: TPPA is tris(4-(pyridin-4-yl)phenyl)amine, 1,4-ndc is 1,4-naphthalenedicarboxylic acid, and n is any positive integer;

[0031] The cadmium coordination polymer belongs to the triclinic system and the space group is The unit cell parameters are α=69.504(2)°, β=86.2350(10)°, γ=78.0320(10)°, Z=2,

[0032] The molecular structures of TPPA and 1,4-ndc are shown below:

[0033]

[0034] The cadmium coordination polymer (D-1) in this example has a crystal structure as shown in FIG. Figure 1 The crystallographic data of the cadmium coordination polymer (D-1) are shown in Table 1.

[0035] Table 1 Crystallographic data of cadmium coordination polymer (D-1)

[0036]

[0037] like Figure 1 As shown, in the coordination mode of the cadmium coordination polymer (D-1) in this embodiment, the cadmium coordination polymer based on the triphenylamine derivative ligand, that is, the cadmium coordination polymer (D-1) is based on Cd 2+ As the central coordination atom, it is connected to three N atoms and four O atoms. The three N atoms come from three triphenylamines, and the four O atoms come from the ligand 1,4-naphthalenedicarboxylic acid, forming a 7-coordinated complex. The crystal structure of the cadmium coordination polymer (D-1) was measured under low temperature conditions of 173K, and the structure of the crystal is stable when placed at room temperature.

[0038] A method for preparing a cadmium coordination polymer comprises the following steps:

[0039] Step S1, synthesis of ligand TPPA: pyridine-4-boric acid (34.7 mmol, 4.27 g), tris(4-bromophenyl)amine (6.2 mmol, 3.0 g), tetrakis(triphenylphosphine)palladium (0.31 mmol, 0.358 g), potassium carbonate (49.6 mmol, 6.85 g) were added to a 250 mL round-bottom flask. 1,4-Dioxane and 8 mL of water were added as solvents, and the mixture was cyclically degassed three times in a vacuum state. Under vacuum, an inert gas was introduced, and the mixture was heated under reflux at 100° C. for 24 hours. After the heating source was turned off and the mixture was cooled to room temperature, the reaction product was filtered through diatomaceous earth, and the filtrate was removed under vacuum. The residue was redissolved in CH2Cl2 (100 mL) and washed several times with 50 mL of water. The obtained organic layer was dried over magnesium sulfate for 1 hour, and the organic solvent was concentrated. Ether was added to form a light yellow solid, which was then purified by recrystallization from methanol / ethyl acetate to obtain TPPA with a yield of 70%;

[0040] Step S2, Synthesis of Cadmium Coordination Polymer (D-1): TPPA (24.0 mg, 0.050 mmol), 1,4-naphthalenedicarboxylic acid (10.8 mg, 0.05 mmol), and Cd(OAc)2·2H2O (13.4 mg, 0.05 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and the mixture was placed in a sealed autoclave, which was then sealed in a 100°C programmed oven. The temperature was raised for 12 h, heated for 72 h, and cooled for 24 h before the power was turned off to form [Cd(TPPA)3(1,4-ndc)2]. n The resulting rectangular single crystals were collected by filtration, washed with DMF solvent, and then air-dried to obtain a cadmium coordination polymer (D-1) based on a triphenylamine derivative ligand. Here, heating for 12 hours means heating from room temperature to 100°C for 12 hours and then heating at a constant temperature for 72 hours at 100°C. Cooling for 24 hours means cooling from 100°C to room temperature for 24 hours.

[0041] The fluorescence performance test of the cadmium coordination polymer (D-1) based on triphenylamine derivative ligand prepared in this example was carried out, and the test results were as follows: Figures 2 to 8 shown.

[0042] Depend on Figure 3 It can be seen that the cadmium coordination polymer (D-1) based on triphenylamine derivative ligand prepared in this example loses about 20% of its weight before 300° C., loses more weight after 300° C., and its crystal structure begins to collapse.

[0043] Depend on Figure 4It can be seen that the excitation wavelength of the cadmium coordination polymer (D-1) based on the triphenylamine derivative ligand prepared in this example is 365 nm, and the emission wavelength is 500 nm.

[0044] Depend on Figure 5 It can be seen that the cadmium coordination polymer (D-1) based on the triphenylamine derivative ligand prepared in this example exhibits a red shift of 70 nm as the temperature increases, indicating that the complex has stimulus-responsive behavior to temperature.

[0045] Depend on Figure 6 It can be seen that the fluorescence intensity of the cadmium coordination polymer (D-1) based on the triphenylamine derivative ligand prepared in this example substantially decreases as the temperature increases.

[0046] Depend on Figure 7 It can be seen that the cadmium coordination polymer (D-1) based on triphenylamine derivative ligand prepared in this example emits light from blue to green to yellow as the temperature rises at an excitation wavelength of 365 nm, and the luminescence phenomenon is consistent with the results of the fluorescence test.

[0047] Depend on Figure 8 It can be seen that the cadmium coordination polymer (D-1) based on the triphenylamine derivative ligand prepared in this example has different quantum efficiencies measured at different excitation wavelengths of 310 nm, 365 nm, 400 nm, and 450 nm, respectively. The highest quantum efficiency is 51.70% at an excitation wavelength of 310 nm.

[0048] Example 2

[0049] A method for preparing a cadmium coordination polymer comprises the following steps:

[0050] Step S1, Synthesis of Ligand TPPA: Pyridine-4-boric acid (34.3mmol, 4.22g), tris(4-bromophenyl)amine (6.0mmol, 2.9g), tetrakis(triphenylphosphine)palladium (0.29mmol, 0.33g), potassium carbonate (49.3mmol, 6.81g) were added to a 250mL round-bottom flask, and 140ml of 1,4-dioxane and 7mL of water were added as solvent. The mixture was degassed three times in a vacuum state to ensure that it was in a vacuum state. Inert gas was introduced and heated to reflux at 100°C for 23h. After turning off the heating source and cooling it to room temperature, the reaction product was filtered through diatomaceous earth, and the residue was redissolved in CH2Cl2 (100mL), washed several times with 50mL of water, and the obtained organic layer was dried over magnesium sulfate for 1h, and the organic solvent was concentrated. Ether was added to form a light yellow solid and purified by recrystallization from methanol / ethyl acetate with a yield of 70%;

[0051] Step S2, synthesis of cadmium coordination polymer: TPPA (19.04 mg, 0.040 mmol), 1,4-naphthalenedicarboxylic acid (8.64 mg, 0.04 mmol), and Cd(OAc)2·2H2O (10.72 mg, 0.04 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and the mixture was placed in a sealed autoclave, which was then sealed in a 100°C programmed oven. The temperature was raised for 12 h, heated for 72 h, and cooled for 24 h before the power was turned off to form [Cd(TPPA)3(1,4-ndc)2]. n The crystals were collected by filtration, washed with DMF solvent, and then dried in air to obtain a cadmium coordination polymer based on a triphenylamine derivative ligand.

[0052] Example 3

[0053] A method for preparing a cadmium coordination polymer comprises the following steps:

[0054] Step S1, synthesis of ligand TPPA: pyridine-4-boric acid (35.0 mmol, 4.30 g), tris(4-bromophenyl)amine (6.5 mmol, 3.14 g), tetrakis(triphenylphosphine)palladium (0.34 mmol, 0.392 g), potassium carbonate (49.8 mmol, 6.88 g) were added to a 250 mL round-bottom flask. 1,4-Dioxane and 9 mL of water were added as solvents, and the mixture was cyclically degassed three times in a vacuum state. Under vacuum, an inert gas was introduced and the mixture was heated under reflux at 100°C for 25 h. After the heating source was turned off and the mixture was cooled to room temperature, the reaction product was filtered through diatomaceous earth, and the residue was redissolved in CH2Cl2 (100 mL) and washed several times with 50 mL of water. The obtained organic layer was dried over magnesium sulfate for 1 h, and the organic solvent was concentrated. Ether was added to form a light yellow solid, which was purified by recrystallization from methanol / ethyl acetate with a yield of 70%.

[0055] Step S2, synthesis of cadmium coordination polymer: TPPA (28.56 mg, 0.060 mmol), 1,4-naphthalenedicarboxylic acid (12.96 mg, 0.06 mmol), and Cd(OAc)2·2H2O (16.08 mg, 0.06 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and the mixture was placed in a sealed autoclave, which was then sealed in a 100°C programmed oven. The temperature was raised for 12 h, heated for 72 h, and cooled for 24 h before the power was turned off to form [Cd(TPPA)3(1,4-ndc)2]. nThe crystals were collected by filtration, washed with DMF solvent, and then dried in air to obtain a cadmium coordination polymer based on a triphenylamine derivative ligand.

[0056] Example 4

[0057] A method for preparing a cadmium coordination polymer comprises the following steps:

[0058] Step S1, synthesis of ligand TPPA: pyridine-4-boric acid (34.5 mmol, 4.24 g), tris(4-bromophenyl)amine (6.15 mmol, 2.96 g), tetrakis(triphenylphosphine)palladium (0.305 mmol, 0.352 g), potassium carbonate (49.1 mmol, 6.78 g) were added to a 250 mL round-bottom flask. 1,4-Dioxane and 7 mL of water were added as solvents, and the mixture was cyclically degassed three times in a vacuum state. Under vacuum, an inert gas was introduced and the mixture was heated under reflux at 100° C. for 25 h. After the heating source was turned off and the mixture was cooled to room temperature, the reaction product was filtered through diatomaceous earth, and the residue was redissolved in CH2Cl2 (100 mL) and washed several times with 50 mL of water. The obtained organic layer was dried over magnesium sulfate for 1 h, and the organic solvent was concentrated. Ether was added to form a light yellow solid, which was purified by recrystallization from methanol / ethyl acetate with a yield of 70%.

[0059] Step S2, synthesis of cadmium coordination polymer: TPPA (21.42 mg, 0.045 mmol), 1,4-naphthalenedicarboxylic acid (9.72 mg, 0.045 mmol), and Cd(OAc)2·2H2O (12.06 mg, 0.045 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and the mixture was placed in a sealed autoclave, which was then sealed in a 100°C programmed oven. The temperature was raised for 12 h, heated for 72 h, and cooled for 24 h before the power was turned off to form [Cd(TPPA)3(1,4-ndc)2]. n The crystals were collected by filtration, washed with DMF solvent, and then dried in air to obtain a cadmium coordination polymer based on a triphenylamine derivative ligand.

[0060] Example 5

[0061] A method for preparing a cadmium coordination polymer comprises the following steps:

[0062] Step S1, synthesis of ligand TPPA: pyridine-4-boric acid (35.2 mmol, 4.32 g), tris(4-bromophenyl)amine (6.23 mmol, 3.00 g), tetrakis(triphenylphosphine)palladium (0.33 mmol, 0.381 g), potassium carbonate (50 mmol, 6.91 g) were added to a 250 mL round-bottom flask. 1,4-Dioxane and 10 mL of water were added as solvents, and the mixture was cyclically degassed three times in a vacuum state. Under vacuum, an inert gas was introduced and the mixture was heated under reflux at 100° C. for 25 h. The heating source was turned off and the mixture was cooled to room temperature. The reaction product was filtered through diatomaceous earth, and the residue was redissolved in CH2Cl2 (100 mL) and washed several times with 50 mL of water. The obtained organic layer was dried over magnesium sulfate for 1 h, and the organic solvent was concentrated. Ether was added to form a light yellow solid, which was purified by recrystallization from methanol / ethyl acetate with a yield of 70%.

[0063] Step S2, synthesis of cadmium coordination polymer: TPPA (26.18 mg, 0.055 mmol), 1,4-naphthalenedicarboxylic acid (11.88 mg, 0.055 mmol), and Cd(OAc)2·2H2O (14.74 mg, 0.055 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and the mixture was placed in a sealed autoclave, which was then sealed in a 100°C programmed oven. The temperature was raised for 12 h, heated for 72 h, and cooled for 24 h before the power was turned off to form [Cd(TPPA)3(1,4-ndc)2]. n The crystals were collected by filtration, washed with DMF solvent, and then dried in air to obtain a cadmium coordination polymer based on a triphenylamine derivative ligand.

[0064] Comparative Example 1

[0065] A method for preparing a cadmium coordination polymer comprises the following steps:

[0066] Step S1, synthesis of ligand TPPA: pyridine-4-boric acid (34.7 mmol, 4.27 g), tris(4-bromophenyl)amine (6.2 mmol, 3.0 g), tetrakis(triphenylphosphine)palladium (0.31 mmol, 0.358 g), potassium carbonate (49.6 mmol, 6.85 g) were added to a 250 mL round-bottom flask. 1,4-Dioxane and 8 mL of water were added as solvents, and the mixture was cyclically degassed three times in a vacuum state. Under vacuum, an inert gas was introduced, and the mixture was heated under reflux at 100° C. for 24 hours. The heating source was turned off and the mixture was cooled to room temperature. The reaction product was filtered through diatomaceous earth, and the filtrate was filtered out under vacuum. The residue was redissolved in CH2Cl2 (100 mL) and washed several times with 50 mL of water. The obtained organic layer was dried over magnesium sulfate for 1 hour, and the organic solvent was concentrated. Ether was added to form a light yellow solid, which was purified by recrystallization from methanol / ethyl acetate to obtain TPPA with a yield of 70%;

[0067] Step S2, synthesis of cadmium coordination polymer: TPPA (24.0 mg, 0.050 mmol), 1,4-naphthalene dicarboxylic acid (21.6 mg, 0.1 mmol) and Cd(OAc)2·2H2O (26.8 mg, 0.1 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and placed in a sealed autoclave, which was then sealed in a 100°C programmed oven. The temperature was raised for 12 h, heated for 72 h, and cooled for 24 h, and then the power was turned off to form a powder precipitate.

[0068] Comparative Example 2

[0069] A method for preparing a cadmium coordination polymer comprises the following steps:

[0070] Step S1, synthesis of ligand TPPA: pyridine-4-boric acid (34.7 mmol, 4.27 g), tris(4-bromophenyl)amine (6.2 mmol, 3.0 g), tetrakis(triphenylphosphine)palladium (0.31 mmol, 0.358 g), potassium carbonate (49.6 mmol, 6.85 g) were added to a 250 mL round-bottom flask. 1,4-Dioxane and 8 mL of water were added as solvents, and the mixture was cyclically degassed three times in a vacuum state. Under vacuum, an inert gas was introduced, and the mixture was heated under reflux at 100° C. for 24 hours. The heating source was turned off and the mixture was cooled to room temperature. The reaction product was filtered through diatomaceous earth, and the filtrate was filtered out under vacuum. The residue was redissolved in CH2Cl2 (100 mL) and washed several times with 50 mL of water. The obtained organic layer was dried over magnesium sulfate for 1 hour, and the organic solvent was concentrated. Ether was added to form a light yellow solid, which was purified by recrystallization from methanol / ethyl acetate to obtain TPPA with a yield of 70%;

[0071] Step S2, synthesis of cadmium coordination polymer: TPPA (24.0 mg, 0.050 mmol), 1,4-naphthalene dicarboxylic acid (10.8 mg, 0.05 mmol) and Cd(OAc)2·2H2O (13.4 mg, 0.05 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and placed in a sealed autoclave, which was then sealed in a 120°C programmed oven. After heating for 12 h, heating for 72 h, and cooling for 24 h, the power was turned off and no crystalline particles were found.

[0072] Comparative Example 3

[0073] A method for preparing a cadmium coordination polymer comprises the following steps:

[0074] Step S1, synthesis of ligand TPPA: pyridine-4-boric acid (34.7 mmol, 4.27 g), tris(4-bromophenyl)amine (6.2 mmol, 3.0 g), tetrakis(triphenylphosphine)palladium (0.31 mmol, 0.358 g), potassium carbonate (49.6 mmol, 6.85 g) were added to a 250 mL round-bottom flask. 1,4-Dioxane and 8 mL of water were added as solvents, and the mixture was cyclically degassed three times in a vacuum state. Under vacuum, an inert gas was introduced, and the mixture was heated under reflux at 100° C. for 24 hours. The heating source was turned off and the mixture was cooled to room temperature. The reaction product was filtered through diatomaceous earth, and the filtrate was filtered out under vacuum. The residue was redissolved in CH2Cl2 (100 mL) and washed several times with 50 mL of water. The obtained organic layer was dried over magnesium sulfate for 1 hour, and the organic solvent was concentrated. Ether was added to form a light yellow solid, which was purified by recrystallization from methanol / ethyl acetate to obtain TPPA with a yield of 70%;

[0075] Step S2, synthesis of cadmium coordination polymer: TPPA (48.0 mg, 0.1 mmol), 1,4-naphthalene dicarboxylic acid (10.8 mg, 0.05 mmol) and Cd(OAc)2·2H2O (13.4 mg, 0.05 mmol) prepared in step S1 were added to N,N-dimethylformamide (DMF, 10 mL), and placed in a sealed autoclave, and then placed in a 100°C programmed oven and sealed. After heating for 12 h, heating for 72 h, and cooling for 24 h, the power was turned off. No crystalline particles were found, and all the particles were solid.

[0076] In summary, the present invention has a reasonable design and is simple to operate. Tri(4-(pyridin-4-yl)phenyl)amine and 1,4-naphthalenedicarboxylic acid are used as organic ligands, Cd(OAc)2·2H2O is used as a metal salt, N,N-dimethylformamide is used as a reaction solvent, and a hydrothermal method is used to cause a coordination reaction between the organic ligand and the cadmium salt to prepare a cadmium coordination polymer based on a triphenylamine derivative ligand. In the present invention, a cadmium coordination polymer based on a triphenylamine derivative ligand is obtained by controlling the raw material ratio of the reaction, selecting a suitable solvent, and controlling the reaction time. The cadmium coordination polymer has good structural stability when placed at room temperature for several months. In addition, the cadmium coordination polymer in the present invention has excellent fluorescent properties and can be used as a potential optical functional material. At the same time, its thermochromic properties can be widely used in anti-counterfeiting and secure data storage.

[0077] The above description only describes specific embodiments of the present invention. Various examples do not limit the essential content of the present invention. After reading the description, ordinary technicians in the relevant technical field can make modifications or variations to the specific embodiments described above without departing from the essence and scope of the invention.

Claims

1. A cadmium coordination polymer, characterized in that: The chemical formula of the cadmium coordination polymer is [Cd(TPPA)3(1,4-ndc)2]n, wherein: TPPA is tris(4-(pyridin-4-yl)phenyl)amine, 1,4-ndc is 1,4-naphthalene dicarboxylic acid, and n is any positive integer; The cadmium coordination polymer belongs to the triclinic system, and the space group is The unit cell parameters are α=69.504(2)°, β=86.2350(10)°, γ=78.0320(10)°, Z=2, The cadmium coordination polymer is based on Cd 2+ As the central coordination atom, it is connected to three N atoms and four O atoms. The three N atoms come from three triphenylamines, and the four O atoms come from the ligand 1,4-naphthalenedicarboxylic acid, forming a 7-coordinated complex.

2. A method for preparing a cadmium coordination polymer as claimed in claim 1, characterized in that: The specific steps include: Step S1, Synthesis of Ligand TPPA: Pyridine-4-boric acid, tris(4-bromophenyl)amine, tetrakis(triphenylphosphine)palladium and potassium carbonate were added to a flask, and 1,4-dioxane and water as a solvent were added. The mixture was degassed three times in a vacuum state, and an inert gas was introduced under vacuum. The mixture was heated to reflux at 100° C. for 24 hours. The heating source was turned off and the mixture was cooled to room temperature. The reaction product was filtered through diatomaceous earth and the filtrate was removed under vacuum. The residue was redissolved in CH2Cl2 and washed with water several times. The obtained organic layer was dried over magnesium sulfate for 1 hour, and the organic solvent was concentrated. Ether was added to form a light yellow solid and purified by recrystallization from methanol / ethyl acetate to obtain tris(4-(pyridin-4-yl)phenyl)amine; Step S2, synthesis of a cadmium coordination polymer: tris(4-(pyridin-4-yl)phenyl)amine, 1,4-naphthalenedicarboxylic acid, and Cd(OAc)2·2H2O prepared in step S1 were added to N,N-dimethylformamide, and the mixture was placed in a sealed kettle, which was then sealed in a programmed oven. The temperature was raised for 12 h, kept at a constant temperature for 72 h, and cooled for 24 h before the power was turned off to form [Cd(TPPA)3(1,4-ndc)2] n The crystals were collected by filtration, washed with DMF and dried in air to obtain the finished product.

3. The method for preparing a cadmium coordination polymer according to claim 2, wherein: In step S1, the amount of pyridine-4-boric acid used is 34.3-35.2 mmol, the amount of tri(4-bromophenyl)amine used is 6.0-6.23 mmol, the amount of tetrakis(triphenylphosphine)palladium used is 0.29-0.33 mmol, the amount of potassium carbonate used is 49.3-50 mmol, the amount of 1,4-dioxane used is 140-150 ml, and the amount of water used is 7-10 ml.

4. The method for preparing a cadmium coordination polymer according to claim 2, wherein: In step S2, the molar ratio of tri(4-(pyridin-4-yl)phenyl)amine, 1,4-naphthalenedicarboxylic acid, and Cd(OAc)2·2H2O is 1:1:

1.

5. The method for preparing a cadmium coordination polymer according to claim 4, wherein: In step S2, the amount of tri(4-(pyridin-4-yl)phenyl)amine used is 0.04-0.06 mmol, the amount of 1,4-naphthalenedicarboxylic acid used is 0.04-0.06 mmol, and the amount of Cd(OAc)2·2H2O used is 0.04-0.06 mmol.

6. The method for preparing a cadmium coordination polymer according to claim 2, wherein: In step S2, heating for 12 hours means heating from room temperature to 95-105° C. for 12 hours and heating at a constant temperature for 72 hours at a temperature of 95-105° C., and cooling for 24 hours means cooling from 95-105° C. to room temperature for 24 hours.

7. A use of the cadmium coordination polymer according to claim 1, characterized in that: The cadmium coordination polymer is used in anti-counterfeiting and secure data storage.

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