Preparation method and application of novel cadmium complex

Abstract

The invention discloses a preparation method and application of a novel cadmium complex, and the preparation method comprises the following steps: adding cadmium nitrate, 2, 5-bis (pyridine-4-yl) thiazolo [5, 4-d] thiazole (DPTzTz) and azobenzene 4, 4-dicarboxylic acid (4, 4-H2Azo) into a mixed solvent of N, N-dimethylformamide / H2O, carrying out ultrasonic treatment, and heating to obtain an orange prismatic crystal complex {[Cd (NO3) (4, 4 '-Azo) 0.5 (DPTzTz)]. DMF} n, the obtained orange prism-shaped crystal complex is activated and purified, a novel cadmium complex with higher performance can be obtained, and the complex can serve as an excellent reaction catalyst for catalyzing a carbon dioxide cycloaddition reaction and can also serve as a radioactive iodine trapping agent; the use amount of the novel cadmium complex in the carbon dioxide cycloaddition reaction is 1 mol%, the reaction conditions are mild and easy to operate, and expanded production of the reaction is facilitated; the raw materials in all the reaction processes are easy to obtain, reaction conditions are mild, operation is easy, energy consumption is low, and environment friendliness is achieved.

Description

Technical Field

[0001] The patent of this invention belongs to the field of inorganic chemistry technology, and specifically relates to a new method for preparing cadmium complexes and their application. Background Art

[0002] Complexes, as ordered porous materials, have attracted widespread attention in academia and industry over the past few decades. In recent years, the design and synthesis of high-performance, multifunctional complexes has become a research hotspot. To achieve the desired properties, the most common and effective approach is to seek breakthrough organic ligands. Ligand structures are numerous, and the complexes can be engineered to achieve structural diversity through the design of functional groups and substituents, resulting in complexes with superior properties. Azo and its derivatives have highly conjugated π-electron systems and exhibit excellent photoresponsive properties, providing photoresponsive structures for complexes. Furthermore, since the basic N=N group enhances the interaction with the acidic CO2 molecule, the azo group helps strengthen the interaction between the complex and CO2. Thiazolo[5,4-d]thiazole (TzTz) exhibits excellent optical and electrical properties due to its large π-conjugated heterocycle. When ligands containing this functional group are arranged parallel within the complex, inter-space charge transfer (IVCT) occurs between the coplanar portions, effectively promoting the conversion of light energy into chemical energy. Therefore, complexes prepared from ligands containing TzTz moieties are often used in applications such as fluorescence sensing, electrochromism, and catalysis. It is of interest to develop materials with excellent multifunctionality by introducing TzTz and N=N groups into complexes via a mixed ligand strategy.

[0003] Therefore, in order to obtain a high-performance, multifunctional complex with cheap and readily available reaction raw materials, high reaction selectivity, mild reaction conditions and environmental friendliness, the inventors developed a new method for preparing cadmium complexes and their applications. Summary of the Invention

[0004] To address the above-mentioned issues, the present invention provides a method for preparing a novel cadmium complex and its application. The complex exhibits excellent stability and has the ability to capture radioactive iodine in both gaseous and aqueous solutions. This has important research value and application implications for the handling and immobilization of radioactive iodine. Furthermore, the novel cadmium complex possesses dual functionality and can also serve as a novel catalyst for the cycloaddition of carbon dioxide. The development of a method with readily available, inexpensive raw materials, high reaction selectivity, mild reaction conditions, and environmental friendliness would be of great research significance and application value.

[0005] In order to achieve the above technical effects, the present invention provides a novel method for preparing a cadmium complex, which specifically comprises the following steps: S1. Cadmium nitrate, 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTzTz), azobenzene 4,4´-dicarboxylic acid (4,4´- H2Azo), and concentrated nitric acid are added to a mixed solvent of N,N-dimethylformamide / H2O, with the ratio of cadmium nitrate to solvent ranging from 0.1 to 0.4 mmol / mL. Ultrasonicate for 30 minutes and heat at 99-121°C for 48 hours to obtain an orange prismatic crystal complex. Furthermore, the molar ratio of cadmium nitrate, 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTzTz), azobenzene 4,4'-dicarboxylic acid (4,4'- H2Azo), and concentrated nitric acid in S1 is 2:2:1:0.13, and the molar ratio can be adjusted within the range of ±10%; Furthermore, the volume ratio of the N,N-dimethylformamide / H2O mixed solvent in S1 is 5:1, and the volume ratio can be adjusted within the range of ±10%; Furthermore, the ratio of cadmium nitrate to solvent in S1 is in the range of 0.1-0.4 mmol / mL and can be adjusted within the range of ±10%; S2. Activating and purifying the orange prismatic crystal complex obtained in S1 to obtain a novel cadmium complex, the specific steps of which include: S201, washing the orange prismatic crystalline complex obtained in S1 with an appropriate amount of DMF and drying at 60°C for 20 hours; S202, soaking the dried complex in ultra-dry dichloromethane for three days, replacing the solvent every 12 hours; S203. Dry the complex at 50° C. under vacuum conditions to completely remove the solvent molecules and obtain an activated new cadmium complex.

[0006] Based on the above technical solution, the inventors also provide a novel cadmium complex preparation method to prepare a novel cadmium complex {[Cd(NO3)(4,4′-Azo) 0.5 (DPTzTz)]·DMF} n .

[0007] Based on the above technical solution, the inventors also provide a new type of cadmium complex for use in iodine capture.

[0008] Based on the above technical solution, the inventors also provide a novel cadmium complex for use in catalyzing carbon dioxide cycloaddition.

[0009] The beneficial effects of the present invention are: 1. Synthesize a novel cadmium complex that can serve as an excellent catalyst for carbon dioxide cycloaddition reactions and can also serve as a scavenger for radioactive iodine. 2. The use amount of the new cadmium complex in the carbon dioxide cycloaddition reaction is 1 mol%, and the reaction conditions are mild and easy to operate, which is conducive to the scale-up production of the reaction; 3. All the raw materials in the reaction process are easily available, the reaction conditions are mild, easy to operate, low energy consumption and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts: Figure 1 (a) is the coordination of cadmium ions in the cadmium complex of the present invention, and (b) is the Cd-Cd distance in the [Cd2(COO)2] unit and the π-π interaction between the tztz ligands; Figure 2 (a) is a 2D sheet structure constructed along the ac plane of the present invention, and (b) is a 1D channel of the complex along the crystallographic c axis (the solvent molecules and the coordinated NO3 are omitted for clarity). - ); Figure 3 The PXRD of the complex of the present invention after simulation, experiment and activation; Figure 4 is the thermogravimetric analysis curve of the cadmium complex of the present invention; Figure 5 This is the PXRD of the cadmium complex of the present invention after being immersed in different solvents for 40 hours; Figure 6 (a) is the UV-visible spectrum of the present invention capturing iodine in a cyclohexane solution over time, and (b) is the change in iodine capture rate in the cyclohexane solution; Figure 7 The recoverability of the iodine captured by the cadmium complex of the present invention in cyclohexane solution; Figure 8 This is the process of the cadmium complex of the present invention capturing gaseous iodine; Figure 9 is the PXRD of the cadmium complex of the present invention before and after capturing iodine; Figure 10 is the yield of various cyclic carbonates produced by the CO2 cycloaddition reaction catalyzed by the cadmium complex of the present invention; Figure 11 (a) is the recovery rate of the cadmium complex of the present invention after five catalytic cycles, and (b) is the PXRD of the cadmium complex after five catalytic cycles. DETAILED DESCRIPTION

[0011] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. Example 1

[0012] Based on the existing technology, in order to obtain a high-performance, multifunctional complex with cheap and readily available reaction raw materials, high reaction selectivity, mild reaction conditions, and environmental friendliness, the inventors provide a new method for preparing a cadmium complex, which specifically comprises the following steps: S1. Cadmium nitrate, 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTzTz), azobenzene 4,4´-dicarboxylic acid (4,4´- H2Azo), and concentrated nitric acid are added to a mixed solvent of N,N-dimethylformamide / H2O, with the ratio of cadmium nitrate to solvent ranging from 0.1 to 0.4 mmol / mL. Ultrasonicate for 30 minutes and heat at 99-121°C for 48 hours to obtain an orange prismatic crystal complex. Furthermore, the molar ratio of cadmium nitrate, 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTzTz), azobenzene 4,4'-dicarboxylic acid (4,4'- H2Azo), and concentrated nitric acid in S1 is 2:2:1:0.13, and the molar ratio can be adjusted within the range of ±10%; Furthermore, the volume ratio of the N,N-dimethylformamide / H2O mixed solvent in S1 is 5:1, and the volume ratio can be adjusted within the range of ±10%; Furthermore, the ratio of cadmium nitrate to solvent in S1 is in the range of 0.1-0.4 mmol / mL and can be adjusted within the range of ±10%; S2. Activating and purifying the orange prismatic crystal complex obtained in S1 to obtain a novel cadmium complex, the specific steps of which include: S201, washing the orange prismatic crystalline complex obtained in S1 with an appropriate amount of DMF and drying at 60°C for 20 hours; S202, soaking the dried complex in ultra-dry dichloromethane for three days, replacing the solvent every 12 hours; S203. Dry the complex at 50° C. under vacuum conditions to completely remove the solvent molecules and obtain an activated new cadmium complex.

[0013] Based on the above technical solution, the inventors also provide a novel cadmium complex preparation method to prepare a novel cadmium complex {[Cd(NO3)(4,4′-Azo) 0.5 (DPTzTz)]·DMF} n .

[0014] In the above technical solution, the inventors conducted a phase purity analysis of the orange prismatic crystalline cadmium complex, specifically including the following: First, an orange prismatic crystalline cadmium complex was prepared as described in S1 above, and then single crystal X-ray analysis of the cadmium complex crystal was performed (e.g. Figure 1 a) The crystals were found to belong to the C2 / c space group, and each structural unit contained a Cd(II) ion, half of a completely deprotonated 4,4'-Azo 2- anion, a DPTzTz ligand, a coordinated NO3 - and a free DMF molecule. The Cd(II) center has a six-coordinated distorted octahedral geometry with four oxygen atoms attached at the equatorial position (O1 and O2 belong to two 4,4'-Azo 2- Ligand NO3 - , O5, and O4#2), axially connecting the two nitrogen atoms (N4 and N1#3) of the two DPTz ligands. In the 4,4´-H2Azo ligand, the two carboxylic acid groups use the same bidentate bridging mode to connect the two Cd(II) centers, forming a binuclear [Cd2(COO)2] unit with a Cd-Cd distance of 4.003Å. The π-π distance between the phenyl rings of adjacent DPTzTz ligands is 3.969Å, which helps mediate electrons (such as Figure 1 b) The [Cd2(COO)2] unit consists of 4,4'-Azo 2- and DPTzTz are alternately connected to form a mixed ligand 2D sheet structure on the ac plane (e.g. Figure 2 a). Adjacent 2D layers are further connected together by DPTzTz to form a 3D double-pillar layered framework. This complex has a large 1D channel in the c-axis direction with a pore size of 13.496Å × 13.496Å (based on Cd-Cd separation, as shown in Figure 2). Figure 2 b) The inner walls of the pores are exposed with Cd(II) vacancies, N=N, and TzTz. Notably, according to PLATON calculations, the free volume of the framework remains 32.7% (equivalent to 1967.3 Å3 when the solvent is removed).

[0015] To improve the performance of the cadmium complex, as described in S2 above, it can be activated. The specific activation process is as follows: 1. Wash the cadmium complex with an appropriate amount of DMF and dry it at 60°C for 20 hours. 2. Soak the dried complex in ultra-dry dichloromethane for three days, replacing the solvent every 12 hours. 3. Dry the complex at 50°C under vacuum to completely remove the solvent molecules.

[0016] The structure of the synthesized cadmium complex was characterized. Figure 3The red curve in the figure is the simulated powder X-ray diffraction spectrum of the cadmium complex, the green curve is the powder X-ray diffraction spectrum of the prepared cadmium complex, and the blue curve is the powder X-ray diffraction spectrum of the activated cadmium complex. Comparing the red and green spectra, no obvious impurity peaks appear, indicating that the complex has excellent phase purity. Comparing the green and blue spectra, no significant changes are found, indicating that the complex framework remains intact after activation and the sample's crystallinity is maintained. The activated complex is a potential ideal material for applications such as adsorption / separation, catalysis, and fluorescence recognition.

[0017] In the above technical solution, the inventors also conducted a stability analysis of the orange prismatic crystalline cadmium complex, as follows: In order to investigate the thermal stability of the cadmium complex, thermogravimetric analysis was performed. The results are shown in Figure 4 . As shown in the figure, the first weight loss occurs between 51 and 80 ° C, and the weight loss value is equivalent to the loss of one DMF solvent molecule (experimental value is about 89.5%, calculated value is 89.2%). From 80 to 201 ° C, the weight is almost not reduced. After further heating, a sudden weight loss occurs, which is attributed to the decomposition of the skeleton. The final residue after thermal decomposition can be inferred to be CdO (experimental value is 22.1%, calculated value is 18.9%). When the temperature is below 200 ° C, the thermogravimetric analysis curve of the activated complex does not decrease, indicating that the crystal structure is stable within this temperature range. This also shows that the activation only removes the solvent in the pores of the complex and does not affect the structure and composition of the complex.

[0018] The crystal samples of the cadmium complex were immersed in different organic solvents for 40 h, including dichloromethane (CH2Cl2), methanol (CH3OH), acetonitrile (CH3CN), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Figure 5 As shown, the complex recovered from the solvent has consistent PXRD data with the unsoaked complex, which indicates that the cadmium complex has good solvent stability. Example 1

[0019] Based on the above technical solution, the inventors investigated the capture performance of the new cadmium complex for radioactive iodine, thereby obtaining an application of the new cadmium complex in iodine capture. The specific process of the investigation is as follows: The activated complex was immersed in 5 mL of 320 mg / L iodocyclohexane solution. The dark purple solution gradually faded to light pink or even colorless, while the sample color changed from orange to almost black (e.g. Figure 6a), indicating that the cadmium complex can effectively capture iodine. For 5mg, 10mg, and 15mg of the complex, the capture rates were 84.6%, 98.9%, and 99.1%, respectively, indicating that 10mg is the optimal dose. The complex rapidly captures iodine in the initial stage, capturing approximately 58.8% of the iodine within 8 hours. After 48 hours, the capture rate gradually slowed until reaching equilibrium (e.g. Figure 6 b). The optimal iodine capture rate and capture amount reached 97.5% and 737.2 mg·g, respectively. -1 The iodine captured by the complex can be released into ethanol, and the iodine capture process is reversible. After six I2 capture-release cycles, the iodine capture efficiency of the complex can still reach more than 71.7% (such as Figure 7 ).

[0020] 100 mg of the activated complex and solid iodine were sealed in a container and evaluated for its ability to capture volatile iodine at 75°C. The results showed that the complex rapidly captured volatile iodine within the first three hours, then gradually decreased. Saturation was reached after approximately 13 hours, with a maximum capture of 680.1 mg·g -1 , which is comparable to the capture amount in cyclohexane solution. The capture efficiency reached 69% in the first 35 minutes. After 150 minutes, the absorbance basically stopped changing, and the capture efficiency was 88.2% (such as Figure 8 ).

[0021] like Figure 9 As shown in Figure 2, the PXRD patterns of the cadmium complex before and after iodine capture are essentially identical, with only some peaks weakening and broadening. This indicates that the skeleton of the cadmium complex is well maintained during the iodine capture and release process. Example 2

[0022] Based on the above technical solution, the inventors investigated the application performance of the new cadmium complex in catalyzing the cycloaddition reaction of epoxide and carbon dioxide, thereby obtaining an application of the new cadmium complex in catalyzing the cycloaddition reaction of carbon dioxide. The specific process of the investigation is as follows: Cadmium complexes were used to catalyze the cycloaddition reaction of carbon dioxide and epoxides. The experimental scheme was optimized using propylene oxide as an example. The results showed that under the reaction conditions of 50°C and 12h, when tetrabutylammonium bromide (TATB) was used as a catalyst, the CO2 cycloaddition conversion rate was 6%; when cadmium complexes were used as catalysts, the conversion rate could be increased to 12%; and when cadmium complexes (1 mol%) and tetrabutylammonium bromide (TATB) were used as co-catalysts, the conversion rate could be as high as 98%. In order to further study the catalytic versatility of cadmium complexes, different epoxide substrates were used to carry out CO2 cycloaddition reactions. The corresponding results (such as Figure 10) showed that the cadmium complex exhibited high efficiency in the CO2 cycloaddition reaction. Recyclability is a necessary prerequisite for the large-scale application of the catalyst. Therefore, a cyclic catalytic experiment was carried out. Using propylene oxide as a representative substrate, after five cycles under the above optimal conditions, the conversion rate did not decrease significantly (such as Figure 11 (a) shows that the cadmium complex has good reusability as a catalyst. The PXRD pattern of the recovered complex has basically no change, indicating that the structure of the cadmium complex remains intact after recycling (e.g. Figure 11 (b)).

[0023] Conclusion: The cadmium complex prepared by the present invention has the effect of capturing radioactive iodine in both gaseous and solution states. 10 mg of cadmium complex can capture 5 mL, 320 mg·L -1 The capture efficiency of iodine in cyclohexane solution was 58.8% after 8 hours and 98.9% after 48 hours; the maximum capture amount was 737.2 mg·g -1 The capture rate was 97.5%; after 6 cycles, the capture rate was still higher than 71.7%. The maximum capture capacity of the cadmium complex for gaseous iodine was 680.1 mg·g -1 The capture rate was 69% at 35 minutes and 88.2% at 150 minutes. Furthermore, the cadmium complex catalyzed the cycloaddition reaction of carbon dioxide and epoxides. When 1 mol% of the complex was added and synergistically catalyzed with tetrabutylammonium bromide, the yield reached over 98%. Even after five cycles, the yield did not decrease significantly.

[0024] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0025] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A novel method for preparing a cadmium complex, characterized in that: The specific steps include: S1. Cadmium nitrate, 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTzTz), azobenzene 4,4´-dicarboxylic acid (4,4´- H2Azo), and concentrated nitric acid are added to a mixed solvent of N,N-dimethylformamide / H2O, with the ratio of cadmium nitrate to solvent ranging from 0.1 to 0.4 mmol / mL. Ultrasonicate for 30 minutes and heat at 99-121°C for 48 hours to obtain an orange prismatic crystal complex. S2. Activating and purifying the orange prismatic crystal complex obtained in S1 to obtain a novel cadmium complex, the specific steps of which include: S201, washing the orange prismatic crystalline complex obtained in S1 with an appropriate amount of DMF and drying at 60°C for 20 hours; S202, soaking the dried complex in ultra-dry dichloromethane for three days, replacing the solvent every 12 hours; S203. Dry the complex at 50° C. under vacuum conditions to completely remove the solvent molecules and obtain an activated new cadmium complex.

2. A method for preparing a novel cadmium complex according to claim 1, characterized in that: The molar ratio of cadmium nitrate, 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTzTz), azobenzene 4,4'-dicarboxylic acid (4,4'-H2Azo), and concentrated nitric acid in S1 is 2:2:1:0.13, and the molar ratio can be adjusted within the range of ±10%.

3. The method for preparing a novel cadmium complex according to claim 1, wherein: The volume ratio of the N,N-dimethylformamide / H2O mixed solvent in S1 is 5:1, and the volume ratio can be adjusted within the range of ±10%.

4. The method for preparing a novel cadmium complex according to claim 1, wherein: The ratio of cadmium nitrate to solvent in the S1 is in the range of 0.1-0.4 mmol / mL and can be adjusted within the range of ±10%.

5. The novel cadmium complex {[Cd(NO3)(4,4′-Azo) 0.5 (DPTzTz)]·DMF} n .

6. Use of the novel cadmium complex according to claim 5 in iodine capture.

7. Use of the novel cadmium complex according to claim 5 in catalyzing carbon dioxide cycloaddition.

Images