Photo-thermal conversion crystal material as well as preparation method and application thereof

Abstract

The invention relates to a photothermal conversion crystal material and a preparation method and application thereof, a tetrathiafulvalene structural unit has a 10-center 14-electron large conjugated unit pi 1014, when the tetrathiafulvalene unit is connected with four pyridine groups, a larger conjugated unit is formed, and a specific conjugated system has specific influence on the photothermal conversion performance of the crystal material; the positions of carboxyl groups in aromatic rings are different, and the steric configurations of the ligands are different, so that the composition, structure and steric configuration of the coordination polymer of the ligands and metal ions are different, and the coordination polymer has different physical and chemical properties and different applications; under the specific preparation method and crystallization conditions, after acid radicals of 2, 2 '-bithiophene-5, 5'-dicarboxylic acid and zinc ions are subjected to a coordination reaction, the formed MOF crystal material has specific composition, structure and spatial configuration, so that the prepared MOF crystal material has specific photothermal conversion performance.

Description

Technical Field

[0001] The present invention relates to the technical field of photothermal conversion materials, and in particular to a photothermal conversion crystal material and a preparation method and application thereof. Background Art

[0002] Photothermal conversion involves converting solar energy into thermal energy, which is then used to achieve desired goals, such as water purification, desalination, power generation, catalytic conversion, and sterilization. Therefore, solar thermal conversion can serve as a supplement to photovoltaic conversion and is also considered an important clean energy utilization technology.

[0003] Metal-organic frameworks (MOFs) are a new class of inorganic-organic composites that have attracted widespread attention due to their ability to precisely control composition, structure, and physicochemical properties at the atomic and molecular scales. MOFs are typically designed through simple solvothermal synthesis methods involving metal ions and organic ligands. Donor-acceptor (DA) interactions between electron donors (donors) and acceptors (acceptors) enable the stacking and assembly of D and A components, as well as tunable electron-related processes such as charge transfer / separation and energy transfer. In recent years, some MOFs have been used to load photothermal materials to enhance performance through synergistic effects.

[0004] Tetrathiafulvalene (TTF) is a well-characterized electron donor. By controlling the potential, it can undergo a stepwise reversible oxidation reaction to generate monovalent or divalent cations. Therefore, TTF can exist as a neutral molecule, a radical cation, and a divalent cation. Due to its unique physicochemical properties, including electrochemical behavior, assembly characteristics, and ease of derivatization, scientists have synthesized a variety of TTF derivatives with extended conjugated π groups to improve their electron-donating ability and expand research in related fields. These derivatives not only lead to stable oxidation states and the formation of polycationic bodies, but also reduce the energy gaps of the HOMO and LUMO orbitals, enhancing electron-donating capacity. Numerous experimental results have demonstrated that TTF derivatives can exhibit varying degrees of photothermal conversion performance by tailoring their structure using groups such as pyridyl, carboxyl, benzocyano, thiophene, or furan, through ionic coordination with transition metals. Therefore, the design and construction of MOFs using TTF derivatives as primary templates is often achieved by grafting different conjugated groups onto their primary active sites.

[0005] At present, how to obtain photothermal conversion materials with simple preparation methods and good stability needs further research. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a photothermal conversion crystal material with high stability and performance in response to the current status of the existing technology.

[0007] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned photothermal conversion crystal material in view of the current status of the existing technology. The preparation method is simple and easy to implement.

[0008] The third technical problem to be solved by the present invention is to provide an application of the above-mentioned photothermal conversion crystal material in view of the current status of the existing technology.

[0009] The technical solution adopted by the present invention to solve at least one of the above technical problems is: A photothermal conversion crystal material, the photothermal conversion crystal material belongs to the monoclinic system, the space group is P21 (no.4), the molecular formula is C 46 H 24 N4O8S8Zn2, molecular weight is 1154.4, unit cell parameters are a=7.0530(13) Å, b=20.5202(14) Å, c=16.4849(8) Å, α=γ= 90°, β=97.1°.

[0010] In the present invention, the asymmetric unit of the photothermal conversion crystal material includes a p-TTF(py)4, a 2,2'-bithiophene-5,5'-dicarboxylic acid and a Zn 2+ ; Zn 2+ It adopts a four-coordination mode, with two oxygen atoms coming from two different 2,2'-bithiophene-5,5'-dicarboxylate groups and two nitrogen atoms coming from two different p-TTF(py)4 ligands. The five atoms together form a secondary building unit with a tetrahedral structure.

[0011] Preferably, the secondary building units are connected in different directions via two ligands to form a three-dimensional network structure having four different pores.

[0012] Preferably, the ligands are p-TTF(py)4 and 2,2'-bithiophene-5,5'-dicarboxylic acid, wherein the structural formula of 2,2'-bithiophene-5,5'-dicarboxylic acid is as follows: ; p-TTF(py)4 is 3,4,5,6-tetrakis(4-pyridyl)tetrathiafulvalenoate, with the following structural formula: .

[0013] A method for preparing a photothermal conversion crystal material comprises the following steps: Weigh 2,2'-bithiophene-5,5'-dicarboxylic acid and dissolve it in N-dimethylformamide to obtain a DMF solution of 2,2'-bithiophene-5,5'-dicarboxylic acid; Weigh Zn(NO3)2·6H2O and p-TTF(py)4 and dissolve them in a mixed solution of ethanol and H2O to obtain a solution of zinc nitrate and p-TTF(py)4; The above two solutions were mixed, and a dilute HNO3 (2.0 mol / L) solution was added dropwise. After ultrasonic vibration treatment, the mixture was heated in a 90°C oven for reaction. After the reaction, the temperature was cooled at a rate of 5°C / h. The product was filtered out at room temperature, washed with ethanol, and dried at 60°C to obtain black block crystals, which are the photothermal conversion crystal materials.

[0014] Preferably, the molar ratio of the 2,2'-bithiophene-5,5'-dicarboxylic acid, zinc nitrate, and p-TTF(py)4 substances is 2:3.5:1.

[0015] Preferably, the substances or solvents involved in the reaction are chemically pure.

[0016] An application of a photothermal conversion crystal material for use in photothermal conversion equipment.

[0017] Compared with the prior art, the advantages of the present invention are that, during the construction of a metal-organic framework, the 4-pyridyl derivative in the TTF(py)4 ligand and the related geometric configurations, such as the dihedral angles between the four pyridyl groups and the TTF core, are more conducive to the formation of a coordination polymer during coordination-driven self-assembly. The four pyridyl groups can partially or completely coordinate with the metal ions, facilitating the formation of a stable framework structure. Specifically: The tetrathiafulvalene structural unit of the present invention has a 10-center 14-electron large conjugated unit π 10 14 When the tetrathiafulvalene unit is connected to four pyridine groups to form a larger conjugated unit, the specific conjugated system has a specific effect on the photothermal conversion performance of the crystal material. In addition, the different positions of the carboxyl group on the aromatic ring and the different spatial configurations of the ligands lead to different compositions, structures and spatial configurations of the coordination polymers between the ligands and the metal ions, which in turn give the coordination polymers different physical and chemical properties and applications. Under specific preparation methods and crystallization conditions, the metal organic framework crystal material formed after the coordination reaction of the acid radical of 2,2'-bithiophene-5,5'-dicarboxylic acid with zinc ions has a specific composition, structure and spatial configuration, which makes the prepared MOF crystal material have unique photothermal conversion performance. The crystal material prepared by the present invention at room temperature has a thermal conductivity of 1.6 W·cm -2Under the irradiation of high-power near-infrared laser, the temperature rises to 200°C in 5 seconds and can reach a maximum temperature of 240°C; under the irradiation of 808 nm laser (0.4 W·cm −2 ) The change in surface temperature under continuous irradiation of repeated laser on / off cycles was tested under light. The temperature of the MOF crystal material rapidly rose from room temperature to 85°C. After 5 cycles, the photothermal performance of the crystal material did not decay. The same test was performed again three weeks later. The crystal material was still stable and the photothermal performance did not decrease. The results proved that the MOF photothermal conversion performance is stable and can be reused.

[0018] Therefore, the MOF crystal material prepared by the present invention exhibits good photothermal conversion performance and good stability, and has broad application prospects as a photothermal conversion material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the coordination environment of zinc ions in the MOF crystal material of the present invention; Figure 2 It is a three-dimensional network structure of the MOF crystal material of the present invention; Figure 3 The pore morphology along the a-axis of the MOF crystal material of the present invention; Figure 4 is the XRD spectrum of the MOF crystal material of the present invention; Figure 5 This is the thermogravimetric analysis spectrum of the MOF crystal material of the present invention; Figure 6 The MOF crystal material of the present invention is subjected to a power of 1.6 W·cm -2 Photothermal conversion spectrum on laser; Figure 7 The MOF crystal material of the present invention is subjected to a power of 0.4 W·cm -2 Photothermal cycle curve on the laser. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0021] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Example 1:

[0022] 2.5 mg (0.0098 mmol) of 2,2'-bithiophene-5,5'-dicarboxylic acid was weighed on a weighing balance and dissolved in 0.75 mL of N-N-dimethylformamide (DMF) to obtain a DMF solution of 2,2'-bithiophene-5,5'-dicarboxylic acid. 5 mg (0.017 mmol) of Zn(NO3)2·6H2O and 2.5 mg (0.0049 mmol) of p-TTF(py)4 were then weighed and dissolved in a mixed solution of 0.75 mL of ethanol and 0.5 mL of H2O to obtain a solution of zinc nitrate and p-TTF(py)4. The two solutions were mixed in a 10 mL glass bottle and 0.1 mL of dilute HNO3 (2 mol / L) solution was added dropwise. After ultrasonic vibration for 5 min, the mixture was heated in an oven at 90 °C for 3 days. After the reaction was completed, the temperature was cooled at a rate of 5 °C / h. The product was filtered out at room temperature, washed with ethanol, and dried at 60 °C for 2 min. h, and obtained red block crystals (3.26 mg, yield 58%), which is the target product photothermal conversion crystal material. Example 2:

[0023] 5 mg (0.0196 mmol) of 2,2'-bithiophene-5,5'-dicarboxylic acid was weighed on a weighing balance and dissolved in 1.5 mL of N-N-dimethylformamide (DMF) to obtain a DMF solution of 2,2'-bithiophene-5,5'-dicarboxylic acid. 10 mg (0.034 mmol) of Zn(NO3)2·6H2O and 5 mg (0.0098 mmol) of p-TTF(py)4 were then weighed and dissolved in a mixed solution of 1.5 mL of ethanol and 0.5 mL of H2O to obtain a solution of zinc nitrate and p-TTF(py)4. The two solutions were mixed in a 20 mL glass bottle and 0.2 mL of dilute HNO3 (2 mol / L) solution was added dropwise. After ultrasonic vibration for 5 min, the mixture was heated in an oven at 90 °C for 3 days. After the reaction was completed, the temperature was cooled at a rate of 5 °C / h. The product was filtered out at room temperature, washed with ethanol, and heated at 60 After drying at ℃ for 2 h, red block crystals were obtained, which was the target product. Example 3:

[0024] 10 mg (0.0392 mmol) of 2,2'-bithiophene-5,5'-dicarboxylic acid was weighed on a weighing balance and dissolved in 3 mL of N-N-dimethylformamide (DMF) to obtain a DMF solution of 2,2'-bithiophene-5,5'-dicarboxylic acid. 20 mg (0.068 mmol) of Zn(NO3)2·6H2O and 10 mg (0.0196 mmol) of p-TTF(py)4 were then weighed and dissolved in a mixed solution of 3 mL of ethanol and 1 mL of H2O to obtain a solution of zinc nitrate and p-TTF(py)4. The two solutions were mixed in a 20 mL glass bottle and 0.4 mL of dilute HNO3 (2 mol / L) solution was added dropwise. After ultrasonic vibration for 5 min, the mixture was heated in an oven at 90 °C for 3 days. After the reaction was completed, the temperature was cooled at a rate of 5 °C / h. The product was filtered out at room temperature, washed with ethanol, and dried at 60 °C for 2 min. h, and red block crystals were obtained, which were the target product.

[0025] The performance of the photothermal conversion crystal material prepared in the embodiment of the present invention was tested.

[0026] The black block crystals prepared in Example 1 were subjected to single crystal X-ray diffraction analysis. Crystals of suitable size and regular shape were selected at room temperature and fixed on the test needle with epoxy resin glue. The test needle was then placed on a Bruker APEX-II CCD diffraction microscope using a graphite monochromator. α The sample was tested with X-ray (λ = 0.71073 Å), and the data were collected using CrysAlisPro-Agilent software. The crystal structure was solved directly using the ShelXS program, and anisotropic refinement was performed using ShelXL. 2 Full-matrix least squares was used for refinement and correction. The coordinates of non-hydrogen atoms in the structure were gradually determined by difference Fourier peak synthesis and anisotropic refinement was performed. Hydrogen atoms were obtained by theoretical hydrogenation, and all hydrogen atoms were isotropically refined. Further data refinement was then performed using full-matrix least squares in SHELXL-97 to finally determine the crystal formula. The test results showed that the black bulk crystals prepared in Example 1 were the target product, photothermal conversion crystal material.

[0027] The results of X-ray single crystal diffraction test and analysis show that the prepared crystal material belongs to the monoclinic system, the space group is P21 (no.4), and its molecular formula is C 46 H 24N4O8S8Zn2, with a molecular weight of 1154.4, unit cell parameters a = 7.0530(13) Å, b = 20.5202(14) Å, c = 16.4849(8) Å, α = γ = 90°, β = 97.1°, and its asymmetric unit consists of a p-TTF(py)4, a 2,2'-bithiophene-5,5'-dicarboxylic acid, and a Zn 2+ ; Zn 2+ The four-coordination mode is adopted, with two oxygen atoms coming from two different 2,2'-bithiophene-5,5'-dicarboxylate groups and two nitrogen atoms coming from two different p-TTF(py)4 ligands (coordination mode as Figure 1 The five atoms together form a tetrahedral secondary building unit (SBU), which is connected in different directions by the ligand p-TTF(py)4 and 2,2'-bithiophene-5,5'-dicarboxylic acid to form a three-dimensional network structure (as shown in Figure 2 ); Observing the three-dimensional structure along the a-axis direction, there are four different channels (such as Figure 3 ); The black block crystals prepared in Examples 1 and 2 were irradiated with laser light, and X-ray diffraction (XRD) analysis was performed on the crystals before and after irradiation. The results showed that the original characteristic peaks of the crystals still existed after irradiation, indicating that the material was pure phase, had good crystallinity, and had good stability (such as Figure 4 The results of thermogravimetric tests show that the crystal material skeleton remains stable at 300 °C (e.g. Figure 5 ).

[0028] Photothermal conversion performance test: 10 mg of the crystal material powder of the sample to be tested was evenly spread on a glass surface dish 5 cm away from an 808 nm laser. The laser power was selected to be 0.4 W·cm -2 and 1.6 W·cm -2 The temperature rise reaction of the crystal sample to the laser was tested with an infrared thermal imager, and the temperature rise curve and the photothermal conversion cycle diagram were produced by recording the video with FLIR Thermal Studio software. -2 Under the irradiation of high-power near-infrared laser, the temperature rises to 200°C in 5 seconds and can reach a maximum temperature of 240°C (such as Figure 6 ). Under 808 nm laser (0.4 W·cm −2 ) light, the surface temperature change under repeated laser on / off cycles was tested. The test results showed that the temperature of the MOF crystal material rose rapidly from room temperature to 85 ° C. After 5 cycles, the photothermal performance of the crystal material did not decay (such as Figure 7), and the same test was carried out again three weeks later. The crystal material was still stable and the photothermal performance did not decrease, proving that the photothermal conversion performance of the MOF material was stable and could be reused.

[0029] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0030] The above-described embodiments merely represent several implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A photothermal conversion crystal material, characterized by: The photothermal conversion crystal material belongs to the monoclinic system, the space group is P21 (no.4), and the molecular formula is C 46 H 24 N4O8S8Zn2, molecular weight is 1154.4, unit cell parameters are a=7.0530(13) Å, b=20.5202(14) Å, c=16.4849(8) Å, α=γ= 90°, β=97.1°.

2. The photothermal conversion crystal material according to claim 1, characterized in that: The asymmetric unit of the photothermal conversion crystal material includes a p-TTF(py)4, a 2,2'-bithiophene-5,5'-dicarboxylic acid and a Zn 2+ ; Zn 2+ It adopts a four-coordination mode, with two oxygen atoms coming from two different 2,2'-bithiophene-5,5'-dicarboxylate groups and two nitrogen atoms coming from two different p-TTF(py)4 ligands. The five atoms together form a secondary building unit with a tetrahedral structure.

3. The photothermal conversion crystal material according to claim 2, characterized in that: The secondary building units are connected in different directions through two ligands to form a three-dimensional network structure having four different pores.

4. The photothermal conversion crystal material according to claim 3, characterized in that: The ligands are p-TTF(py)4 and 2,2'-bithiophene-5,5'-dicarboxylic acid, The structural formula of 2,2'-bithiophene-5,5'-dicarboxylic acid is as follows: ； p-TTF(py)4 is 3,4,5,6-tetrakis(4-pyridyl)tetrathiafulvalenoate, with the following structural formula: 。 5. A method for preparing the photothermal conversion crystal material according to any one of claims 1 to 4, characterized in that The following steps are involved: Weigh 2,2'-bithiophene-5,5'-dicarboxylic acid and dissolve it in N-dimethylformamide to obtain a DMF solution of 2,2'-bithiophene-5,5'-dicarboxylic acid; Weigh Zn(NO3)2·6H2O and p-TTF(py)4 and dissolve them in a mixed solution of ethanol and H2O to obtain a solution of zinc nitrate and p-TTF(py)4; The above two solutions were mixed, and a dilute HNO3 (2.0 mol / L) solution was added dropwise. After ultrasonic vibration treatment, the mixture was heated in a 90°C oven for reaction. After the reaction, the temperature was cooled at a rate of 5°C / h. The product was filtered out at room temperature, washed with ethanol, and dried at 60°C to obtain black block crystals, which are the photothermal conversion crystal materials.

6. The preparation method according to claim 5, characterized in that: The molar ratio of the 2,2'-bithiophene-5,5'-dicarboxylic acid, zinc nitrate and p-TTF(py)4 is 2:3.5:

1.

7. The preparation method according to claim 5, characterized in that: All substances or solvents involved in the reaction are chemically pure.

8. A use of the photothermal conversion crystal material according to any one of claims 1 to 4, characterized in that: Used in photothermal conversion equipment.

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