A dithiine functionalized metal organic framework photothermal material, a free radical metal organic framework photothermal material, and preparation method and application thereof

Abstract

The present invention discloses a dithiino-functionalized metal organic framework photothermal material, a free radical metal organic framework photothermal material, and a preparation method and application thereof. Tetrathioanthracene is used as a connecting group to connect the trinuclear iron oxide clusters in a direction to form a ring, and the tripyridylamine is connected to the Fe atom in the ring to make the trinuclear iron oxide clusters become 9-coordinated connections. The formed MOF has good hydrophilicity and a wide light absorption range; it has a stable framework structure, and the one-dimensional pore structure therein provides a channel for water transport; therefore, the solar energy that is easily obtained is converted into thermal energy for water evaporation; and the sulfur-containing unsaturated double bond in the tetrathioanthracene is used as a modifiable group, and after high-temperature annealing, the ring shrinks to form a framework with stable free radicals, showing a wide absorption spectrum, which is conducive to the absorption of sunlight, and gives the material a strong photothermal conversion ability. The dithiino-functionalized metal organic framework photothermal material can be prepared by solvent thermal reaction; the preparation process is simple and easy to prepare on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal-organic framework functional materials, and particularly relates to a dithienyl-functionalized metal-organic framework photothermal material, a free-metal metal-organic framework photothermal material, and their preparation methods and applications. Background Art

[0002] With the increasing consumption of traditional fossil energy and the continuous increase of ecological environment pressure, accelerating the development and utilization of renewable energy solar energy has become a global focus. The effective utilization of solar energy has always been a hot research field. Among them, photothermal conversion is a clean and efficient way to utilize solar energy. Using solar energy to achieve efficient water evaporation for seawater desalination and sewage treatment is one of the most promising sustainable freshwater production technologies, providing new solutions to the global freshwater shortage problem. Traditional water evaporation technologies are mainly powered by fossil fuels, requiring high energy consumption and producing environmentally harmful by-products. While solar water evaporation technology can directly convert clean, environmentally friendly and low-cost solar energy into heat energy for steam generation, effectively solving the water resource shortage problem.

[0003] Photothermal conversion materials (light absorbers), as the key part of solar water evaporation applications, their performance determines the efficiency of water evaporation. To achieve high water evaporation rates and solar thermal conversion efficiencies, ideal photothermal conversion materials should have broad light absorption, high solar thermal conversion efficiency, high hydrophilicity, low thermal conductivity, etc. Currently, various photothermal conversion materials have been developed, such as carbon-based materials, metal nanoparticles, metal oxides, natural biological materials, and polymer absorbers. However, most absorbers have problems such as limited light absorption range, poor water transport ability, low photothermal conversion efficiency, or short service life.

[0004] Metal-organic framework materials (MOFs) are a class of porous crystalline materials formed by the self-assembly of metal ions and organic ligands, showing many application prospects in many fields such as catalysis, gas adsorption and separation, and chemical sensing. MOF has the advantages of a well-defined structure, low thermal conductivity, adjustable structure, and functional designability, and is expected to provide new ideas for the development of a new generation of photothermal conversion materials with good hydrophilicity and broad light absorption. Due to the intrinsic hydrophobicity and limited light absorption of MOF, there are still great challenges in its application as a photothermal conversion material in solar water evaporation. Summary of the Invention

[0005] For the above reasons, the first object of the present invention is to provide a dithienyl-functionalized metal-organic framework photothermal material, which has good hydrophilicity and a wide light absorption range; has a stable framework structure, and the one-dimensional pore structure therein provides a channel for water transport; therefore, it is very easy to convert the obtained solar energy into heat energy for water evaporation; and there are modifiable groups, providing a way for subsequent further synthesis and modification.

[0006] The second object of the present invention is to provide a preparation method of a dithienyl-functionalized metal-organic framework photothermal material.

[0007] The third object of the present invention is to provide a preparation method of a free metal-organic framework photothermal material.

[0008] The fourth object of the present invention is to provide a free metal-organic framework photothermal material with stable free radicals, which can achieve excellent photothermal conversion.

[0009] The fifth object of the present invention is to provide an application of a material. It is used as a photothermal conversion material for solar water evaporation.

[0010] The first object of the present invention can be achieved by adopting the following technical solutions:

[0011] A dithienyl-functionalized metal-organic framework photothermal material, comprising a monomer with the structure shown in Formula I, a monomer with the structure shown in Formula II, and a trinuclear iron oxide cluster;

[0012] Wherein, two oxygen atoms of one carboxyl group of the monomer with the structure shown in Formula I are respectively coordinately connected to two adjacent metal Fe atoms of a trinuclear iron oxide cluster, and two oxygen atoms of the other carboxyl group are respectively coordinately connected to two adjacent metal Fe atoms of another trinuclear iron oxide cluster; six trinuclear iron oxide clusters are sequentially connected by six monomers with the structure shown in Formula I to form a honeycomb-shaped hexagonal pore channel;

[0013] At the same time, each Fe center is hexacoordinated by four oxygen atoms of four monomers with the structure shown in Formula I, one N atom of a monomer with the structure shown in Formula II, and one central μ 3 -O to form an octahedral structure; the trinuclear iron oxide cluster forms a 9-connected rigid network with six monomers with the structure shown in Formula I and three monomers with the structure shown in Formula II; wherein the N atom of the monomer with the structure shown in Formula II occupies three axial positions;

[0014] The trinuclear iron oxide cluster is centered on μ 3 -O, and three octahedrally coordinated Fe atoms are connected with μ 3 -O as vertices; two carboxyl oxygen atoms on two ligands with the structure shown in Formula I are coordinately connected between two adjacent Fe atoms;

[0015]

[0016] The second object of the present invention can be achieved by adopting the following technical solutions:

[0017] A preparation method of a dithienyl-functionalized metal-organic framework photothermal material, in which monomers with the structure shown in Formula I, monomers with the structure shown in Formula II, and an iron salt react through solvothermal reaction to prepare the dithienyl-functionalized metal-organic framework photothermal material.

[0018] Furthermore, the molar ratio of the monomer with the structure shown in Formula I to the monomer with the structure shown in Formula II is 1:(0.9 - 1.2).

[0019] Furthermore, the molar ratio of the monomer with the structure shown in Formula I to the iron salt is 1:(2 - 2.5).

[0020] Furthermore, a mixed reagent of DMF and / or DMA and N,N-dimethylallylurea is used as the solvent; the volume ratio of DMF and / or DMA to N,N-dimethylallylurea is (1 - 4):1.

[0021] Furthermore, the reaction is carried out at 110 - 140 °C for 6 - 72 h.

[0022] Furthermore, the molar volume ratio of the monomer with the structure shown in Formula I to the solvent is (10 - 50) μmol:1 mL.

[0023] Furthermore, hexafluoroacetylacetone is added during the reaction, and the added volume of hexafluoroacetylacetone is 1% - 4% of the volume of the solvent.

[0024] Furthermore, the reaction includes a separation and washing process; after separation, the solid is washed with DMF and water; then the solid is soaked in an acetonitrile solution for 2 - 4 days.

[0025] To achieve the third object of the present invention, the following technical solution can be adopted:

[0026] A preparation method of a free metal-organic framework photothermal material, in which the above-mentioned dithienyl-functionalized metal-organic framework photothermal material undergoes a thermal annealing reaction in an inert gas atmosphere to prepare the free metal-organic framework photothermal material.

[0027] Furthermore, the inert gas atmosphere is a nitrogen atmosphere.

[0028] Furthermore, the conditions for the thermal annealing reaction are: maintaining at 250 - 320 °C for 3 - 24 h.

[0029] To achieve the fourth object of the present invention, the following technical solution can be adopted:

[0030] A free metal-organic framework photothermal material, which is prepared by the preparation method of a free metal-organic framework photothermal material described above.

[0031] The fifth object of the present invention can be achieved by adopting the following technical solutions:

[0032] Application of dithienyl-functionalized metal-organic framework photothermal material or free metal-organic framework photothermal material as a photothermal conversion material.

[0033] Furthermore, the material is loaded on a polyurethane membrane and water evaporation is carried out under sunlight.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. A dithienyl-functionalized metal-organic framework photothermal material of the present invention uses carboxyl-containing tetrathiaanthracene and tripyridylamine as monomers and trinuclear iron oxide clusters as metal connection sites; tetrathiaanthracene is used as a linking group to orientally link trinuclear iron oxide clusters into a ring, and tripyridylamine further connects to Fe atoms within the ring to enhance the stability and photoelectric conversion performance of the framework. The formed MOF has good hydrophilicity and a wide light absorption range; it has a stable framework structure, and the one-dimensional pore structure therein provides a channel for water transportation; therefore, the easily obtained solar energy is converted into heat energy for water evaporation; and the sulfur-containing unsaturated double bond in tetrathiaanthracene serves as a modifiable group, providing a way for subsequent further synthesis and modification.

[0036] 2. A preparation method of a dithienyl-functionalized metal-organic framework photothermal material of the present invention can be prepared by a solvothermal reaction; the preparation process is simple and easy to prepare on a large scale.

[0037] 3. The free metal-organic framework photothermal material of the present invention has strong radical stability, exhibits a wide absorption spectrum, is beneficial to the absorption of sunlight, and endows the material with extremely strong photothermal conversion ability.

[0038] 4. A preparation method of the free metal-organic framework photothermal material of the present invention can be prepared by post-modification of heat treatment of the dithienyl-functionalized metal-organic framework photothermal material. The post-synthesis modification method has simple steps, high yield and can be prepared in large quantities. Description of the Drawings

[0039] Figure 1 Single crystal X-ray structure simulation diagrams of FeTTA-TPA prepared in the examples, FeTTA-TPA-300 and FeTTA prepared in Comparative Example 1;

[0040] Figure 2 Single crystal photographs of (a) FeTTA, (b) FeTTA-TPA and (b) FeTTA-TPA-300.

[0041] Figure 3is an X-ray powder diffraction pattern; among which (a) is the simulated structure of FeTTA-TPA single crystal; (b) is the synthesized FeTTA-TPA sample; (c) is the FeTTA-TPA-300 sample after thermal annealing; (d) is the simulated structure of FeTTA single crystal; (e) is the synthesized FeTTA sample; (f) is the FeTTA sample after thermal annealing at 300 °C;

[0042] Figure 4 is the organic ligand H 2 TTA, the FeTTA-TPA and FeTTA-TPA-300 prepared in the examples, and the FeTTA prepared in Comparative Example 1 and the FeTTA-300 prepared in Comparative Example 2 are Fourier transform-infrared spectrograms;

[0043] Figure 5 is the thermogravimetric analysis diagram of FeTTA-TPA and FeTTA under nitrogen conditions;

[0044] Figure 6 is the solid ultraviolet-visible absorption spectrogram of FeTTA, FeTTA-TPA and FeTTA-TPA-300;

[0045] Figure 7 is the solid EPR test diagram of 10.0 mg of FeTTA, FeTTA-TPA and FeTTA-TPA-300 at room temperature;

[0046] Figure 8 is the water contact angle test diagram of FeTTA, FeTTA-TPA and FeTTA-TPA-300;

[0047] Figure 9 is the interface temperature change diagram of each sample under simulated sunlight irradiation for 1 h;

[0048] Figure 10 is the interface moisture evaporation mass change diagram of each sample under simulated sunlight irradiation for 1 h. Detailed implementation manners

[0049] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with specific embodiments. Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0050] Currently, for water evaporation using MOF as a photothermal conversion material, due to the intrinsic hydrophobicity and limited light absorption of MOF, improving the hydrophilicity and light absorption range of MOF materials is the main goal for solar water evaporation applications. Most of the existing solar water evaporation systems based on MOF introduce additional inorganic materials, such as composite carbon-based materials (e.g., graphene or carbon nanotubes), to obtain good light absorption ability and adjustable water transport paths. However, introducing stable free radicals into the MOF framework to enable charge transfer in the overall structure and thus effectively reduce the material bandgap and expand near-infrared absorption is one of the best strategies to enhance the light absorption ability. Radical MOF not only has characteristics such as a well-defined coordination structure, porosity, and chemical stability, but also has the characteristics of free radicals, including high spin density and extended absorption in the near-infrared region, which endows radical MOF with excellent photothermal properties.

[0051] Based on the above, the present application provides a dithienyl-functionalized metal-organic framework photothermal material, a free radical metal-organic framework photothermal material, and their preparation methods and applications.

[0052] A dithienyl-functionalized metal-organic framework photothermal material, comprising a monomer with the structure shown in Formula I, a monomer with the structure shown in Formula II, and a trinuclear iron oxide cluster;

[0053] Among them, two oxygen atoms of one carboxyl group of the monomer with the structure shown in Formula I are respectively coordinately connected to two adjacent metal Fe atoms of a trinuclear iron oxide cluster, and two oxygen atoms of the other carboxyl group are respectively coordinately connected to two adjacent metal Fe atoms of another trinuclear iron oxide cluster; six trinuclear iron oxide clusters are sequentially connected by six monomers with the structure shown in Formula I to form a honeycomb-like hexagonal pore channel;

[0054] At the same time, each Fe center is hexacoordinated by four oxygen atoms of four monomers with the structure shown in Formula I, one N atom of a monomer with the structure shown in Formula II, and one central μ 3 -O to form an octahedral structure; enabling the trinuclear iron oxide cluster to form a 9-connected rigid network with six monomers with the structure shown in Formula I and three monomers with the structure shown in Formula II; where the N atom of the monomer with the structure shown in Formula II occupies three axial positions;

[0055] The molecular formula of the trinuclear iron oxide cluster is [Fe 3 O(COO) 6 , with μ 3 -O as the center, three octahedrally coordinated Fe atoms are connected with μ 3 -O as the vertices; two carboxyl oxygen atoms on two ligands with the structure shown in Formula I coordinately connect adjacent two Fe atoms.

[0056]

[0057] The monomer with the structure shown in Formula I is a dithienyl-functionalized carboxyl ligand (H 2 TTA), and the monomer with the structure shown in Formula II is a pyridyl ligand tripyridylamine (TPA), where H 2 TTA coordinates and assembles with the trinuclear iron oxide cluster, and pyridine participates in coordination to form a highly stable 9-connected trinuclear iron oxide cluster and a host framework containing sulfur unsaturated double bonds; it has a highly ordered three-dimensional framework stable structure, and the one-dimensional pore structure formed provides a channel for water transportation; the N group in the middle of the TPA molecule is a strong electron donor, which can increase the electron density in the MOF framework and promote the charge transport of the overall framework; the formed MOF has good hydrophilicity and a wide light absorption range; therefore, the easily obtained solar energy is converted into heat energy for water evaporation; and the sulfur unsaturated double bond in tetrathiaanthracene serves as a modifiable group, providing a way for subsequent further synthesis and modification.

[0058] A preparation method of a dithienyl-functionalized metal-organic framework photothermal material of the present invention is that the monomer with the structure shown in Formula I, the monomer with the structure shown in Formula II, and an iron salt react through solvothermal treatment to prepare the dithienyl-functionalized metal-organic framework photothermal material.

[0059] Solvothermal reaction is a common method for preparing MOF. In this application, by selecting an appropriate monomer with the structure shown in Formula I and an iron salt for directional assembly, the iron atom is coordinatively connected to the oxygen on the carboxyl group of the monomer with the structure shown in Formula I in the form of a trinuclear iron oxide cluster.

[0060] The molecular formula of the trinuclear metal oxide cluster is [Fe 3 O(COO) 6 , with μ 3 -O as the center, three octahedrally coordinated Fe atoms are connected with μ 3 -O as the vertex. At the same time, each trinuclear iron oxide cluster is connected to six monomers with the structure shown in Formula I. The two oxygen atoms of the carboxyl group on each monomer with the structure shown in Formula I are respectively coordinatively connected to two adjacent Fe atoms of the trinuclear metal oxide cluster, forming a trinuclear metal oxide cluster and a three-dimensional network with the structure shown in Formula I. Each Fe center is composed of four oxygen atoms of four TTA ligands, one The N atom of one TPA ligand and one central μ 3 -O atom form an octahedral geometry through six coordination.

[0061] The two oxygen atoms of one carboxyl group of the monomer with the structure shown in Formula I are respectively coordinatively connected to two adjacent metal Fe atoms of a trinuclear iron oxide cluster, and the two oxygen atoms of the other carboxyl group are respectively coordinatively connected to two adjacent metal Fe atoms of another trinuclear iron oxide cluster; six trinuclear iron oxide clusters are sequentially connected by six monomers with the structure shown in Formula I to enclose a cavity, forming a one-dimensional pore structure along the c-axis direction.

[0062] Specifically, the N atom of the monomer with the structure shown in Formula II occupies three axial positions and connects to the Fe near the cavity of the trinuclear iron oxide cluster, changing the connection of a trinuclear iron oxide cluster from a 6-ligand connection to a more stable 9-ligand connection. It also divides the one-dimensional hexagonal pore channels along the FeTTAc axis into many cylindrical cavities with a length of about . In addition, due to the coordination connection of the monomer with the structure shown in Formula II, the N group in the middle of the molecule is a strong electron donor, which can increase the electron density in the MOF framework and promote the charge transport of the overall framework.

[0063] As one of the embodiments, the molar ratio of the monomer with the structure shown in Formula I to the monomer with the structure shown in Formula II is 1:(0.9 - 1.2).

[0064] As one of the embodiments, the iron salt is one or more combinations of iron hydrochloride, sulfate, nitrate or their hydrates. Preferably, the iron salt is FeCl 3 ·6H 2 O.

[0065] As one of the embodiments, the molar ratio of the monomer with the structure shown in Formula I to the iron salt is 1:(2 - 2.5). Through the ligands of the above monomers and iron salts, directional assembly can be achieved.

[0066] As one of the embodiments, the conditions for the solvothermal reaction are as follows:

[0067] Using a mixed reagent of DMF and / or DMA and N,N-dimethylallylurea as the solvent; the volume ratio of DMF and / or DMA to N,N-dimethylallylurea is (1 - 4):1.

[0068] As one of the embodiments, the reaction is carried out at 110 - 140 °C for 6 - 72 h.

[0069] As one of the embodiments, hexafluoroacetylacetone is also added to the reaction, and the added volume of hexafluoroacetylacetone is 1% - 4% of the solvent volume.

[0070] As one of the embodiments, the molar volume ratio of the monomer with the structure shown in Formula I to the solvent is (10 - 50) μmol:1 mL. The conditions of the above solvothermal reaction are selected according to the properties of the monomer and the iron salt, and the reaction temperature and time achieve better reaction effects.

[0071] As one of the embodiments, the reaction is followed by a separation and washing process; after separation, the solid is washed with DMF and water; then the solid is soaked in an acetonitrile solution for 2 - 4 days. Specifically, the single crystal sample is washed with DMF (5 mL × 5) and water (5 mL × 5), and then soaked in an acetonitrile solution for 2 - 4 days. After soaking, the solid-liquid separation is carried out and dried in vacuo.

[0072] The present invention also provides a method for preparing a free metal-organic framework photothermal material, by subjecting the above-mentioned dithienyl-functionalized metal-organic framework photothermal material to a thermal annealing reaction under an inert gas atmosphere to obtain the free metal-organic framework photothermal material;

[0073]

[0074] The sulfur-containing unsaturated double bonds in the framework form a framework with stable free radicals through ring contraction after thermal annealing, while the original MOF only shows a very weak or even negligible free radical signal. The tight three-dimensional stacking structure of the MOF enhances the stability of the free radicals. The free radical MOF has a broad absorption spectrum, which is beneficial to the absorption of sunlight, endowing it with extremely strong photothermal conversion ability.

[0075] As one of the embodiments, the inert gas atmosphere is a nitrogen atmosphere.

[0076] As one of the embodiments, the conditions of the thermal annealing reaction are: maintaining at 250 - 320 °C for 3 - 24 h.

[0077] The present invention provides a free metal-organic framework photothermal material, which is prepared by the preparation method of a free metal-organic framework photothermal material as described above.

[0078] The sulfur-containing unsaturated double bonds undergo ring contraction after thermal annealing. Among them, the tight three-dimensional stacking structure of the MOF after annealing enhances the stability of the free radicals, and the formed free metal-organic framework photothermal material is a framework with stable free radicals. It exhibits a broad absorption peak, which is beneficial to the absorption of sunlight, endowing it with extremely strong photothermal conversion ability.

[0079] Application of the dithienyl-functionalized metal-organic framework photothermal material or the free metal-organic framework photothermal material as a photothermal conversion material.

[0080] As one of the embodiments, the material is loaded on a polyurethane membrane for water evaporation under sunlight.

[0081] The following is further illustrated with specific examples.

[0082] Example 1

[0083] Weigh H2 44 μmol of TTA, 44 μmol of TPA and FeCl 3 ·6H 2 88 μmol of O were placed in a glass tube (8×150 mm). 1 ml of N,N-dimethylformamide, 0.5 ml of N,N-dimethylallylurea and 20 μL of hexafluoroacetylacetone were added. Subsequently, the mixture was sonicated for 10 min; the glass tube was sealed with a hydrogen-oxygen flame and heated in an oven at 120 °C for 72 h, then naturally cooled to room temperature; the crystals were collected by filtration, and the single-crystal sample was washed with DMF (5 mL×5) and water (5 mL×5). Subsequently, it was soaked in an acetonitrile solution for 3 days and dried in vacuo to obtain the dithiophene-functionalized metal-organic framework photothermal material, named FeTTA-TPA, with a yield of 80%.

[0084] Example 2

[0085] Weighed H 2 44 μmol of TTA, 39.6 μmol of TPA and FeCl 3 110 μmol were placed in a glass tube (8×150 mm). 1.1 ml of N,N-dimethylformamide, 1.1 ml of N,N-dimethylacetamide, 2.2 ml of N,N-dimethylallylurea and 44 μL of hexafluoroacetylacetone were added. Subsequently, the mixture was sonicated for 10 min; the glass tube was sealed with a hydrogen-oxygen flame and heated in an oven at 140 °C for 6 h, then naturally cooled to room temperature; the crystals were collected by filtration, and the single-crystal sample was washed with DMF (5 mL×5) and water (5 mL×5). Subsequently, it was soaked in an acetonitrile solution for 3 days and dried in vacuo to obtain the dithiophene-functionalized metal-organic framework photothermal material, named FeTTA-TPA, with a yield of 78%.

[0086] Example 3

[0087] Weighed H 2 44 μmol of TTA, 52.8 μmol of TPA and FeCl 3 ·6H 2 99 μmol of O were placed in a glass tube (8×150 mm). 0.7 ml of N,N-dimethylacetamide, 0.18 ml of N,N-dimethylallylurea and 35 μL of hexafluoroacetylacetone were added. Subsequently, the mixture was sonicated for 10 min; the glass tube was sealed with a hydrogen-oxygen flame and heated in an oven at 110 °C for 72 h, then naturally cooled to room temperature; the crystals were collected by filtration, and the single-crystal sample was washed with DMF (5 mL×5) and water (5 mL×5). Subsequently, it was soaked in an acetonitrile solution for 3 days and dried in vacuo to obtain the dithiophene-functionalized metal-organic framework photothermal material, named FeTTA-TPA, with a yield of 75%.

[0088] Example 4

[0089] Weigh 100 mg of FeTTA-TPA and place it in aluminum foil. Then, put the crystal wrapped in aluminum foil on a quartz boat and place the quartz boat into a tube furnace. After evacuating the tube furnace and purging it with nitrogen three times, keep the nitrogen flowing inside the tube and program the temperature to rise to 300 °C and hold for 6 h. After 6 h, take out the quartz boat from the tube furnace to cool it to room temperature, obtaining a free metal-organic framework photothermal material, named FeTTA-TPA-300.

[0090] Example 5

[0091] Weigh 100 mg of FeTTA-TPA and place it in aluminum foil. Then, put the crystal wrapped in aluminum foil on a quartz boat and place the quartz boat into a tube furnace. After evacuating the tube furnace and purging it with nitrogen three times, keep the nitrogen flowing inside the tube and program the temperature to rise to 250 °C and hold for 24 h. After 24 h, take out the quartz boat from the tube furnace to cool it to room temperature, obtaining a free metal-organic framework photothermal material, named FeTTA-TPA-250.

[0092] Example 6

[0093] Weigh 100 mg of FeTTA-TPA and place it in aluminum foil. Then, put the crystal wrapped in aluminum foil on a quartz boat and place the quartz boat into a tube furnace. After evacuating the tube furnace and purging it with nitrogen three times, keep the nitrogen flowing inside the tube and program the temperature to rise to 320 °C and hold for 3 h. After 3 h, take out the quartz boat from the tube furnace to cool it to room temperature, obtaining a free metal-organic framework photothermal material, named FeTTA-TPA-320.

[0094] Example 7

[0095] Ultrasonically disperse 50 mg of FeTTA-TPA-300 powder in isopropanol for 30 min. Drop the mixture evenly onto a PU with a diameter of 2.2 cm and dry it at 85 °C for 1 h, then cool it to obtain the FeTTA-TPA-300@PU film.

[0096] Comparative Example 1

[0097] Weigh 44 μmol of H 2 TTA and 88 μmol of FeCl 3 ·6H 2In a glass tube (8×150 mm), add 1.5 ml of N,N-dimethylformamide and 25 μL of glacial acetic acid, and then ultrasonically treat the mixture for 10 min; seal the glass tube with a hydrogen-oxygen flame and heat it in an oven at 140 °C for 24 h, and then naturally cool it to room temperature; collect the crystals by filtration, wash the single-crystal sample with DMF (5 mL×5) and water (5 mL×5), then soak it in an acetonitrile solution for 3 days, and dry it in vacuo to obtain FeTTA crystals, yield: 60%.

[0098] Comparative Example 2

[0099] Weigh 100 mg of FeTTA prepared in Comparative Example 1 and place it in aluminum foil, then place the crystal wrapped in aluminum foil on a quartz boat and put the quartz boat into a tube furnace; after evacuating and purging the tube furnace with nitrogen three times, keep the nitrogen flowing in the tube and program the temperature to 300 °C and hold for 6 h; after 6 h, take out the quartz boat from the tube furnace to cool to room temperature to obtain a free radical metal-organic framework photothermal material, named FeTTA-300.

[0100] Test Example:

[0101] (1) Perform single-crystal X-ray structure simulation on FeTTA-TPA, FeTTA-TPA-300 prepared in the examples and FeTTA prepared in Comparative Example 1; the single-crystal structure is as Figure 1 shown, where (a) is the single-crystal structure of FeTTA; (b) is the single-crystal structure of FeTTA-TPA; (c) is the single-crystal structure of FeTTA-TPA-300; (d) is the single-crystal to single-crystal transformation process of the TTA ligand in the MOF; the single-crystal photos are as Figure 2 shown; where (a) is FeTTA, (b) is FeTTA-TPA, and (b) is FeTTA-TPA-300.

[0102] It can be seen from the results of the single-crystal X-ray diffraction test that the synthesized FeTTA framework has a one-dimensional pore of about 1 nm, in which one trinuclear iron-oxygen cluster is connected to six TTA molecules respectively to form a three-dimensional network. Each Fe atom adopts an octahedral coordination configuration and is hexacoordinated by one μ 3 -O atom, four carboxyl oxygen atoms of four TTA ligands and an oxygen atom from the terminal solvent molecule. After introducing TPA, each Fe center is hexacoordinated by four oxygen atoms of four TTA, one N atom of TPA and one central μ 3 -O to form an octahedral structure; enabling the trinuclear iron-oxygen cluster to form a 9-connected rigid network with six TTA and three TPA; where the N atom of TPA occupies three axial positions.

[0103] The transformation from the six-membered disulfide ring to the five-membered disulfide ring in the TTA monomer was clearly revealed in the single-crystal structure after further thermal annealing treatment, and the pyridine ligand remained in the structure without being destroyed.

[0104] (2) X-ray powder diffraction tests were performed on FeTTA-TPA and FeTTA-TPA-300 prepared in the examples, FeTTA prepared in Comparative Example 1, and FeTTA-300 prepared in Comparative Example 2. The X-ray powder diffraction is as Figure 4 shown; where (a) single-crystal simulated structure of FeTTA-TPA; (b) synthesized FeTTA-TPA sample; (c) FeTTA-TPA-300 sample after thermal annealing; (d) single-crystal simulated structure of FeTTA; (e) synthesized FeTTA sample; (f) FeTTA sample after thermal annealing at 300 °C;

[0105] The crystal samples obtained before and after thermal annealing of FeTTA-TPA showed good crystallinity by powder X-ray diffraction. Moreover, the diffraction peak positions of FeTTA-TPA-300 and FeTTA-TPA were highly consistent and matched the single-crystal simulation, indicating that the MOF material maintained its original framework after thermal annealing. For the FeTTA framework without the introduction of TPA, its stability was poor, and the structure collapsed at a temperature of 300 °C, losing its original crystallinity.

[0106] (3) Fourier transform-infrared spectroscopy was performed on the organic ligand H 2 TTA, FeTTA-TPA and FeTTA-TPA-300 prepared in the examples, FeTTA prepared in Comparative Example 1, and FeTTA-300 prepared in Comparative Example 2. The results are as Figure 4 shown, where (a) organic ligand H 2 TTA; (b) synthesized FeTTA-TPA; (c) synthesized FeTTA-TPA-300; (d) organic ligand H 2 TTA; (e) synthesized FeTTA; (f) FeTTA after treatment at 300 °C.

[0107] In the Fourier transform infrared spectrum of FeTTA-TPA, it was observed that the original carboxyl C=O stretching vibration absorption peak at about 1690 cm 2 of H -1 TTA shifted, while the -HC=CH- stretching vibration remained at 3045 cm -1 ; At the same time, it was observed that in the TPA monomer, at about 1592 cm -1The absorption peak of -C=N- stretching vibration indicates that both organic ligands are successfully assembled to form FeTTA-TPA. The FeTTA-TPA-300 powder obtained by heat annealing at 300 °C also shows the -C=N- stretching vibration peak at 1592 cm -1 -1, while the stretching vibration peak of -HC=CH- disappears, indicating that the unsaturated double bonds in the sulfur ring successfully react during heating. As can be seen from the infrared spectrum of FeTTA, after heat annealing at 300 °C, the carboxyl C=O stretching vibration absorption peak of TTA itself at about 1645 cm -1 -1 has disappeared, further confirming the collapse caused by the instability of the framework.

[0108] (4) Thermogravimetric analysis of FeTTA-TPA and FeTTA was carried out under nitrogen atmosphere, and the results are as Figure 5 shown.

[0109] Under nitrogen atmosphere, FeTTA-TPA maintains structural stability within 360 °C; FeTTA shows obvious weight loss before 360 °C and has poor thermal stability.

[0110] (5) Solid ultraviolet-visible absorption tests were carried out on FeTTA, FeTTA-TPA and FeTTA-TPA-300, and the ultraviolet absorption spectra are as Figure 6 shown.

[0111] From Figure 6 the absorption spectrum test results, it can be seen that compared with the original FeTTA, after introducing the TPA ligand, the light absorption ability of FeTTA-TPA is broadened to a certain extent. The UV-Vis-NIR absorption spectrum measured at room temperature for the FeTTA-TPA-300 crystal obtained by further heat annealing shows obvious differences. The FeTTA-TPA-300 powder exhibits a broad absorption spectrum of 200 - 2500 nm covering the visible and near-infrared light ranges, greatly enhancing the absorption of sunlight. The radicals formed by the ring contraction in the FeTTA-TPA-300 framework generate strong intramolecular charge transfer and a low bandgap, which greatly improves non-radiative decay. Therefore, the FeTTA-TPA-300 powder has great potential for applications in solar light-thermal conversion and thermoelectric conversion.

[0112] (6) Solid EPR tests were carried out on 10.0 mg of FeTTA, FeTTA-TPA and FeTTA-TPA-300 at room temperature, and the results are as Figure 7 shown.

[0113] The FeTTA-TPA-300 solid exhibits an obvious EPR signal, while the original FeTTA-TPA and FeTTA solids do not show an EPR signal. This indicates that the FeTTA-TPA-300 of this application has strong free radicals.

[0114] (7) The water contact angles of FeTTA, FeTTA-TPA, and FeTTA-TPA-300 were measured, and the water contact angle diagrams are as Figure 8 shown.

[0115] From Figure 8 it can be seen that the water contact angles of FeTTA, FeTTA-TPA, and FeTTA-TPA-300 are all within 90.4°. In particular, the water contact angle of the formed FeTTA-TPA is 90.4°. However, after annealing treatment at 300 °C, the water contact angle of the formed FeTTA-TPA-300 is only 60.9°, showing excellent hydrophilicity.

[0116] Test examples:

[0117] In order to study the solar water evaporation performance of FeTTA-TPA powder, referring to the preparation method of Example 7, 50 mg of the powder sample was loaded on a polyurethane (PU) membrane to prepare FeTTA@PU membrane, FeTTA-TPA@PU membrane, and FeTTA-TPA-300@PU membrane; the porous PU foam provided good heat insulation and water transmission performance.

[0118] The PU membrane, FeTTA@PU membrane, FeTTA-TPA@PU membrane, and FeTTA-TPA-300@PU membrane were placed in water, and a xenon lamp was used to simulate a solar light intensity of 0.1 W cm -2 to irradiate the membrane, and the changes in temperature and mass within one hour were recorded. The temperature changes are as Figure 9 shown, and the results of the water mass change are as Figure 10 shown.

[0119] From Figure 9 the water evaporation interface temperature, it can be seen that the pure PU membrane reached the highest 36 °C within 20 min; the FeTTA@PU membrane had a slower heating rate and reached the highest temperature of about 40 °C in 40 min; the heating rate of the FeTTA-TPA@PU membrane after introducing TPA was significantly improved, and the highest temperature reached about 45.6 °C; while the FeTTA-TPA-300@PU membrane after thermal annealing had the most obvious improvement, and the interface temperature reached 50.7 °C within half an hour.

[0120] From Figure 10It can be obtained that the water evaporation rate of FeTTA-TPA@PU foam (50 mg) is greater than that of FeTTA@PU foam (50 mg); in particular, the water evaporation rate of FeTTA-TPA-300@PU foam (50 mg) is much higher than that of FeTTA-TPA@PU and FeTTA@PU, and the interfacial temperature can reach 50.7 °C. The calculated solar water evaporation efficiency of the FeTTA-TPA-300@PU membrane reaches 98%, which is much higher than 40% of the homogeneous MOF FeTTA@PU membrane without TPA modification.

[0121] In summary, a dithienyl-functionalized metal-organic framework photothermal material of the present invention uses carboxyl-containing tetrathiaanthracene and tripyridylamine as monomers, and trinuclear iron oxide clusters as metal connection sites; tetrathiaanthracene is used as a linking group to orientedly link trinuclear iron oxide clusters into a ring; the N group in the middle of the tripyridylamine molecule is a strong electron donor, which increases the electron density in the MOF framework, further connects with Fe atoms in the ring to strengthen the stability of the framework and promote the charge transport of the overall framework. The formed MOF has good hydrophilicity and a wide light absorption range; it has a stable framework structure, and the one-dimensional pore structure therein provides a channel for water transport; therefore, the easily obtained solar energy is converted into heat energy for water evaporation; moreover, the sulfur-containing unsaturated double bond in tetrathiaanthracene serves as a modifiable group, and after a high-temperature heat release reaction, the formed MOF has strong radical stability, exhibits a wide absorption spectrum, is beneficial to the absorption of sunlight, and endows the material with extremely strong photothermal conversion ability.

[0122] The above embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention belong to the scope of protection required by the present invention.

Claims

1. A dithiine functionalized metal organic framework material, characterized in that: Comprising a monomer having a structure shown in formula I, a monomer having a structure shown in formula II, and a trinuclear iron oxide cluster; The two oxygen atoms of a carboxyl group of the monomer of the structure shown in Formula I are respectively coordinated and connected with two metal Fe atoms adjacent to a trinuclear ferrite cluster, and the two oxygen atoms of another carboxyl group are respectively coordinated and connected with two metal Fe atoms adjacent to another trinuclear ferrite cluster; six trinuclear ferrite clusters are sequentially connected through six monomers of the structure shown in Formula I to form a honeycomb hexagonal channel; At the same time, each Fe center is hexa-coordinated by four oxygen atoms of four monomers of the structure shown in formula I, one N atom of a monomer of the structure shown in formula II, and one central μ3-O to form an octahedral structure; the trinuclear iron oxide cluster forms a 9-connected rigid network with six monomers of the structure shown in formula I and three monomers of the structure shown in formula II; wherein the N atoms of the monomer of the structure shown in formula II occupy three axial positions; The trinuclear iron oxide cluster is centered on μ3-O, and three octahedral coordinated Fe atoms are connected with μ3-O as vertices; two adjacent Fe atoms are connected by two carboxyl oxygen groups on two ligands of the structure shown in formula I; 2. A method for preparing the dithiine functionalized metal organic framework material according to claim 1, characterized in that: The monomer of the structure shown in formula I, the monomer of the structure shown in formula II and the iron salt react with each other through solvent thermal reaction to prepare the dithiine functionalized metal organic framework material.

3. The method for preparing a dithiine-functionalized metal organic framework material according to claim 2, characterized in that: The molar ratio of the monomer of the structure represented by formula I to the monomer of the structure represented by formula II is 1:(0.9-1.2); The molar ratio of the monomer of the structure shown in formula I to the iron salt is 1:(2-2.5).

4. The method for preparing a dithiine-functionalized metal organic framework material according to claim 2, characterized in that: The conditions for the solvent thermal reaction are: Using a mixed reagent of DMF and / or DMA and N,N-dimethylpropyleneurea as solvent; reacting at 110-140° C. for 6-72 hours; the volume ratio of DMF and / or DMA to N,N-dimethylpropyleneurea is (1-4):1; The molar volume ratio of the monomer of the structure represented by Formula I to the solvent is (10-50) μmol:1 mL.

5. The method for preparing a dithiine-functionalized metal organic framework material according to claim 2, characterized in that: Hexafluoroacetylacetone is also added during the reaction, wherein the added volume of the hexafluoroacetylacetone is 1%-4% of the volume of the solvent; The reaction comprises a separation and washing process; after separation, the solid is washed with DMF and water; and then the solid is soaked in an acetonitrile solution for 2-4 days.

6. A method for preparing a radical metal organic framework photothermal material, characterized in that: The dithiine functionalized metal organic framework material according to any one of claims 1 to 5 is subjected to a thermal annealing reaction under an inert gas atmosphere to prepare the free radical metal organic framework photothermal material.

7. The method for preparing a radical metal organic framework photothermal material according to claim 6, characterized in that: The inert gas atmosphere is a nitrogen atmosphere; The conditions of the thermal annealing reaction are: 250-320° C. for 3-24 hours.

8. A free radical metal organic framework photothermal material, characterized in that: The radical metal organic framework photothermal material is prepared by the method for preparing a radical metal organic framework photothermal material according to claim 6 or 7.

9. Use of the radical metal organic framework photothermal material prepared by the preparation method according to claim 6 or 7 or the radical metal organic framework photothermal material according to claim 8 as a photothermal conversion material.

10. The use according to claim 9, characterized in that: The material is supported on a polyurethane film and water is evaporated under sunlight.

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