Crystal material with photothermal conversion performance and preparation method and application thereof

Abstract

The invention discloses a crystal material with photothermal conversion performance and a preparation method and application thereof. Specifically, TTFDPNI-Cd-MOF belongs to an orthorhombic system, the space group is Pbca, and the cell parameters alpha = beta = gamma = 90 degrees. TTFDPNI-Co-MOF belongs to a monoclinic system, the space group is P21 / n, the cell parameters alpha = gamma = 90 degrees, and beta = 112.224 degrees. The prepared crystal material has good photothermal conversion performance, thermal stability and cycle durability. A test result shows that the crystal material has a wide application prospect as a photo-thermal conversion material.

Description

Technical Field

[0001] This invention belongs to the field of crystal chemistry, specifically relating to crystal materials with photothermal conversion properties, their preparation methods and uses, and in particular two metal-organic framework crystal materials with photothermal conversion properties, their preparation methods and uses. Background Technology

[0002] Solar interfacial evaporation is an emerging technology that utilizes the surface-localized thermal effect of photothermal conversion materials to drive water evaporation and produce pure water, potentially alleviating the freshwater shortage crisis. This technology features simple processes, low energy consumption, low cost, and environmental friendliness, showing broad application prospects in seawater desalination, wastewater purification, and other fields. Photothermal materials are a crucial component of solar evaporation systems and an important way to improve evaporation efficiency and achieve multi-scenario applications. Metal-organic frameworks (MOFs) are a class of crystalline materials with abundant porous structures. Their ordered porous structure effectively increases the interaction with incident sunlight, facilitating light collection and achieving excellent photothermal conversion performance. Summary of the Invention

[0003] This invention addresses the problems existing in the prior art by providing two crystalline materials with photothermal conversion properties, their preparation methods, and applications.

[0004] Tetrathiofulvalene (TTF) and its derivatives are stable and reversible two-electron materials that play a crucial role in constructing charge transfer (CT) functional materials, serving as excellent electron donors. Furthermore, naphthalenediimide (NDI) has a low least unoccupied molecular orbital (LUMO) energy and a large planar π-system, making it an excellent electron acceptor. Simultaneously, its derivatives often exhibit efficient light absorption over a wide spectral range, enabling the full utilization of light energy at different wavelengths for photothermal conversion and improving photothermal conversion efficiency. Therefore, we selected the TTF derivative 4,4',4",4""-((2,2'-bis(1,3-dithiacyclopenten-2-ylidene))-4,4',5,5'-tetrayl)tetrabenzoic acid (H4TTFTB) and the NDI derivative 2,7-bis(pyridin-4-yl)pyrene-1,3,6,8(2H,7H)-tetraone (DPNI) into a single system. This allows for better induction of extensive absorption in the near-infrared (NIR) region when the charge is transferred from the electron donor (TTF) to the acceptor (NDI) unit, thus enabling the development of MOFs with near-infrared photothermal conversion properties.

[0005] The first technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a cadmium crystal material with photothermal conversion properties is named TTFDPNI-Cd-MOF. This crystal belongs to the orthorhombic crystal system, space group Pbca, and its molecular structural formula is [Cd2(TTFTB)(DPNI)(H2O)2]·2H2O, and its chemical formula is Cd2C 58 H 36 N4O 16 S4, chemical formula weight 1398, unit cell parameters α = β = γ = 90°; the asymmetric unit of this crystal includes half of the TTFTB that has lost a proton. 4- Half of a DPNI molecule, one Cd 2+ One coordinated water molecule and one guest water molecule ( Figure 1 ); Center Cd 2+ The ion adopts a six-coordinate octahedral configuration, with four oxygen atoms derived from three TTFTB atoms. 4- The carboxyl group of the ligand One oxygen atom comes from a coordinated water molecule, and one nitrogen atom comes from the pyridine nitrogen atom of the ligand DPNI. ( Figure 2 ); structural units are linked by ligand carboxyl and pyridyl groups to form a three-dimensional network structure. Figure 3 The crystal structure exhibits face-to-face π-π packing interactions, with a spacing between the packing planes of π / 2.

[0006] The second technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: the cobalt crystal material with photothermal conversion properties is named TTFDPNI-Co-MOF. This crystal belongs to the monoclinic crystal system, the space group is P21 / n, and its molecular structure formula is [Co2(TTFTB)(DPNI). 0.5 [(H2O)(DMF)], with the chemical formula Co2C 49 H 31 N3O 12 S4, chemical formula weight 1099.91, unit cell parameters α = γ = 90°, β = 112.224°; the asymmetric unit cell of this crystal includes a deprotonated TTFTB. 4- Ligand, half of a DPNI molecule, two Co 2+ An ion, consisting of a coordinated water molecule and a coordinated DMF molecule ( Figure 4 ); Center Co(1) 2+ The ion adopts a six-coordinate octahedral configuration, with four oxygen atoms derived from TTFTB. 4- The carboxyl group of the ligand One oxygen atom comes from the carbonyl group of DMF, and another oxygen atom comes from a coordinated water molecule; while Co(2)2+ The ion also adopts a six-coordinate octahedral configuration, with five oxygen atoms derived from TTFTB. 4- The carboxyl group of the ligand One nitrogen atom comes from the pyridine nitrogen atom of the DPNI ligand. Structural units are linked in different directions through ligands to form a three-dimensional network structure. Figure 5 The crystal structure exhibits face-to-face π-π packing interactions, with a spacing between the packing planes of π / 2.

[0007] The present invention also provides a method for preparing the crystalline material, the method comprising the following steps:

[0008] Preparation method of Scheme 1: Weigh ligand H4TTFTB, DPNI and cadmium salt into a reaction flask, add NN dimethylacetamide (DMF), acetonitrile and deionized water, sonicate for 5 min, heat in an oven at 85-95℃ for 3 days, cool to room temperature at a rate of 5℃ / h at the end, filter, wash with ethanol, dry at 60℃ to obtain brown-black needle-like crystals.

[0009] The molar ratio of the ligands H4TTFTB, DPNI and Cd(II) ions is 1:1:2;

[0010] Preparation method of scheme 2: Weigh ligand H4TTFTB, DPNI and cobalt salt into a reaction flask, add NN dimethylformamide, methanol and deionized water, heat in an oven at 75-85℃ for 3 days, cool to room temperature at a rate of 5℃ / h at the end, filter, wash with ethanol, and dry at 60℃ to obtain brown block crystals.

[0011] The molar ratio of the ligands H4TTFTB, DPNI and Co(II) ions is 1:1:4;

[0012] The H4TTFTB ligand is an abbreviation for 4,4',4",4""-((2,2'-bis(1,3-dithiacyclopenten-2-ylidene))-4,4',5,5'-tetramethyl)tetrabenzoic acid, with the molecular formula C 34 H 20 S4O8, with a molecular weight of 684.78, has the following structural formula (Ⅰ):

[0013]

[0014] The DPNI ligand is an abbreviation for 2,7-bis(pyridin-4-yl)pyrene-1,3,6,8(2H,7H)-tetraone, with the molecular formula C. 24 H 12N4O4, with a molecular weight of 420.38, has the following structural formula (II):

[0015]

[0016] The cadmium salt is one or more of the following: cadmium nitrate tetrahydrate Cd(NO3)2·4H2O, cadmium acetate dihydrate Cd(CH3COO)2·2H2O, and cadmium dichloride dihydrate CdCl2·2.5H2O.

[0017] The cobalt salt is one or more of the following: cobalt dichloride hexahydrate CoCl2·6H2O, cobalt nitrate hexahydrate Co(NO3)2·6H2O, and cobalt acetate tetrahydrate Co(CH3COO)2·4H2O.

[0018] The DMF is N,N'-dimethylformamide;

[0019] All substances or solvents participating in the reaction are chemically pure.

[0020] Furthermore, the present invention also provides applications for the two framework materials, MOFs with photothermal conversion properties constructed based on TTF and NDI derivative ligands, in 808nm laser (0.7W cm⁻¹) -2 Under illumination, the temperature of TTFDPNI-Cd-MOF increased from room temperature to 230℃ within 5 seconds, reaching a maximum of 254℃, with a photothermal conversion efficiency of 47.5%. The temperature of TTFDPNI-Co-MOF increased from room temperature to 221℃ within 5 seconds, reaching a maximum of 230℃, with a photothermal conversion efficiency of 39.4%. Furthermore, the temperature change showed a linear relationship with the laser power, indicating that both TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF possess good thermal control. In addition, tests were conducted under 808nm laser (0.5W cm⁻¹) illumination. -2 Thermal stability tests were conducted. Under repeated laser on / off cycles of continuous irradiation of both crystalline materials: TTFDPNI-Cd-MOF rapidly increased in temperature from room temperature to 210℃, and TTFDPNI-Co-MOF rapidly increased in temperature from room temperature to 184℃. After 9 cycles, the samples did not decompose, and the heating rate and achievable maximum temperature remained unchanged. These results demonstrate that both TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF possess good stability. Under 1 unit of sunlight intensity, TTFDPNI-Cd-MOF rapidly increased in temperature from room temperature to 93℃ within 5 minutes, achieving an evaporation efficiency of 96.8% and an evaporation rate of 1.78 kg m³. -2 h- 1In comparison, TTFDPNI-Co-MOF achieved an evaporation efficiency of 89.3% and an evaporation rate of 1.54 kg m³ at 60°C under the same conditions. -2 h- 1 .

[0021] The formula for calculating evaporation efficiency is μ = mh LV / C opt Po, where:

[0022] μ represents evaporation efficiency;

[0023] m = evaporation mass;

[0024] h LV = Total enthalpy of liquid-gas phase transition, including endothermic and vaporization enthalpy (h LV =Q + Δvap), where Q = the energy required to heat the system from the initial temperature T to the final temperature T, and Δvap = the heat of vaporization of water;

[0025] Copt = Optical Concentration Ratio;

[0026] Po = Nominal solar radiation value, typically 1.0 kWm -2 .

[0027] Compared with the prior art, the present invention is characterized by:

[0028] This invention selects H4TTFTB and DPNI as ligands to interact with different metal ions, specifically Cd. 2+ and Co 2+ Two MOF (Metal-Organic Fire-Fuel) crystal materials were synthesized. The stacking of electron-donating and electron-accepting units in the organic ligands was controlled by the coordination mode between metal ions and ligands, inducing different interactions between ligand units (including charge transfer interactions and π-π stacking interactions). Different crystal structures and different interactions between ligand units have different effects on the photothermal conversion performance of the crystal materials; a specific structure determines specific properties. The TTFDPNI-Cd-MOF crystal material prepared in this invention exhibits high performance at 0.7 W / cm². -2 The highest temperature reached under illumination was 254℃, while under the same conditions, the highest temperature of the TTFDPNI-Co-MOF crystal material reached 230℃. The prepared TTFDPNI-Cd-MOF crystal material exhibits excellent photothermal conversion performance for solar-driven water evaporation, with an evaporation efficiency of 96.8% and an evaporation rate of 1.78 kg m³. -2 h-1, as a photothermal conversion material, has broad application prospects in fields such as seawater desalination and wastewater purification. Attached Figure Description

[0029] Figure 1This is the asymmetric structural unit of the TTFDPNI-Cd-MOF crystal material of the present invention;

[0030] Figure 2 The Cd in the TTFDPNI-Cd-MOF crystal material of this invention 2+ The coordination environment diagram is shown in the figure, with guest water molecules omitted for clarity.

[0031] Figure 3 This is a three-dimensional packing diagram of the TTFDPNI-Cd-MOF crystal material of the present invention. Hydrogen atoms and guest water molecules are omitted for clarity.

[0032] Figure 4 This is the asymmetric structural unit of the TTFDPNI-Co-MOF crystal material of the present invention;

[0033] Figure 5 This is a three-dimensional packing diagram of the TTFDPNI-Co-MOF crystal material of the present invention;

[0034] Figure 6 Thermogravimetric spectra of the TTFDPNI-Co-MOF and TTFDPNI-Cd-MOF crystal materials prepared in this invention;

[0035] Figure 7 The cyclic voltammetry spectra of the TTFDPNI-Co-MOF and TTFDPNI-Cd-MOF crystal materials prepared in this invention are shown.

[0036] Figure 8 The solid ultraviolet-visible-near-infrared absorption spectra of the TTFDPNI-Co-MOF and TTFDPNI-Cd-MOF crystal materials prepared in this invention are shown.

[0037] Figure 9 The photothermal conversion curves of the TTFDPNI-Cd-MOF crystal material of this invention under different near-infrared laser intensities are shown below.

[0038] Figure 10 The photothermal conversion curves of the TTFDPNI-Co-MOF crystal material of this invention under different near-infrared laser intensities are shown below.

[0039] Figure 11 The TTFDPNI-Cd-MOF crystal material of this invention is in 0.5W cm -2 Photothermal cycling curves under laser intensity;

[0040] Figure 12 The TTFDPNI-Co-MOF crystal material of this invention is in 0.5W cm -2 Photothermal cycling curves under laser intensity;

[0041] Figure 13 Water evaporation curves of the TTFDPNI-Co-MOF and TTFDPNI-Cd-MOF crystal materials prepared in this invention under one solar irradiance;

[0042] Figure 14 Temperature variation curves of the TTFDPNI-Co-MOF and TTFDPNI-Cd-MOF crystal materials prepared in this invention under one solar irradiance. Detailed Implementation

[0043] Example 1 of TTFDPNI-Cd-MOF preparation:

[0044] Ligands H4TTFTB (6.85 mg, 0.01 mmol), DPNI (4.20 mg, 0.01 mmol), and Cd(NO3)2·4H2O (6.16 mg, 0.02 mmol) were weighed and placed in a 10 mL reaction flask. 0.75 mL of NN dimethylacetamide (DMF), 0.5 mL of acetonitrile, and 0.5 mL of deionized water were added. The mixture was sonicated for 5 min, heated in a 95 °C oven for 3 days, and then cooled to room temperature at a rate of 5 °C / h. The mixture was filtered, washed with ethanol, and dried at 60 °C to obtain brownish-black needle-like crystals, which are the TTFDPNI-Cd-MOF crystal material.

[0045] Example 2 of TTFDPNI-Cd-MOF preparation:

[0046] Ligand H4TTFTB (6.85 mg, 0.01 mmol), DPNI (4.20 mg, 0.01 mmol), and cadmium acetate dihydrate Cd(CH3COO)2·2H2O (5.32 mg, 0.02 mmol) were weighed and placed in a 10 mL reaction flask. 1.5 mL of NN dimethylacetamide, 1.0 mL of acetonitrile, and 1.0 mL of deionized water were added. The mixture was sonicated for 5 min, heated in an oven at 85 °C for 3 days, and then cooled to room temperature at a rate of 5 °C / h. The mixture was filtered, washed with ethanol, and dried at 60 °C to obtain brownish-black needle-like crystals, which are the TTFDPNI-Cd-MOF crystal material.

[0047] Example 3 of TTFDPNI-Cd-MOF preparation:

[0048] Ligand H4TTFTB (6.85 mg, 0.01 mmol), DPNI (4.20 mg, 0.01 mmol), and cadmium dichloride (CdCl2·2.5H2O) (4.56 mg, 0.02 mmol) were weighed and placed in a 10 mL reaction flask. 1.5 mL of N,N dimethylacetamide, 1.0 mL of acetonitrile, and 1.0 mL of deionized water were added. The mixture was sonicated for 5 min, heated in a 90 °C oven for 3 days, and then cooled to room temperature at a rate of 5 °C / h. The mixture was filtered, washed with ethanol, and dried at 60 °C to obtain brownish-black needle-like crystals, which are the TTFDPNI-Cd-MOF crystal material.

[0049] Example 4 of TTFDPNI-Co-MOF preparation:

[0050] Ligands H4TTFTB (6.85 mg, 0.01 mmol), DPNI (4.20 mg, 0.01 mmol), and CoCl2·6H2O (9.42 mg, 0.04 mmol) were weighed and placed in a 10 mL reaction flask. 0.6 mL of N,N-dimethylformamide, 0.4 mL of ethanol, and 0.4 mL of deionized water were added. The mixture was heated in an oven at 75 °C for 3 days. At the end of the reaction, the mixture was cooled to room temperature at a rate of 5 °C / h. The mixture was filtered, washed with ethanol, and dried at 60 °C to obtain brown blocky crystals, which are the TTFDPNI-Co-MOF crystal material.

[0051] Example 5 of TTFDPNI-Co-MOF preparation

[0052] Ligands H4TTFTB (6.85 mg, 0.01 mmol), DPNI (4.20 mg, 0.01 mmol), and Co(NO3)2·6H2O (11.64 mg, 0.04 mmol) were weighed and placed in a 10 mL reaction flask. 1.2 mL of N,N-dimethylformamide, 0.8 mL of ethanol, and 0.8 mL of deionized water were added. The mixture was heated in an oven at 85 °C for 3 days, and then cooled to room temperature at a rate of 5 °C / h at the end of the reaction. The mixture was filtered, washed with ethanol, and dried at 60 °C to obtain brown blocky crystals, which is the TTFDPNI-Co-MOF crystal material.

[0053] Example 6 of TTFDPNI-Co-MOF preparation:

[0054] Ligand H4TTFTB (6.85 mg, 0.01 mmol), DPNI (4.20 mg, 0.01 mmol), and cobalt acetate tetrahydrate Co(CH3COO)2·4H2O (9.96 mg, 0.04 mmol) were weighed and placed in a 10 mL reaction flask. 0.6 mL of N,N dimethylformamide, 0.4 mL of ethanol, and 0.4 mL of deionized water were added. The mixture was heated in an oven at 80 °C for 3 days. At the end of the reaction, the mixture was cooled to room temperature at a rate of 5 °C / h. The mixture was filtered, washed with ethanol, and dried at 60 °C to obtain brown blocky crystals, which are the TTFDPNI-Co-MOF crystal materials.

[0055] Characterization of the TTFDPNI-Cd-MOF prepared in Example 1 by single-crystal X-ray diffraction showed that the crystal belongs to the orthorhombic crystal system, space group Pbca, and its molecular structural formula is [Cd2(TTFTB)(DPNI)(H2O)2]·2H2O, with the chemical formula Cd2C. 58 H 36 N4O 16 S4, chemical formula weight 1398, unit cell parameters α = β = γ = 90°; the asymmetric unit of this crystal includes half of the TTFTB that has lost a proton. 4- Half of a DPNI molecule, one Cd 2+ One coordinated water molecule and one guest water molecule ( Figure 1 ); Center Cd 2+ The ion adopts a six-coordinate octahedral configuration, with four oxygen atoms derived from three TTFTB atoms. 4- The carboxyl group of the ligand One oxygen atom comes from a coordinated water molecule, and one nitrogen atom comes from the pyridine nitrogen atom of the ligand DPNI. ( Figure 2 ); structural units are linked by ligand carboxyl and pyridyl groups to form a three-dimensional network structure. Figure 3 The crystal structure exhibits face-to-face π-π packing interactions, with a spacing between the packing planes of π / 2.

[0056] Characterization of the TTFDPNI-Co-MOF prepared in Example 1 by single-crystal X-ray analysis showed that the crystal belongs to the monoclinic crystal system, space group P21 / n, and its molecular structural formula is [Co2(TTFTB)(DPNI). 0.5 [(H2O)(DMF)], with the chemical formula Co2C 49 H 31 N3O 12 S4, chemical formula weight 1099.91, unit cell parameters α = γ = 90°, β = 112.224°; the asymmetric unit cell of this crystal includes a deprotonated TTFTB. 4- Ligand, half of a DPNI molecule, two Co 2+ An ion, consisting of a coordinated water molecule and a coordinated DMF molecule ( Figure 4 ); Center Co(1) 2+ The ion adopts a six-coordinate octahedral configuration, with four oxygen atoms derived from TTFTB. 4- The carboxyl group of the ligand One oxygen atom comes from the carbonyl group of DMF, and another oxygen atom comes from a coordinated water molecule; while Co(2) 2+ The ion also adopts a six-coordinate octahedral configuration, with five oxygen atoms derived from TTFTB. 4- The carboxyl group of the ligand One nitrogen atom comes from the pyridine nitrogen atom of the DPNI ligand. Structural units are linked in different directions through ligands to form a three-dimensional network structure. Figure 5 The crystal structure exhibits face-to-face π-π packing interactions, with a spacing between the packing planes of π / 2.

[0057] Thermogravimetric analysis (TGA) Figure 6 The results show that both TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF crystal materials prepared in Example 1 exhibit excellent thermal stability, with a 15% mass loss at 100–200 °C, attributed to the loss of guest molecules. TTFDPNI-Cd-MOF collapses at 360 °C. TTFDPNI-Co-MOF prepared in Example 1 exhibits enhanced thermal resistance, maintaining structural stability at 400 °C. Within the 200–400 °C thermal stability window, its structure remains intact and stable during repeated thermal cycling, while also maintaining good charge transfer characteristics.

[0058] Cyclic voltammetry was used to test the redox properties of two crystalline materials prepared in Example 1: TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF. Figure 7 As shown: Both crystalline materials retain the characteristic two-step redox behavior (TTF / TTF) of the tetrathiofulvalene (TTF) ligand. + and TTF + / TTF 2+The differences in their formal potentials indicate that the redox properties of the materials are affected by their different compositions and structures. TTFDPNI-Cd-MOF exhibits a higher current response and a sharper redox peak, while TTFDPNI-Co-MOF shows a broader peak and a weakened current at high scan rates. These differences are determined by their different compositions and structures, thus determining their unique electrochemical and photothermal properties.

[0059] Solid-state UV-Vis-NIR absorption spectroscopy results show that ( Figure 8 The main absorption peaks of the two crystalline materials prepared in Example 1, TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF, are concentrated in the wavelength range of 400–760 nm. Both materials exhibit an absorbance of 1.2, indicating strong absorption in the visible light spectrum within this range. In the ultraviolet (UV) range of 200–400 nm, the absorbance increases with wavelength. Above 700 nm in the near-infrared and infrared regions, the absorbance gradually decreases and stabilizes, reaching a stable value of approximately 0.8 at 1000 nm. TTFDPNI-Cd-MOF exhibits higher and more stable absorbance in the near-infrared region above 700 nm, indicating that it can absorb more photons in this spectral region, effectively converting them into heat energy and providing a continuous energy input for water evaporation. In contrast, TTFDPNI-Co-MOF has slightly lower absorbance and exhibits an absorption valley in the near-infrared region, indicating weaker light-harvesting efficiency.

[0060] To further investigate the photothermal conversion capabilities of the two crystalline materials, TTFDPNI-Cd-MOF prepared in Example 1 and TTFDPNI-Co-MOF prepared in Example 2, infrared thermal imaging technology was used to measure the photothermal conversion capabilities of the materials in the range of 0.1 to 1.1 W / cm². -2 The temperature changes of TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF under 808nm laser irradiation were tested at different power densities. TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF exhibited different temperature rise curves at 0.7W / cm². -2 Under irradiation, the TTFDPNI-Cd-MOF rapidly increased from ambient temperature to 230℃ within 5 seconds, reaching a maximum temperature of 254℃, with a photothermal conversion efficiency of 47.5%. Figure 9 In contrast, TTFDPNI-Co-MOF achieved a temperature rise from room temperature to 221°C within the same timeframe, with a maximum temperature of 230°C and a photothermal conversion efficiency of 39.4%. Figure 10 ).

[0061] The cycling stability of the TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF crystal materials prepared in Example 1 and Example 2, respectively, was tested under cyclic on / off irradiation. No decomposition of the crystal materials was observed after nine consecutive cycles, indicating that both TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF crystal materials have excellent cycling stability. Figure 11 , Figure 12 ).

[0062] The solar-driven water evaporation performance of two crystalline materials, TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF, was tested as photothermal conversion materials. A polyvinylidene fluoride (PVDF) film was precisely cut to match the diameter of the beaker opening, allowing it to float on the water surface when placed on a supporting foam. Subsequently, the crystalline material was uniformly deposited on the PVDF film. The light intensity was precisely calibrated using a xenon lamp equipped with a power meter. The mass changes of the two crystalline materials, TTFDPNI-Cd-MOF and TTFDPNI-Co-MOF prepared in Example 1, were recorded. Figure 13 ) and temperature change ( Figure 14 Under 1 solar irradiance, the temperature of TTFDPNI-Cd-MOF rapidly increased from room temperature to 93°C within 5 minutes, achieving an evaporation efficiency of 96.8% and an evaporation rate of 1.78 kg m³. -2 h-1. In comparison, under the same conditions, TTFDPNI-Co-MOF achieved a temperature of 60℃, an evaporation efficiency of 89.3%, and an evaporation rate of 1.54 kg m³. -2 h-1.

Claims

1. A cadmium crystal material with photothermal conversion properties, characterized in that, The cadmium crystal material is named TTFDPNI-Cd-MOF. This crystal belongs to the orthorhombic crystal system, space group Pbca, and its molecular structural formula is [Cd₂(TTFTB)(DPNI)(H₂O)₂]·2H₂O, with the chemical formula Cd₂C₂. 58 H 36 N4O 16 S4, chemical formula weight 1398, unit cell parameters α = β = γ = 90°; the asymmetric unit of this crystal includes half of the TTFTB that has lost a proton. 4- Half of a DPNI molecule, one Cd 2+ One coordinated water molecule and one guest water molecule; the central Cd 2+ The ion adopts a six-coordinate octahedral configuration, with four oxygen atoms derived from TTFTB. 4- The ligand's carboxyl group and one oxygen atom originate from a coordinated water molecule, while the nitrogen atom comes from the pyridine nitrogen atom of the ligand DPNI. The structural units are linked by ligand carboxyl and pyridine groups to form a three-dimensional network structure. Face-to-face π-π stacking interactions exist in the crystal structure, with an interplanar spacing of [missing information].

2. A cobalt crystal material with photothermal conversion properties, characterized in that, The cobalt crystal material is named TTFDPNI-Co-MOF. This crystal belongs to the monoclinic crystal system, with space group P21 / n, and its molecular structural formula is [Co2(TTFTB)(DPNI). 0.5 [(H2O)(DMF)], with the chemical formula Co2C 49 H 31 N3O 12 S4, chemical formula weight 1099.91, unit cell parameters α = γ = 90°, β = 112.224°; the asymmetric unit cell of this crystal includes a deprotonated TTFTB. 4- Ligand, half of a DPNI molecule, two Co 2+ An ion consisting of a coordinated water molecule and a coordinated DMF molecule; the central Co(1) 2+ The ion adopts a six-coordinate octahedral configuration, with four oxygen atoms derived from TTFTB. 4- The carboxylate group of the ligand has one oxygen atom from the carbonyl group of DMF and one oxygen atom from the coordinated water molecule; Co(2) 2+ The ion also adopts a six-coordinate octahedral configuration, with five oxygen atoms derived from TTFTB. 4- The ligand's carboxyl group contains one nitrogen atom derived from the pyridine nitrogen atom of the DPNI ligand; the structural units are linked in different directions through the ligands to form a three-dimensional network structure, exhibiting face-to-face π-π stacking interactions in the crystal structure, with an interplanar spacing of [missing information].

3. The method for preparing a cadmium crystal material with photothermal conversion properties according to claim 1, characterized in that, The preparation method includes the following steps: Weigh ligands H4TTFTB, DPNI and cadmium salt into a reaction flask, add NN dimethylacetamide (DMF), acetonitrile and deionized water, sonicate for 5 min, heat in an oven at 85-95℃ for 3 days, cool to room temperature at a rate of 5℃ / h at the end, filter, wash with ethanol, dry at 60℃ to obtain brown-black needle-like crystals. The molar ratio of the ligands H4TTFTB, DPNI, and Cd(II) ions is 1:1:

2.

4. The method for preparing a cobalt crystal material with photothermal conversion properties according to claim 2, characterized in that, The preparation method includes the following steps: Weigh out ligands H4TTFTB, DPNI and cobalt salt and place them in a reaction flask. Add NN dimethylformamide, methanol and deionized water. Heat in an oven at 75-85℃ for 3 days. At the end, cool to room temperature at a rate of 5℃ / h. Filter, wash with ethanol, and dry at 60℃ to obtain brown blocky crystals. The molar ratio of the ligands H4TTFTB, DPNI, and Co(II) ions is 1:1:

4.

5. The use of the crystalline material according to claim 1 or 2, characterized in that, TTFDPNI-Cd-MOF or TTFDPNI-Co-MOF crystal materials have excellent photothermal conversion properties and can be used as photothermal conversion materials in the fields of seawater desalination and wastewater purification.

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