Preparation method and application of pyrene-based metal-organic framework two-dimensional ultrathin nanosheet
Two-dimensional ultrathin nanosheets of pyrene-based metal-organic frameworks were directly synthesized by a surfactant-free solvothermal method, which solved the problem of active sites being masked during the preparation process in existing technologies and achieved highly efficient photocatalytic water splitting for hydrogen production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-16
AI Technical Summary
Existing technologies struggle to efficiently prepare large-size, ultrathin two-dimensional metal-organic framework nanosheets, and surfactants are difficult to completely remove during the preparation process, affecting the exposure of catalytic active sites and photocatalytic efficiency.
Two-dimensional ultrathin nanosheets of pyrene-based metal-organic frameworks were synthesized using a surfactant-free solvothermal method. By controlling the solvothermal reaction conditions, nanosheets with a thickness of less than 3 nm and a size in the micrometer range were directly synthesized, avoiding the use of surfactants.
The prepared nanosheets effectively shorten the carrier transfer path, significantly improve the performance of photocatalytic water splitting for hydrogen production, and increase catalytic efficiency.
Smart Images
Figure CN119591894B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic materials technology, specifically relating to a method for preparing and applying two-dimensional ultrathin nanosheets of pyrene-based metal-organic frameworks. Background Technology
[0002] Compared to bulk or single-crystal materials, two-dimensional materials with large dimensions and atomic or molecular thickness and high aspect ratios possess unique physical and chemical properties. Two-dimensional nanomaterials occupy an important position in applications such as separation, optoelectronics, and catalysis. In recent years, two-dimensional (2D) metal-organic framework (MOF) nanosheets, as new members of the two-dimensional family, have attracted considerable attention due to their tunable structure and function, large specific surface area, and ultra-high porosity, leading to rapid development in related research in the fields of chemistry and materials science. Compared to 3D bulk MOF crystals, 2D ultrathin MOF nanosheets possess high catalytic active sites and large surface area, which is beneficial for ensuring rapid mass transfer and high catalytic activity. These properties endow 2D ultrathin MOF nanosheets with enormous application potential in catalysis, energy storage, and electronic sensors.
[0003] In recent years, methods for preparing two-dimensional nanosheets have been synthesized and developed, including top-down and bottom-up methods. Top-down methods involve ultrasonically exfoliating layered bulk MOFs to obtain nanosheets; however, this method often suffers from morphological damage, recombination, low yield, and limitations applicable only to MOFs with weak interlayer interactions. Bottom-up methods for directly synthesizing MOF nanosheets, such as surfactant-assisted synthesis and interface-assisted synthesis strategies, are preferred for preparing MOF nanosheets with high yields and good dispersion. However, low yields and the difficulty in completely removing introduced surfactants, leading to the masking of catalytic active sites, negatively impact the photocatalytic process. Therefore, there is an urgent need for a method for directly synthesizing large-size, surfactant-free, universally applicable, and large-scale production of ultrathin 2D MOF nanosheets. Summary of the Invention
[0004] The purpose of this invention is to propose a method for preparing and applying pyrene-based metal-organic framework (MOF) two-dimensional ultrathin nanosheets, in order to solve the problems existing in the current nanosheet preparation process, such as difficulty in achieving large size, ultrathin thickness, complete exposure of active sites, low yield, and low photocatalytic efficiency of the prepared nanosheets. The 2D ultrathin MOF nanosheets prepared by this invention have micron-sized dimensions and surfactant-free surfaces, which can effectively shorten the transfer path of charge carriers from the bulk phase to the surface, while exposing a larger specific surface area, significantly improving the performance of photocatalytic water splitting for hydrogen production.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0006] In a first aspect, the present invention provides a method for preparing two-dimensional ultrathin nanosheets of pyrene-based metal-organic frameworks, comprising the following steps:
[0007] (1) Disperse the 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) ligand and the metal salt in an organic solvent or a mixed solution of organic solvent and deionized water, and stir until homogeneous;
[0008] (2) Add the ligand solution obtained in step (1) dropwise to the metal salt solution while stirring, and stir until homogeneous;
[0009] (3) The mixed solution obtained in step (2) is placed into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 100-140°C for 3-24 hours. After cooling, the mixture is centrifuged, washed, and freeze-dried to obtain two-dimensional ultrathin nanosheet powder.
[0010] Based on the above technical solution, the metal salts mentioned in step (1) further include chlorides, nitrates, sulfates, acetates and hydrates of Mn, Co, Cd and Ni.
[0011] Based on the above technical solution, the metal salts mentioned in step (1) further include MnCl4, Co(NO3)2, Cd(NO3)2, NiCl2 and their hydrates.
[0012] Based on the above technical solution, further, in step (1), the molar ratio of the metal atom of the metal salt to the 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) ligand is 5:1 to 1:1, and the concentration of the 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) ligand is 0.1 to 10 mmol / L. -1 The concentration of the metal salt is 0.1–20 mmol / L. -1 .
[0013] Based on the above technical solution, further, the organic solvent mentioned in step (1) includes N,N-dimethylformamide and N,N-diethylformamide, and the volume ratio of organic solvent to water in the mixed solution is 64:1 to 16:1.
[0014] Based on the above technical solution, further, the stirring time in steps (1) and (2) is 20 to 40 minutes.
[0015] Based on the above technical solution, further, in step (3), the reaction temperature is 110℃~130℃ and the reaction time is 3h~8h.
[0016] Based on the above technical solution, further, in step (3), the centrifugation speed is 5000-8000 r / min, the centrifugation time is 2-3 min, the solvent used for washing is N,N-dimethylformamide and acetonitrile, N,N-dimethylformamide is used for washing 1-4 times, acetonitrile is used for washing 1-4 times, and the freeze drying is specifically liquid nitrogen freeze drying.
[0017] Secondly, the present invention provides a pyrene-based metal-organic framework two-dimensional ultrathin nanosheet prepared by the above preparation method.
[0018] Based on the above technical solution, the thickness of the pyrene-based metal-organic framework two-dimensional ultrathin nanosheet is 1-3 nm, and the size is 1-6 μm.
[0019] Thirdly, the present invention provides the application of the above-mentioned pyrene-based metal-organic framework two-dimensional ultrathin nanosheets in photocatalytic water splitting for hydrogen production.
[0020] Based on the above technical solution, the application is further described as follows: the pyrene-based metal-organic framework two-dimensional ultrathin nanosheets are added to a mixed solution of acetonitrile, water and ascorbic acid, H2PtCl6 aqueous solution is added, the mixture is transferred into a sealed reactor, vacuum is applied, and Pt co-catalyst is photodeposited using a 100-500W xenon lamp (λ≥420nm) as the light source, followed by photocatalytic water splitting to produce hydrogen.
[0021] Based on the above technical solution, the amount of the pyrene-based metal-organic framework two-dimensional ultrathin nanosheets added is 10-30 mg, and the mixed solution for photocatalytic water splitting to produce hydrogen is composed of 1000-2000 μL of water, 50-150 mL of MeCN and 25-45 mg of ascorbic acid.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] 1. This invention directly synthesizes a series of pyrene-based MOF two-dimensional ultrathin nanosheets via a solvothermal method without regulator control. This method requires no regulator, has mild conditions, is simple to prepare, highly reproducible, and has strong universality. The synthesized ultrathin two-dimensional MOF nanosheets have a thickness of less than 3 nm and have a micron-sized structure.
[0024] 2. The method used in this invention does not require the addition of surfactants, thus avoiding masking the exposed active sites.
[0025] 3. The ultrathin 2D MOF nanosheets prepared by this invention can effectively shorten the transfer path of charge carriers from the bulk phase to the surface, and significantly improve the performance of photocatalytic water splitting to produce hydrogen. Attached image description:
[0026] Figure 1The images shown are SEM (a), TEM (b), AFM (c), and XRD (d) images of the Mn-TBAPy-UTNS two-dimensional ultrathin nanosheets prepared in Example 1.
[0027] Figure 2 The images shown are SEM (a), AFM (b), and XRD (c) images of Co-TBAPy-UTNS prepared in Example 2.
[0028] Figure 3 The images shown are SEM (a), AFM (b), and XRD (c) images of the Cd-TBAPy-UTNS prepared in Example 3.
[0029] Figure 4 The images shown are SEM (a), AFM (b), and XRD patterns (c) of the Ni-TBAPy-UTNS prepared in Example 4.
[0030] Figure 5 This is the photocatalytic water splitting and hydrogen production reaction activity of Mn-TBAPy-UTNS two-dimensional ultrathin nanosheets in Example 6. In this figure, a is the hydrogen production rate result of ultrathin two-dimensional nanosheets and bulk sample, and b is the hydrogen production time curve result of Mn-TBAPy-UTNS two-dimensional ultrathin nanosheets.
[0031] Figure 6 The electrochemical impedance spectroscopy (a) and fluorescence spectrum (b) of the Mn-TBAPy-UTNS two-dimensional ultrathin nanosheets tested in Examples 7 and 8 are shown. Detailed implementation method:
[0032] The present invention will now be described in detail with reference to examples and accompanying drawings, but the embodiments of the present invention are not limited thereto.
[0033] Example 1
[0034] This embodiment provides a method for preparing Mn-TBAPy-UTNS two-dimensional ultrathin nanosheets, specifically including the following steps:
[0035] 1,3,6,8-tetra(4-carboxyphenyl)pyrene H4TBAPy ligand (5 mg) and MnCl4·4H2O (2.3 mg) were placed in two 25 mL beakers, and DMF (8 mL) was added to each beaker. The mixture was stirred for 30 min, and then the ligand solution was added dropwise to the metal salt solution and stirred for another 30 min. The solution was poured into a stainless steel reactor with a 25 mL polytetrafluoroethylene liner and then transferred to a temperature-controlled oven. The temperature was raised to 120 °C and held for 6 h. After cooling to room temperature, the mixture was centrifuged, washed with DMF and acetonitrile, and freeze-dried to obtain a fluffy yellow powder named Mn-TBAPy-UTNS.
[0036] Figure 1 Image a shows a SEM image of the Mn-TBAPy-UTNS prepared in this example. The nanosheets have micron-sized dimensions and are extremely thin. Figure 1 b is the TEM image of Mn-TBAPy-UTNS. Figure 1 c is an AFM image of Mn-TBAPy-UTNS, showing that the thickness of the nanosheet is approximately 2.1 nm; Figure 1 d is a comparison of the XRD of Mn-TBAPy-UTNS with that of single crystal (SCIENCE CHINAChemistry, 2020, 63(12), 1756-1760.), which proves the successful preparation of nanosheets.
[0037] Example 2
[0038] This embodiment provides a method for preparing Co-TBAPy-UTNS two-dimensional ultrathin nanosheets, specifically including the following steps:
[0039] 1,3,6,8-tetra(4-carboxyphenyl)pyrene H4TBAPy ligand (10 mg) and Co(NO3)2·6H2O (5.5 mg) were placed in two 25 mL beakers, respectively. DEF (7.75 mL) and water (0.25 mL) were added to each beaker, and the mixture was stirred for 30 min. The solution containing the ligand was then added dropwise to the metal salt solution, and the mixture was stirred for another 30 min. The solution was then poured into a stainless steel reactor lined with 25 mL of polytetrafluoroethylene and transferred to a temperature-controlled oven. The temperature was raised to 120 °C and held for 6 h. The mixture was then allowed to cool naturally to room temperature, centrifuged, washed with DMF and acetonitrile, and freeze-dried to obtain a fluffy yellow powder, which was named Co-TBAPy-UTNS.
[0040] Figure 2 Image a shows a SEM image of the Co-TBAPy-UTNS fabricated in this example. The nanosheets have micron-sized dimensions and are extremely thin. Figure 2 b shows an AFM image of Mn-TBAPy-UTNS, indicating that the thickness of the nanosheets is approximately 1.7 nm; Figure 1 c is a comparison of the XRD patterns of Co-TBAPy-UTNS and single crystals (Journal of Solid State Chemistry, 285, 121252.), which proves the successful preparation of nanosheets.
[0041] Example 3
[0042] This embodiment provides a method for preparing Cd-TBAPy-UTNS two-dimensional ultrathin nanosheets, specifically including the following steps:
[0043] 3.4 mg of 1,3,6,8-tetra(4-carboxyphenyl)pyrene H4TBAPy ligand and 4.6 mg of Cd(NO3)2·4H2O were placed in two 25 mL beakers, and 8 mL of DMF and 0.5 mL of H2O were added to each beaker, respectively. The mixtures were then stirred for 30 min. Next, the ligand solution was added dropwise to the metal salt solution, and the mixture was stirred for another 30 min. The solution was then poured into a stainless steel reactor lined with 25 mL of polytetrafluoroethylene and transferred to a temperature-controlled oven. The temperature was raised to 120 °C and held for 6 h. The mixture was then allowed to cool naturally to room temperature, centrifuged, washed with DMF and acetonitrile, and freeze-dried to obtain a fluffy yellow powder, which was named Cd-TBAPy-UTNS.
[0044] Figure 3 Image a shows a SEM image of the Cd-TBAPy-UTNS prepared in this example. The nanosheets have micron-sized dimensions and are extremely thin. Figure 2 b is an AFM image of Cd-TBAPy-UTNS, showing that the thickness of the nanosheets is approximately 1.5 nm; Figure 1 c is a comparison of the XRD pattern of Cd-TBAPy-UTNS with that of a single crystal (Advanced Materials, 2018, 30, 1803401), which shows the successful preparation of nanosheets.
[0045] Example 4
[0046] This embodiment provides a method for preparing Ni-TBAPy-UTNS two-dimensional ultrathin nanosheets, specifically including the following steps:
[0047] 1,3,6,8-tetra(4-carboxyphenyl)pyrene H4TBAPy ligand (10 mg) and NiCl2·6H2O (2.6 mg) were placed in two 25 mL beakers, respectively. A mixed solvent of DMF (7.5 mL) and water (0.5 mL) was added to each beaker, and the mixture was stirred for 30 min. Next, the solution containing the ligand was added dropwise to the metal salt solution, and the mixture was stirred for another 30 min. The solution was then poured into a stainless steel reactor with a 25 mL polytetrafluoroethylene liner, and then transferred to a temperature-controlled oven. The temperature was raised to 120 °C and held for 6 h. After cooling to room temperature, the mixture was centrifuged, washed with DMF and acetonitrile, respectively, and freeze-dried to obtain a fluffy yellow powder, which was named Ni-TBAPy-NS.
[0048] Figure 4 Image a shows a SEM image of the Ni-TBAPy-UTNS fabricated in this example. The nanosheets have micron-sized dimensions and are extremely thin. Figure 4 b is an AFM image of Ni-TBAPy-UTNS, showing that the thickness of the nanosheet is approximately 1.2 nm; Figure 4c is a comparison of the XRD of Ni-TBAPy-UTNS with that of single crystal (Journal of the American Chemical Society, 2022, 144(6), 2747-2754.), which proves the successful preparation of nanosheets.
[0049] Example 5
[0050] This embodiment provides the deposition of the Mn-TBAPy-UTNS and Mn-TBAPy-SC (SCIENCE CHINAChemistry, 2020, 63(12), 1756-1760.) cocatalysts prepared in Example 1, specifically including the following steps:
[0051] Weigh 20 mg of the sample and place it in a reactor containing 1500 μL of water, 100 mL of acetonitrile, and 35 mg of ascorbic acid (AA) sacrificial agent, using the same solvent as the photocatalytic reaction. Add 60 μL of a 1 mg / mL solution. -1 Pt-loaded Mn-TBAPy nanosheets (denoted as "Pt / Mn-TBAPy-UTNS and Pt / Mn-TBAPy-SC") can be obtained by depositing a chloroplatinic acid (H2PtCl6) aqueous solution in a sealed reactor under vacuum for 1 hour under full-spectrum irradiation with a 300W xenon lamp as the light source.
[0052] Example 6
[0053] This embodiment provides an experiment on the photocatalytic water splitting to generate hydrogen from Mn-TBAPy-SC single crystals and Mn-TBAPy-UTNS ultrathin nanosheets: 20 mg of catalyst powder (Mn-TBAPy-UTNS and Mn-TBAPy-SC) was dispersed in a mixed solution of 1500 μL water, 100 mL acetonitrile, and 35 mg ascorbic acid (AA), and the same volume percentage of 1 mg / mL was added. -1 The reaction solution was prepared as an aqueous solution of H2PtCl6. The solution was then transferred to a 400 mL Pyrex reactor, which was sealed. A circulating cooling system was activated to maintain the reaction temperature at 15°C, and a vacuum pump was connected for 15 minutes to ensure complete removal of air from the reactor. Following the procedure in Example 5, a 0.3% Pt co-catalyst was first photodeposited, followed by photocatalytic water splitting experiments. A top-irradiation method was used, employing a 300W xenon lamp (λ≥420nm) as the light source. Samples were taken every 1 hour, and the amount of hydrogen produced was detected using gas chromatography.
[0054] The results are as follows Figure 5 As shown, from Figure 5It can be seen that the photocatalytic water splitting rate of Pt / Mn-TBAPy-UTNS for hydrogen production is an order of magnitude higher than that of single-crystal Pt / Mn-TBAPy-SC.
[0055] Example 7
[0056] This embodiment provides electrochemical impedance spectroscopy (EIS) testing of Mn-TBAPy-UTNS and Mn-TBAPy-SC: 5 mg of Mn-TBAPy-UTNS powder and Mn-TBAPy-SC were weighed and ultrasonically dispersed in 0.5 mL of anhydrous methanol solution containing 0.05% Nafin. Then, 10 μL of the dispersed suspension was dropped onto a 0.25 cm⁻¹ plate. 2 Air-dried on FTO. Then dried naturally. -1 EIS was tested in a sodium sulfate solution. The reference electrode was an Ag / AgCl electrode, and the counter electrode was a platinum sheet electrode. The EIS test process potential was 0.6V vs RHE, and the frequency was 0.1~1000HZ.
[0057] Figure 6 a presents the experimental results from EIS, showing that Mn-TBAPy-UTNS has a smaller charge transfer resistance and better charge separation capability than Mn-TBAPy-SC.
[0058] Example 8
[0059] Fluorescence spectroscopy (PL) testing: The tests were performed using powder samples (Mn-TBAPy-UTNS and Mn-TBAPy-SC) at an excitation wavelength of 375 nm.
[0060] Figure 6 b shows the fluorescence spectroscopy (PL) results of Mn-TBAPy-UTNS and Mn-TBAPy-SC, indicating that Mn-TBAPy-SC has a stronger fluorescence intensity than Mn-TBAPy-UTNS.
Claims
1. A method for preparing two-dimensional ultrathin nanosheets of pyrene-based metal-organic frameworks, characterized in that, Includes the following steps: (1) Disperse the 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) ligand and the metal salt in an organic solvent or a mixed solution of organic solvent and deionized water, and stir until homogeneous; (2) Add the ligand solution obtained in step (1) dropwise to the metal salt solution while stirring, and stir until homogeneous; (3) The mixed solution obtained in step (2) is placed into a stainless steel reactor with a polytetrafluoroethylene liner and heated at 100~140°C. o The reaction was carried out at C for 3-24 h, and after cooling, centrifugation, washing, and freeze-drying were performed to obtain two-dimensional ultrathin nanosheet powder. The metal salts mentioned in step (1) include chlorides, nitrates, sulfates, acetates and hydrates of Mn, Co, Cd and Ni; the molar ratio of the metal atoms of the metal salts to the 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) ligands is 5:1 to 1:
1. The organic solvents mentioned in step (1) include N,N-dimethylformamide and N,N-diethylformamide, and the volume ratio of organic solvent to water in the mixed solution is 64:1 to 16:
1.
2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPy) ligand is 0.1–10 mmol / L. -1 The concentration of the metal salt is 0.1~20 mmol / L. -1 .
3. The preparation method according to claim 1, characterized in that, The stirring time in steps (1) and (2) is 20 to 40 minutes.
4. The preparation method according to claim 1, characterized in that, The reaction temperature in step (3) is 110°C. o C~130 o C, the reaction time is 3 h to 8 h.
5. The preparation method according to claim 1, characterized in that, In step (3), the centrifugation speed is 5000~8000 r / min, the centrifugation time is 2~3 min, the washing solvent is N,N-dimethylformamide and acetonitrile, N,N-dimethylformamide is used for washing 1~4 times, acetonitrile is used for washing 1~4 times, and the freeze drying is specifically liquid nitrogen freeze drying.
6. Two-dimensional ultrathin nanosheets of pyrene-based metal-organic frameworks prepared by the preparation method according to any one of claims 1-5.
7. The pyrene-based metal-organic framework two-dimensional ultrathin nanosheets according to claim 6, characterized in that, The pyrene-based metal-organic framework two-dimensional ultrathin nanosheets have a thickness of 1~3 nm and a size of 1~6 μm.
8. The application of the pyrene-based metal-organic framework two-dimensional ultrathin nanosheets as described in claim 6 or 7 in photocatalytic water splitting for hydrogen production.