Anthraquinone-based MOF photocatalytic material and preparation method and application thereof

Abstract

The application discloses an anthraquinone-based MOF photocatalytic material and a preparation method and application thereof. The anthraquinone-based MOF photocatalytic material is obtained by a solvothermal reaction of a ligand DPAq and a nickel source in a mixed solvent; wherein the ligand DPAq is 2,6-bis(pyrazol-4-yl)-9,10 anthraquinone, and the mixed solvent is a combination of N,N-dimethylformamide and water. The anthraquinone-based MOF photocatalytic material disclosed by the application shows a suitable band gap and a good ROS generation efficiency, and shows excellent catalytic activity and selectivity when applied to a benzylamine coupling reaction, wherein the reaction selectivity reaches 100%, the product yield can reach 97%, the catalytic reaction efficiency is high; and the anthraquinone-based MOF photocatalytic material can be recycled, and the product yield can still reach 92% after being recycled for 5 times.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photocatalytic materials, and particularly relates to an anthraquinone-based MOF photocatalytic material and a preparation method and application thereof. BACKGROUND

[0002] Imines are used as intermediates and active building blocks in drug synthesis. Imines are usually prepared by condensation between amines and carbonyl compounds, which usually requires an unstable aldehyde as a starting material, a Lewis acid catalyst and a dehydrating agent. However, the reaction has poor selectivity and functional group tolerance, and the post-treatment purification process is complex, which requires removal of by-products, dehydrating agents and catalyst residues. Considering the wide use of imines as biologically active compounds, selective aerobic oxidation of amines to imines is a key reaction for laboratory and commercial applications. Therefore, it is necessary to develop a mild, green and sustainable method for synthesizing imines.

[0003] In recent years, visible light-induced transition metal catalyzed reactions not only eliminate the trouble of noble metal complexes, but also do not need to use additional photosensitizers. The combination of catalyst and substrate occurs in coordination with the process of photo-induced single electron transfer (SET), which reduces the temperature at which the redox process occurs, thereby activating organic molecules with high redox potential, which is sometimes not achieved by typical photo-redox catalysts. From the concept of green and sustainable development, it is essential to develop high-catalytic activity, green and recyclable non-noble metal heterogeneous catalysts.

[0004] Metal-organic frameworks (MOFs) are a class of porous crystalline materials self-assembled by metal ions / clusters and organic linkers. MOFs have high porosity, high adsorption, large specific surface area and rich active sites, and have become important materials for energy and environment related applications, especially in the field of heterogeneous photocatalysis. Visible light-driven photo-redox transformation is often used to prepare high-value-added organic compounds due to its unique advantages such as mild conditions and green sustainability. Molecular oxygen (O2) as an economically abundant oxidant has received more and more attention in organic synthesis. For example, a photocatalyst capable of absorbing visible light and generating electron-hole pairs can convert O2 into reactive oxygen species (ROS) through single electron transfer (SET) and energy transfer (ET) processes, and the obtained ROS further interact with substrate molecules to perform oxidative transformation.

[0005] Organic photosensitizers can be integrated into the MOF framework as building blocks. For example, anthraquinone units are known for their photonic absorption efficiency. Anthraquinone compounds are the most numerous among various natural quinone compounds, are important dyes and pharmaceutical intermediates, and are substances with good optical activity. Due to their high photosensitivity, high triplet state energy and relatively long triplet state lifetime, they are widely used as organic photocatalysts to participate in organic photocatalytic reactions. Their electron-accepting properties make these substances have the potential to transfer electrons in reactions, so anthraquinone compounds can be used as active ligands in the field of photocatalysis. For example, the invention patent with publication number CN116371471A discloses a photosensitive MOF catalyst material with large hexagonal channels obtained by coordination self-assembly of photosensitive ligands and transition metal nitrate, which has high catalytic activity when used for photocatalytic reduction of CO2. For example, the invention patent with publication number CN117700766A discloses an anthraquinone-based two-dimensional MOF photocatalyst and its preparation method and application. The photocatalyst is synthesized by coordinating 2,6-bis((E)-2-(pyridin-4-yl)vinyl)anthracene-9,10-dione as a functional ligand with auxiliary carboxylic acid and metal Zn(II) ion, wherein the auxiliary carboxylic acid is 5-methyl isophthalic acid, isophthalic acid or 5-fluoro isophthalic acid. The MOF photocatalyst has high selectivity and high yield for photocatalytic benzylamine and its derivative self-coupling reaction, wherein the reaction selectivity is 100% and the product yield can reach 98.24%. The catalytic reaction efficiency is high and can be recycled multiple times. However, there is no related report on using anthraquinone photosensitive ligand to construct Ni8-MOF material and using it for photocatalytic benzylamine self-coupling reaction to prepare imine compounds. SUMMARY

[0006] The technical problem to be solved by the present application is to provide an anthraquinone-based MOF photocatalytic material with high catalytic reaction efficiency and its preparation method and application.

[0007] The first object of the present application is to provide an anthraquinone-based MOF photocatalytic material, which is obtained by solvothermal reaction of ligand DPAq and nickel source in a mixed solvent; wherein the ligand DPAq is 2,6-bis(pyrrole-4-yl)-9,10 anthraquinone, and the mixed solvent is a combination of N,N-dimethylformamide and water.

[0008] The aforementioned anthraquinone-based MOF photocatalyst is a yellow-brown powder. The nickel source used in the above scheme is Ni(OAc)₂·4H₂O; in the composition of the mixed solvent, the volume ratio of N,N-dimethylformamide to water is preferably 1–10:1, more preferably 3–5:1. The ligand DPAq and the nickel source can be directly dissolved in the mixed solvent and then subjected to a solvothermal reaction, or the ligand DPAq and the nickel source can be dissolved separately in N,N-dimethylformamide and water, and the resulting two solutions can be mixed before the solvothermal reaction. Regardless of the method used, the preferred ratio of the amount of nickel source to the amount of water in the mixed solvent is 7–10 mg:1 mL, and the preferred ratio of the amount of ligand DPAq to the amount of N,N-dimethylformamide in the mixed solvent is 1–3 mg:1 mL. The solvothermal reaction is usually carried out at ≥100°C, more preferably at 140–160°C; when the reaction is carried out at 140–160°C, the reaction time is preferably controlled at 10–12 h.

[0009] The second objective of this invention is to provide a method for preparing the above-mentioned anthraquinone-based MOF photocatalytic material, comprising: dissolving ligand DPAq and nickel source in N,N-dimethylformamide and water, respectively, mixing the two solutions and then carrying out a solvothermal reaction to obtain the material.

[0010] In the preparation method of the anthraquinone-based MOF photocatalytic material described above, the selection of the nickel source and the solvothermal reaction parameters are as previously described. N,N-dimethylformamide and water constitute the aforementioned mixed solvent in the preparation method, and the ratio of N,N-dimethylformamide to water, and their relationship with the amounts of DPAq and the nickel source, are the same as described above. The ratio of ligand DPAq to the nickel source is a stoichiometric ratio; in one specific embodiment, the molar ratio of ligand DPAq to the nickel source is 3:4.

[0011] The third objective of this invention is to provide an anthraquinone-based MOF photocatalytic material crystal, which is octahedral in shape and belongs to the cubic crystal system. Space group, cell parameters are: α = 90.00°, β = 90.00°, γ = 90.00°. The anthraquinone-based MOF photocatalytic material has a nickel ion with a positive divalent charge at its crystal metal center. The MOF framework consists of an inorganic secondary building unit (SBU) and a Ni8 cluster, which are connected to 12 DPAq linkers to form a three-dimensional porous framework with octahedral and tetrahedral cavities.

[0012] The fourth object of the present application is to provide a preparation method of the anthraquinone-based MOF photocatalytic material crystal, comprising: placing ligand DPAq and a nickel source in a mixed solvent, adjusting the pH of the system to be acidic, reacting under heating conditions, cooling the reaction solution, and precipitating crystals to obtain the product; wherein the ligand DPAq is 2,6-bis(pyrazol-4-yl)-9,10-anthraquinone, and the mixed solvent is a combination of N,N-dimethylformamide and water.

[0013] In the preparation method of the anthraquinone-based MOF photocatalytic material crystal, an organic acid or an inorganic acid is used to adjust the pH of the system to be acidic, such as nitric acid, hydrochloric acid, or sulfuric acid, and preferably dilute nitric acid (such as 0.2-0.3 mol / L) is used for adjustment. Preferably, the pH of the system is adjusted to 4.0-6.5, and more preferably the pH of the system is adjusted to 4.0-5.0. In the preparation method of the crystal, the heating reaction is preferably carried out at ≥100℃, and more preferably at 110-130℃; when the reaction is carried out at 110-130℃, the reaction time is preferably controlled to 60-96 h. The selection of the nickel source and the ratio of the mixed solvent involved in the preparation method are the same as described above.

[0014] The fifth object of the present application is to provide the application of the anthraquinone-based MOF photocatalytic material or the anthraquinone-based MOF photocatalytic material crystal in the photocatalytic benzylamine self-coupling reaction to prepare imine compounds.

[0015] In the present application, the structure of the ligand DPAq is shown in the following formula (1):

[0016]

[0017] The ligand DPAq can be prepared according to the existing literature (Wu K, Liu X-Y, Cheng P-W, et al. Linker Engineering for Reactive Oxygen Species Generation Efficiency in Ultra-Stable Nickel-Based Metal–Organic Frameworks [J]. Journal of the American Chemical Society, 2023, 145(34): 18931-8.). Specifically, 2,6-dibromoanthraquinone and 1-THP-4-pyrazole boronic acid pinacol ester (1-(2-Tetrahydropyranyl)-1H-pyrazole-4-boronic acid pinacol ester) are placed in a combination of an organic solvent and water, a catalyst is added, the system is adjusted to weak alkaline, and the reaction is carried out under the protection of an inert atmosphere (such as nitrogen, helium, etc.). The reaction product is filtered, and the filter cake is subjected to silica gel column chromatography to obtain an intermediate product. The tetrahydropyranyl protecting group of the obtained intermediate product is deprotected to obtain the ligand DPAq.

[0018] In the above method for preparing the ligand DPAq, the organic solvent is preferably N,N-dimethylformamide, N,N-dimethylacetamide, 1,4 dioxane or acetonitrile, and the volume ratio of the organic solvent to water is preferably 3-5:1. The catalyst is preferably tetrakis(triphenylphosphine)palladium. The system is adjusted to weak alkaline by using a basic substance (such as potassium carbonate, sodium carbonate, sodium bicarbonate or triethylamine, etc.), and the pH of the system is preferably adjusted to 8.0-9.0. The heating reaction is preferably carried out at 100-120°C, and the reaction time is usually controlled at 48-72h. When the silica gel column chromatography is used for purification, the developing agent used is a combination of petroleum ether and ethyl acetate, and the volume ratio of petroleum ether to ethyl acetate is preferably 1:1. The tetrahydropyranyl protecting group of the obtained intermediate product is deprotected by using a conventional method, such as placing the obtained intermediate product in ethanol and removing the tetrahydropyranyl protecting group of the obtained intermediate product under acidic conditions. The removal is usually carried out by heating to 60-80°C under air environment for 8-12h. In this method, the mass ratio of 2,6-dibromoanthraquinone to 1-THP-4-pyrazole boronic acid pinacol ester is usually 1:2-3, and the mass ratio of 1-THP-4-pyrazole boronic acid pinacol ester to the organic solvent is preferably 1g:15-25mL. The amount of the catalyst is preferably 0.15-0.25 times the mass of 1-THP-4-pyrazole boronic acid pinacol ester.

[0019] Compared with the prior art, the anthraquinone-based MOF photocatalytic material is constructed by coordinating Ni8 cluster and 2,6-bis(pyrazol-4-yl)-9,10-anthraquinone, and the anthraquinone-based MOF photocatalytic material is constructed by the application. The test results of the applicant show that the anthraquinone-based MOF photocatalytic material exhibits a suitable band gap and good ROS generation efficiency, and exhibits excellent catalytic activity and selectivity when applied to a benzylamine coupling reaction, wherein the reaction selectivity is 100%, the product yield can reach 97%, the catalytic reaction efficiency is high; and the anthraquinone-based MOF photocatalytic material can be recycled, and the product yield can still reach 92% after being recycled for 5 times. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The infrared spectrum of the ligand prepared in Example 1 is shown in FIG. 1, wherein (a) is the infrared spectrum of the ligand DPAq prepared in Example 1, and (b) is the infrared spectrum of the MOF photocatalytic material GXMZU106 prepared in Example 1. 1 H and 13 C nuclear magnetic resonance spectrum, wherein (a) is the 1 H nuclear magnetic resonance spectrum, (b) is the 13 C nuclear magnetic resonance spectrum.

[0021] Figure 2 The infrared spectrum of the ligand H2pbp prepared in Comparative Example 1 is shown in FIG. 2, wherein (a) is the infrared spectrum of the ligand H2pbp prepared in Comparative Example 1, and (b) is the infrared spectrum of the MOF photocatalytic material GXMZU104 prepared in Comparative Example 1. 1 H and 13 C nuclear magnetic resonance spectrum, wherein (a) is the 1 H nuclear magnetic resonance spectrum, (b) is the 13 C nuclear magnetic resonance spectrum.

[0022] Figure 3 The infrared spectrum of the ligand prepared in Comparative Example 2 is shown in FIG. 3, wherein (a) is the infrared spectrum of the ligand DPA prepared in Comparative Example 2, and (b) is the infrared spectrum of the MOF photocatalytic material GXMZU105 prepared in Comparative Example 2. 1 H and 13 C nuclear magnetic resonance spectrum, wherein (a) is the 1 H nuclear magnetic resonance spectrum, (b) is the 13 C nuclear magnetic resonance spectrum.

[0023] Figure 4 The infrared spectrum of the ligand and MOF photocatalytic material, GXMZU105 and GXMZU106 prepared in Example 1, Comparative Examples 1 and 2 is shown in FIG. 4, wherein (a) is the infrared spectrum of the ligand H2pbp and the MOF photocatalytic material GXMZU104 prepared in Comparative Example 1, (b) is the infrared spectrum of the ligand DPA and the MOF photocatalytic material GXMZU105 prepared in Comparative Example 2, and (c) is the infrared spectrum of the ligand DPAq and the MOF photocatalytic material GXMZU106 prepared in Example 1.

[0024] Figure 5 The XRD diagram of GXMZU104, GXMZU105 and GXMZU106 respectively prepared in Example 1, Comparative Examples 1 and 2 is shown in FIG. 5.

[0025] Figure 6The solid UV-Vis diffuse reflection spectra of GXMZU104, GXMZU105 and GXMZU106 prepared in Example 1, Comparative Example 1 and 2, respectively.

[0026] Figure 7 The EIS spectra of GXMZU104, GXMZU105 and GXMZU106 prepared in Example 1, Comparative Example 1 and 2, respectively.

[0027] Figure 8 The photocurrent response curves of GXMZU104, GXMZU105 and GXMZU106 prepared in Example 1, Comparative Example 1 and 2, respectively.

[0028] Figure 9 The XPS spectra of GXMZU106 prepared in Application Example 1 before and after the photocatalytic benzylamine self-coupling reaction cycle.

[0029] Figure 10 The crystal structure diagram of the anthraquinone-based MOF photocatalytic material crystal prepared in Example 2.

[0030] Figure 11 The SEM and EDS diagrams of the anthraquinone-based MOF photocatalytic material crystal prepared in Example 2.

[0031] Figure 12 The yield and selectivity results diagram of GXMZU106 photocatalytic benzylamine self-coupling reaction for 5 cycles in Application Example 1. DETAILED DESCRIPTION

[0032] In order to better explain the technical solutions of the present application, the present application will be further described in detail below in combination with examples, but the embodiments of the present application are not limited thereto.

[0033] Example 1: Preparation of anthraquinone-based MOF photocatalytic material

[0034] (1) Preparation of functional ligand:

[0035]

[0036] To 1 g of 2,6-dibromoanthraquinone and 2.7184 g of 1-THP-4-pyrazole boronic acid pinacol ester in N,N-dimethylformamide (45 mL) and water (16 mL), 1.052 g of anhydrous K2CO3 and 0.4396 g of Pd(PPh3)4 were added, and the reaction was stirred at 110°C under a nitrogen atmosphere for 48 h. After the reaction was completed, the reaction mixture was cooled to room temperature, 50 mL of saturated aqueous sodium chloride solution was added, and the solid was completely precipitated and then filtered. The yellow solid obtained was purified by silica gel column chromatography (petroleum ether: ethyl acetate = 1:1, by volume) to obtain an intermediate product. The tetrahydropyran protecting group of the obtained intermediate product was deprotected by placing the intermediate product in 50 mL of ethanol and adding 25 mL of hydrochloric acid (1.0 mol / L). The mixture was stirred at 80°C for 10 h, cooled to room temperature, filtered, and the precipitate was washed with ethanol and then added to a beaker containing 100 mL of distilled water. The pH was adjusted to 5.0-7.0 with sodium hydroxide (aq, 0.5 mol / L), and the mixture was filtered, and the filter cake was washed with distilled water until it was neutral, and then rinsed with a small amount of ethanol and ethyl ether to obtain a bright yellow solid (labeled as Ligand DPAq) with a yield of 88%.

[0037] (2) Preparation of anthraquinone-based MOF photocatalytic material: 33 mg of Ligand DPAq was dissolved in 16 mL of N,N-dimethylformamide, and 31.8 mg of Ni(OAc)2·4H2O was dissolved in 4 mL of water. Then the two solutions were mixed and subjected to a solvothermal reaction in a reaction kettle at 150°C until completion (about 9 h). After the reaction was completed, the mixture was cooled to room temperature, and a solid was precipitated. The solid was collected and washed with solvents N,N-dimethylformamide, ethanol, and ethyl ether, and then dried under vacuum to obtain an anthraquinone-based MOF photocatalytic material (brownish yellow powder, labeled as GXMZU106, GXMZU = Guangxi University for Nationalities) with a yield of 65%.

[0038] Preparation of biphenyl-based MOF photocatalytic material

[0039] (1) Preparation of functional ligand:

[0040]

[0041] Into a 100 mL round bottom flask, 0.5 g of 4,4'-dibromo-1,1'-biphenyl and 1.783 g of 1-THP-4-pyrazoleboronic acid pinacol ester were dissolved in N,N-dimethylformamide (38 mL) and water (9.5 mL), 0.8859 g of anhydrous K2CO3 and 0.3704 g of Pd(PPh3)4 were added, and the reaction was stirred at 110°C under a nitrogen atmosphere for 48 h. After the reaction was completed, the reaction mixture was cooled to room temperature, 50 mL of saturated aqueous sodium chloride solution was added, and the solid was completely precipitated and then filtered. The obtained dark gray solid was purified by silica gel column chromatography (petroleum ether: ethyl acetate = 1:1, by volume), and the tetrahydropyran protecting group of the obtained intermediate was deprotected. Specifically, the obtained intermediate was dissolved in 50 mL of ethanol, 25 mL of hydrochloric acid (1.0 mol / L) was added, and the reaction was stirred at 80°C for 10 h. After cooling to room temperature, the precipitate was filtered and washed with ethanol, and then added to a beaker containing 100 mL of distilled water. The pH was adjusted to 5.0-7.0 with sodium hydroxide (aq, 0.5 mol / L), and the filtrate was washed with distilled water until it was neutral, and then rinsed with a small amount of ethanol and ethyl ether to obtain a blue-gray solid (denoted as ligand H2pbp) with a yield of 72%.

[0042] (2) Preparation of MOF photocatalytic material: 33 mg of ligand H2pbp was dissolved in 16 mL of N,N-dimethylformamide, and 37.9 mg of Ni(OAc)2·4H2O was dissolved in 4 mL of water. Then the two solutions were mixed and subjected to a solvothermal reaction in a reaction kettle at 150°C until completion (about 9 h). After the reaction was completed, the mixture was cooled to room temperature, and a solid was precipitated. The solid was collected and washed with solvents N,N-dimethylformamide, ethanol and ethyl ether, and then dried under vacuum to obtain a biphenyl MOF photocatalytic material (gray powder, denoted as GXMZU104, GXMZU = Guangxi University for Nationalities), with a yield of 70%.

[0043] Preparation of anthracene-based MOF photocatalytic material

[0044] (1) Preparation of functional ligand:

[0045]

[0046] A mixture of 0.5 g of 2,6-dibromoanthracene and 1.656 g of 1-THP-4-pyrazole boronic acid pinacol ester was placed in N,N-dimethylformamide (36 mL) and water (9 mL), 0.823 g of anhydrous K2CO3 and 0.344 g of Pd(PPh3)4 were added, and the reaction was stirred at 110°C under a nitrogen atmosphere for 48 h. After the reaction was completed, the reaction mixture was cooled to room temperature, 50 mL of a saturated aqueous sodium chloride solution was added, and the solid was completely precipitated and then filtered. The resulting yellow solid was purified by column chromatography on silica gel (petroleum ether: ethyl acetate = 1:1, by volume) to obtain an intermediate product. The tetrahydropyran protecting group of the obtained intermediate product was deprotected by placing the intermediate product in 50 mL of ethanol, adding 25 mL of hydrochloric acid (1.0 mol / L), and stirring at 80°C for 10 h. After cooling to room temperature, the mixture was filtered, and the precipitate was washed with ethanol and then added to a beaker containing 100 mL of distilled water. The pH was adjusted to 5.0-7.0 (in this case, the pH was adjusted to 7.0) with sodium hydroxide (aq, 0.5 mol / L), and the mixture was filtered. The filter cake was washed with distilled water until it was neutral, and then it was rinsed with a small amount of ethanol and diethyl ether to obtain a light yellow solid (labeled as Ligand DPA) with a yield of 85%.

[0047] (2) Preparation of MOF photocatalytic material: 30 mg of Ligand DPA was dissolved in 16 mL of N,N-dimethylformamide, and 31.8 mg of Ni(OAc)2·4H2O was dissolved in 4 mL of water. The two solutions were then mixed, and a solvothermal reaction was performed in a reaction kettle at 150°C until completion (about 9 h). After the reaction was completed, the mixture was cooled to room temperature, and a solid was precipitated. The solid was collected and washed with solvents such as N,N-dimethylformamide, ethanol, and diethyl ether, and then dried under vacuum to obtain an anthracene-based MOF photocatalytic material (dark brown, labeled as GXMZU105, GXMZU = Guangxi University for Nationalities) with a yield of 57%.

[0048] Preparation of anthraquinone-based MOF photocatalytic material

[0049] Example 1 was repeated, except that acetonitrile was used instead of N,N-dimethylformamide in step (2).

[0050] No solid was precipitated after the solvothermal reaction was completed and the mixture was cooled to room temperature, so an anthraquinone-based MOF photocatalytic material was not prepared in this case.

[0051] Preparation of anthraquinone-based MOF photocatalytic material

[0052] Example 1 was repeated, except that Ni(NO3)2·6H2O was used instead of Ni(OAc)2·4H2O in step (2).

[0053] After the solvent thermal reaction is completed and cooled to room temperature, no solid is precipitated, so no anthraquinone-based MOF photocatalytic material is prepared in this example.

[0054] The ligands and MOF photocatalytic materials prepared in the above-mentioned example 1 and comparative examples 1 and 2 are characterized and analyzed, and the results are as follows:

[0055] 1. Nuclear magnetic resonance hydrogen spectrum, carbon spectrum

[0056] The ligands prepared in example 1 and comparative examples 1-2 are respectively characterized by nuclear magnetic resonance, wherein:

[0057] The nuclear magnetic hydrogen spectrum and carbon spectrum spectrum of the ligand prepared in example 1 are as shown in Figure 1 From Figure 1 it can be determined that the ligand DPAq prepared in example 1 is determined as 2,6-bis(pyrazol-4-yl)-9,10 anthraquinone.

[0058] The nuclear magnetic hydrogen spectrum and carbon spectrum spectrum of the ligand prepared in comparative example 1 are as shown in Figure 2 From Figure 2 it can be determined that the ligand H2pbp prepared in comparative example 1 is determined as 4,4′-di(1H-pyrazol-4-yl)-1,1′-biphenyl.

[0059] The nuclear magnetic hydrogen spectrum and carbon spectrum spectrum of the ligand prepared in comparative example 2 are as shown in Figure 3 From Figure 3 it can be determined that the ligand DPA prepared in comparative example 2 is determined as 2,6-bis(pyrazol-4-yl)-9,10 anthraquinone.

[0060] 2. Infrared spectrum analysis

[0061] The ligands and photocatalytic materials GXMZU104, GXMZU105 and GXMZU106 prepared in example 1 and comparative examples 1-2 are respectively characterized and analyzed by infrared spectrometer, and the characterization results are as shown in Figure 4 From Figure 4 (c), it can be known that GXMZU106 contains the characteristic peak of the anthraquinone part C=O of the ligand at 1670-1678 cm -1 , and the pyrazole peak of the three Ni8-MOFs compared with the ligand disappears at about 3000-3300 cm -1 , which preliminarily indicates the synthesis of the complex (i.e. MOF photocatalytic material) from the infrared spectrum.

[0062] 3. PXRD analysis

[0063] GXMZU104, GXMZU105 and GXMZU106 prepared in example 1 and comparative examples 1-2 are respectively characterized and analyzed by X-ray powder diffractometer (PXRD), and the characterization results are as shown in Figure 5 FromFigure 5 It can be seen that the PXRD of GXMZU106 is consistent with its simulated PXRD results. At the same time, the PXRD results of GXMZU104 and GXMZU105 are consistent with those of GXMZU106, indicating that the crystal coordination structure of GXMZU104 and GXMZU105 is the same as that of GXMZU106. Furthermore, GXMZU106 maintains high crystallinity and structural integrity even after boiling in 7 mol / L NaOH for 24 h, indicating its chemical stability.

[0064] 4. Ultraviolet-Visible Diffuse Reflectance Analysis

[0065] Solid-state UV-Vis diffuse reflectance analysis was performed on GXMZU104, GXMZU105, and GXMZU106 prepared in Example 1 and Comparative Examples 1-2, respectively. The analysis results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the absorption edge of GXMZU106 is greater than 700nm, indicating that GXMZU106 has the ability to capture visible light and shows strong electron acceptance ability.

[0066] 5. Electrochemical impedance analysis

[0067] Electrochemical impedance spectroscopy (EIS) was performed on GXMZU104, GXMZU105, and GXMZU106 prepared in Example 1 and Comparative Examples 1-2, respectively. The test results are as follows: Figure 7 As shown. By Figure 7 It can be seen that GXMZU106 has the lowest impedance, indicating that it has a lower charge transfer resistance, which is more conducive to charge transfer.

[0068] 6. Photocurrent response analysis

[0069] Photocurrent response analysis was performed on GXMZU104, GXMZU105, and GXMZU106 prepared in Example 1 and Comparative Examples 1-2, respectively. The analysis results are as follows: Figure 8 As shown. By Figure 8 It can be seen that the photocurrent response generated by GXMZU106 under visible light irradiation is much higher than that of the other two Ni8-MOFs, which indicates that the introduction of photoactive electron-withdrawing units into the system is indeed beneficial to improving charge separation efficiency.

[0070] 7. XPS Analysis

[0071] X-ray photoelectron spectroscopy (XPS) was used to characterize and analyze the GXMZU106 prepared in Example 1 before and after cycling to determine the elemental composition and stability of the MOFs. The characterization results are as follows: Figure 9 As shown. By Figure 9It can be seen that the prepared GXMZU106 sample contains Ni, O, C and N elements, and does not contain other impurity elements, which shows that the prepared sample is consistent with the elements obtained by crystal structure, and the elements before and after the cycle test are the same, which further proves the high stability of the material.

[0072] Example 2: Preparation of anthraquinone-based MOF photocatalytic material crystal

[0073] Take Ni(OAc)2·4H2O (5 mg, 0.025 mmol), ligand DPAq (6 mg, 0.02 mmol, prepared according to step (1) of Example 1) and N,N-dimethylformamide (1.5 mL) and water (0.50 mL) in a 10 mL glass container, adjust the pH of the system to 4.5 with dilute HNO3 (0.25 mol / L), then place the glass container in a 120°C environment for 72 h. After the reaction is completed, cool to room temperature at a rate of 5°C / h, and brown yellow octahedral crystals are precipitated. Collect the crystals, which are anthraquinone-based MOF photocatalytic material crystals, with a yield of 68%.

[0074] The anthraquinone-based MOF photocatalytic material crystal prepared in this example was subjected to X-ray single crystal diffraction (XRD) characterization and analysis, and the crystal structure thereof was obtained. The crystallographic data is shown in Table 1 below, and the crystal structure is shown in Figure 10 Figure 10 It can be seen that 8 Ni atoms are bridged by 4 μ4-OH and 2 μ4-OH2 oxygen to form a [Ni8(μ4-OH)4(μ4-OH2)2(Pz) 12 ] cluster, in which two N atoms of the same pyrazole coordinately cover two adjacent Ni atoms. The [Ni8(μ4-OH)4(μ4-OH2)2(Pz) 12 ] cluster is further connected with a linear bipyrazole to generate a three-dimensional porous framework with octahedral and tetrahedral cavities, which intuitively represents the synthesis of the complex and its coordination structure. At the same time, the SCXRD (X-ray single crystal diffraction) analysis of the crystal obtained in this example shows that the crystal has symmetry.

[0075] Table 1 Crystallographic structure data of anthraquinone-based MOF photocatalytic material crystal

[0076]

[0077] a R1 = Σ||Fo|-|Fc|| / Σ|Fo|.

[0078] b wR2 = {Σ[w(Fo2-Fc2) 2 ] / [w(Fo2) 2 ​] 1 / 2, [Fo > 4s(Fo)].

[0079] The quinone-based MOF photocatalytic material crystal prepared in the embodiment is characterized and analyzed by using a scanning electron microscope (SEM) and energy spectrum analysis (EDS), and the characterization result is shown in FIG. 1. Figure 11 It can be known from FIG. 1 that the quinone-based MOF photocatalytic material crystal is an octahedral crystal, and C, O, Ni and N are uniformly distributed in the sample. Figure 11

[0080] Example 3: Preparation of an anthraquinone-based MOF photocatalytic material

[0081] The example 1 is repeated, except that:

[0082] In step (1), N,N-dimethylacetamide is used instead of N,N-dimethylformamide.

[0083] In step (2), the reaction temperature is changed to 140℃.

[0084] As a result, an anthraquinone-based MOF photocatalytic material in the form of yellow-brown powder is obtained. The yield is 23%.

[0085] Example 4: Preparation of an anthraquinone-based MOF photocatalytic material

[0086] The example 1 is repeated, except that:

[0087] In step (1), 1,4-dioxane is used instead of N,N-dimethylformamide, the amount of tetrakis(triphenylphosphine)palladium is changed to 0.2 times the amount of 1-THP-4-pyrazole boronic acid pinacol ester, and sodium bicarbonate is used to adjust the pH of the system to 7.0.

[0088] In step (2), the amount of N,N-dimethylformamide is changed to 20 mL, and the reaction temperature is changed to 160℃.

[0089] As a result, an anthraquinone-based MOF photocatalytic material in the form of yellow-brown powder is obtained. The yield is 39%.

[0090] Example 5: Preparation of an anthraquinone-based MOF photocatalytic material crystal

[0091] The example 2 is repeated, except that: the amount of N,N-dimethylformamide is changed to 1.0 mL, dilute sulfuric acid (0.2 mol / L) is used to adjust the pH of the system to 5.5, and the reaction is carried out at 140℃ for 48 h.

[0092] As a result, an anthraquinone-based MOF photocatalytic material crystal in the form of yellow-brown octahedron is obtained. The yield is 32%.

[0093] The crystal obtained in the embodiment is characterized and analyzed by using an X-ray single crystal diffractometer, and is determined to be the anthraquinone-based MOF photocatalytic material crystal according to the present application. ​

[0094] Application Example 1

[0095] 5 mg of GXMZU106 prepared in Example 1 and 10.92 μL (0.1 mmol) of benzylamine (C7H9N) were added to a quartz tube, followed by 4 mL of acetonitrile solution. The quartz tube was sealed, and oxygen was bubbled for 20 min. The mixture was then irradiated with a 500 W xenon lamp with a wavelength greater than 420 nm and reacted at room temperature for 6 h. After the reaction was complete, the catalyst was separated, and the product was collected. The product yield was determined by gas chromatography (GC), and the product was identified by nuclear magnetic resonance (NMR), yielding N-benzyl-1-phenylmethylimine (C7H9N). 14 H 13 N). Calculations showed that the yield of N-benzyl-1-phenylmethylimine was 97%, with a selectivity of 100%.

[0096] Material Application Analysis: After the photocatalytic reaction of GXMZU106 in Application Example 1 was completed, the catalyst GXMZU106 was centrifuged, washed, dried, and reused to catalyze fresh benzylamine. This cycle was repeated four times, yielding five yields of 97%, 95%, 95%, 94%, and 92%, with a selectivity of 100% in all cases. Figure 12 As shown. By Figure 12 It can be seen that after five cycles of experiments, the effect of GXMZU106 catalyzing the self-coupling of benzylamine remained stable. This cyclic experiment demonstrates that the anthraquinone-based MOF photocatalyst material of this invention has excellent stability, can be reused, and has good economic benefits.

[0097] Application Comparative Example 1

[0098] The only difference between this example and Application Example 1 is that the ligand DPAq prepared in step (1) of Example 1 is used instead of GXMZU106 as the catalyst.

[0099] The results showed that the product N-benzyl-1-phenylmethyleneimine (C) was obtained. 14 H 13 N). Calculations showed that the yield of N-benzyl-1-phenylmethylimine was 92%, with a selectivity of 100%.

[0100] Application Comparative Example 2

[0101] The only difference between this example and Application Example 1 is that GXMZU104 prepared in Comparative Example 1 is used instead of GXMZU106 as the catalyst.

[0102] The results showed that the product N-benzyl-1-phenylmethyleneimine (C) was obtained. 14 H 13 N). Calculations showed that the yield of N-benzyl-1-phenylmethylimine was 45%, with a selectivity of 100%.

[0103] Application Example 3

[0104] This example differs from Application Example 1 only in that GXMZU 105, prepared in Step (1) of Example 1, is used in place of GXMZU 106 as the catalyst.

[0105] The results show that the product N-(4-bromobenzyl)-l-(4-bromophenyl)formimidamide (C 14 H 13 N) is obtained. The yield of N-(4-bromobenzyl)-l-(4-bromophenyl)formimidamide is calculated to be 93% with a selectivity of 100%.

[0106] Application Example 2

[0107] This example differs from Application Example 1 only in that 4-fluorobenzylamine (C7H8FN) is used in place of benzylamine (C7H9N).

[0108] The results show that the product N-(4-fluorobenzyl)-l-(4-fluorophenyl)formimidamide (C 14 H 11 F2N) is obtained. The yield of N-(4-fluorobenzyl)-l-(4-fluorophenyl)formimidamide is calculated to be 91% with a selectivity of 87%.

[0109] Application Example 3

[0110] This example differs from Application Example 1 only in that 4-chlorobenzylamine (C7H8CIN) is used in place of benzylamine (C7H9N).

[0111] The results show that the product N-(4-chlorobenzyl)-l-(4-chlorophenyl)formimidamide (C 14 H 11 C l2 N) is obtained. The yield of N-(4-chlorobenzyl)-l-(4-chlorophenyl)formimidamide is calculated to be 94% with a selectivity of 100%.

[0112] Application Example 4

[0113] This example differs from Application Example 1 only in that 4-bromobenzylamine (C7H8BrN) is used in place of benzylamine (C7H9N).

[0114] The results show that the product N-(4-bromobenzyl)-l-(4-bromophenyl)formimidamide (C 14 H 11 Br2N) is obtained. The yield of N-(4-bromobenzyl)-l-(4-bromophenyl)formimidamide is calculated to be 93% with a selectivity of 100%.

[0115] Application Example 5

[0116] The difference between this example and the application example 1 is that 4- methoxybenzylamine (C8H10ON) is used instead of benzylamine (C7H9N).

[0117] The result shows that the product N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine (C 16 H 11 O2N) is obtained. The yield of N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine is calculated to be 97% and the selectivity is 100%.

[0118] Application Example 6

[0119] The difference between this example and the application example 1 is that 4- methoxybenzylamine (C8H10ON) is used instead of benzylamine (C7H9N). 11 N) is used instead of benzylamine (C7H9N).

[0120] The result shows that the product N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine (C 16 H 17 N) is obtained. The yield of N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine is calculated to be 97% and the selectivity is 100%.

[0121] Application Example 7

[0122] The difference between this example and the application example 1 is that 4- methoxybenzylamine (C8H10ON) is used instead of benzylamine (C7H9N). 11 ON) is used instead of benzylamine (C7H9N).

[0123] The result shows that the product N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine (C 16 H 17 O2N) is obtained. The yield of N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine is calculated to be 97% and the selectivity is 100%.

[0124] Application Example 8

[0125] The difference between this example and the application example 1 is that 4- methoxybenzylamine (C8H10ON) is used instead of benzylamine (C7H9N). 11 ON) is used instead of benzylamine (C7H9N).

[0126] The result shows that the product N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine (C 16 H 17 O2N) is obtained. The yield of N-(4-methoxybenzyl)-1-(4- methoxyphenyl) methanimine is calculated to be 97% and the selectivity is 100%.

[0127] Application Example 9

[0128] The difference between this example and the application example 1 is that 3- methoxybenzylamine (C8H9NO) is used instead of benzylamine (C7H9N). 11 ON) instead of benzylamine (C7H9N).

[0129] The result shows that the product N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide (C 16 H 17 O2N) is obtained. The yield of N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide is calculated to be 90% and the selectivity is 100%.

[0130] Application Example 10

[0131] The difference between this example and the application example 1 is that 3- methoxybenzylamine (C8H9NO) is used instead of benzylamine (C7H9N).

[0132] The result shows that the product N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide (C 12 H 11 N3) is obtained. The yield of N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide is calculated to be 90% and the selectivity is 100%.

[0133] Application Example 11

[0134] The difference between this example and the application example 1 is that 3- methoxybenzylamine (C8H9NO) is used instead of benzylamine (C7H9N).

[0135] The result shows that the product N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide (C 10 H9O2N) is obtained. The yield of N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide is calculated to be 90% and the selectivity is 100%.

[0136] Application Example 12

[0137] The difference between this example and the application example 1 is that 3- methoxybenzylamine (C8H9NO) is used instead of benzylamine (C7H9N).

[0138] The result shows that the product N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide (C 10 H9S2N) is obtained. The yield of N-(3-methoxybenzyl)-l-(3-methoxyphenyl) formimidamide is calculated to be 90% and the selectivity is 100%.

Claims

1. An anthraquinone-based MOF photocatalytic material, characterized in that, It is obtained by a solvothermal reaction of ligand DPAq and nickel source in a mixed solvent; wherein, ligand DPAq is 2,6-bis(pyrazol-4-yl)-9,10-anthraquinone, the mixed solvent is a combination of N,N-dimethylformamide and water; the nickel source is Ni(OAc)2·4H2O, and the solvothermal reaction is carried out at ≥100℃.

2. The method for preparing the anthraquinone-based MOF photocatalytic material according to claim 1, characterized in that, The ligand DPAq and the nickel source were dissolved in N,N-dimethylformamide and water, respectively. The two solutions were mixed and subjected to a solvothermal reaction to obtain the product. The nickel source was Ni(OAc)2·4H2O, and the solvothermal reaction was carried out at ≥100℃.

3. An anthraquinone-based MOF photocatalytic material crystal, characterized in that, This material belongs to the cubic crystal system. Fm3̅ m Space group, cell parameters are: a =31.3753(4)Å, b =31.3753(4)Å, c =31.3753(4)Å, α = 90.00 o , β = 90.00 o , γ = 90.00 o The anthraquinone-based MOF photocatalytic material has a nickel ion in the crystal metal center that is divalent. The MOF framework consists of an inorganic secondary building unit and a Ni8 cluster, which are connected to 12 DPAq linkers to form a three-dimensional porous framework with octahedral and tetrahedral cavities. The DPAq is 2,6-bis(pyrazol-4-yl)-9,10-anthraquinone.

4. The method for preparing the anthraquinone-based MOF photocatalytic material crystal according to claim 3, characterized in that, The ligand DPAq and a nickel source are placed in a mixed solvent, the pH of the system is adjusted to acidic, and the reaction is carried out under heating conditions. After the reaction solution is cooled, crystals precipitate out, which yields the product. The ligand DPAq is 2,6-bis(pyrazol-4-yl)-9,10-anthraquinone, the mixed solvent is a combination of N,N-dimethylformamide and water, and the nickel source is Ni(OAc)2·4H2O. The reaction is carried out at ≥100℃.

5. The preparation method according to claim 4, characterized in that, Adjust the pH of the system to 4.0~6.

5.

6. The application of the anthraquinone-based MOF photocatalytic material of claim 1 or the anthraquinone-based MOF photocatalytic material crystal of claim 3 in the photocatalytic self-coupling reaction of benzylamine to prepare imine compounds.

Images