MOFs as well as preparation method and application thereof

Abstract

The invention relates to MOFs, the chemical formula of the MOFs is [M (L1) (L2) (O)] n, M is any one of Cu, Co and Ni, L1 and L2 are ligands, the structural formula of L1 is # imgabs0 # L2 is # imgabs1 #, the MOFs comprises molecular ring units distributed according to a linear array, the molecular ring is formed by the ligand L2 and M metal ions, and the molecular ring is formed by the ligand L2 and the M metal ions. The structural formula of the molecular rings is # imgabs2, the ring planes of the different molecular rings are oppositely arranged in space, opposite M metal ions in adjacent molecular rings are connected through a ligand L1, and the opposite M metal ions in the adjacent molecular rings are coordinated with N atoms at the two ends of the ligand L1 respectively. According to the present invention, the L2 ligand and the L1 ligand ring form the molecular cage, and the molecular sizes of the L1 ligand and the L2 ligand are suitable, such that the molecular cage has the suitable accommodation space, is matched with the molecular volume of the dodecaphosphotungstic acid, has the good matching property with the dodecaphosphotungstic acid, can easily stabilize the dodecaphosphotungstic acid, and can substantially broaden the application range of the dodecaphosphotungstic acid.

Description

Technical Field

[0001] This application relates to the field of materials, and particularly to metal-organic framework materials. Background Art

[0002] MOFs is the abbreviation of Metal-Organic Frameworks. It is a class of crystalline porous materials with a periodic network structure formed by the self-assembly of inorganic metal centers (metal ions or metal clusters) and bridging organic ligands. MOFs is an organic-inorganic hybrid material, also known as coordination polymer. It is different from both inorganic porous materials and general organic complexes, and has the rigid characteristics of inorganic materials and the flexible characteristics of organic materials.

[0003] Due to its complex spatial structure, cage-like structures often appear in the molecular framework of MOFs. These cage-like structures can capture other small molecules, enabling MOFs materials to also possess the functions of these captured small molecules.

[0004] Polyoxometalates (POMs), due to their unique structures and numerous excellent potential application properties, especially their potential application values in aspects such as catalytic degradation of pollutants, chirality, molecular magnetism, pharmaceutical chemistry, and nuclear waste treatment, have attracted the attention and research exploration of scientists around the world. After more than two hundred years of efforts, important progress has been made in the synthesis strategies and methods of novel polyoxometalate-based compounds with high catalytic activity. Phosphotungstic heteropolyacid, also known as keggin-type phosphotungstic acid, that is, dodecaphosphotungstic acid, has characteristics such as non-toxicity, strong acidity, good chemical stability, and catalytic performance. However, when directly used as a photocatalyst in water system treatment, phosphotungstic heteropolyacid still has the following problems: poor use stability, difficult recovery, difficulties in the separation and reuse of the catalyst, and the risk of secondary pollution.

[0005] In order to improve the applicability of phosphotungstic heteropolyacid catalysts, scientists have done a lot of work in the aspect of carrier loading. However, the currently selected carriers for phosphotungstic heteropolyacid catalysts also have many disadvantages: low loading amount, easy loss of the loaded catalyst, especially due to the uneven accumulation of phosphotungstic heteropolyacid, resulting in uneven distribution of reaction active sites and passivation of the acidity of polyacids in aqueous solutions.

[0006] Due to its designable cage-like structure, MOFs has the potential to be used as a carrier for phosphotungstic heteropolyacid catalysts. However, the existing MOFs materials currently have poor compatibility with phosphotungstic heteropolyacid, and a brand-new MOFs needs to be designed. Summary of the Invention

[0007] The embodiments of the present application provide a kind of MOFs, its preparation method and application, to solve the technical problem that the existing MOFs materials have poor matching with phosphotungstic heteropolyacid.

[0008] In the first aspect, the embodiments of the present application provide a kind of MOFs, and the chemical formula of the MOFs is [M(L1)(L2)(O)] n , where M is any one of Cu, Co, Ni, and both L1 and L2 are ligands. Among them,

[0009] The structural formula of L1 is:

[0010] The structural formula of L2 is:

[0011] The MOFs include molecular ring units distributed in a linear array. The molecular ring is formed by ligand L2 and M metal ions, and the structural formula of the molecular ring is:

[0012]

[0013] The ring planes of different molecular rings are oppositely arranged in space, and the opposite M metal ions in adjacent molecular rings are connected by ligand L1. Among them, the opposite M metal ions in adjacent molecular rings are respectively coordinated with the N atoms at both ends of L1.

[0014] In some embodiments of the present application, the MOFs further include dodecatungstophosphoric acid, and the dodecatungstophosphoric acid is located in the molecular cage formed by L1 and L2.

[0015] In some embodiments of the present application, the chemical formula of the MOFs is C 22 H 42 CuN 15 O 44 PW 12 .

[0016] In some embodiments of the present application, the crystal of the MOFs belongs to the monoclinic system, the space group is C2 / m, and the unit cell parameters are α = γ = 90°, β = 115.797°.

[0017] In the second aspect, the embodiments of the present application provide a preparation method of MOFs. The method includes the following steps:

[0018] Provide a precursor solution, and the precursor solution includes dodecatungstophosphoric acid, soluble divalent copper salt, ligand L1, and ligand L2;

[0019] Process the precursor solution in a closed container at a first temperature for a first time to obtain the MOFs.

[0020] Among them,

[0021] The structural formula of L1 is:

[0022] The structural formula of L2 is:

[0023] In some embodiments of the present application, the first temperature is 150 - 170 °C.

[0024] In some embodiments of the present application, the first time is 60 - 100 h.

[0025] In some embodiments of the present application, in the precursor solution, the mass ratio of dodecatungstophosphoric acid to water is 1:180 - 220.

[0026] In some embodiments of the present application, the method further includes the following steps:

[0027] Perform ultrasonic cleaning treatment on the obtained MOFs.

[0028] In some embodiments of the present application, providing the precursor solution includes the following steps:

[0029] Fully mix 1,2,4 - triazole, excessive potassium carbonate and N,N - dimethylformamide to obtain a first solution;

[0030] Add 1,4 - dibromobutane to the first solution and treat it at a second temperature for a second time to obtain a second solution;

[0031] Remove the solvent of the second solution to obtain a solid mixture;

[0032] Extract the obtained solid mixture with dichloromethane to obtain an extract, and evaporate the extract to dryness to obtain a ligand mixture including L1 and L2;

[0033] Prepare the ligand mixture with water into a ligand solution including the two ligands L1 and L2;

[0034] Prepare the precursor solution by mixing the ligand solution with dodecatungstophosphoric acid and copper chloride.

[0035] In some embodiments of the present application, the second temperature is 50 - 70 °C.

[0036] In some embodiments of the present application, the second time is 100 - 150 min.

[0037] In a third aspect, an embodiment of the present application provides an application of MOFs. The MOFs are the MOFs described in the first aspect or the MOFs prepared by the method described in the second aspect, and the MOFs are applied to a catalyst.

[0038] In some embodiments of the present application, the MOFs are used as photocatalysts for the degradation of organic pollutants in water bodies.

[0039] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0040] The MOFs provided by the embodiments of the present application form a molecular ring by making the L2 ligand and the M metal ion, and then form a molecular cage by connecting the molecular rings through the L1 ligand. Due to the appropriate molecular sizes of the L1 and L2 ligands, the molecular cage has an appropriate accommodation space, which fits the molecular volume of dodecatungstophosphoric acid, has good matching with dodecatungstophosphoric acid, is beneficial to stabilizing dodecatungstophosphoric acid, and greatly broadens the application scope of dodecatungstophosphoric acid. Description of the Drawings

[0041] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments in line with the present application, and are used together with the specification to explain the principles of the present application.

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 It is a 3D model diagram of the molecular ring provided by the embodiments of the present application;

[0044] Figure 2 It is a 3D model diagram of the MOFs provided by the embodiments of the present application;

[0045] Figure 3 It is a 3D model diagram of the coordination situation of the M metal ion in the MOFs provided by the embodiments of the present application;

[0046] Figure 4 It is a 3D model diagram of the MOFs embedded with dodecatungstophosphoric acid provided by the embodiments of the present application;

[0047] Figure 5 It is a supramolecular stacking structure diagram of the MOFs embedded with dodecatungstophosphoric acid provided by the embodiments of the present application;

[0048] Figure 6 It is a thermogravimetric analysis diagram of the MOFs provided by Embodiment 1 of the present application;

[0049] Figure 7 It is an infrared spectrum diagram of dodecatungstophosphoric acid and the MOFs provided by Embodiment 1 of the present application;

[0050] Figure 8 It is the absorbance-time curve of the rhodamine B solution in the first control group of this application;

[0051] Figure 9 It is the absorbance-time curve of the rhodamine B solution in the second control group of this application;

[0052] Figure 10 It is the absorbance-time curve of the rhodamine B solution in the first experimental group of this application;

[0053] Figure 11 It is the rhodamine B degradation kinetic curve of the first control group, the second control group and the first experimental group of this application;

[0054] Figure 12 It is the degradation kinetic curve of the organic pollutants in the second to fifth experimental groups of this application. Detailed implementation manners

[0055] To make the objectives, technical solutions and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some but not all of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application.

[0056] Unless otherwise specifically stated, the terms used in this article should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used in this article have the same meaning as the general understanding of those skilled in the technical field to which this application belongs. In case of conflict, this specification prevails.

[0057] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in this application can be obtained through market purchase or can be prepared by existing methods.

[0058] Existing MOFs materials have the technical problem of poor matching with phosphotungstic heteropolyacid.

[0059] The technical solutions provided by the embodiments of this application to solve the above technical problems are generally as follows:

[0060] In a first aspect, the embodiments of this application provide a kind of MOFs, and the chemical formula of the MOFS is [M(L1)(L2)(O)] n , where M is any one of Cu, Co, and Ni, and both L1 and L2 are ligands, where,

[0061] The structural formula of L1 is:

[0062] The structural formula of L2 is:

[0063] The MOFs include molecular ring units distributed in a linear array. The molecular ring is formed by ligand L2 and M metal ions, and the structural formula of the molecular ring is:

[0064]

[0065] The ring planes of different said molecular rings are oppositely arranged in space, and the opposite M metal ions in adjacent molecular rings are connected by ligand L1, wherein the opposite M metal ions in adjacent molecular rings are respectively coordinated with the N atoms at both ends of L1.

[0066] Please refer to Figure 1 、 Figure 2 、 Figure 3 。 Figure 1 The 3D model diagram of the said molecular ring is shown, Figure 2 The 3D model diagram of the said MOFs is shown. It is easy to find that the MOFs molecule is formed by the infinite cyclic extension of one said molecular ring and two said L1s in one-dimensional direction, that is, the said molecular ring is distributed in a linear array and connected by L1. Taking the M metal ion as a copper ion as an example, Figure 3 The coordination situation of the M metal ion in the said MOFs molecule is shown. It can be found that the divalent copper ion presents a 5-coordination structure, and it is connected with a nitrogen atom on one L1 and two nitrogen ions on two L2s to form a quadrangular pyramid.

[0067] Observation Figure 2 It is easy to find that L1 and L2 can form a semi-closed molecular cage, and the accommodation space of this molecular cage fits the molecular volume of dodecatungstophosphoric acid.

[0068] In this application, by forming a molecular ring with ligand L2 and M metal ions, and then connecting the molecular rings with ligand L1 to form a molecular cage, due to the appropriate molecular sizes of ligands L1 and L2, the said molecular cage has an appropriate accommodation space, which fits the molecular volume of dodecatungstophosphoric acid, has good matching with dodecatungstophosphoric acid, is beneficial to stabilizing dodecatungstophosphoric acid, and greatly broadens the application scope of dodecatungstophosphoric acid.

[0069] In some embodiments of this application, the MOFs further include dodecatungstophosphoric acid, and the dodecatungstophosphoric acid is located inside the molecular cage formed by L1 and L2.

[0070] Through Figure 4 It is easy to understand that dodecatungstophosphoric acid is easily embedded in the said molecular cage.

[0071] In addition, according to the results of actual experiments, the catalytic effect of MOFs embedded with dodecatungstophosphoric acid is better than that of dodecatungstophosphoric acid alone. The specific experimental process and result data are shown in the examples section below.

[0072] In some embodiments of the present application, the chemical formula of the MOFs is C 22 H 42 CuN 15 O 44 PW 12 。

[0073] In some embodiments of the present application, the crystal of the MOFs belongs to the monoclinic system, the space group is C2 / m, and the unit cell parameters are α = γ = 90°, β = 115.797°.

[0074] The above crystal characteristics are the crystal characteristics of MOFs embedded with dodecatungstophosphoric acid when M is a copper ion.

[0075] In a second aspect, embodiments of the present application provide a method for preparing MOFs, the method comprising the following steps:

[0076] S1: Provide a precursor solution, the precursor solution comprising dodecatungstophosphoric acid, a soluble divalent copper salt, ligand L1, and ligand L2;

[0077] S2: Treat the precursor solution in a closed container at a first temperature for a first time to obtain the MOFs,

[0078] wherein,

[0079] The structural formula of L1 is:

[0080] The structural formula of L2 is:

[0081] In some embodiments of the present application, the first temperature is 150 - 170 °C.

[0082] The adverse effect of the first temperature being lower than the above range is that this MOFs structure cannot be synthesized, and the adverse effect of the first temperature being higher than the above range is that the reaction rate is too fast and the formed crystals decompose again.

[0083] In some embodiments of the present application, the first time is 60 - 100 h.

[0084] If the first time is shorter than the above range, the adverse effect is that the quality of the grown crystal is not high (for example, semi-crystallization, too small crystal size, which is not conducive to crystal structure analysis). If the first time is longer than the above range, the adverse effect is that the crystal becomes unstable over time, is prone to powdering, the degree of crystallization decreases, and the size becomes smaller.

[0085] In some embodiments of the present application, in the precursor solution, the mass ratio of dodecatungstophosphoric acid to water is 1:180 - 220.

[0086] In some embodiments of the present application, the method further includes the following steps:

[0087] Perform ultrasonic cleaning treatment on the obtained MOFs.

[0088] It is easy to understand that performing ultrasonic cleaning treatment on the obtained MOFs can wash away the impurities attached to the surface of the MOFs.

[0089] In some embodiments of the present application, providing the precursor solution includes the following steps:

[0090] S11: Thoroughly mix 1,2,4-triazole, excessive potassium carbonate and N,N-dimethylformamide to obtain a first solution;

[0091] S12: Add 1,4-dibromobutane to the first solution and treat it at a second temperature for a second time to obtain a second solution;

[0092] S13: Remove the solvent of the second solution to obtain a solid mixture;

[0093] S14: Extract the obtained solid mixture with dichloromethane to obtain an extract, and evaporate the extract to dryness to obtain a ligand mixture including L1 and L2;

[0094] S15: Prepare the ligand mixture with water to form a ligand solution including the two ligands L1 and L2;

[0095] S16: Prepare the precursor solution by mixing the ligand solution with dodecatungstophosphoric acid and copper chloride.

[0096] In some embodiments of the present application, the second temperature is 50 - 70 °C.

[0097] In some embodiments of the present application, the second time is 100 - 150 min.

[0098] In a third aspect, an embodiment of the present application provides an application of MOFs. The MOFs are the MOFs described in the first aspect or the MOFs prepared by the method described in the second aspect, and the MOFs are applied to a catalyst.

[0099] It is easy to understand that when dodecatungstophosphoric acid is embedded in the MOFs, due to the dodecatungstophosphoric acid being confined in the molecular cage, it has high stability and can work as a catalyst for a long time.

[0100] When the dodecatungstophosphoric acid is not embedded in the MOFs, due to the presence of M metal ions, it itself also has the potential to be used as a catalyst.

[0101] The application of the MOFs is realized based on the embodiments of the first aspect or the second aspect. The specific implementation manners can refer to the embodiments of the first aspect or the second aspect and the common general knowledge in the field of catalysts. Since the application of the MOFs can adopt all the technical solutions of any one of the embodiments of the first aspect or the second aspect, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated one by one here.

[0102] In some embodiments of the present application, the MOFs are applied as a photocatalyst for degrading organic pollutants in water bodies.

[0103] The following further elaborates the present application in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions noted in the following embodiments are generally determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0104] Example 1

[0105] This example provides a kind of MOFs, which is prepared by the following steps:

[0106] Sa: Mix 1,2,4-triazole and excessive potassium carbonate with N,N-dimethylformamide and stir for 1 h to obtain a first solution;

[0107] Sb: Add 1,4-dibromobutane to the first solution and reflux at 60 °C for 2 h to obtain a second solution;

[0108] Sc: Evaporate the N,N-dimethylformamide in the second solution to dryness to obtain a solid mixture;

[0109] Sd: Extract the obtained solid mixture with dichloromethane three times, combine the extraction solutions, evaporate the extraction solutions to dryness to obtain a white powder, which is a ligand mixture including L1 and L2;

[0110] Se: Weigh 9.4 mg of the said ligand mixture with an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir with a multi-head heating stirrer to completely dissolve it;

[0111] Sf: Weigh 50 mg of dodecatungstophosphoric acid using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0112] Sg: Weigh 17 mg of CuCL1 using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0113] Sh: Mix the three solutions obtained in steps Se to Sg, add them to a reaction kettle, then add 4 mL of distilled water to the reaction kettle, and stir with a magnetic stirrer for 10 minutes until evenly mixed;

[0114] Si: Seal the reaction kettle and place it in an oven to heat for 72 h, and keep the temperature at 160 °C;

[0115] Sj: Put the materials in the reaction kettle into a 25 mL beaker, then use water as a cleaning agent, clean it twice with an ultrasonic cleaning instrument to remove impurities, filter, and air-dry naturally to obtain blue crystals, that is, the MOFs.

[0116] Example 2

[0117] The main difference between this example and Example 1 is:

[0118] In step Si, the heating time of the reaction kettle in the oven is 96 h. Specifically as follows:

[0119] This example provides a kind of MOFs, which is prepared by the following steps:

[0120] Sa: Mix 1,2,4-triazole and excessive potassium carbonate with N,N-dimethylformamide and stir for 1 h to obtain a first solution;

[0121] Sb: Add 1,4-dibromobutane to the first solution and reflux at 60 °C for 2 h to obtain a second solution;

[0122] Sc: Evaporate the N,N-dimethylformamide in the second solution to dryness to obtain a solid mixture;

[0123] Sd: Extract the obtained solid mixture three times with dichloromethane, combine the extraction liquids, evaporate the extraction liquids to dryness to obtain a white powder, that is, a mixture ligand including L1 and L2;

[0124] Se: Weigh 9.4 mg of the mixture ligand using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0125] Sf: Weigh 50 mg of dodecatungstophosphoric acid using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0126] Sg: Weigh 17 mg of CuCl1 using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0127] Sh: Mix the three solutions obtained in steps Se - Sg, add them to a reaction kettle, then add 4 mL of distilled water to the reaction kettle, and stir with a magnetic stirrer for 10 minutes until evenly mixed;

[0128] Si: Seal the reaction kettle and put it into an oven to heat for 96 h, and keep the temperature at 160 °C;

[0129] Sj: Put the materials in the reaction kettle into a 25 mL beaker, then use water as a cleaning agent, clean it twice with an ultrasonic cleaning instrument to remove impurities, filter, and air-dry naturally to obtain blue crystals, which are the MOFs.

[0130] Example 3

[0131] The main difference between this example and Example 1 is:

[0132] In step Si, the heating temperature of the reaction kettle in the oven is kept at 180 °C. Specifically as follows:

[0133] This example provides a kind of MOFs, which is prepared through the following steps:

[0134] Sa: Mix 1,2,4-triazole and excessive potassium carbonate with N,N-dimethylformamide and stir for 1 h to obtain the first solution;

[0135] Sb: Add 1,4-dibromobutane to the first solution and reflux at 60 °C for 2 h to obtain the second solution;

[0136] Sc: Evaporate the N,N-dimethylformamide in the second solution to dryness to obtain a solid mixture;

[0137] Sd: Extract the obtained solid mixture with dichloromethane three times, combine the extraction liquids, evaporate the extraction liquids to dryness to obtain a white powder, which is a ligand mixture including L1 and L2;

[0138] Se: Weigh 9.4 mg of the said ligand mixture using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0139] Sf: Weigh 50 mg of dodecatungstophosphoric acid using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0140] Sg: Weigh 17 mg of CuCL1 using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0141] Sh: Mix the three solutions obtained in steps Se to Sg, add them to a reaction kettle, then add 4 mL of distilled water to the reaction kettle, and stir with a magnetic stirrer for 10 minutes until evenly mixed;

[0142] Si: Seal the reaction kettle and place it in an oven to heat for 72 h, keeping the temperature at 180 °C;

[0143] Sj: Put the materials in the reaction kettle into a 25 mL beaker, then use water as a cleaning agent, and clean it twice with an ultrasonic cleaning instrument to remove impurities, filter, and air-dry naturally to obtain blue crystals, which are the MOFs.

[0144] Example 4

[0145] The main difference between this example and Example 1 is:

[0146] The coordinated metal ion is selected as Co 2+ , and the raw material in step Sg is selected as CoCL1. Specifically as follows:

[0147] This example provides a kind of MOFs, which is prepared through the following steps:

[0148] Sa: Mix 1,2,4-triazole and excessive potassium carbonate with N,N-dimethylformamide and stir for 1 h to obtain the first solution;

[0149] Sb: Add 1,4-dibromobutane to the first solution and reflux at 60 °C for 2 h to obtain the second solution;

[0150] Sc: Evaporate the N,N-dimethylformamide in the second solution to dryness to obtain a solid mixture;

[0151] Sd: Extract the obtained solid mixture three times with dichloromethane, combine the extraction solutions, evaporate the extraction solutions to dryness to obtain a white powder, which is a mixture ligand including L1 and L2;

[0152] Se: Weigh 9.4 mg of the said mixture ligand using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0153] Sf: Weigh 50 mg of dodecatungstophosphoric acid using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0154] Sg: Weigh 24 mg of CoCl1 using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0155] Sh: Mix the three solutions obtained in steps Se to Sg, add them to a reaction kettle, then add 4 mL of distilled water to the reaction kettle, and stir with a magnetic stirrer for 10 minutes until evenly mixed;

[0156] Si: Seal the reaction kettle and place it in an oven to heat for 72 h, and keep the temperature at 180 °C;

[0157] Sj: Put the materials in the reaction kettle into a 25 mL beaker, then use water as a cleaning agent, clean it twice with an ultrasonic cleaning instrument to remove impurities, filter, and air-dry naturally to obtain red crystals, which are the MOFs.

[0158] Example 5

[0159] The main difference between this example and Example 1 is:

[0160] The coordinated metal ion is selected as Ni 2+ , and the raw material in step Sg is selected as NiCL1. Specifically as follows:

[0161] This example provides a kind of MOFs, which is prepared through the following steps:

[0162] Sa: Mix 1,2,4-triazole and excessive potassium carbonate with N,N-dimethylformamide and stir for 1 h to obtain the first solution;

[0163] Sb: Add 1,4-dibromobutane to the first solution and reflux at 60 °C for 2 h to obtain the second solution;

[0164] Sc: Evaporate the N,N-dimethylformamide in the second solution to dryness to obtain a solid mixture;

[0165] Sd: Extract the obtained solid mixture with dichloromethane three times, combine the extraction liquids, evaporate the extraction liquids to dryness to obtain a white powder, which is a mixture ligand including L1 and L2;

[0166] Se: Weigh 9.4 mg of the mixture ligand using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0167] Sf: Weigh 50 mg of dodecatungstophosphoric acid using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0168] Sg: Weigh 24 mg of NiCL1 using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0169] Sh: Mix the three solutions obtained in steps Se - Sg, add them to a reaction kettle, then add 4 mL of distilled water to the reaction kettle, and stir with a magnetic stirrer for 10 minutes to mix evenly;

[0170] Si: Seal the reaction kettle and put it into an oven to heat for 72 h, keeping the temperature at 180 °C;

[0171] Sj: Put the materials in the reaction kettle into a 25 mL beaker, then use water as a cleaning agent, and clean it twice with an ultrasonic cleaning instrument to remove impurities, filter, and air-dry naturally to obtain light green crystals, which are the MOFs.

[0172] Comparative Example

[0173] The main difference between this comparative example and Example 1 is:

[0174] In step Sf, silicotungstic acid is used instead of dodecatungstophosphoric acid; no crystals are obtained in step Sj. Specifically as follows:

[0175] This example provides a kind of MOFs, which is prepared through the following steps:

[0176] Sa: Mix 1,2,4-triazole and excessive potassium carbonate with N,N-dimethylformamide and stir for 1 h to obtain the first solution;

[0177] Sb: Add 1,4-dibromobutane to the first solution and reflux at 60 °C for 2 h to obtain the second solution;

[0178] Sc: Evaporate the N,N-dimethylformamide in the second solution to dryness to obtain a solid mixture;

[0179] Sd: Extract the obtained solid mixture with dichloromethane three times, combine the extraction liquids, evaporate the extraction liquids to dryness to obtain a white powder, which is a ligand mixture including L1 and L2;

[0180] Se: Weigh 9.4 mg of the said ligand mixture using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0181] Sf: Weigh 50 mg of silicotungstic acid using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0182] Sg: Weigh 24 mg of NiCL1 using an electronic balance, put it into a 12.5 mL beaker containing 2 mL of distilled water, and stir it with a multi-head heating stirrer until it is completely dissolved;

[0183] Sh: Mix the three solutions obtained in steps Se to Sg, add them to a reaction kettle, then add 4 mL of distilled water to the reaction kettle, and stir with a magnetic stirrer for 10 minutes until evenly mixed;

[0184] Si: Seal the reaction kettle and place it in an oven to heat for 72 h, and keep the temperature at 180 °C;

[0185] Sj: Put the materials in the reaction kettle into a 25 mL beaker, and no crystals are obtained.

[0186] Related experimental and effect data:

[0187] The different reaction conditions between Examples 1 to 5 and the comparative examples, as well as the obtained crystal sizes, are shown in Table 1.

[0188]

[0189] Table 1

[0190] It can be easily found from Table 1 that metal ions such as Cu 2+ , Co, and Ni can all be used to prepare MOFs. Under the reaction conditions of 160 °C and 72 h, among these three metal ions, using Cu 2+ can obtain the largest-sized crystals.

[0191] On the premise of using Cu 2+ as the metal ion, under the reaction conditions of 160 °C and 72 h, crystals with relatively large sizes can be obtained. Prolonging the reaction time or increasing the temperature will both lead to a decrease in crystal size. A too long reaction time may cause some products to be damaged at high temperatures; when the temperature is too high, while the crystal size decreases, the total number of crystals also increases. This may be because too high a temperature may lead to a relatively high reaction rate, forming a relatively large number of crystal nuclei, so that individual crystals will become smaller.

[0192] In the comparative example, no crystals were prepared using silicotungstic acid. The main reason is that the different surface bonding abilities of polyacids lead to different final crystallization effects.

[0193] Single crystal X-ray diffraction tests were performed on the MOFs of Example 1, and the crystallographic parameters are shown in Table 2: Cu 2+ The bond lengths between ions and other atoms are shown in Table 3; Cu2+ The bond angles between the ionically connected chemical bonds are shown in Table 4.

[0194]

[0195] Table 2

[0196]

[0197]

[0198] Table 3

[0199] Atom Atom Atom Angle / ° Atom Atom Atom Angle / ° N1#2 Cu1 N1 137.0(10) N4 Cu1 N4#2 179.1(12) N4 Cu1 O1W 89.6(6) N4 Cu1 N1#2 88.9(6) N4#2 Cu1 O1W 89.6(6) N4#2 Cu1 N1#2 91.4(6) N1#2 Cu1 O1W 111.5(5) N4 Cu1 N1 91.4(6) N1 Cu1 O1W 111.5(5) N4#2 Cu1 N1 88.9(6)

[0200] Table 4

[0201] In Tables 2 to 4, Cu1 refers to a certain copper ion, N1 and N1#2 respectively refer to the nitrogen atoms connected to the copper ion by two L1 ligands, and N4 and N4#1 refer to the nitrogen atoms connected to the copper ion by two L2 ligands. The specific spatial positions of Cu1, N1, N1#2, N4, and N4#1 can be referred to Figure 3 .

[0202] X-ray single crystal diffraction data shows that the MOFs present a one-dimensional chain structure. From Figure 3 it can be known that the divalent copper ion presents a 5-coordinate structure, which is connected to a nitrogen atom on one L1 and two nitrogen ions on two L2s to form a square pyramid. From Figures 1 - 2 the overall structure of the product can be seen. First, two compounds L2 are connected with two copper ions as connection points to form a molecular ring; between the intermediates 1, they are connected with copper ions as points and two compounds L1 as bridges to form a one-dimensional complex. There is a large space between the chains of this complex. As Figure 4 shown, dodecatungstophosphoric acid just fits into the gap, and then the final MOFs product is generated. There is a gap between dodecatungstophosphoric acid and the divalent copper ion, and an octanuclear water cluster adheres to it.

[0203] Figure 5 shows the close packing mode of the MOFs crystal. Each compound 1 is stacked with six identical structures to form a three-dimensional supramolecule, and the one-dimensional extension direction of each compound 1 is parallel to the C axis. Figure 5 The C axis is perpendicular to the plane of the figure in Figure 5 so it is not shown.

[0204] Thermogravimetric analysis was performed on the MOFs obtained in Example 1, and a thermogravimetric analysis diagram was obtained, as Figure 6 shown.

[0205] FromFigure 6 It can be known from [description] that the weight loss curve of the measured sample produces the first plateau at 200 °C, which may be due to the loss of crystal water and coordinated water in the sample. At about 320 °C, the mass of the sample begins to decrease again until the end of the reaction. The mass decrease in this stage is because the sample continuously degrades and volatilizes under high temperature conditions.

[0206] The MOFs obtained in Example 1 were subjected to infrared spectroscopy analysis, and the obtained infrared spectrum was summarized with the infrared spectrum of dodecatungstophosphoric acid to form Figure 7 .

[0207] From Figure 7 it can be known that in the band range of 700 - 1300 cm -1 for MOFs and dodecatungstophosphoric acid, absorption peaks were found at 780 cm - 1, 810 cm -1 , 1000 cm -1 , 1100 cm -1 . The positions of these absorption peaks are nearly overlapped with the characteristic peaks of dodecatungstophosphoric acid. Therefore, we can infer that dodecatungstophosphoric acid has the same structure as some parts of the sample. This phenomenon indicates that the polymer contains dodecatungstophosphoric acid.

[0208] The photocatalytic experiment on the MOFs obtained in Example 1 was carried out as follows:

[0209] For the first control group, 4 mg of dodecatungstophosphoric acid and 0.2 mL of 30% hydrogen peroxide were added to 6 10 - mL quartz tubes. At the same time, 5 ml of rhodamine B solution was poured into each quartz test tube, and they were placed in an XPA series photoreactor. After 30 minutes of dark treatment, photocatalysis was carried out. Every 20 minutes, 1 quartz test tube was taken out, and the liquid in it was poured into a centrifuge tube and centrifuged at a speed of 8000 revolutions for 4 minutes. The supernatant was taken and analyzed with a UV - absorption spectrometer to understand the photocatalytic effect of phosphotungstic acid.

[0210] For the second control group, only 0.2 mL of 30% hydrogen peroxide was added without adding dodecatungstophosphoric acid, and other conditions were the same as those of the first control group.

[0211] For the first experimental group, 4 mg of the MOFs obtained in Example 1 was used to replace dodecatungstophosphoric acid in the first control group, and other conditions were the same as those of the first control group.

[0212] Figures 8 - 10 The absorbance - time curves of rhodamine B solution in the first control group, the second control group, and the first experimental group are respectively shown. Figure 11 is the degradation kinetic curve of rhodamine B plotted according to Figures 8 - 10 the results of

[0213] FromFigure 8 It can be learned from [reference] that when phosphotungstic acid is added as a catalyst and hydrogen peroxide is added as an oxidant to the rhodamine B solution, under the illumination condition, there is no obvious degradation of the rhodamine B solution.

[0214] From Figure 9 it can be found that for the rhodamine B with hydrogen peroxide added as an oxidant, under the illumination condition, after illumination for different times, the absorption peak gradually becomes smaller. This indicates that hydrogen peroxide can degrade rhodamine B under the illumination condition, but the degradation rate is not fast.

[0215] From Figure 10 it can be found that for the rhodamine B solution with MOFs and hydrogen peroxide added, as the illumination time prolongs, the absorption of ultraviolet light decreases significantly, which indicates that the rhodamine B in the solution decreases significantly. This phenomenon shows that MOFs can effectively degrade the organic pollutant rhodamine B under the illumination condition.

[0216] From Figure 11 it can be directly observed that the degradation efficiency of the first experimental group is much higher than that of the first control group and the second control group.

[0217] In the second to fifth experimental groups, the organic pollutants are replaced with methyl orange, methylene blue, tetracycline hydrochloride, and ofloxacin respectively for the rhodamine B in the first experimental group, and the corresponding degradation kinetic curves are plotted and summarized to form Figure 12 .

[0218] From Figure 12 it, we can clearly understand that compound 1 has considerable catalytic effects on the degradation of different organic pollutants under the illumination condition.

[0219] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and the individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0220] In this application, unless otherwise specified, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the attached drawings. Additionally, in the description of this application's specification, the terms "comprise", "include", etc. mean "include but not limited to". Moreover, the term "comprise", "include" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, the elements defined by the statement "comprising..." do not preclude the existence of additional identical elements in the process, method, article or device comprising the said elements. In this text, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that these three associated objects can exist alone in any one item, or any at least two of them exist simultaneously. For example, for A, and / or B, and / or C, it can mean that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three exist simultaneously. In this text, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one item (piece) below" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one item (piece) among a, b, or c", or, "at least one item (piece) among a, b, and c" can both mean: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0221] The above description is only the specific implementation manners of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A kind of MOFs, characterized in that, The chemical formula of the MOFs is [M(L1)(L2)(O)] n , where M is any one of Cu, Co, and Ni, and both L1 and L2 are ligands. Among them, The structural formula of L1 is as follows: The structural formula of L2 is as follows: The MOFs include molecular ring units distributed in a linear array. The molecular rings are formed by ligand L2 and M metal ions, and the structural formula of the molecular ring is as follows: The ring planes of different molecular rings are oppositely arranged in space, and the opposite M metal ions in adjacent molecular rings are connected by ligand L1, where the opposite M metal ions in adjacent molecular rings are respectively coordinated with the N atoms at both ends of L1.

2. The MOFs according to claim 1, characterized in that, The MOFs further include dodecatungstophosphoric acid, which is located in the molecular cage formed by L1 and L2.

3. The MOFs according to claim 2, characterized in that, The chemical formula of the MOFs is C 22 H 42 CuN 15 O 44 PW 12 .

4. The MOFs according to claim 3, characterized in that, The crystal of the MOFs belongs to the monoclinic system, with the space group C2 / m and the unit cell parameters being α = γ = 90°, β = 115.797°.

5. A preparation method of MOFs, characterized in that, The method includes the following steps: Providing a precursor solution, which includes dodecatungstophosphoric acid, a soluble divalent copper salt, ligand L1, and ligand L2; Processing the precursor solution in a closed container at a first temperature for a first time to obtain the MOFs, wherein, The structural formula of L1 is as follows: The structural formula of L2 is as follows:

6. The preparation method of MOFs according to claim 5, characterized in that, the first temperature is 150 - 170 °C.

7. The preparation method of MOFs according to claim 5, characterized in that, The first time is 60 - 100 h.

8. The preparation method of MOFs according to claim 5, characterized in that, In the precursor solution, the mass ratio of dodecatungstophosphoric acid to water is 1:180 - 220.

9. The preparation method of MOFs according to claim 5, characterized in that, The method further includes the following steps: Performing ultrasonic cleaning treatment on the obtained MOFs.

10. The preparation method of MOFs according to claim 5, characterized in that, The step of providing the precursor solution includes the following steps: Fully mixing 1,2,4-triazole, excessive potassium carbonate, and N,N-dimethylformamide to obtain a first solution; Adding 1,4-dibromobutane to the first solution and processing it at a second temperature for a second time to obtain a second solution; Removing the solvent of the second solution to obtain a solid mixture; Extracting the obtained solid mixture with dichloromethane to obtain an extraction solution, and evaporating the extraction solution to obtain a mixed ligand including L1 and L2; Formulating the mixed ligand with water into a ligand solution including the two ligands L1 and L2; Formulating the ligand solution with dodecatungstophosphoric acid and copper chloride into the precursor solution.

11. The preparation method of MOFs according to claim 10, wherein, The second temperature is 50 - 70 °C.

12. The preparation method of MOFs according to claim 10, characterized in that, The second time is 100 - 150 min.

13. An application of MOFs, characterized in that, The MOFs are the MOFs described in any one of claims 1 - 4, or the MOFs prepared by the method described in any one of claims 5 - 12, and the MOFs are applied to a catalyst.

14. The application of MOFs according to claim 13, wherein The MOFs are applied to a photocatalyst for degrading organic pollutants in water.

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