Six-fold interspersed anion metal organic framework material with single-crystal structure and preparation method and application of six-fold interspersed anion metal organic framework material

Abstract

The invention discloses a sextuple insertion anion metal organic framework material with a single crystal structure as well as a preparation method and application of the sextuple insertion anion metal organic framework material. The sextuple insertion anion metal organic framework material with the single crystal structure is formed by coordination of a ligand taking triphenylene as a main body and zinc ions under a solvothermal condition; in the presence of a conditioning agent, six groups of structures with the same coordination mode are formed by mutual interpenetration in different interpenetration modes, and have good crystallinity and stability; due to the property of the anion framework, the framework material has a promoting effect on adsorption of cationic organic dyes in drinking water, and the cationic organic dyes in water can be effectively removed.

Description

Technical Field

[0001] This invention belongs to the technical field of metal-organic framework functional materials, specifically relating to a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure, its preparation method, and its application. Background Technology

[0002] Conventional adsorbent materials have long dominated the removal of organic dyes from drinking water, mainly including activated carbon, zeolite, clay minerals, and biochar. Their technology is based on physical adsorption and surface chemical interactions. Conventional adsorbents primarily rely on physical or simple chemical processes, and their performance has inherent limitations. For example, activated carbon adsorbs organic matter through π-π packing and micropore filling, showing good effectiveness against non-polar dyes, but its specific surface area is limited, typically less than 1500 m². 2 The adsorption capacity of zeolite is relatively low, ranging from 20 to 80 mg / g, with high regeneration energy consumption and poor selectivity for polar dyes. Zeolite adsorption occurs through ion exchange and electrostatic interactions, with a fixed pore size, generally less than 1.2 nm, making it difficult to adsorb large molecular dyes such as Congo red, resulting in a low capacity of 15-60 mg / g. Clay minerals rely on cation exchange and surface adsorption, but have very low specific surface area and adsorption capacity, ranging from 10-40 mg / g, and are easily affected by coexisting ions. Biochar has diverse adsorption mechanisms, including hydrogen bonding, electrostatics, and π-π, but its kinetics are slow, its structure is prone to collapse, and its capacity is generally less than 200 mg / g. All of these methods share common limitations: low adsorption capacity, slow kinetics, insufficient selectivity, and poor regeneration performance, making them unsuitable for meeting the demands of efficient and deep purification.

[0003] Organic dyes (such as methyl orange, rhodamine B, and methylene blue) are widely found in wastewater from the printing and dyeing, pharmaceutical, and papermaking industries. They are characterized by high toxicity, poor biodegradability, and strong color development. Even low concentrations can damage aquatic ecosystems and threaten human health. Traditional adsorbents (such as activated carbon) suffer from limitations such as low adsorption capacity, difficult regeneration, and poor selectivity.

[0004] Metal-organic frameworks (MOFs) are a class of porous crystalline materials formed by the self-assembly of metal ions or clusters with organic ligands through coordination bonds. They possess ultra-high specific surface areas, reaching up to 7000 m². 2With its high density, adjustable pore size (3-100 Å), functionalized surface sites, and structural designability, MOFs are ideal adsorbents for the efficient removal of organic dyes from drinking water. MOFs achieve efficient adsorption through the following mechanisms: (1) electrostatic interaction, where the positively charged MOF surface (e.g., UiO-66-NH2) forms a strong Coulomb attraction with anionic dyes (e.g., Congo Red); π-π stacking, where aromatic ligands interact non-covalently with the conjugated structure of dye molecules; hydrogen bonding, where functional groups such as NH2 and -COOH form a hydrogen bond network with -OH and N=N in the dye; and pore confinement effect, where nanoscale pores smaller than 2 nm produce a size sieving and concentration effect on dye molecules. Studies have shown that MOFs have the highest adsorption efficiency for anionic dyes in the pH range of 7-9, and some materials (e.g., PSP-MIL-53) can achieve simultaneous removal of seawater desalination and dyes within 30 min, meeting WHO drinking water standards. Summary of the Invention

[0005] Based on the above reasons, in order to further purify drinking water, the first objective of this invention is to provide a method for preparing a hexapeptide anionic metal-organic framework material with a single crystal structure. Under solvothermal reaction conditions, by controlling the amount of zinc ion precursor added and using a specific regulator, the interpenetration of the coordination structure is achieved, thereby obtaining a hexapeptide anionic metal-organic framework material.

[0006] The second objective of this invention is to provide a hexagonal interpenetrating anionic metal-organic framework material with a single-crystal structure. The six sets of structures with the same coordination mode are formed by interpenetrating each other through different interpenetration methods, and have good crystallinity and stability.

[0007] The third objective of this invention is to provide an application of a hexagonal interpenetrating anionic metal-organic framework material with a single-crystal structure in the adsorption of organic dyes. The hexagonal interpenetrating anionic metal-organic framework material is a negative ion framework material and has excellent adsorption effect on organic dyes.

[0008] The first objective of this invention can be achieved by adopting the following technical solution:

[0009] A method for preparing a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure includes the following steps:

[0010] The ligand with the structure shown in Formula I and the precursor of divalent zinc ions are reacted in a solvothermal manner in the presence of 1-ethyl-3-methylimidazolium tetrafluoroborate at a molar ratio of 1:(4.5-5.5) to obtain the hexapeptide anionic metal-organic framework material with a single crystal structure.

[0011] ;

[0012] Where R is n is 0, 1 or 2.

[0013] Furthermore, the divalent zinc ion precursor is a compound of divalent zinc ions in acetic acid, hydrochloric acid, sulfuric acid, or nitric acid, or its hydrate.

[0014] Furthermore, the amount of 1-ethyl-3-methylimidazolium tetrafluoroborate added is 1-5% of the solvent volume.

[0015] Furthermore, the solvent for the reaction is a mixed solvent of NaOH methanol solution and ethylenediamine, wherein the volume ratio of NaOH methanol solution to ethylenediamine is 1:(0.5-2).

[0016] The molar concentration of NaOH in a NaOH methanol solution is 200-278 mmol / L. –1 .

[0017] Furthermore, the conditions for the solvothermal reaction are:

[0018] The molar-volume ratio of the monomer to the solvent in the structure shown in Formula I is (1.5-3) μmol: 1 mL;

[0019] The reaction temperature is 110-130℃; the reaction time is 12-96h.

[0020] Furthermore, the reaction includes a separation and washing process; after separation, the solid is washed with methanol and vacuum dried to obtain the hexapeptide anionic metal-organic framework material with a single-crystal structure.

[0021] The second objective of this invention can be achieved by adopting the following technical solution:

[0022] A six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure is prepared by the above-mentioned preparation method of the six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure.

[0023] Furthermore, in the hexapeptide anionic metal-organic framework material with a single-crystal structure, the six groups of structures with the same coordination mode are interpenetrated with each other through different interpenetration methods.

[0024] Furthermore, the crystal system of the six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure is triclinic, and its space group is [missing information]. P -1; the lattice parameters are a=20.81Å, b=24.22Å, c=31.07Å, α=112.14°, β=92.16°, γ=91.90°.

[0025] The third objective of this invention can be achieved by adopting the following technical solution:

[0026] Application of hexagonal interpenetrating anionic metal-organic frameworks with single-crystal structures in the adsorption of cationic organic dyes in drinking water.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. This application discloses a method for preparing a hexapeptide anionic metal-organic framework material with a single-crystal structure. An organic ligand is coordinated with zinc ions. By controlling the amount of zinc ion precursor added and using a specific modifier, the coordination structures interpenetrate through different interpenetration mechanisms to form a hexapeptide anionic metal-organic framework material. The solvothermal reaction conditions are mild and not harsh, making it suitable for large-scale preparation.

[0029] 2. The present application discloses a hexapeptide anionic metal-organic framework material with a single-crystal structure, which has a highly conjugated structure of triphenylene and ZnS4 sites, and has a hexapeptide metal-organic framework with good crystallinity and stability; it is also an anionic framework material that promotes the adsorption of cationic organic dyes in drinking water. Attached Figure Description

[0030] Figure 1 It is the smallest asymmetric unit of the MOF Zn-S single crystal structure;

[0031] Figure 2 This is a diagram of the six-fold interpenetrating single-crystal structure of MOF Zn-S along the b-axis;

[0032] Figure 3 This is a diagram of the six-fold interpenetrating single-crystal structure of MOF Zn-S along the c-axis;

[0033] Figure 4 A partial view of the MOF Zn-S single crystal structure;

[0034] Figure 5 The values ​​measured in the MOF Zn-S experiment and the refined X-ray diffraction spectrum;

[0035] Figure 6 Comparison of Fourier transform infrared spectra of MOF Zn-S and its ligands;

[0036] Figure 7 TGA curves of MOF Zn-S in air and N2 atmosphere;

[0037] Figure 8 shows the X-ray photoelectron spectrum of MOF Zn-S;

[0038] Figure 9 The UV-Vis absorption spectra of methylene blue adsorbed on MOF Zn-S at different times. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] Traditional adsorption materials (such as activated carbon, zeolite, and biochar) have limited specific surface area and mismatched pore size distribution, resulting in generally low adsorption capacity for organic dyes, far lower than that of MOF materials. Furthermore, their adsorption equilibrium time is relatively long, making it difficult to meet the demands of high-efficiency water purification. They also lack molecular recognition capabilities and are susceptible to natural organic matter (such as humic acid) and inorganic ions (CaO) in complex water conditions. 2+ Mg 2+ Competition for adsorption sites. For zeolites, hardness ions can clog zeolite pores, significantly reducing their ion exchange efficiency for anionic dyes; while the regeneration of materials such as activated carbon relies on high-temperature pyrolysis (>800℃), which is energy-intensive and costly; waste saturated carbon is classified as hazardous waste (HW49 category), and improper disposal can easily lead to the secondary release of organic dyes, creating environmental liability risks. Therefore, this application provides a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure, its preparation method, and its applications.

[0041] A method for preparing a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure includes the following steps:

[0042] The ligand with the structure shown in Formula I and the precursor of divalent zinc ions are reacted in a solvothermal manner in the presence of 1-ethyl-3-methylimidazolium tetrafluoroborate at a molar ratio of 1:(4.5-5.5) to obtain the hexapeptide anionic metal-organic framework material with a single crystal structure.

[0043] ;

[0044] Where R is n is 0, 1 or 2.

[0045] Zinc ions coordinate with ligands primarily composed of triphenylene to assemble into metal-organic frameworks (MOFs). The short S-Zn bonds and the rigid plane of triphenylene allow for a three-dimensional spatial structure when triphenylene coordinates with metal ions. Multiple extended structures interpenetrate within this space, with the multiplicity of interpenetration depending on the spatial thickness of the extended structure. This application presents a six-fold interpenetrating anionic MOF with a single-crystal structure. Increasing the amount of zinc ions promotes the extension of the extended structure; the addition of 1-ethyl-3-methylimidazolium tetrafluoroborate regulates the interpenetration structure and crystal form. The smallest asymmetric unit of the single-crystal structure is as follows: Figure 1 As shown; the diagram of the six-fold interpenetrating single crystal structure along the b-axis is as follows. Figure 2As shown; the diagram of the six-fold interpenetrating single crystal structure along the c-axis is as follows. Figure 3 As shown; partial view of the single crystal structure is as follows Figure 4 As shown.

[0046] As one embodiment, the divalent zinc ion precursor is a compound of divalent zinc ions in acetic acid, hydrochloric acid, sulfuric acid or nitric acid and its hydrate.

[0047] In one embodiment, the amount of 1-ethyl-3-methylimidazolium tetrafluoroborate added is 1-5% of the solvent volume. The addition of 1-ethyl-3-methylimidazolium tetrafluoroborate allows its anionic properties to form competitive hydrogen bonds with the functional groups on the MOF ligands, influencing the conformation and arrangement of the ligands; it provides a different crystallization microenvironment than traditional solvents, stabilizing high-energy crystal planes and potentially corresponding to different crystal forms; and it can temporarily occupy framework space, guiding the formation of specific channels or preventing common close-packed structures. Therefore, the metal-organic framework material of this application is a six-fold interpenetrating structure with a single-crystal structure.

[0048] In one embodiment, the solvent for the reaction is a mixed solvent of NaOH methanol solution and ethylenediamine, wherein the volume ratio of NaOH methanol solution to ethylenediamine is 1:(0.5-2).

[0049] The molar concentration of NaOH in a NaOH methanol solution is 200-278 mmol / L. –1 .

[0050] As one implementation method, the conditions for the solvothermal reaction are:

[0051] The molar-volume ratio of the monomer to the solvent in the structure shown in Formula I is (1.5-3) μmol: 1 mL;

[0052] The reaction temperature is 110-130℃; the reaction time is 12-96h.

[0053] As one implementation method, the reaction includes a separation and washing process; after separation, the solid is washed with methanol and vacuum dried to obtain the hexapeptide anionic metal-organic framework material with a single crystal structure.

[0054] A six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure is prepared by the above-mentioned preparation method of the six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure.

[0055] In one embodiment, the six groups of structures with the same coordination mode in the hexagonal interpenetrating anionic metal-organic framework material with a single crystal structure interpenetrate with each other in different ways.

[0056] As one implementation method, the six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure has a triclinic crystal system and a space group of [missing information]. P -1; the lattice parameters are a=20.81Å, b=24.22Å, c=31.07Å, α=112.14°, β=92.16°, γ=91.90°.

[0057] Application of hexagonal interpenetrating anionic metal-organic frameworks with single-crystal structures in the adsorption of cationic organic dyes in drinking water.

[0058] The following specific examples will provide further details. Example 1

[0059] 10 μmol of ligand 2,3,6,7,10,11-hexa(pentanoylthio)triphenylene, 50 μmol of anhydrous Zn(OAc)2, and 0.6 mmol of NaOH were weighed into a glass tube. 2.5 ml of ultradry methanol, 2.5 ml of ethylenediamine, and 0.7 ml of 1-ethyl-3-methylimidazolium tetrafluoroborate were then pipetted into the glass tube. The mixture was frozen in liquid nitrogen, evacuated, and thawed three times. Finally, the glass tube was sealed under vacuum with an oxyhydrogen flame. The mixture was heated at 120 °C for 48 h in an oven and then naturally cooled to room temperature to obtain bulk crystals. The crystals were filtered, washed with methanol, and evacuated at room temperature to obtain the hexapeptide anionic metal-organic framework material with a single-crystal structure, named MOF Zn-S. Example 2

[0060] 10 μmol of ligand 2,3,6,7,10,11-hexa(pentanoylthio)triphenylene, 45 μmol of anhydrous Zn(OAc)2, and 0.44 mmol of NaOH were weighed into a glass tube. 2.2 ml of ultradry methanol, 1.1 ml of ethylenediamine, and 0.16 ml of 1-ethyl-3-methylimidazolium tetrafluoroborate were then pipetted into the glass tube. The mixtures were frozen in liquid nitrogen, evacuated, and thawed three times. Finally, the glass tube was sealed under vacuum with an oxyhydrogen flame. The mixture was heated at 110 °C for 96 h in an oven and then naturally cooled to room temperature to obtain bulk crystals. The crystals were filtered, washed with methanol, and evacuated at room temperature to obtain the hexapeptide anionic metal-organic framework material with a single-crystal structure. Example 3

[0061] 10 μmol of ligand 2,3,6,7,10,11-hexa(pentanoylthio)triphenylene, 55 μmol of anhydrous Zn(OAc)2, and 0.64 mmol of NaOH were weighed into a glass tube. 2.3 ml of ultradry methanol, 4.4 ml of ethylenediamine, and 0.67 ml of 1-ethyl-3-methylimidazolium tetrafluoroborate were then pipetted into the glass tube. The mixtures were frozen in liquid nitrogen, evacuated, and thawed three times. Finally, the glass tube was sealed under vacuum with an oxyhydrogen flame. The mixture was heated at 130 °C for 12 h in an oven and then naturally cooled to room temperature to obtain bulk crystals. The crystals were filtered, washed with methanol, and evacuated at room temperature to obtain the hexapeptide anionic metal-organic framework material with a single-crystal structure.

[0062] Test example:

[0063] (1) X-ray diffraction (XRD) was performed on the MOF Zn-S prepared in Example 1; the results were refined by comparing the XRD with the theoretical values ​​calculated using a single-crystal diffractometer. Figure 5 As shown in the figure; the crystallographic parameters and results of MOF Zn-S are shown in Table 1.

[0064]

[0065] The X-ray diffraction (XRD) spectra were refined with theoretical values ​​calculated using a single-crystal diffractometer. The two values ​​showed a good fit, indicating high purity and good crystallinity of the Zn-S phase. Zn-S was characterized using Bruker X-ray single-crystal diffraction, revealing a sixfold interpenetrating structure, a triclinic crystal system, and a space group of [space group missing]. P -1. The lattice parameters are a = 20.81 Å, b = 24.22 Å, c = 31.07 Å, α = 112.14°, β = 92.16°, γ = 91.90°. Zn-S are connected by twisted tetrahedra, four-coordinated ZnS4 nodes, and are asymmetrically interconnected. (Example...) Figure 1 As shown.

[0066] (2) The MOF Zn-S prepared in Example 1 was subjected to infrared spectroscopy analysis. The infrared spectrum is shown in the figure below. Figure 6 As shown.

[0067] from Figure 6 In the infrared spectrum, it can be observed that, under Fourier transform infrared (FT-IR) spectroscopy, the C=O and saturated CH stretching signals of the protective thioester chain (1701 and 2850-3000 cm⁻¹) are significant. -1 The disappearance of ligand S indicates that the interaction between ligand S and metal Zn is implied. 2+ Successful matching.

[0068] (3) Thermogravimetric analysis was performed on the MOF Zn-S prepared in Example 1 under nitrogen and air atmospheres, respectively. The thermogravimetric curves are shown in the figure. Figure 7As shown.

[0069] From thermogravimetric analysis Figure 7 It can be seen that MOF Zn-S experiences a small amount of weight loss before 220℃, mainly due to the loss of guest molecules in the pores, such as water molecules; it retains 93.0% of its weight, indicating that it has thermal stability.

[0070] (4) X-ray photoelectron spectroscopy was performed on the MOF Zn-S prepared in Example 1. The X-ray photoelectron spectrum is shown below. Figure 8 As shown.

[0071] The spectrum shows the signals of C, S, Zn, N, and Na; the Zn 2p spectrum shows Zn 2+ 2 p 1 / 2 and 2 p 3 / 2 The signal is centered at 1045.13 and 1022.08 eV.

[0072] Experimental example:

[0073] To investigate the adsorption performance of Zn-S for the cationic organic dye (methylene blue) in drinking water, 5 mg of the Zn-S crystal sample prepared in Example 1 was weighed into a glass bottle under room temperature and light-protected conditions, and 5 mL of 0.2 mM methylene blue aqueous solution was added and stirred. Multiple reactions were prepared under the same conditions, and samples were taken and photographed at different time points. It was found that the color of the methylene blue aqueous solution gradually decreased between 0 h and 4 h, and finally almost disappeared at approximately 4 h. UV-Vis absorption spectroscopy was then performed, and the absorbance value gradually decreased, eventually dropping to almost zero at approximately 4 h. Figure 8 As shown.

[0074] To investigate the adsorption mechanism of Zn-S for cationic organic dyes (methylene blue) in drinking water, we compared the adsorption performance of Zn-S materials with that of previously reported triple-interpenetrated [ZnS4] node MOF materials. Under the same conditions, the adsorption effect of the triple-interpenetrated [ZnS4] node MOF material for methylene blue was not ideal; no significant color change was observed within 4 hours of adsorption, and complete adsorption was only achieved after 12 hours. This may be because the framework charge of the triple-interpenetrated [ZnS4] node MOF material is relatively small, and adsorption can only be achieved through the pore effect of the MOF itself. In contrast, the framework of the Zn-S material carries a large negative charge, which can promote the adsorption of methylene blue through the combined effect of the negative framework charge and the pore effect of the MOF itself.

[0075] In summary, this invention provides a method for preparing a hexapeptide anionic metal-organic framework material with a single-crystal structure. The organic ligand is coordinated with zinc ions. By controlling the amount of zinc ion precursor added and using a specific modifier, the coordination structures interpenetrate with each other through different interpenetration mechanisms, forming a hexapeptide anionic metal-organic framework material. The large negative charge and abundant porous structure of the hexapeptide anionic metal-organic framework material promote the adsorption of cationic organic dyes in drinking water.

[0076] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure, characterized in that, Includes the following steps: The ligand with the structure shown in Formula I and the precursor of divalent zinc ions are reacted in a solvothermal manner in the presence of 1-ethyl-3-methylimidazolium tetrafluoroborate at a molar ratio of 1:(4.5-5.5) to obtain the hexapeptide anionic metal-organic framework material with a single crystal structure. ； Where R is n is 0, 1 or 2.

2. The method for preparing a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure according to claim 1, characterized in that, The divalent zinc ion precursor is a compound of divalent zinc ions in acetic acid, hydrochloric acid, sulfuric acid, or nitric acid, or its hydrate.

3. The method for preparing a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure according to claim 1, characterized in that, The amount of 1-ethyl-3-methylimidazolium tetrafluoroborate added is 1-5% of the solvent volume.

4. The method for preparing a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure according to claim 1, characterized in that, The reaction solvent is a mixture of NaOH methanol solution and ethylenediamine, wherein the volume ratio of NaOH methanol solution to ethylenediamine is 1:(0.5-2). The molar concentration of NaOH in a NaOH methanol solution is 200-278 mmol / L. –1 .

5. The method for preparing a hexapeptide anionic metal-organic framework material with a single-crystal structure according to claim 1, characterized in that, The conditions for a solvothermal reaction are: The molar-volume ratio of the monomer to the solvent in the structure shown in Formula I is (1.5-3) μmol: 1 mL; The reaction temperature is 110-130℃; the reaction time is 12-96h.

6. The method for preparing a six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure according to claim 1, characterized in that, The reaction includes a separation and washing process; after separation, the solid is washed with methanol and vacuum dried to obtain the hexapeptide anionic metal-organic framework material with a single crystal structure.

7. A six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure, characterized in that, It is prepared by the preparation method of the hexagonal interpenetrating anionic metal-organic framework material with a single crystal structure as described in any one of claims 1-6.

8. The six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure according to claim 7, characterized in that, In the hexagonal interpenetrating anionic metal-organic framework material with a single-crystal structure, six groups of structures with the same coordination mode interpenetrate with each other in different ways.

9. The six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure according to claim 7, characterized in that, The crystal system of the six-fold interpenetrating anionic metal-organic framework material with a single-crystal structure is triclinic, and its space group is [missing information]. P -1; the lattice parameters are a=20.81Å, b=24.22Å, c=31.07Å, α=112.14°, β=92.16°, γ=91.90°.

10. The application of the hexagonal interpenetrating anionic metal-organic framework material with a single-crystal structure as described in any one of claims 1-9 in the adsorption of cationic organic dyes in drinking water.

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