A multifunctional ionic porous organic cage material, its preparation method and application in chromium adsorption

Abstract

The present invention discloses a multifunctional ionic porous organic cage material, its preparation method and chromium adsorption application, belonging to the technical field of porous organic materials. In the present invention, a porous organic cage material NKPOC-PH is synthesized using tetraaldehyde m-cyclocucurbit[4]arene and pyridine-3,5-dicarboxylic dihydrazide as reaction monomers, and then it is modified with methyl iodide to obtain ionic NKPOC-PH(I)Me. The present invention uses an easily modified porous organic cage as the substrate to construct triple synergistic adsorption sites of redox, coordination and electrostatics. Pyridine groups in the material are used as the introduction points of electrostatic sites, hydrazide linking groups as redox sites, and nitrogen-rich sites to adsorb dichromate ions through coordination. The obtained ionic porous cage can achieve an ultra-high chromium adsorption performance with a saturated adsorption capacity exceeding 1.3 g / g under acidic (pH = 3-4) aqueous phase conditions. The ionic porous organic cage material described in the present invention provides a new solution for adsorbing dichromate ions under aqueous phase conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of porous organic materials, and particularly relates to a preparation method of a multifunctional ionic porous organic cage material having electrostatic, redox and coordination sites and its application in efficiently adsorbing dichromate Background Art

[0002] Chromium elements and their compounds play an important role in the fields of metallurgy, metal processing, electroplating industry, artificial leather, paint, printing and dyeing, pigments, etc. Chromium can be found in various media of the environment, including the atmosphere, water bodies, and soil. Since coal contains about 10 mg / kg of chromium elements, the waste gas discharged from smelting and coal combustion also contains chromium. There are two forms of chromium in water: trivalent chromium and hexavalent chromium. Toxic hexavalent chromium is a representative of toxic and harmful pollutants among heavy metals. Chromium-containing wastewater is mainly acidic (pH = 3 - 4) and mainly exists in the form of dichromate in the environment. Hexavalent chromium is a swallowed poison / highly toxic inhalant. Skin contact may cause sensitivity; it is more likely to cause genetic defects. Inhalation may cause cancer and pose a persistent danger to the environment. Therefore, it is of great significance to develop an efficient and economical chromium adsorbent.

[0003] Currently, common treatment methods for chromium pollution include precipitation method, redox method, electrolysis method, adsorption method, ion exchange method, etc. Among them, the adsorption method has been widely used in chromium pollution due to its easy operation and high efficiency. However, since most adsorbents use a single action site such as an ionic site with electrostatic interaction, a coordination site rich in nitrogen, etc., the current chromium adsorbents still have problems such as low adsorption capacity, high cost, and poor stability.

[0004] Porous organic cages, a kind of hollow zero-dimensional cage-like molecular material. Due to its high specific surface area, easy solubility and modification characteristics, it has attracted wide attention in many fields. Due to the flexibility of its configuration, porous organic cages can be designed reasonably to have both stability, functionality and crystallinity, which makes porous organic cages have broad application prospects in environmental applications such as adsorption separation, energy storage, sensing, catalysis, and pollutant capture. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for efficiently adsorbing dichromate under aqueous phase conditions, and solve the problems of low adsorption capacity and poor stability of current chromium adsorbents by preparing an ionic porous organic cage material having triple functional sites of electrostatic interaction, coordination interaction and redox interaction.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] An ion-functionalized porous organic cage material, the structure of the organic porous material and its synthetic route and structure after modification are as follows:

[0008]

[0009] NKPOC-PH has good crystallinity and obvious pore structure. After ion modification, NKPOC-PH(I)Me can reach a saturated adsorption capacity of more than 1.3 g / g under aqueous phase conditions. The specific preparation steps are as follows:

[0010] A. Preparation method of NKPOC-PH

[0011] Add tetraal-dehyde m-cyclo-calix[4]arene, pyridine-3,5-dicarboxylic dihydrazide and the reaction solvent into a reaction vessel, mix the mixed solution evenly, place the sealed vessel in an oven to react for a certain time, and leave the obtained solution open in a crystallizing dish containing a diffusion solvent to diffuse for a period of time. The obtained product is filtered, washed and dried to obtain the product NKPOC-PH.

[0012] Among them, the tetraal-dehyde m-cyclo-calix[4]arene refers to the following synthetic route, and the specific synthesis method refers to the literature J.Org.Chem.2013,78,11597-11601.

[0013]

[0014] For the synthesis of the said NKPOC-PH, the reaction solvent is selected as DMF and mesitylene, and the molar ratio of the ligand to the solvent is tetraal-dehyde m-cyclo-calix[4]arene:pyridine-3,5-dicarboxylic dihydrazide:DMF:mesitylene = 1:2:551:153. The reaction temperature is 100 °C and the reaction time is 24 h.

[0015] Specifically: Add 20 mg (0.047 mmol) of tetraal-dehyde m-cyclo-calix[4]arene, 18.4 mg (0.097 mmol) of pyridine-3,5-dicarboxylic dihydrazide, 2 ml of DMF and 1 ml of mesitylene into a 20 ml glass bottle, seal it with a plastic bottle cap and ultrasonicate for 10 min. Place the sealed glass bottle in an oven at 100 °C to react for 24 h, place the obtained glass bottle containing the solution in a crystallizing dish containing 5 ml of methanol, seal the crystallizing dish and diffuse at 20 °C for 14 days. The obtained product is filtered, washed and dried to obtain the product NKPOC-PH.

[0016] In addition to the above preferred methods, the reaction solvent of the present invention can also be selected from DMF and one of toluene, mesitylene, chlorobenzene, nitrobenzene, p-xylene, m-xylene, and o-xylene; the molar ratio of the ligand to the solvent can be selected as tetraal-dehyde meta-cyclo[4]arene:pyridine-3,5-dicarboxylic dihydrazide:DMF = 1:1-5:200-10000, the reaction temperature can be set at 80-150 °C, and the reaction time is 8-120 h. The diffusion solvent can be selected from one or more of ethanol, ether, and tetrahydrofuran, and the molar ratio of the amount of the solvent to the reaction solvent is 1:1-10. The temperature during diffusion is 5-40 °C, and the time is 36-720 h.

[0017] B. Preparation method of NKPOC-PH(I)Me

[0018] Add NKPOC-PH, methyl iodide, and the reaction solvent into a reaction vessel, stir the reactants for a certain time, and the obtained product is subjected to post-treatment such as filtration, washing, and drying to obtain the product NKPOC-PH(I)Me.

[0019] Furthermore, for the synthesis of NKPOC-PH(I)Me, the reaction solvent is selected as ethanol, and the molar ratio of the reactants to the solvent is NKPOC-PH:methyl iodide:ethanol = 1:10:19,692. The stirring reaction temperature is 50 °C, the stirring environment is a nitrogen atmosphere, and the stirring time is 24 h.

[0020] Specifically: Add 100 mg (0.0275 mmol) of NKPOC-PH, 17 μL (0.275 mmol) of methyl iodide, and 30 ml of ethanol into a 150 ml pressure-resistant bottle. After introducing nitrogen, stir at 50 °C for 24 h. The obtained product is subjected to filtration, washing, and drying treatments to obtain the product NKPOC-PH(I)Me. In addition to the above preferred methods, the solvent can be selected from one or more of methanol, acetonitrile, and tetrahydrofuran; the molar ratio of the reactants to the solvent can be selected as NKPOC-PH:methyl iodide:solvent = 1:1.5-100:10000-100000; the stirring temperature can be set at 20-80 °C; the stirring environment is air or argon atmosphere, and the reaction time is 2-120 h.

[0021] Adsorption of the ionic porous organic cage material described in the present invention by dichromate.

[0022] Furthermore, it is used for the adsorption of dichromate under the aqueous phase conditions of pH = 3-4.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The present invention discloses a method for efficiently adsorbing dichromate under acidic (pH = 3) aqueous phase conditions using an ionic porous organic cage material with redox and coordination multifunctionalization. Compared with the reported chromium adsorption materials, the porous organic cage material designed in the present invention has the advantages of simple synthesis, batch production, multiple active sites, and high adsorption capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the cage molecular structure diagram of NKPOC-PH.

[0026] Figure 2 It is the crystal packing diagram of NKPOC-PH observed along the c-axis.

[0027] Figure 3 It is the carbon dioxide adsorption diagram of NKPOC-PH at 195K.

[0028] Figure 4 It is the PXRD diagram of NKPOC-PH.

[0029] Figure 5 It is the infrared spectrum diagram of NKPOC-PH(I)Me.

[0030] Figure 6 It is the standard curve diagram for preparing the dichromate solution.

[0031] Figure 7 It is the chromium adsorption diagram of NKPOC-PH(I)Me at different concentrations. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the objectives, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not limited to the present invention.

[0033] Example 1

[0034] 200 mg (0.47 mmol) of tetraaldehyde m-cyclophane[4]arene, 184 mg (0.94 mmol) of pyridine-3,5-dicarboxylic dihydrazide, 20 ml of DMF and 10 ml of mesitylene were added to a 150 ml pressure-resistant bottle, and after sealing, it was ultrasonically treated for 30 min. The sealed glass bottle was placed in an oven at 100 °C for reaction for 24 h, and the glass bottle containing the solution was placed in a crystallization dish containing 50 ml of methanol. After sealing the crystallization dish, it was diffused at 20 °C for 14 days. The obtained product was filtered, washed, and dried to obtain the product NKPOC-PH.

[0035] Figure 1Figure 0 shows the cage-like molecular structure diagram corresponding to Example 1. It can be seen from the figure that the prepared porous organic cage NKPOC-PH is a porous organic cage material with a 3+6 configuration.

[0036] Figure 2 Figure 4 shows the crystal packing diagram observed along the c-axis corresponding to Example 1. It can be seen from the figure that the prepared porous organic cage material NKPOC-PH has one-dimensional pores, which is beneficial to the diffusion of adsorbates within the porous organic cage material.

[0037] Table 1 shows the structural crystal data table corresponding to Example 1.

[0038] Table 1

[0039]

[0040]

[0041] Figure 3 Figure 20 shows the carbon dioxide adsorption diagram of NKPOC-PH at 195K. It can be seen from the figure that NKPOC-PH has good carbon dioxide adsorption capacity.

[0042] Figure 4 Figure 24 shows the PXRD diagram of NKPOC-PH. It can be seen that the obtained porous organic cage material has good crystallinity. The above results also prove that NKPOC-PH can be prepared by simple solvothermal and diffusion crystallization methods to obtain good porosity, without the need for complex operations such as reaction kettles, pyrex tubes, and vacuum pumping required in the preparation of traditional MOFs by solvothermal methods.

[0043] Example 2

[0044] 100 mg (0.0275 mmol) of NKPOC-PH obtained in Example 1, 17 μL (0.275 mmol) of iodomethane, and 30 ml of ethanol were added to a 150 ml pressure-resistant bottle. After purging with nitrogen, the mixture was stirred at 50 °C for 24 h. The obtained product was filtered, washed, and dried to obtain the product NKPOC-PH(I)Me.

[0045] Figure 5 Figure 34 shows the infrared spectrum diagram corresponding to Example 2. It can be seen from the figure that the appearance of the -C-N- infrared characteristic peak at a wavenumber of 1330 cm -1 and the -CH -1 infrared characteristic peak at a wavenumber of 3024 cm 3 confirm the successful synthesis of the porous organic cage material NKPOC-PH(I)Me. The appearance of the -C=N- at a wavenumber of 1612 cm -1 in the infrared spectrum indicates that the connecting bonds of the cage are not damaged.

[0046] Example 3

[0047] Standard curve of the chromium adsorption experiment samples:

[0048] To test the adsorption performance of the porous organic cage material synthesized in Example 2 above for dichromate ions, chromium standard solutions with concentrations of 20 ppm, 10 ppm, 5 ppm, 2.5 ppm, 1.25 ppm, and 0.625 ppm were prepared. Weigh 56.57 mg of potassium dichromate and dissolve it in 943.43 mg of ultrapure water to obtain a 20 ppm chromium standard solution; use the two-fold dilution method to sequentially obtain 10 ppm, 5 ppm, 2.5 ppm, 1.25 ppm, and 0.625 ppm chromium standard solutions. Before testing, all the prepared standard solutions were diluted by a factor of 1000 to obtain chromium standard solutions of 20 ppb, 10 ppb, 5 ppb, 2.5 ppb, 1.25 ppb, and 0.625 ppb.

[0049] Figure 6 It is the standard curve corresponding to Example 3.

[0050] Example 4

[0051] Aqueous phase chromium adsorption experiment:

[0052] To test the adsorption effect of the porous organic cage material NKPOC-PH(I)Me on chromium at different concentrations, the adsorbent synthesized in Example 2 above was used to conduct aqueous phase chromium adsorption experiments at different concentrations. In this example, the concentrations of the simulated chromium wastewater were 5 ppm, 10 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, 600 ppm, and 800 ppm; and in order to simulate the real chromium wastewater adsorption scenario, hydrochloric acid and pH were used to make the pH of all solutions equal to 3. Place 10 mg of NKPOC-PH(I)Me into 50 ml of the above-mentioned simulated chromium wastewater respectively, and shake it on a shaker at room temperature for 8 h. Take the adsorbed simulated chromium wastewater and dilute it by a factor of 1000 by the gravimetric method. The concentration of the adsorbed simulated chromium wastewater was obtained by ICP-MS. From the formula:

[0053]

[0054] c 0 —Initial concentration; c a —Concentration after adsorption; v—Volume of the solution; m—Mass of the adsorbent

[0055] The adsorption amounts at each obtained concentration are shown in Figure 7 , and the adsorption capacity of NKPOC-PH(I)Me reached 1.356 g / g at a concentration of 800 ppm, proving its excellent chromium adsorption ability.

[0056] Example 5

[0057] 2 g (4.7 mmol) of tetraaldehyde m -calix[4]arene, 1.84 g (9.4 mmol) of pyridine-3,5-dicarbohydrazide, 200 ml of DMF and 100 ml of mesitylene were added to a 500 ml three-necked flask and sonicated for 30 min. The three-necked flask was placed in an oil bath at 100 °C and reacted for 24 h. The resulting solution was dispensed into 20 ml glass bottles and left open in a crystallization dish containing 50 ml of methanol. The crystallization dish was sealed and diffused at 20 °C for 14 days. The obtained product was filtered, washed and dried to obtain the product NKPOC-PH.

[0058] Example 6

[0059] 100 mg (0.0275 mmol) of NKPOC-PH obtained in Example 1, 17 μL (0.275 mmol) of methyl iodide and 30 ml of methanol were added to a 150 ml pressure-resistant bottle. After purging with nitrogen, the mixture was stirred at 50 °C for 24 h. The obtained product was filtered, washed and dried to obtain the product NKPOC-PH(I)Me.

[0060] Example 7

[0061] 200 mg (0.47 mmol) of tetraaldehyde m -calix[4]arene, 184 mg (0.94 mmol) of pyridine-3,5-dicarbohydrazide, 20 ml of DMF and 10 ml of toluene were added to a 150 ml pressure-resistant bottle, which was then sealed and sonicated for 30 min. The sealed glass bottle was placed in an oven at 100 °C and reacted for 48 h. The glass bottle containing the solution was placed in a crystallization dish containing 50 ml of ethanol. The crystallization dish was sealed and diffused at 20 °C for 10 days. The obtained product was filtered, washed and dried to obtain the product NKPOC-PH.

[0062] Example 8

[0063] 200 mg (0.055 mmol) of NKPOC-PH obtained in Example 1, 17 μL (0.55 mmol) of methyl iodide and 70 ml of acetonitrile were added to a 150 ml pressure-resistant bottle. The mixture was stirred at 50 °C for 24 h. The obtained product was filtered, washed and dried to obtain the product NKPOC-PH(I)Me.

[0064] The present invention designs and synthesizes an ionic porous organic cage NKPOC-PH(I)Me, which has the advantages of simple synthesis method, batch production, large chromium adsorption capacity at multiple active sites, etc. compared with the reported chromium adsorption materials, and can achieve efficient adsorption of chromium under acidic (pH = 3) aqueous phase conditions. This material has a simpler synthesis process compared with MOFs and POPs, does not require complex synthesis equipment such as reaction kettles and pyrex sealed tubes, and complicated operations such as vacuum pumping, and can realize batch preparation, laying a foundation for the actual industrial application of the material. In summary, the ionic porous organic cage material NKPOC-PH(I)Me designed and synthesized by the present invention with redox and coordination multifunctionalization is a good choice for industrializing chromium adsorption materials in terms of product performance.

[0065] The above description of the embodiments is to enable those of ordinary skill in the art to understand and apply the present invention. Those skilled in the art can easily make various modifications to these embodiments, including but not limited to modifying the solvent used for the ligand, modifying the reaction ligand ratio, solvent ratio, reaction time, temperature, etc., and applying the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the embodiments described herein, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention as disclosed should be within the protection scope of the present invention.

Claims

1. A multifunctional ionic porous organic cage material, characterized in that, the structure of the porous organic cage material NKPOC-PH(I)Me is as follows: This material is obtained by the following method: A. Preparation method of NKPOC-PH Add tetraaldehyde m-cyclophane[4]arene, pyridine-3,5-dicarboxylic dihydrazide and a reaction solvent into a reaction vessel, mix the mixed solution well, place the sealed vessel in an oven to react for a certain period of time, and leave the obtained solution open in a crystallization dish containing a diffusion solvent to diffuse for a period of time. The obtained product is filtered, washed and dried to obtain the product NKPOC-PH; B. Preparation method of NKPOC-PH(I)Me Add NKPOC-PH, methyl iodide and a reaction solvent into a reaction vessel, stir the reactants for a certain period of time, and the obtained product is filtered, washed and dried to obtain the product NKPOC-PH(I)Me.

2. A preparation method of the multifunctional ionic porous organic cage material according to claim 1, characterized in that, the steps are as follows: A. Preparation method of NKPOC-PH Add tetraaldehyde m-cyclophane[4]arene, pyridine-3,5-dicarboxylic dihydrazide and a reaction solvent into a reaction vessel, mix the mixed solution well, place the sealed vessel in an oven to react for a certain period of time, and leave the obtained solution open in a crystallization dish containing a diffusion solvent to diffuse for a period of time. The obtained product is filtered, washed and dried to obtain the product NKPOC-PH; B. Preparation method of NKPOC-PH(I)Me Add NKPOC-PH, methyl iodide and a reaction solvent into a reaction vessel, stir the reactants for a certain period of time, and the obtained product is filtered, washed and dried to obtain the product NKPOC-PH(I)Me.

3. According to the preparation method of the multifunctional ionic porous organic cage material described in claim 2, characterized in that, in the preparation method of NKPOC-PH, the reaction solvent is DMF and one of, but not limited to, toluene, mesitylene, chlorobenzene, nitrobenzene, p-xylene, m-xylene, o-xylene; the reaction vessel includes, but is not limited to, a glass bottle, a round-bottom flask or a pressure-resistant bottle, and the mixing method includes, but is not limited to, stirring or ultrasonic wave.

4. According to the preparation method of the multifunctional ionic porous organic cage material described in claim 2, characterized in that, in the preparation method of NKPOC-PH, the molar ratio of tetraaldehyde m-cyclophane[4]arene, pyridine-3,5-dicarboxylic dihydrazide and DMF is: 1:1-5:200-10000, the reaction temperature of the oven is 80-150 °C, and the reaction time is 8-120 h.

5. According to the preparation method of the multifunctional ionic porous organic cage material described in claim 2, characterized in that, in the preparation method of NKPOC-PH, the diffusion solvent is one or several of methanol, ethanol, ether, tetrahydrofuran, and the molar ratio of the amount of the diffusion solvent to the reaction solvent is 1:1-10. The temperature during diffusion is 5-40 °C, and the time is 36-720 h.

6. According to the preparation method of the multifunctional ionic porous organic cage material described in claim 2, characterized in that, In the preparation method of NKPOC-PH, the temperature of the drying treatment is 50 to 180 °C.

7. The preparation method of the multifunctional ionic porous organic cage material according to claim 2, characterized in that, in the preparation method of NKPOC-PH(I)Me, the reaction solvent includes but is not limited to one or more of methanol, ethanol, acetonitrile, and tetrahydrofuran, and the reaction vessel includes but is not limited to a glass bottle, a round-bottom flask, or a pressure-resistant bottle.

8. The preparation method of the multifunctional ionic porous organic cage material according to claim 2, characterized in that, in the preparation method of NKPOC-PH(I)Me, the molar ratio of the reactants and the solvent is NKPOC-PH: methyl iodide: reaction solvent = 1: 1.5 to 100: 10000 to 100000, the stirring reaction temperature is 20 to 80 °C, the stirring environment is in an air, nitrogen, or argon atmosphere, and the reaction time is 2 to 120 h.

9. The use of the multifunctional ionic porous organic cage material according to claim 1, characterized in that, it is used for adsorbing dichromate.

10. The use of the multifunctional ionic porous organic cage material according to claim 9, characterized in that, it is used for adsorbing dichromate in an acidic aqueous phase with pH = 3 to 4.

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