Guanidine-functionalized metal-organic framework composite material, preparation method thereof and application

Abstract

The present invention discloses a guanidine-functionalized metal-organic framework composite material, its preparation method and application, which relates to the technical field of polymer materials; the present invention comprises the following steps: performing plasma treatment on the MOFs matrix material; adding an aqueous solution of guanidine monomer to the plasma-treated MOFs matrix material, heating at 60-80 °C, continuously stirring for 6-12 hours for reaction, filtering after standing for 6-12 hours, washing, and freeze-drying at low temperature for 12-24 hours to obtain the guanidine-functionalized metal-organic framework composite material; by using plasma technology to induce grafting on the MOFs matrix material, the present invention realizes the efficient functionalization of guanidine on the surface of MOFs. The preparation method is simple, environmentally friendly, and the reaction conditions are mild. The obtained composite material has a high adsorption capacity and high selectivity for gaseous iodine, and at the same time has good stability and reusability.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a guanidyl-functionalized metal-organic framework composite material, a preparation method thereof, and an application thereof. Background Art

[0002] During the nuclear fuel reprocessing process and accident conditions in nuclear power plants, radioactive iodine isotopes will be released. Among them, I-129 and I-131 are the most harmful radioactive iodine isotopes due to their extremely long half-lives and relatively high specific activities. The occurred Three Mile Island, Chernobyl, and Fukushima nuclear accidents have shown that the main form of radioactive iodine is gaseous. And the main chemical forms of gaseous iodine are I2, HOI, and organic iodine (such as CH3I). Therefore, the effective capture of gaseous radioactive iodine plays a crucial role in the safe utilization of nuclear energy and environmental protection. However, traditional adsorbents (activated carbon, silver zeolite) have problems such as high cost (silver-based), low adsorption capacity, lack of selectivity, and difficult regeneration, and it is necessary to develop materials with high adsorption capacity, fast kinetics, and renewable properties.

[0003] Metal-organic framework (MOF) materials are mainly composed of nitrogen- and oxygen-containing polydentate organic ligands of aromatic acids or bases, which form a three-dimensional network structure crystal through coordination bonds with inorganic metal centers. Compared with traditional materials, MOFs have the following characteristics and advantages: MOFs have the following characteristics and advantages: 1) They have a highly diverse crystal structure, with diverse ligands and metal ions, and different structural MOF materials can be formed through coordination chemistry and topological geometric coordination; 2) The adjustability of structural properties, and the chemical environment of the pore surface can be adjusted through modification; 3) They have an extremely large specific surface area and porosity; 4) They have good thermal stability, chemical stability, and radiation stability; 5) Functional doping and modification expand the application of MOF materials. At the same time, due to the presence of metal components in MOF materials, they have higher safety than activated carbon in dealing with the flammable danger brought by NO ｘ gas.

[0004] During the preparation of MOFs, a large number of active groups (such as carboxyl groups and amine groups) on the ligands are used to form complexes with the central metal clusters, resulting in a reduction in the exposed active groups, which affects the iodine adsorption performance of pure MOFs. Guanidyl compounds are considered to be an effective functional group due to their strong affinity for iodine. Through a post-synthesis modification strategy, highly efficient active guanidyl groups are introduced into MOFs. By using the fact that guanidyl contains rich nitrogen-containing groups, the iodine adsorption capacity of MOF materials can be improved. However, how to efficiently graft guanidyl groups onto the surface of MOFs without destroying the overall structure of the material is a technical problem.

[0005] The patent document with the publication number CN118807712A discloses a guanidine-functionalized UiO-66 material, its preparation method and application. The material is obtained by modifying UiO-66-NH2 with guanidine. The preparation method is as follows: Add UiO-66-NH2 to an organic solvent, dissolve monocyanamide in water, drop the monocyanamide aqueous solution into the organic solvent containing UiO-66-NH2, stir for 20 - 24 hours, cool down, centrifuge to collect the solid, and dry it with a detergent to obtain it. Although this patent document realizes the introduction of guanidine into UiO-66-NH2 for the removal of Pb, Cu, and methylene blue in aqueous solution, it uses a chemical synthesis method that requires the use of toxic chemical reagents such as methyl ethyl ketone and cyanamide. Among them, methyl ethyl ketone has a low flash point and flammability, with low safety. Cyanamide is toxic to the human body and can enter the human body through inhalation, ingestion, and skin absorption, causing poisoning symptoms. The use of these chemical reagents not only has high risks, but also has troublesome post-treatment and is easy to discharge into water bodies, causing environmental pollution.

[0006] Based on this, the present invention provides a preparation method for a guanidine-functionalized metal-organic framework composite material that is simpler, more efficient, and has a high safety factor, and is applied to gaseous iodine adsorption. Summary of the Invention

[0007] The present invention aims to solve the technical problems in the prior art that the chemical synthesis method for preparing guanidine-functionalized MOFs materials has high risks of the reagents used, troublesome post-treatment, and easy environmental pollution. The purpose is to provide a guanidine-functionalized metal-organic framework composite material, its preparation method and application, which realize the efficient functionalization of guanidine on the surface of MOFs. The preparation method is simple, environmentally friendly, and has mild reaction conditions. The obtained composite material has a high adsorption capacity and high selectivity for gaseous iodine, and at the same time has good stability and reusability.

[0008] The present invention is realized through the following technical solutions.

[0009] The first object of the present invention is to provide a preparation method for a guanidine-functionalized metal-organic framework composite material, including the following steps:

[0010] (1) Perform plasma treatment on the MOFs matrix material;

[0011] (2) Add an aqueous solution of guanidine monomer to the plasma-treated MOFs matrix material, heat at 60 - 80 °C, continuously stir for 6 - 12 hours for reaction, let it stand for 6 - 12 hours, then filter, wash, and freeze-dry at low temperature for 12 - 24 hours to obtain the guanidine-functionalized metal-organic framework composite material.

[0012] Further, the MOFs matrix material is selected from any one of ZIF-8, UiO-66, and PCN-224.

[0013] Further, the guanidine monomer is selected from any one of diaminoguanidine hydrochloride, tetramethylguanidine, and guanidine acetate.

[0014] Further, the mass ratio of the MOFs matrix material to the guanidine monomer is 100:(4 - 10).

[0015] Further, the concentration of the aqueous solution of the guanidine monomer is 0.4 - 2.0 g / L.

[0016] Further, the plasma treatment is carried out under a vacuum degree of 10 - 500 Pa, and the plasma mixed gas is any one of O2 / N2 and NH3 / N2.

[0017] Further, the washing is carried out by rinsing with deionized water and ethanol.

[0018] The second object of the present invention is to provide a guanidine-functionalized metal-organic framework composite material prepared by the aforementioned method.

[0019] The third object of the present invention is to provide an application of the guanidine-functionalized metal-organic framework composite material in the adsorption of gaseous iodine.

[0020] Further, after the guanidine-functionalized metal-organic framework composite material adsorbs iodine to saturation, it can be regenerated by desorbing at 120 - 150 °C for 3 - 5 hours, the number of recycling uses ≥ 5 times, and the adsorption capacity retention rate > 90%.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] 1. By using plasma technology to induce grafting on the MOFs matrix material, the present invention realizes the efficient functionalization of guanidine on the surface of MOFs, with simple operation, environmental protection, mild reaction conditions, and no damage to the properties of the matrix material, avoiding the safety and pollution problems brought by the use of chemical synthesis methods in the prior art; 2. The guanidine-functionalized MOFs composite material prepared by the present invention has a high adsorption capacity and high selectivity for gaseous iodine, and is suitable for the treatment of nuclear industry waste gas and the capture of radioactive iodine; 3. The guanidine-functionalized MOFs composite material prepared by the present invention can be regenerated by desorbing at 120 - 150 °C for 3 - 5 hours after adsorption saturation, the number of recycling uses ≥ 5 times, and the adsorption capacity retention rate > 90%, having good stability and reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on these drawings. In the drawings:

[0024] Figure 1 It is the SEM morphology diagram of the MOFs material powder Zr-PCN-224 in Example 1;

[0025] Figure 2 It is the SEM morphology diagram of the guanidine-functionalized Zr-PCN-224 composite material prepared in Example 1;

[0026] Figure 3 It is the comparison diagram of the iodine adsorption curves of the materials prepared in the examples and comparative examples;

[0027] Figure 4 It is the statistics of the adsorption amounts of the guanidine-functionalized Zr-PCN-224 composite material prepared in Example 1 under different cycle numbers. Detailed implementation manners

[0028] To make the purpose, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments and drawings. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not serve as a limitation to the present invention.

[0029] The following will appropriately refer to the drawings to detail the implementation manners of a guanidine-functionalized metal-organic framework composite material and its preparation method and application of the present invention. However, there will be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions are omitted. This is to avoid the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art.

[0030] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range.

[0031] If there is no special description, all the embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0032] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0033] Unless otherwise specified, the terms "including" and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For example, the terms "including" and "comprising" can mean that other substances not listed can also be included or comprised, or only the substances listed are included or comprised.

[0034] Unless otherwise specified, all steps of this application can be carried out in sequence or randomly, and preferably in sequence.

[0035] The present invention provides a method for preparing a guanidine-functionalized metal-organic framework composite material, comprising the following steps:

[0036] (1) Subjecting the MOFs matrix material to plasma treatment;

[0037] (2) Adding an aqueous solution of a guanidine monomer to the plasma-treated MOFs matrix material, heating at 60 - 80 °C, continuously stirring for 6 - 12 hours for reaction, standing for 6 - 12 hours, then filtering, washing, and freeze-drying at low temperature for 12 - 24 hours to obtain the guanidine-functionalized metal-organic framework composite material.

[0038] The present invention realizes the efficient functionalization of guanidine on the surface of MOFs by inducing grafting on the MOFs matrix material using plasma technology, with simple operation, environmental protection, mild reaction conditions, and without damaging the properties of the matrix material.

[0039] The guanidine-functionalized MOFs composite material prepared by the present invention has a high adsorption capacity and high selectivity for gaseous iodine, and is suitable for the treatment of nuclear industry waste gas and the capture of radioactive iodine; and through adsorption test verification, the composite material can be regenerated by desorbing at 120 - 150 °C for 3 - 5 hours after adsorption saturation, the number of recycling times ≥ 5 times, and the adsorption capacity retention rate > 90%, having good stability and reusability.

[0040] Preferably, the MOFs matrix material is selected from any one of ZIF-8, UiO-66, and PCN-224, and more preferably Zr-PCN-224 is used.

[0041] Preferably, the guanidine monomer is selected from any one of diaminoguanidine hydrochloride, tetramethylguanidine, and guanidine acetate.

[0042] Preferably, the mass ratio of the MOFs matrix material to the guanidine monomer is 100: (4 - 10).

[0043] Preferably, the concentration of the guanidine monomer aqueous solution is 0.5-2.0 g / L. Specifically, the concentration of the guanidine monomer aqueous solution can be selected as 0.5 g / L, 0.7 g / L, 1.0 g / L, 1.2 g / L, 1.5 g / L, 1.8 g / L, 2.0 g / L.

[0044] Preferably, the plasma treatment is carried out under a vacuum of 10-500 Pa, preferably 100-200 Pa. The plasma mixed gas is any one of O2 / N2 and NH3 / N2 mixed gases. O 2、 NH3 is a reactive gas and the discharge is unstable. The addition of N2 gas improves the plasma discharge stability. More preferably, the volume ratio of the mixed gas is 1:2.

[0045] Specifically, in step (1), the plasma treatment of the MOFs matrix material includes the following:

[0046] Place the MOFs matrix material in a vacuum chamber, turn on the vacuum pump, and evacuate the air. When the pressure in the vacuum chamber is under a vacuum of 10-500 Pa, then introduce the plasma mixed gas into the chamber, with a gas flow rate of 30-100 sccm. Use a radio frequency inductively coupled plasma source (frequency 13.56 MHz), and the discharge power density is 1-20 W / cm 3 , and continuously discharge for 5-30 minutes under a vacuum of 10-500 Pa.

[0047] Preferably, the washing is carried out by rinsing with deionized water and ethanol.

[0048] The technical solution of the present invention will be further described in detail below in conjunction with the embodiments.

[0049] It should be noted that the experimental methods used in the embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and those skilled in the art can obtain them through commercial channels without special instructions.

[0050] Example 1

[0051] This example provides a preparation method of a guanidine-functionalized metal-organic framework composite material, including the following steps:

[0052] (1) 1.0 g of MOFs material powder (Zr-PCN-224, SEM as Figure 1Place it (as shown) in a vacuum chamber, turn on the vacuum pump to evacuate air; when the chamber pressure of the plasma generating device reaches a vacuum of 100 Pa, introduce an O2 / N2 mixed gas (volume ratio 1:2) into the chamber with a gas flow rate of 70 sccm. Use a radio frequency inductively coupled plasma source (frequency 13.56 MHz), and the plasma discharge power density is 20 W / cm 3 , and continuously discharge for 20 minutes at a vacuum of 100 Pa;

[0053] (2) Stop the discharge, add 80 mL of 1.0 g / L aqueous solution of tetramethylguanidine, heat at 70 °C, and continuously stir for 6 hours for reaction. Let it stand for 12 hours and then filter. Rinse with deionized water and ethanol 3 times, and then freeze-dry at low temperature for 24 hours. The SEM of the guanidine-functionalized Zr-PCN-224 composite material obtained is as Figure 2 shown.

[0054] From Figure 2 it can be seen that the morphology of the material after grafting guanidine groups is significantly different from Figure 1 that before. The particle size becomes larger, and strip-like substances can be observed on the surface connecting individual particles, indicating that guanidine groups are grafted onto Zr-PCN-224.

[0055] Example 2

[0056] The difference between this example and Example 1 is that the mass ratio of the MOFs material to the tetramethylguanidine monomer is changed to 100:4.

[0057] Provide a preparation method of a guanidine-functionalized metal-organic framework composite material, including the following steps:

[0058] (1) Place 1.0 g of MOFs material powder (Zr-PCN-224) in a vacuum chamber, turn on the vacuum pump to evacuate air; when the chamber pressure of the plasma generating device reaches a vacuum of 100 Pa, introduce an O2 / N2 mixed gas (volume ratio 1:2) into the chamber with a gas flow rate of 70 sccm. Use a radio frequency inductively coupled plasma source (frequency 13.56 MHz), and the plasma discharge power density is 20 W / cm 3 , and continuously discharge for 20 minutes at a vacuum of 100 Pa;

[0059] (2) Stop the discharge, add 40 mL of 1.0 g / L aqueous solution of tetramethylguanidine, heat at 70 °C, and continuously stir for 6 hours for reaction. Let it stand for 12 hours and then filter. Rinse with deionized water and ethanol 3 times, and then freeze-dry at low temperature for 24 hours to obtain the guanidine-functionalized Zr-PCN-224 composite material, and then use this material for iodine adsorption tests.

[0060] Example 3

[0061] The difference between this embodiment and Embodiment 1 is that the mass ratio of the MOFs material to the tetramethylguanidine monomer is changed to 100:10.

[0062] Provide a preparation method of a guanidine-functionalized metal-organic framework composite material, including the following steps:

[0063] (1) Place 1.0 g of MOFs material powder (Zr-PCN-224) in a vacuum chamber, turn on the vacuum pump, and evacuate the air; when the chamber pressure of the plasma generating device reaches a vacuum of 100 Pa, introduce an O2 / N2 mixed gas (volume ratio 1:2) into the chamber, the gas flow rate is 70 sccm, use a radio frequency inductively coupled plasma source (frequency 13.56 MHz), and the plasma discharge power density is 20 W / cm 3 , and continuously discharge at a vacuum of 100 Pa for 20 minutes;

[0064] (2) Stop discharging, drop 100 mL of 1.0 g / L tetramethylguanidine aqueous solution, heat at 70 °C, and continuously stir for 6 hours for reaction. After standing for 12 hours, filter, then rinse 3 times with deionized water and ethanol, and then freeze-dry at low temperature for 24 hours to obtain the guanidine-functionalized Zr-PCN-224 composite material. Subsequently, use this material for iodine adsorption experiments.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Embodiment 1 is that the MOFs (Zr-PCN-224) material is not subjected to plasma modification and is not mixed with the guanidine monomer solution for grafting, that is, the unmodified MOFs (Zr-PCN-224) material. Subsequently, use this material for iodine adsorption experiments.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Embodiment 1 is that the MOFs (Zr-PCN-224) material is not subjected to plasma modification and is directly mixed with the guanidine monomer solution for grafting to obtain a composite material. Subsequently, use this material for iodine adsorption experiments.

[0069] Experimental Example

[0070] 1. Conduct iodine adsorption experiments on the materials obtained in the above Embodiments 1-3, Comparative Examples 1 and 2 respectively. The experimental method is as follows:

[0071] Weigh 20.0 mg of the guanidine-functionalized Zr-PCN-224 composite material of Example 1, and the material powders of Comparative Example 1 and Comparative Example 2 respectively, place them in a weighing bottle of 40×25 mm, then put them into a sealed container containing 0.8 g of iodine, seal it, and put it into an oven. Under the conditions of 75 °C and 300 - 500 ppm iodine vapor, perform an iodine adsorption experiment, and measure the iodine adsorption curve according to the increased weight measured each time;

[0072] The adsorption curves of the 5 samples obtained from the experiment are as Figure 3 shown, and the adsorption capacity data are shown in Table 1.

[0073] Table 1. Adsorption capacity data

[0074] Serial number Experimental materials Adsorption capacity (mg / g) Example 1 Guanidine-functionalized Zr-PCN-224 composite material (mass ratio 100:8) 1230 Example 2 Guanidine-functionalized Zr-PCN-224 composite material (mass ratio 100:4) 1029 Example 3 Guanidine-functionalized Zr-PCN-224 composite material (mass ratio 100:10) 1231 Comparative example 1 Unmodified Zr-PCN-224 material 820 Comparative example 2 Zr-PCN-224 material directly mixed and grafted with guanidine 876 .

[0075] From Figure 3 and the data in Table 1, it can be seen that:

[0076] Compared with the unmodified MOFs material of Comparative Example 1, the adsorption capacity of the MOFs material after plasma-induced grafting of guanidine in the present invention is greatly improved, and the adsorption capacity can reach 1230 mg / g. In Comparative Example 2, the mixed heating method was used for grafting, and the MOFs material was not plasma-modified. Its adsorption amount is slightly higher than the adsorption capacity of Zr-PCN-224, indicating that without plasma treatment, it is difficult for guanidine monomers to be successfully grafted, and maybe a small amount is adsorbed on Zr-PCN-224 and not eluted, so the adsorption amount is higher compared with the unmodified MOFs material; in Example 2, due to the low grafting amount of guanidine monomers on the MOFs, its adsorption amount of 1029 mg / g is lower than that of Example 1. In Example 3, compared with Example 1, the aqueous solution of tetramethylguanidine was increased to 100 mL, but the grafting amount of guanidine monomers on the MOFs has reached saturation, and the adsorption amount has not been significantly further improved, so the preferred mass ratio is 100:8.

[0077] 2. Perform regeneration and stability experiments on the adsorbed-saturated guanidine-functionalized Zr-PCN-224 composite material of Example 1. The experimental method is: heat the sample at a temperature of 140 °C, thermally desorb for 4 hours, and then detect its adsorption capacity again, and repeat the operation 5 times.

[0078] The experimental results are as Figure 4 shown. From Figure 4 it can be seen that when the number of recycling times is 5 times, the adsorption amount of the guanidine-functionalized Zr-PCN-224 composite material of the present invention is 1108 mg / g, and the adsorption amount retention rate > 90%, showing good stability and reusability.

[0079] Finally, it should be noted that: The above specific embodiments are only used to elaborate in detail the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above description is only the specific implementation manners of the present invention and is not used to limit the protection scope of the present invention; Although the present invention has been described in detail with reference to the foregoing specific embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements or improvements on some or all of the technical features; And these modifications, equivalent replacements and improvements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and the description of the present invention.

Claims

1. A method for preparing a guanidine-functionalized metal-organic framework composite material, characterized in that: The following steps are involved: (1) Plasma treatment of MOFs matrix material; (2) Adding a guanidine monomer aqueous solution to the MOFs matrix material after plasma treatment, heating at 60-80°C, stirring continuously for 6-12 hours to react, leaving it to stand for 6-12 hours, filtering, washing, and freeze-drying at low temperature for 12-24 hours to obtain a guanidine functionalized metal organic framework composite material.

2. The method for preparing a guanidine-functionalized metal-organic framework composite material according to claim 1, characterized in that: The MOFs matrix material is selected from any one of ZIF-8, UiO-66, and PCN-224.

3. The method for preparing a guanidine-functionalized metal-organic framework composite material according to claim 1, characterized in that: The guanidine monomer is selected from any one of diaminoguanidine hydrochloride, tetramethylguanidine and guanidine acetate.

4. The method for preparing a guanidine-functionalized metal-organic framework composite material according to claim 1, characterized in that: The mass ratio of the MOFs matrix material to the guanidine monomer is 100:(4-10).

5. The method for preparing a guanidine-functionalized metal-organic framework composite material according to claim 1, characterized in that: The concentration of the guanidine monomer aqueous solution is 0.5-2.0 g / L.

6. A method for preparing a guanidine-functionalized metal-organic framework composite material according to any one of claims 1 to 5, characterized in that: The plasma treatment is carried out under a vacuum degree of 10-500 Pa, and the plasma mixed gas is any one of O2 / N2 and NH3 / N2.

7. A method for preparing a guanidine-functionalized metal-organic framework composite material according to any one of claims 1 to 5, characterized in that: The washing is performed by rinsing with deionized water and ethanol.

8. A guanidine-functionalized metal-organic framework composite material prepared by the method according to any one of claims 1 to 7.

9. Use of a guanidine-functionalized metal-organic framework composite material as claimed in claim 8 in gaseous iodine adsorption.

10. The use according to claim 9, characterized in that: After the guanidine-functionalized metal-organic framework composite material adsorbs iodine to saturation, it can be regenerated by desorption at 120-150° C. for 3-5 hours, and the number of cycles is ≥5 times, and the adsorption capacity retention rate is >90%.

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