Guanidyl functionalized metal organic framework composite material as well as preparation method and application thereof

Abstract

The invention discloses a guanidyl functionalized metal organic framework composite material as well as a preparation method and application thereof, and relates to the technical field of high polymer materials. The method comprises the following steps: carrying out plasma treatment on an MOFs matrix material; adding a guanidyl monomer aqueous solution into the MOFs matrix material subjected to plasma treatment, heating at 60-80 DEG C, continuously stirring for 6-12 hours to react, standing for 6-12 hours, filtering, washing, and freeze-drying at low temperature for 12-24 hours to obtain the guanidyl functionalized metal organic framework composite material. The MOFs matrix material is subjected to induced grafting by adopting a plasma technology, efficient functionalization of guanidyl on the MOFs surface is achieved, the preparation method is simple and environmentally friendly, the reaction condition is mild, and the obtained composite material has high adsorption capacity and high selectivity on gaseous iodine and meanwhile has good stability and reusability.

Description

Technical Field

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

[0002] During the reprocessing of nuclear fuel in nuclear power plants and in accident conditions, radioactive iodine isotopes are released. Among them, I-129 and I-131 are the most harmful radioactive iodine isotopes due to their extremely long half-life and high specific activity. The Three Mile Island, Chernobyl and Fukushima nuclear accidents have shown that the main form of radioactive iodine is gaseous. The main chemical form of gaseous iodine is I 2 , HOI and organic iodine (such as CH 3 I). Therefore, the effective capture of gaseous radioactive iodine plays a vital role in the safe use 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 difficulty in regeneration. It is necessary to develop materials with high adsorption capacity, fast kinetics and regeneration.

[0003] Metal-organic framework MOFs materials are mainly composed of nitrogen and oxygen multidentate organic ligands of aromatic acids or bases, which are hybridized with inorganic metal centers through coordination bonds to form three-dimensional network structure crystals. Compared with traditional materials, MOFs have the following characteristics and advantages: 1) They have highly diverse crystal structures, various ligands and metal ions, and can form MOFs materials with different structures through coordination chemistry and topological geometric coordination; 2) The structural properties are adjustable, and the chemical environment of the pore surface can be adjusted through modification; 3) They have ultra-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 MOFs materials. At the same time, due to the metal components of MOFs materials, they are very useful for NO in treating nuclear reactor exhaust. ｘ The flammability hazard posed by gas is safer than activated carbon.

[0004] During the preparation of MOFs, a large number of active groups on the ligands (such as carboxyl and amine groups) are used to form complexes with the central metal cluster, resulting in a reduction in exposed active groups, which affects the iodine adsorption performance of simple MOFs. Guanidine compounds are considered to be an effective functional group due to their strong affinity for iodine. Through post-synthetic modification strategies, efficient and active guanidine groups are introduced into MOFs. The rich nitrogen-containing groups in guanidine groups can be used to improve the iodine adsorption capacity of MOFs materials. However, how to efficiently graft guanidine groups onto the surface of MOFs without destroying the overall structure of the material is a technical challenge.

[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-NH 2 and the preparation method is as follows: Add UiO-66-NH 2 to an organic solvent, dissolve monocyanamide in water, and drop the monocyanamide aqueous solution into the organic solvent containing UiO-66-NH 2 . Stir for 20 - 24 h, cool down, centrifuge to collect the solid, and dry it with a detergent to obtain. Although this patent document realizes the introduction of guanidine into UiO-66-NH 2 for the removal of Pb, Cu and methylene blue in aqueous solution, the chemical synthesis method is adopted, which 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, and its safety is low. 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 be discharged into water bodies, causing environmental pollution.

[0006] Based on this, the present invention provides a preparation method of 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 that the existing technology uses the chemical synthesis method to prepare guanidine-functionalized MOFs materials, which has high risks of the reagents used, troublesome post-treatment and easy to cause 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 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.

[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 of a guanidine-functionalized metal-organic framework composite material, including the following steps: (1) Perform plasma treatment on the MOFs matrix material; (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, 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.

[0010] Furthermore, the MOFs matrix material is selected from any one of ZIF-8, UiO-66, and PCN-224.

[0011] Furthermore, the guanidine monomer is selected from any one of diaminoguanidine hydrochloride, tetramethylguanidine and guanidine acetate.

[0012] Furthermore, the mass ratio of the MOFs matrix material to the guanidine monomer is 100:(4-10).

[0013] Furthermore, the concentration of the guanidine monomer aqueous solution is 0.4-2.0 g / L.

[0014] Further, the plasma treatment is carried out under a vacuum degree of 10-500 Pa, and the plasma mixed gas is O 2 / N 2 NH 3 / N 2 Any one of .

[0015] Furthermore, the washing is performed by rinsing with deionized water and ethanol.

[0016] The second object of the present invention is to provide a guanidine-functionalized metal-organic framework composite material prepared by the above method.

[0017] The third object of the present invention is to provide an application of a guanidine-functionalized metal-organic framework composite material in gaseous iodine adsorption.

[0018] Furthermore, 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%.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention uses plasma technology to induce grafting of MOFs matrix materials, thereby achieving efficient functionalization of guanidine groups on the surface of MOFs. The operation is simple, environmentally friendly, has mild reaction conditions, does not destroy the properties of the matrix material, and avoids the safety and pollution problems caused by the chemical synthesis method used in the prior art; 2. The guanidine-functionalized MOFs composite material prepared by the present invention has high adsorption capacity and high selectivity for gaseous iodine, and is suitable for nuclear industrial waste gas treatment and radioactive iodine capture; 3. The guanidine-functionalized MOFs composite material prepared by the present invention can be regenerated by desorption at 120-150°C for 3-5 hours after adsorption saturation, the number of cycles is ≥5 times, the adsorption capacity retention rate is >90%, and it has good stability and reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings: Figure 1 This is the SEM morphology of the MOFs material powder Zr-PCN-224 in Example 1; Figure 2 This is a SEM morphology image of the guanidine-functionalized Zr-PCN-224 composite material prepared in Example 1; Figure 3 The following is a comparison of the adsorption curves of iodine by the materials prepared in the embodiment and the comparative example; Figure 4 The adsorption statistics of the guanidine-functionalized Zr-PCN-224 composite material prepared in Example 1 at different cycle times. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in combination with the embodiments and drawings. Obviously, the schematic implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0022] The following is a detailed description of the embodiments of the guanidine-functionalized metal-organic framework composite material and its preparation method and application according to the present invention with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions and repeated descriptions of well-known matters are omitted. This is to avoid the following description from becoming unnecessarily lengthy and facilitate the understanding of those skilled in the art.

[0023] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0024] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0025] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0026] Unless otherwise specified, the terms "include" and "comprising" mentioned in this application may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other substances not listed may also be included or only the listed substances may be included.

[0027] If there is no special explanation, all the steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0028] The present invention provides a method for preparing a guanidine-functionalized metal-organic framework composite material, comprising the following steps: (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.

[0029] The present invention uses plasma technology to induce grafting of MOFs matrix materials, thereby achieving efficient functionalization of guanidine groups on the surface of MOFs. The operation is simple, environmentally friendly, the reaction conditions are mild, and the properties of the matrix materials are not destroyed.

[0030] The guanidine-functionalized MOFs composite material prepared by the present invention has high adsorption capacity and high selectivity for gaseous iodine, and is suitable for nuclear industrial waste gas treatment and radioactive iodine capture; and according to adsorption tests, the composite material can be regenerated by desorption at 120-150° C. for 3-5 hours after adsorption saturation, the number of cycles is ≥5 times, the adsorption capacity retention rate is >90%, and it has good stability and reusability.

[0031] Preferably, the MOFs matrix material is selected from any one of ZIF-8, UiO-66, and PCN-224, and Zr-PCN-224 is more preferred.

[0032] Preferably, the guanidine monomer is selected from any one of diaminoguanidine hydrochloride, tetramethylguanidine and guanidine acetate.

[0033] Preferably, the mass ratio of the MOFs matrix material to the guanidine monomer is 100:(4-10).

[0034] 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 0.5 g / L, 0.7 g / L, 1.0 g / L, 1.2 g / L, 1.5 g / L, 1.8 g / L, or 2.0 g / L.

[0035] Preferably, the plasma treatment is carried out under a vacuum degree of 10-500 Pa, preferably 100-200 Pa, and the plasma mixed gas is O 2 / N 2 NH 3 / N 2 Any one of the mixed gases, O 2、 NH 3 It is an active gas, the discharge is unstable, N 2 The addition of gas improves the stability of plasma discharge, and more optimally, the volume ratio of the mixed gas is 1:2.

[0036] Specifically, in step (1), the MOFs matrix material is subjected to plasma treatment, which includes the following steps: The MOFs matrix material was placed in a vacuum chamber, and the vacuum pump was turned on to exhaust the air. When the vacuum chamber pressure was at a vacuum degree of 10-500 Pa, a plasma mixed gas was introduced into the chamber with a gas flow rate of 30-100 sccm. A radio frequency inductively coupled plasma source (frequency 13.56 MHz) was used, and the discharge power density was 1-20 W / cm 3 , and continue to discharge for 5-30 minutes at a vacuum degree of 10-500 Pa.

[0037] Preferably, the washing is performed by rinsing with deionized water and ethanol.

[0038] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0039] It should be noted that the experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by those skilled in the art through commercial channels.

[0040] Example 1

[0041] This embodiment provides a method for preparing a guanidine-functionalized metal-organic framework composite material, comprising the following steps: (1) 1.0 g MOFs material powder (Zr-PCN-224, SEM as Figure 1 The plasma generator is placed in a vacuum chamber, and the vacuum pump is turned on to exhaust the air. When the pressure in the chamber of the plasma generator reaches a vacuum degree of 100 Pa, a gas in the atmosphere of O is introduced into the chamber. 2 / N 2 The mixed gas (volume ratio 1:2) with a gas flow rate of 70 sccm was used, and a radio frequency inductively coupled plasma source (frequency 13.56 MHz) was used, with a plasma discharge power density of 20 W / cm 3, and discharge continuously for 20 minutes at a vacuum degree of 100 Pa; (2) Stop the discharge, add 80 mL of 1.0 g / L tetramethylguanidine aqueous solution, heat at 70 °C, and stir continuously for 6 hours to react. After standing for 12 hours, filter, rinse with deionized water and ethanol three times, and then freeze-dry for 24 hours. The SEM of the obtained guanidine functionalized Zr-PCN-224 composite material is as follows: Figure 2 shown.

[0042] from Figure 2 It can be seen that the morphology of the material after grafting guanidine groups is similar to Figure 1 There are obvious differences. The particle size becomes larger and stripes can be observed on the surface linking the individual particles, indicating that guanidine groups are grafted onto Zr-PCN-224.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that the mass ratio of MOFs material to tetramethylguanidine monomer is changed to 100:4.

[0045] A method for preparing a guanidine-functionalized metal-organic framework composite material is provided, comprising the following steps: (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 generator reaches a vacuum degree of 100 Pa, introduce oxygen into the chamber. 2 / N 2 The mixed gas (volume ratio 1:2) with a gas flow rate of 70 sccm was used, and a radio frequency inductively coupled plasma source (frequency 13.56 MHz) was used, with a plasma discharge power density of 20 W / cm 3 , and discharge continuously for 20 minutes at a vacuum degree of 100 Pa; (2) Stop the discharge, add 40 mL of 1.0 g / L tetramethylguanidine aqueous solution, heat at 70°C, and stir continuously for 6 hours to react. After standing for 12 hours, filter, rinse with deionized water and ethanol three times, and then freeze-dry for 24 hours. The obtained guanidine-functionalized Zr-PCN-224 composite material was subsequently used for iodine adsorption test.

[0046] Example 3

[0047] 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.

[0048] A method for preparing a guanidine-functionalized metal-organic framework composite material is provided, comprising the following steps: (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 generator reaches a vacuum degree of 100 Pa, introduce oxygen into the chamber. 2 / N 2 The mixed gas (volume ratio 1:2) with a gas flow rate of 70 sccm was used, and a radio frequency inductively coupled plasma source (frequency 13.56 MHz) was used, with a plasma discharge power density of 20 W / cm 3 , and discharge continuously for 20 minutes at a vacuum degree of 100 Pa; (2) Stop the discharge, add 100 mL of 1.0 g / L tetramethylguanidine aqueous solution, heat at 70°C, and stir continuously for 6 hours to react. After standing for 12 hours, filter, rinse with deionized water and ethanol three times, and then freeze-dry for 24 hours. The obtained guanidine-functionalized Zr-PCN-224 composite material was subsequently used for iodine adsorption test.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that the MOFs (Zr-PCN-224) material is not plasma-modified nor mixed with a guanidine monomer solution for grafting, that is, an unmodified MOFs (Zr-PCN-224) material, which is subsequently used for an iodine adsorption test.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that the MOFs (Zr-PCN-224) material is not plasma-modified, but is directly mixed with a guanidine monomer solution for grafting to obtain a composite material, which is subsequently used for an iodine adsorption test.

[0051] Experimental example

[0052] 1. The materials obtained in the above Examples 1-3 and Comparative Examples 1 and 2 were subjected to iodine adsorption experiments respectively, and the experimental methods were as follows: Weigh 20.0 mg of the guanidine-functionalized Zr-PCN-224 composite material of Example 1, the material powder of Comparative Example 1, and Comparative Example 2 respectively and place them in a 40×25 mm weighing bottle, then place them in a sealed container containing 0.8 g of iodine, place them in an oven, and perform an iodine adsorption experiment at 75° C. and 300-500 ppm of iodine vapor. Determine the iodine adsorption curve based on the increased weight obtained each time; The adsorption curves of the five samples obtained in the experiment are as follows: Figure 3 The adsorption data are shown in Table 1.

[0053] Table 1. Adsorption data 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 Directly mixed with guanidine-grafted Zr-PCN-224 material 876 .

[0054] from Figure 3 From the data in Table 1, we can see that: Compared with the unmodified MOFs material in Comparative Example 1, the adsorption capacity of the MOFs material after plasma-induced grafting of guanidine groups in the present invention is greatly improved, and the adsorption capacity can reach 1230 mg / g. Comparative Example 2 adopts a mixed heating method for grafting, and the MOFs material is not plasma-modified. Its adsorption capacity is slightly higher than the adsorption capacity of Zr-PCN-224, indicating that without plasma treatment, the guanidine monomer is difficult to be successfully grafted, and may be adsorbed on Zr-PCN-224 in small amounts without being eluted, so that the adsorption capacity is higher than that of the unmodified MOFs material; Example 2, due to the low grafting amount of guanidine monomers on MOFs, its adsorption amount of 1029 mg / g is lower than that of Example 1. Compared with Example 1, Example 3 increases the tetramethylguanidine aqueous solution to 100 mL, but the grafting amount of guanidine monomers on MOFs has reached saturation, and the adsorption amount has not been significantly further increased, so the preferred mass ratio is 100:8.

[0055] 2. The saturated guanidine-functionalized Zr-PCN-224 composite material of Example 1 was subjected to regeneration and stability experiments. The experimental method was as follows: the sample was heated at 140°C, and its adsorption capacity was tested again after thermal desorption for 4 hours. The operation was repeated 5 times.

[0056] The experimental results are as follows Figure 4 As shown, from Figure 4 It can be seen that when the number of cycles is 5, the adsorption capacity of the guanidine-functionalized Zr-PCN-224 composite material of the present invention is 1108 mg / g, and the adsorption capacity retention rate is greater than 90%, which has good stability and reusability.

[0057] Finally, it should be noted that the above specific embodiments are only used to explain in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and is not used to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above specific embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions recorded in the above embodiments, or to replace or improve some or all of the technical features therein. 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 included in the scope of the claims and 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%.

Images