A polydimethylsiloxane metal-organic framework coating composite film and a preparation method and application thereof

Abstract

The present application relates to a kind of polydimethylsiloxane metal organic framework coating composite film and its preparation method and application, including the following steps: with metal organic framework as basic filler, polydimethylsiloxane is polymer coating, catalyst and crosslinking agent are added, and polydimethylsiloxane metal organic framework polymer solution is formed after physical mixing;Polydimethylsiloxane metal organic framework polymer solution is modified on the surface of modified porous membrane using covalent bond to achieve grafting purpose, and polydimethylsiloxane metal organic framework coating composite film is obtained.Compared with prior art, the polydimethylsiloxane metal organic framework coating obtained in the present application has a large number of functional amino groups, which can be effectively crosslinked and combined with the modified porous membrane substrate through covalent bond, thereby improving the interface relationship between the coating and the substrate, solving the interface defects of the coating and the substrate, improving the mechanical strength and physicochemical structure of the coating composite film, and the coating process is relatively simple, and the environmental impact is smaller.

Description

Technical Field

[0001] This invention relates to the fields of composite membrane material preparation and organic pollutant adsorption technology, specifically to a polydimethylsiloxane metal-organic framework coated composite membrane, its preparation method, and its application. Background Technology

[0002] The emissions of carbon dioxide and organic pollutants from numerous petrochemical enterprises are increasing year by year. These emissions pose a serious threat to natural ecosystems and human health. Many organic pollutants have been listed as priority pollutants by authoritative organizations such as the World Health Organization, the US Environmental Protection Agency, the European Union, China, and other regulatory agencies. Therefore, prioritizing the treatment of excess organic pollutants can significantly reduce their potential emission into the atmosphere. Commonly used methods for treating organic pollutants include concentration and recovery, photolysis, combustion, microbial methods, and adsorption. Among these, adsorption stands out due to its green, convenient, and inexpensive advantages. Materials used for adsorbing organic pollutants include biomass carbon, metal-organic frameworks, and membranes. Membrane materials, with their unique advantages of low energy consumption and high efficiency, show great potential. Therefore, developing membrane materials with high mechanical strength, good chemical stability, and high adsorption capacity for organic pollutants has become a current research hotspot.

[0003] Coated composite membranes, as novel membrane materials, have attracted widespread attention from scientists. They are made by coating a porous membrane substrate with a functionalized polymer coating. However, coated composite membranes often face the problem of weak adhesion between the functionalized coating and the substrate. Therefore, solving the relationship between the coating and the substrate, enhancing their adhesion, and obtaining coated composite membranes with high adsorption capacity for organic pollutants are key research areas. Metal-organic frameworks (MOFs) have become the preferred target for functionalized polymer coatings due to their regular pore structure, modifiable functional groups, and numerous unsaturated sites. Although MOF-coated composite membranes exhibit good adsorption performance for organic pollutants, the common problem of poor adhesion and mismatch between the coating and the substrate, resulting in weak adsorption, remains. Furthermore, the optimal selection of MOFs in the coating remains a crucial issue to be addressed. Summary of the Invention

[0004] The purpose of this invention is to overcome at least one of the defects of the prior art and provide a polydimethylsiloxane metal-organic framework coated composite membrane, its preparation method and application, which enhances the bonding and functionality between the coating and the substrate, greatly maintains the physical structure and chemical stability of the porous membrane substrate, and thus improves the adsorption performance of the coated composite membrane for organic pollutants.

[0005] Based on the principle of covalent bonding, modifying porous membrane substrates and utilizing metal-organic frameworks (MOFs) can improve the interfacial relationship between the coating and the substrate, and further optimize the adsorption performance of organic pollutants. Currently, there are numerous materials for modifying porous membrane substrates and polymers for coatings, but research on materials with strong chemical interactions with the MOFs in the coating and the resulting coated composite membranes is limited. Furthermore, the adsorption mechanism of organic pollutants in coated composite membranes remains relatively unclear. Therefore, selecting suitable modified porous membrane substrate materials and polymers for coatings to prepare coated composite membranes with good coating-substrate bonding, low cost, and high adsorption capacity is of significant research importance and application value.

[0006] Polydimethylsiloxane, as a polymer material, contains a large number of ether-oxygen bonds, which can promote the interaction between organic pollutant molecules and the coated composite membrane and provide a large number of sites for adsorption and removal of organic pollutants. Furthermore, polydimethylsiloxane has excellent ductility, flexible controllability, and good compatibility with porous membrane substrates, solving the compatibility problem between functionalized coatings and substrates. In addition, after modification with nitrogen-hydroxysuccinimide (NHS) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC), NHS and EDC can form NHS ester intermediates with the substrate, which are then subjected to an amidation reaction to form covalent bonds between the porous membrane substrate and the metal-organic framework in the functionalized coating, thereby enhancing the bonding force between the two. This reaction is mild, the preparation process is simple, and pollution-free. The coated composite membrane prepared by this method not only increases the functionality of the coating but also effectively maintains the physical structure and chemical stability of the porous membrane substrate, thereby improving the performance of the coated composite membrane against organic pollutants. The objective of this invention can be achieved through the following technical solutions:

[0007] One objective of this invention is to provide a method for preparing a polydimethylsiloxane metal-organic framework coated composite film, comprising the following steps:

[0008] A polydimethylsiloxane metal-organic framework polymer solution was formed by physically mixing a metal-organic framework as the basic filler and polydimethylsiloxane as the polymer coating, with the addition of a catalyst and a crosslinking agent.

[0009] A polydimethylsiloxane metal-organic framework polymer solution was coated onto a modified porous membrane. The solvent was evaporated at room temperature, and the polydimethylsiloxane metal-organic framework polymer solution was modified onto the surface of the modified porous membrane by covalent bonds to achieve the grafting purpose, thereby obtaining a polydimethylsiloxane metal-organic framework coated composite membrane.

[0010] Further, the metal-organic framework is a zirconium-based metal-organic framework; the catalyst is dibutyltin dilaurate; and the crosslinking agent is tetraethyl orthosilicate. The mass ratio of the metal-organic framework, polydimethylsiloxane, tetraethyl orthosilicate, and dibutyltin dilaurate is (1-3):(5-10):2:1.

[0011] Furthermore, the polydimethylsiloxane metal-organic framework polymer solution contains n-hexane; the mass ratio of n-hexane to polydimethylsiloxane is (1-2):1.

[0012] Furthermore, the specific process of the physical mixing is as follows: zirconium-based metal-organic framework and polydimethylsiloxane are mixed in hexane and stirred for 2-3 hours, and then tetraethyl orthosilicate and dibutyl dilaurate are added and mixed and stirred for 5-10 minutes.

[0013] Furthermore, the stirring is carried out at room temperature.

[0014] Furthermore, the modified porous membrane is prepared by first immersing the mixed cellulose membrane in a mixed solution of nitrogen-hydroxysuccinimide (NHS) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) for activation, and then drying it to obtain the modified porous membrane.

[0015] Furthermore:

[0016] The mass ratio of the nitrogen-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (1-2):1;

[0017] The mixed solution of nitrogen-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide was prepared with PBS buffer solution at pH 7-8.

[0018] The volume of the PBS buffer solution shall be no less than 10 mL and no more than 100 mL;

[0019] The soaking time is 6-12 hours.

[0020] Furthermore, the coating process specifically involves casting a polydimethylsiloxane metal-organic framework polymer solution onto a modified porous membrane, and using a coating device to form a uniform and smooth membrane.

[0021] The second objective of this invention is to provide a polydimethylsiloxane metal-organic framework coated composite film obtained by the method described above.

[0022] The third objective of this invention is the application of a polydimethylsiloxane metal-organic framework coated composite membrane as described above, which is used for the adsorption of organic pollutants such as petroleum ether, cyclohexane, methanol and ethyl acetate.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1) Currently, coated composite membranes are mainly composed of functionalized coatings and porous membrane substrates. Due to the common problem of mismatch and poor adaptability between functionalized coatings and porous membrane substrates, the prepared coated composite membranes usually exhibit poor mechanical properties and low adhesion. In this invention, the polydimethylsiloxane metal-organic framework coating has a large number of functionalized amino groups, which can effectively crosslink and bond with the modified porous membrane substrate through covalent bonding. This improves the interfacial relationship between the coating and the substrate, solves the interfacial defects between the coating and the substrate, and enhances the mechanical strength and physicochemical structure of the coated composite membrane. The coating process is relatively simple and has little environmental impact.

[0025] 2) This invention utilizes the ease with which polydimethylsiloxane can covalently crosslink with zirconium-based metal-organic frameworks, eliminating the need for initiators and catalysts in the physical mixing process. This simplifies the preparation process, reduces interference from multiple factors, saves costs, and reduces environmental pollution. Furthermore, the physicochemical structure of the coating can be controlled by adjusting the concentration of polydimethylsiloxane, the coating thickness, and the metal-organic framework content, which facilitates its integration with the modified mixed cellulose membrane, reduces the volume of ineffective gaps, and thus significantly improves the adsorption capacity of the mixed matrix membrane.

[0026] 3) The polydimethylsiloxane metal-organic framework coated composite membrane of the present invention exhibits adsorption capacities of no less than 400 mg / g, 500 mg / g, 300 mg / g, and 700 mg / g for four typical organic pollutants: petroleum ether, cyclohexane, methanol, and ethyl acetate, respectively. Compared with similar membrane materials, this coated composite membrane demonstrates excellent adsorption capacity for organic pollutants. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the preparation process of a polydimethylsiloxane metal-organic framework coated composite film according to the present invention.

[0028] Figure 2 This is a scanning electron microscope image of the polydimethylsiloxane metal-organic framework coating composite film in Example 1;

[0029] Figure 3 This is a graph showing the adsorption data of organic pollutants on the polydimethylsiloxane metal-organic framework coated composite membrane in Example 1. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0031] A method for preparing a polydimethylsiloxane metal-organic framework coated composite film includes the following steps:

[0032] A polydimethylsiloxane metal-organic framework polymer solution was formed by physically mixing a metal-organic framework as the basic filler and polydimethylsiloxane as the polymer coating, with the addition of a catalyst and a crosslinking agent.

[0033] The metal-organic framework is a zirconium-based metal-organic framework; the catalyst is dibutyltin dilaurate; the crosslinking agent is tetraethyl orthosilicate; the mass ratio of the metal-organic framework, polydimethylsiloxane, tetraethyl orthosilicate, and dibutyltin dilaurate is (1-3):(5-10):2:1. The specific physical mixing process is as follows: at room temperature, the zirconium-based metal-organic framework and polydimethylsiloxane are mixed in hexane and stirred for 2-3 hours, then tetraethyl orthosilicate and dibutyltin dilaurate are added and mixed and stirred for 5-10 minutes.

[0034] A polydimethylsiloxane metal-organic framework polymer solution was coated onto a modified porous membrane. The solvent was evaporated, and the polydimethylsiloxane metal-organic framework polymer solution was used to modify the surface of the modified porous membrane by covalent bonds to achieve the grafting purpose, thereby obtaining a polydimethylsiloxane metal-organic framework coated composite membrane.

[0035] The polydimethylsiloxane metal-organic framework polymer solution contains n-hexane; the mass ratio of n-hexane to polydimethylsiloxane is (1-2):1. The modified porous membrane is prepared as follows: a mixed cellulose membrane is first activated by immersing it in a mixed solution of nitrogen-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and then dried to obtain the modified porous membrane. The mass ratio of nitrogen-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (1-2):1; the mixed solution of nitrogen-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide is prepared with PBS buffer solution at pH 7-8; the volume of the PBS buffer solution is not less than 10 mL and not more than 100 mL; the immersion time is 6-12 hours. The coating process involves casting a polydimethylsiloxane metal-organic framework polymer solution onto a modified porous membrane and using a coater to form a uniform and smooth membrane.

[0036] In the following examples, the pore size of the mixed cellulose membrane was 0.45 μm, and it was purchased from Millipore.

[0037] Example 1:

[0038] I. This embodiment relates to a method for preparing a polydimethylsiloxane metal-organic framework coated composite film. For details, please refer to [link to specific procedures]. Figure 1 It includes the following steps:

[0039] 1) Preparation of polydimethylsiloxane metal-organic framework polymer solution: 0.15 g UiO-66-NH2 was dissolved in 1 mL n-hexane and sonicated for 1 h and magnetically stirred for 2 h. Then, 0.5 g polydimethylsiloxane was added and stirring was continued for 1 h. Then, 0.1 g TEOS and 0.05 g DBTDL were added and stirred for 10 min. The resulting solution is denoted as polydimethylsiloxane metal-organic framework polymer solution.

[0040] 2) Preparation of polydimethylsiloxane metal-organic framework coated composite membrane: The mixed cellulose membrane was activated for 12 hours in 20 mL of PBS solution (pH 7.4) containing 400 mg EDC and 400 mg NHS, and then dried in an oven at 80 °C. Then, the polydimethylsiloxane metal-organic framework polymer solution was poured onto the modified mixed cellulose membrane and spread evenly using a coater. After evaporation at room temperature, the polydimethylsiloxane metal-organic framework coated composite membrane UiO-66-NA@PDMS / MCE was obtained, which has a dense coating on top and a porous substrate underneath. (See figure) Figure 2 .

[0041] II. The polydimethylsiloxane metal-organic framework coated composite membrane prepared in this embodiment was subjected to an organic pollutant adsorption experiment. The steps are as follows:

[0042] 1) Place 50 mL of each solvent into a 250 mL glass bottle. Then suspend another 20 mL vial containing a weighing membrane inside the glass bottle, ensuring the membrane is only in contact with the vapors of the volatile organic compounds at room temperature. Weigh the vial every four hours. Calculate the adsorption capacity of the polydimethylsiloxane metal-organic framework coated composite membrane using the following formula:

[0043] C = (M1 - M0) / m × 1000 mg / g (1)

[0044] C represents the adsorption capacity, M1 and M0 represent the equilibrium mass and initial mass of the glass vial containing the sample, respectively, and m represents the mass of the membrane.

[0045] Adsorption experiments on organic pollutants were conducted using the method described above. The organic pollutants involved were petroleum ether, cyclohexane, methanol, and ethyl acetate. The adsorption capacities of UiO-66-NA@PDMS / MCE for petroleum ether, cyclohexane, methanol, and ethyl acetate were measured to be 469.8 mg / g, 585.5 mg / g, 397.6 mg / g, and 723.2 mg / g, respectively. (See attached table). Figure 3 And Table 1.

[0046] Example 2:

[0047] The organic pollutant adsorption experiment of the mixed cellulose membrane in this embodiment is the same as that in Example 1. The specific adsorption performance is shown in Table 1.

[0048] Table 1. Comparison of adsorption performance between polydimethylsiloxane metal-organic framework coated composite membranes and mixed cellulose membranes.

[0049]

[0050] The results show that, compared with the mixed cellulose membrane, the polydimethylsiloxane metal-organic framework coated composite membrane prepared in Example 1 has a high adsorption capacity for organic pollutants, indicating that the polydimethylsiloxane metal-organic framework coated composite membrane has excellent adsorption properties.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. The application of a polydimethylsiloxane metal-organic framework coated composite membrane in the adsorption of organic pollutants, characterized in that, The preparation method of the polydimethylsiloxane metal-organic framework coated composite film includes the following steps: A polydimethylsiloxane metal-organic framework polymer solution was formed by physically mixing a metal-organic framework as the basic filler and polydimethylsiloxane as the polymer coating, with the addition of a catalyst and a crosslinking agent. A polydimethylsiloxane metal-organic framework polymer solution was coated onto a modified porous membrane. The solvent was evaporated, and the polydimethylsiloxane metal-organic framework polymer solution was modified onto the surface of the modified porous membrane by covalent bonds to achieve the grafting purpose, thereby obtaining a polydimethylsiloxane metal-organic framework coated composite membrane. The metal-organic framework is a zirconium-based metal-organic framework; the catalyst is dibutyltin dilaurate; and the crosslinking agent is tetraethyl orthosilicate. The mass ratio of the metal-organic framework, polydimethylsiloxane, tetraethyl orthosilicate and dibutyltin dilaurate is (1-3):(5-10):2:1; The modified porous membrane is prepared by first immersing the mixed cellulose membrane in a mixed solution of nitrogen-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide for activation, and then drying it to obtain the modified porous membrane. The organic pollutants are petroleum ether, cyclohexane, methanol, and ethyl acetate.

2. The application according to claim 1, characterized in that, The polydimethylsiloxane metal-organic framework polymer solution contains n-hexane; the mass ratio of n-hexane to polydimethylsiloxane is (1-2):

1.

3. The application according to claim 2, characterized in that, The specific process of physical mixing is as follows: zirconium-based metal-organic framework and polydimethylsiloxane are mixed in hexane and stirred for 2-3 hours, and then tetraethyl orthosilicate and dibutyl dilaurate are added and mixed and stirred for 5-10 minutes.

4. The application according to claim 3, characterized in that, The stirring was carried out at room temperature.

5. The application according to claim 1, characterized in that, The mass ratio of the nitrogen-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (1-2):1; The mixed solution of nitrogen-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide was prepared with PBS buffer solution at pH 7-8. The volume of the PBS buffer solution shall be no less than 10 mL and no more than 100 mL; The soaking time is 6-12 hours.

6. The application according to claim 1, characterized in that, The coating process specifically involves casting a polydimethylsiloxane metal-organic framework polymer solution onto a modified porous membrane, and using a coating device to form a uniform and smooth membrane.

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