A UiO-66-NH2-based porous liquid and its preparation method

Abstract

The application discloses a kind of UiO-66-NH2-based porous liquids and preparation method thereof, belong to porous material technical field.The application is to solve the problem of harsh synthesis condition of porous liquid in prior art, poor long-term stability and pore is easily filled.The technical scheme of the application includes: first synthesizing UiO-66-NH2 metal organic framework material;Then prepare the eutectic solvent consisting of 2,3-epoxypropyl trimethylammonium chloride and polyetheramine D2000;Then UiO-66-NH2 is grafted with the eutectic solvent in ethanol aqueous solution, and the UiO-66-NH2-based porous liquid is obtained after removing the solvent.The porous liquid has both permanent micropores and good flowability, and remains uniform and stable without stratification at room temperature for 150 days.The application is mainly used in the fields of gas adsorption and separation, biomolecular recognition and aptamer screening.

Description

Technical Field

[0001] This invention relates to the field of porous materials technology, and more specifically, to a UiO-66-NH2-based metal-organic framework porous liquid with permanent pores and flowability, and a method for preparing the same. Background Technology

[0002] Porous materials such as zeolites and metal-organic frameworks (MOFs) have significant applications in gas adsorption and separation, catalysis, and other fields due to their high specific surface area and well-ordered pore structure. However, the inherent solid-state nature of these materials limits their application in continuous flow processes and membrane separation scenarios that require fluid media. While traditional liquids possess excellent fluidity, they lack permanent nanoscale pores.

[0003] To overcome the aforementioned shortcomings, the academic community has proposed the concept of porous liquids. In existing technologies, the preparation of porous liquids is mainly divided into three categories: Type I, which consists of hollow molecules in pure liquid form; Type II, which consists of solutions of hollow molecules in volume-repellent solvents; and Type III, which consists of dispersions of porous solids in volume-repellent solvents. For example, Giri et al. reported in *Nature* in 2015 the preparation of Type II porous liquids using porous organic cages (CC3) and crown ether solvents. Sheng Dai's team, on the other hand, prepared Type III porous liquids by grafting long-chain organic molecules onto the surface of hollow silica and dispersing them in ionic liquids.

[0004] However, existing technologies still have shortcomings. For Type I porous liquids, their synthesis is difficult, limited by the design of low-melting-point, low-viscosity cavity molecules. For Type II and Type III porous liquids, the key lies in finding suitable volume-repellent solvents to ensure that the solvent molecule size is larger than the window size of the porous material, thereby preventing pore filling. This greatly limits the range of choices for porous materials and solvents. Furthermore, dispersions prepared by physical mixing methods are prone to stratification after long-term standing, exhibiting poor stability. Therefore, developing a novel porous liquid with simple synthesis, good stability, and the ability to effectively maintain the inherent pore structure of porous materials, along with its preparation method, has significant research and application value. Summary of the Invention

[0005] This invention aims to solve the technical problems of harsh synthesis conditions, limited material selection, and poor long-term stability of porous liquids in the prior art, and provides a novel UiO-66-NH2-based porous liquid and its simple and efficient preparation method. Technical solution

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a UiO-66-NH2-based porous liquid includes the following steps: (1) Synthesis of UiO-66-NH2 metal-organic framework material: Zirconium source and 2-aminoterephthalic acid were dissolved in the first organic solvent, a regulator was added, and UiO-66-NH2 crystals were obtained by solvothermal reaction. (2) Preparation of eutectic solvent: The hydrogen bond acceptor and the hydrogen bond donor are mixed in proportion and dissolved in a second organic solvent to form a eutectic solvent; wherein the hydrogen bond acceptor is 2,3-epoxypropyltrimethylammonium chloride and the hydrogen bond donor is polyetheramine D2000. (3) Synthesis of porous liquid: The UiO-66-NH2 obtained in step (1) is mixed with the eutectic solvent prepared in step (2) in the reaction solvent to carry out the grafting reaction; after the reaction is completed, the solvent is removed to obtain the UiO-66-NH2-based porous liquid.

[0007] Further, in step (1), the zirconium source is zirconium chloride, the first organic solvent is N,N-dimethylformamide, and the regulator is glacial acetic acid. The solvothermal reaction conditions are: reaction temperature 100-140℃, reaction time 18-30 hours. The product after the reaction is washed sequentially with N,N-dimethylformamide and methanol, and then dried.

[0008] Furthermore, in step (2), the mass ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:10 to 1:15. The second organic solvent is a mixture of ethanol and water.

[0009] Furthermore, in step (3), the mass ratio of UiO-66-NH2 to the eutectic solvent is 1:5 to 1:15. The reaction solvent is a mixed solution of ethanol and water. The conditions for the grafting reaction are: reaction temperature 60-100℃, reaction time 6-18 hours.

[0010] Furthermore, in step (3), the solvent removal method is rotary evaporation and drying.

[0011] The UiO-66-NH2-based porous liquid prepared according to any one of the above preparation methods is characterized in that: the porous liquid is a viscous liquid with fluidity at room temperature; the lattice of UiO-66-NH2 inside it expands, and the X-ray diffraction peak shifts to a lower angle by 0.2-0.5° relative to the standard peak of UiO-66-NH2; its surface has a eutectic solvent modification layer with a thickness of 15-30 nm; the water contact angle of the porous liquid is 65-85°, which is significantly lower than the hydrophilicity of UiO-66-NH2 (contact angle 36.5°), exhibiting amphiphilicity; the porous liquid maintains uniform dispersion and fluidity after standing at room temperature for 150 days, without stratification. Beneficial effects

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. A novel Type III porous liquid is provided: This invention is the first to use a eutectic solvent formed by polyetheramine D2000 and 2,3-epoxypropyltrimethylammonium chloride to covalently graft UiO-66-NH2, successfully preparing a novel porous liquid with permanent channels and good flowability, thus enriching the types of porous liquids. 2. Solved the stability problem of porous liquids: By grafting a eutectic solvent, which serves as a steric hindrance solvent, onto the MOF surface through covalent bonding, rather than through simple physical mixing, the resulting porous liquid remains homogeneous and stable after standing at room temperature for 150 days, without stratification or precipitation, which is significantly better than the long-term stability of products obtained by existing physical mixing methods. 3. Ensuring the integrity of the porous matrix: The eutectic solvent molecules selected in this invention have a molecular size larger than the pore size of UiO-66-NH2 (approximately 0.7 nm) and are fixed to the outside of the MOF through a grafting reaction, effectively preventing solvent molecules from entering and clogging the pores. BET testing confirms that the microporous structure of UiO-66-NH2 in the product is preserved, ensuring its core function as a porous material. 4. Simplified synthesis process: This invention uses a one-step grafting reaction to prepare porous liquids, which has a short synthesis path, is easy to operate, and does not require complex multi-step surface modification or harsh solvent removal conditions, making it easy to scale up production. 5. It endows the material with tunable surface properties: By grafting amphiphilic polyetheramine segments, the strongly hydrophilic UiO-66-NH2 was successfully transformed into an amphiphilic material with moderate hydrophobicity (contact angle 73.8°), expanding its application potential in the fields of interface chemistry and biomolecular adsorption. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the synthesis process of the UiO-66-NH2-based porous liquid in Example 1 of this invention.

[0014] Figure 2 The images show the appearance of UiO-66-NH2 powder (a) and the prepared UiO-66-NH2-based porous liquid (b, c, d, f) in Example 1 of this invention, as well as the appearance of the control sample (e).

[0015] Figure 3 The Fourier transform infrared spectra of UiO-66-NH2, the eutectic solvent GTAC-D2000, and the prepared UiO-66-NH2-based porous liquid in Example 1 of this invention are shown.

[0016] Figure 4 The X-ray diffraction patterns of UiO-66-NH2 and the prepared UiO-66-NH2-based porous liquid in Example 1 of this invention are shown.

[0017] Figure 5 Thermogravimetric analysis curves of UiO-66-NH2 and the prepared UiO-66-NH2-based porous liquid in Example 1 of this invention.

[0018] Figure 6 The figure shows the water contact angle measurement results of UiO-66-NH2 (a) and the prepared UiO-66-NH2-based porous liquid (b) in Example 1 of the present invention.

[0019] Figure 7 This is a particle size distribution diagram of UiO-66-NH2 and the prepared UiO-66-NH2-based porous liquid in Example 1 of the present invention.

[0020] Figure 8 The images show the nitrogen adsorption / desorption isotherms (a) and pore size distribution (b) of UiO-66-NH2 in Example 1 of this invention.

[0021] Figure 9 The images show a simulation diagram (a) of the single crystal structure of UiO-66-NH2 in Example 1 of the present invention and simulation diagrams (b, c) of two molecular sizes of the eutectic solvent GTAC-D2000.

[0022] Figure 10 The images shown are scanning electron microscope (SEM) images (a, b, c) and EDS spectra (d) of UiO-66-NH2 in Example 1 of this invention.

[0023] Figure 11 Transmission electron microscopy (TEM) images (a, b, c) of the UiO-66-NH2-based porous liquid prepared in Example 1 of this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below with reference to specific embodiments. However, the scope of protection of this invention is not limited to the following embodiments.

[0025] Example 1 This embodiment provides a method for preparing UiO-66-NH2-based porous liquid (UiO-66-PL), the specific steps of which are as follows: 1. Synthesis of UiO-66-NH2: Weigh 1.1664 g of zirconium chloride and 0.9242 g of 2-aminoterephthalic acid, and dissolve them separately in 42.5 mL of N,N-dimethylformamide (DMF). Dissolve by sonication for 5 minutes. Mix the two solutions, add 15 mL of glacial acetic acid, and continue sonication for 5 minutes. Transfer the mixture to a hydrothermal synthesis reactor and heat in a 120°C electric drying oven for 24 hours. After the reaction, allow it to cool naturally to room temperature. Wash the obtained product three times each with DMF and methanol by centrifugation, and finally dry at 80°C for 12 hours to obtain a pale pink UiO-66-NH2 powder. 2. Preparation of the eutectic solvent (GTAC-D2000): Weigh 9.2609 g of polyetheramine D2000 and 0.7391 g of 2,3-epoxypropyltrimethylammonium chloride, add them to a mixed solvent of 40 mL of ethanol and 40 mL of water, and sonicate for 5 minutes until completely dissolved to obtain a eutectic solvent solution. 3. Synthesis of UiO-66-NH2-based porous liquids: Add 1.0 g of the UiO-66-NH2 powder obtained in step 1 to the eutectic solvent solution prepared in step 2, and sonicate for 5 minutes to disperse it evenly. Transfer the mixture to a heat-collecting constant-temperature magnetic stirrer and heat and stir at 80°C for 12 hours. After the reaction is complete, cool to room temperature, remove most of the solvent using a rotary evaporator, and then dry thoroughly in an 80°C oven for 12 hours to obtain a pink viscous liquid, which is the UiO-66-NH2-based porous liquid of this embodiment.

[0026] Structural characterization and performance testing: The UiO-66-NH2 and UiO-66-PL prepared in Example 1 were characterized in various ways, and the results are as follows: Appearance and stability: The obtained UiO-66-PL is a reddish-brown viscous liquid with good flowability. After standing at room temperature for 150 days, it still maintains good flowability and dispersibility without stratification. In contrast, when ungrafted UiO-66-NH2 was physically mixed with GTAC-D2000 eutectic solvent, obvious stratification occurred after standing for 150 days. Infrared spectrum: The infrared spectrum of UiO-66-PL shows the characteristic peaks of UiO-66-NH2 (the benzene ring skeleton peak at 1580 cm⁻¹ and the fingerprint peak at 800-500 cm⁻¹), while the peak at 1652 cm⁻¹ disappears, indicating that the eutectic solvent was successfully grafted onto the MOF. X-ray diffraction: Compared with the standard card of UiO-66-NH2, the XRD diffraction peak position of UiO-66-PL shifted to a lower angle by about 0.3°, indicating that the grafting reaction caused a slight expansion of the MOF lattice. Thermogravimetric analysis: The decomposition temperature of the UiO-66-PL surface modification layer is higher than the boiling point of polyetheramine D2000 (232℃), indicating that it has good thermal stability. Hydrophilicity / hydrophobicity: Water contact angle test showed that UiO-66-NH2 had a contact angle of 36.5°, indicating strong hydrophilicity; while UiO-66-PL had a contact angle of 73.8°, indicating amphiphilicity. Particle size distribution: Dynamic light scattering analysis showed that the average particle size of UiO-66-PL was 449 nm, which is about 50 nm larger than that of UiO-66-NH2 (396 nm), confirming the presence of the surface modification layer. Specific surface area and pore size: BET test results show that the specific surface area of ​​UiO-66-NH2 is 754.37 m² / g, which is typical of microporous materials, with the pore size concentrated around 0.7 nm. This size is smaller than the molecular size of the sterically hindered solvent GTAC-D2000, ensuring that the pores are not filled. Electron microscopy: Scanning electron microscopy revealed that UiO-66-NH2 exhibits a regular octahedral structure. Transmission electron microscopy clearly observed a eutectic solvent modification layer with a thickness of approximately 22 nm on the surface of the MOF particles of UiO-66-PL. The above characterization results fully demonstrate that this embodiment successfully prepared a UiO-66-NH2-based porous liquid with permanent channels, good flowability, and excellent long-term stability.

[0027] Example 2 This embodiment is basically the same as Embodiment 1, except that the synthesis parameters of UiO-66-NH2 are adjusted. Specifically: In step 1, the solvothermal reaction temperature is 100℃ and the reaction time is 30 hours. The other steps and parameters are the same as in Example 1. Preliminary tests showed that the resulting product had similar flowability and stability to that of Example 1.

[0028] Example 3 This embodiment is basically the same as Embodiment 1, except that the material ratio and conditions of the grafting reaction are adjusted. Specifically: In step 3, the amount of UiO-66-NH2 powder added was 0.7 g, and the amount of eutectic solvent (prepared from 6.48 g of polyetheramine D2000 and 0.52 g of 2,3-epoxypropyltrimethylammonium chloride) was adjusted accordingly to make the mass ratio of the two approximately 1:10. The grafting reaction temperature was 60℃, and the reaction time was 18 hours. The other steps and parameters are the same as in Example 1. Preliminary tests showed that the obtained product had similar flowability and stability to that of Example 1, and a distinct surface modification layer could also be observed under a transmission electron microscope.

[0029] In summary, the present invention provides a UiO-66-NH2-based porous liquid and its preparation method, which has a simple process, excellent product performance, and solves the long-standing problems of poor stability and easy pore blockage in the prior art, and has significant prospects for industrial application.

Claims

1. A method for preparing a UiO-66-NH2-based porous liquid, characterized in that, Includes the following steps: Step 1: Synthesize UiO-66-NH2 metal-organic framework material; Step 2: Prepare a eutectic solvent, which consists of a hydrogen bond acceptor and a hydrogen bond donor. The hydrogen bond acceptor is 2,3-epoxypropyltrimethylammonium chloride, and the hydrogen bond donor is polyetheramine D2000. Step 3: Mix the UiO-66-NH2 obtained in Step 1 with the eutectic solvent prepared in Step 2 in the reaction solvent to carry out the grafting reaction. After the reaction is completed, remove the solvent to obtain the UiO-66-NH2-based porous liquid.

2. The preparation method according to claim 1, characterized in that, The synthesis of UiO-66-NH2 in step one specifically includes: dissolving zirconium source and 2-aminoterephthalic acid in a first organic solvent, adding a regulator, and then washing and drying after a solvothermal reaction.

3. The preparation method according to claim 2, characterized in that, The zirconium source is zirconium chloride, the first organic solvent is N,N-dimethylformamide, and the regulator is glacial acetic acid.

4. The preparation method according to claim 2, characterized in that, The conditions for the solvothermal reaction are: reaction temperature 100-140℃, reaction time 18-30 hours.

5. The preparation method according to claim 1, characterized in that, The mass ratio of hydrogen bond acceptor to hydrogen bond donor in step two is 1:10 to 1:

15.

6. The preparation method according to claim 1, characterized in that, In step three, the mass ratio of UiO-66-NH2 to the eutectic solvent is 1:5 to 1:

15.

7. The preparation method according to claim 1, characterized in that, The reaction solvent in step three is a mixed solution of ethanol and water, and the conditions for the grafting reaction are: reaction temperature 60-100℃, reaction time 6-18 hours.

8. The preparation method according to claim 1, characterized in that, The solvent removal method described in step three is rotary evaporation and drying.

9. The UiO-66-NH2-based porous liquid prepared by the method according to any one of claims 1 to 8, characterized in that, The porous liquid is a viscous liquid with fluidity at room temperature, and its surface has a layer of eutectic solvent modification. The porous liquid still maintains uniform dispersion and fluidity after standing at room temperature for 150 days.

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