UiO-66-based porous liquid and preparation method and application thereof

Abstract

The application discloses a kind of UiO-66-based porous liquids and its preparation method and application, belong to porous material technical field, the present application metal organic framework material UiO-66 or / and metal organic framework material UiO-66-NH2 is porous guest, with ionic liquid [C4C7Im]Br, [C4C4Im]Br is prepared as steric solvent porous liquid.Porous guest can be stably dispersed in steric solvent, benefit from appropriate electrostatic repulsion, based on DLVO colloidal stability theory inference, the electrostatic repulsion of ionic liquid can offset the van der waals attraction between nanoparticles, greatly improve the dispersion stability of porous guest in ionic liquid, form stable porous liquid.

Description

Technical Field

[0001] This invention relates to the field of porous materials technology, specifically to a UiO-66-based porous liquid, its preparation method, and its application. Background Technology

[0002] In recent years, global carbon emissions have increased rapidly, causing atmospheric CO2 levels to reach record highs, leading to frequent catastrophic weather events and seriously threatening human survival and development. Carbon dioxide, as an important carbon resource, can also be used to prepare many chemical raw materials. The cycloaddition reaction of carbon dioxide with epoxides can convert the greenhouse gas CO2 into valuable chemical products such as cyclic carbonates. Therefore, the development of highly efficient and selective catalytic materials for this reaction has always been a hot topic in materials and catalysis research.

[0003] UiO-66 (University of Oslo, UiO) is a metal-organic framework (MOF) with high stability and large open pores, and has been widely studied as a catalytic material in the field of catalysis. However, for Lewis acid-base catalyzed CO2 cycloaddition reactions, UiO-66 usually requires relatively harsh reaction conditions, or the presence of ionic liquid co-catalysts or solvents, to exhibit a certain catalytic effect. By introducing functional groups, functionalizing with ionic liquids, creating defects, and combining with other materials, the acid and base site content of the UiO-66 framework can be increased, thereby effectively improving the catalytic performance of the material for CO2 cycloaddition reactions.

[0004] Ionic liquids (ILs) are among the most promising solvents for constructing porous liquids (PLs) due to their unique advantages such as high absorption efficiency, wide applicability, easily adjustable physical properties, non-volatility, strong stability, easy availability, high economy, and low regeneration energy consumption. However, they also have disadvantages such as high processing costs, high energy consumption, and poor selectivity.

[0005] Porous ionic liquids have been successfully prepared by mixing metal-organic framework materials with ionic liquids to form stable suspensions. However, existing porous liquid preparation processes are complex and can only be used for CO2 adsorption and storage, and the captured CO2 cannot be converted and applied. Summary of the Invention

[0006] This invention provides a UiO-66-based porous liquid, its preparation method, and its application. It effectively solves the technical problem that existing porous liquid preparation processes are complex and can only achieve CO2 adsorption and storage, but cannot convert and apply the captured CO2. This invention uses the metal-organic framework material UiO-66 or / and amino-modified metal-organic framework material UiO-66 as the porous guest, and two ionic liquids, [C4C7Im]Br and [C4C4Im]Br, as sterically hindered solvents to prepare a UiO-66-based porous liquid with high catalytic activity and high stability.

[0007] The first objective of this invention is to provide a UiO-66-based porous liquid, which uses the metal-organic framework material UiO-66 or / and the metal-organic framework material UiO-66-NH2 as a porous guest and the ionic liquids [C4C7Im]Br and [C4C4Im]Br as sterically hindered solvents; wherein the ionic liquids are [C4C7Im]Br and / or [C4C4Im]Br, wherein Im is an imidazole group;

[0008] The mass percentage of the metal-organic framework material UiO-66 or / and the amino-modified metal-organic framework material UiO-66 is 1% to 3%, and the mass percentage of the ionic liquid is 97% to 99%, totaling 100%.

[0009] A second objective of this invention is to provide a method for preparing the above-mentioned UiO-66-based porous liquid, comprising the following steps:

[0010] Preparation of metal-organic framework material UiO-66 or / and amino-modified metal-organic framework material UiO-66;

[0011] Preparation of ionic liquid: Ethyl acetate and N-n-butylimidazolium are mixed to obtain a first reaction solution; ethyl acetate is mixed with a bromoalkane compound to obtain a second reaction solution; the first reaction solution and the second reaction solution are mixed and stirred at 55℃~65℃ to remove ethyl acetate and obtain an ionic liquid;

[0012] The ethanol suspension of the metal-organic framework material UiO-66 and / or the ethanol suspension of the amino-modified metal-organic framework material UiO-66 are mixed with the ethanol suspension of the ionic liquid, stirred at room temperature, and dried to obtain a UiO-66-based porous liquid.

[0013] In a preferred embodiment, the bromoalkane compound is 1-bromoheptane or bromobutane.

[0014] In a preferred embodiment, the molar ratio of the N-n-butylimidazole to the bromine atoms in the bromoalkane compound is 1:1.

[0015] In a preferred embodiment, the mass ratio of the metal-organic framework material UiO-66 or / and the amino-modified metal-organic framework material UiO-66 to the ionic liquid is 0.1:8 to 12.

[0016] In a preferred embodiment, the stirring reaction time is 18–24 hours.

[0017] In a preferred embodiment, the stirring time at room temperature is 18–24 hours.

[0018] A third objective of this invention is to provide an application of the above-mentioned UiO-66-based porous liquid in the catalytic conversion of CO2 into cyclic carbonates.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention provides a UiO-66-based porous liquid, using the metal-organic framework material UiO-66 or / and the metal-organic framework material UiO-66-NH2 as the porous guest, and the ionic liquids [C4C7Im]Br and [C4C4Im]Br as the sterically hindered solvent. The porous guest can be stably dispersed in the sterically hindered solvent due to appropriate electrostatic repulsion. Based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) colloidal stability theory, it is inferred that the electrostatic repulsion of the ionic liquid can counteract the van der Waals attraction between nanoparticles, greatly improving the dispersion stability of the porous guest in the ionic liquid, thus forming a stable porous liquid. The UiO-66-based porous liquid prepared by this invention is used to catalyze the conversion of CO2 into cyclic carbonates. It not only adsorbs and stores CO2, but also converts the captured CO2 into cyclic carbonates. When the UiO-66-based porous liquid prepared in Examples 1 to 4 of this invention is used as a catalyst, the conversion rate of propylene oxide can reach 78.90%. However, when the sterically hindered solvent [C4C7Im]Br or [C4C4Im]Br is used as a catalyst, the conversion rate is much lower than that of the UiO-66-based porous liquid prepared by this invention. Attached Figure Description

[0021] Figure 1 These are electron microscope images of the porous guest UiO-66 and UiO-66-NH2 of the present invention, wherein (a) is magnified 10,000 times; (b) is magnified 20,000 times; (c) is magnified 10,000 times; and (d) is magnified 40,000 times.

[0022] Figure 2 The XRD diffraction patterns of UiO-66 and UiO-66-NH2 of this invention are shown.

[0023] Figure 3 The TGA curves of UiO-66 and UiO-66-NH2 of this invention are shown.

[0024] Figure 4 The images show the FT-IR spectra of the porous guests UiO-66 and UiO-66-NH2 of this invention.

[0025] Figure 5 This is a sample image of the porous guest material of the present invention.

[0026] Figure 6 The image shows the FT-IR spectra of [C4C7Im]Br and [C4C4Im]Br of this invention.

[0027] Figure 7 The images show the FT-IR spectra of the UiO-66-based porous liquids of the present invention, wherein (a) shows Br-UiO-PL-1 and Br-UiO-NH2-PL-1, and (b) shows Br-UiO-PL-2 and Br-UiO-NH2-PL-2.

[0028] Figure 8 The images shown are photographs and TEM images of the samples Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2 and Br-UiO-NH2-PL-2 of the present invention. Among them, Figure a is a photograph of the samples Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2 and Br-UiO-NH2-PL-2, and Figures b to d are TEM images of the porous liquids.

[0029] Figure 9 The thermogravimetric curves of Br-UiO-PL and Br-UiO-NH2-PL of the present invention are shown in Figure (a), (b), and (c).

[0030] Figure 10 The figures show the CO2 adsorption curves of [C4C7Im]Br, [C4C4Im]Br, and the porous liquids Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2 and Br-UiO-NH2-PL-2 prepared in the examples of the present invention. In Figure (a), the figures show [C4C7Im]Br, Br-UiO-PL-2 and Br-UiO-NH2-PL-2, and in Figure (b), the figures show [C4C4Im]Br, Br-UiO-PL-1 and Br-UiO-NH2-PL-1.

[0031] Figure 11 This is a flowchart illustrating the cycloaddition reaction route of propylene oxide and CO2 in this invention.

[0032] Figure 12 This is a comparison chart showing the effect of different catalysts on the catalytic conversion rate of this invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0034] To address the technical problem that existing porous liquid preparation processes are complex and can only achieve CO2 adsorption and storage without converting and applying the captured CO2, this invention provides a UiO-66-based porous liquid, its preparation method, and its applications. Using the metal-organic framework material UiO-66 or / and amino-modified UiO-66 as the porous host, and two ionic liquids, [C4C7Im]Br and [C4C4Im]Br, as sterically hindered solvents, a UiO-66-based porous liquid with high catalytic activity and high stability is prepared. This invention uses the prepared UiO-66-based porous liquid for CO2 adsorption and storage, and catalytically converts the captured CO2 into cyclic carbonates, elevating carbon capture to the level of carbon application.

[0035] The technical solution of the present invention will be analyzed and described in detail below.

[0036] This invention first provides a UiO-66-based porous liquid, which is made of metal-organic framework material UiO-66 or / and amino-modified metal-organic framework material UiO-66 and ionic liquid; the ionic liquid is [C4C7Im]Br and / or [C4C4Im]Br, wherein Im is an imidazole group;

[0037] The mass percentage of the metal-organic framework material UiO-66 or / and the amino-modified metal-organic framework material UiO-66 is 1% to 3%, and the mass percentage of the ionic liquid is 97% to 99%.

[0038] In the above technical solution, the metal-organic framework material UiO-66 or / and amino-modified metal-organic framework material UiO-66 are used as porous guests, and the two ionic liquids [C4C7Im]Br and [C4C4Im]Br are used as sterically hindered solvents. The prepared UiO-66-based porous liquid is used as a catalyst to catalyze the reaction of CO2 with propylene oxide. The catalytic activity of the UiO-66-based porous liquid is significantly improved compared with the corresponding sterically hindered solvents, indicating that the porous guest and the sterically hindered solvent have a synergistic catalytic effect in the porous liquid.

[0039] This invention also provides a method for preparing the above-mentioned UiO-66-based porous liquid, comprising the following steps:

[0040] Preparation of metal-organic framework material UiO-66 and amino-modified metal-organic framework material UiO-66

[0041] Preparation of UiO-66: First, prepare a beaker of about 100mL, weigh 60mL of DMF, and then weigh a certain amount of ZrCl4 and terephthalic acid (BDC). Add ZrCl4 and BDC to the DMF, and then add 6mL (or 10mL) of glacial acetic acid to the beaker. Place the beaker in an instrument and sonicate for at least 30 minutes to completely dissolve ZrCl4 and BDC in the DMF. After sonication, the solution becomes transparent. Pour the transparent solution into four small glass bottles, label them, and place them in an electric heating drying oven. Heat at 120℃ for 24 hours to obtain the sample. After heating, discard the supernatant from the four small glass bottles and pour the lower milky white liquid into centrifuge tubes for centrifugation. After centrifugation and washing, place the centrifuged sample in an electric heating drying oven at 70℃ to completely dry the solvent in the sample to obtain the final sample. Figure 5 As shown.

[0042] Preparation of amino-modified UiO-66: First, prepare a beaker of about 100 mL, weigh 60 mL of DMF, then weigh 0.48 g (2.058 mmol) of ZrCl4 and add it to the DMF. After sonicating for 10 min, allow the ZrCl4 to dissolve in the DMF. Then, add BDC-NH2 (372.81 mg, 2.058 mmol) to the beaker. After sonicating for 10 min, add 6 mL or (10 mL) of glacial acetic acid to the solution. Transfer the mixture to two polytetrafluoroethylene hydrothermal reactors (reaction vessels). Heat in an oven at 120℃ for 24 hours to obtain the sample. After heating, cool to room temperature, then discard the supernatant in the reaction vessel sample, and pour the lower brownish-red liquid into a centrifuge tube. Wash the sample three times with DMF and methanol at room temperature. After centrifugation and washing, place the sample in an oven and dry at 70℃ to obtain the sample. Figure 5 As shown.

[0043] Preparation of ionic liquid: Ethyl acetate and N-n-butylimidazolium were mixed to obtain a first reaction solution; ethyl acetate and a bromoalkane compound were mixed to obtain a second reaction solution; the first and second reaction solutions were mixed and stirred at 55℃~65℃ for 18~24h; ethyl acetate was removed to obtain the ionic liquid.

[0044] The ethanol suspension of the metal-organic framework material UiO-66 and / or the ethanol suspension of the amino-modified metal-organic framework material UiO-66 are mixed with the ethanol suspension of the ionic liquid, stirred at room temperature for 18-24 hours, and dried to obtain a UiO-66-based porous liquid.

[0045] It should be noted that the bromoalkane compound is 1-bromoheptane or bromobutane.

[0046] When the bromoalkane compound is 1-bromoheptane, the preparation method of the ionic liquid includes the following steps: Weigh 90g of ethyl acetate and add it to two beakers, adding 45g of ethyl acetate to each beaker. Weigh 23g of N-n-butylimidazole and 37g of 1-bromoheptane and add them to the two beakers respectively. Mix them evenly and then mix them together in a round-bottom flask. Heat the mixture in a water bath at 65°C using a constant temperature magnetic stirrer at 1200 rpm for 24 hours to obtain an ionic solution. Pour the stirred ionic solution into a beaker, discard the upper layer of liquid, and dry it in an oven at 70°C for more than 2 hours to obtain a slightly viscous, pale yellow liquid. Then wash it with ethyl acetate, stirring with a glass rod during the washing process. Wash 5-6 times, discard the upper layer of liquid, and finally dry it in an oven at 70°C for more than 5 hours to obtain a clear and transparent ionic liquid [C4C7Im]Br.

[0047] When the bromoalkane compound is bromobutane, the preparation method of the ionic liquid includes the following steps: Weigh 90g of ethyl acetate and add it to two beakers, adding 45g of ethyl acetate to each beaker. Weigh 23g of N-n-butylimidazole and 37g of bromobutane and add them to the two beakers respectively. Mix them evenly and then mix them together in a round-bottom flask. Heat the mixture in a water bath at 65°C using a constant temperature magnetic stirrer at 1200 rpm for 24 hours to obtain an ionic solution. Pour the stirred ionic solution into a beaker, discard the upper layer of liquid, and dry it in an oven at 70°C for more than 2 hours to obtain a slightly viscous, pale yellow liquid. Then wash it with ethyl acetate, stirring with a glass rod during the washing process. Wash 5-6 times, discard the upper layer of liquid, and finally dry it in an oven at 70°C for more than 5 hours to obtain a clear and transparent ionic liquid [C4C4Im]Br.

[0048] It should be noted that the molar ratio of the N-n-butylimidazole to the bromine atoms in the bromine alkane compound is 1:1.

[0049] In a preferred embodiment, the mass ratio of the metal-organic framework material UiO-66 or / and the amino-modified metal-organic framework material UiO-66 to the ionic liquid is 0.1:8 to 12.

[0050] The technical effects of the present invention will be described below with reference to specific embodiments.

[0051] Example 1

[0052] A UiO-66-based porous liquid is made of 1% by mass of metal-organic framework material UiO-66 and 99% by mass of ionic liquid; said ionic liquid is [C4C4Im]Br, wherein Im is imidazole.

[0053] The preparation method of the above-mentioned UiO-66-based porous liquid includes the following steps:

[0054] 0.1 g of pre-synthesized metal-organic framework material UiO-66 and 10 g of ionic liquid [C4C4Im]Br were weighed and placed in 10 mL of anhydrous ethanol. After ultrasonic treatment for 30 min, suspensions of porous material and ionic liquid were obtained. The two suspensions were then mixed and magnetically stirred at room temperature for 24 h to obtain a homogeneous mixture. After vacuum drying in a vacuum drying oven at 70 °C for 24 h, UiO-66-based porous liquid was obtained, denoted as Br-UiO-PL-1.

[0055] Example 2

[0056] A UiO-66-based porous liquid is made of 1% by mass of an amino-modified metal-organic framework material UiO-66 and 99% by mass of an ionic liquid; the ionic liquid is [C4C4Im]Br, wherein Im is an imidazole.

[0057] The preparation method of the above-mentioned UiO-66-based porous liquid includes the following steps:

[0058] 0.1 g of pre-synthesized metal-organic framework material UiO-66-NH2 and 10 g of ionic liquid [C4C4Im]Br were weighed and placed in 10 mL of anhydrous ethanol. After ultrasonic treatment for 30 min, suspensions of porous material and ionic liquid were obtained. The two suspensions were then mixed and magnetically stirred at room temperature for 24 h to obtain a homogeneous mixture. After vacuum drying in a vacuum drying oven at 70 °C for 24 h, UiO-66-based porous liquid was obtained, denoted as Br-UiO-NH2-PL-1.

[0059] Example 3

[0060] A UiO-66-based porous liquid is made of 1% by mass of metal-organic framework material UiO-66 and 99% by mass of ionic liquid; said ionic liquid is [C4C7Im]Br, wherein Im is imidazole.

[0061] The preparation method of the above-mentioned UiO-66-based porous liquid includes the following steps:

[0062] 0.1 g of pre-synthesized metal-organic framework material UiO-66 and 10 g of ionic liquid [C4C7Im]Br were weighed and placed in 10 mL of anhydrous ethanol. After ultrasonic treatment for 30 min, suspensions of porous material and ionic liquid were obtained. The two suspensions were then mixed and magnetically stirred at room temperature for 24 h to obtain a homogeneous mixture. After vacuum drying in a vacuum drying oven at 70 °C for 24 h, UiO-66-based porous liquid was obtained, denoted as Br-UiO-PL-2.

[0063] Example 4

[0064] A UiO-66-based porous liquid is made of 1% by mass of metal-organic framework material UiO-66-NH2 and 99% by mass of ionic liquid; wherein the ionic liquid is [C4C7Im]Br, wherein Im is an imidazole group.

[0065] The preparation method of the above-mentioned UiO-66-based porous liquid includes the following steps:

[0066] 0.1 g of pre-synthesized metal-organic framework material UiO-66-NH2 and 10 g of ionic liquid [C4C7Im]Br were weighed and placed in 10 mL of anhydrous ethanol. After ultrasonic treatment for 30 min, suspensions of porous material and ionic liquid were obtained. The two suspensions were then mixed and magnetically stirred at room temperature for 24 h to obtain a homogeneous mixture. After vacuum drying in a vacuum drying oven at 70 °C for 24 h, UiO-66-based porous liquid was obtained, denoted as Br-UiO-NH2-PL-2.

[0067] The properties of the UiO-66-based porous liquids prepared in Examples 1 to 4 above were characterized, and the results are as follows.

[0068] Scanning electron microscopy (SEM) analysis

[0069] This experiment observed the internal morphology, particle size, and shape of two different porous materials, metal-organic framework material UiO-66 and metal-organic framework material UiO-66-NH2, to further evaluate the differences in particle size distribution between the two porous materials and to determine whether the samples were generated.

[0070] X-ray diffraction analysis (XRD)

[0071] This experiment involved X-ray diffraction of porous MOFs, specifically UiO-66 and UiO-66-NH2, to analyze their diffraction patterns and obtain information about their composition, internal atomic or molecular structure or morphology.

[0072] Differential scanning calorimetry (DSC)

[0073] In this experiment, differential scanning calorimetry was used to test the liquid temperature range of the prepared porous material and ionic liquid, as well as four types of porous liquid. During the test, the temperature was increased to 200℃ at a rate of 10℃ / min, and then decreased to room temperature at a rate of 10℃ / min.

[0074] Thermogravimetric analysis (TGA)

[0075] The thermal stability of the samples was characterized by a thermogravimetric analyzer with a heating rate of 10℃ / min, using N2 as the test gas, and the test temperature range was from room temperature to 500℃.

[0076] Fourier Transform Infrared Spectroscopy (FT-IR)

[0077] In this experiment, the chemical composition of the samples was characterized using Fourier transform infrared spectroscopy (FT-IR), and the ATR reflectance method was employed for sample testing. The testing conditions were: scanning range 400 cm⁻¹. -1 ~4000cm -1 1.5cm resolution -1 The number of scans was 32, and the processing time for each scan was less than 1 minute.

[0078] cycloaddition reaction of carbon dioxide with epoxides

[0079] This paper describes the cycloaddition reaction of CO2 with epoxides using a micro-magnetic high-pressure reactor. After the reaction was completed and the reactor was cooled, the remaining products in the reactor were analyzed.

[0080] CO2 adsorption performance test

[0081] The CO2 adsorption performance of porous liquid was tested using an adsorption tester, and the measured data were analyzed.

[0082] Characterization results

[0083] Morphology regulation of porous objects

[0084] Porous guest materials are the source and basis of permanent pores in porous liquids. For metal-organic framework (MOF) materials like UiO-66 nanoparticles, the molar ratio of metal ions to ligands often affects the morphology and particle size distribution of the nanoparticles, thus influencing their pore size distribution and subsequent applications. The porous guest MOF materials UiO-66 and UiO-66-NH2 prepared in this invention were obtained via a hydrothermal method, with a zirconium source ZrCl4 and ligands BDC and BDC-NH2 in a mass ratio of 7:1. The UiO-66 and UiO-66-NH2 samples were scanned, and their microstructures were further characterized using scanning electron microscopy. The results are as follows: Figure 1 As shown.

[0085] Figure 1 Figures (a) and (b) are scanning electron microscope (SEM) images of the metal-organic framework material UiO-66 prepared in this invention at magnifications of 10,000 and 20,000, respectively. Figures (c) and (d) are SEM images of UiO-66-NH2 at magnifications of 10,000 and 40,000, respectively. Both types of nanoparticles have uniform particle size and regular morphology. It can be seen from the figures that both types of nanoparticles have polyhedral morphology. The size of UiO-66 is 100 nm to 150 nm, and the size of UiO-66-NH2 is 50 nm to 55 nm. The size distribution is uniform, and a relatively three-dimensional geometric morphology can be seen.

[0086] The crystal structures of metal-organic framework materials UiO-66 and UiO-66-NH2 were characterized by powder X-ray diffraction, and the results are as follows: Figure 2 As shown in the comparison of the XRD spectra of the prepared UiO-66 and UiO-66-NH2, the characteristic peak positions of the two nanoparticles are basically the same. It can be seen from the XRD spectra that the XRD diffraction peaks of the two porous guest particles UiO-66 and UiO-66-NH2 prepared by hydrothermal method are mainly reflected at 7.3°, 8.5° and 25.6°. The XRD results can prove that the present invention has successfully prepared UiO-66 and UiO-66-NH2.

[0087] Thermal stability characterization of porous objects

[0088] Thermal properties are among the most fundamental and important properties of materials. Thermogravimetric analysis was used to test the thermal stability of metal-organic framework materials UiO-66 and UiO-66-NH2 under a N2 atmosphere. Figure 3 As shown. By Figure 3 It can be seen that UiO-66 nanoparticles exhibit the best thermal stability, with significant mass loss only occurring after 87℃. Since both types of nanoparticles possess high specific surface area and high porosity, they adsorb large amounts of small-molecule solvents such as water and ethanol, resulting in weight loss due to solvent evaporation before 100℃. At 500℃, the residual masses of UiO-66 and UiO-66-NH2 are 66% and 57%, respectively, indicating good thermal stability for both types of nanoparticles.

[0089] Chemical structure characterization of porous guests

[0090] Depend on Figure 4 It can be seen that in the infrared spectra of porous guest metal-organic framework materials UiO-66 and UiO-66-NH2, at 3380 cm⁻¹... -1The broad peak at 1590 cm⁻¹ is a hydroxyl vibration peak, which may indicate that the porous guest molecules UiO-66 and UiO-66-NH₂ adsorbed moisture from the air before the test. -1 and 1390cm -1 The corresponding peaks at 1505 cm⁻¹ are attributed to the symmetric and asymmetric stretching vibrations of COO⁻ in the porous guest structure, respectively. -1 The peak at 1100 cm⁻¹ is the vibrational absorption peak of C=C in the benzene ring. -1 The peak at 822 cm⁻¹ represents the stretching vibration of the Zr-O single bond in the UiO-66 and UiO-66-NH₂ frameworks. -1 745cm -1 and 61cm -1 The peak at this point represents the vibrations of -OH and CH in the terephthalic acid ligand. The FT-IR results confirm that the porous guest molecules UiO-66 and UiO-66-NH2 were successfully prepared in this experiment.

[0091] Chemical structural characterization of ionic liquids

[0092] The chemical structures of the two ionic liquids, [C4C7Im]Br and [C4C4Im]Br, were further characterized using FT-IR. Figure 6 As shown, 2859cm -1 2930cm -1 and 2959cm -1 The characteristic peaks at 1561 cm⁻¹ are all attributed to the CH bonds on the alkyl chain of the ionic liquid. -1 and 1166cm -1 The characteristic peaks at these locations are attributed to the imidazole ring on the ionic liquid. The appearance of these characteristic peaks proves the successful preparation of the two ionic liquids, [C4C7Im]Br and [C4C4Im]Br.

[0093] Structural characterization of porous liquids

[0094] Using [C4C4Im]Br and [C4C7Im]Br as sterically hindered solvents, and with metal-organic framework materials UiO-66 and UiO-66-NH2 as porous guests, type III porous liquids Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2, and Br-UiO-NH2-PL-2 were prepared, respectively. The four prepared porous liquids were characterized by FT-IR, and the results are as follows: Figure 7 As shown in Figures (a) and (b), at 2858cm -1 2931cm -1 and 2957cm -1 The characteristic peak of the CH bond was observed at 1561 cm⁻¹. -1and 1166cm -1 Characteristic peaks belonging to the imidazole ring were observed at the 100°C. These characteristic peaks were all attributed to the sterically hindered solvents [C4C4Im]Br and [C4C7Im]Br of the four PLs. The amount of porous guest added did not affect the structure of the ionic liquid.

[0095] Stability characterization of porous liquids

[0096] One of the characteristics of type III porous liquids is that the porous guest remains stably dispersed in sterically hindered solvents for a long period without sedimentation or aggregation. To verify the stability of four porous liquids—Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2, and Br-UiO-NH2-PL-2—photographs of the four liquids before and after being placed at room temperature for a period of time were compared, such as... Figure 8 As shown. The porous material was uniformly dispersed in the PLs without obvious aggregation. After 120 days at room temperature, the appearance of the four PLs showed no significant changes; none of them exhibited obvious sedimentation or aggregation and still maintained good flowability. Figure 8 As shown in Figure (a), the morphology of the porous liquid was observed using transmission electron microscopy, as shown in Figure (a). Figure 8 As shown in Figures (b), (c), and (d), the porous guest is coated with a uniform ionic liquid layer. The porous guest is evenly distributed in the sterically hindered solvent without accumulation, demonstrating the successful preparation of the porous liquid.

[0097] Good thermal stability is an important prerequisite for PLs to be connected to industrial pipelines for industrial applications. The thermal stability of four porous liquids was characterized by thermogravimetric analysis and differential scanning calorimetry. The thermal behavior of the four porous liquids is as follows: Figure 9 As shown in Figures (a) and (b), no obvious melting or crystallization phenomena were observed in the four porous liquids between 25 and 200 °C, indicating that they were in a stable liquid state between 25 and 200 °C. This shows that the type of porous object has no significant effect on the liquid range of the porous liquid. All four PLs have a wide liquid range and are stable.

[0098] Figure 9 Figure (c) shows the TGA curves of PLs. Due to the strong hygroscopicity of ionic liquids, slight mass loss occurs before 100℃ due to the evaporation of small molecule solvents such as water. There is virtually no mass loss between 100℃ and 250℃. The mass loss that appears after 250℃ is clearly attributed to the thermal decomposition of the ionic liquid. After reaching 450℃, there is virtually no more mass loss, indicating that the ionic liquid has essentially decomposed. Since the amount of porous guest added to PLs is only 1wt%, the type of porous guest has no significant effect on the thermal decomposition temperature of PLs. In summary, the four types of PLs exhibit good thermal stability and can withstand temperatures of at least 250℃.

[0099] CO2 adsorption performance of porous liquids

[0100] To verify the adsorption capacity of porous liquids for CO2, the CO2 adsorption performance of four porous liquids was characterized by CO2 adsorption tests. The results are shown in [Figure number missing]. Figure 10 The CO2 adsorption capacity of porous liquids and their corresponding ionic liquids exhibits a non-linear relationship with pressure, indicating that in addition to physical adsorption, chemisorption also exists between porous liquids and ionic liquids and CO2. At pressures ranging from 1 bar to 2.5 bar, the CO2 adsorption capacity in porous liquids is significantly higher than that in ionic liquids, demonstrating the existence of permanent pores in the porous liquids.

[0101] Catalytic performance testing of porous liquids

[0102] The standard reaction is the cycloaddition of propylene oxide with CO2 to synthesize propylene carbonate, such as... Figure 11 As shown, the catalytic performance of ionic liquids [C4C4Im]Br and [C4C7Im]Br, and four porous liquids Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2, and Br-UiO-NH2-PL-2 was studied. In the experiment, the catalyst addition was 0.3 mL, the reactant propylene oxide addition was 5 mL, and the reaction was carried out at 95 °C and 1 MPa for 6 h. The catalytic conversion results are shown in the figure. Figure 12 As shown.

[0103] The formula for calculating the catalytic conversion rate is as follows:

[0104]

[0105] When [C4C7Im]Br is used as a catalyst, the conversion rate of propylene oxide is 55.26%. When the porous liquid Br-UiO-NH2-PL-1 is used as a catalyst, the conversion rate of propylene oxide is 68.78%. When the porous liquid Br-UiO-NH2-PL-2 is used as a catalyst, the conversion rate of propylene oxide is 78.90%.

[0106] Therefore, the catalytic performance of the porous liquid Br-UiO-NH2-PL is improved compared with that of the sterically hindered solvents [C4C4Im]Br and [C4C7Im]Br after the addition of the porous guest. This is attributed to the Lewis basicity of the N atom on the ionic liquid N-n-methylimidazolium in the porous guest, which can also activate and adsorb CO2, promoting the reaction between CO2 and propylene oxide. Simultaneously, the high specific surface area and high porosity of the porous guest facilitate sufficient contact between the reactants propylene oxide and CO2 and the catalytically active sites, promoting mass transfer of reactants and products, thereby increasing the catalytic effect.

[0107] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A UiO-66-based porous liquid, characterized in that, It is prepared using metal-organic framework material UiO-66 or / and metal-organic framework material UiO-66-NH2 as porous guest and ionic liquid [C4C7Im]Br and / or [C4C4Im]Br as sterically hindered solvent, wherein Im is an imidazole group; The mass percentage of the metal-organic framework material UiO-66 or / and the amino-modified metal-organic framework material UiO-66 is 1% to 3%, and the mass percentage of the ionic liquid is 97% to 99%, totaling 100%. The preparation method of the UiO-66-based porous liquid includes the following steps: Preparation of metal-organic framework material UiO-66 or / and amino-modified metal-organic framework material UiO-66; Preparation of ionic liquid: Ethyl acetate and N-n-butylimidazolium are mixed to obtain a first reaction solution; ethyl acetate and a bromoalkane compound are mixed to obtain a second reaction solution; the first and second reaction solutions are mixed and stirred at 55℃~65℃ for 18h~24h; ethyl acetate is removed to obtain the ionic liquid. The ethanol suspension of the metal-organic framework material UiO-66 and / or the ethanol suspension of the amino-modified metal-organic framework material UiO-66 are mixed with the ethanol suspension of the ionic liquid, stirred at room temperature for 18-24 hours, and dried to obtain a UiO-66-based porous liquid.

2. A method for preparing the UiO-66-based porous liquid according to claim 1, characterized in that, Includes the following steps: Preparation of metal-organic framework material UiO-66 or / and amino-modified metal-organic framework material UiO-66; Preparation of ionic liquid: Ethyl acetate and N-n-butylimidazolium are mixed to obtain a first reaction solution; ethyl acetate and a bromoalkane compound are mixed to obtain a second reaction solution; the first and second reaction solutions are mixed and stirred at 55℃~65℃ for 18h~24h; ethyl acetate is removed to obtain the ionic liquid. The ethanol suspension of the metal-organic framework material UiO-66 and / or the ethanol suspension of the amino-modified metal-organic framework material UiO-66 are mixed with the ethanol suspension of the ionic liquid, stirred at room temperature for 18h~24h, and dried to obtain a UiO-66-based porous liquid. The bromoalkane compound is 1-bromoheptane or bromobutane; The molar ratio of bromine atoms in the N-n-butylimidazole to those in the bromoalkane compound is 1:1; The mass ratio of the metal-organic framework material UiO-66 or / and amino-modified metal-organic framework material UiO-66 to the ionic liquid is 0.1:8~12.

3. The application of the UiO-66-based porous liquid of claim 1 in the catalytic conversion of CO2 to cyclic carbonates.

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