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

Abstract

The invention discloses a UiO-66-based porous liquid as well as a preparation method and application thereof, and belongs to the technical field of porous materials, the porous liquid is prepared by taking a metal organic framework material UiO-66 or / and a metal organic framework material UiO-66-NH2 as a porous object and taking ionic liquid [C4C7Im] Br and [C4C4Im] Br as steric hindrance solvents. The porous guest can be stably dispersed in the steric hindrance solvent, and benefited from a proper electrostatic repulsion effect, on the basis of DLVO colloidal stability theory inference, the electrostatic repulsion effect of the ionic liquid can counteract Van der Waals attractive force among nano particles, the dispersion stability of the porous guest in the ionic liquid is greatly improved, and the stable porous liquid is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of porous materials, and in particular to a UiO-66-based porous liquid and a preparation method and application thereof. Background Art

[0002] In recent years, global carbon emissions have increased rapidly, causing the CO2 content in the atmosphere to reach a record level, resulting in frequent catastrophic climate events, which seriously threatens 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 and epoxides can convert greenhouse gas CO2 into valuable chemical products such as cyclic carbonates. Therefore, the development of catalytic materials with high efficiency and selectivity for this reaction has always been a hot topic in the field of materials and catalysis.

[0003] UiO-66 (University of Oslo, UiO) is a metal-organic framework (MOFs) with high stability and large open pores. It has been widely studied as a catalytic material in the field of catalysis. However, for Lewis acid and base catalyzed CO2 cycloaddition reactions, UiO-66 usually needs to be in more stringent reaction conditions or in the presence of ionic liquid co-catalysts or solvents to show a certain catalytic effect. The acid and base site content of the UiO-66 framework can be increased by introducing functional groups, ionic liquid functionalization, manufacturing defects and compounding with other materials, thereby effectively improving the catalytic performance of the material for CO2 cycloaddition reactions.

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

[0005] Porous ionic liquids were successfully prepared by mixing metal-organic framework materials with ionic liquids to form a stable suspension. However, the existing porous liquid preparation process is complicated and can only be used for CO2 adsorption and storage, and the captured CO2 cannot be converted and applied. Summary of the invention

[0006] The present invention provides a UiO-66-based porous liquid and a preparation method and application thereof, which effectively solve the technical problems that the existing porous liquid preparation process is complicated and can only realize CO2 adsorption storage but cannot convert and apply the captured CO2. The present invention uses metal organic framework material UiO-66 or / and amino-modified metal organic framework material UiO-66 as porous objects, and uses two ionic liquids [C4C7Im]Br and [C4C4Im]Br as steric solvents to prepare a UiO-66-based porous liquid with high catalytic activity and high stability.

[0007] The first object of the present invention is to provide a UiO-66-based porous liquid, which is prepared by using metal organic framework material UiO-66 or / and metal organic framework material UiO-66-NH2 as porous guest and ionic liquid [C4C7Im]Br, [C4C4Im]Br as hindered solvent; the ionic liquid is [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%, which is 100% in total.

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

[0010] Preparing a metal organic framework material UiO-66 or / and an amino-modified metal organic framework material UiO-66;

[0011] Preparation of ionic liquid: ethyl acetate and N-n-butyl imidazole are mixed to obtain a first reaction liquid; ethyl acetate and a brominated alkane compound are mixed to obtain a second reaction liquid, the first reaction liquid and the second reaction liquid are mixed, stirred at 55° C. to 65° C. for reaction, and ethyl acetate is removed to obtain an ionic liquid;

[0012] The ethanol suspension of the metal organic framework material UiO-66 or / and 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] As a preferred embodiment, the brominated alkane compound is 1-bromoheptane or n-bromobutane.

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

[0015] As a preferred implementation manner, 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 0.1:8-12.

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

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

[0018] The third object of the present invention is to provide an application of the above-mentioned UiO-66-based porous liquid in catalyzing the conversion of CO2 into cyclic carbonates.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a UiO-66-based porous liquid, with metal organic framework material UiO-66 or / and metal organic framework material UiO-66-NH2 as porous objects, and ionic liquids [C4C7Im]Br and [C4C4Im]Br as steric solvents. The porous objects can be stably dispersed in the steric solvent, thanks to the appropriate electrostatic repulsion, based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) colloid stability theory, the electrostatic repulsion of the ionic liquid can offset the van der Waals attraction between nanoparticles, greatly improving the dispersion stability of the porous objects in the ionic liquid, and forming a stable porous liquid. The UiO-66-based porous liquid prepared by the present invention is used to catalyze the conversion of CO2 into cyclic carbonates. Not only can CO2 be adsorbed and stored, but the captured CO2 can also be converted into cyclic carbonates. When the UiO-66-based porous liquid prepared in Examples 1 to 4 of the present invention is used as a catalyst, the conversion rate of propylene oxide can reach 78.90%, while when the hindered solvent [C4C7Im]Br or [C4C4Im]Br is used as a catalyst, its conversion rate is far lower than that of the UiO-66-based porous liquid prepared by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] Figure 2 XRD diffraction patterns of UiO-66 and UiO-66-NH2 of the present invention.

[0023] Figure 3 These are the TGA curves of UiO-66 and UiO-66-NH2 of the present invention.

[0024] Figure 4 FT-IR spectra of the porous objects UiO-66 and UiO-66-NH2 of the present invention.

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

[0026] Figure 6 FT-IR chart of [C4C7Im]Br and [C4C4Im]Br of the present invention.

[0027] Figure 7 FT-IR spectra of the UiO-66-based porous liquid 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 These are sample photos and TEM images of Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2 and Br-UiO-NH2-PL-2 of the present invention, wherein Figure a is a sample photo of 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 porous liquids.

[0029] Fig. 9 1 and 2 are thermogravimetric curves of Br-UiO-PL and Br-UiO-NH2-PL of the present invention, wherein (a) is a DSC curve, (b) is a DSC curve, and (c) is a TGA curve.

[0030] Fig.10 These are CO2 adsorption curves of [C4C7Im]Br, [C4C4Im]Br of the present invention 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 embodiments, wherein (a) shows [C4C7Im]Br, Br-UiO-PL-2 and Br-UiO-NH2-PL-2, and (b) shows [C4C4Im]Br, Br-UiO-PL-1 and Br-UiO-NH2-PL-1.

[0031] Fig.11 The figure is a reaction route diagram of the cycloaddition of propylene oxide and CO2 according to the present invention.

[0032] Fig.12 This is a comparison chart of the effects of different catalysts of the present invention on catalytic conversion rate. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is further described below in conjunction with specific examples, but the examples are not intended to limit the present invention. The following test methods and detection methods, unless otherwise specified, are conventional methods; the reagents and raw materials, unless otherwise specified, are commercially available.

[0034] In view of the technical problems that the existing porous liquid preparation process is complicated and can only achieve CO2 adsorption storage, but cannot convert and apply the captured CO2, the present invention provides a UiO-66-based porous liquid and its preparation method and application. Using metal organic framework material UiO-66 or / and amino-modified metal organic framework material UiO-66 as porous objects, and two ionic liquids [C4C7Im]Br and [C4C4Im]Br as steric solvents, a UiO-66-based porous liquid with high catalytic activity and high stability is prepared. The present invention uses the prepared UiO-66-based porous liquid for the adsorption and storage of CO2, and catalytically converts the captured CO2, converting CO2 into cyclic carbonates, and elevating carbon collection to the level of carbon application.

[0035] The technical solution of the present invention is analyzed and explained in detail below.

[0036] The present invention first provides a UiO-66-based porous liquid, which is made of a metal organic framework material UiO-66 or / and an amino-modified metal organic framework material UiO-66 and an 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 scheme, the metal organic framework material UiO-66 or / and the amino-modified metal organic framework material UiO-66 is used as the porous guest, and the two ionic liquids [C4C7Im]Br and [C4C4Im]Br are used as the hindered solvents. The prepared UiO-66-based porous liquid is used as a catalyst to catalyze the reaction of CO2 and propylene oxide. The catalytic activity of the UiO-66-based porous liquid is significantly improved compared with the corresponding hindered solvent, indicating that the porous guest and the hindered solvent in the porous liquid have a synergistic catalytic effect.

[0039] The present 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, weigh a certain amount of ZrCl4 and terephthalic acid (BDC), then add ZrCl4 and BDC to DMF, then add 6mL or (10mL) of glacial acetic acid to the beaker, place the beaker in the instrument for ultrasonication for more than 30 minutes to completely dissolve ZrCl4 and BDC in DMF. After the ultrasonication is completed, the solution becomes transparent, pour the transparent solution into four small glass bottles, mark them and put them into an electric blast drying oven, heat them at 120℃ for 24 hours to obtain samples, after the heating is completed, pour out the supernatant in the four small glass bottle samples, pour the lower milky white liquid into a centrifuge tube, centrifuge, after the centrifugal washing is completed, put the centrifuged sample into an electric blast drying oven, and completely dry the solvent in the sample at 70℃ to obtain the sample, such as Figure 5 shown.

[0042] Preparation of amino-modified UiO-66: First, prepare a beaker of about 100 mL, weigh 60 mL of DMF, and then weigh 0.48 g (2.058 mmol) of ZrCl4 and add it to DMF. After ultrasonication for 10 minutes, let ZrCl4 dissolve in DMF, and then add BDC-NH2 (372.81 mg, 2.058 mmol) to the beaker. After ultrasonication for 10 minutes, add 6 mL or (10 mL) of glacial acetic acid to the solution, and transfer the mixture into two polytetrafluoroethylene hydrothermal reactors (reactors). Heat in an oven at 120°C for 24 hours to obtain a sample. After heating, cool to room temperature, then pour out the supernatant in the reactor sample, pour the lower brown-red liquid into a centrifuge tube, and centrifuge and wash three times with DMF and methanol at room temperature. After centrifugation and washing, put it in an oven and dry it at 70°C to obtain a sample, such as Figure 5 shown.

[0043] Preparation of ionic liquid: ethyl acetate and N-n-butylimidazole are mixed to obtain a first reaction liquid; ethyl acetate is mixed with a brominated alkane compound to obtain a second reaction liquid, the first reaction liquid and the second reaction liquid are mixed, stirred at 55° C. to 65° C. for 18 to 24 hours, and the ethyl acetate is removed to obtain an ionic liquid.

[0044] The ethanol suspension of the metal organic framework material UiO-66 or / and 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 to 24 hours, and dried to obtain a UiO-66-based porous liquid.

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

[0046] When the brominated alkane compound is 1-bromoheptane, the preparation method of the ionic liquid comprises the following steps: weighing 90g of ethyl acetate, adding them into two beakers respectively, adding 45g of ethyl acetate into each beaker, weighing 23g of N-n-butylimidazole and 37g of 1-bromoheptane respectively, adding them into two beakers respectively and mixing them evenly, finally mixing them together into a round-bottom flask, heating them in a water bath at 65°C for 24 hours using a constant temperature magnetic stirrer, and setting the speed to 1200 rpm to obtain an ionic solution, pouring the stirred ionic solution into a beaker, pouring out the upper layer of liquid, and drying it in an oven at 70°C for more than 2 hours to obtain a slightly viscous light yellow liquid, and then washing it with ethyl acetate, stirring it with a glass rod during the washing process, washing it 5 to 6 times, pouring out the upper layer of liquid, and finally drying 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 brominated alkane compound is n-butane bromide, the preparation method of the ionic liquid comprises the following steps: weighing 90g of ethyl acetate, adding them into two beakers respectively, adding 45g of ethyl acetate into each beaker, weighing 23g of N-n-butylimidazole and 37g of n-butane bromide respectively, adding them into two beakers respectively and mixing them evenly, finally mixing them together into a round-bottom flask, heating them in a water bath at 65°C for 24 hours using a constant temperature magnetic stirrer, and setting the speed to 1200 rpm to obtain an ionic solution, pouring the stirred ionic solution into a beaker, pouring out the upper layer of liquid, and drying it in an oven at 70°C for more than 2 hours to obtain a slightly viscous light yellow liquid, then washing with ethyl acetate, stirring with a glass rod during washing, washing 5 to 6 times, pouring out the upper layer of liquid, and finally drying 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 brominated alkane compound is 1:1.

[0049] As a preferred implementation manner, 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 0.1:8-12.

[0050] The technical effects of the present invention are described below in conjunction with specific embodiments.

[0051] Example 1

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

[0053] The method for preparing the above-mentioned UiO-66-based porous liquid comprises the following steps:

[0054] 0.1 g of the pre-synthesized metal organic framework material UiO-66 and 10 g of the ionic liquid [C4C4Im]Br were weighed and put into 10 mL of anhydrous ethanol respectively. After ultrasonic treatment for 30 min, a suspension of the porous material and the ionic liquid was obtained. Then the two suspensions were mixed and magnetically stirred at room temperature for 24 h to obtain a uniform mixed solution. After vacuum drying in a vacuum drying oven at 70 °C for 24 h, a UiO-66-based porous liquid was obtained, which was recorded as Br-UiO-PL-1.

[0055] Example 2

[0056] A UiO-66-based porous liquid is prepared from 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 imidazole.

[0057] The method for preparing the above-mentioned UiO-66-based porous liquid comprises the following steps:

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

[0059] Example 3

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

[0061] The method for preparing the above-mentioned UiO-66-based porous liquid comprises the following steps:

[0062] 0.1 g of the pre-synthesized metal organic framework material UiO-66 and 10 g of the ionic liquid [C4C7Im]Br were weighed and put into 10 mL of anhydrous ethanol respectively. After ultrasonic treatment for 30 min, a suspension of the porous material and the ionic liquid was obtained. Then the two suspensions were mixed and magnetically stirred at room temperature for 24 h to obtain a uniform mixed solution. After vacuum drying in a vacuum drying oven at 70 °C for 24 h, a UiO-66-based porous liquid was obtained, which was recorded as Br-UiO-PL-2.

[0063] Example 4

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

[0065] The method for preparing the above-mentioned UiO-66-based porous liquid comprises the following steps:

[0066] 0.1 g of the pre-synthesized metal organic framework material UiO-66-NH2 and 10 g of the ionic liquid [C4C7Im]Br were weighed and put into 10 mL of anhydrous ethanol respectively. After ultrasonic treatment for 30 min, a suspension of the porous material and the ionic liquid was obtained. The two suspensions were then mixed and magnetically stirred at room temperature for 24 h to obtain a uniform mixed solution. After vacuum drying in a vacuum drying oven at 70 °C for 24 h, a UiO-66-based porous liquid was obtained, recorded 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 analysis (SEM)

[0069] This experiment observed the internal organization morphology, particle size and form of two different porous materials, metal-organic framework material UiO-66 and metal-organic framework material UiO-66-NH2 samples, further evaluated the difference in particle size distribution between the two porous materials, and determined whether the samples were generated.

[0070] X-ray diffraction analysis (XRD)

[0071] In this experiment, X-ray diffraction was performed on the MOFs porous guests of the metal-organic framework material UiO-66 and the metal-organic framework material UiO-66-NH2, and the diffraction patterns of the two porous guests were analyzed to analyze the composition of the materials, the structure or morphology of the internal atoms or molecules, and other information.

[0072] Differential Scanning Calorimetry (DSC)

[0073] In this experiment, a differential scanning calorimeter was used to test the prepared porous materials, ionic liquids and the liquid temperature range of four porous liquids. During the test, the temperature was raised to 200°C at a rate of 10°C / min, and then cooled to room temperature at a rate of 10°C / min.

[0074] Thermogravimetric analysis (TGA)

[0075] The thermal stability of the samples was characterized and tested using a thermogravimetric analyzer with a heating rate of 10°C / min, the test gas being N2, and the test temperature ranging from room temperature to 500°C.

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

[0077] In this experiment, the chemical composition of the samples was characterized by Fourier transform infrared spectrometer (FT-IR), and the samples were tested by ATR reflection method. The test conditions were: scanning range 400cm -1 ~4000cm -1 , resolution 1.5cm -1 , scanning times 32 times, each processing time is less than 1min.

[0078] Cycloaddition reaction of carbon dioxide with epoxides

[0079] In this paper, a micro-magnetic high-pressure reactor was used to carry out the cycloaddition reaction of CO2 and epoxide. After the reaction was completed, the reactor was cooled and the remaining product in the reactor was analyzed.

[0080] CO2 adsorption performance test

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

[0082] Characterization results

[0083] Morphology control of porous guest

[0084] The porous guest is the source and basis of the permanent pores of the porous liquid. For the metal organic framework material UiO-66 nanoparticles, the molar ratio of metal ions to ligands often affects the morphology and particle size distribution of the nanoparticles, thereby affecting its pore size distribution and subsequent applications. The porous guest metal organic framework material UiO-66 and the metal organic framework material UiO-66-NH2 prepared by the present invention are obtained by a hydrothermal method, wherein the mass ratio of the zirconium source ZrCl4 to the ligands BDC and BDC-NH2 is 7:1. The UiO-66 and UiO-66-NH2 samples were scanned, and the microscopic morphology of the obtained UiO-66 and UiO-66-NH2 was further characterized by a scanning electron microscope. The results are as follows: Figure 1 shown.

[0085] Figure 1 Figure (a) and (b) are scanning electron microscope images of the metal organic framework material UiO-66 prepared by the present invention at magnifications of 10,000 and 20,000, and Figure (c) and (d) are scanning electron microscope images of UiO-66-NH2 at magnifications of 10,000 and 40,000. Both nanoparticles have uniform particle size and regular morphology. It can be seen from the figures that both nanoparticles are polyhedral in morphology, with UiO-66 having a size of 100nm to 150nm and UiO-66-NH2 having a size of 50nm to 55nm. 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 metal organic framework materials UiO-66-NH2 were characterized by powder X-ray diffraction. Figure 2 As shown in the figure, the XRD spectra of the prepared UiO-66 and UiO-66-NH2 are compared. The characteristic peak positions of the two nanoparticles are basically consistent. It can be seen from the XRD spectra that the XRD diffraction peaks of the two porous guest UiO-66 and UiO-66-NH2 particles prepared by the hydrothermal method are mainly reflected at 7.3°, 8.5° and 25.6°. The results of XRD can prove that the present invention successfully prepared UiO-66 and UiO-66-NH2.

[0087] Characterization of thermal stability of porous guests

[0088] Thermal properties are one of the most basic and important properties of materials. The thermal stability of metal organic framework materials UiO-66 and metal organic framework materials UiO-66-NH2 was tested in a N2 atmosphere using thermogravimetric analysis. Figure 3 As shown. Figure 3 It can be seen that UiO-66 nanoparticles have the best thermal stability, and significant mass loss occurs only after 87°C. Since both nanoparticles have high specific surface area and high porosity, and adsorb a large amount of small molecule solvents such as water and ethanol, there is weight loss caused by solvent volatilization before 100°C. At 500°C, the residual masses of UiO-66 and UiO-66-NH2 are 66% and 57%, respectively. Both nanoparticles have good thermal stability.

[0089] Chemical structure characterization of porous guests

[0090] Depend on Figure 4 It can be seen that in the infrared spectra of the porous guest metal organic framework material UiO-66 and the metal organic framework material UiO-66-NH2, the -1The broad peak at 1590 cm is the hydroxyl vibration peak. It is possible that before the test, the porous objects UiO-66 and UiO-66-NH2 adsorbed water from the air. -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. -1 The peak at 1100 cm is the vibration absorption peak of C=C in the benzene ring. -1 The peak at 822 cm is 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 peaks at 400 nm are the vibrations of -OH and CH in the terephthalic acid ligand. The results of FT-IR can prove that the porous guest UiO-66 and UiO-66-NH2 were successfully prepared in this experiment.

[0091] Chemical structure characterization of ionic liquids

[0092] FT-IR was used to further characterize the chemical structures of the two ionic liquids [C4C7Im]Br and [C4C4Im]Br. Figure 6 As shown, 2859cm -1 、2930cm -1 and 2959cm -1 The characteristic peaks at 1561 cm -1 and 1166cm -1 The characteristic peaks at 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 steric solvents, metal organic framework material UiO-66 and metal organic framework material UiO-66-NH2 as porous objects, 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. The results are shown in Figure 7 As shown in Figures (a) and (b), at 2858cm -1 、2931cm -1 and 2957cm -1 The characteristic peak of CH bond was observed at 1561cm -1and 1166cm -1 Characteristic peaks attributed to the imidazole ring were observed, which were all attributed to the hindered solvents [C4C4Im]Br and [C4C7Im]Br of the four PLs. The addition amount of porous guests had no effect on the structure of the ionic liquids.

[0095] Stability Characterization of Porous Liquids

[0096] One of the characteristics of type III PLs is that the porous guest can be stably dispersed in the hindered solvent for a long time without sedimentation and agglomeration. In order to verify the stability of the four porous liquids Br-UiO-PL-1, Br-UiO-NH2-PL-1, Br-UiO-PL-2 and Br-UiO-NH2-PL-2, the photos of the four PLs before and after being placed at room temperature for a period of time were compared, as shown in Figure 2. Figure 8 The porous guest is evenly dispersed in the PLs without obvious agglomeration. After 120 days at room temperature, the appearance of the four PLs has no obvious change, no obvious sedimentation and agglomeration occurs, and they still have good fluidity, as shown in Figure 2. Figure 8 The morphology of the porous liquid was observed using a transmission electron microscope, as shown in Figure (a). Figure 8 As shown in Figures (b), (c) and (d), the surface of the porous guest is covered with a uniform ionic liquid layer, and the porous guest is evenly distributed in the steric solvent without stacking, demonstrating the successful preparation of the porous liquid.

[0097] Good thermal stability is an important prerequisite for PLs to be connected to industrial pipelines and realize industrial applications. The thermal stability of four porous liquids was characterized by thermogravimetric analysis and differential scanning calorimetry. The thermal behaviors of the four porous liquids are as follows: Fig. 9 As shown in Figures (a) and (b) in Figure 1, no obvious melting and crystallization phenomena were observed for the four porous liquids at 25-200°C, indicating that they are all in liquid state between 25-200°C and the state is stable. It can be seen that the type of porous guest has no obvious effect on the liquid range of the porous liquid. The four PLs have a wide liquid range and are stable.

[0098] Fig. 9 Figure (c) shows the TGA curve of PLs. Due to the strong water absorption of ionic liquids, the volatilization of small molecule solvents such as water before 100°C causes a slight mass loss. There is basically no mass loss between 100°C and 250°C. The mass loss after 250°C is obviously attributed to the thermal decomposition of the ionic liquid. After the temperature reaches 450°C, there is basically no mass loss, indicating that the ionic liquid is basically decomposed. Since the amount of porous guest added to PLs is only 1wt%, the type of porous guest has no obvious effect on the thermal decomposition temperature of PLs. In short, the four PLs have good thermal stability and can withstand temperatures of at least 250°C.

[0099] CO2 adsorption properties of porous liquids

[0100] In order to confirm the adsorption effect of porous liquids on CO2, the CO2 adsorption performance of four porous liquids was characterized by CO2 adsorption test. The results are shown in Fig.10 The amount of CO2 adsorbed by porous liquids and corresponding ionic liquids is nonlinearly related to pressure, which indicates that there is not only physical adsorption but also chemical adsorption between porous liquids and ionic liquids and CO2. At 1 bar to 2.5 bar, the amount of CO2 adsorbed by porous liquids is significantly higher than that of ionic liquids, proving the existence of permanent pores in porous liquids.

[0101] Testing the catalytic properties of porous liquids

[0102] The standard reaction is the cycloaddition reaction of propylene oxide and CO2 to synthesize propylene carbonate. Fig.11 As shown in the figure, the catalytic performance of ionic liquids [C4C4Im]Br, [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 were studied. In the experiment, the amount of catalyst added was 0.3mL, the amount of reactant propylene oxide added was 5mL, and the reaction was carried out at 95℃ and 1MPa for 6h. The catalytic conversion results are shown in the figure. Fig.12 shown.

[0103] The calculation formula of catalytic conversion rate is:

[0104]

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

[0106] It can be seen that after adding the porous guest, the catalytic performance of the porous liquid Br-UiO-NH2-PL is improved compared with the hindered solvents [C4C4Im]Br and [C4C7Im]Br. This is attributed to the Lewis basicity of the N atom on the ionic liquid N-methylimidazole in the porous guest, which can also activate and adsorb CO2 and promote the reaction of CO2 with propylene oxide. At the same time, the high specific surface area and high porosity of the porous guest are conducive to the full contact between the reactants propylene oxide and CO2 and the catalytic active sites, which is conducive to the mass transfer of reactants and products, thereby increasing the catalytic effect.

[0107] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A UiO-66-based porous liquid, characterized in that: The method is prepared by using metal organic framework material UiO-66 or / and metal organic framework material UiO-66-NH2 as porous guest and ionic liquid [C4C7Im]Br, [C4C4Im]Br as steric solvent; the ionic liquid is [C4C7Im]Br and / or [C4C4Im]Br, 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%, which is 100% in total.

2. A method for preparing the UiO-66-based porous liquid according to claim 1, characterized in that: The following steps are involved: Preparing a metal organic framework material UiO-66 or / and an amino-modified metal organic framework material UiO-66; Preparation of ionic liquid: ethyl acetate and N-n-butyl imidazole are mixed to obtain a first reaction liquid; ethyl acetate and a brominated alkane compound are mixed to obtain a second reaction liquid, the first reaction liquid and the second reaction liquid are mixed, stirred at 55° C. to 65° C. for reaction, and ethyl acetate is removed to obtain an ionic liquid; The ethanol suspension of the metal organic framework material UiO-66 or / and 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.

3. The preparation method according to claim 2, characterized in that: The brominated alkane compound is 1-bromoheptane or n-bromobutane.

4. The preparation method according to claim 2, characterized in that: The molar ratio of the N-n-butylimidazole to the bromine atoms in the brominated alkane compound is 1:

1.

5. The preparation method according to claim 2, characterized in that: 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 0.1:8-12.

6. The preparation method according to claim 2, characterized in that: The stirring reaction time is 18 to 24 hours.

7. The preparation method according to claim 2, characterized in that: The stirring time at room temperature is 18 to 24 hours.

8. Use of the UiO-66-based porous liquid according to claim 1 in catalyzing the conversion of CO2 into cyclic carbonates.

Images