A low-cost preparation method for mixed-ligand UiO-66-based porous liquid and its application

Abstract

This invention belongs to the field of carbon dioxide capture and separation materials technology, and relates to a low-cost preparation method for a mixed-ligand UiO-66 porous liquid and its application. The method uses a mixed-ligand UiO-66-COOH constructed from terephthalic acid and isophthalic acid as the main component, and commercially available sterically hindered polyetheramine as the size-exclusion continuous phase. The porous liquid is constructed through ethanol-assisted dispersion and homogenization treatment. This method eliminates the need for expensive ionic liquids as the continuous medium and avoids complex surface grafting or functionalization modifications. The resulting porous liquid combines the structure of MOF materials with good liquid flowability, offering advantages such as stable dispersion, simple preparation process, wide availability of raw materials, and low cost. It can be widely applied in fields such as natural gas decarbonization, flue gas CO2 capture, industrial tail gas purification, and carbon resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of gas separation and carbon capture technology, and relates to the preparation process of porous liquid materials, specifically to a low-cost preparation method of a mixed ligand UiO-66-based porous liquid and its application. Background Technology

[0002] With the continuous increase in global greenhouse gas emissions, carbon dioxide (CO2) capture and resource utilization has become an important technological approach to achieving the "dual carbon" strategy. Currently, the most widely used CO2 capture technology in industry is the organic amine absorption method, represented by absorbents such as monoethanolamine (MEA) and diethanolamine (DEA). Although this type of process is mature and has high absorption efficiency, CO2 is mainly captured through chemical absorption, requiring high temperatures during absorbent regeneration, resulting in high energy consumption. Furthermore, it suffers from severe equipment corrosion, amine evaporation losses, and high operating and maintenance costs. Therefore, developing low-energy-consumption and highly stable CO2 capture materials is of great significance.

[0003] In recent years, metal-organic frameworks (MOFs) have been widely used in CO2 adsorption and separation due to their ultra-high specific surface area, tunable pore size, and rich pore structure. Among them, the UiO-66 series MOFs exhibit excellent thermal, chemical, and mechanical stability, showing promising application prospects in natural gas decarbonization, flue gas separation, and CO2 capture. However, MOF materials are usually in solid powder form, which leads to problems such as particle agglomeration, high mass transfer resistance, difficulties in continuous transport, and insufficient industrial adaptability, thus limiting their practical industrial applications.

[0004] To balance the structural integrity of MOF materials with the fluidity of liquid systems, porous liquids have gradually become an important research direction in the field of CO2 capture in recent years. Existing MOF-based porous liquids typically employ ionic liquids, surface-grafted polymers, or complex functionalization modifications as the continuous phase to ensure stable dispersion and structural preservation of MOF particles in the liquid. Although such systems can achieve good CO2 adsorption performance, they still have the following shortcomings: (1) The continuous phase often uses expensive ionic liquids or functionalized polymers, which has high raw material costs and is not conducive to industrial-scale application. (2) Most MOF particles require complex surface modification, grafting or functionalization, which makes the preparation process complicated and involves many reaction steps, increasing production costs. (3) Some systems use a large amount of organic modifiers, which not only reduces the effective pore volume of MOF, but may also weaken the gas diffusion rate, thereby affecting the adsorption performance; (4) Existing porous liquids focus more on improving adsorption capacity, but lack consideration for low-cost construction, high stability and continuous industrial applications.

[0005] Therefore, developing a MOF-based porous liquid that can be rapidly constructed using low-cost commercial raw materials without complex surface modification, while maintaining the MOF structure and excellent CO2 adsorption performance, is of great significance for promoting the large-scale application of CO2 capture materials. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, the present invention aims to provide a low-cost preparation method for mixed-ligand UiO-66-based porous liquids. By using the mixed-ligand UiO-66-COOH as the host and a sterically hindered polyether amine, such as commercially available sterically hindered polyether amines D230 or T403, as the size exclusion continuous phase, a porous liquid with long-term stability can be constructed without the need for an ionic liquid as a continuous medium or complex surface grafting modification. The polyether amine used is widely available, inexpensive, and industrially mature, significantly reducing material costs compared to existing ionic liquid systems while maintaining good fluidity, structure, and CO2 selective adsorption performance. This provides a new technical solution for the low-cost industrialization of MOF-based porous liquids.

[0007] The present invention adopts the following technical solution: In a first aspect, the present invention provides a low-cost method for preparing a mixed-ligand UiO-66-based porous liquid, comprising the following steps: Step 1: Add terephthalic acid, isophthalic acid and zirconium tetrachloride to a mixed solution of N,N-dimethylformamide and acetic acid and stir to obtain a precursor solution; Step 2: Place the precursor solution in a reaction vessel for a constant-temperature thermal reaction; Step 3: After the reactor has cooled naturally, the reactants are washed, centrifuged and dried to obtain UiO-66-COOH porous guest material; Step 4: The UiO-66-COOH porous guest is ultrasonically dispersed in anhydrous ethanol, and then a sterically hindered polyetheramine-ethanol mixture is added. The ethanol is removed by heating and stirring, and the mixture is dried to obtain the mixed ligand UiO-66-based porous liquid.

[0008] Furthermore, in step 1, the molar ratio of terephthalic acid, isophthalic acid, and zirconium tetrachloride is (7-11):(1-3):(10-12).

[0009] Furthermore, in step 1, the molar ratio of zirconium tetrachloride to N,N-dimethylformamide is (10-12):(2300-2900), and the volume ratio of N,N-dimethylformamide to acetic acid is (180-220):(6-8).

[0010] Furthermore, in step 2, the reaction vessel is a Teflon reaction vessel, the reaction temperature is 110℃~130℃, and the reaction time is 12h.

[0011] Furthermore, in step 3, the washing solution is N,N-dimethylformamide and anhydrous ethanol, and the washing is performed 2 to 3 times.

[0012] Furthermore, in step 4, the mass ratio of the UiO-66-COOH porous guest to anhydrous ethanol is 1:(3-5); the mass fraction of the sterically hindered polyetheramine in the sterically hindered polyetheramine-ethanol mixed solution is 20%-25%; and the mass ratio of the UiO-66-COOH porous guest to the sterically hindered polyetheramine is 1:(3-5).

[0013] Furthermore, the sterically hindered polyetheramine is commercial polyetheramine D230 or T403.

[0014] Furthermore, in step 4, during the heating and stirring process, the heating temperature is 110–130°C; a magnetic stirrer is used for stirring at a speed of 500–600 r / min.

[0015] In a second aspect, the present invention provides a mixed ligand UiO-66-based porous liquid, wherein the porous liquid is UiO-66-D230-PL or UiO-66-T403-PL, and is prepared according to the method described in any one of the first aspects.

[0016] Thirdly, the present invention provides the application of the mixed ligand UiO-66-based porous liquid described in the second aspect in the field of adsorption and separation of mixed gases containing carbon dioxide. The application scenarios include natural gas decarbonization, flue gas CO2 capture, industrial tail gas purification and carbon dioxide resource utilization.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a mixed ligand UiO-66-COOH as a porous guest and commercially available sterically hindered polyetheramine as a size exclusion continuous phase. It eliminates the need for expensive ionic liquids as continuous media and complex surface grafting or functionalization modifications, thereby constructing MOF-based porous liquids that combine permanent pore structure and liquid flowability. This significantly reduces material preparation costs and process complexity, which is beneficial for industrial-scale production.

[0018] 2. This invention utilizes the abundant carboxyl sites of the mixed ligand UiO-66-COOH to enhance the interfacial interaction between MOF particles and polyetheramine, enabling the porous bulk to be stably dispersed in the continuous phase and effectively maintaining the permanent pore structure of the MOF, thereby achieving both excellent gas mass transfer performance and good flow stability.

[0019] 3. The UiO-66-based porous liquid prepared by this invention exhibits excellent CO2 adsorption and selective separation performance. Under conditions of 303 K and 1 bar, the CO2 adsorption capacity of UiO-66-T403-PL reaches 0.831 mmol·g. - ¹, the CO2 / CH4 separation selectivity reaches over 80%, and the CO2 / N2 separation selectivity reaches over 100%, demonstrating excellent CO2 capture and gas separation capabilities.

[0020] 4. Compared with traditional chemical absorption systems such as MEA, this invention mainly relies on the permanent pore structure of MOF to achieve physical adsorption, which can effectively reduce regeneration energy consumption, reduce equipment corrosion and absorbent volatilization, improve the stability of material recycling, and reduce operation and maintenance costs.

[0021] 5. This invention uses commercially available polyetheramine as the continuous phase. The raw materials are widely available, inexpensive, and the preparation process is simple. The resulting porous liquid has low cost, high stability, and excellent CO2 capture and separation performance. It can be widely used in natural gas decarbonization, flue gas CO2 capture, industrial tail gas purification, and carbon resource utilization, and has good prospects for industrial application. Attached Figure Description

[0022] Figure 1 The images show the porous guest and porous liquid prepared according to this invention. Wherein: (a) is a physical image of the porous guest UiO-66-COOH; (b) is a physical image of the porous liquid UiO-66-T403-PL prepared in Example 4.

[0023] Figure 2 These are scanning electron microscope (SEM) images of the UiO-66-COOH porous guest and the UiO-66-based porous liquid prepared in this invention. Wherein: (a) is a SEM image of the UiO-66-COOH porous guest prepared in Example 1; (b) is a SEM image of the UiO-66-T403-PL prepared in Example 4; and (c) is a SEM image of the UiO-66-D230-PL prepared in Example 1.

[0024] Figure 3 The image shows the microstructure of UiO-66-D230-PL prepared in Example 1. Wherein: (a) is a transmission electron microscope (TEM) image; (b) is an EDS elemental distribution map.

[0025] Figure 4 The image shows the pore structure characterization of the UiO-66-COOH porous guest prepared in Example 1. The outer graph is the N2 adsorption-desorption isotherm diagram; the inner graph is the pore size distribution curve.

[0026] Figure 5 The Fourier transform infrared (FTIR) spectrum of the UiO-66-COOH porous guest prepared in Example 1 is shown.

[0027] Figure 6 The graph shows the test results of gas adsorption and separation performance of UiO-66-based porous liquid. Among them: (a) is the CO2 adsorption isotherm of UiO-66-T403-PL at 303 K; (b) is the CO2 adsorption isotherm of UiO-66-D230-PL at 303 K; (c) is the CH4 adsorption isotherm of UiO-66-T403-PL at 303 K; (d) is the N2 adsorption isotherm of UiO-66-T403-PL at 303 K; (e) is the IAST selectivity curve of CO2 / CH4 and CO2 / N2 mixed gas of UiO-66-T403-PL at 303 K; (f) is the selectivity comparison diagram of CO2 / CH4 and CO2 / N2 mixed gas of UiO-66-T403-PL at 303 K.

[0028] Figure 7 This is a comparison chart of the properties of the UiO-66-based porous liquid of the present invention with those of existing porous liquids. Wherein: (a) is a comparison chart of the CO2 adsorption capacity of UiO-66-T403-PL and UiO-66-D230-PL of the present invention with that of existing porous liquids; (b) is a comparison chart of the CO2 / N2 selectivity of UiO-66-T403-PL and UiO-66-D230-PL of the present invention with that of existing porous liquids; (c) is a comparison chart of the CO2 / CH4 selectivity of UiO-66-T403-PL and UiO-66-D230-PL of the present invention with that of existing porous liquids. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0030] Example 1 A low-cost method for preparing a mixed-ligand UiO-66-based porous liquid includes the following steps: S1. Add 1.5g terephthalic acid (9mmol), 0.3g isophthalic acid (1.8mmol) and 2.58g zirconium tetrachloride (11mmol) to a mixed solution of 200mL N,N-dimethylformamide (2.59mol) and 7mL acetic acid, and stir at 500r / min for 5min to obtain a precursor solution; S2. Transfer the precursor solution obtained in S1 to four 100mL Teflon reaction vessels and react at 120℃ for 12h. S3. After the reaction vessel from S2 has cooled naturally, the reactants are transferred to centrifuge tubes and dissolved in N,N-dimethylformamide and anhydrous ethanol, respectively. The solutions are then centrifuged at 10000 rpm for 3 minutes, the washing liquid is discarded, and the mixture is circulated three times. After drying at 80°C for 12 hours, a porous UiO-66-COOH guest material is obtained, with the following macroscopic morphology: Figure 1 As shown in (a), it is a white powdery solid. Figure 2 As shown in (a), the obtained UiO-66-COOH particles exhibit a regular polyhedral crystal morphology and relatively uniform particle size, indicating that the obtained material has good crystallinity. Figure 4 As shown in the external figure, UiO-66-COOH exhibits a typical Type I nitrogen adsorption isotherm; combined with Figure 4 The pore size distribution results in the inner diagram show that it still retains a rich microporous structure, indicating that the obtained material has a permanent porous structure. For example... Figure 5 As shown, characteristic absorption peaks related to the carboxyl group (–COOH) can be observed in the FTIR spectrum, indicating that the mixed ligand UiO-66-COOH was successfully constructed. S4. Add 1g of the UiO-66-COOH porous guest obtained in S3 to 5g of anhydrous ethanol and ultrasonically disperse for 5min. Simultaneously, add 20g of a 25% (w / w) D230 / ethanol mixed solution (where the mass of polyetheramine D230 is 5.0g, the mass of ethanol is 15.0g, and the mass ratio of porous guest to polyetheramine is 1:5) to the dispersed UiO-66-COOH. Stir at 500r / min on a magnetic stirrer at 120℃. After 95% of the anhydrous ethanol has evaporated, transfer the mixed liquid to an oven at 80℃ and dry for 12h to obtain UiO-66-D230-PL porous liquid. Figure 3 As shown in (a), the UiO-66 particles in UiO-66-D230-PL still maintain a complete crystal structure, and no obvious structural collapse was observed. Figure 3 As shown in (b), the EDS mapping results indicate a uniform distribution of Zr, O, C, and N elements, suggesting that the polyetheramine continuous phase is uniformly bonded to the UiO-66 particles, forming a stable porous liquid system. Meanwhile, from... Figure 2As shown in (c), the MOF particles in UiO-66-D230-PL can be uniformly dispersed in the polyetheramine continuous phase without obvious agglomeration, which is consistent with the TEM and EDS analysis results, indicating that the constructed porous liquid has good dispersion stability.

[0031] Example 2 A low-cost method for preparing a mixed-ligand UiO-66-based porous liquid includes the following steps: S1. Add 1.2 g terephthalic acid (7.2 mmol), 0.4 g isophthalic acid (2.4 mmol) and 2.40 g zirconium tetrachloride (10.3 mmol) to a mixed solution of 180 mL N,N-dimethylformamide (2.33 mol) and 6 mL acetic acid, and stir at 500 r / min for 10 min to obtain the precursor solution; S2. The precursor solution obtained in S1 was transferred to four 100 mL Teflon reaction vessels and reacted at 110 °C for 12 h. S3. After the reaction is completed and the product is naturally cooled, the product is first centrifuged with N,N-dimethylformamide at 10000 r / min for 5 min, washed twice, then centrifuged with anhydrous ethanol at 10000 r / min for 5 min, and finally dried under vacuum at 80℃ for 10 h to obtain UiO-66-COOH porous guest. S4. Add 1g of the UiO-66-COOH porous guest obtained in S3 to 3g of anhydrous ethanol and ultrasonically disperse for 10min. Then add 15g of a 20% (w / w) polyetheramine D230-ethanol mixed solution (where the mass of polyetheramine D230 is 3.0g, the mass of ethanol is 12.0g, and the mass ratio of porous guest to polyetheramine is 1:3). Stir at 600r / min at 110℃. After about 92.5% of the ethanol has evaporated, dry in an oven at 80℃ for 12h to obtain UiO-66-D230-PL porous liquid.

[0032] Example 3 A low-cost method for preparing a mixed-ligand UiO-66-based porous liquid includes the following steps: S1. Add 1.8 g terephthalic acid (11 mmol), 0.2 g isophthalic acid (1.2 mmol) and 2.70 g zirconium tetrachloride (11.6 mmol) to a mixed solution of 220 mL N,N-dimethylformamide (2.85 mol) and 8 mL acetic acid, and stir at 500 r / min for 10 min to obtain the precursor solution; S2. Transfer the precursor solution obtained in S1 to four 100mL Teflon reaction vessels and react at 130℃ for 12h. S3. After natural cooling, the sample was washed alternately with N,N-dimethylformamide and ethanol, centrifuged at 10000 r / min for 3 min, repeated 3 times, and dried at 80℃ for 12 h to obtain UiO-66-COOH porous guest. S4. Add 1g of UiO-66-COOH porous guest to 4g of anhydrous ethanol and ultrasonically disperse for 10min. Then add 20g of 20% (w / w) polyetheramine D230 ethanol solution (w / w of polyetheramine D230 is 4.0g, ethanol is 16.0g, and the mass ratio of porous guest to polyetheramine is 1:4). Stir at 130℃ and 600r / min. After 90% of the ethanol has evaporated, dry at 80℃ for 12h to obtain UiO-66-D230-PL porous liquid.

[0033] Example 4 A low-cost method for preparing a mixed-ligand UiO-66-based porous liquid includes the following steps: S1. Add 1.5g terephthalic acid (9mmol), 0.3g isophthalic acid (1.8mmol) and 2.58g zirconium tetrachloride (11mmol) to a mixed solution of 200mL N,N-dimethylformamide (2.59mol) and 7mL acetic acid, and stir at 500r / min for 5min to obtain a precursor solution; S2. Transfer the precursor solution obtained in S1 to four 100mL Teflon reaction vessels and react at 120℃ for 12h. S3. After the reaction vessel of S2 has cooled naturally, the reactants are transferred to centrifuge tubes and dissolved in N,N-dimethylformamide and anhydrous ethanol, respectively. After centrifugation at 10000r / min for 3min, the washing liquid is discarded and the mixture is circulated 3 times. After drying at 80℃ for 12h, UiO-66-COOH porous guest material is obtained. S4. Add 1g of the UiO-66-COOH porous guest obtained in S3 to 5g of anhydrous ethanol and ultrasonically disperse for 5min. Simultaneously, add 20g of a 25% (w / w) T403 / ethanol mixed solution (where the mass of polyetheramine T403 is 5.0g, the mass of ethanol is 15.0g, and the mass ratio of porous guest to polyetheramine is 1:5) to the dispersed UiO-66-COOH. Stir at 500r / min on a magnetic stirrer at 120℃. After 95% of the anhydrous ethanol has evaporated, transfer the mixed liquid to an oven at 80℃ and dry for 12h to obtain UiO-66-T403-PL porous liquid, the macroscopic morphology of which is as follows. Figure 1 As shown in (b), the liquid is a homogeneous white liquid. No obvious sedimentation was observed after standing, indicating that the obtained porous liquid has good macroscopic stability. Figure 2As shown in (b), UiO-66 particles are uniformly dispersed in the polyetheramine continuous phase without obvious agglomeration, indicating that ethanol-assisted dispersion and heating homogenization treatment are beneficial to improving the dispersion uniformity of MOF particles in the continuous phase. Figure 3 As shown in (a), the UiO-66 particles still maintain a complete crystal structure and no obvious structural collapse has occurred; Figure 3 As can be seen in (b), Zr, O, C and N elements are uniformly distributed, further proving that UiO-66 particles and polyetheramine continuous phase form a stable composite system.

[0034] Example 5 A low-cost method for preparing a mixed-ligand UiO-66-based porous liquid includes the following steps: S1. Add 1.2 g terephthalic acid (7.2 mmol), 0.4 g isophthalic acid (2.4 mmol) and 2.40 g zirconium tetrachloride (10.3 mmol) to a mixed solution of 180 mL N,N-dimethylformamide (2.33 mol) and 6 mL acetic acid, and stir at 500 r / min for 10 min to obtain the precursor solution; S2. The precursor solution obtained in S1 was transferred to four 100 mL Teflon reaction vessels and reacted at 110 °C for 12 h. S3. After the reaction is completed and the product is naturally cooled, the product is first centrifuged with N,N-dimethylformamide at 10000 r / min for 5 min, washed twice, then centrifuged with anhydrous ethanol at 10000 r / min for 5 min, and finally dried under vacuum at 80℃ for 10 h to obtain UiO-66-COOH porous guest. S4. Add 1g of UiO-66-COOH porous guest to 3g of anhydrous ethanol and ultrasonically disperse for 10min. Then add 15g of a 20% (w / w) polyetheramine T403 / ethanol mixed solution (where the mass of polyetheramine T403 is 3.0g, the mass of ethanol is 12.0g, and the mass ratio of porous guest to polyetheramine is 1:3). Stir at 600r / min at 110℃. After about 92.5% of the ethanol has evaporated, dry in an oven at 80℃ for 12h to obtain UiO-66-T403-PL porous liquid. Example 6 A low-cost method for preparing a mixed-ligand UiO-66-based porous liquid includes the following steps: S1. Add 1.8 g terephthalic acid (11 mmol), 0.2 g isophthalic acid (1.2 mmol) and 2.70 g zirconium tetrachloride (11.6 mmol) to a mixed solution of 220 mL N,N-dimethylformamide (2.85 mol) and 8 mL acetic acid, and stir at 500 r / min for 10 min to obtain the precursor solution; S2. Transfer the precursor solution obtained in S1 to four 100mL Teflon reaction vessels and react at 130℃ for 12h. S3. After natural cooling, wash with N,N-dimethylformamide and ethanol alternately, centrifuge at 10000r / min for 3min, repeat 3 times, and dry at 80℃ for 12h to obtain UiO-66-COOH; S4. Add 1g of UiO-66-COOH porous guest to 4g of anhydrous ethanol and ultrasonically disperse for 10min. Then add 20g of a 20% (w / w) polyetheramine T403 / ethanol solution (w / w) containing 4.0g of polyetheramine T403 and 16.0g of ethanol, with a mass ratio of porous guest to polyetheramine of 1:4. Stir at 130℃ and 600r / min. After 90% of the ethanol has evaporated, dry at 80℃ for 12h to obtain UiO-66-T403-PL porous liquid.

[0035] The preparation method established in this invention is applicable to different types of commercial polyetheramine continuous phases. By adjusting the type of polyetheramine and the mass ratio of the porous guest to the continuous phase, UiO-66-based porous liquids with good flowability, stability, and CO2 adsorption performance can be obtained. Among them, the T403 system exhibits superior overall adsorption and separation performance, while the D230 system demonstrates good method applicability and application flexibility, providing more options for the design of porous liquids under different operating conditions.

[0036] To systematically evaluate the technical effect of the mixed ligand UiO-66-based porous liquid prepared by the method of the present invention, the following comparative examples are set up: Comparative Example 1 A method for preparing a UiO-66-T403 mixture includes the following steps: S1. Add 1.5g terephthalic acid (9mmol), 0.3g isophthalic acid (1.8mmol) and 2.58g zirconium tetrachloride (11mmol) to a mixed solution of 200mL N,N-dimethylformamide (2.59mol) and 7mL acetic acid, and stir at 500r / min for 5min to obtain a precursor solution; S2. Transfer the precursor solution obtained in S1 to four 100mL Teflon reaction vessels and react at 120℃ for 12h. S3. After the reaction vessel of S2 has cooled naturally, the reactants are transferred to centrifuge tubes and dissolved in N,N-dimethylformamide and anhydrous ethanol, respectively. After centrifugation at 10000r / min for 3min, the washing liquid is discarded and the mixture is circulated 3 times. After drying at 80℃ for 12h, UiO-66-COOH porous guest material is obtained.

[0037] S4. Add 1g UiO-66-COOH directly to 5g polyetheramine T403 and mechanically stir at room temperature for 6h to obtain a mixture.

[0038] Because it has not undergone ethanol dispersion and high-temperature homogenization treatment, the UiO-66-COOH in the obtained system is unevenly dispersed, and it is prone to particle agglomeration and sedimentation, and the gas adsorption performance is low.

[0039] Comparative Example 2 A method for preparing a polyetheramine T403 liquid material includes the following steps: Take 20g of polyetheramine T403 and dry it in an oven at 80℃ for 12h. Then use it directly as an adsorption liquid. Its product performance is shown in Table 1.

[0040] Since the system does not contain the UiO-66-COOH structure, its CO2 adsorption capacity and CO2 / CH4 separation performance are significantly lower than those of the UiO-66 porous liquid system.

[0041] The CO2 adsorption and gas separation performance of the samples obtained in Examples 1-6 and Comparative Examples 1 and 2 were tested. Before the test, all samples were vacuum activated at 80 °C for 12 h to remove adsorbed impurities. Subsequently, the single-component adsorption isotherms of CO2, CH4, and N2 at 303 K were tested using a gas adsorption analyzer, and the CO2 / CH4 and CO2 / N2 selectivity were calculated based on the single-component adsorption data using the Ideal Adsorption Solution Theory (IAST).

[0042] Typical gas adsorption and separation test results are as follows: Figure 6 As shown. Figure 6 (a) and Figure 6 Figure (b) shows the CO2 adsorption isotherms of UiO-66-T403-PL and UiO-66-D230-PL of the present invention at 303 K. Both porous liquids showed good CO2 adsorption capacity, with UiO-66-T403-PL showing a higher CO2 adsorption capacity. Figure 6 (c) and Figure 6 The values ​​in (d) represent the adsorption isotherms of CH4 and N2 for UiO-66-T403-PL, respectively. The adsorption capacity is significantly lower for UiO-66-T403-PL than for CO2, indicating that the obtained porous liquid has a higher adsorption affinity for CO2. The IAST selectivity results calculated based on the single-component adsorption isotherms are shown below. Figure 6 (e) and Figure 6 (f) indicates that the UiO-66-based porous liquid prepared by this invention has good CO2 / CH4 and CO2 / N2 separation performance. Figure 6 It is mainly used to demonstrate the adsorption behavior of typical porous liquids and the gas separation law of the present invention.

[0043] The test results of each embodiment and comparative example are summarized in Table 1.

[0044] Table 1. Comparison of CO2 adsorption and gas separation performance of samples obtained in Examples 1-6 and Comparative Examples 1-2 As shown in Table 1, the UiO-66-based porous liquids constructed using the mixed ligand UiO-66-COOH as the porous guest and commercial polyetheramine as the continuous phase exhibit good CO2 adsorption capacity and gas separation performance. Among them, the UiO-66-T403-PL prepared in Example 4 shows the most outstanding overall performance, achieving a CO2 adsorption capacity of 0.831 mmol·g under conditions of 303 K and 1 bar. - ¹, CO2 / CH4 selectivity is greater than 80, and CO2 / N2 selectivity is greater than 100. The UiO-66-D230-PL prepared in Example 1 also maintained good CO2 adsorption capacity and CO2 / CH4 selectivity, indicating that the preparation method established in this invention is applicable to different commercial polyetheramine continuous phases and has good method universality. In contrast, Comparative Example 1, due to its failure to form a stable porous liquid structure, showed significantly reduced CO2 adsorption capacity and gas separation performance; Comparative Example 2, without the introduction of carboxyl groups into UiO-66 as a porous guest, exhibited lower CO2 adsorption capacity and gas separation performance than the examples of this invention, indicating that the mixed ligand UiO-66-COOH and the construction method of this invention are both beneficial for improving the stability of porous liquids and CO2 adsorption and separation performance.

[0045] To further evaluate the overall performance of the porous liquid obtained in this invention, Examples 1 and 4 were compared with typical MOF-based porous liquids reported in the literature. The results are as follows: Figure 7 As shown. Figure 7 (a) Compares the CO2 adsorption capacity of porous liquids with different MOF-based structures. Figure 7 (b) and Figure 7 (c) Comparison of CO2 / N2 and CO2 / CH4 selectivity. It can be seen that the UiO-66-based porous liquid prepared in this invention, while maintaining low-cost continuous phase and simple preparation process, still possesses CO2 adsorption and separation performance comparable to or even better than reported MOF-based porous liquids. Among them, UiO-66-T403-PL exhibits more outstanding overall performance, while UiO-66-D230-PL also demonstrates good CO2 adsorption capacity and gas separation performance, further verifying the good applicability of the method of this invention to different commercial polyetheramine continuous phases. Figure 7 The comparative data in this paper are all from publicly published literature on MOF-based porous liquids, and are statistically analyzed based on the corresponding test conditions of each literature to comprehensively evaluate the performance advantages of the material of this invention.

[0046] To evaluate the economics of this invention, a cost comparison was conducted between commonly used continuous phases of existing MOF-based porous liquids and the commercially available polyetheramine continuous phase used in this invention. The market reference prices of ionic liquids, functionalized polymers, and polyetheramines were obtained based on statistics of publicly available industrial-grade product prices, and were comprehensively compared considering factors such as the need for surface modification, the complexity of the preparation process, and industrialization costs. The results are shown in Table 2.

[0047] Table 2. Comparison of cost and process complexity of different MOF-based porous liquid continuous phases (market reference) As shown in Table 2, most existing MOF-based porous liquids use ionic liquids or functionalized polymers as the continuous phase. This not only results in high raw material costs but also typically requires surface modification or grafting, leading to complex preparation processes and high industrialization costs. This invention uses commercially available polyetheramine as the continuous phase, achieving stable construction of permanently porous liquids without surface functionalization. The market reference price for this continuous phase is only 30–150 RMB / kg, significantly lower than ionic liquid and functionalized polymer systems. Furthermore, the preparation process is simpler, making it more suitable for industrial application.

[0048] Using Example 4 as a typical example, a statistical analysis was performed on the single-batch preparation cost of UiO-66-T403-PL. Based on the actual input quantities of each raw material in Example 4 and combined with the market purchase prices of the corresponding reagents, the cost of each raw material was calculated, resulting in the single-batch preparation cost. The results are shown in Table 3.

[0049] Table 3. Cost and Quality Table for a Single Batch of UiO-66-T403-PL (Taking Example 4 as an Example) As shown in Table 3, the main cost in the preparation of a single batch of UiO-66-T403-PL comes from process solvents such as DMF and ethanol, while the cost of main raw materials such as ZrCl4, organic ligands, and polyetheramine accounts for a relatively small proportion. Furthermore, both DMF and ethanol can be recycled during industrial production, so the actual production cost will be significantly lower than the laboratory cost. Therefore, this invention uses commercially available polyetheramine to replace ionic liquids as the continuous phase, ensuring excellent CO2 adsorption and separation performance while possessing significant low-cost advantages and good potential for industrial application.

[0050] This invention provides a low-cost method for preparing a mixed-ligand UiO-66-based porous liquid. By using the mixed-ligand UiO-66-COOH as the porous guest and commercially available sterically hindered polyetheramine as the size-exclusion continuous phase, stable construction of the porous liquid is achieved without the need for expensive ionic liquids as the continuous medium or complex surface grafting or functionalization modifications. The resulting porous liquid maintains the MOF structure and good flowability while exhibiting high CO2 adsorption capacity and excellent CO2 / CH4 and CO2 / N2 selectivity. It also boasts advantages such as simple preparation process, wide availability of raw materials, low cost, good stability, and ease of industrial scale-up.

[0051] Compared with existing MOF-based porous liquids, this invention effectively reduces material preparation costs and process complexity, improves the feasibility of industrial applications, and can be widely used in fields such as natural gas decarbonization, flue gas CO2 capture, industrial tail gas purification, and carbon resource utilization. It provides a new technical solution for the large-scale, low-cost preparation and industrial application of MOF-based porous liquids.

[0052] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

[0053] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing a mixed-ligand UiO-66-based porous liquid, characterized in that, Includes the following steps: Step 1: Add terephthalic acid, isophthalic acid and zirconium tetrachloride to a mixed solution of N,N-dimethylformamide and acetic acid and stir to obtain a precursor solution; Step 2: Place the precursor solution in a reaction vessel for a constant-temperature thermal reaction; Step 3: After the reactor has cooled naturally, the reactants are washed, centrifuged and dried to obtain UiO-66-COOH porous guest material; Step 4: The UiO-66-COOH porous guest is ultrasonically dispersed in anhydrous ethanol, and then a sterically hindered polyetheramine-ethanol mixture is added. The ethanol is removed by heating and stirring, and the mixture is dried to obtain the mixed ligand UiO-66-based porous liquid.

2. The method for preparing the mixed ligand UiO-66-based porous liquid according to claim 1, characterized in that, In step 1, the molar ratio of terephthalic acid, isophthalic acid, and zirconium tetrachloride is (7-11):(1-3):(10-12).

3. The method for preparing the mixed ligand UiO-66-based porous liquid according to claim 2, characterized in that, In step 1, the molar ratio of zirconium tetrachloride to N,N-dimethylformamide is (10-12):(2300-2900), and the volume ratio of N,N-dimethylformamide to acetic acid is (180-220):(6-8).

4. The method for preparing the mixed-ligand UiO-66-based porous liquid according to claim 1, characterized in that, In step 2, the reactor is a Teflon reactor, the reaction temperature is 110℃~130℃, and the reaction time is 12h.

5. The method for preparing the mixed ligand UiO-66-based porous liquid according to claim 1, characterized in that, In step 3, the washing solution is N,N-dimethylformamide and anhydrous ethanol, and the washing is performed 2 to 3 times.

6. The method for preparing the mixed ligand UiO-66-based porous liquid according to claim 1, characterized in that, In step 4, the mass ratio of the UiO-66-COOH porous guest to anhydrous ethanol is 1:(3-5); the mass fraction of the sterically hindered polyetheramine in the sterically hindered polyetheramine-ethanol mixed solution is 20%-25%; and the mass ratio of the UiO-66-COOH porous guest to the sterically hindered polyetheramine is 1:(3-5).

7. The method for preparing the mixed ligand UiO-66-based porous liquid according to claim 1 or 6, characterized in that, The sterically hindered polyetheramine is commercial polyetheramine D230 or T403.

8. The method for preparing the mixed ligand UiO-66-based porous liquid according to claim 1, characterized in that... In step 4, the heating and stirring process is carried out at a temperature of 110-130°C; a magnetic stirrer is used for stirring at a speed of 500-600 r / min.

9. A mixed-ligand UiO-66-based porous liquid, wherein the porous liquid is UiO-66-D230-PL or UiO-66-T403-PL, prepared by the method according to any one of claims 1-8.

10. The application of the mixed ligand UiO-66-based porous liquid of claim 9 in the field of adsorption and separation of carbon dioxide-containing mixed gases, characterized in that, Application scenarios include natural gas decarbonization, flue gas CO2 capture, industrial exhaust gas purification, and carbon dioxide resource utilization.

Images