A method for preparing hydrophobic porous liquid photocatalytic materials and their applications

Abstract

This invention belongs to the field of environmental and energy materials synthesis technology, specifically relating to a method for preparing a hydrophobic porous liquid photocatalyst and its application. The steps are as follows: First, NH2-UIO-66 is prepared. Then, through surface engineering strategies, NH2-UIO-66 is used as a carrier and combined with hydrophobic PDMS to form a new hydrophobic porous liquid (NH2-UIO-66PL). Due to the hydrophobicity of the long organic chains of PDMS, it can significantly reduce the concentration of water molecules on its surface during the photocatalytic CO2 reduction reaction in the aqueous phase, while providing multiple transport channels for CO2. This allows CO2 molecules to easily pass through the hydrophobic PDMS layer into the surface of the catalyst, thus significantly increasing the CO2 concentration on the catalyst surface. While increasing the CO2 concentration on the catalyst surface, the concentration of water molecules on the surface is controlled, thereby promoting the surface reaction rate of photocatalytic CO2 reduction.

Description

Technical Field

[0001] This invention belongs to the field of environmental and energy material synthesis technology, specifically relating to a method for preparing hydrophobic porous liquid photocatalytic materials and their applications. Background Technology

[0002] In recent years, with human production and development, atmospheric CO2 emissions have been continuously increasing. Excessive CO2 emissions lead to global warming, affecting not only the growth of plants and animals but also human survival and sustainable socio-economic development. Photocatalytic CO2 reduction uses solar energy to convert CO2 into fuels or other high-value-added chemicals. This not only reduces CO2 concentration but also converts solar energy into easily transportable and stored green fuels, which is of great significance for the utilization and storage of solar energy and the resource utilization of CO2.

[0003] Currently, most photocatalytic CO2 reduction reactions are carried out in a liquid phase using water as the solvent due to its low cost, energy efficiency, environmental friendliness, and mild reaction conditions. However, the supply of CO2 molecules is crucial to the efficiency of the photocatalytic CO2 reduction reaction because CO2 molecules adsorbed on the catalyst surface can be rapidly depleted under strong reaction driving forces. Nevertheless, CO2 has low solubility in water, resulting in low CO2 molecule concentration and slow diffusion rate on the catalyst surface. Converting the hydrophilic catalyst surface to a hydrophobic surface can help increase the CO2 concentration on the catalyst surface, thereby further improving the reaction rate of the photocatalytic CO2 reduction reaction in the aqueous phase.

[0004] The UIO-66-based porous liquid photocatalyst possesses a hydrophobic surface, which inhibits the adsorption of water molecules and enhances the adsorption and mass transfer of CO2 molecules, thereby increasing the CO2 concentration on the catalyst surface. This is due, on one hand, to the unique permanent porosity and fluidity of the porous liquid, which promotes the dissolution and diffusion of CO2 in water; and on the other hand, to the introduction of hydrophobic PDMS (poly(dimethylsiloxane) diglycidyl ether) as its outer liquid layer, which imparts a good hydrophobic surface, promoting the adsorption of CO2 by the catalyst. This increases the CO2 concentration on the catalyst surface while simultaneously regulating the water molecule concentration, thus promoting the surface reaction rate of CO2 photocatalytic reduction. Currently, there are no reports on the efficient conversion of CO2 using the UIO-66-based porous liquid photocatalyst. Summary of the Invention

[0005] To address the issues of low CO2 molecule concentration and slow diffusion rate on catalyst surfaces and achieve efficient CO2 conversion, this invention uses NH2-UIO-66 as a carrier and combines it with hydrophobic PDMS through surface engineering strategies to form a novel hydrophobic porous liquid (NH2-UIO-66PL). Because NH2-UIO-66PL retains the abundant micropores of NH2-UIO-66 and the -NH- groups formed within it, its CO2 adsorption performance is enhanced. Simultaneously, the good flowability of NH2-UIO-66PL promotes the dissolution and diffusion of CO2 in water. Furthermore, due to the hydrophobicity of the long organic chains of PDMS, NH2-UIO-66PL can significantly reduce the concentration of water molecules on its surface during photocatalytic CO2 reduction in the aqueous phase, while providing multiple transport channels for CO2. This allows CO2 molecules to easily pass through the hydrophobic PDMS layer and enter the catalyst surface, thus significantly increasing the CO2 concentration on the catalyst surface. Therefore, NH2-UIO-66PL has higher photocatalytic CO2 reduction performance than NH2-UIO-66 and PDMS, with CO and CH4 yields of 24.70 μmol / g / h and 7.93 μmol / g / h, respectively.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution;

[0007] A method for preparing a hydrophobic porous liquid photocatalyst, comprising the following steps:

[0008] Step 1: Synthesis of NH2-UIO-66:

[0009] Zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide. Formic acid was then added as a regulator, and the mixture was sonicated to obtain a mixed solution. The resulting mixed solution was then transferred to a polytetrafluoroethylene autoclave, and the autoclave was placed in an oven for reaction under certain conditions. After the reaction was completed, the product in the autoclave was collected by centrifugation and washed sequentially with N,N-dimethylformamide, acetone, and ethanol. Finally, the washed product was dried to obtain the product NH2-UIO-66.

[0010] Step 2: Synthesis of hydrophobic porous liquid photocatalyst (NH2-UIO-66PL):

[0011] The NH2-UIO-66 and PDMS prepared in step 1 were dissolved in a mixture of acetone and 2-butanone, respectively. The mixture was ultrasonically treated to obtain an NH2-UIO-66 suspension and a PDMS solution. Then, the NH2-UIO-66 suspension was added to the PDMS solution. After stirring and reacting, the solvent was evaporated in an oil bath at a certain temperature. The resulting solution was then vacuum dried under certain conditions. The product obtained after drying is the hydrophobic porous liquid photocatalyst, denoted as NH2-UIO-66PL.

[0012] Preferably, in step 1, the ratio of zirconium tetrachloride, 2-aminoterephthalic acid, N,N-dimethylformamide and formic acid is 1 mmol: 1 mmol: 100 mL: 4.3 mL.

[0013] Preferably, in step 1, the ultrasound time is 30 minutes.

[0014] Preferably, in step 1, the reaction temperature under certain conditions is 120°C and the reaction time is 12 hours.

[0015] Preferably, in step 1, the drying is vacuum drying at a temperature of 150°C for 12 hours.

[0016] Preferably, in step 2, the dosage of NH2-UIO-66, PDMS, acetone and 2-butanone is in the following ratio: 0.2g: 1.2g: 40mL: 0.4mL.

[0017] Preferably, in step 2, the ultrasound time is 10 minutes.

[0018] Preferably, in step 2, the temperature of the stirring reaction is 40°C and the reaction time is 20 hours.

[0019] Preferably, in step 2, the temperature of the oil bath evaporation under certain temperature conditions is 70°C, and the evaporation time is 4-8 hours.

[0020] Preferably, in step 2, the vacuum drying temperature is 60°C and the drying time is 24 hours.

[0021] The hydrophobic porous liquid photocatalyst of the present invention, through a surface engineering strategy, uses NH2-UIO-66 as a support and combines it with hydrophobic PDMS to form a new hydrophobic porous liquid (NH2-UIO-66PL), which enhances the adsorption and mass transfer capacity of CO2 molecules, thereby increasing the CO2 concentration on the catalyst surface and effectively improving the photocatalytic reduction performance of CO2.

[0022] The hydrophobic porous liquid photocatalyst prepared in this invention is used for photocatalytic CO2 reduction.

[0023] The beneficial effects of this invention are:

[0024] (1) The hydrophobic porous liquid photocatalyst prepared by the present invention has the unique permanent porosity and fluidity of porous liquid, which promotes the dissolution and diffusion of CO2 in water.

[0025] (2) The hydrophobic porous liquid photocatalyst prepared in this invention retains the abundant micropores of NH2-UIO-66 and the -NH- groups formed inside it, which can promote the adsorption of CO2 by the catalyst.

[0026] (3) The hydrophobic porous liquid photocatalyst prepared in this invention increases the CO2 concentration on the catalyst surface while regulating the water molecule concentration on the surface, thereby promoting the surface reaction rate of its photocatalytic reduction of CO2.

[0027] (4) The hydrophobic porous liquid photocatalyst prepared in this invention can significantly reduce the concentration of water molecules on its surface when the long organic chain of PDMS is carried out in the aqueous phase, due to the hydrophobicity of PDMS. At the same time, it provides multiple transport channels for CO2, so that CO2 molecules can easily enter the surface of the catalyst through the hydrophobic layer of PDMS, thus significantly increasing the concentration of CO2 on the catalyst surface. Attached Figure Description

[0028] Figure 1 The images show the Fourier transform infrared spectra of different samples; the samples are PDMS, NH2-UIO-66, and NH2-UIO-66PL, respectively.

[0029] Figure 2 The images show the TEM spectra of different samples; where a represents NH2-UIO-66 and b represents NH2-UIO-66PL.

[0030] Figure 3 The flowability graph of NH2-UIO-66PL after being placed at room temperature for 240 days.

[0031] Figure 4 The images show the DSC curves for different samples; the samples are NH2-UIO-66PL and PDMS, respectively.

[0032] Figure 5 CO2 adsorption capacity graphs of different samples; the samples are NH2-UIO-66, NH2-UIO-66PL and PDMS.

[0033] Figure 6 The diagram shows the water contact angles of different samples; where a represents NH2-UIO-66 and b represents NH2-UIO-66PL.

[0034] Figure 7The graph shows the photocatalytic CO2 reduction yield of different samples; the samples are NH2-UIO-66, NH2-UIO-66PL and PDMS, respectively.

[0035] Figure 8 The diagram shows the CO2 reduction cycle experiment of NH2-UIO-66PL. Detailed Implementation

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0040] Evaluation of photocatalytic CO2 reduction activity: 10 mg of photocatalyst was mixed in a 20 mL reaction solution containing 18 mL of deionized water and 2 mL of TEOA in a 100 mL quartz glass reactor. The reactor was then purged with pure CO2 gas (purity >99.999%) for 10 minutes, followed by vacuum pressurization at least twice to ensure complete removal of all impurities and residual air. Before illumination, the reactor was installed on a CEL-SPH2N photocatalytic CO2 reduction reaction system equipped with a 300W xenon lamp to simulate sunlight, with a magnetic stirrer (300 rpm) below the system. The xenon lamp and magnetic stirrer were then turned on, and gas was sampled every hour. After 5 hours of photocatalytic reaction, the xenon lamp was turned off, and the resulting mixture was retained. Gas chromatography (GC-2030) equipped with a thermal conductivity detector and a flame ionization detector was used to analyze possible gaseous and liquid products, with Ar as the carrier gas, a flow rate of 20 mL / min, and a column oven temperature of 333 K.

[0041] Example 1:

[0042] (1) Synthesis of NH2-UIO-66: 1 mmol zirconium tetrachloride and 1 mmol 2-aminoterephthalic acid were dissolved in 100 mL N,N-dimethylformamide; then, 4.3 mL formic acid was added as a regulator. After sonicating the resulting mixture for half an hour, the mixture was transferred to a polytetrafluoroethylene autoclave and placed in an oven. The reaction was carried out at 120 °C for 12 hours. After the reaction was completed, the product in the autoclave was collected by centrifugation and washed with N,N-dimethylformamide, acetone and ethanol in sequence. Finally, the washed product was dried at 150 °C for 12 hours to obtain NH2-UIO-66.

[0043] (2) Synthesis of hydrophobic porous liquid photocatalyst (NH2-UIO-66PL): 0.2 g of NH2-UIO-66 and 1.2 g of PDMS were dissolved in a mixture of 40 mL of acetone and 0.4 mL of 2-butanone, respectively. The mixture was ultrasonically treated for 10 minutes to obtain an NH2-UIO-66 suspension and a PDMS solution. The NH2-UIO-66 suspension was then added to the PDMS solution, and the resulting mixture was stirred vigorously at 40 °C for 20 hours to ensure complete dissolution. Finally, the solvent was evaporated in a 70 °C oil bath for 4-8 hours, and the resulting solution was dried in a 60 °C vacuum drying oven for 24 hours. The product obtained was the hydrophobic UIO-66-based porous liquid photocatalyst, denoted as NH2-UIO-66PL.

[0044] Figure 1 The images show the Fourier transform infrared spectra of different samples. The characteristic peak of NH2-UIO-66 is consistent with the peak reported in the literature (Wang G, He CT, Huang R, et al. Photoinduction of Cu single atoms decorated on UiO-66-NH2 for enhanced photocatalytic reduction of CO2 to liquid fuels[J]. Journal of the American Chemical Society, 2020, 142: 19339-19345.).

[0045] Furthermore, some new characteristic peaks appeared in the FT-IR curve of NH2-UIO-66PL compared to NH2-UIO-66. These peaks are located at 786 cm⁻¹. -1 1012cm -1 and 2962cm -1These belong to the -CH3, Si-O, and Si-(CH3)2 groups of PDMS, respectively. NH2-UIO-66PL at 3100 cm⁻¹ -1 -3400cm -1 The intensity of the broad absorption peak at 3300 cm⁻¹ weakens significantly, indicating a decrease in the amount of -NH₂. Meanwhile, at 3300 cm⁻¹... -1 A stretching mode peak of -NH- appeared at the position, corresponding to a secondary amine, proving that the -NH2 in NH2-UIO-66 is covalently bonded to the epoxy group of PDMS.

[0046] Furthermore, characteristic peaks of NH2-UIO-66, such as 1382 cm⁻¹, appeared in the FT-IR curve of NH2-UIO-66PL. -1 and 1574cm -1 The peaks at these locations correspond to CN and O=CO groups, respectively, and these characteristic peaks did not appear in PDMS. These conclusions demonstrate the successful preparation of NH2-UIO-66PL.

[0047] Figure 2 TEM images of different samples are shown, where (a) is NH2-UIO-66 and (b) is NH2-UIO-66PL; Figure 2 As shown in Figure (a), the original NH2-UIO-66 has an octahedral shape with a size of 100-200 nm. Figure 2 As shown in Figure (b), the NH2-UIO-66 particles are encapsulated by an outer layer of gelatinous material. These results demonstrate a tight bond between NH2-UIO-66 and PDMS, maintaining the original structure of NH2-UIO-66, indicating the successful synthesis of NH2-UIO-66PL.

[0048] Figure 3 The graph shows the flowability of NH2-UIO-66PL after being stored at room temperature for 240 days. After 240 days, NH2-UIO-66PL also showed good flowability, which also proves its excellent stability at room temperature.

[0049] Figure 4 DSC curves for different samples; melting temperature (T) of NH2-UIO-66PL. m The temperature is around -94℃, which is much lower than room temperature. This corresponds to the melting temperature of PDMS, indicating that it has good liquid flowability at room temperature.

[0050] Figure 5The graph shows the CO2 adsorption capacity of different samples. NH2-UIO-66PL showed a CO2 adsorption capacity of 5.76 mmol / g at 298 K and 4 bar, while the corresponding adsorption capacities of PDMS and NH2-UIO-66 were 1.18 mmol / g and 3.30 mmol / g, respectively.

[0051] Therefore, compared to PDMS and NH2-UIO-66, NH2-UIO-66PL exhibits the highest CO2 adsorption capacity. This superior adsorption capacity reflects the continued existence of porous cavities within the porous liquid, and also demonstrates that covalently combining NH2-UIO-66 and PDMS to form NH2-UIO-66PL can significantly enhance its CO2 adsorption capacity, thereby promoting the surface reaction rate of CO2 photocatalytic reduction by NH2-UIO-66PL.

[0052] Figure 6 The diagram shows the water contact angles of different samples. The contact angle of NH2-UIO-66 is 31°, indicating its hydrophilic nature. When combined with hydrophobic PDMS to form a porous liquid, its contact angle increases to 116°, demonstrating its hydrophobicity. PDMS provides NH2-UIO-66PL with liquid flowability, promoting the dissolution and diffusion of CO2 in water. Simultaneously, due to the hydrophobicity of the long organic chains of PDMS, NH2-UIO-66PL significantly reduces the concentration of water molecules on its surface during photocatalytic CO2 reduction in the aqueous phase, and also provides multiple transport channels for CO2. Because CO2 is hydrophobic, CO2 molecules can easily pass through the hydrophobic PDMS layer into the catalyst surface, thus significantly increasing the CO2 concentration on the catalyst surface and thereby improving the surface reaction rate.

[0053] Figure 7 The figures show the photocatalytic CO2 reduction yields of different samples. NH2-UIO-66 exhibited poor photocatalytic performance, with a CO yield of 10.90 μmol / g / h and a CH4 yield of 2.90 μmol / g / h after 5 h of reaction. However, by combining NH2-UIO-66 with PDMS to form a porous liquid, NH2-UIO-66PL showed excellent CO and CH4 yields of 24.70 μmol / g / h and 7.93 μmol / g / h, respectively, achieving unexpectedly significant results. This may be because NH2-UIO-66PL not only significantly enhances its CO2 adsorption capacity, but the long organic chains of PDMS also significantly increase the CO2 concentration on the catalyst surface due to their hydrophobicity.

[0054] Figure 8The graphs show the cyclic test results for different samples; NH2-UIO-66PL exhibited a stable increasing trend in CO and CH4 production during this period, confirming its good photostability.

[0055] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. Use of a hydrophobic porous liquid photocatalyst for photocatalytic reduction of CO2, characterized in that, The preparation of the hydrophobic porous liquid photocatalyst comprises the following steps: Step 1: synthesis of NH2-UIO-66: Zirconium tetrachloride and 2-amino terephthalic acid are dissolved in N,N-dimethylformamide; then, formic acid is added as a regulator, and a mixed solution is obtained after ultrasonic treatment, and the obtained mixed solution is transferred to a polytetrafluoroethylene high-pressure kettle, and the reaction kettle is placed in an oven, and reacted under certain conditions, and after the reaction is completed, the product in the reaction kettle is collected by centrifugation, and is washed with N,N-dimethylformamide, acetone and ethanol in turn, and finally the washed product is dried to obtain the product, which is NH2-UIO-66; the amount ratio of the zirconium tetrachloride, 2-amino terephthalic acid, N,N-dimethylformamide and formic acid is 1 mmol: 1 mmol: 100 mL: 4.3 mL; Step 2: synthesis of the hydrophobic porous liquid photocatalyst: NH2-UIO-66 and PDMS prepared in step 1 are respectively dissolved in a mixture of acetone and 2-butanone, and a NH2-UIO-66 suspension and a PDMS solution are obtained by ultrasonic treatment; then, the NH2-UIO-66 suspension is added to the PDMS solution to obtain a mixed solution, wherein the amount ratio of NH2-UIO-66, PDMS, acetone and 2-butanone is 0.2 g: 1.2 g: 40 mL: 0.4 mL; and the obtained mixed solution is stirred and reacted, and then the solvent is evaporated by oil bath, the temperature of oil bath evaporation is 70℃, and the evaporation time is 4-8 h; and the obtained solution after evaporation is vacuum dried, and the product obtained after drying is the hydrophobic porous liquid photocatalyst, which is denoted as NH2-UIO-66 PL; the melting temperature of the hydrophobic porous liquid photocatalyst is -94℃, and it has liquid fluidity at room temperature.

2. Use of the hydrophobic porous liquid photocatalyst according to claim 1 for photocatalytic reduction of CO2, characterized in that, In step 1, the ultrasonic treatment time is 30 min; and the reaction temperature under certain conditions is 120℃, and the reaction time is 12 h.

3. Use of the hydrophobic porous liquid photocatalyst according to claim 1 for photocatalytic reduction of CO2, characterized in that, In step 1, the drying is vacuum drying, the temperature is 150℃, and the drying time is 12 h.

4. Use of the hydrophobic porous liquid photocatalyst according to claim 1 for photocatalytic reduction of CO2, characterized in that, In step 2, the ultrasonic treatment time is 10 min; and the stirring reaction temperature is 40℃, and the reaction time is 20 h.

5. Use of the hydrophobic porous liquid photocatalyst according to claim 1 for photocatalytic reduction of CO2, characterized in that, In step 2, the vacuum drying temperature is 60℃, and the drying time is 24 h.

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