A copper-based MOF photocatalyst, a preparation method and application thereof

Abstract

This invention discloses a copper-based MOF photocatalyst, its preparation method, and its application, belonging to the field of catalyst preparation. This invention pertains to the synthesis of copper-based MOF compounds constructed using defect engineering strategies and their application in photocatalysis to directly convert carbon dioxide into the multi-carbon product acetone. Specifically, it relates to the preparation and application of copper-based MOF composite materials with specific triatomic sites (NH2-Cu-NH2) for the direct conversion of carbon dioxide into the high-value C3 product acetone under visible light irradiation at room temperature.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation, specifically to the synthesis of copper-based MOF compounds constructed using defect engineering strategies and their use in photocatalysis to selectively convert carbon dioxide into acetone. It relates to the preparation and application of copper-based MOF photocatalysts for the direct conversion of carbon dioxide into the high-value C3 product acetone under visible light irradiation at room temperature, as well as the preparation and application of copper-based MOF photocatalysts with special triatomic sites NH2-Cu-NH2. Background Technology

[0002] Photocatalytic water splitting and carbon dioxide reduction into chemical feedstocks or value-added fuels, by mimicking the natural process of photosynthesis, is a promising technology for addressing global energy demand and environmental issues. Photocatalytic reduction of CO2 to C 2+ The product achieves efficient CO2 conversion and utilization, while providing a new pathway for the synthesis of high-value-added hydrocarbons. Metal-organic frameworks (MOFs) have attracted significant research interest due to their large specific surface area, high porosity, tunable structure, and uniformly dispersed active sites, and are widely used as platforms for the synthesis or post-synthesis strategies of immobilized catalyst composites for photocatalysis and electrocatalysis. However, the photo-driven water splitting and CO2 reduction products of MOF catalysts are mainly limited to CO from two-electron reduction and further reduced C1 products, such as methane or methanol. Studies have shown that copper-based catalysts can electrocatalyze the reduction of CO2 to produce multi-carbon products; however, these strategies rarely achieve efficient C1 formation in photocatalytic systems. 2+ Product. Due to C 3+ The formation of the product is a thermodynamically difficult and kinetically slow process involving multiple electron transfers and multiple C-couplings. Selective photoreduction of CO2 to target C3 products remains an important but challenging task. Recently, an asymmetric M1-O-M2 triatomic site confined in amorphous materials has been reported to promote C-coupling and utilize photoinduced heat to increase molecular thermal vibrations, accelerating the reduction of CO2 to C2 fuel. Based on this, we propose that introducing three synergistic interactions around a metal-organic photocatalytic system to mitigate the harmful dipole-dipole repulsion between adjacent C1 intermediates coupled with C-coupling will selectively generate specific C3 products.

[0003] Since amino groups are excellent at capturing CO2 and firmly immobilizing reduction intermediates during CO2 reduction, we envision utilizing the synergistic effect of amino groups and copper sites to form NH2-Cu-NH2 catalytic sites for photocatalytic CO2 reduction, potentially reducing CO2 entirely to C3 products. This invention successfully introduces copper sites into the defective UiO-66-NH2 linker node through a defective engineering strategy, forming a unique NH2-Cu-NH2 catalytic site for the photocatalytic selective decomposition of H2O to O2 and the reduction of carbon dioxide to acetone. The Cu in the well-modified CuN2O2 unit... 2+ The site serves as a trapping site, capturing electrons through effective photoinduced electron-hole separation to form active Cu. I Sites are used for CO2 reduction, while in the MOF framework, photogenerated holes are used for water oxidation.

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies by introducing CuN2O2 active sites into a defective UiO-66-NH2 metal-organic framework, thereby combining Cu ions with the defective MOF and ultimately synthesizing a copper-based MOF photocatalyst with three atomic sites NH2-Cu-NH2. Subsequently, using the copper-based MOF as a photocatalyst, photocatalytic oxidation of H2O to O2 was achieved in a heterogeneous catalytic system, and carbon dioxide was selectively reduced to the C3 product acetone. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an effective defect engineering construction strategy. Cu ions are introduced into the defective UiO-66-NH2 metal-organic framework through acid etching and solvothermal methods, yielding a copper-based MOF photocatalyst with three atomic sites: NH2-Cu-NH2. Subsequently, using the copper-based MOF as a photocatalyst, under irradiation with a 300W xenon lamp (≥420nm filter), the selective reduction of carbon dioxide to multi-carbon products is efficiently achieved. The method of this invention is simple and easy to implement, with mild reaction conditions. The prepared copper-based MOF photocatalyst exhibits high photocatalytic oxidation of water molecules and reduction of carbon dioxide, realizing true "artificial photosynthesis." The catalyst is recyclable and can complete the photocatalytic oxidation of H2O to O2 in a heterogeneous catalytic system, while simultaneously efficiently and selectively reducing carbon dioxide to the C3 product acetone.

[0006] The technical solution of this invention:

[0007] This invention provides a method for preparing a copper-based MOF photocatalyst, comprising the following steps:

[0008] Step 1: Preparation of UiO-66-NH2

[0009] ZrCl4 and 2-aminoterephthalic acid were dissolved in DMF solution. After the solution became clear and transparent, acetic acid was added. The mixture was then transferred to a high-pressure reactor and heated to a high temperature until a precipitate formed. After cooling naturally to room temperature, the precipitate was collected by centrifugation, washed with an organic solvent, and dried under vacuum until all the organic solvent had evaporated, yielding a milky white precipitate of UiO-66-NH2.

[0010] Furthermore, in step one, the mass concentration of ZrCl4 in DMF is 0.35–0.65 mg / mL, and the mass concentration of 2-aminoterephthalic acid in DMF is 0.25–0.55 mg / mL;

[0011] Furthermore, in step one, the volume ratio of acetic acid to DMF is 1 / 10 to 1 / 5.

[0012] Furthermore, in step one, the temperature of the high-temperature heating reaction is 100-120°C, and the high-temperature heating reaction time is 12-72 hours.

[0013] Furthermore, in steps one and two, the organic solvent is ethanol, methanol, or acetonitrile.

[0014] Step 2: Preparation of d-MOF

[0015] The synthesized milky white UiO-66-NH2 precipitate was dispersed in deionized water and sonicated until the powder was completely and evenly dispersed. Hydrofluoric acid was added and stirred until the solution was nearly white and transparent. The solution was collected by centrifugation, washed with organic solvent, and vacuum dried until the solvent was completely evaporated to obtain the dried defective UiO-66-NH2 precipitate, denoted as d-MOF.

[0016] Furthermore, in step two, the mass concentration of the UiO-66-NH2 precipitate dispersed in deionized water is 0.5–2 mg / mL.

[0017] Furthermore, in step two, the hydrofluoric acid is commercially available, and its mass percentage in the aqueous solution is 40%–50%; the volume ratio of hydrofluoric acid to deionized water is 1 / 4000–1 / 1200. The reaction stirring time is 3–6 hours.

[0018] Step 3: Preparation of Cu-MOF compounds

[0019] d-MOF and anhydrous CuCl2 were dispersed in a methanol solution and sonicated until CuCl2 dissolved and d-MOF powder was evenly dispersed. The mixed solution was then transferred to a high-pressure reactor and heated at high temperature until the white precipitate turned into a yellow precipitate. The precipitate was then allowed to cool naturally to room temperature, collected by centrifugation, washed with an organic solvent until the washing solution was colorless and transparent, and vacuum dried until all the solvent evaporated to obtain a copper-based MOF photocatalyst with special three-atom NH2-Cu-NH2 sites.

[0020] Furthermore, in step three, the mass ratio of d-MOF to anhydrous CuCl2 is 1 / 20 to 1 / 5; the mass concentration of CuCl2 in methanol is 5 to 100 mg / mL.

[0021] Furthermore, in step three, the temperature of the high-temperature heating reaction is 90℃~110℃; the high-temperature heating reaction time is 12h~50h.

[0022] Furthermore, in step three, the organic solvent is ethanol, methanol, or acetonitrile.

[0023] The present invention also provides a copper-based MOF photocatalyst prepared by the above method.

[0024] The present invention also provides an application of a copper-based MOF photocatalyst, wherein the copper-based MOF photocatalyst is used for photocatalytic conversion of CO2 into acetone.

[0025] Copper-based MOF photocatalysts, using carbon dioxide gas as a substrate, DMF and water as solvent and proton source respectively, are used for water splitting and photocatalytic CO2 reduction under visible light irradiation, and can ultimately reduce carbon dioxide to the C3 product acetone with high selectivity.

[0026] Specifically: A copper-based MOF photocatalyst was dispersed in a transparent reactor containing DMF and deionized water. High-purity CO2 gas was bubbled through a suspension for at least 10 minutes before irradiation. At room temperature, a xenon lamp and a ≥420nm cutoff filter were used as the visible light source to carry out the photocatalytic CO2RR reaction in a closed reaction system until the C3 product acetone was produced. The liquid product was monitored using a gas chromatograph detector. Further analysis was performed using H... 1 NMR and GC-MS were used to identify and quantify the acetone products.

[0027] Furthermore, the copper-based MOF photocatalyst is dispersed in a solution containing DMF and deionized water at a mass concentration of 0.5–1.5 mg / mL; the volume ratio of deionized water to DMF is 1 / 6–1 / 2.

[0028] Furthermore, the transparent reactor is made of quartz glass.

[0029] Furthermore, the xenon lamp is a commercially available standard 300W xenon lamp. During the reaction process, the photocurrent of the xenon lamp is 10–19 A.

[0030] Furthermore, the photocatalytic reaction time is 20h to 72h.

[0031] The beneficial effects of this invention are:

[0032] (1) This invention prepared a copper-based MOF photocatalyst with special three-atom NH2-Cu-NH2 sites through a defect engineering construction strategy. Through continuous photoelectron excitation and transfer, the synergistic effect of photocatalysis of CO2 and water splitting by the copper-based MOF photocatalyst was realized, and carbon dioxide was successfully converted into acetone.

[0033] (2) This invention uses copper-based MOF as a photocatalyst and successfully realizes the full reaction of water splitting and photocatalytic CO2 reduction under visible light irradiation, and finally can selectively reduce carbon dioxide to acetone, a high-value multi-carbon product. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a copper-based MOF photocatalyst and its photocatalytic reduction of CO2 to acetone.

[0035] Figure 2 The X-ray powder diffraction patterns are those of the UiO-66-NH2, d-MOF and copper-based MOF photocatalysts prepared in steps one, two and three of Example 1.

[0036] Figure 3 These are aberration-corrected high-angle annular dark-field scanning transmission electron images and corresponding elemental distribution maps of the copper-based MOF photocatalyst prepared in step three of Example 1, where a) and b) are aberration-corrected high-angle annular dark-field scanning transmission electron images of the copper-based MOF photocatalyst, and c) is the corresponding elemental distribution map of the copper-based MOF photocatalyst.

[0037] Figure 4 The images show the CO2 adsorption isotherm and corresponding pore size distribution of the copper-based MOF photocatalyst prepared in step three of Example 1.

[0038] Figure 5 These are the synchrotron radiation spectrum fitting curves of Cu element in the copper-based MOF photocatalyst prepared in step three of Example 1, where a) X-ray absorption near-edge structure spectra of Cu-MOF and standard samples; b) X-ray absorption fine structure spectra of Cu-MOF and standard samples; and c) X-ray absorption fine structure fitting curve of Cu-MOF.

[0039] Figure 6These are the electron paramagnetic resonance spectra of the copper-based MOF photocatalyst prepared in step three of Example 1 under different conditions.

[0040] Figure 7(a) shows the 1H NMR spectrum of the copper-based MOF photocatalyst used for the reduction of carbon dioxide to acetone.

[0041] Figure 7(b) shows the carbon NMR spectrum of the copper-based MOF photocatalyst used for the reduction of carbon dioxide to acetone.

[0042] Figure 8 This is a gas chromatography-mass spectrometry (GC-MS) chromatogram of the acetone product prepared by carbon dioxide reduction using the copper-based MOF photocatalyst in step 4 of Example. Detailed Implementation

[0043] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0044] Example 1:

[0045] Step 1: Dissolve ZrCl4 (0.053 g) and 2-aminoterephthalic acid (0.041 g) in 10 mL of DMF solution. After the solution becomes clear and transparent, add 1.2 mL of acetic acid. Then transfer the mixture to a high-pressure reactor and heat at 120 °C for 24 hours. Allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash three times with ethanol, and dry under vacuum at 80 °C for 12 hours to obtain a milky white precipitate of UiO-66-NH2.

[0046] Step 2: Subsequently, 20 mg of the synthesized UiO-66-NH2 precipitate was dispersed in 20 mL of deionized water and sonicated for 30 min until the powder was completely and evenly dispersed. After dispersion, 10 μL of hydrofluoric acid (40%) was added and stirred for 4 h until the solution was nearly white and transparent. The solution was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C for 12 h to obtain the UiO-66-NH2 precipitate with defective structure, denoted as d-MOF.

[0047] Step 3: Take 50 mg of the synthesized d-MOF powder and disperse it in 10 mL of methanol solution containing anhydrous CuCl2 (0.5 g). Sonicate for 30 min until the powder is completely and evenly dispersed. Then transfer the mixed solution to a high-pressure reactor and heat at 100 °C for 24 h. Allow it to cool naturally to room temperature and collect it by centrifugation to obtain the copper-based MOF photocatalyst with special three-atom NH2-Cu-NH2 sites.

[0048] Example 2:

[0049] Step 1: Dissolve ZrCl4 (0.058 g) and 2-aminoterephthalic acid (0.045 g) in 10 mL of DMF solution. After the solution becomes clear and transparent, add 1.5 mL of acetic acid. Then transfer the mixture to a high-pressure reactor and heat at 120 °C for 36 hours. Allow it to cool naturally to room temperature, collect by centrifugation, wash three times with ethanol, and dry under vacuum at 80 °C for 24 hours to obtain a milky white precipitate of UiO-66-NH2.

[0050] Step 2: Subsequently, 30 mg of the synthesized milky white UiO-66-NH2 precipitate was dispersed in 20 mL of deionized water and sonicated for 20 min until the powder was completely and evenly dispersed. After dispersion, 15 μL of hydrofluoric acid (40%) was added and stirred for 5.5 h until the solution was nearly white and transparent. The solution was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C for 12 h to obtain the UiO-66-NH2 precipitate with defective structure, denoted as d-MOF.

[0051] Step 3: Take 55 mg of the synthesized d-MOF powder and disperse it in 10 mL of methanol solution containing anhydrous CuCl2 (0.6 g). Sonicate for 40 min until the powder is completely and evenly dispersed. Then transfer the mixed solution to a high-pressure reactor and heat at 90 °C for 30 h. After cooling naturally to room temperature, collect the copper-based MOF photocatalyst with special three-atom NH2-Cu-NH2 sites by centrifugation.

[0052] Example 3:

[0053] Step 1: Dissolve ZrCl4 (0.06 g) and 2-aminoterephthalic acid (0.05 g) in 10 mL of DMF solution. After the solution becomes clear and transparent, add 1.8 mL of acetic acid. Then transfer the mixture to a high-pressure reactor and heat at 110 °C for 48 hours. Allow it to cool naturally to room temperature, collect by centrifugation, wash three times with ethanol, and dry under vacuum at 80 °C for 12 hours to obtain a milky white precipitate of UiO-66-NH2.

[0054] Step 2: Subsequently, 23 mg of the synthesized milky white UiO-66-NH2 precipitate was dispersed in 20 mL of deionized water and sonicated for 60 min until the powder was completely and evenly dispersed. After dispersion, 8 μL of hydrofluoric acid (40%) was added and stirred for 5 h until the solution was nearly white and transparent. The solution was collected by centrifugation, washed three times with ethanol, and dried under vacuum at 80 °C for 12 h to obtain a UiO-66-NH2 precipitate with a defective structure, denoted as d-MOF.

[0055] Step 3: Take 60 mg of the synthesized d-MOF powder and disperse it in 10 mL of methanol solution containing anhydrous CuCl2 (0.8 g). Sonicate for 20 min until the powder is completely and evenly dispersed. Then transfer the mixed solution to a high-pressure reactor and heat at 100 °C for 20 h. After cooling naturally to room temperature, collect the copper-based MOF photocatalyst with special three-atom NH2-Cu-NH2 sites by centrifugation.

[0056] Example 4:

[0057] Eight mg of the copper-based MOF photocatalyst obtained in Example 1 was dispersed in a quartz glass reactor containing DMF (6 mL) and deionized water (2 mL). The photocatalytic carbon dioxide reduction reaction was carried out in a closed reaction system at room temperature using a 300 W xenon lamp (adjusted to a photocurrent of 18 A) and a ≥420 nm cutoff filter as the visible light source for 24 h. High-purity CO2 (99.999%) gas was bubbled through a suspension for at least 10 minutes before irradiation. Liquid products were monitored using a TRACE1300 gas chromatograph (Thermo Scientific) with an FID detector. Further analysis was performed using H... 1 NMR and GC-MS were used to identify and quantify the acetone products.

Claims

1. An application of a copper-based MOF photocatalyst, characterized in that, The copper-based MOF photocatalyst is used for the photocatalytic conversion of CO2 to acetone: The copper-based MOF photocatalyst acts as a photocatalyst, using carbon dioxide gas as the substrate, DMF and water as the solvent and proton source, respectively. Under visible light irradiation, it is used for water splitting and photocatalytic CO2 reduction, ultimately selectively reducing carbon dioxide to the C3 product acetone. The preparation method of the copper-based MOF photocatalyst is as follows: Step 1: Preparation of UiO-66-NH2 ZrCl4 and 2-aminoterephthalic acid were dissolved in DMF solution. After the solution became clear and transparent, acetic acid was added. The mixture was then transferred to a high-pressure reactor and heated to a high temperature until a precipitate formed. The mixture was allowed to cool naturally to room temperature, collected by centrifugation, washed with an organic solvent, and vacuum dried until all the organic solvent had evaporated, yielding a milky white precipitate of UiO-66-NH2. Step 2: Preparation of d-MOF The synthesized milky white UiO-66-NH2 precipitate was dispersed in deionized water and ultrasonically treated until the powder was completely and evenly dispersed. Hydrofluoric acid was added and stirred until the solution was nearly white and transparent. The solution was collected by centrifugation, washed with organic solvent, and vacuum dried until the solvent was completely evaporated to obtain the dried defective UiO-66-NH2 precipitate, denoted as d-MOF. Step 3: Preparation of Cu-MOF compounds d-MOF and anhydrous CuCl2 were dispersed in a methanol solution and sonicated until CuCl2 dissolved and d-MOF powder was evenly dispersed. The mixed solution was then transferred to a high-pressure reactor and heated at high temperature until the white precipitate turned into a yellow precipitate. After natural cooling to room temperature, the precipitate was collected by centrifugation and washed with an organic solvent until the washing solution was colorless and transparent. The solution was then vacuum dried until all the solvent evaporated to obtain a copper-based MOF photocatalyst with special three-atom NH2-Cu-NH2 sites. The high-temperature reaction temperature was 90℃~110℃ and the high-temperature reaction time was 12 h~50 h.

2. The application of the copper-based MOF photocatalyst according to claim 1, characterized in that, In step one, the mass concentration of ZrCl4 in DMF is 0.35 ~ 0.65 mg / mL, the mass concentration of 2-aminoterephthalic acid in DMF is 0.25 ~ 0.55 mg / mL, and the volume ratio of acetic acid to DMF is 1 / 10 ~ 1 / 5.

3. The application of the copper-based MOF photocatalyst according to claim 1, characterized in that, In step one, the high-temperature heating reaction temperature is 100~120℃, and the high-temperature heating reaction time is 12 h~72 h; in steps one, two, and three, the organic solvent is ethanol, methanol, or acetonitrile.

4. The application of the copper-based MOF photocatalyst according to claim 1, characterized in that, In step two, the mass concentration of UiO-66-NH2 precipitate dispersed in deionized water is 0.5 ~ 2 mg / mL; the volume ratio of hydrofluoric acid to deionized water is 1 / 4000 ~ 1 / 1200; and the reaction stirring time is 3 h ~ 6 h.

5. The application of the copper-based MOF photocatalyst according to claim 1, characterized in that, In step three, the mass ratio of d-MOF to anhydrous CuCl2 is 1 / 20 to 1 / 5; the mass concentration of CuCl2 in methanol is 5 to 100 mg / mL.

6. The application according to claim 1, characterized in that, Specifically, the process involves dispersing a copper-based MOF photocatalyst in a transparent reactor containing DMF and deionized water; bubbling high-purity CO2 gas through a suspension for at least 10 minutes before irradiation; conducting a photocatalytic CO2RR reaction in a closed reaction system at room temperature using a xenon lamp and a ≥420 nm cutoff filter as the visible light source, until the C3 product acetone is produced; monitoring the liquid product using a gas chromatograph detector; and further processing using H... 1 NMR and GC-MS were used to identify and quantify the acetone products.

7. The application according to claim 6, characterized in that, The volume ratio of deionized water to DMF is 1 / 6 to 1 / 2; the xenon lamp is a commercially available standard 300W xenon lamp; during the reaction, the photocurrent of the xenon lamp is 10 to 19 A; the photocatalytic reaction time is 20 to 72 hours.

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