MOF-based catalyst with Cudelta+-O2--Zr4 + interfacial active center as well as preparation method and application of MOF-based catalyst

Abstract

The invention relates to an MOF-based catalyst with a-O2--Zr < 4 + > interfacial active center and a preparation method and application thereof.The preparation method comprises the steps that a zirconium source, an organic ligand and a monocarboxylic acid regulator are dissolved in an organic solvent, mixed to be uniform and then transferred into a reaction kettle to be subjected to a solvothermal reaction; after the reaction is finished, washing and drying to obtain UiO-xAA carriers with different ligand deficiency defect concentrations; dispersing the carrier in a copper salt solution, and carrying out impregnation adsorption; then, drying the solid adsorbed with the copper ions, carrying out calcination treatment, and further carrying out reduction treatment in a reducing atmosphere; the problems that in the prior art, the Cu active center electronic state is difficult to regulate and control, interfacial active sites are insufficient, and the structure-function relationship is difficult to establish are effectively solved. The catalyst with a unique confinement effect and an interface electronic state is prepared by utilizing an MOF defect engineering strategy, so that effective regulation and control on an active center electronic state and a coordination structure are realized; in a reaction for preparing methanol through CO2 hydrogenation, the catalyst shows significantly improved methanol selectivity, space-time yield and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a catalyst with... -O 2- -Zr 4+ MOF-based catalysts with interfacial active centers, their preparation methods, and applications, particularly a catalyst for the hydrogenation of carbon dioxide to methanol. -O 2- -Zr 4+ Metal-organic framework supported copper-based catalysts with specific interfacial active centers, their preparation methods, and applications. Background Technology

[0002] The increasingly severe climate crisis has made carbon dioxide emission reduction and resource utilization a global priority. Utilizing renewable energy to convert carbon dioxide into value-added chemicals is not only a promising pathway for carbon dioxide utilization but also a key strategy for achieving high-value carbon sequestration. Among various pathways, the catalytic conversion of carbon dioxide into methanol using green hydrogen is a highly promising carbon capture, utilization, and storage technology. Methanol can be used not only as a fuel and hydrogen storage carrier but also as a key C1 platform molecule in the synthesis of other high-value chemicals (such as olefins and gasoline).

[0003] Under reaction conditions of 300 °C and 5 MPa, due to competing reactions, the selectivity of methanol relying solely on thermodynamic effects (without catalysis) is typically only 20-30%. Therefore, constructing a highly selective catalytic system is crucial for achieving efficient methanol synthesis. Currently, high-performance catalysts developed for the conversion of carbon dioxide to methanol mainly include copper-based, indium oxide-based, solid solution, noble metal, and alloy catalysts. Among them, copper-based catalysts (such as Cu / ZnO / Al2O3 and Cu / ZrO2) are considered the most promising candidates for industrialization due to their low cost and relatively high activity. Numerous studies have shown that the interface formed between the metal and the oxide support (such as the Cu-ZrO2 interface) is a key active region for catalytic CO2 hydrogenation. Electron metal-support interactions can regulate the electronic state of active centers (such as Cu), thereby affecting catalytic performance. However, the interface structure of traditional supported catalysts is complex and influenced by factors such as support morphology, crystallinity, and defect chemistry, making precise design and control difficult, resulting in a lack of understanding of the structure-performance relationship of the interfacial active centers. For example, the methanol selectivity of traditional supported Cu / ZrO2-based catalysts is usually around 50%, and they are easily deactivated by the product H2O.

[0004] In recent years, metal-organic frameworks (MOFs) have been used as supports to confine metal nanoparticles due to their well-defined structures, tunable pores, and ease of functionalization. Zr-based MOFs, in particular, such as UiO-66, have been used to construct confined metal-supported catalysts for CO2 hydrogenation due to their excellent thermochemical stability. Existing reports on Cu@MOF catalysts, while recognizing the importance of defects and active interfaces, mostly remain at the level of phenomenological description; the underlying nature of the active sites remains unclear, and the methanol space-time yields of these catalysts are concentrated around 200 mg·g⁻¹. -1 ·h -1 There is still considerable room for improvement. Furthermore, there is a lack of quantitative research on how inherent defects in the MOF framework systematically regulate the formation of active interfaces, and even less in-depth understanding of how defects induce interfacial electron transfer and their decisive role in catalytic activity.

[0005] To address the aforementioned shortcomings, this invention proposes a catalyst-oriented construction strategy based on MOF defect engineering and strong interfacial electron interactions. This method uses UiO-66 with tunable defect concentration as a support, precisely anchoring Cu species and inducing their formation with the support. -O 2- -Zr 4+ The interfacial active centers enable effective control over the electronic states and coordination structures of the active centers. Compared with supported catalysts prepared by traditional impregnation or deposition methods, this invention combines MOF defect engineering with strong metal-support interactions, providing a new approach for the design of highly efficient CO2 hydrogenation catalysts, exhibiting superior activity, selectivity, and stability in methanol synthesis reactions. Summary of the Invention

[0006] In view of this, the present invention addresses the problems of complex and difficult-to-control interfacial structures and easy deactivation in traditional copper-based catalysts, and the lack of in-depth elucidation of the mechanisms by which emerging MOF-based catalysts quantitatively regulate the formation of active interfaces and induce electron transfer due to framework defects, resulting in unclear active sites and ambiguous structure-activity relationships. Therefore, the present invention provides a method with… -O 2- -Zr 4+ MOF-based catalysts with interfacial active centers, their preparation methods, and applications are described. A simple MOF defect engineering strategy is employed to prepare a catalyst using confined encapsulation. -O 2- -Zr 4+ The Cu@UiO-66 catalyst, with its interface as the active center, exhibits an electron-deficient state due to interfacial electronic effects. Site generation. This catalyst should effectively solve the problems of difficult control of the electronic state of Cu active center, insufficient interfacial active sites, and difficulty in establishing structure-activity relationship in the existing technology, so as to achieve efficient activation and high-selectivity conversion of CO2, thereby obtaining methanol space-time yield and long-term stability far exceeding those of traditional supported catalysts.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A kind of -O 2- -Zr 4+ The preparation method of MOF-based catalysts with interfacial active centers includes the following steps:

[0009] S1. Synthesis of defective UiO-xAA support: Accurately weigh the zirconium source zirconium tetrachloride (ZrCl4) and the organic ligand 1,4-terephthalic acid (H2BDC); use acetic acid (AA) in an amount of 0-100 equivalents of the zirconium source as a structure and defect modifier. Add the above three components sequentially to an appropriate amount of organic solvent N,N-dimethylformamide (DMF), mix, and then stir on a magnetic stirrer at room temperature for 30-60 min until all solids are completely dissolved to form a clear and transparent homogeneous solution. The competitive coordination of acetic acid is the key to the formation of defects. It can partially replace the BDC ligand and bind to the Zr cluster, and is removed in subsequent washing, leaving vacancies.

[0010] A clear, homogeneous solution was transferred to a reaction vessel, which was then placed in an oven and heated to 120 °C. The reaction was maintained at this temperature for 24 h. During this process, ZrCl4 and H2BDC underwent coordination self-assembly. The competitive action of acetic acid led to the loss of some BDC ligands, resulting in crystals with a specific defect concentration.

[0011] After the reaction, the mixture was naturally cooled to room temperature, washed with DMF and anhydrous ethanol, and dried. The product was collected by centrifugation, washed three times with fresh DMF to remove unreacted organic matter and free acetic acid, and then washed three times with anhydrous ethanol to replace DMF molecules in the pores and facilitate drying. Finally, porous defect-type supports UiO-xAA with different missing ligand defect concentrations were obtained. The zirconium source can also be zirconium oxychloride (ZrOCl2), and the organic ligands can be ligands with functional groups such as -OMe, -NH2, -F, -SO3H, -OH, -Br, and -CH3. The monocarboxylic acid regulator can also be formic acid, trifluoroacetic acid, or hydrochloric acid. The prepared UiO-xAA series of zirconium-based metal-organic framework materials can be selected from UiO-66, UiO-67, UiO-68, or MOF-808.

[0012] S2. Loading of Cu nanoparticles: Weigh an appropriate amount of copper nitrate (Cu(NO3)2·3H2O) and dissolve it in anhydrous ethanol to prepare a solution of a certain concentration. The volume of the solution must be sufficient to submerge the support, and the mass of the solute must be accurately calculated to ensure that the theoretical Cu loading in the final catalyst is 15 wt.%. Weigh the UiO-xAA support obtained in step S1 and disperse it in the above copper nitrate ethanol solution. Stir magnetically at room temperature for 24 h. During this period, the coordinatingly unsaturated Zr sites (defect sites) on the support surface will specifically adsorb Cu through electrostatic or coordination interactions. 2+ Ions enable preferential enrichment of copper species at defects.

[0013] The stirred suspension was transferred to a rotary evaporator and subjected to reduced pressure rotary evaporation at a water bath temperature of 40–60 °C for 1–2 h to slowly remove the ethanol solvent. This step prevents the copper species from migrating and agglomerating due to rapid solvent evaporation, ensuring their uniform distribution within the carrier pores. The resulting blue, thick slurry was then transferred to a vacuum drying oven and dried at 80 °C for 8–12 h to obtain a solid sample loaded with the copper precursor.

[0014] The vacuum-dried sample was placed in a tube furnace and calcined at 300 °C for 2 h under a nitrogen atmosphere at a flow rate of 50-100 mL / min. This process decomposes copper nitrate into copper oxide (CuO), while removing residual organic solvents and nitrate anions, allowing copper species to exist stably in oxide form on the surface of the support and within the pores.

[0015] The calcined sample (in this case, CuO / UiO-6AA) is placed in a fixed-bed reactor or reduction furnace. Pure hydrogen (H2) or a 5% H2 / Ar mixture is introduced, and the temperature is raised to 250 °C at a rate of 2~5 °C / min. The sample is then kept at this temperature for 2 hours for reduction. After reduction, the sample is cooled to room temperature under the protection of an inert gas (such as N2 or Ar) to obtain the Cu@UiO-xAA catalyst, which can be used directly for catalytic reactions or stored in an inert atmosphere for later use.

[0016] Mechanism Explanation: During the reduction process, CuO is reduced to metallic Cu nanoparticles. Due to the strong anchoring effect of the defect sites introduced in step S1, the newly generated Cu nanoparticles cannot migrate and aggregate freely, but are firmly fixed at the defect sites. At this time, Cu atoms undergo strong electronic interactions with the exposed Zr-O clusters on the support, and electrons transfer from Cu to the electron-deficient Zr sites, forming electron-deficient copper species (…). ), and eventually build a stable -O 2- -Zr 4+ Heterogeneous interface active center.

[0017] Furthermore, in step S1, the molar ratio of acetic acid to zirconium source is 36:1 to obtain the optimal defect concentration (approximately 1.08 / Zr6).

[0018] The preparation method described above yields a product with... -O 2- -Zr 4+ The MOF-based catalyst with an interfacial active center contains a specific concentration of "ligand-deficient" UiO-xAA support, with the defect located in the Zr6 oxygen cluster ([Zr6O4(OH)4)). 12+ On the Zr cluster, the 1,4-terephthalic acid ligand that should have coordinated with the Zr cluster is missing, thus exposing the coordination-unsaturated Zr sites; the copper nanoparticles are encapsulated in the defective UiO-xAA support and are preferentially anchored to the coordination-unsaturated Zr sites through chemical bonds (Zr-O-Cu), thus forming a tight Cu-(O)-Zr heterointerface with the Zr6 oxygen cluster.

[0019] The having -O 2- -Zr 4+ Application of MOF-based catalysts with interfacial active centers in the CO2 hydrogenation to methanol reaction.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The invention disclosed herein has -O 2- -Zr 4+ MOF-based catalysts with interfacial active centers have been clearly proposed and successfully constructed. -O 2- -Zr 4+ "Interfacial active center". Multiple characterization methods (Cu LMM, H2-TPR) confirmed that this center possesses a unique electron-deficient Cu structure. It has an extremely strong adsorption and activation ability for CO2 molecules, which is the fundamental reason for the improved catalytic performance.

[0022] 2. The invention disclosed has -O 2- -Zr 4+ MOF-based catalysts with interfacial active centers benefit from unique -O 2- -Zr 4+ The optimal catalyst of this invention (Cu@UiO-36AA) at the interfacial active site exhibits a methanol STY that is 2.4 times that of the defect-free comparative catalyst (Cu@UiO-36AA-PSE) and 5.1 times that of the conventional Cu / ZrO2 catalyst, demonstrating extremely outstanding performance advantages. This was further demonstrated at 260 °C, 3.2 MPa, and 24000 mL·g.-1 ·h -1 Under these conditions, the space-time yield of methanol reached as high as 289.94%. The methanol selectivity reached 72%.

[0023] 3. The invention disclosed has -O 2- -Zr 4+ The MOF-based catalyst with interfacial active center showed no significant activity decay or selectivity decrease during a continuous reaction test of 110 h, demonstrating excellent operational stability and promising prospects for industrial application.

[0024] 4. The invention disclosed has -O 2- -Zr 4+ The MOF-based catalyst with interfacial active centers utilizes a monocarboxylic acid modulation method to synthesize MOF defect supports, a simple process easily scaled up. The defect concentration can be precisely and continuously controlled by simply adjusting the amount of acid, thereby achieving the "tailoring" of interfacial electronic states and optimizing catalytic performance, providing a novel approach for the design of high-performance catalysts. Compared with traditional supported Cu-based catalysts, this invention utilizes a MOF defect engineering strategy to prepare a catalyst with unique confinement effects and interfacial electronic states, achieving effective control over the electronic states and coordination structures of the active centers; in the CO2 hydrogenation to methanol reaction, it exhibits significantly improved methanol selectivity, space-time yield, and long-term operational stability.

[0025] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0027] Figure 1 Thermogravimetric analysis curves of different samples of the present invention are used for quantitative calculation of defect concentration comparison.

[0028] Figure 2 Transmission electron microscopy images and particle size distribution histograms of the Cu@UiO-36AA catalyst prepared in Example 4;

[0029] Figure 3 High-resolution transmission electron microscopy image of the Cu@UiO-36AA catalyst prepared in Example 4;

[0030] Figure 4 The Cu LMM spectra of Example 4 and Comparative Example 1 of this invention are shown below;

[0031] Figure 5 The H2-TPR spectra of Example 4 and Comparative Example 1 of the present invention are shown. Detailed Implementation

[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0033] The having -O 2- -Zr 4+ The preparation method of MOF-based catalysts with interfacial active centers includes the following steps:

[0034] S1. Synthesis of defective UiO-66 supports (adjustment of defect concentration): A zirconium source (e.g., ZrCl4), an organic ligand (1,4-terephthalic acid), and a monocarboxylic acid modifier (e.g., acetic acid) are dissolved in an organic solvent (e.g., DMF), mixed thoroughly, and then transferred to a reactor for a solvothermal reaction. After the reaction, the mixture is washed and dried to obtain UiO-xAA supports with different ligand defect concentrations (x is the acetic acid equivalent).

[0035] By varying the amount of the monocarboxylic acid regulator (acetic acid), the concentration of defects in the product can be precisely controlled. For example, the molar ratio of acetic acid to the zirconium source can be adjusted within the range of (0~100):1 to achieve control over the defect concentration from low to high. Preferably, this molar ratio is 36:1 to obtain the optimal defect concentration (approximately 1.08 / Zr6).

[0036] S2. Loading and Interface Construction of Copper Nanoparticles: The defective UiO-xAA support obtained in step S1 was dispersed in a copper salt solution (such as an ethanol solution of Cu(NO3)2) for impregnation and adsorption. Subsequently, the solid with adsorbed copper ions was dried (e.g., by rotary evaporation), calcined, and further reduced in a reducing atmosphere (such as a H2 / Ar mixture).

[0037] During the reduction process, Cu anchored at the defect site 2+ The particles are reduced and grown in situ as Cu nanoparticles. Due to the "anchoring effect" of defect sites, the Cu nanoparticles form strong chemical bonds with Zr6 oxygen clusters, thereby spontaneously constructing the desired Cu-(O)-Zr interface. -O 2--Zr 4+ Active center. The preferred reduction temperature is 250 °C, and the preferred time is 2 h.

[0038] The having -O 2- -Zr 4+ The application of MOF-based catalysts with interfacial active centers in the CO2 hydrogenation to methanol reaction, under the following reaction conditions: reaction temperature 220–300 °C, reaction pressure 3.2 MPa, H2 / CO2 volume ratio 3, and gas hourly space velocity 4000–24000 mL·g. -1 ·h -1 .

[0039] The having -O 2- -Zr 4+ The core structure of MOF-based catalysts with interfacial active centers is characterized by:

[0040] Interface electronic states: Due to the anchoring effect of defect sites, a strong electronic metal-carrier interaction occurs at the Cu-(O)-Zr interface. This interaction leads to charge transfer from Cu nanoparticles to Zr6 oxygen clusters, resulting in an electron-deficient state for copper at the interface (denoted as...). ).

[0041] Active center: the electron-deficient Cu ( ), and oxygen ions (O) that form bonds with it 2- ) and zirconium ions (Zr) in the support 4 + Together they form a whole, namely, the "..." described in this invention. -O 2- -Zr 4+ "Interfacial active center". This center is an effective active site for catalyzing CO2 adsorption, activation, and hydrogenation to methanol.

[0042] Among the preferred technical parameters:

[0043] Defect Concentration: The concentration of the missing ligand defects is 0.75–1.32 missing 1,4-terephthalic acid ligands per Zr6 unit, with a maximum of 1.08 (corresponding to the UiO-36AA sample synthesized via acetic acid regulation). Cu Size and Distribution: The average particle size of the copper nanoparticles is 7.95 ± 0.12 nm, and they are highly dispersed and confined within the pores of the defective UiO-66 support, rather than agglomerating on the external surface. Electronic State Characterization: X-ray photoelectron spectroscopy analysis shows significant charge transfer between the Cu and Zr oxygen clusters in the catalyst, and the Cu LMM Auger electron spectrum of the catalyst indicates that the copper species are in a state of... Mainly. Interface characterization: High-resolution transmission electron microscopy revealed that the Cu(111) crystal plane (lattice spacing 0.208 nm) and the UiO-66(444) crystal plane (lattice spacing 0.298 nm) are adjacent, forming a clear Cu-(O)-Zr interface.

[0044] Example 1: Preparation of Cu@UiO-0AA catalyst

[0045] S1. Synthesis of defective UiO-0AA support: Accurately weigh 1.165 g (5 mmol) of zirconium tetrachloride (ZrCl4) and 0.83 g (5 mmol) of organic ligand 1,4-terephthalic acid (H2BDC); add the above components sequentially to an appropriate amount of organic solvent N,N-dimethylformamide (DMF), mix and stir on a magnetic stirrer at room temperature for 60 min until all solids are completely dissolved to form a clear and transparent homogeneous solution;

[0046] The clear, homogeneous solution was transferred to a reaction vessel, which was then placed in an oven and heated to 120 °C. The reaction was maintained at this temperature for 24 h. After the reaction was completed, the solution was allowed to cool naturally to room temperature, washed with DMF and anhydrous ethanol, dried, and the product was collected by centrifugation, finally yielding the porous defect-type support UiO-0AA.

[0047] S2. Loading of Cu nanoparticles: Weigh an appropriate amount of copper nitrate (Cu(NO3)2·3H2O) and dissolve it in anhydrous ethanol to prepare a solution of a certain concentration. The volume of the solution must be sufficient to submerge the support, and the mass of the solute must be accurately calculated to ensure that the theoretical Cu loading in the final catalyst is 15 wt.%. Weigh the UiO-0AA support obtained in step S1 and disperse it in the above copper nitrate ethanol solution. Stir magnetically for 24 h at room temperature.

[0048] The stirred suspension was transferred to a rotary evaporator and evaporated under reduced pressure in a 60 °C water bath for 2 h to slowly remove the ethanol solvent. The resulting blue, thick slurry was transferred to a vacuum drying oven and dried at 80 °C for 10 h to obtain a solid sample loaded with the copper precursor. The vacuum-dried sample was then placed in a tube furnace and calcined at 300 °C for 2 h under a nitrogen atmosphere at a flow rate of 80 mL / min.

[0049] The calcined sample (in this case, CuO / UiO-0AA) was placed in a fixed-bed reactor or reduction furnace. Pure hydrogen (H2) or a 5% H2 / Ar mixture was introduced, and the temperature was increased to 250 °C at a rate of 5 °C / min. The sample was then reduced at this temperature for 2 hours to obtain the Cu@UiO-6AA catalyst.

[0050] Example 2: Preparation of Cu@UiO-6AA catalyst

[0051] S1. Synthesis of the defective UiO-6AA support: Accurately weigh 1.165 g (5 mmol) of zirconium tetrachloride (ZrCl4) and 0.83 g (5 mmol) of the organic ligand 1,4-terephthalic acid (H2BDC); measure acetic acid (AA) as a structure and defect modifier, using 6 equivalents of the zirconium source, i.e., 30 mmol (approximately 1.7 mL). Add the above components sequentially to an appropriate amount of the organic solvent N,N-dimethylformamide (DMF), mix, and then stir on a magnetic stirrer at room temperature for 60 min until all solids are completely dissolved, forming a clear and transparent homogeneous solution.

[0052] The clear, homogeneous solution was transferred to a reaction vessel, which was then placed in an oven and heated to 120 °C. The reaction was maintained at this temperature for 24 h. After the reaction was completed, the solution was allowed to cool naturally to room temperature, washed with DMF and anhydrous ethanol, dried, and the product was collected by centrifugation, finally yielding the porous defect-type support UiO-6AA.

[0053] S2. Loading of Cu nanoparticles: Weigh an appropriate amount of copper nitrate (Cu(NO3)2·3H2O) and dissolve it in anhydrous ethanol to prepare a solution of a certain concentration. The volume of the solution must be sufficient to submerge the support, and the mass of the solute must be accurately calculated to ensure that the theoretical Cu loading in the final catalyst is 15 wt.%. Weigh the UiO-6AA support obtained in step S1 and disperse it in the above copper nitrate ethanol solution. Stir magnetically for 24 h at room temperature.

[0054] The stirred suspension was transferred to a rotary evaporator and evaporated under reduced pressure in a 60 °C water bath for 2 h to slowly remove the ethanol solvent. The resulting blue, thick slurry was transferred to a vacuum drying oven and dried at 80 °C for 10 h to obtain a solid sample loaded with the copper precursor. The vacuum-dried sample was then placed in a tube furnace and calcined at 300 °C for 2 h under a nitrogen atmosphere at a flow rate of 80 mL / min.

[0055] The calcined sample (in this case, CuO / UiO-6AA) is placed in a fixed-bed reactor or reduction furnace. Pure hydrogen (H2) or a 5% H2 / Ar mixture is introduced, and the temperature is raised to 250 °C at a rate of 5 °C / min. The sample is then kept at this temperature for 2 h for reduction. After reduction, the sample is cooled to room temperature under the protection of an inert gas (such as N2 or Ar) to obtain the Cu@UiO-6AA catalyst, which can be used directly for catalytic reactions or stored in an inert atmosphere for later use.

[0056] Example 3: Preparation of Cu@UiO-12AA catalyst

[0057] The difference between Example 3 and Example 2 is that in step S1, 1.165 g (5 mmol) of zirconium tetrachloride (ZrCl4) and 0.83 g (5 mmol) of organic ligand 1,4-terephthalic acid (H2BDC) were accurately weighed; acetic acid (AA) was measured as a structure and defect modifier, and the amount used was 12 equivalents of the zirconium source, i.e., 60 mmol (about 3.4 mL). The catalyst prepared in the end is denoted as Cu@UiO-12AA.

[0058] Example 4: Preparation of Cu@UiO-36AA catalyst

[0059] The difference between Example 4 and Example 2 is that in step S1, 1.165 g (5 mmol) of zirconium tetrachloride (ZrCl4) and 0.83 g (5 mmol) of organic ligand 1,4-terephthalic acid (H2BDC) were accurately weighed; acetic acid (AA) was measured as a structure and defect modifier, and the amount used was 36 equivalents of the zirconium source, i.e., 180 mmol (about 10.3 mL). The catalyst finally prepared was denoted as Cu@UiO-36AA.

[0060] Example 5: Preparation of Cu@UiO-100AA catalyst

[0061] The difference between Example 5 and Example 2 is that in step S1, 1.165 g (5 mmol) of zirconium tetrachloride (ZrCl4) and 0.83 g (5 mmol) of organic ligand 1,4-terephthalic acid (H2BDC) were accurately weighed; acetic acid (AA) was measured as a structure and defect modifier, and the amount used was 100 equivalents of the zirconium source, i.e., 500 mmol (about 28.6 mL). The catalyst prepared in the end is denoted as Cu@UiO-100AA.

[0062] Comparative Example 1: Preparation of Cu@UiO-36AA-PSE catalyst

[0063] The UiO-36AA support prepared in Example 4 was subjected to post-synthetic ligand exchange treatment to repair its missing ligand defects, resulting in a nearly defect-free UiO-36AA-PSE. Then, 15 wt.% Cu was loaded onto it using the same method as step S2 in Example 4.

[0064] Comparative Example 2: Preparation of a conventional Cu / ZrO2 catalyst

[0065] A 15 wt.% Cu / ZrO2 catalyst was prepared by impregnation.

[0066] Table 1 shows a comparison of the CO2 conversion and product selectivity of the Cu@UiO-xAA catalysts prepared in Examples 1-5 with different defect concentrations and those prepared in comparative documents 1 and 2. It can be seen that the amount of acetic acid regulator (0 AA to 100 AA) affects the Cu@UiO-66 catalyst... Significant impact on hydrogenation performance: With increasing acetic acid equivalent, the selectivity of methanol (CH3OH) first increases and then decreases, reaching a peak (approximately 65%) at 36 AA. The conversion rate also reached its highest value (approximately 6.5%) here, indicating that appropriate acetic acid regulation can optimize the defect structure and enhance the electronic interaction (EMSI) at the Cu-support interface, thereby efficiently promoting methanol production; while excessive acetic acid (such as 100AA) destroys the structural order or blocks the active sites, resulting in a decrease in both selectivity and conversion rate, proving that "defect engineering" requires precise regulation to maximize catalytic performance.

[0067] Table 1 Catalytic activity data for each catalyst

[0068]

[0069] Table 1 shows the comparison of space-time yield versus temperature for the Cu@UiO-xAA catalysts with different defect concentrations prepared in Examples 1-5 and those prepared in comparative documents 1 and 2. Catalyst performance was evaluated in a fixed-bed reactor (P = 3.2 MPa, T = 220-300 °C, H2 / CO2 = 3, GHSV = 8000 mL·g). -1 ·h -1 The results showed that the catalytic performance exhibited a volcano-like variation with defect concentration, with Cu@UiO-36AA showing the best performance (CO2 conversion 6.21% @260 °C, methanol STY 111.15 mg·g). -1 ·h -1 ).

[0070] Figure 1 Thermogravimetric analysis curves of different samples from Examples 1-5 and Comparative Example 1 are used to quantitatively calculate the defect concentration comparison chart; Table 2 estimates the number of UiO-xAA carriers (x = 0, 6, 12, 36 and 100) prepared in Examples 1-5 and the number of UiO-36AA-PSE missing linkers prepared in Comparative Example 1 by thermogravimetric analysis (TGA).

[0071] Table 2 Thermogravimetric Test Results

[0072]

[0073] The TGA analysis above indicates that the defect concentration of UiO-36AA is 1.08 ligand-deficient units / Zr6 unit. This suggests that the moderately defective structure introduced through regulation with 36 equivalents of acetic acid is most favorable for constructing highly active structures. -O 2- -Zr 4+ The interface is optimized to maximize catalytic efficiency; however, excessively high or low acetic acid content (such as 0AA or 100AA) leads to a decrease in STY, further confirming that "the defect concentration needs to be precisely optimized" in order to balance the number and stability of active sites and achieve the optimal solution for CO2 hydrogenation to methanol performance.

[0074] Performance comparison: Under the same reaction conditions (260 °C, 3.2 MPa, 8000 mL·g), -1 ·h -1 (Evaluate)

[0075] Table 1 clearly demonstrates the multiplier effect of defect engineering and interface structure design on catalytic performance by comparing the CO2 conversion, methanol selectivity, and methanol space-time yield (STY) of different catalysts: Cu@UiO-36AA-PSE (Example 4): CO2 conversion 6.21%, methanol selectivity 64.96%, methanol STY 111.15 mg·g -1 ·h -1 Cu@UiO-36AA-PSE (Comparative Example 1): CO2 conversion 4.69%, methanol selectivity 36.33%, methanol STY approximately 46.82 mg·g -1 ·h -1 Cu / ZrO2 (Comparative Example 2): CO2 conversion 2.62%, methanol selectivity 30.18%, methanol STY approximately 21.75 mg·g -1 ·h -1 The methanol STY of Cu@UiO-36AA-PSE (Example 4) was 2.4 times and 5.1 times that of Cu@UiO-36AA-PSE (Comparative Example 1) and Cu / ZrO2 (Comparative Example 2), respectively.

[0076] The above results demonstrate that precise control of MOF support defects and enhancement of metal-support electronic interactions (EMSI) can significantly activate interfacial sites and suppress side reactions, thereby achieving a synergistic breakthrough of "high selectivity + high yield" in CO2 hydrogenation to methanol. This comparative example fully proves that it is precisely the presence of defects that induces the formation of a unique Cu-(O)-Zr interface and electron-deficient Cu active centers, leading to the leap in performance.

[0077] Figure 2 , Figure 3Transmission electron microscopy (TEM) of the Cu@UiO-36AA catalyst prepared in Example 4 directly reveals the precise control of the microstructure of the Cu@UiO-36AA catalyst by the acetic acid modulation strategy: TEM images show that the Cu nanoparticles in the catalyst prepared with 36AA optimization are uniform in size (~7.5 nm), highly dispersed, and form a clear interface with the UiO-66 support. The lattice fringes correspond to Cu(111) and ZrO2(002), confirming the strong metal-support interaction; indicating that the Cu nanoparticles are anchored at the defect sites of the MOF framework, forming a stable... -O 2- -Zr 4+ Active interface—this “atomic-level dispersion + interface coupling” structure is the key physical basis for achieving high methanol selectivity and conversion rate.

[0078] Figure 4 The Cu LMM spectrum revealed significant charge transfer between Cu and Zr oxygen clusters in the Cu@UiO-36AA catalyst prepared in Example 4, and the Cu LMM Auger electron spectroscopy indicated that copper species... The primary characteristic is that, compared to the Cu@UiO-36AA-PSE prepared in Comparative Example 1 (916.72 eV), the Cu@UiO-36AA prepared in Example 4 exhibits a lower kinetic energy (915.95 eV), indicating that Cu... + The proportion is higher. This may be due to the presence of more interface sites, such as -O 2- -Zr 4+ and -Zr 4+ .

[0079] Figure 5 The H2-TPR spectrum revealed a single reduction feature below approximately 300 °C, which could be deconvolved into two components: a low-temperature peak attributed to highly dispersed CuO, and a high-temperature peak corresponding to CuO species or bulk CuO strongly interacting with Zr6-oxygen clusters. Due to stronger Cu-(O)-Zr interfacial bonding, the Cu@UiO-36AA prepared in Example 4 exhibited a higher reduction temperature (285.2 °C), making the interfacial oxygen more difficult to reduce. In contrast, the Cu@UiO-36AA-PSE prepared in Comparative Example 1, due to its larger particle size and weaker interfacial interactions, exhibited a lower reduction temperature (267.0 °C).

[0080] The above results demonstrate that there is a stronger metal-support interaction in the defective catalyst.

[0081] Table 3 shows the 110-hour long-term stability test results of the optimal catalyst in Example 4 of this invention. In the continuous reaction test of 110 hours, no obvious activity decay or selectivity decrease was observed, which shows excellent operational stability and good prospects for industrial application.

[0082] Table 3. Stability test results of Example 4

[0083]

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A kind of -O 2- -Zr 4+ A method for preparing MOF-based catalysts with interfacial active centers, characterized in that, Includes the following steps: S1. Synthesis of defective UiO-xAA support: The zirconium source, organic ligand and monocarboxylic acid regulator were accurately weighed, dissolved in an organic solvent, mixed evenly, and then transferred to a reaction vessel for solvothermal reaction. After the reaction was completed, the mixture was washed with organic solvent and anhydrous ethanol and dried to obtain porous defective support UiO-xAA with different concentrations of missing ligands (x is the monocarboxylic acid equivalent). The amount of monocarboxylic acid used was 0~100 equivalents of zirconium source. S2. Loading of Cu nanoparticles: The defective support UiO-xAA obtained in step S1 is dispersed in a copper salt solution for impregnation and adsorption. The loading amount of Cu is 5~20 wt.%. The solid with adsorbed copper ions is dried, calcined, and further reduced in a reducing atmosphere.

2. The method for preparing the MOF-based catalyst as described in claim 1, characterized in that, In step S1, the zirconium source is zirconium tetrachloride (ZrCl4) or zirconium oxychloride (ZrOCl2), the organic ligand is 1,4-terephthalic acid (H2BDC) or a ligand with functional groups such as -OMe, -NH2, -F, -SO3H, -OH, -Br, and -CH3, the monocarboxylic acid modifier is one of acetic acid (AA), formic acid (FA), trifluoroacetic acid (TFA), and hydrochloric acid (HCl), the organic solvent is N,N-dimethylformamide (DMF), and the prepared UiO-xAA series zirconium-based metal-organic framework material is one of UiO-66, UiO-67, UiO-68 or MOF-808.

3. The method for preparing the MOF-based catalyst as described in claim 2, characterized in that, In step S1, the zirconium source is zirconium tetrachloride (ZrCl4), the organic ligand is 1,4-terephthalic acid (H2BDC), the monocarboxylic acid regulator is acetic acid, and the organic solvent is N,N-dimethylformamide (DMF). The prepared UiO-xAA series zirconium-based metal-organic framework material is UiO-66. The three components, zirconium tetrachloride (ZrCl4), 1,4-terephthalic acid (H2BDC) and acetic acid (AA), are added sequentially to an appropriate amount of organic solvent N,N-dimethylformamide (DMF) and mixed. The mixture is then stirred at room temperature on a magnetic stirrer for 30-60 min until all solids are completely dissolved, forming a clear and transparent homogeneous solution. The molar ratio of acetic acid to zirconium tetrachloride is 36:1 to obtain the optimal defect concentration.

4. The method for preparing the MOF-based catalyst as described in claim 3, characterized in that, In step S1, the clear and transparent homogeneous solution is transferred to a reaction vessel, which is then placed in an oven and heated to 120 °C. The reaction is then carried out at this temperature for 24 h.

5. The method for preparing the MOF-based catalyst as described in claim 4, characterized in that, After the reaction in step S1 is completed, the mixture is naturally cooled to room temperature, washed and dried with DMF and anhydrous ethanol, and the product is collected by centrifugation. The product is first washed three times with fresh DMF to remove unreacted organic matter and free acetic acid, and then washed three times with anhydrous ethanol to replace DMF molecules in the pores and facilitate drying, finally obtaining the porous defect type support UiO-xAA.

6. The method for preparing the MOF-based catalyst as described in claim 1, characterized in that, The copper salt solution in step S2 was prepared by dissolving copper nitrate (Cu(NO3)2·3H2O) in anhydrous ethanol, with a Cu loading of 15 wt.%.

7. The method for preparing the MOF-based catalyst as described in claim 6, characterized in that, Step S2: The UiO-xAA support obtained in step S1 is dispersed in a copper nitrate ethanol solution and then magnetically stirred at room temperature. The stirred suspension is transferred to a rotary evaporator and rotary evaporated under reduced pressure at a water bath of 40-60 °C for 1-2 h to slowly remove the ethanol solvent. The resulting blue, thick slurry substrate is then transferred to a vacuum drying oven and dried at 80 °C for 8-12 h to obtain a solid sample loaded with the copper precursor.

8. The method for preparing the MOF-based catalyst as described in claim 7, characterized in that, In step S2, the vacuum-dried sample is placed in a tube furnace and calcined at a constant temperature under a nitrogen atmosphere of 50-100 mL / min. The calcined sample is then placed in a fixed-bed reactor or reduction furnace, and pure hydrogen (H2) or a 5% H2 / Ar mixture is introduced. The sample is then reduced at a constant temperature of 250 °C for 2 h to obtain the Cu@UiO-xAA catalyst.

9. A catalyst prepared using the method described in any one of claims 2 to 8, possessing... -O 2- -Zr 4+ The MOF-based catalyst with an interfacial active center, this defective UiO-xAA support contains a specific concentration of "ligand-deficient defects," located in the Zr6 oxygen cluster ([Zr6O4(OH)4)). 12+ On the Zr cluster, the organic ligands that should have coordinated with the Zr cluster are missing, thus exposing the Zr sites that are not coordinated. The copper nanoparticles are encapsulated in the defective UiO-xAA support and are preferentially anchored to the Zr sites that are not coordinated through chemical bonds (Zr-O-Cu), thus forming a tight Cu-(O)-Zr heterointerface with the Zr6 oxygen cluster.

10. The one having as described in claim 9 -O 2- -Zr 4+ Application of MOF-based catalysts with interfacial active centers in the CO2 hydrogenation to methanol reaction.

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