One-dimensional metal organic framework material for photocatalytic CO2 reduction as well as preparation method and application of one-dimensional metal organic framework material

Abstract

The invention discloses a one-dimensional metal organic framework material for photocatalytic CO2 reduction as well as a preparation method and application of the one-dimensional metal organic framework material, zinc ions and ellagic acid hydroxyl construct firm planar four-coordination, so that the one-dimensional metal organic framework material has excellent stability; the one-dimensional metal organic framework material has the advantages that the one-dimensional metal organic framework material is coordinated with two water in the longitudinal direction to form a stable six-coordination structure, so that the one-dimensional metal organic framework material has open metal sites and shows excellent photocatalytic performance; the generation rates of CO and H2 reduction through photocatalysis of CO2 can reach 7.26 mmol / h / g and 0.04 mmol / h / g respectively, and the selectivity to CO is as high as 98.94%. According to the preparation method disclosed by the invention, a natural product ellagic acid massively existing in the nature is adopted as an organic ligand, so that additional synthesis of the organic ligand is avoided, the synthesis period of the MOF material is short, the cost is reduced, and the MOF material is environment-friendly; in addition, a solvothermal method is adopted for synthesis of MOF, the process is mature, reaction conditions are mild and easy to control, and single crystals and gram-grade products can be prepared.

Description

Technical Field

[0001] This invention belongs to the field of novel metal-organic materials, specifically relating to a one-dimensional metal-organic framework material for photocatalytic CO2 reduction, its preparation method, and its application. Background Technology

[0002] Biomass energy is the largest and most widely distributed renewable energy source on Earth, with broad application prospects. However, its development currently faces certain limitations, as the direct use of biomass resources to construct high-end functional materials is relatively scarce. On the other hand, the rapid consumption of traditional fossil fuels inevitably releases large amounts of greenhouse gases, including CO2, disrupting the ecological balance, exacerbating the greenhouse effect, and harming the human living environment. Therefore, accelerating the use of biomass resources to replace traditional fossil fuels, and simultaneously using biomass resources as raw materials to construct functional materials to mitigate CO2 emissions, is of paramount importance.

[0003] Reducing generated CO2 into value-added substances (such as CO, HCOOH, CH4, etc.) using various physicochemical techniques is a feasible method. Common CO2 reduction methods include thermocatalysis, electrocatalysis, and photocatalysis. While thermocatalytic CO2 reduction is relatively mature, maintaining high temperature and pressure requires significant energy consumption, contradicting the goal of reducing energy consumption. Electrocatalytic CO2 reduction, although allowing precise product control at room temperature and pressure, often uses precious metals as catalysts, resulting in high costs and competitive hydrogen evolution reactions, wasting considerable electrical energy. In contrast, photocatalytic CO2 reduction operates under extremely mild conditions, driven by solar energy, directly converting solar energy into chemical energy, completing both "light capture" and "chemical conversion" in one step. Furthermore, integrating light collection, charge separation, and catalytic reaction into a single unit allows for very compact and simple device design, with the potential for large-scale deployment.

[0004] Achieving excellent photocatalytic reactions relies heavily on efficient photocatalysts. Metal-organic frameworks (MOFs), with their unique high specific surface area, designable crystal structures, abundant active sites, and good dispersibility, are increasingly being used in photocatalytic CO2 reduction. MOFs are a class of porous crystalline materials formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination bonds, combining the stability of inorganic materials with the designability of organic materials. Based on the spatial dimension of the framework structure, they can be classified into four categories: zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D). Different dimensional framework structures exhibit significant differences in mass transport, light absorption, active site exposure, and stability, thus directly affecting the photocatalytic CO2 reduction efficiency.

[0005] While zero-dimensional MOFs exhibit high specific surface area and abundant exposed sites, their tendency to aggregate and limited photogenerated carrier separation efficiency remain unresolved. Two-dimensional MOFs possess extremely high specific surface area and active site exposure rates, but they are prone to recombination during preparation and processing, leading to the burial of active sites. Three-dimensional MOFs have regular and interconnected porous channels and stable structures, but their bulk charge separation efficiency and internal active site utilization are low. One-dimensional MOF nanowires combine the high specific surface area of ​​zero-dimensional materials with the directional transport advantages of three-dimensional materials, exhibiting unique advantages in photocatalytic CO2 reduction. Therefore, this application provides a one-dimensional metal-organic framework material for photocatalytic CO2 reduction, its preparation method, and its application. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the first objective of this invention is to provide a one-dimensional metal-organic framework material for photocatalytic CO2 reduction, wherein the one-dimensional nanowire structure formed by the coordination of ellagic acid ligands and zinc ions forms a robust planar four-coordinate and a flexible longitudinal dihydrate coordination; the MOFs exhibit high stability and can fully expose metal sites to participate in catalysis during the catalytic process, thereby improving photocatalytic performance.

[0007] The second objective of this invention is to provide a method for preparing the aforementioned one-dimensional metal-organic framework (MOF) material for photocatalytic CO2 reduction. This method utilizes ellagic acid, a biomass feedstock, as a ligand, and chelates it with non-toxic zinc ions via a thermal reaction. This method enables the preparation of single-crystal and gram-scale one-dimensional MOF materials, overcoming the currently prevalent problems of difficult MOF raw material supply, long synthesis cycles, and high costs.

[0008] The third objective of this invention is to provide an application of the aforementioned one-dimensional metal-organic framework material in photocatalytic CO2 reduction.

[0009] One of the objectives of this invention can be achieved by adopting the following technical solutions:

[0010] A one-dimensional metal-organic framework material for photocatalytic CO2 reduction, comprising the organic ligand ellagic acid and zinc ions; each Zn 2+ The ion coordinates horizontally with the two deprotonated hydroxyl groups and two undeprotonated hydroxyl groups of two ellagic acid molecules, forming a plane; and vertically with two water molecules, forming a six-coordinate structure. Each ellagic acid molecule has two hydroxyl groups on the same benzene ring, one deprotonated and one undeprotonated, which coordinate with the same Zn group. 2+ Ion coordination linkage.

[0011] Furthermore, the one-dimensional metal-organic framework material used for photocatalytic CO2 reduction is triclinic. PSpace group -1, cell parameters a=4.9713Å, b=6.9610Å, c=11.2805Å, α=82.709°, β=83.188°, γ=69.560°.

[0012] The second objective of this invention can be achieved by adopting the following technical solution:

[0013] A method for preparing one-dimensional metal-organic framework materials for photocatalytic CO2 reduction includes the following steps:

[0014] The zinc ion precursor and ellagic acid were subjected to a solvothermal reaction in a solvent, and the one-dimensional metal-organic framework material for photocatalytic CO2 reduction was obtained after the reaction was completed.

[0015] Furthermore, the solvothermal reaction is carried out in a sealed glass tube or by stirring in a reaction vessel.

[0016] Furthermore, the solvent is a mixture of an organic solvent and water, wherein the volume ratio of the organic solvent to water is 1:(1-3).

[0017] Furthermore, the organic solvent is one or a combination of two of N,N-dimethylformamide or N,N-dimethylacetamide.

[0018] Furthermore, the zinc ion precursor is one or more of zinc ion chlorides, nitrates, acetates, and their hydrates.

[0019] Furthermore, the molar ratio of ellagic acid to zinc ion precursor is (1-1.5):1.

[0020] Furthermore, the characteristic feature is that the molar-volume ratio of ellagic acid to solvent is 1 mmol: (10-40) ml.

[0021] Furthermore, the reaction conditions are 50-100℃ for 2-24 hours.

[0022] Furthermore, the reaction includes a post-processing step: solid-liquid separation after the reaction, washing the solid phase with DMA and / or DMF, H2O and ethanol, and vacuuming at room temperature to obtain the one-dimensional metal-organic framework material for photocatalytic CO2 reduction. The third objective of this invention can be achieved by adopting the following technical solutions:

[0023] The application of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction prepared by the above-mentioned preparation method for photocatalytic CO2 reduction in the photocatalytic CO2 reduction reaction.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention provides a one-dimensional metal-organic framework material for photocatalytic CO2 reduction, which uses natural polyhydroxy ellagic acid as an organic ligand and zinc ions to construct a one-dimensional metal-organic framework structure. The zinc ions and ellagic acid hydroxyl groups form a robust planar four-coordinate structure, giving the one-dimensional metal-organic framework material excellent stability. It also coordinates with two water molecules in the longitudinal direction to form a stable six-coordinate structure, giving the one-dimensional metal-organic framework material open metal sites and exhibiting excellent photocatalytic performance.

[0026] 2. The method for preparing one-dimensional metal-organic framework materials for photocatalytic CO2 reduction of the present invention uses ellagic acid, a natural product abundant in nature, as an organic ligand, avoiding the need for separate synthesis of organic ligands, thus shortening the MOF material synthesis cycle, reducing costs, and being environmentally friendly; in addition, the synthesis of MOF adopts a solvothermal method, which is a mature process with mild and easy-to-control reaction conditions, and can prepare single crystals and gram-scale products.

[0027] 3. When the one-dimensional metal-organic framework material of the present invention is used for photocatalytic CO2 reduction reaction, zinc ions exhibit unique reactivity. Compared with metal-organic framework materials constructed from group VIII and group IB transition metals, the conversion rate and selectivity of CO2 reduction to CO are greatly improved, demonstrating excellent photocatalytic CO2 reduction performance. Attached Figure Description

[0028] Figure 1 The crystal structure of the one-dimensional metal-organic framework material used for photocatalytic CO2 reduction in this invention is shown in Figure a, where a is the asymmetric unit of EA-Zn; b is the coordination mode of the central atom Zn; c is the coordination mode of the ligand EA; d is the one-dimensional chain-like derivative configuration of EA-Zn; and e is the arrangement mode of multiple EA-Zn chains.

[0029] Figure 2 Figure 1 shows the morphological appearance of EA-Zn single crystal; Figure a is a photograph of EA-Zn single crystal; Figure b is a SEM and EDS photograph of EA-Zn single crystal.

[0030] Figure 3 Figure 2 shows the morphological characteristics of EA-Zn powder; Figure a is a photograph of EA-Zn powder; Figure b is a SEM and EDS photograph of EA-Zn powder.

[0031] Figure 4 The X-ray powder diffraction pattern of the EA-Zn powder prepared in Example 2 of this invention;

[0032] Figure 5The X-ray powder diffraction patterns of EA-Zn prepared in Example 2 of this invention after soaking in different reagents for 7 days are shown.

[0033] Figure 6 The X-ray powder diffraction patterns of EA-Zn prepared in Example 2 of this invention after soaking in aqueous solutions of different pH values ​​for 7 days are shown.

[0034] Figure 7 The X-ray powder diffraction patterns of EA-Zn prepared in Examples 4-6 of this invention are shown below.

[0035] Figure 8 The X-ray photoelectron spectrum of EA-Zn prepared in Example 2 of this invention. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] One-dimensional MOF nanowire structures combine the abundant exposure sites of zero-dimensional materials with the directional transport advantages of three-dimensional materials, exhibiting unique advantages in photocatalytic CO2 reduction. Specifically: 1. They possess highly efficient directional charge transport channels; their framework structure extends continuously along the long axis, providing pathways for directional electron migration and reducing scattering and recombination losses caused by grain boundaries and defects during electron transport; 2. They exhibit anisotropic synergistic effects; the one-dimensional structure achieves an ideal balance between long-range electron transport and short-range mass transport; 3. They are easy to construct hierarchical porous macrostructures; one-dimensional nanowires can serve as excellent "building blocks," constructing three-dimensional porous network structures (such as aerogels, sponges, or self-supporting films) through self-assembly or template methods, which simultaneously solves the problem of nanomaterial recycling. Therefore, this application provides a one-dimensional metal-organic framework material for photocatalytic CO2 reduction.

[0038] Currently, the metal ions reported to be synthesized with ellagic acid (EA) include Bi, Zr, Pb, Ca, Fe, Co, Ni, and Cu. However, the MOFs formed with Bi and Zr are powdery three-dimensional structures (not single crystals), and their structures are determined by 3D electron diffraction. The MOFs formed with Pb (two-dimensional) and Ca (three-dimensional) are single crystals, and their structures are determined by X-ray single crystal diffraction. However, it is worth noting that the reported MOFs formed with Fe, Co, Ni, and Cu are all powders. Although they are crystalline, they lack a clear single-crystal structure, and their structures are merely guesses based on software simulations (as is well known, software simulations are inaccurate; for example, even with the same topological structure, different local ligand side chains or different metal coordination can result in the same xrd, thus the industry generally recognizes that they have a large error). Furthermore, the four reported MOFs—Fe-EA, Co-EA, Ni-EA, and Cu-EA—all require the use of surfactants PVP (polyvinylpyrrolidone) or CTAB (cetyltrimethylammonium bromide) for assisted synthesis. These two materials have high foaming properties (i.e., generate a large amount of foam), which makes post-processing (including post-modification and washing) difficult. Therefore, this application provides a one-dimensional metal-organic framework material for photocatalytic CO2 reduction and its preparation method.

[0039] A one-dimensional metal-organic framework material for photocatalytic CO2 reduction, comprising the organic ligand ellagic acid and zinc ions; each Zn 2+ The ion coordinates horizontally with the two deprotonated hydroxyl groups and two undeprotonated hydroxyl groups of two ellagic acid molecules, forming a plane; and vertically with two water molecules, forming a six-coordinate structure. Each ellagic acid molecule has two hydroxyl groups on the same benzene ring, one deprotonated and one undeprotonated, which coordinate with the same Zn group. 2+ Ion coordination linkage.

[0040]

[0041] Ellagic acid is a natural polyphenol component and a biomass resource found in nature. Using ellagic acid as a ligand for one-dimensional metal-organic frameworks avoids the significant manpower, financial, and time costs associated with ligand design, synthesis, extraction, separation, identification, and purification, as well as the problems of low yield. Furthermore, its planar fused-ring structure and the two hydroxyl groups at both ends, which coordinate with metal ions, provide a structural basis for one-dimensional metal-organic frameworks.

[0042] The molecular formula of the one-dimensional metal-organic framework material used for photocatalytic CO2 reduction is C0. 14 H 12 O 12 Zn [+solvent] (EA-Zn); crystal structure as follows Figure 1 As shown.

[0043] The asymmetric unit of EA-Zn consists of a Zn 2+ It consists of a partial ellagic acid anion and a free water molecule. Figure 1 a). The central metal atom Zn forms a plane horizontally with two deprotonated hydroxyl groups and two undeprotonated hydroxyl groups from two ellagic acid molecules, and vertically coordinates with two water molecules, forming a six-coordinate structure. Figure 1 b); while the four hydroxyl groups of ligand EA are partially deprotonated and their ends are bonded to Zn. 2+ Coordination ( Figure 1 c). Therefore, the central atom Zn and the ligand EA alternately coordinate to form a one-dimensional extended chain structure ( Figure 1 d), these chain-like structures are slightly misaligned to form a one-dimensional chain-like EA-Zn ( Figure 1 e).

[0044] When ellagic acid coordinates with zinc ions, one of the two hydroxyl groups on the same benzene ring of the ellagic acid molecule is deprotonated, while the other remains unprotonated. Conversely, each of the two hydroxyl groups on the same benzene ring of the ellagic acid molecule coordinates with the same zinc ion, and each zinc ion coordinates with two ellagic acid molecules. The four hydroxyl groups of the two ellagic acids form a robust planar four-coordinate structure with the zinc ions, while the central atom Zn alternately coordinates with the ligand ellagic acid to form a one-dimensional extended chain structure, constituting the main body of the one-dimensional metal-organic framework material. Furthermore, each zinc ion also flexibly coordinates with two water molecules in the longitudinal direction, removing water molecules during the photocatalytic reaction to form open zinc metal catalytic sites, achieving excellent photo-CO2 reduction performance.

[0045] As one embodiment, the one-dimensional metal-organic framework material used for photocatalytic CO2 reduction is triclinic. P Space group -1, cell parameters a=4.9713Å, b=6.9610Å, c=11.2805Å, α=82.709°, β=83.188°, γ=69.560°.

[0046] This application also provides a method for preparing a one-dimensional metal-organic framework material for photocatalytic CO2 reduction, comprising the following steps:

[0047] The zinc ion precursor and ellagic acid were subjected to a solvothermal reaction in a solvent, and the one-dimensional metal-organic framework material for photocatalytic CO2 reduction was obtained after the reaction was completed.

[0048] In existing technologies, ellagic acid often coordinates with other transition metal ions or noble metal ions to form two-dimensional or three-dimensional structures; none use inexpensive zinc as a coordination center. However, this application synthesizes one-dimensional metal-organic frameworks (MOFs) by a solvothermal reaction of zinc ion precursors and ellagic acid in a solvent. Even with low-purity (80%) ellagic acid, this one-dimensional MOF can be successfully synthesized. Lower purity EA implies greater flexibility in the synthesis process and better application potential (existing technologies require at least 95% purity). Furthermore, this synthesis method has a short cycle and does not require the addition of surfactants such as PVP and CTAB to assist growth. Surfactants such as PVP and CTAB require multiple washings and are difficult to completely remove. Therefore, the method for synthesizing one-dimensional MOFs in this application shortens the reaction time and simplifies post-processing steps.

[0049] In one implementation method, the solvothermal reaction is carried out in a sealed glass tube or by stirring in a reaction vessel. When the solvothermal reaction is carried out in a small amount in a sealed glass tube, single-crystal products can be obtained; when the solvothermal reaction is carried out by stirring in a reactor, which generally refers to a reaction flask, the reaction can achieve gram-level production.

[0050] In one embodiment, the solvent is a mixture of an organic solvent and water, wherein the volume ratio of the organic solvent to water is 1:(1-3).

[0051] In a preferred embodiment, when preparing at the gram level, the zinc metal ion precursor is dissolved in water to prepare a precursor solution; ellagic acid is dissolved in an organic solvent; the two solutions are mixed and then heated for reaction.

[0052] In one embodiment, the organic solvent is one or a combination of two of N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA).

[0053] As one embodiment, the zinc ion precursor is one or more of zinc ion chlorides, nitrates, acetates, and their hydrates.

[0054] In one embodiment, the molar ratio of ellagic acid to zinc ion precursor is (1-1.5):1.

[0055] As one embodiment, the feature is that the molar-volume ratio of ellagic acid to solvent is 1 mmol: (10-40) ml.

[0056] As one implementation method, the reaction conditions are 50-100°C for 2-24 hours.

[0057] As one embodiment, the reaction also includes a post-processing step: after the reaction is completed, solid-liquid separation is performed, the solid phase is washed with DMA and / or DMF, H2O and ethanol, and vacuum is applied at room temperature to obtain the one-dimensional metal-organic framework material for photocatalytic CO2 reduction.

[0058] This application describes the use of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction prepared by the above-mentioned method for photocatalytic CO2 reduction in the photocatalytic CO2 reduction reaction.

[0059] As one implementation method, Ru(phen)3 is used. 2+ The compound was used as a photosensitizer, and triethylamine (TEA) was used as a sacrificial agent to carry out a photocatalytic CO2 reduction reaction in a quartz reactor containing a CO2-saturated CH3CN-H2O mixture.

[0060] The following is a further explanation using specific embodiments. Example 1

[0061] 0.04 mmol of zinc chloride hexahydrate and 0.04 mmol of ellagic acid (98% purity) were added to a glass tube. 0.4 mL of H₂O and 0.4 mL of N,N-dimethylacetamide were added to separate glass tubes. The glass tubes were sealed with an oxyhydrogen flame, sonicated for 20 min to mix thoroughly, and then heated in an 85°C oven for 4 h. After natural cooling to room temperature, the crystals were filtered out, washed repeatedly with N,N-dimethylacetamide, deionized water, and ethanol, and then vacuum dried at room temperature to obtain a one-dimensional metal-organic framework single crystal for photocatalytic CO₂ reduction, denoted as EA-Zn single crystal. Its appearance is as follows: Figure 2 As shown in Figure a; SEM and EDS figures are shown in Figure a. Figure 2 As shown in Figure b. Example 2

[0062] 2 mmol of zinc dichloride hexahydrate was ultrasonically dissolved in 30 mL of H₂O, and 2.4 mmol of ellagic acid (98% purity) was ultrasonically dissolved in 20 mL of N,N-dimethylacetamide. The two solutions were then mixed and vigorously stirred in an oil bath at 85°C for 4 h. After natural cooling to room temperature, the crystals were separated by high-speed centrifugation and washed repeatedly with DMA, H₂O, and ethanol. The crystals were then vacuum-dried at room temperature to obtain a large quantity of one-dimensional metal-organic framework powder for photocatalytic CO₂ reduction, denoted as EA-Zn powder; the yield was 82%. The powder morphology is as follows. Figure 3 As shown in Figure a; SEM and EDS figures are shown in Figure a. Figure 3 As shown in Figure b. Example 3

[0063] 2 mmol of zinc dichloride was ultrasonically dissolved in 90 mL of H2O, and 3 mmol of ellagic acid (98% purity) was ultrasonically dissolved in 30 mL of N,N-dimethylformamide. The two solutions were then mixed and vigorously stirred in an oil bath at 100°C for 2 h. After cooling naturally to room temperature, the crystals were separated by high-speed centrifugation and washed multiple times with DMA, H2O and ethanol. The crystals were then vacuum dried at room temperature to obtain a large amount of one-dimensional metal-organic framework material powder for photocatalytic CO2 reduction, denoted as EA-Zn powder.

[0064] Examples 4-6

[0065] The difference between Examples 4-6 and Example 2 is that the purity of ellagic acid is 95%, 90%, and 80%, respectively; other preparation conditions are the same as in Example 2.

[0066] Characterization example:

[0067] (1) The EA-Zn powder prepared in Example 2 was subjected to X-ray powder diffraction test. The X-ray powder diffraction pattern is shown below. Figure 4 As shown. The EA-Zn powder prepared in Example 2 was soaked in different reagents (acetic acid, acetonitrile, acetone, tetrahydrofuran, ethanol) for 7 days, then centrifuged and dried under the same conditions, and X-ray powder diffraction was performed. The test results are shown below. Figure 5 As shown; the EA-Zn powder prepared in Example 2 was soaked in aqueous solutions of different pH values ​​for 7 days, then centrifuged and dried under the same conditions, and X-ray powder diffraction tests were performed. The test results are as follows. Figure 6 As shown; X-ray powder diffraction tests were performed on the EA-Zn powders prepared in Examples 4-6, and the X-ray powder diffraction patterns are shown below. Figure 7 As shown in Table 1, the crystallographic data of EA-Zn are as follows.

[0068] Table 1 Crystallographic data of EA-Zn

[0069]

[0070] from Figure 4 The X-ray powder diffraction test results show that the diffraction pattern of the synthesized EA-Zn is highly consistent with the peak position of the single-crystal simulated X-ray powder diffraction, indicating that the synthesized EA-Zn is a pure phase. Moreover, the diffraction peaks of EA-Zn are strong and sharp, indicating that the synthesized metal-organic framework EA-Zn has good crystallinity.

[0071] from Figure 5-6It can also be seen that after EA-Zn was treated for 7 days in different pH values ​​(2-12) and various organic solvents such as acetic acid, acetonitrile, acetone, tetrahydrofuran, and ethanol, the diffraction peaks remained strong, indicating that it is stable under various conditions.

[0072] In addition, such as Figure 7 As shown, it can also be seen that EA-Zn with high crystallinity can be synthesized using EA of different purities. Even with EA purity as low as 80%, the same product can be obtained as the material prepared using ellagic acid with 98% purity. The lower purity means lower cost, which highlights the economic advantages of the preparation method of this application and has potential application potential.

[0073] (2) The EA-Zn prepared in Example 2 was subjected to X-ray photoelectron spectroscopy (XPS) analysis. The XPS image is shown below. Figure 8 As shown.

[0074] Figure 8 The XPS plots revealed the valence state and bonding of the central atom in the EA-Zn group. Figure 8 In the XPS full spectrum of EA-Zn, Zn2 is clearly visible. p O1 s and C1 s peak( Figure 8 a). Specifically, the fine spectrum of Zn at 1045 eV is 2 p 2 at 1 / 2 and 1021.9 eV p 3 / 2 exhibits the typical +2 valence characteristic of Zn ( Figure 8 b); C1 s The peaks in the fine spectrum correspond to the bonds on the ligand ellagic acid. Figure 8 c) O1 s The fine spectrum shows Zn-O bonds, confirming the fact that Zn atoms are bonded to O atoms on ellagic acid, and the presence of the -OH peak also indicates that undeprotonated hydroxyl groups are still present on ellagic acid. Figure 8 d), which is consistent with the crystal structure analysis.

[0075] Experimental example:

[0076] (1) Photocatalytic CO2 reduction performance test

[0077] Test method: The photocatalytic activity of EA-Zn for CO2 reduction was investigated under visible light irradiation. Ru(phen)3 was used. 2+The compound was used as a photosensitizer, and triethylamine (TEA) as a sacrificial agent. The reaction was carried out in a quartz reactor containing a CO2-saturated CH3CN-H2O mixture. The photocatalytic results under different conditions are shown in Table 2. The catalytic results with catalyst recycling are shown in Table 3; the catalytic performance of EA-Fe, EA-Co, EA-Ni, and EA-Cu materials prepared according to the literature method is shown in Table 4.

[0078] Table 2 Photocatalytic activity of EA-Zn under different conditions

[0079]

[0080] Table 2 shows the photocatalytic activity of EA-Zn after 3 hours of LED irradiation under different solvent ratios. When the solvent ratio is CH3CN:H2O = 6:2, the EA-Zn catalyst exhibits the best performance, with CO and H2 generation rates of 7.26 mmol / h / g and 0.04 mmol / h / g, respectively, and a selectivity for CO of over 98%.

[0081] Table 3. Photocatalytic cycling activity of EA-Zn.

[0082]

[0083] As can be seen from Table 3, after 6 cycles of use, the CO2 reduction performance of EA-Zn did not change much, indicating that it has good cycling performance and potential applicability.

[0084] Table 4. Photocatalytic activity of EA-M.

[0085]

[0086] More importantly, under the same conditions, the photocatalytic CO2 reduction activity and selectivity of analogues EA-M (EA-Fe, EA-Co, EA-Ni and EA-Cu) synthesized from other metals (Fe, Co, Ni and Cu) and ellagic acid were significantly lower than those of EA-Zn, indicating that EA-Zn is irreplaceable.

[0087] In summary, this invention utilizes naturally occurring polyhydroxy ellagic acid as an organic ligand to construct a one-dimensional metal-organic framework (MOF) material with zinc ions. The multiple phenolic hydroxyl groups in ellagic acid chelate with zinc ions to form a stable planar four-coordinate structure, giving the bio-MOF material unique stability. Zinc ions vertically coordinate with two weakly coordinated water molecules, forming a unique six-coordinate structure, providing the one-dimensional MOF material with open metal sites. The photocatalytic CO2 reduction rates for CO and H2 production reach 7.26 mmol / h / g and 0.04 mmol / h / g, respectively, with a CO selectivity as high as 98.94%, demonstrating excellent photocatalytic performance.

[0088] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A one-dimensional metal-organic framework material for photocatalytic reduction of CO2, characterized in that, comprising an organic ligand ellagic acid and a zinc ion; each Zn 2+ ion is coordinated in the horizontal direction with two deprotonated hydroxyl groups and two non-deprotonated hydroxyl groups of two ellagic acid molecules to form a plane, and in the vertical direction with two water molecules to form a six-coordinated structure; two hydroxyl groups on the same benzene ring of each ellagic acid molecule, one deprotonated and one non-deprotonated, are coordinated to the same Zn 2+ ion. 2.The one-dimensional metal-organic framework material for photocatalytic CO2 reduction according to claim 1, characterized in that, The one-dimensional metal-organic framework material for photocatalytic reduction of CO2 is triclinic, P -1 space group, with a unit cell parameter of a=4.9713 Å, b=6.9610 Å, c=11.2805 Å, α=82.709°, β=83.188°, γ=69.560°.

3. A method for preparing a one-dimensional metal-organic framework material for photocatalytic CO2 reduction as described in claim 1 or 2, characterized in that, comprising the following steps: subjecting the zinc ion precursor and the ellagic acid to a solvothermal reaction in a solvent, and obtaining the one-dimensional metal-organic framework material for photocatalytic CO2 reduction after the reaction is completed. 4.The preparation method of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction according to claim 3, characterized in that, the solvothermal reaction is carried out in a sealed glass tube or is stirred in a reaction container. 5.The preparation method of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction according to claim 3, characterized in that, the solvent is a mixed solvent of an organic solvent and water, wherein the volume ratio of the organic solvent to water is 1: (1-3) ; and the organic solvent is a combination of one or both of N, N-dimethylformamide and N, N-dimethylacetamide. 6.The preparation method of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction according to claim 3, characterized in that, the zinc ion precursor is one or a combination of two or more of a chloride, a nitrate, and an acetate of a zinc ion, and a hydrate thereof; and the molar ratio of the ellagic acid to the zinc ion precursor is (1-1.5) :

1. 7.The preparation method of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction according to claim 3, characterized in that, the molar volume ratio of the ellagic acid to the solvent is 1 mmol: (10-40) ml. 8.The preparation method of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction according to claim 3, characterized in that, the reaction condition is 50-100℃ for 2-24h. 9.The preparation method of the one-dimensional metal-organic framework material for photocatalytic CO2 reduction according to claim 3, characterized in that, the method further comprises a post-processing step after the reaction: after the reaction is completed, solid-liquid separation is performed, the solid phase is washed with DMA and / or DMF, H2O, and ethanol, and vacuumization is performed at room temperature, to obtain the one-dimensional metal-organic framework material for photocatalytic CO2 reduction. 10.The one-dimensional metal-organic framework material for photocatalytic CO2 reduction of claim 1 or 2, or the one-dimensional metal-organic framework material for photocatalytic CO2 reduction prepared by the preparation method of any one of claims 3-9, is applied in a photocatalytic CO2 reduction reaction.

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