Zn-tib-bdc crystal and preparation method and application thereof

Abstract

The application relates to the field of photocatalytic CO2 reduction, in particular to a Zn-TIB-BDC crystal and a preparation method and application thereof. The application synthesizes a MOF material, namely the Zn-TIB-BDC crystal with a specific crystal structure, through coordination self-assembly of zinc nitrate hexahydrate, 1,3,5-triazole benzene and terephthalic acid. The Zn-TIB-BDC crystal provided by the application is a novel nitrogen-containing metal organic framework crystal, nitrogen-containing ligands which can be used as Lewis base sites are introduced into the framework structure, efficient adsorption and activation of CO2 molecules are realized, meanwhile, the light absorption capacity and charge separation efficiency of the material are optimized, so that the performance of photocatalytic CO2 reduction is significantly improved, and the demand for CO2 resource utilization and green low-carbon development is met.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic CO2 reduction, and more specifically, to a Zn-TIB-BDC crystal, its preparation method, and its application. Background Technology

[0002] The photocatalytic reduction of CO2 can be viewed as a simulation of photosynthesis in nature. This reaction is a complex process involving multiple electrons and protons. Its core lies in using light energy to excite the catalyst to generate photogenerated electron-hole pairs. These high-energy electrons and holes are the direct driving force behind the entire reduction and oxidation reaction. The entire photocatalytic CO2 reduction reaction process can be divided into the following four core steps: 1. **Photoabsorption:** The photocatalyst (usually a semiconductor, such as TiO2, g-C3N4, etc.) absorbs photons with energy greater than its band gap, causing electrons in its valence band to jump to the conduction band, leaving a hole in the valence band. 2. **Carrier Separation and Migration:** After separation, photogenerated electrons and holes migrate from the bulk phase of the material to the surface. 3. **Surface Adsorption and Activation:** CO2 molecules first need to be adsorbed onto the active sites on the catalyst surface. The structure of the adsorbed CO2 molecules is distorted and polarized, breaking its chemical inertness (the dissociation enthalpy of the C=O bond is as high as ~750 kJ / mol), preparing for subsequent reactions. 4. **Surface Redox Reaction:** The adsorbed CO2 gains photogenerated electrons and protons, undergoing a reduction reaction to produce carbon monoxide (CO), methane (CH4), methanol (CH3OH), formic acid (HCOOH), etc. Simultaneously, photogenerated holes oxidize water (H2O) or a sacrificial agent at the other end of the catalyst, providing the required protons (H+). + And complete the reaction cycle. It can be seen that photocatalysts can not only capture light energy and convert it into chemical energy to provide energy for CO2 activation and conversion, but also adsorb and activate CO2 to reduce the activation energy barrier for C=O bond breaking, playing an important role in photocatalytic CO2 reduction.

[0003] Metal-organic frameworks (MOFs) are crystalline porous materials with a periodic network structure, formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination bonds. Their large specific surface area, high porosity, and abundant active sites make them advantageous as photocatalysts for the efficient adsorption and activation of CO2 molecules, thereby improving the efficiency of photocatalytic CO2 reduction reactions. However, existing MOF materials generally suffer from limited visible light absorption, insufficient CO2 adsorption and activation capabilities, low efficiency in the formation of key intermediates, low selectivity for target products, and low catalytic efficiency, thus limiting their application in photocatalytic CO2 reduction reactions. Therefore, developing metal-organic frameworks with well-defined structures and good photocatalytic CO2 reduction performance is of great significance. Summary of the Invention

[0004] To address the technical problem of low catalytic efficiency in existing MOF materials, this invention provides a Zn-TIB-BDC crystal, its preparation method, and its application.

[0005] This invention synthesizes a MOF material with a specific crystal structure—Zn-TIB-BDC crystal—through coordination self-assembly of zinc nitrate hexahydrate (Zn(NO3)3•6H2O), 1,3,5-triimidazolebenzene (TIB), and terephthalic acid (BDC).

[0006] The Zn-TIB-BDC crystal provided by this invention is a novel nitrogen-based metal-organic framework crystal. By introducing nitrogen-containing ligands that can serve as Lewis base sites into the framework structure, it achieves efficient adsorption and activation of CO2 molecules, while optimizing the light absorption capacity and charge separation efficiency of the material, thereby significantly improving the performance of photocatalytic CO2 reduction to meet the needs of CO2 resource utilization and green and low-carbon development.

[0007] One of the objectives of this invention is to provide a Zn-TIB-BDC crystal.

[0008] The chemical formula of the Zn-TIB-BDC crystal is C. 27 H 21 N6O7Zn.

[0009] The chemical formula C 27 H 21 N6O7Zn refers to the ratio of the net number of atoms in the unit cell of a Zn-TIB-BDC crystal.

[0010] The powder X-ray diffraction of the Zn-TIB-BDC crystal has characteristic peaks at least at diffraction angles of 2θ = 10.1 ± 0.2°, 12.2 ± 0.2°, 17.2 ± 0.2°, 18.4 ± 0.2° and 27.7 ± 0.2°.

[0011] The powder X-ray diffraction of the Zn-TIB-BDC crystal has characteristic peaks at least at diffraction angles of 2θ = 6.1 ± 0.2°, 14.3 ± 0.2°, 15.1 ± 0.2°, 20.5 ± 0.2° and 25.7 ± 0.2°.

[0012] The FT-IR of the Zn-TIB-BDC crystal was 1600±5 cm⁻¹. -1 600±5 cm -1 With 450±5 cm -1 An absorption peak appears.

[0013] The FT-IR of the Zn-TIB-BDC crystal is approximately 1600 cm⁻¹. -1The absorption peak that appears is -COO - The stretching vibration peak is at 600 cm⁻¹. -1 With 450 cm -1 The absorption peaks that appear are the stretching vibration peaks of Zn-N and Zn-O.

[0014] The Zn-TIB-BDC crystal belongs to the monoclinic crystal system. P Space group 21 / c; its cell parameters include: a=14.4653 Å, b=7.8332 Å, c=22.604 Å, α=90°, β=91.759°, γ=90°.

[0015] In the Zn-TIB-BDC crystal, the same atom may have different coordination environments; Arabic numerals are added after the element symbol to distinguish atoms in different coordination environments. For example, O1 and O3 represent oxygen atoms in different coordination environments.

[0016] The Zn-TIB-BDC crystal has a Zn-O1 bond length of 1.999 Å, a Zn-O3 bond length of 1.939 Å, a Zn-N6 bond length of 2.040 Å, and a Zn-N1 bond length of 2.009 Å.

[0017] The O1-Zn-N6 bond angle of the Zn-TIB-BDC crystal is 104.48°, the O1-Zn-N1 bond angle is 110.23°, the O3-Zn-O1 bond angle is 113.50°, the O3-Zn-N6 bond angle is 105.95°, the O3-Zn-N1 bond angle is 116.53°, and the N1-Zn-N6 bond angle is 104.94°.

[0018] The smallest asymmetric unit of the Zn-TIB-BDC crystal comprises: one crystallographically independent metallic Zn 2+ The composition consists of ions, two 1,3,5-triimidazolylbenzene molecules, one fully deprotonated terephthalic acid molecule, and one partially deprotonated terephthalic acid molecule. A fully deprotonated terephthalic acid molecule is one terephthalic acid molecule with two hydrogen atoms (terephthalate ions) removed, while a partially deprotonated terephthalic acid molecule is one terephthalic acid molecule with one hydrogen atom removed.

[0019] The Zn-TIB-BDC crystal contains metallic Zn. 2+ Ions, 1,3,5-triimidazolylbenzene (TIB) and terephthalic acid (BDC); Metal Zn 2+The ion coordinates with two N atoms from two TIB ligands and two O atoms from two BDC ligands (one of which is a fully deprotonated BDC and the other is not fully deprotonated BDC), forming a distorted tetrahedral geometry.

[0020] In the Zn-TIB-BDC crystal: Each metal Zn 2+ The ion is linked to two TIB ligands and two BDC ligands (one of the two BDC ligands is a fully deprotonated BDC, and the other is a partially deprotonated BDC). Each TIB ligand is associated with two metallic Zn. 2+ Ion bonding, Each fully deprotonated BDC ligand is paired with two metallic Zn. 2+ Ion bonding, Each incompletely deprotonated BDC ligand is associated with a metallic Zn. 2+ Ion bonding.

[0021] The Zn-TIB-BDC crystal is an orange-yellow crystal.

[0022] The Zn-TIB-BDC crystal is a metal-organic framework material.

[0023] The Zn-TIB-BDC crystals can be produced by reacting zinc nitrate hexahydrate (Zn(NO3)3•6H2O), 1,3,5-triimidazolebenzene (TIB), and terephthalic acid (BDC); specifically, a hydrothermal method can be used.

[0024] The second objective of this invention is to provide a method for preparing the Zn-TIB-BDC crystal described in one of the objectives of this invention.

[0025] The preparation method of the Zn-TIB-BDC crystal includes: The raw materials, including zinc nitrate hexahydrate (Zn(NO3)3•6H2O), 1,3,5-triimidazolebenzene (TIB) and terephthalic acid (BDC), are subjected to a hydrothermal reaction.

[0026] The preparation method of the Zn-TIB-BDC crystal includes the following steps: 1) Mix zinc nitrate hexahydrate, 1,3,5-triimidazolebenzene, terephthalic acid and distilled water to form a suspension; 2) To induce a hydrothermal reaction in the suspension; 3) After the hydrothermal reaction is complete, cool down to room temperature.

[0027] As a preferred embodiment, the molar ratio of zinc nitrate hexahydrate, 1,3,5-triimidazole benzene, and terephthalic acid is (2±0.2):1:(2±0.2).

[0028] As a preferred option, the hydrothermal reaction temperature is 130~160 ℃, for example 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃.

[0029] As a preferred option, the hydrothermal reaction time is 48 hours or more, such as 60 hours, 66 hours, or 72 hours.

[0030] As a preferred option, the cooling rate is 1~10 ℃ / h, for example 2 ℃ / h, 5 ℃ / h, 8 ℃ / h.

[0031] As a specific embodiment, the method for preparing the Zn-TIB-BDC crystal includes: 1) Add zinc nitrate hexahydrate (Zn(NO3)3•6H2O), 1,3,5-triimidazolebenzene (TIB) and terephthalic acid (BDC) to a beaker; the molar ratio of zinc nitrate hexahydrate, 1,3,5-triimidazolebenzene and terephthalic acid is 2:1:2; 2) Add distilled water to the above beaker and place the beaker in an ultrasonic bath to form a suspension; 3) Transfer the suspension to a polytetrafluoroethylene liner, place the liner into a stainless steel reactor, and place the reactor in an oven at 130~160 ℃ for reaction, maintaining the temperature for more than 48 h. 4) Slowly cool to room temperature at a rate of 1~10 ℃ / h to obtain the Zn-TIB-BDC crystal.

[0032] The Zn-TIB-BDC disclosed in this invention has high photocatalytic CO2 reduction to CO performance, with a CO generation rate of over 302.87 µmol / (g·h).

[0033] The third objective of this invention is to provide a photocatalyst for the photocatalytic reduction of CO2.

[0034] The photocatalyst comprises Zn-TIB-BDC crystal as described in one of the invention objectives or Zn-TIB-BDC crystal prepared by the preparation method described in another of the invention objectives.

[0035] The fourth objective of this invention is to provide an application of the photocatalyst described in the third objective of this invention in the field of photocatalytic CO2 reduction.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: The Zn-TIB-BDC crystal disclosed in this invention exhibits high photocatalytic CO2 reduction to CO performance, with a CO generation rate exceeding 302.87 µmol / (g·h). Compared to photocatalytic CO2 reduction without a catalyst, the Zn-TIB-BDC crystal significantly enhances the photocatalytic CO2 reduction performance.

[0037] Unless otherwise specified, the room temperature described in this invention is 15~30℃. Attached Figure Description

[0038] Figure 1 The appearance morphology of the Zn-TIB-BDC crystal prepared in Example 1; Figure 2 This is the crystal structure of the Zn-TIB-BDC crystal of the present invention; wherein, Figure 2 (a) is a schematic diagram of the smallest structural unit of the Zn-TIB-BDC crystal of the present invention; Figure 2 (b) shows Zn in Zn-TIB-BDC crystal. 2+ The coordination environment; Figure 2 (c) is a schematic diagram of the Zn-TIB-BDC crystal along the ac direction; Figure 2 (d) is a schematic diagram of the Zn-TIB-BDC crystal along the bc direction; Figure 3 Powder X-ray diffraction and simulated powder X-ray diffraction of the Zn-TIB-BDC crystal of the present invention; Figure 4 The infrared spectrum of the Zn-TIB-BDC crystal of the present invention; Figure 5 The cumulative CO production from photocatalytic CO2 reduction is shown as a function of time; among which, Figure 5 (a) shows the change in the cumulative amount of CO generated by CO2 reduction catalyzed by using the Zn-TIB-BDC crystal of the present invention as a photocatalyst over time; Figure 5 (b) The change in the cumulative amount of CO generated by catalytic CO2 reduction over time when no photocatalyst is added; Figure 5 (c) The cumulative amount of CO generated by catalytic CO2 reduction as a photocatalyst when Zn-TIB of Comparative Example 1 is used as a photocatalyst changes over time; Figure 6 The results show the photocatalytic performance and cycle stability test results of the Zn-TIB-BDC crystal of this invention. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0040] All reagents used in the following examples and experimental cases are commercially available products.

[0041] Zinc nitrate hexahydrate (Zn(NO3)3•6H2O) has a purity of 99% and is manufactured by Shandong Xiya Chemical Industry Co., Ltd. Terephthalic acid (BDC) has a purity of 98% and is manufactured by Shanghai Maclean Biochemical Technology Co., Ltd. 1,3,5-Triimidazolebenzene (TIB) has a purity of 97% and is manufactured by Jinan Henghua Technology Co., Ltd.

[0042] Example 1 0.2 mmol of zinc nitrate hexahydrate, 0.1 mmol of 1,3,5-triimidazolebenzene, and 0.2 mmol of terephthalic acid were weighed and added to a 25 mL beaker. Then, 9 mL of distilled water was added to the beaker, and the beaker was sonicated for 15 min to obtain a suspension. The suspension was transferred to a 25 mL polytetrafluoroethylene (PTFE) liner, which was then transferred to a high-pressure reactor. The reactor was placed in an oven at 140 °C for 72 h, and finally cooled to room temperature at a rate of 5 °C / h to obtain orange-yellow crystals. These orange-yellow crystals were named Zn-TIB-BDC crystals.

[0043] (1) The appearance morphology of the Zn-TIB-BDC crystal is as follows: Figure 1 As shown.

[0044] (2) Single-crystal X-ray diffraction (SC-XRD) was performed on Zn-TIB-BDC crystals. Single-crystal samples of Zn-TIB-BDC crystals were selected, and diffraction data were collected in the range of 2θ = 2.82°–56.72° using a MoKα radiation source (λ = 0.71073 Å) on a CCD surface detector diffractometer. The crystal temperature was stabilized at 296.15 K throughout the experiment using a constant temperature system. Subsequently, the Olex2 software platform was used for structural analysis and refinement. The structural analysis was performed using the built-in olex2.solve program and the charge-flipping method to solve for the initial phase. The structural refinement was performed using its XL refinement package, and the atomic parameters and structure factor were optimized using the least squares method.

[0045] The crystal structure, principal unit cell parameters, partial bond lengths, and bond angles of Zn-TIB-BDC crystals were obtained by single-crystal X-ray diffraction (SC-XRD). The principal unit cell parameters of Zn-TIB-BDC crystals are shown in Table 1, partial bond lengths are shown in Table 2, partial bond angles are shown in Table 3, and the crystal structure is as follows: Figure 2 As shown. The XRD pattern obtained from simulation based on the resolved Zn-TIB-BDC crystal structure is shown below. Figure 3 As shown.

[0046] Table 1

[0047] Table 2

[0048] Table 3

[0049] Tables 2 and 3 Figure 2 In this system, the numbers following the element symbols are only used to distinguish the different coordination environments of the corresponding atoms; different numbers indicate that the corresponding atoms are in different coordination environments. For example, O1 and O3 represent O atoms in different coordination environments, and N1 and N6 represent N atoms in different coordination environments.

[0050] Single-crystal X-ray diffraction analysis results indicate that the Zn-TIB-BDC crystal belongs to the monoclinic crystal system. P 21 / c space group; its central metal is Zn 2+ The ion coordinates with two N atoms from two TIB ligands and two O atoms from two BDC ligands, forming a distorted tetrahedral geometry.

[0051] (3) Powder X-ray diffraction (PXRD) was performed on the Zn-TIB-BDC crystal.

[0052] PXRD conditions: Device: Anton Paar XRDynamic 500; X-rays used: Cu-Kα rays; Strength: 40 kV, 30 mA; Angle: 2θ = 5~50°; Scanning speed: 5 ° / min.

[0053] PXRD of Zn-TIB-BDC crystals as follows Figure 3 As shown.

[0054] Figure 3The results show that characteristic peaks are present at least at diffraction angles of 2θ = 6.1 ± 0.2°, 10.1 ± 0.2°, 12.2 ± 0.2°, 14.3 ± 0.2°, 15.1 ± 0.2°, 17.2 ± 0.2°, 18.4 ± 0.2°, 20.5 ± 0.2°, 25.7 ± 0.2°, and 27.7 ± 0.2°.

[0055] contrast Figure 3 The two curves show that the positions and relative intensities of the diffraction peaks are basically consistent. This indicates that the true structure of the Zn-TIB-BDC crystal is consistent with the structure obtained from the analysis.

[0056] (4) The Zn-TIB-BDC crystal was subjected to infrared spectroscopy (FT-IR).

[0057] FT-IR measurement conditions: Instrument: Perkinelmer Spectrum Two; Scanning range: 400~4000 cm -1 ; Resolution: 4 cm -1 ; Number of scans: 64; ATR method (diamond crystal).

[0058] FT-IR of Zn-TIB-BDC crystals, such as Figure 4 As shown.

[0059] like Figure 4 As shown, at approximately 1600 cm -1 The absorption peak that appears is -COO - The stretching vibration peak, while at 600 cm⁻¹ -1 With 450 cm -1 The absorption peaks that appeared were stretching vibration peaks of Zn-N bonds and Zn-O bonds, respectively, indicating that Zn was successfully coordinated with N in TIB and O in BDC.

[0060] Example 2 0.2 mmol of zinc nitrate hexahydrate, 0.1 mmol of 1,3,5-triimidazolebenzene, and 0.2 mmol of terephthalic acid were weighed and added to a 25 mL beaker. Then, 9 mL of distilled water was added to the beaker, and the beaker was sonicated for 15 min to fully dissolve the zinc nitrate hexahydrate, obtaining a suspension. The suspension was transferred to a 25 mL polytetrafluoroethylene (PTFE) liner, which was then transferred to a high-pressure reactor. The reactor was placed in an oven at 135 °C for 72 h, and finally cooled to room temperature at a rate of 5 °C / h to obtain orange-yellow crystals. These orange-yellow crystals were named Zn-TIB-BDC crystals.

[0061] Example 3 0.2 mmol of zinc nitrate hexahydrate, 0.1 mmol of 1,3,5-triimidazolebenzene, and 0.2 mmol of terephthalic acid were weighed and added to a 25 mL beaker. Then, 9 mL of distilled water was added to the beaker, and the beaker was sonicated for 15 min to obtain a suspension. The suspension was transferred to a 25 mL polytetrafluoroethylene (PTFE) liner, which was then transferred to a high-pressure reactor. The reactor was placed in an oven at 145 °C for 72 h, and finally cooled to room temperature at a rate of 5 °C / h to obtain orange-yellow crystals. These orange-yellow crystals were named Zn-TIB-BDC crystals.

[0062] Example 4 0.2 mmol of zinc nitrate hexahydrate, 0.1 mmol of 1,3,5-triimidazolebenzene, and 0.2 mmol of terephthalic acid were weighed and added to a 25 mL beaker. Then, 9 mL of distilled water was added to the beaker, and the beaker was sonicated for 15 min to obtain a suspension. The suspension was transferred to a 25 mL polytetrafluoroethylene (PTFE) liner, which was then transferred to a high-pressure reactor. The reactor was placed in an oven at 140 °C for 66 h, and finally cooled to room temperature at a rate of 5 °C / h to obtain orange-yellow crystals. These orange-yellow crystals were named Zn-TIB-BDC crystals.

[0063] Example 5 0.2 mmol of zinc nitrate hexahydrate, 0.1 mmol of 1,3,5-triimidazolebenzene, and 0.2 mmol of terephthalic acid were weighed and added to a 25 mL beaker. Then, 9 mL of distilled water was added to the beaker, and the beaker was sonicated for 15 min to obtain a suspension. The suspension was transferred to a 25 mL polytetrafluoroethylene (PTFE) liner, which was then transferred to a high-pressure reactor. The reactor was placed in an oven at 140 °C for 60 h, and finally cooled to room temperature at a rate of 5 °C / h to obtain orange-yellow crystals. These orange-yellow crystals were named Zn-TIB-BDC crystals.

[0064] The appearance, cell parameters, powder X-ray diffraction (PXRD), and infrared spectrum (FT-IR) of the Zn-TIB-BDC crystals prepared in Examples 2-5 were consistent with those of the Zn-TIB-BDC crystals prepared in Example 1.

[0065] Comparative Example 1 0.05 mmol of zinc nitrate hexahydrate and 0.1 mmol of 1,3,5-triimidazolebenzene were weighed and added to a 25 mL beaker. 8 mL of distilled water was then added to the beaker, and the beaker was sonicated for 15 min to obtain a suspension. The suspension was transferred to a 25 mL polytetrafluoroethylene (PTFE) liner, which was then transferred to a high-pressure reactor. The reactor was placed in an oven at 140 °C for 48 h, and finally cooled to room temperature at a rate of 5 °C / h to obtain a white precipitate, Zn-TIB.

[0066] Experimental Example 1 Photocatalytic CO2 reduction experiment 1) Experimental group First, 2 mg of Zn-TIB-BDC crystals prepared in Example 1 were added as photocatalysts to a quartz photocatalytic reactor. Then, 15 mL of distilled water and 5 mL of triethanolamine were added. After coating the reactor with vacuum grease, it was connected to the photocatalytic instrument. A vacuum pump was used to create a sealed environment, and a circulating condenser was activated to maintain the temperature at 5°C. High-purity CO2 gas at 88 kPa was introduced into the reactor, and the stirrer and the plunger pump of the photocatalytic instrument were turned on to allow the photocatalyst and solution in the reaction system to fully adsorb CO2 molecules. A xenon lamp was used as the light source, and the light radiation time was 4 h. Samples were automatically taken every 20 min, and the products were analyzed using the FID detector of a Fuli 7970Ⅱ gas chromatograph. The product composition was determined by retention time (7 min for CO), and the CO yield was calculated using a standard curve obtained from a standard gas mixture. A curve was plotted with time on the x-axis and CO production on the y-axis, as shown below. Figure 5 As shown in (a).

[0067] from Figure 5 As can be clearly seen in (a), the amount of CO generated increases significantly with increasing reaction time; the CO generation rate (average rate over 4 hours) is 302.87 µmol / (g·h). This result fully demonstrates that the Zn-TIB-BDC of the present invention, as a photocatalyst, can efficiently catalyze the reduction of CO2 to CO.

[0068] 2) Control group 1 The difference from the experimental group is that no photocatalyst Zn-TIB-BDC was added.

[0069] A curve was plotted with time on the x-axis and CO generation on the y-axis, as shown below. Figure 5 As shown in (b).

[0070] from Figure 5As can be clearly seen in (b), the amount of CO generated increases slowly with the increase of reaction time; the CO generation rate (average rate over 4 hours) is 2.39 µmol / (g·h).

[0071] Compare Figure 5 (a) and (b) show that the CO generation rate of the experimental group (using the Zn-TIB-BDC of the present invention as a photocatalyst) is much higher than that of the control group 1 (without catalyst), which further confirms that the Zn-TIB-BDC of the present invention has the ability to efficiently catalyze the reduction of CO2 to CO.

[0072] 3) Control group 2 The difference from the experimental group was that Zn-TIB prepared in Comparative Example 1 was added as a photocatalyst.

[0073] A curve was plotted with time on the x-axis and CO generation on the y-axis, as shown below. Figure 5 As shown in (c).

[0074] from Figure 5 As can be clearly seen in (c), the amount of CO generated increases slowly with the increase of reaction time; the CO generation rate (average rate over 4 hours) is 106.07 µmol / (g·h).

[0075] Compare Figure 5 (a) and (c) show that the CO generation rate of the experimental group (using the Zn-TIB-BDC of the present invention as a photocatalyst) is much higher than that of the control group 2 (using the Zn-TIB prepared in Comparative Example 1 as a photocatalyst). This further confirms that the Zn-TIB-BDC of the present invention has the ability to efficiently catalyze the reduction of CO2 to CO.

[0076] Experiment Example 2 Photocatalytic performance cycle stability test The difference between this experiment and the one in the photocatalytic CO2 reduction experiment is that the same photocatalyst used previously is used in each cycle. "One cycle" refers to using the Zn-TIB-BDC crystals remaining from the previous cycle as the photocatalyst. The CO generation rate (average rate over 4 hours) for cycles 1-5 is shown below. Figure 6 As shown. Figure 6 The horizontal axis represents the number of cycles, and the vertical axis represents the CO generation rate.

[0077] from Figure 6 It can be clearly seen that the CO generation rate did not decrease significantly in the five cycles, indicating that Zn-TIB-BDC crystals, as a photocatalyst, have good cycle stability.

[0078] Experimental Example 3 Turnover and Turnover Frequency Turnover number (TON) and turnover frequency (TOF) are used to characterize the cumulative ability of each catalyst molecule (Zn-TIB-BDC crystal) to generate the target product CO within a certain time and the catalytic activity per unit time, respectively. In Experimental Example 3 of this application, TON and TOF are calculated according to the following formulas: TON = n(amount of CO produced) / n(amount of Zn-TIB-BDC crystal) TOF = TON / t (reaction time).

[0079] The turnover number (TON) and turnover frequency (TOF) of the experimental group in Experiment Example 1 are shown in Table 4.

[0080] Table 4

[0081] As shown in Table 4, the TON and TOF of the Zn-TIB-BDC crystal are 0.735 and 0.184 h, respectively. -1 This indicates that Zn-TIB-BDC crystals have a certain catalytic ability and exhibit good intrinsic catalytic activity in the photocatalytic reduction of CO2 to CO process.

Claims

1. A Zn-TIB-BDC crystal with the chemical formula C 27 H 21 N6O7Zn.

2. The Zn-TIB-BDC crystal as described in claim 1, characterized in that, Its powder X-ray diffraction has characteristic peaks at least at diffraction angles of 2θ = 10.1 ± 0.2°, 12.2 ± 0.2°, 17.2 ± 0.2°, 18.4 ± 0.2° and 27.7 ± 0.2°.

3. The Zn-TIB-BDC crystal as described in claim 1, characterized in that, Its powder X-ray diffraction has characteristic peaks at least at diffraction angles of 2θ = 6.1 ± 0.2°, 14.3 ± 0.2°, 15.1 ± 0.2°, 20.5 ± 0.2° and 25.7 ± 0.2°.

4. The Zn-TIB-BDC crystal as described in claim 1, characterized in that, It belongs to the monoclinic crystal system. P 21 / c space group; Its unit cell parameters include: a=14.4653 Å, b=7.8332 Å, c=22.604 Å, α=90°, β=91.759°, γ=90°.

5. The Zn-TIB-BDC crystal as described in claim 1, characterized in that, It is produced by reacting zinc nitrate hexahydrate, 1,3,5-triimidazolylbenzene and terephthalic acid.

6. A method for preparing a Zn-TIB-BDC crystal as described in any one of claims 1-5, comprising: The raw materials, including zinc nitrate hexahydrate, 1,3,5-triimidazolebenzene and terephthalic acid, are subjected to a hydrothermal reaction.

7. The preparation method according to claim 6, comprising: 1) Mix zinc nitrate hexahydrate, 1,3,5-triimidazolebenzene, terephthalic acid and distilled water to form a suspension; 2) To induce a hydrothermal reaction in the suspension; 3) After the hydrothermal reaction is complete, cool down to room temperature.

8. The preparation method according to claim 7, comprising: The molar ratio of zinc nitrate hexahydrate, 1,3,5-triimidazolylbenzene, and terephthalic acid is (2±0.2):1:(2±0.2); or / and, The hydrothermal reaction temperature is 130~160 ℃; or / and, The hydrothermal reaction time is 48 hours or more; or / and, The cooling rate is 1~10 ℃ / h.

9. A photocatalyst for photocatalytic CO2 reduction, comprising Zn-TIB-BDC crystal as described in any one of claims 1-5 or Zn-TIB-BDC crystal prepared by the preparation method as described in any one of claims 6-8.

10. The application of the photocatalyst as described in claim 9 in the field of photocatalytic CO2 reduction.

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