Preparation method and application of NH2-UiO-66 (Zr / Ce)@BNMFs composite material

Abstract

The application discloses a preparation method and application of an NH2-UiO-66(Zr / Ce)@BNMFs composite material. Zr ions and Ce ions are first anchored on prepared BNMFs in DMF, then a DMF solution of NH2-BDC is added, stirring is carried out, then the mixed solution is transferred into a high-pressure kettle inner container, and the NH2-UiO-66(Zr / Ce)@BNMFs composite material is obtained through a solvothermal method, and the best ratio is obtained by changing the amount of BNMFs. Through a photocatalytic process, the application can efficiently reduce CO2 into valuable chemical substances such as CO, CH4 and H2, and exhibits significant photocatalytic activity.

Description

Technical Field

[0001] This invention relates to the fields of composite material preparation and photocatalysis technology, and in particular to a method for synthesizing and applying a high-efficiency NH2-UiO-66(Zr / Ce)@BNMFs composite material for photocatalytic reduction of CO2. Background Technology

[0002] With the acceleration of industrialization and the continuous consumption of fossil fuels, the concentration of carbon dioxide (CO2) in the atmosphere is constantly rising, posing a serious threat to the global climate and ecological environment. To address this challenge, reducing CO2 emissions and exploring efficient utilization pathways have become a hot topic in scientific research and industry. Photocatalysis technology, with its unique advantages of being solar-powered, environmentally friendly, and producing high-value-added products, shows great potential in the field of CO2 emission reduction and conversion.

[0003] UiO-66, as a type of metal-organic framework (MOF) material, has broad application prospects in gas adsorption and catalysis due to its high stability, high porosity, and tunable structure. However, the original UiO-66 has limitations in photocatalytic CO2 reduction, such as a limited light absorption range, a wide band gap, and low photogenerated carrier separation efficiency. These shortcomings limit its efficiency in practical applications.

[0004] To overcome the aforementioned drawbacks of UiO-66, researchers have explored various modification strategies, including ligand functionalization, selection of functional metal nodes, defect engineering, and composite with other photocatalytically active semiconductors. These modification methods aim to improve the CO2 adsorption performance, light absorption performance, and photogenerated electron-hole separation efficiency of UiO-66, thereby enhancing its photocatalytic activity for CO2 reduction.

[0005] The products of photocatalytic reduction of CO2 include C1 compounds such as CO, methane, methanol, ethanol, formaldehyde, and formic acid, which have wide applications in energy, chemical, and other fields. Among these, CO, as an important intermediate product, can be used in processes such as Fischer-Tropsch synthesis to produce fuels, possessing extremely high industrial value. Therefore, developing efficient and highly selective photocatalysts is of great significance for realizing the industrial application of photocatalytic CO2 reduction.

[0006] Since Garcia et al. discovered in 2010 that UiO-66 can produce hydrogen under ultraviolet light irradiation, it has been extensively studied (Gomes Silva C, Luz I, Llabres i Xamena FX, et al. Chemistry-A European Journal, 2010, 16, 11133-11138.). Although UiO-66 exhibits photoresponsiveness, it is only responsive under ultraviolet light, meaning its catalytic performance is not superior to conventional semiconductor materials. Therefore, to improve the photocatalytic performance of UiO-66, researchers have modified it. In 2015, Sun et al. successfully prepared Ti-substituted UiO-66-NH2 (Zr / Ti) (D.Sun, W.Liu, M.Qiu, Y.Zhang, Z.Li. Chemical Communications 2015, 51, 2056-2059), which exhibited stronger CO2 reduction under visible light (5.8 mmol·mol⁻¹ for 10 h). -1 ) and hydrogen production (9h 3.5mmol·mol) -1 In contrast, using UiO-66-NH2 as a photocatalyst resulted in relatively weak CO2 reduction (3.4 mmol·mol⁻¹). -1 ) and hydrogen production (2.4 mmol·mol -1 The activity indicates that Ti doping improves the photocatalytic reduction performance of CO2, but the photogenerated electron-hole separation efficiency is not high, which is not conducive to the photocatalytic reduction of CO2. The paper "Preparation Method and Application of Cerium-Doped NH2-UiO-66 / Indium Cadmium Sulfide Composite Photocatalyst for CO2 Reduction" (ZL 202310388785.3) describes the preparation of a cerium-doped NH2-UiO-66 / indium cadmium sulfide composite photocatalyst via a hydrothermal method. Although this method improves the photogenerated electron-hole separation efficiency, the photocatalytic reduction performance of CO2 is still not high (6 μmol·g-1·h-1). To further improve the photocatalytic reduction performance of CO2, the CO2 adsorption and activation performance of the catalyst can also be improved. Therefore, it is necessary to prepare a composite photocatalyst with higher CO2 adsorption and activation performance. Summary of the Invention

[0007] To address the low CO2 adsorption performance in current photocatalytic CO2 reduction technologies, this invention proposes a method for preparing and applying an NH2-UiO-66(Zr / Ce)@BNMFs composite material. The method involves first anchoring Zr and Ce ions onto prepared BNMFs in DMF, then adding an NH2-BDC DMF solution, stirring, and transferring the mixture to an autoclave liner. The NH2-UiO-66(Zr / Ce)@BNMFs composite material is obtained via a solvothermal method. The optimal ratio is achieved by adjusting the amount of BNMFs used. This invention efficiently reduces CO2 to valuable chemical substances such as CO, CH4, and H2 through a photocatalytic process, exhibiting significant photocatalytic activity.

[0008] The technical solution of this invention is:

[0009] A method for preparing an NH2-UiO-66(Zr / Ce)@BNMFs composite material, the method comprising the following steps:

[0010] Step 1: Add the prepared BNMFs to NN dimethylformamide (DMF), denoted as solution A. Sonicate at 15-25℃ for 25-50 min to ensure that the BNMFs are evenly dispersed in the DMF. Then add glacial acetic acid, followed by chloride salt. Stir at 20-25℃ for 5-10 min to obtain suspension A with the central metal atom anchored on the BNMFs.

[0011] For every 15 ml of DMF, add 1-3 mmol of BNMFs, 2-4 ml of glacial acetic acid, and 1-3 mmol of chloride salt.

[0012] The chloride salts mentioned are ZrCl4 and CeCl3, with a molar ratio of ZrCl4:CeCl3 = 1:1;

[0013] Step 2: Add diaminoterephthalic acid (NH2-BDC) to DMF and sonicate at 15-25℃ for 5-10 min to disperse NH2-BDC in DMF, and denote it as solution B;

[0014] For every 15 ml of DMF, 1-3 mmol of NH2-BDC is added;

[0015] Step 3: Add solution B dropwise to suspension A and stir at 15-25℃ for 30-60 minutes to obtain a mixture;

[0016] Wherein: the molar ratio of chloride salt in suspension A to NH2-BDC in solution B is 1:1;

[0017] Step 4: Transfer the mixture to an autoclave, seal it, and keep it at 115-125℃ for 20-26 hours. Finally, let it cool naturally to room temperature to obtain the NH2-UiO-66(Zr / Ce)@BNMFs composite material.

[0018] Purification of the NH2-UiO-66(Zr / Ce)@BNMFs composite material: Centrifuge the reaction product, wash with DMF and methanol 3-5 times each, and then dry at 70-80℃ for 20-30h.

[0019] The centrifugation speed is 10000-11000 r / min, and the centrifugation time is 2-3 min.

[0020] The NH2-UiO-66(Zr / Ce)@BNMFs composite material obtained by the method is used for photocatalytic reduction of CO2 to produce CO.

[0021] Specifically, the steps include: placing the NH2-UiO-66(Zr / Ce)@BNMFs composite material and deionized water into a quartz reactor, sealing it, and irradiating it with a light source for 5-7 hours under a CO2 atmosphere to obtain CO;

[0022] Among them, 25-40 mg of NH2-UiO-66(Zr / Ce)@BNMFs composite material is added to every 10 mL of deionized water;

[0023] The light source is sunlight or xenon lamp.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. In the composite material prepared by this invention, the particle size of NH2-UiO-66 (Zr / Ce) is reduced from 303 nm to 85.7 nm, and the aggregation phenomenon between NH2-UiO-66 (Zr / Ce) molecules is alleviated, such as... Figure 3 This is beneficial for CO2 adsorption and activation. In addition, the NH2-UiO-66 (Zr / Ce) grown on BNMFs is very uniformly arranged, and there is a clear interface between the two components, which is conducive to electron transfer.

[0026] 2. The NH2-UiO-66(Zr / Ce)@BNMFs composite material synthesized in this invention not only improves the CO2 adsorption and activation performance of the catalyst, but also... Figure 7 The composite material exhibits a CO2 adsorption capacity of 50.15 cc / g, which is superior to conventional materials, and the two components are also constructed as a heterojunction. This also promotes the efficiency of photogenerated electron-hole separation, such as... Figure 6 The photocurrent density of the composite material is 4 times that of NH2-UiO-66(Zr / Ce).

[0027] 3. The photocatalytic CO2 reduction performance of the NH2-UiO-66(Zr / Ce)@BNMFs composite material synthesized in this invention shows a CO yield of 216 μmol·g⁻¹ after 6 hours. The photocatalytic CO2 reduction performance of the NH2-UiO-66(Zr / Ce)@BNMFs composite material synthesized in this invention is higher than that of the photocatalytic CO2 reduction performance of the photocatalyst prepared in patent ZL 202310388785.3. Furthermore, based on the comparison of synthesis methods, this invention uniformly disperses NH2-UiO-66(Zr / Ce) on the surface of BNMFs, which makes the light absorption performance of the composite photocatalyst approach that of NH2-UiO-66(Zr / Ce). In contrast, the composite photocatalyst prepared by patent ZL 202310388785.3 coats NH2-UiO-66(Zr / Ce). Therefore, the composite photocatalyst prepared by this invention has better applicability than the photocatalyst prepared by patent ZL 202310388785.3. Attached Figure Description

[0028] Figure 1 X-ray diffraction patterns of the photocatalysts prepared in Examples 1, 2, 3 and 4;

[0029] Figure 2 Infrared spectra of the photocatalysts prepared in Examples 1, 2, 3 and 4;

[0030] Figure 3 SEM images of the photocatalysts prepared in Examples 1, 2, 3 and 4, and average particle size distribution of NH2-UiO-66 (Zr / Ce) in the catalysts prepared in Examples 1 and 3;

[0031] Figure 4 The bar chart shows the yields of the photocatalysts prepared in Examples 1, 2, 3 and 4 in simulated sunlight photocatalytic reduction of CO2 to H2, CO and CH4.

[0032] Figure 5 The bar chart shows the cyclic stability of the photocatalyst prepared in Example 1 in simulated sunlight photocatalytic reduction of CO2 to produce H2, CO and CH4.

[0033] Figure 6 Transient photocurrent response diagrams of the photocatalysts prepared in Examples 1, 2, 3 and 4;

[0034] Figure 7 The images show the CO2 adsorption isotherms of the photocatalysts prepared in Examples 1, 3, and 4. Detailed Implementation

[0035] The present invention will be further explained below with reference to the embodiments and accompanying drawings.

[0036] Example 1

[0037] Step 1: Add 2 mmol of the prepared BNMFs to NN dimethylformamide (DMF), and denote it as solution A. Sonicate at 25°C for 30 min to ensure that the BNMFs are evenly dispersed in the DMF. Next, add 3 ml of glacial acetic acid to solution A. Then, take an appropriate amount of ZrCl4 and CeCl3 and add them to solution A. Finally, stir at 25°C for 10 min.

[0038] The amount of DMF used was 15 ml, the total amount of ZrCl4 and CeCl3 was 2 mmol, and the molar ratio of ZrCl4 to CeCl3 was 1:1.

[0039] Step 2: Add diaminoterephthalic acid (NH2-BDC) to DMF, denoted as solution B, and sonicate at 25°C for 5 minutes to ensure that NH2-BDC is evenly dispersed in DMF.

[0040] The amount of DMF used was 15 ml, and the amount of NH2-BDC used was 2 mmol.

[0041] Step 3: Add solution B dropwise to solution A and stir at 25°C for 45 minutes to obtain a mixture.

[0042] Step 4: Remove the magnetic spool, transfer the mixture to the inner liner of the autoclave, transfer the inner liner of the autoclave to the autoclave, place the autoclave in an oven at 120°C for 24 hours, remove it, and allow it to cool naturally to room temperature to obtain the reaction product.

[0043] Step 5: Centrifuge the reaction product, wash it three times each with DMF and methanol, and transfer the washed catalyst to an oven at 70°C for 24 hours to dry. The resulting catalyst is named BN(2)@U.

[0044] The centrifugation speed was 10000 r / min and the centrifugation time was 2 min.

[0045] Example 2

[0046] The amount of BNMFs used in step 1 of Example 1 was changed to 1 mmol, and all other operations were the same as in Example 1. The resulting catalyst was named BN(1)@U.

[0047] Example 3

[0048] The amount of BNMFs used in Example 1 was changed to 0 mmol, and all other operations were the same as in Example 1. The resulting catalyst was named NH2-UiO-66(Zr / Ce).

[0049] Example 4

[0050] (1) Take 12.60g of melamine (C3N6H6) and 18.56g of boric acid (H3BO3), and disperse them in a beaker containing 1000ml of deionized water. First, place the beaker in a water bath at 90℃ and stir for 3 hours. After the water bath temperature drops to 80℃, turn off the stirring and keep it at 80℃ for 6 hours. Finally, turn off the power to the water bath and allow the beaker to cool naturally to room temperature. White flocculent matter was observed to precipitate. The white flocculent matter was separated by filtration and washing with deionized water, and then transferred to a 70℃ oven to dry for 12 hours to obtain melamine diboronic acid (MB2).

[0051] (2) MB2 was placed in a ceramic boat, which was then placed in a tube furnace. The tube furnace parameters were set as follows: heating from room temperature to 1100℃ at a heating rate of 5℃ / min, holding at 1100℃ for 4 hours, and then cooling to room temperature at a cooling rate of 10℃ / min. To eliminate the influence of impurity gases, N2 was passed through for half an hour before running the program, and the program was finally run under an N2 atmosphere to obtain white BNMFs powder.

[0052] 1. Composition determination of NH2-UiO-66(Zr / Ce)@BNMFs composite material

[0053] The photocatalysts prepared in Examples 1, 2, 3, and 4 were analyzed using a Da Vinci X-ray Powder Diffraction (XRD) system from Bruker AXS GmbH, Germany. This instrument used a copper target with Kα rays (λ = 1.54056), a scan rate of 6° / min, a scan range of 5–50°, a voltage of 40 kV, and a current of 150 mA. The X-ray spectra are shown below. Figure 1 As shown: BNMFs exhibit two typical broad diffraction peaks at 2θ (24.5° and 42.6°), corresponding to the (002) and (100) crystal planes of h-BN, respectively. The broadening of the diffraction peaks indicates that BNMFs have low crystallinity and a large number of defects. These defects may provide active sites for photocatalytic reactions, thus contributing to the photocatalytic reduction of CO2. The characteristic peaks at 2θ (7.3° and 8.4°) correspond to the (111) and (200) crystal planes of NH2-UiO-66(Zr / Ce), respectively. The presence of characteristic peaks of BNMFs and NH2-UiO-66(Zr / Ce) in the XRD pattern of the BN@U composite material indicates the successful preparation of the BN@U composite material. Because of the poor crystallinity of BNMFs, the characteristic peaks are masked in the XRD pattern of the composite material.

[0054] 2. Infrared spectroscopy of NH2-UiO-66(Zr / Ce)@BNMFs composite photocatalyst

[0055] The photocatalysts prepared in Examples 1, 2, 3, and 4 were analyzed for chemical bonds and functional groups using a Bruker VECTOR22 Fourier Transform Infrared Spectroscopy (FT-IR) instrument. The infrared spectra are shown below. Figure 2 As shown: For BNMFs, 1392cm - The absorption peak at 801 cm⁻¹ is due to the BN stretching vibration within the BNMFs plane. - The absorption peak at 1 cm⁻¹ corresponds to the out-of-plane BNB bending vibration of BNMFs. The presence of these two absorption peaks confirms the synthesis of BNMFs. For NH₂-UiO₆₆(Zr / Ce), the peak at 667 cm⁻¹ corresponds to the out-of-plane BNB bending vibration of BNMFs. -1 and 482cm -1 The absorption peaks at 771 cm⁻¹ correspond to Zr-O and Ce-O bonds in the metal clusters of the sample, respectively. -1 The nearby vibrational peak corresponds to the C=C bond of the benzene ring in the ligand. 1635 cm⁻¹ -1 and 1255cm -1 The absorption peaks at 1560 cm⁻¹ correspond to the bending vibration of NH₃ and the stretching vibration of CN₂, respectively, proving the successful introduction of -NH₂. -1 and 1395cm -1 The absorption peaks at 3750-3250 cm⁻¹ correspond to the asymmetric and symmetric stretching vibrations of the carboxylic acid group, respectively. -1 The broad peak at 1392 cm⁻¹ corresponds to the stretching vibration of hydroxyl groups in water molecules adsorbed in the pores of NH₂-UiO₆₆(Zr / Ce). BN@U exhibits absorption peaks from both BNMFs and NH₂-UiO₆₆(Zr / Ce), indicating successful composite formation. Furthermore, the BN@U composite material shows an absorption peak at 1392 cm⁻¹. - 1 and 801cm - The absorption peak at position 1 also increases with the increase of BNMF content.

[0056] 3. SEM testing of NH2-UiO-66(Zr / Ce)@BNMFs composite photocatalyst

[0057] The photocatalysts prepared in Examples 1, 2, 3, and 4 were subjected to microscopic morphology testing using a field-emission scanning electron microscope (SEM) from FEI Corporation, USA. The test results are as follows: Figure 3 As shown, the average particle size of the photocatalyst was statistically analyzed using Nano Measurer software.

[0058] like Figure 3As shown in (a) and (e), NH2-UiO-66(Zr / Ce) exhibits a decussated octahedral morphology with an average particle size of 303 nm; Figure 3 As shown in Figure (b), the morphology of BNMFs is fibrous with a smooth surface and a diameter of several micrometers; the SEM images of BN(1)@U and BN(2)@U are shown in Figures (b). Figure 3 As shown in (c) and (d), the SEM images reveal that the NH2-UiO-66(Zr / Ce) on the BN(1)@U surface is sparsely arranged and still exhibits agglomeration, while the NH2-UiO-66(Zr / Ce) on BN(2)@U is tightly arranged with little agglomeration. After NH2-UiO-66(Zr / Ce) is combined with BNMFs, the average particle size of NH2-UiO-66(Zr / Ce) decreases, especially in BN(2)@U, where the average particle size of NH2-UiO-66(Zr / Ce) is approximately 85.7 nm. Figure 3 (f) This is because BNMFs, acting as a support, enhance the dispersion of NH2-UiO-66(Zr / Ce), forming small particles of NH2-UiO-66(Zr / Ce). Small particles often have more exposed active sites, which is beneficial for the photocatalytic reduction of CO2. Furthermore, we observed that the NH2-UiO-66(Zr / Ce) grown on BNMFs are very uniformly arranged, and there is a clear interface between the two components, which is conducive to electron transfer.

[0059] 4. Bar chart showing the yield of NH2-UiO-66(Zr / Ce)@BNMFs composite photocatalyst in simulated sunlight photocatalytic reduction of CO2 to H2, CO and CH4.

[0060] The photocatalysts prepared in Examples 1, 2, 3 and 4 were used to conduct photocatalytic reduction experiments of CO2.

[0061] The photocatalytic reduction of CO2 experiment was conducted as follows: The photocatalytic reduction performance of the catalyst was tested under uniform simulated sunlight irradiation (300W xenon lamp as the light source). The photocatalytic reaction occurred in a sealed 200ml quartz reactor, with a circulating condensate system outside the reactor to keep the photocatalytic reaction constant at room temperature.

[0062] The experimental procedure was as follows: 30 mg of catalyst and 10 ml of deionized water were placed in a quartz reactor. In order to eliminate the influence of impurity gases, the sealed quartz reactor was evacuated and backfilled with high-purity CO2. After 6 hours of simulated sunlight irradiation, the generated gaseous products were analyzed by GC.

[0063] The results of photocatalytic reduction of CO2 are as follows Figure 4As shown, after 6 h of photocatalysis, the CO yield of BNMFs was 23 μmol·g⁻¹, and the CO yield of NH₂-UiO₆₆(Zr / Ce) was 180 μmol·g⁻¹. -1 The catalytic performance was improved when BNMFs were combined with NH2-UiO-66(Zr / Ce). In particular, BN(2)@U achieved a CO yield of 216 μmol·g⁻¹, which is 9.3 times that of BNMFs and 1.2 times that of NH2-UiO-66(Zr / Ce). The CO yield of BN(1)@U was nearly identical to that of NH2-UiO-66(Zr / Ce), at 171 μmol·g⁻¹. -1 The possible reasons are: (1) the amount of BNMFs used is small, resulting in low composite material yield; (2) the contact area between NH2-UiO-66(Zr / Ce) and BNMFs is small, which reduces the electron transfer efficiency between materials. In addition, NH2-UiO-66(Zr / Ce) still shows agglomeration on the surface of BNMFs. This indicates that using a small amount of BNMFs during composite material synthesis will not improve the photocatalytic reduction performance of CO2. Therefore, introducing an appropriate amount of BNMFs can effectively enhance the photocatalytic reduction performance of NH2-UiO-66(Zr / Ce) for CO2.

[0064] 5. Bar chart showing the cyclic stability of the NH2-UiO-66(Zr / Ce)@BNMFs composite photocatalyst in simulated sunlight photocatalytic reduction of CO2 to H2, CO, and CH4.

[0065] The photocatalyst prepared in Example 1 was used for photocatalytic reduction of CO2. After 6 hours, the catalyst was centrifuged and dried, then redistributed into a new reaction system for testing. The process was repeated 5 times to obtain a bar chart of cyclic stability. Figure 5 The BN(2)@U shown has good cyclic stability.

[0066] 6. Transient and steady-state photocurrent response diagrams of NH2-UiO-66(Zr / Ce)@BNMFs composite photocatalysts

[0067] The photocatalysts prepared in Examples 1, 2, 3, and 4 were tested for transient and steady-state photocurrent responses using an electrochemical workstation. The test results are as follows: Figure 6 As shown:

[0068] The transient photocurrent responses of BN@U, BNMFs, and NH2-UiO-66(Zr / Ce) are as follows: Figure 6As shown, BN(2)@U exhibits the highest transient photocurrent response, approximately 3.5 times that of NH2-UiO-66(Zr / Ce). This indicates that BN(2)@U can effectively separate photogenerated electron-hole pairs, thereby promoting the photocatalytic reduction of CO2. The transient photocurrent responses of BN(1)@U and NH2-UiO-66(Zr / Ce) are nearly identical, which corresponds to the aforementioned results regarding the photocatalytic reduction of CO2.

[0069] 7. CO2 adsorption isotherm of NH2-UiO-66(Zr / Ce)@BNMFs composite photocatalyst

[0070] The CO2 adsorption properties of the photocatalysts prepared in Examples 1, 3, and 4 were analyzed using an Autosorb iQ fully automated physicochemical adsorption instrument from Quantachrome Instruments.

[0071] Test method: Take 50-100 mg of sample and place it in a sample tube. Then, degas at 120℃ for 12 hours to remove small molecule impurities from the sample surface. After degassing, test at -196℃. Test results are as follows. Figure 7 As shown.

[0072] Because NH2-UiO-66(Zr / Ce) has a large number of regular pores, it can adsorb a large amount of CO2 (57.35 cc / g). However, the pores of BNMFs are irregular, so the CO2 adsorption performance of BNMFs is less than that of NH2-UiO-66(Zr / Ce). The CO2 adsorption capacity of BNMFs is 30.6 cc / g. Since BNMFs has a large number of Lewis bases, it can adsorb a large amount of CO2. Therefore, the CO2 adsorption performance of the sample after BNMFs is combined with NH2-UiO-66(Zr / Ce) is slightly reduced. The CO2 adsorption capacity of BN(2)@U is 50.15 cc / g. The increase in CO2 adsorption capacity of the photocatalyst enables the catalyst to activate CO2 molecules before the photocatalytic reduction of CO2 begins, thereby promoting the photocatalytic reduction performance of CO2.

[0073] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

[0074] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing NH2-UiO-66-Zr / Ce@BNMFs composite material for photocatalytic reduction of CO2 to CO, characterized in that the method includes the following steps: Step 1: Take 12.60 g of melamine (C3N6H6) and 18.56 g of boric acid (H3BO3), and disperse them in a beaker containing 1000 mL of deionized water. First, place the beaker in a 90 ℃ water bath and stir for 3 h. After the water bath temperature drops to 80 ℃, turn off the stirring and keep it at 80 ℃ for 6 h. Finally, turn off the power to the water bath and let the beaker cool naturally to room temperature. White flocculent matter was observed to precipitate. The white flocculent matter was separated by filtration and washing with deionized water, and then transferred to a 70 ℃ oven to dry for 12 h to obtain melamine diboronic acid (MB2). Place MB2 in a ceramic boat, and then place the ceramic boat in a tube furnace. Set the tube furnace parameters as follows: heat from room temperature to 1100 ℃ at a heating rate of 5 ℃ / min, and hold at 1100 ℃ for 4 h. h, and then cooled to room temperature at a rate of 10℃ / min; to eliminate the influence of impurity gases, N2 was passed through for half an hour before running the program, and finally the program was run under N2 atmosphere to obtain white BNMFs powder. Step 2: Add the prepared BNMFs to N,N-dimethylformamide DMF, and label it solution A. Sonicate at 15-25℃ for 25-50 min, then add glacial acetic acid, followed by chloride salt. Stir at 20-25℃ for 5-10 min to obtain suspension A with the central metal atom anchored on BNMFs. in, Add 1-3 mmol of BNMFs, 2-4 mL of glacial acetic acid, and 1-3 mmol of chloride salt to every 15 mL of DMF; The chloride salts mentioned are ZrCl4 and CeCl3, with a molar ratio of ZrCl4:CeCl3=1:1; Step 3: Add diaminoterephthalic acid NH2-BDC to DMF and sonicate at 15-25℃ for 5-10 min to disperse NH2-BDC in DMF, and denote it as solution B. For every 15 mL of DMF, 1-3 mmol of NH2-BDC is added; Step 4: Add solution B dropwise to suspension A and stir at 15-25℃ for 30-60 min to obtain a mixture; Wherein: the molar ratio of chloride salt in suspension A to NH2-BDC in solution B is 1:1; Step 5: Transfer the mixture to an autoclave, seal it, and keep it at 115-125 ℃ for 20-26 h. Finally, let it cool naturally to room temperature to obtain the NH2-UiO-66-Zr / Ce@BNMFs composite material. The NH2-UiO-66-Zr / Ce@BNMFs composite material was purified by centrifugation, washing with DMF and methanol 3-5 times each, and then drying at 70-80℃ for 20-30 h. The centrifugation speed is 10000-11000 r / min, and the centrifugation time is 2-3 min.

2. The application of the NH2-UiO-66-Zr / Ce@BNMFs composite material obtained by the method as described in claim 1 for photocatalytic reduction of CO2 to CO, characterized in that it is used for photocatalytic reduction of CO2 to CO.

3. The application as described in claim 2, characterized in that it specifically includes the following steps: placing the NH2-UiO-66-Zr / Ce@BNMFs composite material and deionized water into a quartz reactor, sealing it, and irradiating it with a light source for 5-7 hours under a CO2 atmosphere to obtain CO; in, Add 25-40 mg of NH2-UiO-66-Zr / Ce@BNMFs composite material to every 10 mL of deionized water; The light source is sunlight or xenon lamp.

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