Preparation method and application of three-dimensional macroscopic body MOF-808 / RGO / Ag-Ni composite photocatalyst

Abstract

The application belongs to the technical field of resources and environment, and particularly relates to a preparation method and application of a three-dimensional macroscopic body MOF-808 / RGO / Ag-Ni composite photocatalyst. The application prepares a flat round macroscopic body aerogel composite photocatalyst MOF-808 / RGO / Ag-Ni. The flat round macroscopic feature increases the contact area of the catalyst and light, and is more conducive to the subsequent catalytic reaction. The introduction of RGO and Ag-Ni successfully widens the visible light absorption range of the composite photocatalyst. In addition, the Z-type heterojunction formed between MOF-808 and Ag-Ni also has an improvement in the electron transport rate compared with the MOF-808 / RGO composite photocatalyst, further improving the photocatalytic CO2 reduction activity.

Description

Technical Field

[0001] This invention belongs to the field of resource and environmental technology, specifically relating to the preparation method and application of a three-dimensional macroscopic MOF-808 / RGO / Ag-Ni composite photocatalyst. Background Technology

[0002] With the growing demand for sustainable energy and carbon emission reduction, photocatalytic CO2 reduction has emerged as a promising technology. The photocatalytic CO2 reduction process mimics natural photosynthesis, utilizing solar energy and photocatalysts to catalytically convert CO2 and H2O (also known as artificial photosynthesis). This allows for the production of solar fuels and high-value-added chemicals, such as methanol, ethanol, and hydrocarbons, under ambient temperature and pressure conditions. The core of photocatalytic CO2 reduction lies in the use of photocatalysts, which convert light energy into the energy required for the chemical reaction and promote the reduction of CO2 molecules. However, its application faces several challenges. For example, the design and synthesis of photocatalysts, the elucidation of the reaction mechanism, and the improvement of photocatalytic efficiency all require further research and exploration. Therefore, developing photocatalytic semiconductors with high activity, stability, and selectivity for CO2 reduction is crucial.

[0003] MOF-808, as a nanomaterial with a relatively high specific surface area among Zr-MOFs, has gradually attracted attention. It is well-suited for detecting and capturing / adsorbing minute concentrations of substances, purifying water or air; it can also store large amounts of energy for the manufacture of better batteries and energy storage devices. Furthermore, the synthesis method of MOF-808 is relatively simple, and it exhibits good stability under chemical and thermodynamic conditions. However, MOF-808 also has certain limitations, such as low photocatalytic activity and a limited photoresponse range, requiring further research and development. Therefore, the inventors constructed a photocatalytic material MOF-808 / RGO with a three-dimensional macroscopic aerogel structure, which possesses advantages such as high specific surface area, ease of synthesis, and high stability (https: / / doi.org / 10.1016 / j.jcis.2024.04.195). However, its catalytic activity needs further enhancement. Therefore, how to improve the photocatalytic CO2 reduction performance of MOF-808 / RGO has become a pressing technical challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to prepare a flattened, spherical macroscopic aerogel composite photocatalyst MOF-808 / RGO / Ag-Ni. The flattened, spherical macroscopic feature increases the contact area between the catalyst and light, which is more conducive to subsequent catalytic reactions. The introduction of RGO and Ag-Ni successfully broadens the visible light absorption range of the composite photocatalyst. Furthermore, the Z-shaped heterojunction formed between MOF-808 and Ag-Ni also improves the electron transport rate compared to the MOF-808 / RGO composite photocatalyst, further enhancing the photocatalytic CO2 reduction activity.

[0005] A method for developing a three-dimensional macroscopic MOF-808 / RGO or MOF-808 / RGO / Ag-Ni composite photocatalyst includes the following steps:

[0006] (1) Preparation of MOF-808 photocatalyst:

[0007] First, ZrOCl2·8H2O, C9H6O6 and DMF were stirred; formic acid was added and stirred continuously until well mixed, and the mixture was heated at 120℃; after the reaction was completed, the mixture was cooled to room temperature to obtain a white MOF-808 sample.

[0008] (2) Preparation of Ag-Ni photocatalyst

[0009] First, Ni(NO3)2 and AgNO3 were added to water and stirred until dissolved; then, NaOH aqueous solution was added and stirred continuously; next, sodium dodecyl sulfate solution was added and stirred again; hydrazine hydrate solution was added and stirred for 1 hour; the solution was heated to 160°C; after the reaction was completed, the temperature was lowered to room temperature to obtain the Ag-Ni alloy photocatalyst.

[0010] (3) Preparation of MOF-808 / Ag-Ni composite photocatalyst

[0011] First, the prepared MOF-808, Ag-Ni photocatalyst, PVP and ethanol were mixed and stirred. Then the mixture was heated to 100℃. After the reaction was completed, it was cooled to room temperature to obtain the MOF-808 / Ag-Ni composite photocatalyst.

[0012] (4) Preparation of macroscopic aerogel composite photocatalysts of MOF-808 / RGO / Ag-Ni

[0013] The GO solution was ultrasonically treated, and the MOF-808 / Ag-Ni composite photocatalyst was added. The mixture was then ultrasonicated and stirred. Ascorbic acid was added and stirred for 30 minutes. The solution was then heated at 95°C to obtain the MOF-808 / RGO / Ag-Ni hydrogel material. Finally, the MOF-808 / RGO / Ag-Ni aerogel material was obtained by freeze-drying.

[0014] A further step in the method includes the following steps:

[0015] (1) Preparation of MOF-808 photocatalyst:

[0016] First, 0.258 g ZrOCl2·8H2O, 0.056 g C9H6O6, and 12 mL DMF were added and stirred for 10 min to dissolve completely. Then, 12 mL formic acid was added and stirring was continued for 30 min. The mixture was then heated at 120 °C for 48 h. After the reaction was completed, the resulting white solution was cooled to room temperature and repeatedly washed and centrifuged with deionized water, DMF, and ethanol. Finally, the sample was dried in a vacuum drying oven at 60 °C for 24 h to obtain a white MOF-808 sample.

[0017] (2) Preparation of Ag-Ni photocatalyst

[0018] First, 0.145 g of Ni(NO3)2 and 0.085 g of AgNO3 were weighed out and added to 25 mL of deionized water, and stirred thoroughly to achieve complete dissolution. Then, 1 M NaOH aqueous solution was added and stirred continuously for 5 min. Next, 0.01 M sodium dodecyl sulfate solution was added and stirred again for 5 min. 4 mL of hydrazine hydrate solution was added and stirred for 1 hour. Then, the mixture was heated at 160 °C for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the mixture was repeatedly washed with deionized water and ethanol to remove impurities. Finally, the resulting gray-black solid was placed in a vacuum drying oven at 60 °C to obtain the Ag-Ni alloy photocatalyst.

[0019] (3) Preparation of MOF-808 / Ag-Ni composite photocatalyst

[0020] First, 100 mg of the prepared MOF-808 and 25 mg of Ag-Ni photocatalyst were added to 10 mg of PVP and 30 mL of ethanol, stirred for 30 min, heated at 100 °C for 8 h, and then the bottom solid was washed several times with deionized water and ethanol. After washing, the sample was placed in a vacuum drying oven for drying to obtain the MOF-808 / Ag-Ni composite photocatalyst. In addition, following the above steps, the amount of Ag-Ni added was adjusted to prepare MOF-808 / Ag-Ni composite photocatalysts with different ratios.

[0021] (4) Preparation of macroscopic aerogel composite photocatalysts of MOF-808 / RGO / Ag-Ni

[0022] First, a 5 mg / mL GO solution was sonicated for 6 h. Next, 5 mL of the GO solution was taken, and 50 mg of MOF-808 / Ag-Ni composite photocatalyst was added to it, followed by sonication and stirring for 1 h. Then, 30 mg of ascorbic acid was weighed, added to the solution, and stirred for 30 min. Subsequently, the precursor solution was transferred to a quartz bottle, placed in an oven, and kept at 95 °C for 3 h. This yielded the MOF-808 / RGO / Ag-Ni hydrogel material. Finally, the MOF-808 / RGO / Ag-Ni aerogel material was obtained by freeze-drying.

[0023] As an optimization method, the technical solution adopted by this invention includes the following steps:

[0024] A method for preparing a three-dimensional macroscopic MOF-808 / RGO or MOF-808 / RGO / Ag-Ni composite photocatalyst includes the following steps:

[0025] (1) Preparation of MOF-808 photocatalyst:

[0026] First, 0.258 g ZrOCl2·8H2O, 0.056 g C9H6O6, and 12 mL DMF were added to a beaker and stirred for 10 min. After observing that the white solid in the beaker had completely dissolved, 12 mL formic acid was added to the precursor solution and stirring was continued for 30 min. Then, the well-mixed solution was completely transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 48 h. After the reaction was completed, the resulting white solution was cooled to room temperature and repeatedly washed and centrifuged with deionized water, DMF, and ethanol. Finally, the sample was dried in a vacuum drying oven at 60 °C for 24 h to obtain the white MOF-808 sample.

[0027] (2) Preparation of Ag-Ni photocatalyst

[0028] First, 0.145 g of Ni(NO3)2 and 0.085 g of AgNO3 were weighed out and added to 25 mL of deionized water, and stirred thoroughly to achieve complete dissolution. Then, 5 mL of a 1 M NaOH aqueous solution was prepared and added to the aforementioned solution, with stirring continued for 5 min. Next, 1 mL of a 0.01 M sodium dodecyl sulfate solution was prepared and added to the mixed solution, with stirring again for 5 min. Then, 4 mL of hydrazine hydrate solution was added, and stirring was maintained for 1 hour. Subsequently, the precursor solution was transferred to a 100 mL polytetrafluoroethylene autoclave and placed in an oven at 160 °C for 6 h. After the reaction was complete, the temperature was lowered to room temperature, and the mixture was repeatedly washed with deionized water and ethanol to remove impurities. Finally, the resulting grayish-black solid was placed in a vacuum drying oven at 60 °C and dried for 24 h to obtain the Ag-Ni alloy photocatalyst.

[0029] (3) Preparation of MOF-808 / Ag-Ni composite photocatalyst

[0030] First, 100 mg and 25 mg of the prepared MOF-808 and Ag-Ni photocatalysts, respectively, were placed in beakers. Then, 10 mg of PVP and 30 mL of ethanol were weighed and added to the beakers. The mixture was stirred for 30 min using a high-speed stirrer, and then transferred to a 100 mL polytetrafluoroethylene autoclave. The autoclave was set at 100 °C and maintained for 8 h. After cooling to room temperature, the bottom solid was washed several times with deionized water and ethanol. After washing, the sample was dried in a vacuum drying oven to obtain the MOF-808 / Ag-Ni composite photocatalyst. Furthermore, following the above steps, the amount of Ag-Ni added was adjusted to prepare MOF-808 / Ag-Ni composite photocatalysts with different proportions.

[0031] (4) Preparation of macroscopic aerogel composite photocatalysts of MOF-808 / RGO / Ag-Ni

[0032] First, a 5 mg / mL GO solution was sonicated for 6 h. Next, 5 mL of the GO solution was taken, and 50 mg of the MOF-808 / Ag-Ni composite photocatalyst was added, followed by sonication and stirring for 1 h. Then, 30 mg of ascorbic acid was weighed, added to the solution, and stirred for 30 min. Subsequently, the precursor solution was transferred to a quartz bottle and placed in an oven at 95°C for 3 h. This yielded the MOF-808 / RGO / Ag-Ni hydrogel material. Finally, the MOF-808 / RGO / Ag-Ni aerogel material was obtained using freeze-drying. Depending on the amount of Ag-Ni added, the composite photocatalysts were named M / R / AN, respectively. 15 M / R / AN 20M / R / AN 25 and M / R / AN 30 .

[0033] The prepared MOF-808 / RGO / Ag-Ni macroscopic aerogel composite photocatalyst is used as a catalyst for photocatalytic CO2 production.

[0034] In the technical solution described in this invention, the amount of deionized water used is sufficient to completely dissolve the solute.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] In recent years, alloy materials have received increasing attention because they can maintain the properties of their components and generate synergistic effects through cooperation. Silver can serve as the active center in photocatalytic reactions, participating in the process. Nickel has high reactivity and can lower the activation energy of photocatalytic reactions, thereby increasing the reaction rate. Nickel can be combined with other photocatalytic materials to form composite photocatalysts. Ag-Ni alloys exhibit synergistic effects, simultaneously overcoming key challenges in the photocatalytic process. For example, silver has excellent carbon-carbon coupling ability, while nickel can promote the dissociation of hydrocarbon intermediates. This synergistic effect helps improve the selectivity and efficiency of photocatalytic reactions. Ag-Ni alloys possess advantages in photocatalysis, including excellent photocatalytic activity, synergistic effects, broadened photoresponse range, improved photostability, resistance to photocorrosion, and simple preparation methods, offering potential for achieving efficient and environmentally friendly photocatalytic reactions.

[0037] This invention prepares a flattened, macroscopic aerogel composite photocatalyst MOF-808 / RGO / Ag-Ni. The flattened, macroscopic shape increases the contact area between the catalyst and light, which is more conducive to subsequent catalytic reactions. The introduction of RGO and Ag-Ni successfully broadens the visible light absorption range of the composite photocatalyst. Furthermore, the Z-shaped heterojunction formed between MOF-808 and Ag-Ni also improves the electron transport rate compared to the MOF-808 / RGO composite photocatalyst, further enhancing the photocatalytic CO2 reduction activity.

[0038] Specifically, MOF-808 exhibits a wider band gap of 3.95 eV, while Ag-Ni has a band gap of 2.07 eV. However, when MOF-808 and Ag-Ni are in contact to form an aerogel structure, the band gap of M / R / AN25 shrinks to 2.34 eV. This result indicates that the composite photocatalyst can absorb higher-energy photons, thereby improving light absorption efficiency and photothermal conversion efficiency, and further enhancing the photocatalytic CO2 reduction performance. Under full-spectrum irradiation conditions, the CO yield of the aerogel reaches its maximum value of 21.56 μmol g when the Ag-Ni addition amount is 25 mg.-1 It is approximately MOF-808 (1.37 μmol g). -1 16 times that of Ag-Ni (2.88 μmol g) -1 The CH4 yield of the aerogel reached a maximum of 1.34 μmol g when the Ag-Ni addition was 30 mg. -1 They are MOF-808 (0.08 μmol g) -1 16 times that of Ag-Ni (0.65 μmol g) -1 It is about twice that of ). Attached Figure Description

[0039] Figure 1 (a) XRD spectra of different composite samples and MOF-808, RGO, and Ag-Ni; (b) XRD spectra of RGO and GO compared.

[0040] Figure 2 Fourier transform infrared (FTIR) spectra of (a) MOF-808, RGO, Ag-Ni and M / R / AN25, (b) FTIR spectra of RGO and GO, (c) FTIR spectra of different composite materials, and (d) Raman curves of GO, RGO and M / R / AN25.

[0041] Figure 3 TEM images of (a) MOF-808, (b) RGO, (c) Ag-Ni, (d) M / AN and (e) M / R / AN25, SEM images of (f) MOF-808, (g) RGO, (h) Ag-Ni, (i) M / AN and (j) M / R / AN25, and elemental scan image of (ko) M / R / AN25;

[0042] Figure 4 For M / R / AN 25 Hydrogel image (a); M / R / AN 25 aerogel image (b);

[0043] Figure 5 (a) UV-vis DRS of different samples, (b) MOF-808, Ag-Ni and M / R / AN 25 The bandgap width curve;

[0044] Figure 6 (a) Kinetic curves of photocatalytic CO2 reduction to CO from different samples, (b) kinetic curves of photocatalytic CO2 reduction to CH4 from different samples, (c) cyclic kinetic curves of photocatalytic CO2 reduction to CO and CH4 from M / R / AN25, and (d) blank control experiment.

[0045] Figure 7Kinetic curves for photocatalytic reduction of CO2 to CO for different samples (a); kinetic curves for photocatalytic reduction of CO2 to CH4 (b). Detailed Implementation

[0046] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of the invention and should not be considered as specific limitations thereof. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods.

[0047] The following ingredients are used in this invention: zirconium oxychloride octahydrate (ZrOCl2·8H2O), trimesic acid (C9H6O6), N,N-dimethylformamide (DMF, C3H7NO), ascorbic acid (C6H8O6), nickel nitrate hexahydrate (Ni(NO3)2), silver nitrate (AgNO3), hydrazine hydrate (N2H4·H2O), sodium hydroxide (NaOH), and sodium dodecyl sulfate (C 12 H 25 NaO4S was purchased from Sinopharm Chemical Reagent Co., Ltd. Formic acid (CH2O2) and polyvinylpyrrolidone (PVP, (C6H9NO)) were also purchased. n The graphene oxide (GO) was purchased from Shanghai Aladdin Industrial Co., Ltd., and from Hunan Fenghua Materials Development Co., Ltd. All materials were of analytical grade and used directly.

[0048] Example 1: Flattened spherical macroscopic aerogel composite photocatalyst MOF-808 / RGO / Ag-Ni

[0049] (1) Preparation of MOF-808 photocatalyst:

[0050] First, 0.258 g ZrOCl2·8H2O, 0.056 g C9H6O6, and 12 mL DMF were added to a beaker and stirred for 10 min. After observing that the white solid in the beaker had completely dissolved, 12 mL formic acid was added to the precursor solution and stirring was continued for 30 min. Then, the well-mixed solution was completely transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and heated at 120 °C for 48 h. After the reaction was completed, the resulting white solution was cooled to room temperature and repeatedly washed and centrifuged with deionized water, DMF, and ethanol. Finally, the sample was dried in a vacuum drying oven at 60 °C for 24 h to obtain the white MOF-808 sample.

[0051] (2) Preparation of Ag-Ni photocatalyst:

[0052] First, 0.145 g of Ni(NO3)2 and 0.085 g of AgNO3 were weighed out and added to 25 mL of deionized water, and stirred thoroughly to achieve complete dissolution. Then, 5 mL of a 1 M NaOH aqueous solution was prepared and added to the aforementioned solution, with stirring continued for 5 min. Next, 1 mL of a 0.01 M sodium dodecyl sulfate solution was prepared and added to the mixed solution, with stirring again for 5 min. Then, 4 mL of hydrazine hydrate solution was added, and stirring was maintained for 1 hour. Subsequently, the precursor solution was transferred to a 100 mL polytetrafluoroethylene autoclave and placed in an oven at 160 °C for 6 h. After the reaction was complete, the temperature was lowered to room temperature, and the mixture was repeatedly washed with deionized water and ethanol to remove impurities. Finally, the resulting grayish-black solid was placed in a vacuum drying oven at 60 °C and dried for 24 h to obtain the Ag-Ni alloy photocatalyst.

[0053] (3) Preparation of MOF-808 / Ag-Ni composite photocatalyst

[0054] First, 100 mg and 25 mg of the prepared MOF-808 and Ag-Ni photocatalysts, respectively, were placed in beakers. Then, 10 mg of PVP and 30 mL of ethanol were weighed and added to the beakers. The mixture was stirred for 30 min using a high-speed stirrer, and then transferred to a 100 mL polytetrafluoroethylene autoclave. The autoclave was set at 100 °C and maintained for 8 h. After cooling to room temperature, the bottom solid was washed several times with deionized water and ethanol. After washing, the sample was dried in a vacuum drying oven to obtain MOF-808 / Ag-Ni (M / AN) 25 (M / AN, the attached figure uses M / AN for comparison) composite photocatalyst. In addition, following the above steps, the amount of Ag-Ni added was adjusted to prepare MOF-808 / Ag-Ni composite photocatalysts with different ratios. (4) Preparation of MOF-808 / RGO / Ag-Ni macroscopic aerogel composite photocatalyst

[0055] First, a 5 mg / mL GO solution was sonicated for 6 h. Next, 5 mL of the GO solution was taken, and 50 mg of the MOF-808 / Ag-Ni composite photocatalyst was added, followed by sonication and stirring for 1 h. Then, 30 mg of ascorbic acid was weighed, added to the solution, and stirred for 30 min. Subsequently, the precursor solution was transferred to a quartz bottle and placed in an oven at 95°C for 3 h. This yielded the MOF-808 / RGO / Ag-Ni hydrogel material. Finally, the MOF-808 / RGO / Ag-Ni aerogel material was obtained using freeze-drying. Based on the different Ag-Ni addition amounts (15 mg, 20 mg, 25 mg, 30 mg), the composite photocatalysts were named M / R / AN, respectively.15 M / R / AN 20 M / R / AN 25 and M / R / AN 30 .

[0056] (5) Detection of CO2 reduction products and cyclic experiment of photocatalytic CO2 reduction using gas chromatography.

[0057] Before conducting the experiment, the mass of the prepared macroscopic aerogel material was accurately measured and recorded. Then, an appropriate amount of the material was placed in a specially designed small square quartz glass slide groove. Next, the sample-loaded slide was placed into a 250 mL quartz glass reactor. The experiment continued by purging the reactor with 99.99% pure CO2 gas through a water stream for 30 minutes to completely remove internal air. After this step, only CO2 gas remained in the reactor, which was then sealed to prevent gas leakage. Subsequently, the sealed reactor was placed under a 300W xenon lamp to simulate sunlight. During the illumination process, 5 mL gas samples were extracted every hour, and gas chromatography was used for quantitative and qualitative analysis. For the CO2 reduction stability cycling test, the detection time of the above steps was extended to 16 hours, with each cycle lasting 4 hours. After completing the stability cycling test, the samples underwent further characterization analysis. To ensure the reliability and accuracy of the experimental results, three blank control experimental groups were set up: (1) CO2 gas was replaced with pure Ar gas, while keeping other experimental conditions consistent; (2) without adding photocatalyst to the reactor, while keeping the light source and CO2 gas conditions unchanged; (3) without light treatment while keeping the CO2 gas and photocatalyst unchanged.

[0058] result:

[0059] Figure 1 a is MOF-808, RGO, Ag-Ni, M / AN (i.e. M / AN 25 ) and different composite photocatalysts (M / R / AN) 15 M / R / AN 20 M / R / AN 25 and M / R / AN 30The XRD pattern of the MOF-808 sample shows three distinct characteristic peaks at 4.36°, 8.31°, and 8.69°, corresponding to the (111), (311), and (222) crystal planes, respectively. The XRD pattern of the Ag-Ni alloy shows the coexistence of characteristic peaks of Ag and Ni elements. At 38.23°, 44.45°, 64.51°, and 77.57°, they correspond to the (111), (200), (220), and (311) crystal planes of Ag, respectively. This is consistent with the standard value given by the Joint Committee on Powder Diffraction Standards (JCPDS card No. 04-0783). For Ni, its characteristic peaks are located at 44.45°, 52.33°, and 77.23°, corresponding to the (111), (200), and (220) crystal planes, respectively. The presence of Ni and Ag atoms does not lead to a change in the crystal lattice structure. Characteristic peaks of MOF-808 and Ag-Ni were clearly observed in both the M / AN powder sample and the macroscopic aerogel composite photocatalyst. The peak intensity in the XRD pattern of the aerogel composite gradually increased with increasing Ag-Ni alloy ratio. However, the broad peak of RGO at 25.39° was not prominent in the composite sample, possibly due to the relatively low RGO content. Figure 1 As shown in b, GO was successfully reduced to RGO under the action of ascorbic acid. XRD patterns confirmed the successful preparation of the composite sample.

[0060] Figure 2 ac is the FT-IR spectrum of the material, M / R / AN 25 The characteristic peaks are highly similar to those of MOF-808, and some peaks of Ag-Ni are also found in M / R / AN. 25 This is reflected in the 3377cm. -1 At this location, the infrared spectrum shows OH stretching vibration peaks; 1389, 1576, and 1619 cm⁻¹. -1 The vibrational peak appearing at 1439 cm⁻¹ originates from the asymmetric stretching vibration of the carboxyl group in the organic ligand H₃BTC; -1 The vibration is C=C stretching vibration; 1398cm -1 At this point, the C-OH group of alcohols undergoes bending vibration. (655-755 cm⁻¹) -1 The peaks between them are caused by the asymmetric vibrations of Zr-O, indicating that BTC 3- The -COOH group in the solution coordinates with Zr ions, rather than simply mixing. (565cm) -1 The peak at that point is considered to be an asymmetric Zr-(OC) bond stretching vibration. For example... Figure 2 As shown in b, GO contains a large number of functional groups. However, after hydrothermal treatment, GO is reduced to RGO, and some functional groups in RGO are removed or reduced to varying degrees. Figure 2The Fourier transform infrared spectrum of c confirmed the successful preparation of composite photocatalysts with composite powder structure and macroscopic aerogel structure. Figure 2 d presents GO, RGO, and M / R / AN 25 The Raman spectra of the composite sample reveal two significant characteristic peaks, one at 1345 cm⁻¹. -1 The D-band and located at 1585cm -1 The G-band at that location. It is worth noting that the intensity ratio of the D-band to the G-band (I... D / I G The improvement in M / AN reveals, on the one hand, the uniform distribution of M / AN on RGO nanosheets, leading to the increase in sp in the graphene layer. 2 The disorder of hybrid carbon. On the other hand, this also suggests an increase in defects in RGO, which can provide active sites for photocatalytic reactions. This finding implies that M / R / AN 25 The sample has more active sites, thereby improving the photocatalytic CO2 reduction performance of the aerogel-structured composite photocatalyst.

[0061] Figure 3 As shown in a and f, MOF-808 exhibits a regular octahedral structure with a diameter of approximately 500 nm. Figure 3 b and g show the ultrathin sheet layer of RGO, with irregular holes and wrinkles on its surface. Figure 3 c and h show that the Ag-Ni alloy is spherical with a size of less than 100 nm. From Figure 3 In d and i, the bonding between Ag-Ni and MOF-808 octahedra can be observed, and this bonding mode is conducive to electron transport. Figure 3 e and j indicate a close contact between Ag-Ni and MOF-808, and uniform dispersion within the RGO sheets. This uniform dispersion helps prevent the stacking of the RGO sheets and facilitates the formation of a macroscopic aerogel structure with a fluffy appearance. Figure 3 Elemental scans from KO confirm the successful preparation of the macroscopic aerogel material. From... Figure 3 The ko indicates a relatively low Ni content, likely because Ni atoms are encapsulated within the alloy during Ag-Ni alloy formation. Furthermore, we also observed M / R / AN... 25 The macroscopic appearance.

[0062] like Figure 4 As shown in a and b, where Figure 4 a is an M / R / AN25 hydrogel (containing water). Figure 4 b is M / R / AN25 hydrogel obtained by freeze-drying. 25 Aerogel; M / R / AN 25The aerogel exhibits a flattened, round shape, increasing the contact area between the material and light, thus enabling more efficient utilization of light energy. Numerous cracks were observed on the surface of the macrostructure, which facilitates light transmission within the macrostructure. Furthermore, the use of freeze-drying technology effectively prevented the collapse of internal pores, the presence of which promotes light scattering and refraction within the aerogel.

[0063] like Figure 5 As shown in Figure a, MOF-808 exhibits significant light absorption in the ultraviolet region, with its absorption band edge around 320 nm. However, RGO and Ag-Ni both show good light absorption performance in the 200-1000 nm range. Furthermore, Ag-Ni exhibits a sharp peak at 320 nm, which is the resonance peak of pure silver. Pure nickel, on the other hand, does not show a significant resonance peak, possibly due to its lower nickel content. The composite photocatalyst exhibits tailing absorption, covering the entire visible light region. This is mainly because the addition of RGO and Ag-Ni significantly improves the absorption rate of the composite material in the visible light region, thus utilizing solar energy more effectively. Additionally, the composite photocatalyst exhibits a slightly broad peak at 380 nm, which may be due to the introduction of Ag-Ni causing a shift in the Ag resonance peak. Because the amount of Ag-Ni added is relatively small, the peak is not significant. This can be determined by the (αhν) equation in the Tauc equation. 1 / 2 The band gap width is obtained by plotting the curve against the photon energy (hν). Figure 5 As shown in b, MOF-808 has a wider band gap of 3.95 eV, while Ag-Ni has a band gap of 2.07 eV. However, when MOF-808 and Ag-Ni are in contact to form an aerogel structure, M / R / AN 25 The band gap width was reduced to 2.34 eV. This result indicates that the composite photocatalyst can absorb higher-energy photons, thereby improving the light absorption efficiency and photothermal conversion efficiency, and further enhancing the photocatalytic CO2 reduction performance.

[0064] like Figure 6 As shown in Figures a and b, the detection results of CO2 reduction products using gas chromatography indicate that the experimental products mainly consist of a large amount of CO and a small amount of CH4. Analysis revealed that the CO and CH4 yields of the aerogel material were not only higher than those of the monomer but also exceeded those of the powder material M / AN. This result suggests that the presence of RGO and the aerogel structure is beneficial to the photocatalytic reaction. Under full-spectrum irradiation conditions, the CO yield of the aerogel reached its maximum value of 21.56 μmolg when the Ag-Ni addition amount was 25 mg. -1 It is approximately MOF-808 (1.37 μmol g). -1 16 times that of Ag-Ni (2.88 μmol g) -1The CH4 yield of the aerogel reached a maximum of 1.34 μmol g when the Ag-Ni addition was 30 mg. -1 They are MOF-808 (0.08 μmol g) -1 16 times that of Ag-Ni (0.65 μmol g) -1 Approximately twice that of M / R / AN. Furthermore, regarding M / R / AN... 25 A cyclic experiment of photocatalytic CO2 reduction was conducted. For example... Figure 6 As shown in Figure c, after 16 hours of continuous irradiation, the yields of CO and CH4 decreased slightly, which may be related to the loss of active sites in the sample. However, the overall cycling performance remained stable, indicating that the prepared composite photocatalyst has good stability. Figure 6 As shown in Figure d, no product was detected under conditions without a light source or photocatalyst. Similarly, no product was detected under an Ar atmosphere, indicating that the catalyst, light source, and CO2 are indispensable factors for photocatalytic CO2 reduction.

[0065] like Figure 7 As shown in a and b, M / R / AN 25 The catalytic performance is superior to M / AN, MR-5 (powder), or M / R-5 (aerogel), proving that M / R / AN... 25 As a composite material, its catalytic efficiency has been greatly improved.

[0066] Note: The above comparative examples are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above comparative examples, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for a three-dimensional macroscopic MOF-808 / RGO / Ag-Ni composite photocatalyst, comprising the following steps: (1) Preparation of MOF-808 photocatalyst: First, ZrOCl2·8H2O, C9H6O6 and DMF were stirred; formic acid was added and stirred continuously until well mixed, and the mixture was heated at 120℃; after the reaction was completed, the mixture was cooled to room temperature to obtain a white MOF-808 sample. (2) Preparation of Ag-Ni photocatalyst First, Ni(NO3)2 and AgNO3 were added to water and stirred until dissolved; then, NaOH aqueous solution was added and stirred continuously; next, sodium dodecyl sulfate solution was added and stirred again; hydrazine hydrate solution was added and stirred for 1 hour; the solution was heated to 160°C; after the reaction was completed, the temperature was lowered to room temperature to obtain the Ag-Ni alloy photocatalyst. (3) Preparation of MOF-808 / Ag-Ni composite photocatalyst First, the prepared MOF-808, Ag-Ni photocatalyst, PVP and ethanol were mixed and stirred. Then the mixture was heated to 100℃. After the reaction was completed, it was cooled to room temperature to obtain the MOF-808 / Ag-Ni composite photocatalyst. (4) Preparation of macroscopic aerogel composite photocatalyst of MOF-808 / RGO / Ag-Ni The GO solution was ultrasonically treated, and the MOF-808 / Ag-Ni composite photocatalyst was added. The mixture was then ultrasonicated and stirred. Ascorbic acid was added and stirred for 30 min. The solution was then heated at 95 °C to obtain the MOF-808 / RGO / Ag-Ni hydrogel material. Finally, the MOF-808 / RGO / Ag-Ni aerogel material was obtained by freeze-drying.

2. The method according to claim 1, comprising the following steps: (1) Preparation of MOF-808 photocatalyst: First, 0.258 g ZrOCl2·8H2O, 0.056 g C9H6O6, and 12 mL DMF were added and stirred for 10 min to dissolve completely. Then, 12 mL formic acid was added and stirring continued for 30 min. The mixture was then heated at 120 °C for 48 h. After the reaction was completed, the resulting white solution was cooled to room temperature and repeatedly washed and centrifuged with deionized water, DMF, and ethanol. Finally, the sample was dried in a vacuum drying oven at 60 °C for 24 h to obtain a white MOF-808 sample. (2) Preparation of Ag-Ni photocatalyst First, 0.145 g of Ni(NO3)2 and 0.085 g of AgNO3 were weighed and added to 25 mL of deionized water, and stirred thoroughly to achieve complete dissolution. Then, 1 M NaOH aqueous solution was added and stirred continuously for 5 min. Next, 0.01 M sodium dodecyl sulfate solution was added and stirred again for 5 min. 4 mL of hydrazine hydrate solution was added and stirred for 1 hour. Then, the mixture was heated at 160°C for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the mixture was repeatedly washed with deionized water and ethanol to remove impurities. Finally, the resulting gray-black solid was placed in a vacuum drying oven at 60°C to obtain the Ag-Ni alloy photocatalyst. (3) Preparation of MOF-808 / Ag-Ni composite photocatalyst First, 100 mg of the prepared MOF-808 and 25 mg of Ag-Ni photocatalyst were added to 10 mg of PVP and 30 mL of ethanol, stirred for 30 min, heated at 100 °C for 8 h, and then cooled to room temperature. The bottom solid was washed several times with deionized water and ethanol. After washing, the sample was placed in a vacuum drying oven for drying to obtain the MOF-808 / Ag-Ni composite photocatalyst. In addition, following the above steps, the amount of Ag-Ni added was adjusted to prepare MOF-808 / Ag-Ni composite photocatalysts with different ratios. (4) Preparation of macroscopic aerogel composite photocatalyst of MOF-808 / RGO / Ag-Ni First, a 5 mg / mL GO solution was sonicated for 6 h. Next, 5 mL of the GO solution was taken, and 50 mg of MOF-808 / Ag-Ni composite photocatalyst was added to it, followed by sonication and stirring for 1 h. Then, 30 mg of ascorbic acid was weighed, added to the solution, and stirred for 30 min. Subsequently, the precursor solution was transferred to a quartz bottle, placed in an oven, and kept at 95 °C for 3 h. This yielded the MOF-808 / RGO / Ag-Ni hydrogel material. Finally, the MOF-808 / RGO / Ag-Ni aerogel material was obtained by freeze-drying.

3. The application of a MOF-808 / RGO / Ag-Ni macroscopic aerogel composite photocatalyst prepared according to the method of claim 1 or 2 as a catalyst for photocatalytic CO2.

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