A doped iron porphyrin metal-organic framework photocatalyst dispersing gold nanoparticles, a preparation method and application thereof

Abstract

The application discloses a kind of dispersed gold nanoparticle doped iron porphyrin metal organic framework photocatalyst and preparation method and application, chloroauric acid tetrahydrate and L-glutathione are mixed uniformly, and 65~75 ℃ is kept, product is washed and dispersed in water;1-(3-(dimethylamino)propyl)-3-ethyl carbodiimide hydrochloride, hydroxysuccinimide and L-cysteine are added at 60~70 ℃, and then 60~80 ℃ is kept, product is washed and dispersed in water and NaOH solution;Iron chloride is added and stirred, product is washed and dried, and then dispersed in water to obtain dispersion liquid;4,4',4'-(porphyrin-5,10,15,20)-tetrabenzoic acid and aluminum chloride are mixed uniformly in water, and then 160~200 ℃ is kept, product is dispersed in water, and then mixed with dispersion liquid, 60~70 ℃ is kept, and product is washed to obtain dispersed gold nanoparticle doped iron porphyrin metal organic framework photocatalyst.

Description

Technical Field

[0001] This invention belongs to the fields of materials preparation and environmental energy technology, specifically relating to a doped iron porphyrin metal-organic framework photocatalyst with dispersed gold nanoparticles, its preparation method, and its application. Background Technology

[0002] Ammonia (NH3) is not only an important energy storage medium and carbon-free energy carrier, but also an indispensable industrial chemical raw material for the production of explosives and fertilizers, playing a vital role in the development of human society. Currently, the Haber-Bosch process is widely used for the large-scale synthesis of NH3; however, this process is carried out under high temperature (573–773 K) and high pressure (100–200 atm) conditions, consuming approximately 2% of global energy annually and releasing 400 million tons of carbon dioxide. Therefore, there is an urgent need to develop more sustainable catalytic processes to meet the growing demands for environmental protection and energy efficiency.

[0003] In nature, biological nitrogen fixation relies on nitrogenase to generate NH3 via a π-bond mechanism. First, adenosine 5′-triphosphate (ATP) hydrolysis provides energy to the dimerized ferritin, providing an electron source for activating the N-N triple bond (process 1). Subsequently, electrons are transferred to the FeMo cofactor via an electron relay (P-cluster). Then, the σ electrons of N2 are transferred to the unoccupied d orbitals of the Fe / Mo atoms in the FeMo cofactor. The 3d orbitals occupied by the Fe / Mo atoms donate electrons to the N-Nπ antibonding system, forming a chemical bond, adsorbing and activating N2. The activation of N2 to NH3 via the π-bond mechanism by nitrogenase is a crucial process. Therefore, it is necessary to find a photocatalyst with a well-defined structure-activity relationship to mimic the N2 fixation process of nitrogenase.

[0004] Metal-organic frameworks (MOFs) are considered ideal materials for constructing molecular photocatalysts with high-density and atomically dispersed active metal sites. These dispersed metal sites serve as active centers for N2 adsorption and activation, functioning similarly to FeMo cofactors. Compared to traditional photocatalysts, MOFs allow for the easy simultaneous assembly of photosensitizers and cocatalysts into a single system due to their pre-designability and integrity. Therefore, MOFs are considered potential catalysts for mimicking nitrogenase. Among the ligand selections for MOF construction, porphyrins have attracted significant attention due to their excellent photosensitivity. In 2021, Shang et al. discovered the assembly of photosensitive porphyrin structures with Fe catalytic centers into MOF molecular catalysts. However, the conduction band minimum (CBM) of porphyrins is lower than that of iron atoms, indicating that the transfer of free electrons from porphyrins to iron atoms is thermodynamically unfavorable. Therefore, regulating the electronic structure of iron atoms and establishing pathways for free electron transfer between the photosensitive unit (porphyrin) and the catalytic center (iron atom) is crucial for constructing highly efficient nitrogen fixation photocatalysts.

[0005] Gold nanoclusters (Au NCs) are considered promising photoelectron collecting units. The higher CBM of porphyrins compared to Au NCs indicates that the transfer of photoelectrons from porphyrins to Au NCs is thermodynamically favorable. Therefore, Au NCs act as electron relays, accepting photoexcited electrons from porphyrin MOFs (PMOFs) and effectively promoting the separation of photoexcited electron-hole pairs within the MOF, similar to the role of p-clusters in nitrogenases. Free electrons on Au NCs can also be directly transferred to N2 molecules adsorbed on the surface of Au atoms. Compared to photoexcited electrons generated in semiconductors, the charge carriers generated in Au NCs typically possess sufficient energy to activate chemical bonds.

[0006] However, Au atoms lack the electronic structure of a nitrogenase catalytic center, causing N2 to be adsorbed via physical adsorption. Therefore, a pathway for the transfer of free electrons from Au nanocarbon atoms to the catalytic center atoms has not yet been established, making it impossible to construct highly efficient N2-fixed photocatalysts. Summary of the Invention

[0007] To overcome the shortcomings of the existing technology, this invention discloses a doped iron porphyrin metal-organic framework photocatalyst with dispersed gold nanoparticles, its preparation method, and its application, which achieves efficient photocatalytic nitrogen fixation under mild conditions and increases the yield of ammonia synthesized by photocatalytic conversion of nitrogen.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing a doped iron porphyrin metal-organic framework photocatalyst with dispersed gold nanoparticles includes the following steps:

[0010] S1, chloroauric acid tetrahydrate and L-glutathione were mixed evenly in ultrapure water at a mass ratio of 9.7:10, and then kept at 65-75℃ to obtain reaction solution a. The product in reaction solution a was washed and then evenly dispersed in ultrapure water to obtain dispersion a.

[0011] S2, 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride, hydroxysuccinimide and L-cysteine ​​are added to dispersion a at 60-70℃ and mixed evenly. The mass ratio of L-cysteine ​​to chloroauric acid tetrahydrate in S1 is 15:9.7. Then the mixture is kept at 60-80℃ to obtain reaction solution b. The product in reaction solution b is washed and then evenly dispersed in ultrapure water and NaOH solution to obtain dispersion b.

[0012] S3, anhydrous ferrous chloride is added to dispersion b and stirred to obtain a mixture. The product in the mixture is washed, dried and then uniformly dispersed in ultrapure water to obtain dispersion c.

[0013] 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid and aluminum chloride hexahydrate were mixed evenly in ultrapure water at a mass ratio of 5:3. The mixture was then kept at 160–200 °C to obtain reaction solution c. The precipitate in reaction solution c was washed and dried to obtain the product. The product was evenly dispersed in ultrapure water to obtain dispersion d. Dispersion c and dispersion d were mixed evenly at a volume ratio of (3–10):20 and kept at 60–70 °C to obtain reaction solution d. The product in reaction solution d was washed to obtain a gold nanoparticle-doped iron porphyrin metal-organic framework photocatalyst.

[0014] Preferably, in S1, the ratio of chloroauric acid tetrahydrate to ultrapure water is 9.7 mg: 6 mL, and then the mixture is kept at 65–75 °C for 22–26 h to obtain reaction solution a.

[0015] Further, S1 adds acetonitrile to reaction solution a, with a volume ratio of acetonitrile to ultrapure water of 1:1. Then, it is washed by centrifugation with acetonitrile solution, with a volume ratio of ultrapure water to acetonitrile of 3:1. Finally, the obtained product is uniformly dispersed in ultrapure water, with a ratio of ultrapure water to chloroauric acid tetrahydrate of 2 mL: 9.7 mg.

[0016] Preferably, in S2, the mass ratio of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride, hydroxysuccinimide and L-cysteine ​​is 2:1:15, and the ratio of L-cysteine ​​to reaction solution a is 5mg:2mL. Then, the mixture is kept at 60-80℃ for 8-12h to obtain reaction solution b.

[0017] The NaOH solution has a mass percentage of 50%, and the ratio of NaOH solution, ultrapure water and L-cysteine ​​is 0.01 mL: 2 mL: 15 mg.

[0018] Further, the ratio of anhydrous ferrous chloride to dispersion b in S3 is 3 μmol: 2 mL. Anhydrous ferrous chloride is added to dispersion b and stirred for 2.5–3.5 min to obtain a mixture. The mixture is first washed 3–5 times with 30–50 mL of ultrapure water by centrifugation to obtain a preliminary washed product. The preliminary washed product is then soaked in 30–50 mL of ultrapure water for 22–26 h and then washed by centrifugation. The resulting product is then soaked in 30–50 mL of ultrapure water for 22–26 h and then washed by centrifugation. This process is repeated a total of 3–5 times to obtain a secondary washed product. The secondary washed product is then washed 3–5 times with 30–50 mL of ultrapure water by centrifugation. The resulting precipitate is dried at 55–65 °C for 10–14 h and then uniformly dispersed in ultrapure water of the same volume as dispersion b to obtain dispersion c.

[0019] Preferably, in S3, the ratio of aluminum chloride hexahydrate to ultrapure water is 6 mg: 1 mL, and then the mixture is kept at 160–200 °C for 20–26 h to obtain reaction solution c.

[0020] Further, in step S3, the precipitate in reaction solution c was centrifuged sequentially with ultrapure water, N,N-dimethylformamide and acetone, and then freeze-dried for 14-16 hours to obtain the product. Finally, the product was uniformly dispersed in ultrapure water at a ratio of 4 mg to 1 mL to obtain dispersion d.

[0021] Preferably, the heat preservation described in S3 is carried out in an oil bath at 60-70°C for 22-26 hours to obtain reaction solution d.

[0022] A doped iron porphyrin metal-organic framework photocatalyst of dispersed gold nanoparticles obtained by the preparation method of the doped iron porphyrin metal-organic framework photocatalyst of dispersed gold nanoparticles as described in any one of the above methods.

[0023] Application of a doped iron porphyrin metal-organic framework photocatalyst containing dispersed gold nanoparticles in the photocatalytic conversion of nitrogen to ammonia.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] This invention discloses a method for preparing a photocatalyst based on a doped iron porphyrin metal-organic framework (Al-PMOF) containing dispersed gold nanoparticles. A two-dimensional, highly photosensitive aluminum-based porphyrin metal-organic framework (Al-PMOF) prepared in ultrapure water using 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid and aluminum chloride hexahydrate is used as the support. This material exhibits excellent light absorption and photosensitivity, effectively absorbing solar energy and converting it into photogenerated carriers. Under the action of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride and hydroxysuccinimide, the Fe atoms on the Au nanoclusters (Au NCs) and the Al-PMOF ring are bridged by L-cysteine, regulating the electronic structure of the Fe atoms and increasing the N-Nπ antibonding orbitals. Free electrons can then transfer from Au nanoclusters to Fe atoms via the Au-C-Fe-N4 electron transfer pathway. NCs transfer to the Fe-N4 site, injecting electrons into the three-dimensional d orbitals of the Fe atom. This increases the occupancy of the N-Nπ antibonding orbitals in the d orbitals of the iron atom, promoting the cleavage of the N-Nπ bond and activating nitrogen. However, a low molar ratio of iron to aluminum prevents the complete insertion of Fe atoms into all porphyrin ligand rings, while a high ratio leads to interference from excess Au-C-Fe. Therefore, the synergistic effect of aluminum-based porphyrin metal-organic framework composite photocatalysts doped with Au nanoparticles is utilized to achieve efficient photocatalytic nitrogen fixation under mild conditions, thereby increasing the yield of ammonia synthesized from nitrogen gas. This significantly solves the high energy consumption and environmental pollution problems of the traditional industrial Haber-Bosch nitrogen fixation method. The preparation process is simple, low-cost, and uses readily available raw materials.

[0026] Furthermore, if the hydrothermal temperature is too high or the time is too long, the Al-PMOF sheets will be too thick; conversely, if the hydrothermal temperature is too low or the time is too short, pure-phase Al-PMOF cannot be formed.

[0027] Furthermore, excessively high oil bath temperatures accelerate the reaction rate, leading to incomplete or uneven insertion of Au-C-Fe porphyrin ligands into Al-PMOF, thereby reducing the catalytic activity and stability of the photocatalyst. Conversely, excessively low oil bath temperatures slow down the reaction rate, requiring a longer reaction time to achieve Fe atom insertion, thus increasing preparation time and energy consumption.

[0028] The present invention provides a dispersed gold nanoparticle-doped iron porphyrin metal-organic framework composite photocatalyst (Au-C-Fe / Al-PMOF). Al-PMOF is an aluminum-based porphyrin metal-organic framework material, and Au is an in-situ dispersed nanoparticle. Aluminum acts as a metal node, which has high stability. Au-C-Fe is bound and atomically dispersed by residing on each porphyrin ring, promoting the adsorption and activation of N2. It has the characteristics of high temperature resistance and acid and alkali corrosion resistance, and is a photocatalytic material with good stability.

[0029] When the composite photocatalyst of this invention is used in the photocatalytic conversion of nitrogen to ammonia, compared with the unmodified Al-PMOF material, the nitrogen fixation activity of the Au-C-Fe / Al-PMOF composite photocatalyst of this invention is significantly improved (the photocatalytic NH3 yield is 324.1 μmol g). -1 h -1 Its ammonia production is 19.1 times that of Al-PMOF. Attached Figure Description

[0030] Figure 1 The images show the XRD patterns of the Au-C-Fe / Al-PMOF composite photocatalyst prepared in this invention, as well as Al-PMOF and Au / Al-PMOF.

[0031] Figure 2 The UV-Vis absorption spectra of the Au-C-Fe / Al-PMOF composite photocatalysts prepared in Examples 1-4 of this invention are shown.

[0032] Figure 3 The images show the photocatalytic conversion of nitrogen into ammonia by the Au-C-Fe / Al-PMOF composite photocatalysts prepared in Examples 1-4 of this invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These descriptions are intended to explain the invention and not to limit it.

[0034] Au NCs can be used as fluorescent probes for detecting metal ions, where the fluorescence intensity of Au NCs is significantly quenched by the effective electron transfer from Au NCs to metal cations. Therefore, by using metal cations with the ability to accept free electrons as sites for N2 chemisorption, it is theoretically possible to establish a pathway for electrons to transfer from the photosensitive unit to the catalytic center and then to the N-Nπ antibonding orbital.

[0035] L-cysteine ​​(L-cys) can be used as a linker for Fe 2+ A bridging ligand for Au NCs (prepared via glutathione reduction) was then developed. These Fe ions were then integrated into Al-PMOF as a model to construct the Au-C-Fe-N4 free electron transfer pathway. This invention, by designing a free electron transfer strategy to control the filling of iron atom d orbitals, thereby regulating the electron occupancy of N-Nπ antibonding orbitals, makes a positive contribution to the effective electron transfer between the photosensitive unit, catalytic center, and N2 molecules in N2-fixed photocatalysts.

[0036] The present invention discloses a method for preparing a composite photocatalyst, comprising the following steps:

[0037] Step 1: Prepare 10 mL of 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid (100 mg) solution;

[0038] Step 2: Add 60 mg of aluminum chloride hexahydrate to the 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid solution obtained in Step 1, and stir evenly at room temperature to obtain a mixed solution;

[0039] Step 3: Place the mixed solution obtained in Step 2 into a 50 mL polytetrafluoroethylene liner and hydrothermally heat it at 160–200 °C for 20–26 h. After cooling to room temperature, centrifuge it sequentially with 40 mL ultrapure water, 40 mL N,N-dimethylformamide (DMF), and 40 mL acetone (washing 4 times with each reagent). Collect the dark purple product and freeze-dry it for 15 h to obtain pure Al-PMOF (aluminum-based porphyrin metal-organic framework).

[0040] The reaction is: AlCl3 + H4TCPP → Al(H2TCPP) + H + +Cl - Al(H2TCPP) is denoted as (Al-PMOF).

[0041] Take Al-PMOF (80 mg) and disperse it in 20 mL of ultrapure water using ultrasound for 3 hours to obtain a dispersion.

[0042] Step 4: Add 50.0 mg L-glutathione to 30 mL of chloroauric acid tetrahydrate (48.5 mg) solution, stir continuously for 1 hour, then heat in an oil bath at 65–75 °C for 22–26 hours. This allows L-glutathione (GSH-SCH2COOH) to reduce HAuCl4 (HAuCl4 + GSH-SCH2COOH → AuGSH-SCH2COOH + 4Cl). - +H + After cooling to room temperature, a reaction solution was obtained. Acetonitrile (30 mL) was added to the reaction solution. Au NCs were washed three times (8000 rpm, 5 min) by centrifugation with a mixture of ultrapure water and acetonitrile (volume ratio 3:1), 40 mL each time. The gold nanoclusters (Au NCs, i.e., AuGSH-SCH2COOH) were then further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0043] Step 5: Heat the Au NCs dispersion obtained in Step 4 to 60–70°C, add 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (10.0 mg) and hydroxysuccinimide (5.0 mg) as catalysts, stir for 30 minutes, then add 75 mg of L-cysteine, continue stirring for 1 hour, and then heat in an oil bath at 60–80°C for 8–12 hours (AuGSH-SCH2COOH+HSCH2CH(NH2)COOH→AuGSH-SCH2CO(NH)COOHCHCH2SH+H2O). Au-C (L-cysteine-functionalized surface-modified gold nanoclusters, namely AuGSH-SCH2CO(NH)COOHCHCH2SH) was prepared by grafting L-cysteine ​​(HSCH2CH(NH2)COOH) onto the surface of NCs. The nanoclusters were then centrifuged four times with 40 mL of ultrapure water (at a speed of 8000–12000 r / min). The supernatant was removed on the last centrifugation. Then, 10 mL of ultrapure water and 50 μL of 50% NaOH solution were added to obtain the Au-C dispersion.

[0044] Step 6: Add 15 μmol of anhydrous ferrous chloride to 10 mL of the Au-C dispersion prepared in Step 5 and stir continuously for 3 minutes. Utilize the thiol anchoring of iron ions on the Au-C surface (2AuGSH-SCH2CO(NH)COOHCHCH2SH+FeCl2→AuGSH-2SCH2CO(NH)COOHCHCH2SFeCl+Cl). - +H + The reaction proceeds to form Au-C-Fe (i.e., AuGSH-2SCH2CO(NH)COOHCHCH2SFeCl), followed by centrifugation (8500 rpm, 10 min) to collect the yellow precipitate. The precipitate is then washed five times with 40 mL of ultrapure water to remove unreacted Au-C precursors. Residual chloride and ferrous ions are washed away by centrifugation with 40 mL of ultrapure water every 24 h for a total of three times. Finally, the precipitate is centrifuged three times with 40 mL of ultrapure water (8000 rpm, 5 min each time), and dried at 60 °C for 12 h. The purified Au-C-Fe is then further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0045] Step 7: Add 3-10 mL of the Au-C-Fe dispersion prepared in Step 6 to the Al-PMOF dispersion prepared in Step 3, stir for 5 hours, and then heat in an oil bath at 60-70℃ for 22-26 hours (AuGSH-2SCH2CO(NH)COOHCHCH2SFeCl+Al(H2TCPP)→AuGSH-2SCH2CO(NH)COOHCHCH2S-Al(FeTCPP)+H + +Cl- The product was collected by centrifugation (8000-12000 r / min) and then washed three times with 40 mL of ultrapure water to obtain the Au-C-Fe / Al-PMOF composite photocatalyst, namely AuGSH-SCH2CO(NH)COOHCHCH2S-Al(FeTCPP). In the composite photocatalyst, Au is in situ dispersed nanoparticles, which can be used in the photocatalytic conversion of nitrogen to ammonia.

[0046] Example 1

[0047] HAuCl4·4H2O (48.5 mg) was dissolved in ultrapure water (30 mL) at room temperature. Then, L-glutathione (GSH, 50.0 mg) was added, and the mixture was stirred for 1 hour. The mixture was then heated in an oil bath at 70°C for 24 hours. After cooling to room temperature, acetonitrile (30 mL) was added. Finally, Au NCs were washed three times (8000 rpm, 5 min) with a mixture of ultrapure water and acetonitrile (3:1 v / v), 40 mL each time. The purified Au NCs were further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0048] Au NCs dispersion (1.0 mg / mL) -1 10 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (10.0 mg) and hydroxysuccinimide (5.0 mg) were added to a 50 mL round-bottom flask and heated to 65 °C. Then, 10.0 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride and 5.0 mg of hydroxysuccinimide were added as catalysts. After stirring for 30 minutes, 75 mg of L-cysteine ​​(L-cys) was added and stirring continued for 1 hour. The final mixture was stirred in a 65 °C oil bath for 10 hours to obtain Au-C. The Au-C was centrifuged four times with 40 mL of ultrapure water at 10000 rpm. The supernatant was removed on the last centrifugation. 10 mL of ultrapure water and 50 μL of NaOH solution (50% wt%) were added to the purified Au-C to promote its dispersion in the aqueous solution.

[0049] Add FeCl₂ 4H₂O (15 μmol) to 10 mL of Au-C dispersion (1.0 mg / mL). -1 After stirring continuously for 3 minutes, the mixture was centrifuged (8500 rpm, 10 minutes) to collect the yellow precipitate. The precipitate was then washed five times with 40 mL of ultrapure water to remove unreacted precursors. Residual chloride and ferrous ions were washed away by centrifugation with ultrapure water once daily for three days. Finally, the precipitate was centrifuged three times with 40 mL of ultrapure water (8000 rpm, 5 minutes each time), and dried at 60 °C for 12 hours. The purified Au-C-Fe was further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0050] 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid (H2TCPP, 100 mg) and AlCl3·6H2O (60 mg) were added to ultrapure water (10 mL) respectively. After stirring at room temperature for 3 hours, a mixed solution was obtained. This process is equivalent to the previous steps 1 and 2.

[0051] The mixed solution was transferred to a 50 mL reaction vessel and heated at 180 °C for 24 hours. It was then washed and centrifuged (40 mL each, 4 washes per reagent) with ultrapure water, N,N-dimethylformamide (DMF), and acetone to effectively remove unreacted precursors. The dark purple solid was freeze-dried for 15 hours for later use.

[0052] Al-PMOF (80 mg) was dispersed in 20 mL of water using ultrasound for 3 hours to obtain a dispersion. Then, 3 mL of Au-C-Fe (1.0 mg / mL) was added to the dispersion. -1 The dispersion was stirred for 5 hours and then heated in an oil bath at 65°C for 24 hours. The product was collected by centrifugation (at 10,000 r / min) and then washed three times with 40 mL of ultrapure water to obtain the Au-C-Fe / Al-PMOF composite photocatalyst.

[0053] Example 2

[0054] HAuCl4·4H2O (48.5 mg) was dissolved in ultrapure water (30 mL) at room temperature. Then, L-glutathione (GSH, 50.0 mg) was added, and the mixture was stirred continuously. After 1 hour, the mixture was heated in an oil bath at 70°C for 24 hours. After cooling to room temperature, acetonitrile (30 mL) was added. Finally, Au NCs were washed three times (8000 rpm, 5 min) with a mixture of ultrapure water and acetonitrile (3:1 v / v), 40 mL each time. The purified Au NCs were further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0055] Au NCs dispersion (1.0 mg / mL) -1 10 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (10.0 mg) and hydroxysuccinimide (5.0 mg) were added to a 50 mL round-bottom flask and heated to 65 °C. Then, 10.0 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride and 5.0 mg of hydroxysuccinimide were added as catalysts. After stirring for 30 minutes, 75 mg of L-cysteine ​​(L-cys) was added and stirring continued for 1 hour. The final mixture was stirred in a 65 °C oil bath for 10 hours to obtain Au-C. The Au-C was centrifuged four times with 40 mL of ultrapure water at 10000 rpm. The supernatant was removed on the last centrifugation. 10 mL of ultrapure water and 50 μL of NaOH solution (50% wt%) were added to the purified Au-C to promote its dispersion in the aqueous solution.

[0056] 15 μmol of FeCl₂·4H₂O was added to 10 mL of Au-C dispersion (1.0 mg mL⁻¹), and the mixture was stirred continuously for 3 minutes. The mixture was then centrifuged (8500 rpm, 10 minutes) to collect the yellow precipitate, which was then washed five times with 40 mL of ultrapure water to remove unreacted precursors. Residual chloride and ferrous ions were washed away by centrifugation with ultrapure water once daily for three days. Finally, the precipitate was centrifuged three times with 40 mL of ultrapure water (8000 rpm, 5 minutes each time), and dried at 60 °C for 12 hours. The purified Au-C-Fe was further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0057] 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid (H2TCPP, 100 mg) and AlCl3·6H2O (60 mg) were added separately to ultrapure water (10 mL) and stirred at room temperature. After 3 hours, the mixture was transferred to a 50 mL reactor and heated at 180 °C for 24 hours. The mixture was then washed and centrifuged (40 mL each, 4 washes per reagent) with ultrapure water, N,N-dimethylformamide (DMF), and acetone to effectively remove unreacted precursors. The dark purple solid was freeze-dried for 15 hours for later use.

[0058] Al-PMOF (80 mg) was dispersed in 20 mL of water using ultrasound for 3 hours to obtain a dispersion. Then, 5 mL of Au-C-Fe (1.0 mg / mL) was added to the dispersion. -1 The dispersion was stirred for 5 hours and then heated in an oil bath at 65°C for 24 hours. The product was collected by centrifugation (at 10,000 r / min) and then washed three times with 40 mL of ultrapure water to obtain the Au-C-Fe / Al-PMOF composite photocatalyst.

[0059] Example 3

[0060] HAuCl4·4H2O (48.5 mg) was dissolved in ultrapure water (30 mL) at room temperature. Then, L-glutathione (GSH, 50.0 mg) was added, and the mixture was stirred continuously. After 1 hour, the mixture was heated in an oil bath at 70°C for 24 hours. After cooling to room temperature, acetonitrile (30 mL) was added. Finally, Au NCs were washed three times (8000 rpm, 5 min) with a mixture of ultrapure water and acetonitrile (3:1 v / v), 40 mL each time. The purified Au NCs were further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0061] Au NCs dispersion (1.0 mg / mL) -110 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (10.0 mg) and hydroxysuccinimide (5.0 mg) were added to a 50 mL round-bottom flask and heated to 65 °C. Then, 10.0 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride and 5.0 mg of hydroxysuccinimide were added as catalysts. After stirring for 30 minutes, 75 mg of L-cysteine ​​(L-cys) was added and stirring continued for 1 hour. The final mixture was stirred in a 65 °C oil bath for 10 hours to obtain Au-C. The Au-C was centrifuged four times with 40 mL of ultrapure water at 10000 rpm. The supernatant was removed on the last centrifugation. 10 mL of ultrapure water and 50 μL of NaOH solution (50% wt%) were added to the purified Au-C to promote its dispersion in the aqueous solution.

[0062] 15 μmol of FeCl₂·4H₂O was added to 10 mL of Au-C dispersion (1.0 mg mL⁻¹), and the mixture was stirred continuously for 3 minutes. The mixture was then centrifuged (8500 rpm, 10 minutes) to collect the yellow precipitate, which was then washed five times with 40 mL of ultrapure water to remove unreacted precursors. Residual chloride and ferrous ions were washed away by centrifugation with ultrapure water once daily for three days. Finally, the precipitate was centrifuged three times with 40 mL of ultrapure water (8000 rpm, 5 minutes each time), and dried at 60 °C for 12 hours. The purified Au-C-Fe was further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0063] 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid (H2TCPP, 100 mg) and AlCl3·6H2O (60 mg) were added separately to ultrapure water (10 mL) and stirred at room temperature. After 3 hours, the mixture was transferred to a 50 mL reactor and heated at 180 °C for 24 hours. The mixture was then washed and centrifuged (40 mL each, 4 washes per reagent) with ultrapure water, N,N-dimethylformamide (DMF), and acetone to effectively remove unreacted precursors. The dark purple solid was freeze-dried for 15 hours for later use.

[0064] Al-PMOF (80 mg) was dispersed in 20 mL of water using ultrasound for 3 hours to obtain a dispersion. Subsequently, 8 mL of Au-C-Fe (1.0 mg / mL) was added to the dispersion. -1 The dispersion was stirred for 5 hours and then heated in an oil bath at 65°C for 24 hours. The product was collected by centrifugation (at 10,000 r / min) and then washed three times with 40 mL of ultrapure water to obtain the Au-C-Fe / Al-PMOF composite photocatalyst.

[0065] Example 4

[0066] HAuCl4·4H2O (48.5 mg) was dissolved in ultrapure water (30 mL) at room temperature. Then, L-glutathione (GSH, 50.0 mg) was added, and the mixture was stirred continuously. After 1 hour, the mixture was heated in an oil bath at 70°C for 24 hours. After cooling to room temperature, acetonitrile (30 mL) was added. Finally, Au NCs were washed three times (8000 rpm, 5 min) with a mixture of ultrapure water and acetonitrile (3:1 v / v), 40 mL each time. The purified Au NCs were further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0067] Au NCs dispersion (1.0 mg / mL) -1 10 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (10.0 mg) and hydroxysuccinimide (5.0 mg) were added to a 50 mL round-bottom flask and heated to 65 °C. Then, 10.0 mg of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride and 5.0 mg of hydroxysuccinimide were added as catalysts. After stirring for 30 minutes, 75 mg of L-cysteine ​​(L-cys) was added and stirring continued for 1 hour. The final mixture was stirred in a 65 °C oil bath for 10 hours to obtain Au-C. The Au-C was centrifuged four times with 40 mL of ultrapure water at 10000 rpm. The supernatant was removed on the last centrifuge. 10 mL of ultrapure water and 50 μL of NaOH solution (50% wt%) were added to the purified Au-C to promote its dispersion in the aqueous solution.

[0068] Add FeCl₂ 4H₂O (15 μmol) to 10 mL of Au-C dispersion (1.0 mg / mL). -1 After stirring continuously for 3 minutes, the mixture was centrifuged (8500 rpm, 10 minutes) to collect the yellow precipitate. The precipitate was then washed five times with 40 mL of ultrapure water to remove unreacted precursors. Residual chloride and ferrous ions were washed away by centrifugation with ultrapure water once daily for three days. Finally, the precipitate was centrifuged three times with 40 mL of ultrapure water (8000 rpm, 5 minutes each time), and dried at 60 °C for 12 hours. The purified Au-C-Fe was further uniformly dispersed in 10 mL of ultrapure water for subsequent use.

[0069] 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid (H2TCPP, 100 mg) and AlCl3·6H2O (60 mg) were added separately to ultrapure water (10 mL) and stirred at room temperature. After 3 hours, the mixture was transferred to a 50 mL reactor and heated at 180 °C for 24 hours. The mixture was then washed and centrifuged (40 mL each, 4 washes per reagent) with ultrapure water, N,N-dimethylformamide (DMF), and acetone to effectively remove unreacted precursors. The dark purple solid was freeze-dried for 15 hours for later use.

[0070] Al-PMOF (80 mg) was dispersed in 20 mL of water using ultrasound for 3 hours to obtain a dispersion. Then, 10 mL of Au-C-Fe (1.0 mg / mL) was added to the dispersion. -1 The dispersion was stirred for 5 hours and then heated in an oil bath at 65°C for 24 hours. The product was collected by centrifugation (at 10,000 r / min) and then washed three times with 40 mL of ultrapure water to obtain the Au-C-Fe / Al-PMOF composite photocatalyst.

[0071] Preparation of Au / Al-PMOF(Fe)

[0072] HAuCl4·4H2O (48.5 mg) was dissolved in ultrapure water (30 mL) at room temperature. Then, L-glutathione (GSH, 50.0 mg) was added, and the mixture was stirred continuously. After 1 hour, the mixture was heated in an oil bath at 70 °C for 24 hours. After cooling to room temperature, acetonitrile (30 mL) was added. Finally, Au NCs were washed three times (8000 rpm, 5 min) with a mixture of ultrapure water and acetonitrile (3:1 v / v), 40 mL each time. The purified Au NCs were further uniformly dispersed in 10 mL of ultrapure water to obtain Au NCs (1.0 mg / mL). -1 The dispersion is prepared for subsequent use.

[0073] 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid (H2TCPP, 100 mg) and AlCl3·6H2O (60 mg) were added separately to ultrapure water (10 mL) and stirred at room temperature. After 3 hours, the mixture was transferred to a 50 mL reactor and heated at 180 °C for 24 hours. The mixture was then washed and centrifuged (40 mL each, 4 washes per reagent) with ultrapure water, N,N-dimethylformamide (DMF), and acetone to effectively remove unreacted precursors. The dark purple solid was freeze-dried for 15 hours to obtain Al-PMOF for later use.

[0074] Al-PMOF (100 mg) and FeCl2 (50 mg) were added to DMF (30 mL) and sonicated for 30 minutes. The mixture was then continuously stirred and heated in an oil bath at 373 K for 48 hours. After cooling to room temperature, the sample was washed three times with DMF and acetone, and the resulting product was designated Al-PMOF(Fe). Finally, Al-PMOF(Fe) was dried in a vacuum oven at 393 K for 12 hours.

[0075] Al-PMOF(Fe) (80 mg) was dispersed in 20 mL of water using ultrasound for 3 hours to obtain a dispersion. Subsequently, 10 mL of Au NCs (1.0 mg / mL) was added to the dispersion. -1The dispersion was stirred for 5 hours and then heated in an oil bath at 65°C for 24 hours. The product was collected by centrifugation (10000 r / min) and then washed three times with 40 mL of ultrapure water to obtain the Au / Al-PMOF(Fe) composite photocatalyst.

[0076] 100 mg of the samples prepared in Examples 1-4 were mixed with equal amounts of Al-PMOF and Au / Al-PMOF(Fe) and subjected to X-ray diffraction testing. Figure 1 As shown, the XRD patterns of the four composite materials Au-C-Fe / Al-PMOF all showed the presence of (111) and (200) crystal phases of Au NCs, confirming that gold nanoparticles were introduced into the Al-PMOF system.

[0077] Take 100 mg of the sample prepared in Examples 1 to 4 and equal amounts of Al-PMOF and Au / Al-PMOF(Fe) and perform UV-Vis diffuse reflectance testing. Figure 2 The Al-PMOF, Au / Al-PMOF(Fe), and four Au-C-Fe / Al-PMOFs all exhibited strong absorption in the 200–800 nm range. Al-PMOF showed four q-bands in the 500–700 nm range. The q-band peak intensity of the four Au-C-Fe / Al-PMOFs was weaker compared to Al-PMOF and Au / Al-PMOF(Fe), confirming that iron ions were inserted into some of the porphyrin rings in Al-PMOF.

[0078] Photocatalytic ammonia synthesis activity testing process:

[0079] 30 mg of each of the samples from Examples 1-4, and 30 mg of pure Al-PMOF and Au / Al-PMOF(Fe) were weighed out respectively. Six experiments were set up, and the six samples were dispersed in quartz photocatalytic reactors containing 100 mL of deionized water and connected to a circulating water cooling system to maintain a temperature of 25°C. The light source was a 300 W xenon lamp (power 282 mW·cm²). -2 First, the dispersion in the quartz photocatalytic reactor was heated in the dark with high-purity N2 (at 80 mL / min). -1 After bubbling and magnetically stirring for 30 minutes at a certain rate, the N2 in the dispersion was saturated and oxygen was removed from the reactor. Then, the xenon lamp was turned on, and 1 mL of the dispersion was taken out every 60 minutes. The photocatalyst was separated by centrifugation at 5000 rpm to obtain the supernatant. The concentration of NH3 in the supernatant was determined by Nessler's reagent spectrophotometry and ion chromatography, as shown below. Figure 3 The curve shown. From Figure 3It can be seen that, compared with unmodified Al-PMOF and Au / Al-PMOF(Fe), the samples in Examples 1-4 showed significantly improved efficiency in photocatalytic conversion of nitrogen to ammonia, and NH4. + The yield was significantly increased, with Example 3 showing the best yield of 324.1 μmol g. -1 h -1 Its activity is increased by 19 times.

Claims

1. A method for preparing a doped iron porphyrin metal-organic framework photocatalyst dispersing gold nanoparticles, characterized in that, Includes the following steps: S1, chloroauric acid tetrahydrate and L-glutathione were mixed evenly in ultrapure water at a mass ratio of 9.7:10, with the ratio of chloroauric acid tetrahydrate to ultrapure water being 9.7 mg:6 mL. The mixture was then kept at 65~75℃ for 22~26 h to obtain reaction solution a. Acetonitrile was added to reaction solution a, with the volume ratio of acetonitrile to ultrapure water being 1:

1. The mixture was then washed by centrifugation with acetonitrile solution, with the volume ratio of ultrapure water to acetonitrile in the acetonitrile solution being 3:

1. Finally, the obtained product was uniformly dispersed in ultrapure water, with the ratio of ultrapure water to chloroauric acid tetrahydrate being 2 mL:9.7 mg, to obtain dispersion a. S2, 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride, hydroxysuccinimide, and L-cysteine ​​were added to dispersion a at 60-70℃ and mixed evenly. The mass ratio of L-cysteine ​​to chloroauric acid tetrahydrate in S1 was 15:9.7, and the mass ratio of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride, hydroxysuccinimide, and L-cysteine ​​was 2:1:

15. The ratio of L-cysteine ​​to reaction solution a was 5 mg:2 mL. The mixture was then kept at 60-80℃ for 8-12 h to obtain reaction solution b. The product in reaction solution b was washed and then evenly dispersed in ultrapure water and a 50% (w / w) NaOH solution. The ratio of NaOH solution, ultrapure water, and L-cysteine ​​was 0.01 mL:2 mL:15 mg to obtain dispersion b. S3, anhydrous ferrous chloride is added to dispersion b and stirred. The ratio of anhydrous ferrous chloride to dispersion b is 3 μmol: 2 mL to obtain a mixture. The product in the mixture is washed, dried and then uniformly dispersed in ultrapure water to obtain dispersion c. 4,4′,4′-(porphyrin-5,10,15,20)-tetrabenzoic acid and aluminum chloride hexahydrate were mixed evenly in ultrapure water at a mass ratio of 5:3, with an aluminum chloride hexahydrate to ultrapure water ratio of 6 mg:1 mL. The mixture was then kept at 160~200 ℃ for 20~26 h to obtain reaction solution c. The precipitate in reaction solution c was washed and dried to obtain the product. The product was evenly dispersed in ultrapure water to obtain dispersion d. Dispersion c and dispersion d were mixed evenly at a volume ratio of (3~10):20 and kept at 60~70 ℃ in an oil bath for 22~26 h to obtain reaction solution d. The product in reaction solution d was washed to obtain a gold nanoparticle-doped iron porphyrin metal-organic framework photocatalyst.

2. The method for preparing a doped iron-porphyrin metal-organic framework photocatalyst dispersing gold nanoparticles according to claim 1, characterized in that, In S3, anhydrous ferrous chloride is added to dispersion b and stirred for 2.5-3.5 min to obtain a mixture. The mixture is first washed 3-5 times with 30-50 mL of ultrapure water by centrifugation to obtain a preliminary washed product. The preliminary washed product is then soaked in 30-50 mL of ultrapure water for 22-26 h and then washed by centrifugation. The product is then soaked in 30-50 mL of ultrapure water for 22-26 h and then washed by centrifugation. This process is repeated 3-5 times in total to obtain a secondary washed product. The secondary washed product is then washed 3-5 times with 30-50 mL of ultrapure water by centrifugation. The resulting precipitate is dried at 55-65 °C for 10-14 h and then uniformly dispersed in ultrapure water of the same volume as dispersion b to obtain dispersion c.

3. The method for preparing a doped iron-porphyrin metal-organic framework photocatalyst dispersing gold nanoparticles according to claim 1, characterized in that, S3 The precipitate in reaction solution c was centrifuged sequentially with ultrapure water, N,N-dimethylformamide and acetone, and then freeze-dried for 14-16 h to obtain the product. Finally, the product was uniformly dispersed in ultrapure water at a ratio of 4 mg:1 mL to obtain dispersion d.

4. A doped iron porphyrin metal-organic framework photocatalyst of dispersed gold nanoparticles obtained by the preparation method of the doped iron porphyrin metal-organic framework photocatalyst of dispersed gold nanoparticles according to any one of claims 1 to 3.

5. The application of the iron porphyrin metal-organic framework photocatalyst with dispersed gold nanoparticles as described in claim 4 in the photocatalytic conversion of nitrogen into ammonia.

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