Iron atomic distance controllable catalyst and application thereof

Abstract

The application discloses a kind of catalysts with controllable iron atomic spacing and its application, first organic ligand (thioacetamide or hydroxylamine hydrochloride) is formed with divalent iron ion and contains different coordination configuration iron complex, and the encapsulation is completed by the hydrogen bond formation supramolecular process between melamine and cyanuric acid.Then, in argon atmosphere, catalysts with controllable iron atomic spacing are synthesized by high-temperature pyrolysis method.The application also includes the application of catalysts with different iron atomic spacing to remove phenolic benzene series in water.In which, the increase of iron loading will cause iron agglomeration phenomenon;And the introduction of bridging sulfur can not only shorten the distance between two adjacent iron atoms and improve the loading of single iron atom in the catalyst, but also can control the occupation state electron density of adjacent iron atoms d orbital, improve the utilization rate of persulfate and the content and selectivity of high-valence state iron oxide.Highly efficient degradation of p-chlorophenol in surface water, and has good reusability.

Description

Technical Field

[0001] This invention belongs to the field of materials engineering and environmental engineering technology, specifically relating to a catalyst with controllable iron atom spacing and its application. Background Technology

[0002] Iron-based nanomaterials activate persulfate (PMS) to generate free radicals, demonstrating a highly efficient ability to degrade organic pollutants. However, the selectivity of free radical degradation of organic pollutants is poor, and it is easily affected by anions, cations, and natural organic matter in water bodies, leading to problems such as low PMS utilization efficiency, low free radical yield, and poor resistance to environmental interference. In recent years, the ability of non-free radicals to efficiently utilize PMS for rapid degradation of electron-rich pollutants has attracted much attention. Among them, high-valence oxides (M... n+2 =O is a non-free radical with strong redox capabilities (>1.95 eV), multiple oxidation mechanisms (single / double electron transfer, electron addition, oxygen atom transfer, etc.), and a long lifetime (approximately 7-10 eV). -1 Advantages include (s). However, when iron-based nanomaterials activate PMS, their molecular structure (HSO5) is directly broken. - The OO bond within the iron oxide (Fe) cannot undergo the OH dissociation process, making it difficult to selectively generate high-valence iron oxides (Fe). IV =O). Iron single-atom catalysts (Fe SAC) not only possess characteristics such as being green, inexpensive, and resembling natural biological enzymes, but also exhibit excellent binding ability with oxygen sites within PMS molecules. However, electron-rich iron atoms more readily bind to terminal oxygen groups, causing the OH bond to break and undergo a disproportionation reaction, resulting in highly selective generation of singlet oxygen ( =O). 1 O2). Therefore, it is difficult for a single iron atom to activate PMS to generate Fe with high selectivity. IV =O. The bridging configuration not only optimizes the effective distance between adjacent bimetallic or polymetallic atoms, but also facilitates the synergistic effect between two or more metal atoms. Furthermore, sulfur atoms often exhibit a larger covalent radius and lower electronegativity than nitrogen and carbon atoms. By designing a bridging sulfur structure, it is possible to not only suppress the aggregation of two or more iron atoms to form iron clusters, but also weaken the number of occupied electrons in the d orbitals of two or more iron atoms. However, the reported synthetic methods have resulted in a random distribution of iron atom spacing in Fe SAC, leading to an uncontrollable content and coordination configuration of bridging sulfur, iron atoms, and their coordination configuration. We found that the introduction of bridging sulfur regulates the distance between two iron atoms. Furthermore, by increasing the content of bridging sulfur, we can increase the iron atom loading and optimize the electron density in the d orbitals of iron atoms, reduce the energy required for OH dissociation, and increase the utilization efficiency of Fe SAC for PMS and Fe... IVThe amount of =O generated and the selectivity thereof. Therefore, a synthesis method of a catalyst with controllable iron atomic spacing is established, the application of green and efficient removal of phenolic benzene series in water is realized, and the cost of treating surface water pollution is reduced. SUMMARY

[0003] The present application aims at the deficiencies of the prior art and provides a catalyst with controllable iron atomic spacing and applications thereof.

[0004] The purpose of the present application is achieved by the following technical solutions.

[0005] In a first aspect, the present application provides a catalyst with controllable iron atomic spacing, which is synthesized by the following steps:

[0006] S1: Dissolve melamine in deionized water at 70-90 DEG C to obtain a melamine solution; dissolve cyanuric acid in deionized water at 70-90 DEG C to obtain a cyanuric acid solution; dissolve ferrous sulfate heptahydrate in deionized water at 20-30 DEG C to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid and ferrous sulfate is 1:0.5-0.9:0.5-0.2;

[0007] S2: Pour thioacetamide into the ferrous sulfate solution obtained in step S1, uniformly stir at 20-30 DEG C for 5-10 min to obtain solution a; the molar ratio of thioacetamide and ferrous sulfate is 1:0.2-0.8;

[0008] S3: Pour solution a obtained in step S2 into the cyanuric acid solution obtained in step S1, uniformly stir at 70-90 DEG C for 5-10 min, then pour the mixed solution into the melamine solution obtained in step S1, stir for 2-4 h for co-precipitation reaction, then perform solid-liquid separation and washing, and blow dry at 55-60 DEG C for 6-8 h to obtain a supramolecular solid;

[0009] S4: Under the protection of argon atmosphere, heat the supramolecular solid obtained in step S3 to 550-650 DEG C, keep warm for 3-5 h, then cool to room temperature to obtain a catalyst with controllable iron atomic spacing, denoted as Fe1-S-Fe1 / CN.

[0010] In a second aspect, the present application also provides a catalyst with controllable iron atomic spacing, which is synthesized by the following steps:

[0011] S1: melamine is dissolved in deionized water at 70-90 DEG C to obtain a melamine solution; cyanuric acid is dissolved in deionized water at 70-90 DEG C to obtain a cyanuric acid solution; ferrous sulfate heptahydrate is dissolved in deionized water at 20-30 DEG C to obtain a ferrous sulfate solution; the molar ratio of the melamine, cyanuric acid and ferrous sulfate is 1:0.5-0.9:0.5-0.2;

[0012] S2: hydroxylamine hydrochloride is poured into the ferrous sulfate solution obtained in step S1, and stirred uniformly at 20-30 DEG C for 5-10 min to obtain solution a; the molar ratio of the hydroxylamine hydrochloride and ferrous sulfate is 1:0.2-0.8;

[0013] S3: solution a obtained in step S2 is poured into the cyanuric acid solution obtained in step S1, and stirred uniformly at 70-90 DEG C for 5-10 min, then the mixed solution is poured into the melamine solution obtained in step S1, and stirred for 1-3 h for co-precipitation reaction, then solid-liquid separation and washing are carried out, and air drying is carried out at 55-60 DEG C for 6-8 h to obtain a supramolecular solid;

[0014] S4: the supramolecular solid obtained in step S3 is heated to 550-650 DEG C under argon atmosphere protection, and cooled to room temperature after holding for 3-5 h to obtain a catalyst with controllable iron atomic spacing, denoted as Fe1-Fe1 / CN.

[0015] In a third aspect, the application provides a use of a catalyst with controllable iron atomic spacing for removing phenolic benzene series in a surface water body, comprising the following steps: pouring the catalyst with controllable iron atomic spacing and persulfate into the surface water body, the water body temperature is 20-30 DEG C, and stirring reaction is carried out for 10-15 min to complete the removal of phenolic benzene series in the surface water body; the addition amount of the catalyst with controllable iron atomic spacing is 0.2-0.6 g / L; the addition amount of the persulfate is 100-600 μmol / L; and the concentration of the phenolic benzene series is 0-200 μmol / L.

[0016] Further, the phenolic benzene series is phenol, p-chlorophenol, p-hydroxybenzoic acid or p-nitrophenol.

[0017] The application has the following beneficial effects:

[0018] (1) By adjusting the addition amount of thioacetamide and ferrous sulfate heptahydrate, controllable synthesis of bridged sulfur content and iron atomic spacing is realized, and the performance of Fe1-S-Fe1 / CN, such as the activation efficiency of PMS, the content of Fe IV =O and its selectivity, is analyzed;

[0019] (2) By introducing bridging sulfur, the distance between two adjacent iron atoms is shortened, the atomic-level iron loading in the catalyst is increased, the electron density of the occupied states on the d orbitals of iron atoms is weakened, and the Fe1-S-Fe1 / CN activated PMS is increased to generate Fe. IV =O yield and selectivity, enhancing the ability to degrade phenolic benzene compounds;

[0020] (3) By adjusting the dosage of hydroxylamine hydrochloride and ferrous sulfate heptahydrate, as well as the stirring time for co-precipitation, the iron loading and iron atom spacing were controlled for synthesis. The efficiency of Fe1-Fe1 / CN in activating PMS and the generation of... 1 Properties such as O2 content and selectivity;

[0021] (4) Fe1-S-Fe1 / CN activated PMS efficiently degrades p-chlorophenol (4-CP) in surface water and has good reusability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the distance between iron atoms in the catalysts prepared in Examples 7, 11, and Comparative Example 1;

[0023] Figure 2 The image shows a high-angle annular dark-field scanning transmission electron microscope image of the catalyst prepared in Example 7 with spherical aberration correction and the elemental distribution spectrum of Fe and S.

[0024] Figure 3 Aberration-corrected high-angle annular dark-field scanning transmission electron microscope image and Fe and S elemental distribution spectrum of the catalyst prepared in Example 11;

[0025] Figure 4 High-angle annular dark-field scanning transmission electron microscope image and Fe and S elemental distribution spectrum of the catalyst prepared in Comparative Example 1, corrected for spherical aberration.

[0026] Figure 5 The statistical and Rayleigh model fitting plots of the iron atom spacing in the catalysts prepared in Examples 7, 11 and Comparative Example 1 are shown.

[0027] Figure 6 The X-ray diffraction patterns are shown for the catalysts prepared in Examples 7, 11, and Comparative Example 1, and for the graphitic carbon nitride prepared in Comparative Example 2. Figure 6 (a) X-ray diffraction patterns of the catalysts prepared in Examples 7, 11 and Comparative Example 1, and the graphitic carbon nitride prepared in Comparative Example 2; Figure 6 (b) is a magnified detail and schematic diagram of the X-ray diffraction pattern of the catalysts prepared in Examples 7, 11 and Comparative Example 1 and the graphitic carbon nitride prepared in Comparative Example 2 at the 100 crystal plane.Figure 6 (c) Enlarged detail of the X-ray diffraction pattern at the 002 plane and a model illustration for the catalysts prepared in Example 7, Example 11 and Comparative Example 1 and the graphite phase of carbon nitride prepared in Comparative Example 2;

[0028] Figure 7 Comparison plot between the iron atom loadings in the catalysts prepared in Example 1 to Example 11;

[0029] Figure 8 R-space X-ray extended-edge absorption fine structure spectra of the Fourier transform Fe K-edge for the catalysts prepared in Example 7, Example 11, Comparative Example 1, FeS, Fe3N and iron foil

[0030] Figure 9 X-ray photoelectron spectroscopy plots for the catalysts prepared in Example 7, Example 11 and Comparative Example 1 and the graphite phase of carbon nitride prepared in Comparative Example 2, wherein, Figure 9 (a) S 2p plots for the catalysts prepared in Example 7, Example 11 and Comparative Example 1 and the graphite phase of carbon nitride prepared in Comparative Example 2; Figure 9 (b) Fe 2p plots for the catalysts prepared in Example 7, Example 11 and Comparative Example 1 and the graphite phase of carbon nitride prepared in Comparative Example 2; Figure 9 (c) C 1s plots for the catalysts prepared in Example 7, Example 11 and Comparative Example 1 and the graphite phase of carbon nitride prepared in Comparative Example 2; Figure 9 (d) N 1s plots for the catalysts prepared in Example 7, Example 11 and Comparative Example 1 and the graphite phase of carbon nitride prepared in Comparative Example 2;

[0031] Figure 10 Fe K-edge X-ray absorption near-edge structure spectra for the catalysts prepared in Example 7, Example 11, Comparative Example 1, FeO, Fe2O3 and Fe3O4;

[0032] Figure 11 Comparison plot of the d-orbital state density of the iron atom in the catalysts prepared in Example 7, Example 11;

[0033] Figure 12 Plot of the concentration change of 4-CP during the degradation of 4-CP by the catalysts prepared in Example 7, Example 11 and Comparative Example 1 activated by PMS and comparison plot of the degradation rate thereof, wherein, Figure 12 (a) Plot of the concentration change of 4-CP during the degradation of 4-CP by the catalysts prepared in Example 7, Example 11 and Comparative Example 1 activated by PMS, Figure 12(b) is a comparison graph showing the degradation rate of 4-CP by PMS activated by the catalysts prepared in Example 7, Example 11 and Comparative Example 1;

[0034] Figure 13 Comparative figures show the quencher capture experiments of the catalysts prepared in Examples 7, 11, and 1 (for PMS degradation of 4-CP) to activate PMS.

[0035] Figure 14 This is a comparison chart showing the concentration changes and utilization rates of PMS during the degradation of 4-CP by the catalysts prepared in Examples 7, 11, and Comparative Example 1. Figure 14 (a) is a graph showing the concentration change of PMS during the degradation of 4-CP by PMS activated by the catalysts prepared in Examples 7, 11, and Comparative Example 1. Figure 14 (b) is a comparison chart of the utilization rate of PMS during the degradation of 4-CP by the catalysts prepared in Examples 7, 11 and Comparative Example 1;

[0036] Figure 15 The degradation rate of 4-CP and Fe by the catalytically modified PMS prepared in Examples 1-8 are shown. IV =O / 1 Correlation diagram between O2 and sulfur / iron molar ratio;

[0037] Figure 16 The catalysts prepared in Examples 7 and 11 were used to activate PMS to generate Fe. IV =Energy barrier change diagram for each step of the O process;

[0038] Figure 17 This is a comparison graph showing the degradation rates of different phenolic benzene compounds by PMS activated with the catalysts prepared in Examples 7, 11, and 1 (Comparative Example 1).

[0039] Figure 18 This is a correlation diagram showing the relationship between the degradation rate of different phenolic benzene compounds by PMS activated by the catalyst prepared in Example 7 and their functional group isopotentials.

[0040] Figure 19 The graph shows the number of times the catalyst prepared in Example 7 was reused in the PMS degradation of 4-CP and the iron ion dissolution rate. Figure 19 (a) is a graph showing the number of times the catalyst prepared in Example 7 can be reused to activate the PMS degradation of 4-CP. Figure 19 (b) is a graph showing the iron ion dissolution rate during the degradation of 4-CP by PMS activated by the catalyst prepared in Example 7. Detailed Implementation

[0041] In order to make the objectives, technical solutions and advantages of the present application clearer, further understand the present application, the present application will be further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0042] The experimental methods described in the following examples are all conventional methods unless otherwise specified. The reagents and materials described are all commercially available unless otherwise specified.

[0043] The present application provides a catalyst with controllable iron atomic distance. One kind of catalyst with controllable iron atomic distance by controlling the dosing amount of thioacetamide and ferrous sulfate heptahydrate to realize the preparation of bridging sulfur, denoted as Fe1-S-Fe1 / CN, such as example 1, example 2, example 3, example 4, example 5, example 6, example 7 and example 8. Another kind of catalyst with controllable iron atomic distance by controlling the dosing amount of hydroxylamine hydrochloride and ferrous sulfate heptahydrate to realize the preparation of iron loading, denoted as Fe1-Fe1 / CN, such as example 9, example 10 and example 11.

[0044] Example 1: Catalyst with controllable iron atomic distance by bridging sulfur (0.04-Fe1-S-Fe1 / CN) is synthesized by the following steps:

[0045] S1: weigh 1.0 g of melamine into 100 ml of deionized water, heat to 80℃ for dissolution, to obtain a melamine solution; weigh 0.8 g of cyanuric acid into 120 ml of deionized water, heat to 80℃ for dissolution, to obtain a cyanuric acid solution; weigh 0.22 g of ferrous sulfate heptahydrate into 60 ml of deionized water, dissolve at 25℃, to obtain a ferrous sulfate solution;

[0046] S2: weigh 0.03 g of thioacetamide and pour it into the ferrous sulfate solution obtained in step S1, uniformly stir at 25℃ for 10 min, to obtain solution a;

[0047] S3: pour solution a obtained in step S2 into the cyanuric acid solution obtained in step S1, uniformly stir at 80℃ for 10 min, then pour the mixed solution into the melamine solution obtained in step S1, stir for 3 h for co-precipitation reaction, after stirring, solid-liquid separation is performed, washed with deionized water and ethanol alternately for 3 times each, and dried at 60℃ with air blowing for 8 h, to obtain a supramolecular solid;

[0048] S4: The supramolecular solid obtained in step S3 was heated to 550 ℃ at a temperature increasing rate of 5 ℃ / min under the protection of high-purity argon (purity of 99.99%) and kept for 4 h, and then cooled to room temperature to obtain a bridged sulfur-regulated iron atomic distance catalyst, denoted as 0.04-Fe1-S-Fe1 / CN.

[0049] The actual sulfur-iron molar ratio of the bridged sulfur-regulated iron atomic distance catalyst prepared in Example 1 was 0.04, and thus it was denoted as 0.04-Fe1-S-Fe1 / CN.

[0050] Example 2: A bridged sulfur-regulated iron atomic distance catalyst (0.08-Fe1-S-Fe1 / CN) was synthesized by the following steps:

[0051] S1: 1.0 g of melamine was weighed into 100 ml of deionized water, heated to 80 ℃ for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 ml of deionized water, heated to 80 ℃ for dissolution to obtain a cyanuric acid solution; 0.22 g of ferrous sulfate heptahydrate was weighed into 60 ml of deionized water, dissolved at 25 ℃ to obtain a ferrous sulfate solution;

[0052] S2: 0.06 g of thioacetamide was weighed and added to the ferrous sulfate solution obtained in step S1, and uniformly stirred at 25 ℃ for 10 min to obtain solution a;

[0053] S3: Solution a obtained in step S2 was poured into the cyanuric acid solution obtained in step S1, and uniformly stirred at 80 ℃ for 10 min, then the mixed solution was poured into the melamine solution obtained in step S1, and stirred for 3 h for co-precipitation reaction, and then solid-liquid separation was performed, and deionized water and ethanol were alternately washed for 3 times each, and air-dried at 60 ℃ for 8 h to obtain a supramolecular solid;

[0054] S4: The supramolecular solid obtained in step S3 was heated to 550 ℃ at a temperature increasing rate of 5 ℃ / min under the protection of high-purity argon (purity of 99.99%) and kept for 4 h, and then cooled to room temperature to obtain a bridged sulfur-regulated iron atomic distance catalyst, denoted as 0.08-Fe1-S-Fe1 / CN.

[0055] The actual sulfur-iron molar ratio of the bridged sulfur-regulated iron atomic distance catalyst prepared in Example 2 was 0.08, and thus it was denoted as 0.08-Fe1-S-Fe1 / CN.

[0056] Example 3: A bridged sulfur-regulated iron atomic distance catalyst (0.10-Fe1-S-Fe1 / CN) was synthesized by the following steps:

[0057] S1: 1.0 g of melamine was weighed into 100 mL of deionized water, heated to 80°C for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 mL of deionized water, heated to 80°C for dissolution to obtain a cyanuric acid solution; 0.22 g of ferrous sulfate heptahydrate was weighed into 60 mL of deionized water, dissolved at 25°C to obtain a ferrous sulfate solution;

[0058] S2: 0.12 g of thioacetamide was weighed and added to the ferrous sulfate solution obtained in step S1, and uniformly stirred at 25°C for 10 min to obtain solution a;

[0059] S3: Solution a obtained in step S2 was poured into the cyanuric acid solution obtained in step S1, and uniformly stirred at 80°C for 10 min, then the mixed solution was poured into the melamine solution obtained in step S1, and stirred for 3 h for co-precipitation reaction, and then solid-liquid separation was performed, and deionized water and ethanol were alternately washed for 3 times each, and air-dried at 60°C for 8 h to obtain a supramolecular solid;

[0060] S4: The supramolecular solid obtained in step S3 was heated to 550°C at a heating rate of 5°C / min under the protection of high-purity argon (purity 99.99%) and kept for 4 h, and then cooled to room temperature to obtain a bridged sulfur-regulated iron atomic distance catalyst, denoted as 0.10-Fe1-S-Fe1 / CN.

[0061] The actual sulfur-iron molar ratio of the bridged sulfur-regulated iron atomic distance catalyst prepared in Example 3 was 0.10, so it was denoted as 0.10-Fe1-S-Fe1 / CN.

[0062] Example 4: A bridged sulfur-regulated iron atomic distance catalyst (0.14-Fe1-S-Fe1 / CN) was synthesized by the following steps:

[0063] S1: 1.0 g of melamine was weighed into 100 mL of deionized water, heated to 80°C for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 mL of deionized water, heated to 80°C for dissolution to obtain a cyanuric acid solution; 0.44 g of ferrous sulfate heptahydrate was weighed into 60 mL of deionized water, dissolved at 25°C to obtain a ferrous sulfate solution;

[0064] S2: 0.12 g of thioacetamide was weighed and added to the ferrous sulfate solution obtained in step S1, and uniformly stirred at 25°C for 10 min to obtain solution a;

[0065] S3: Pour the solution a obtained in step S2 into the cyanic acid solution obtained in step S1, and uniformly stir at 80°C for 10 min. Then, pour the mixed solution into the melamine solution obtained in step S1, and stir for 3 h to perform a co-precipitation reaction. After the stirring is completed, perform a solid-liquid separation, wash with deionized water and ethanol alternately for 3 times, and perform air blowing drying at 60°C for 8 h to obtain a supramolecular solid;

[0066] S4: Under the protection of high-purity argon gas (purity is 99.99%), heat the supramolecular solid obtained in step S3 to 550°C at a temperature rising speed of 5°C / min, and keep the temperature for 4 h. After cooling to room temperature, a bridged sulfur-regulated iron atomic spacing catalyst is obtained, which is recorded as 0.14-Fe1-S-Fe1 / CN.

[0067] The actual sulfur-iron molar ratio of the bridged sulfur-regulated iron atomic spacing catalyst prepared in Example 4 is 0.14, and thus it is recorded as 0.14-Fe1-S-Fe1 / CN.

[0068] Example 5: A bridged sulfur-regulated iron atomic spacing catalyst (0.15-Fe1-S-Fe1 / CN) is synthesized by the following steps:

[0069] S1: Weigh 1.0 g of melamine into 100 ml of deionized water, heat to 80°C to dissolve, and obtain a melamine solution. Weigh 0.8 g of cyanic acid into 120 ml of deionized water, heat to 80°C to dissolve, and obtain a cyanic acid solution. Weigh 0.11 g of ferrous sulfate heptahydrate into 60 ml of deionized water, and dissolve at 25°C to obtain a ferrous sulfate solution;

[0070] S2: Weigh 0.06 g of thioacetamide and pour it into the ferrous sulfate solution obtained in step S1, and uniformly stir at 25°C for 10 min to obtain solution a;

[0071] S3: Pour the solution a obtained in step S2 into the cyanic acid solution obtained in step S1, and uniformly stir at 80°C for 10 min. Then, pour the mixed solution into the melamine solution obtained in step S1, and stir for 3 h to perform a co-precipitation reaction. After the stirring is completed, perform a solid-liquid separation, wash with deionized water and ethanol alternately for 3 times, and perform air blowing drying at 60°C for 8 h to obtain a supramolecular solid;

[0072] S4: Under the protection of high-purity argon gas (purity is 99.99%), heat the supramolecular solid obtained in step S3 to 550°C at a temperature rising speed of 5°C / min, and keep the temperature for 4 h. After cooling to room temperature, a bridged sulfur-regulated iron atomic spacing catalyst is obtained, which is recorded as 0.15-Fe1-S-Fe1 / CN.

[0073] The measured sulfur-to-iron molar ratio of the bridged sulfur-regulated iron atomic distance catalyst prepared in Example 5 is 0.15, and thus is denoted as 0.15-Fe1-S-Fe1 / CN.

[0074] The bridged sulfur-regulated iron atomic distance catalyst (0.17-Fe1-S-Fe1 / CN) of Example 6 is synthesized by the following steps:

[0075] S1: 1.0 g of melamine was weighed into 100 mL of deionized water, heated to 80°C for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 mL of deionized water, heated to 80°C for dissolution to obtain a cyanuric acid solution; 0.11 g of ferrous sulfate heptahydrate was weighed into 60 mL of deionized water, dissolved at 25°C to obtain a ferrous sulfate solution;

[0076] S2: 0.12 g of thioacetamide was weighed and added to the ferrous sulfate solution obtained in step S1, and stirred uniformly at 25°C for 10 min to obtain solution a;

[0077] S3: Solution a obtained in step S2 was poured into the cyanuric acid solution obtained in step S1, and stirred uniformly at 80°C for 10 min, and then the mixed solution was poured into the melamine solution obtained in step S1, and stirred for 3 h for co-precipitation reaction. After the stirring was completed, solid-liquid separation was performed, and the product was washed with deionized water and ethanol alternately for 3 times each, and then dried at 60°C with air blowing for 8 h to obtain a supramolecular solid;

[0078] S4: The supramolecular solid obtained in step S3 was heated to 550°C at a temperature increasing rate of 5°C / min under the protection of high-purity argon (purity of 99.99%) and kept for 4 h, and then cooled to room temperature to obtain a bridged sulfur-regulated iron atomic distance catalyst, denoted as 0.17-Fe1-S-Fe1 / CN.

[0079] The measured sulfur-to-iron molar ratio of the bridged sulfur-regulated iron atomic distance catalyst prepared in Example 6 is 0.17, and thus is denoted as 0.17-Fe1-S-Fe1 / CN.

[0080] The bridged sulfur-regulated iron atomic distance catalyst (0.20-Fe1-S-Fe1 / CN) of Example 7 is synthesized by the following steps:

[0081] S1: 1.0 g of melamine was weighed into 100 mL of deionized water, heated to 80°C for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 mL of deionized water, heated to 80°C for dissolution to obtain a cyanuric acid solution; 0.11 g of ferrous sulfate heptahydrate was weighed into 60 mL of deionized water, dissolved at 25°C to obtain a ferrous sulfate solution;

[0082] S2: 0.18 g of thioacetamide was weighed and poured into the ferrous sulfate solution obtained in step S1, and stirred uniformly at 25°C for 10 min to obtain solution a;

[0083] S3: Solution a obtained in step S2 was poured into the cyanuric acid solution obtained in step S1, and stirred uniformly at 80°C for 10 min, and then the mixed solution was poured into the melamine solution obtained in step S1, and stirred for 3 h to perform the coprecipitation reaction, and after the stirring was completed, solid-liquid separation was performed, and each was washed with deionized water and ethanol alternately for 3 times, and air-dried at 60°C for 8 h to obtain a supramolecular solid;

[0084] S4: The supramolecular solid obtained in step S3 was heated to 550°C at a temperature increasing rate of 5°C / min under the protection of high-purity argon (purity 99.99%) and kept for 4 h, and then cooled to room temperature to obtain a bridged sulfur-regulated iron atomic distance catalyst, which was recorded as 0.20-Fe1-S-Fe1 / CN.

[0085] The actual sulfur-iron molar ratio of the bridged sulfur-regulated iron atomic distance catalyst prepared in Example 7 was 0.20, and therefore it was recorded as 0.20-Fe1-S-Fe1 / CN.

[0086] Example 8: A bridged sulfur-regulated iron atomic distance catalyst (0.23-Fe1-S-Fe1 / CN) was synthesized by the following steps:

[0087] S1: 1.0 g of melamine was weighed and poured into 100 ml of deionized water, and dissolved by heating to 80°C to obtain a melamine solution; 0.8 g of cyanuric acid was weighed and poured into 120 ml of deionized water, and dissolved by heating to 80°C to obtain a cyanuric acid solution; 0.11 g of ferrous sulfate heptahydrate was weighed and poured into 60 ml of deionized water, and dissolved at 25°C to obtain a ferrous sulfate solution;

[0088] S2: 0.24 g of thioacetamide was weighed and poured into the ferrous sulfate solution obtained in step S1, and stirred uniformly at 25°C for 10 min to obtain solution a;

[0089] S3: Solution a obtained in step S2 was poured into the cyanuric acid solution obtained in step S1, and stirred uniformly at 80°C for 10 min, and then the mixed solution was poured into the melamine solution obtained in step S1, and stirred for 3 h to perform the coprecipitation reaction, and after the stirring was completed, solid-liquid separation was performed, and each was washed with deionized water and ethanol alternately for 3 times, and air-dried at 60°C for 8 h to obtain a supramolecular solid;

[0090] S4: The supramolecular solid obtained in step S3 was heated to 550 ℃ at a temperature increasing rate of 5 ℃ / min under the protection of high-purity argon (purity of 99.99%) and kept for 4 h, and then cooled to room temperature to obtain a bridged sulfur-regulated iron atomic distance catalyst, denoted as 0.23-Fe1-S-Fe1 / CN.

[0091] The actual sulfur-iron molar ratio of the bridged sulfur-regulated iron atomic distance catalyst prepared in Example 8 was 0.23, and thus it was denoted as 0.23-Fe1-S-Fe1 / CN.

[0092] Example 9: An iron loading-regulated iron atomic distance catalyst (0.031-Fe1-Fe1 / CN) was synthesized by the following steps:

[0093] S1: 1.0 g of melamine was weighed into 100 ml of deionized water, heated to 80 ℃ for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 ml of deionized water, heated to 80 ℃ for dissolution to obtain a cyanuric acid solution; 0.11 g of ferrous sulfate heptahydrate was weighed into 60 ml of deionized water, and dissolved at 25 ℃ to obtain a ferrous sulfate solution;

[0094] S2: 0.24 g of hydroxylamine hydrochloride was weighed and added to the ferrous sulfate solution obtained in step S1, and uniformly stirred at 25 ℃ for 10 min to obtain solution a;

[0095] S3: Solution a obtained in step S2 was poured into the cyanuric acid solution obtained in step S1, and uniformly stirred at 80 ℃ for 10 min, then the mixed solution was poured into the melamine solution obtained in step S1, and stirred for 3 h for co-precipitation reaction, and then solid-liquid separation was performed, and deionized water and ethanol were alternately washed for 3 times each, and air-dried at 60 ℃ for 8 h to obtain a supramolecular solid;

[0096] S4: The supramolecular solid obtained in step S3 was heated to 550 ℃ at a temperature increasing rate of 5 ℃ / min under the protection of high-purity argon (purity of 99.99%) and kept for 4 h, and then cooled to room temperature to obtain an iron loading-regulated iron atomic distance catalyst, denoted as 0.031-Fe1-Fe1 / CN.

[0097] The actual iron content of the iron loading-regulated iron atomic distance catalyst prepared in Example 9 was 3.1 wt.%, and thus it was denoted as 0.031-Fe1-Fe1 / CN.

[0098] Example 10: An iron loading-regulated iron atomic distance catalyst (0.022-Fe1-Fe1 / CN) was synthesized by the following steps:

[0099] S1: 1.0 g of melamine was weighed into 100 mL of deionized water, heated to 80°C for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 mL of deionized water, heated to 80°C for dissolution to obtain a cyanuric acid solution; 0.11 g of ferrous sulfate heptahydrate was weighed into 60 mL of deionized water, dissolved at 25°C to obtain a ferrous sulfate solution;

[0100] S2: 0.24 g of hydroxylamine hydrochloride was weighed and added to the ferrous sulfate solution obtained in step S1, and uniformly stirred at 25°C for 10 min to obtain solution a;

[0101] S3: Solution a obtained in step S2 was added to the cyanuric acid solution obtained in step S1, and uniformly stirred at 80°C for 10 min, then the mixed solution was added to the melamine solution obtained in step S1, and stirred for 2 h for co-precipitation reaction. After the stirring was completed, solid-liquid separation was performed, and deionized water and ethanol were alternately washed for 3 times each, and air-dried at 60°C for 8 h to obtain a supramolecular solid;

[0102] S4: The supramolecular solid obtained in step S3 was heated to 550°C at a heating rate of 5°C / min under the protection of high-purity argon (purity 99.99%) and kept for 4 h, and then cooled to room temperature to obtain an iron loading controlled iron atomic spacing catalyst, denoted as 0.022-Fe1-Fe1 / CN.

[0103] The actual iron content of the iron loading controlled iron atomic spacing catalyst prepared in Example 10 was 2.2 wt.%, so it was denoted as 0.022-Fe1-Fe1 / CN.

[0104] Example 11 Iron loading controlled iron atomic spacing catalyst (0.015-Fe1-Fe1 / CN) was synthesized by the following steps:

[0105] S1: 1.0 g of melamine was weighed into 100 mL of deionized water, heated to 80°C for dissolution to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 mL of deionized water, heated to 80°C for dissolution to obtain a cyanuric acid solution; 0.11 g of ferrous sulfate heptahydrate was weighed into 60 mL of deionized water, dissolved at 25°C to obtain a ferrous sulfate solution;

[0106] S2: 0.24 g of hydroxylamine hydrochloride was weighed and added to the ferrous sulfate solution obtained in step S1, and uniformly stirred at 25°C for 10 min to obtain solution a;

[0107] S3: Pour the solution a obtained in step S2 into the cyanic acid solution obtained in step S1, and uniformly stir at 80°C for 10 min. Then, pour the mixed solution into the melamine solution obtained in step S1, and stir for 1 h to perform a coprecipitation reaction. After the stirring is completed, perform solid-liquid separation, wash with deionized water and ethanol alternately for 3 times, and perform air blowing drying at 60°C for 8 h to obtain a supramolecular solid;

[0108] S4: Under the protection of high-purity argon gas (purity 99.99%), heat the supramolecular solid obtained in step S3 to 550°C at a temperature increasing rate of 5°C / min, and keep the temperature for 4 h. After cooling to room temperature, an iron atomic spacing controlled catalyst with an iron loading is obtained, which is recorded as 0.015-Fe1-Fe1 / CN.

[0109] The actual iron content of the iron atomic spacing controlled catalyst prepared in Example 11 is 1.5 wt.%, and thus it is recorded as 0.015-Fe1-Fe1 / CN.

[0110] The iron single-atom catalyst (Fe1 / CN) of Comparative Example 1 is synthesized by the following steps:

[0111] S1: Weigh 1.0 g of melamine into 100 ml of deionized water, and dissolve at 80°C to obtain a melamine solution. Weigh 0.8 g of cyanic acid into 120 ml of deionized water, and dissolve at 80°C to obtain a cyanic acid solution. Weigh 0.162 g of iron nitrate nonahydrate into 60 ml of deionized water, and dissolve at 25°C to obtain a ferrous sulfate solution;

[0112] S2: Weigh 0.168 g of citric acid into the ferrous sulfate solution obtained in step S1, and uniformly stir at 25°C for 10 min to obtain solution a;

[0113] S3: Pour the solution a obtained in step S2 into the cyanic acid solution obtained in step S1, and uniformly stir at 80°C for 10 min. Then, pour the mixed solution into the melamine solution obtained in step S1, and stir for 3 h to perform a coprecipitation reaction. After the stirring is completed, perform solid-liquid separation, wash with deionized water and ethanol alternately for 3 times, and perform air blowing drying at 60°C for 8 h to obtain a supramolecular solid;

[0114] S4: Under the protection of high-purity argon gas (purity 99.99%), heat the supramolecular solid obtained in step S3 to 550°C at a temperature increasing rate of 5°C / min, and keep the temperature for 4 h. After cooling to room temperature, an iron single-atom catalyst is obtained, which is recorded as Fe1 / CN.

[0115] The comparative example 1 prepared an iron monatomic catalyst with an iron atom loading of 8.9 wt.%, which was close to the iron atom loading of the iron monatomic catalysts prepared in examples 1 to 3, example 7 and example 8. In order to conveniently compare and analyze the differences in catalytic performance and selectivity of each, it was recorded as Fe1 / CN.

[0116] The comparative example 2 graphite phase carbon nitride (CN) was synthesized by the following steps:

[0117] S1: 1.0 g of melamine was weighed into 100 ml of deionized water, heated to 80°C for dissolution, to obtain a melamine solution; 0.8 g of cyanuric acid was weighed into 120 ml of deionized water, heated to 80°C for dissolution, to obtain a cyanuric acid solution;

[0118] S2: The melamine solution was poured into the cyanuric acid solution, stirred for 3 h for co-precipitation reaction, and then solid-liquid separation was performed after stirring was completed, washed with deionized water and ethanol alternately for 3 times each, and dried at 60°C with air blowing for 8 h, to obtain a supramolecular solid;

[0119] S3: The supramolecular solid obtained in step S2 was heated to 550°C at a heating rate of 5°C / min under the protection of high-purity argon gas (purity of 99.99%) and kept for 4 h, and then cooled to room temperature, to obtain graphite phase carbon nitride, recorded as CN.

[0120] The schematic diagram of the distance between iron atoms in the catalysts prepared in example 7, example 11 and comparative example 1 is shown in Figure 1 By precise coordination between iron ions and organic ligands, the distance between adjacent Fe atoms was controllably designed, and the supramolecule was formed by encapsulation through hydrogen bonds between melamine and cyanuric acid, and then the iron monatomic catalyst (Fe1 / CN, comparative example 1), the catalyst with iron loading regulating the distance between iron atoms (Fe1-Fe1 / CN, example 11) and the catalyst with bridging sulfur regulating the distance between iron atoms (Fe1-S-Fe1 / CN, example 7) were synthesized by high-temperature pyrolysis under argon atmosphere.

[0121] Figure 2 The spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy image and the Fe, S element distribution spectrum of the catalyst with bridging sulfur regulating the distance between iron atoms (Fe1-S-Fe1 / CN) prepared in example 7 are shown in Figure 3 The spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy image and the Fe, S element distribution spectrum of the catalyst with iron loading regulating the distance between iron atoms (Fe1-Fe1 / CN) prepared in example 11 are shown in Figure 4The spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy images and the element distribution maps of Fe and S of the iron monatomic catalyst (Fe1 / CN) prepared in Comparative Example 1 were obtained. It was observed from Figure 2 , Figure 3 and Figure 4 that Fe1 / CN, Fe1-Fe1 / CN and Fe1-S-Fe1 / CN all had a sheet structure, but the state and distance of the iron atoms in each catalyst were completely different (as indicated by the circles). Among them, Figure 2 Fe1 / CN in Comparative Example 1 showed that a single iron atom uniformly existed in the CN, and only the uniform existence of the iron element could be observed in the element distribution map; Figure 3 Fe1-Fe1 / CN in Comparative Example 2 showed a state of multiple iron atoms in partial aggregation, which was consistent with the aggregation state of the iron element and the absence of sulfur element in the element distribution map; Figure 4 Fe1-S-Fe1 / CN in Comparative Example 3 had a distance between the adjacent two iron atoms, i.e., an iron atom pair, and the elements of Fe and S were distributed in the same region. The above experimental results showed that the distance between the adjacent iron atoms in Fe1 / CN, Fe1-Fe1 / CN and Fe1-S-Fe1 / CN was different, which corresponded to the results of Figure 1 . According to the statistics of the distance between the iron atoms in each catalyst and the analysis of the Rayleigh model fitting (see Figure 5 ), the distance between the iron atoms in Fe1 / CN, Fe1-Fe1 / CN and Fe1-S-Fe1 / CN was 0.42 nm, 0.35 nm and 0.28 nm, respectively, indicating that the bridging sulfur atom existed in the form of coordination bond Fe-S-Fe, which shortened the distance between the two iron atoms.

[0122] In order to verify the existence of the bridging sulfur configuration, the crystal faces of the support CN in each catalyst were analyzed by X-ray diffractometer. Figure 6 The X-ray diffraction patterns of the bridging sulfur-regulated iron atom distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7, the iron loading-regulated iron atom distance catalyst (Fe1-Fe1 / CN) prepared in Example 11, the iron monatomic catalyst (Fe1 / CN) prepared in Comparative Example 1 and the graphite phase carbon nitride (CN) prepared in Comparative Example 2. From Figure 6 (a), it can be seen that Fe1 / CN, Fe1-Fe1 / CN and Fe1-S-Fe1 / CN not only had the same structure as CN, but also did not have the characteristic diffraction peaks of iron nanoparticles, indicating that the iron in each catalyst existed in the form of small-sized atoms, which was consistent with the test results of the spherical aberration-corrected electron microscopy. Figure 6(b) is a magnified detail and schematic diagram of the X-ray diffraction pattern of the catalysts prepared in Examples 7, 11 and Comparative Example 1 and the graphitic carbon nitride prepared in Comparative Example 2 at the 100 crystal plane. Figure 6 (c) is a magnified detail and schematic diagram of the X-ray diffraction patterns of the catalysts prepared in Examples 7, 11, and Comparative Example 1, and the graphitic carbon nitride prepared in Comparative Example 2 at the 002 crystal plane. Compared to the (12.8°, 100) and (27.8°, 002) characteristic peaks of CN, the characteristic peaks corresponding to the (100) and (002) crystal planes of Fe1 / CN, Fe1-Fe1 / CN, and Fe1-S-Fe1 / CN are all shifted to smaller angles. This indicates that as the interatomic spacing of iron atoms shortens, the interaction force between iron atoms in the (100) crystal plane and C and N atoms in the heptaazine ring increases, causing a certain surface stress, which in turn shortens the distance between the inner layers of the CN support corresponding to the (002) crystal plane. The above results confirm that the surface stress of Fe1-Fe1 / CN and Fe1 / CN is more pronounced (see...). Figure 6 (b) Furthermore, the bridging sulfur atoms exist in the interlayer of CN, rather than coordinating with Fe atoms within the layers, thus regulating the surface stress between the support CN and each Fe atom. The catalysts prepared in Examples 1-11 were tested using inductively coupled plasma atomic emission spectrometry (ICP-AES), resulting in a comparison chart of iron loading in the catalysts prepared in Examples 1-11, as shown below. Figure 7 As shown. The iron loading in Fe1-S-Fe1 / CN prepared in Examples 1-8 was approximately 8.0 wt.%, the iron loading in Fe1-Fe1 / CN prepared in Example 9 was approximately 3.1 wt.%, the iron loading in Fe1-Fe1 / CN prepared in Example 10 was approximately 2.2 wt.%, and the iron loading in Fe1-Fe1 / CN prepared in Example 11 was approximately 1.5 wt.%. This further demonstrates that the establishment of the bridging sulfur configuration effectively increases the iron loading in each catalyst.

[0123] The coordination configurations of iron atoms in the catalysts prepared in Examples 7, 11, and Comparative Example 1 were studied using extended X-ray absorption fine analysis. Standard samples such as FeS, Fe3N, and iron foil were also investigated. Figure 8The X-ray diffraction patterns of Fe1-S-Fe1 / CN, Fe1-Fe1 / CN, Fe1 / CN and CN are shown in FIG. 6. The characteristic peak of Fe1-S-Fe1 / CN at 1.4 Å is obviously corresponding to the iron-nitrogen coordination scattering, and the dominant peak of Fe1-S-Fe1 / CN shifts to 1.6 Å, which corresponds to the iron-sulfur coordination bond of FeS standard sample, indicating the internal coordination configuration of iron-sulfur. In addition, Fe1-Fe1 / CN presents obvious characteristic peaks at 1.4 Å and 2.6 Å, indicating that there are two coordination environments of iron atoms in the internal, which are iron-nitrogen and iron-iron coordination bonds. These results show that when the distance between two iron atoms is close, iron clusters are prone to occur due to high surface energy, but the bridging sulfur atom can increase the iron atom loading while avoiding the occurrence of iron clusters.

[0124] The binding energies of elements in the catalyst with bridging sulfur regulating the distance between iron atoms (Fe1-S-Fe1 / CN) prepared in Example 7, the catalyst with iron atom loading regulating the distance between iron atoms (Fe1-Fe1 / CN) prepared in Example 11, the single iron atom catalyst (Fe1 / CN) prepared in Comparative Example 1 and the graphite phase carbon nitride (CN) prepared in Comparative Example 2 were studied by X-ray photoelectron spectroscopy, as shown in FIG. 5, wherein, Figure 9 Figure 9 (a) is the S 2p spectrum of the catalyst prepared in Example 7, Example 11 and Comparative Example 1 and the CN prepared in Comparative Example 2; Figure 9 (b) is the Fe 2p spectrum of the catalyst prepared in Example 7, Example 11 and Comparative Example 1 and the CN prepared in Comparative Example 2; Figure 9 (c) is the C 1s spectrum of the catalyst prepared in Example 7, Example 11 and Comparative Example 1 and the CN prepared in Comparative Example 2; Figure 9 (d) is the N 1s spectrum of the catalyst prepared in Example 7, Example 11 and Comparative Example 1 and the CN prepared in Comparative Example 2. The S 2p spectrum of Fe1-S-Fe1 / CN (a) is observed to have an obvious characteristic peak at 162.3 eV, which is attributed to Fe-S coordination, but there is no characteristic peak of C-S-C and C-SO Figure 9 X The characteristic peak of Fe-S coordination is observed at 162.3 eV, but there is no characteristic peak of C-S-C and C-SO X , indicating that the sulfur atom is not located in the internal of the carrier CN, but is combined with two iron atoms, which is consistent with the result of X-ray diffraction pattern. Due to the low electronegativity characteristics of sulfur atom than nitrogen atom and carbon atom, the existence of bridging sulfur (Fe-S-Fe) microstructure is found, which effectively reduces the electron density of iron atom. From Figure 9 (b), it can be seen that the ratio of Fe 2+ / Fe 3+ increases from 1.00 to 1.12, which is consistent with the increase of the ratio of Fe 2+ / Fe 3+The ratio of the two is similar. From Figure 9 (c) and Figure 9 As can be seen from (c) and (d), the sp 2 hybridized nitrogen atom (N-C=N) and the sp 2 hybridized carbon atom (C-N=C) characteristic peaks in the C 1s and N 1s spectra are both shifted to the high-energy direction, which also confirms that the iron atoms are coordinated with sulfur atoms, carbon atoms, and nitrogen atoms.

[0125] Figure 10 Fe K-edge X-ray absorption near-edge structure spectra of the bridged sulfur-regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7, the iron loading-regulated iron atomic distance catalyst (Fe1-Fe1 / CN) prepared in Example 11, the iron single-atom catalyst (Fe1 / CN) prepared in Comparative Example 1, FeO, Fe2O3, and Fe3O4. Further analysis from the extended X-ray absorption near-edge structure spectra shows that the absorption edge and transition energy of Fe1 / CN, Fe1-Fe1 / CN, and Fe1-S-Fe1 / CN are all between the FeO and Fe2O3 references. Among them, Fe1-S-Fe1 / CN and Fe1 / CN are similar to FeO, and Fe1-Fe1 / CN is similar to Fe2O3, confirming that the valence state of the iron atoms in Fe1-S-Fe1 / CN is lower than that of the iron atoms in Fe1-Fe1 / CN, which is consistent with the results of the X-ray photoelectron Fe 2p spectrum.

[0126] By means of density functional theory, the comparative diagram of the d-orbital state density of the iron atoms in the bridged sulfur-regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7 and the iron loading-regulated iron atomic distance catalyst (Fe1-Fe1 / CN) prepared in Example 11 is analyzed, as shown in Figure 11 which confirms that the bridged sulfur atom can regulate the d-band center of the iron atom to be closer to the Fermi energy level, thereby increasing the number of unoccupied electrons on the d-orbital, which utilizes the interaction between the two iron atoms and the oxygen atoms in the PMS. The above results further prove that the bridged sulfur atom can weaken the electron density of the iron atom.

[0127] Application Example 1

[0128] A saturated aqueous solution of 4-CP was added to a 80 mL beaker containing 50 mL of deionized water to make the initial concentration of 4-CP solution 0.1 mmol / L. 25 mg of the bridged sulfur-regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7, 25 mg of the iron loading-regulated iron atomic distance catalyst (Fe1-Fe1 / CN) prepared in Example 11 and 25 mg of the iron single-atom catalyst (Fe1 / CN) prepared in Comparative Example 1 were weighed out respectively and added to the 0.1 mmol / L 4-CP solution respectively, and after ultrasonic dispersion, they were placed on a magnetic stirrer to keep continuous stirring. After the adsorption reaction between the solid and liquid reached equilibrium, a saturated PMS solution was added to make the initial concentration of PMS 0.5 mmol / L. In addition, when the saturated PMS solution was added, the timing was started, and a clean syringe was used to take samples at 0, 0.5, 1, 1.5, 2, 2.5, 3, 5 and 10 min respectively, and after solid-liquid separation treatment with a 0.22 micron filter membrane, they were placed in amperometric bottles containing 10% methanol solution by volume. The concentrations of 4-CP and PMS in the solution were determined by high performance liquid chromatography and ultraviolet spectrophotometry respectively.

[0129] The concentration change curve of 4-CP in the process of activating PMS to degrade 4-CP by the catalysts prepared in Example 7, Example 11 and Comparative Example 1 is shown in Figure 12 (a). According to the degradation curves in Figure 12 (a), the first-order kinetics was fitted and normalized with the iron atomic loading, and the degradation rate of Fe1-S-Fe1 / CN was 2.93*10 4 min -1 mol -1 , which was 5.2 times and 12.2 times of Fe1 / CN (0.57*10 4 min -1 mol -1 ) and Fe1-Fe1 / CN (0.21*10 4 min -1 mol -1 ) respectively (see Figure 12 (b)). It is shown that the introduction of bridged sulfur atoms significantly improves the degradation rate of 4-CP in the solution.

[0130] Application Example 2

[0131] A saturated aqueous solution of 4-CP was added to several 80 mL beakers containing 50 mL of deionized water to give an initial concentration of 0.1 mmol / L of 4-CP. Each type of quencher was weighed and added to the respective 4-CP solution to give a concentration of 500 mmol / L for methanol and tert-butanol, 5 mmol / L for nitroblue tetrazolium, 5 mmol / L for methyl phenyl sulfoxide, and 5 mmol / L for sodium azide. 25 mg of catalyst prepared from Example 7, Example 11, and Comparative Example 1, respectively, was added to the 0.1 mmol / L 4-CP solution containing the respective concentrations of each type of quencher, and was ultrasonically dispersed before being placed on a magnetic stirrer to maintain constant stirring. After the adsorption reaction between the solid and liquid reached equilibrium, a saturated solution of PMS was added to give an initial concentration of 0.5 mmol / L of PMS. In addition, when the saturated solution of PMS was added, the timing was started, and a clean syringe was used to take samples at 0, 0.5, 1, 1.5, 2, 2.5, 3, 5, and 10 minutes, and the solid-liquid separation was performed using a 0.22 micron filter before being placed in an amperometric bottle containing a 10% methanol solution by volume. The concentration of 4-CP in the solution was determined using a high performance liquid chromatograph. As shown in Figure 13 Figure 2, compared to the control group without any quencher, the addition of methanol, tert-butanol, nitroblue tetrazolium, and sodium azide to the Fe1-S-Fe1 / CN / PMS / 4-CP reaction system was observed to slightly inhibit the degradation of 4-CP, but the addition of methyl phenyl sulfoxide significantly inhibited the degradation of 4-CP. Under the same experimental conditions, it was found that the addition of sodium azide to the Fe1 / CN / PMS / 4-CP and Fe1-Fe1 / CN / PMS / 4-CP reaction systems significantly inhibited the degradation of 4-CP. In contrast, methanol, tert-butanol, nitroblue tetrazolium, and methyl phenyl sulfoxide did not affect the degradation of 4-CP in the Fe1 / CN / PMS / 4-CP system, and methanol and methyl phenyl sulfoxide partially inhibited the degradation of 4-CP in the Fe1-Fe1 / CN / PMS / 4-CP system. The above results show that Fe1-S-Fe1 / CN-activated PMS mainly produces Fe VI =O and 1 O2, with contribution rates of 88.3% and 11.7%, respectively; Fe1 / CN-activated PMS only produces 1 O2, with a contribution rate of 100%; and Fe1-Fe1 / CN-activated PMS mainly produces 1 O2 and free radicals, with contribution rates of 88.7% and 11.3%, respectively (see Figure 12 (b). The change in PMS concentration over time in each reaction system was also detected, as shown in Figure 14(a) As shown, Fe1-S-Fe1 / CN consumes PMS in solution faster than Fe1 / CN and Fe1-Fe1 / CN. Combined with the component analysis of the content of each active species generated, it is found that the utilization rate of PMS by Fe1-S-Fe1 / CN reaches 69%, which is 5.8 times that of Fe1 / CN (12%) and 6.9 times that of Fe1-Fe1 / CN (10%) (see Figure 14 (b)). It shows that Fe1-S-Fe1 / CN in the bridging sulfur configuration can produce Fe IV =O with high selectivity while significantly improving the utilization rate of PMS.

[0132] In order to reveal the influence of the sulfur / iron molar ratio on the Fe1-S-Fe1 / CN activated PMS to generate Fe IV =O and its degradation rate of 4-CP, the degradation rate of 4-CP by PMS activated by the bridging sulfur regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Examples 1-8, the Fe IV =O / 1 O2 and the sulfur / iron molar ratio are shown in the correlation diagram as Figure 15 shown. With the increase of the sulfur / iron molar ratio, the efficiency of its activation of PMS to generate Fe IV =O and degrade 4-CP is significantly improved. Among them, the degradation rate and the sulfur / iron molar ratio in Fe1-S-Fe1 / CN present a certain positive linear correlation; while the Fe IV =O / 1 O2 and the sulfur / iron molar ratio in Fe1-S-Fe1 / CN exist a gradually accelerated relationship, the reason is that the amount of Fe IV =O and 1 O2 two non-radical active species generated is “this consumes the other grows”, with the increase of the content of bridging sulfur, Fe IV =O gradually increases while 1 O2 gradually decreases.

[0133] In order to confirm the influence mechanism of bridging sulfur on the high selectivity of Fe IV =O generation, the binding reaction between each oxygen site on PMS and iron atom is carried out, and the energy barrier change diagram of each step of the process of Fe IV =O generated by PMS activated by the bridging sulfur regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7 and the iron loading regulated iron atomic distance catalyst (Fe1-Fe1 / CN) prepared in Example 11 is shown in Figure 16 It is found that the PMS molecule (HSO5 -) will occur with iron atoms, including O-O breakage and O-H dissociation processes. After comparing the reaction energy barrier values of each step, it is found that the introduction of bridging sulfur not only reduces the O-O breakage energy, but also makes the energy barrier difference between O-O breakage and O-H dissociation -0.01 eV, close to a spontaneous process. Further confirmation that bridging sulfur promotes the activation of PMS by iron monatomic catalysts to generate Fe IV =O.

[0134] Application Example 3

[0135] Phenolic benzene series such as phenol, p-chlorophenol, p-hydroxybenzoic acid, and p-nitrophenol are considered common chemicals, usually produced in large quantities by chemical plants, and their molecular structures contain both hydroxyl and hydrogen, chlorine, carboxyl, nitro, and other functional groups.

[0136] Saturated aqueous solutions of phenolic benzene series (such as phenol, p-chlorophenol, p-hydroxybenzoic acid, and p-nitrophenol) were added to several 80 mL beakers containing 50 mL of deionized water, so that the initial concentrations of phenol, p-chlorophenol, p-hydroxybenzoic acid, and p-nitrophenol were 0.1 mmol / L. 25 mg of the catalyst prepared in Example 7, Example 11, and Comparative Example 1 was weighed and added to the 0.1 mmol / L phenol, p-chlorophenol, p-hydroxybenzoic acid, or p-nitrophenol solution, and after ultrasonic dispersion, it was placed on a magnetic stirrer to maintain continuous stirring. After the adsorption reaction between the solid and liquid reached equilibrium, a saturated solution of PMS was added to make the initial concentration of PMS 0.5 mmol / L. In addition, when the saturated PMS solution was added, the timing was started, and a clean syringe was used to take samples at 0, 0.5, 1, 1.5, 2, 2.5, 3, 5, and 10 minutes, and after solid-liquid separation treatment with a 0.22 micron filter, it was placed in an amperometric bottle containing a 10% methanol solution by volume. The concentrations of each phenolic benzene series in the solution were determined by high performance liquid chromatography.

[0137] As Figure 17 shown, Fe1-S-Fe1 / CN exhibited excellent degradation rates (0.26*10 4 ~3.94*10 4 min -1 mol -1 ), indicating that Fe IV =O can attack multiple functional groups in the phenolic benzene series molecules, including hydroxyl and hydrogen, chlorine, carboxyl, nitro, etc. To explore the degradation ability of Fe IV =O on each functional group, according to Fe IV =O is a non-radical active species, which degrades organic pollutants by electron transfer. Therefore, we use the isopotential value to simulate an indicator representing the electron density of each phenolic benzene series.Figure 18 The correlation between the degradation rate of PMS activated by the bridged sulfur-regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7 and the isoelectric potential of different phenolic benzene series was plotted, and it was found that there was a good linear positive correlation between the degradation ability of Fe1-S-Fe1 / CN and the functional groups such as chloro, carboxyl, nitro, etc. Among them, as the isoelectric potential increased, the degradation rate decreased linearly; while Fe IV =O showed better degradation efficiency for the hydrogen group, which was mainly due to the fact that the lowest unoccupied orbital of phenol was usually lower than that of Fe IV =O and 1 O2, and the degradation process was caused by the synergistic effect between Fe IV =O and 1 O2. The above results showed that the degradation efficiency of PMS activated by Fe1-S-Fe1 / CN for phenolic benzene series had a certain universality.

[0138] Application Example 4

[0139] A saturated aqueous solution of 4-CP was added to several 80 mL beakers containing 50 mL of surface water (from 30°18'1''N, 120°5'13''E) to make the initial concentration of 4-CP 0.1 mmol / L. 25 mg of the bridged sulfur-regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7 was weighed into 0.1 mmol / L of 4-CP solution and ultrasonically dispersed, then placed on a magnetic stirrer to keep continuous stirring. After the adsorption reaction between the solid and the liquid reached equilibrium, a saturated solution of PMS was added to make the initial concentration of PMS 0.5 mmol / L. In addition, when the saturated solution of PMS was added, the timing started, and a clean syringe was used to take samples at 0, 0.5, 1, 1.5, 2, 2.5, 3, 5 and 10 minutes, and then the solid-liquid separation was treated with a 0.22 micron filter membrane and placed in an amperometric bottle containing a 10% methanol solution. At the same time, the catalyst solids were collected for the next reaction, and the cycle was repeated for a total of 5 times. The concentration of 4-CP in the solution at each reaction time in each cycle was determined by high performance liquid chromatography.

[0140] In order to verify the stability of the bridged sulfur-regulated iron atomic distance catalyst (Fe1-S-Fe1 / CN) prepared in Example 7, a periodic experiment was carried out, and the experimental results are shown in Figure 19 From Figure 19 (a), it can be found that the stability of Fe1-S-Fe1 / CN is good; from Figure 19The iron ion leaching rate of Fe1-S-Fe1 / CN in (b) is lower than 5% of the iron loading in the catalyst. Therefore, the catalyst has good reusability in chlorophenol wastewater treatment applications, effectively reducing operating costs.

[0141] The above description is merely preferred embodiments of the present application, but not to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the scope of protection of the present application.

Claims

1. An iron catalyst with controllable interatomic distances, characterized in that, The iron atom distance controllable catalyst is synthesized by the following steps: S1: dissolving melamine in deionized water at 70-90 DEG C to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90 DEG C to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30 DEG C to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid and ferrous sulfate is 1:0.5-0.9:0.5-0.2; S2: pouring thioacetamide into the ferrous sulfate solution obtained in step S1, uniformly stirring at 20-30 DEG C for 5-10 min to obtain solution a; the molar ratio of thioacetamide and ferrous sulfate is 1:0.2-0.8; S3: pouring solution a obtained in step S2 into the cyanuric acid solution obtained in step S1, uniformly stirring at 70-90 DEG C for 5-10 min, then pouring the mixed solution into the melamine solution obtained in step S1, stirring for 2-4 h for co-precipitation reaction, then performing solid-liquid separation and washing, and blowing dry at 55-60 DEG C for 6-8 h to obtain a supramolecular solid; S4: under the protection of argon atmosphere, heating the supramolecular solid obtained in step S3 to 550-650 DEG C, keeping warm for 3-5 h, and then cooling to room temperature to obtain an iron atom distance controllable catalyst, denoted as Fe1-S-Fe1 / CN; Through precise coordination between iron ions and thioacetamide, the distance between adjacent Fe atoms can be controllably designed.

2. Use of the catalyst with controllable iron interatomic distance according to claim 1 for removal of phenolic benzenoids from surface water bodies, characterized by that, The method comprises the following steps: pouring the iron atom distance controllable catalyst and persulfate into a surface water body, the water body temperature is 20-30 DEG C, and stirring reaction is performed for 10-15 min to complete the removal of phenolic benzene series in the surface water body; the dosing amount of the iron atom distance controllable catalyst is 0.2-0.6 g / L; the dosing amount of the persulfate is 100-600 μmol / L; and the concentration of the phenolic benzene series is 0-200 μmol / L.

3. Use according to claim 2, characterized in that, The phenolic benzene series is phenol, p-chlorophenol, p-hydroxybenzoic acid or p-nitrophenol. The iron atom distance controllable catalyst is synthesized by the following steps: S1: dissolving melamine in deionized water at 70-90 DEG C to obtain a melamine solution; dissolving cyanuric acid in deionized water at 70-90 DEG C to obtain a cyanuric acid solution; dissolving ferrous sulfate heptahydrate in deionized water at 20-30 DEG C to obtain a ferrous sulfate solution; the molar ratio of melamine, cyanuric acid and ferrous sulfate is 1:0.5-0.9:0.5-0.2; S2: pouring thioacetamide into the ferrous sulfate solution obtained in step S1, uniformly stirring at 20-30 DEG C for 5-10 min to obtain solution a; the molar ratio of thioacetamide and ferrous sulfate is 1:0.2-0.8; S3: pouring solution a obtained in step S2 into the cyanuric acid solution obtained in step S1, uniformly stirring at 70-90 DEG C for 5-10 min, then pouring the mixed solution into the melamine solution obtained in step S1, stirring for 2-4 h for co-precipitation reaction, then performing solid-liquid separation and washing, and blowing dry at 55-60 DEG C for 6-8 h to obtain a supramolecular solid; S4: under the protection of argon atmosphere, heating the supramolecular solid obtained in step S3 to 550-650 DEG C, keeping warm for 3-5 h, and then cooling to room temperature to obtain an iron atom distance controllable catalyst, denoted as Fe1-S-Fe1 / CN; Through precise coordination between iron ions and thioacetamide, the distance between adjacent Fe atoms can be controllably designed. The method comprises the following steps: pouring the iron atom distance controllable catalyst and persulfate into a surface water body, the water body temperature is 20-30 DEG C, and stirring reaction is performed for 10-15 min to complete the removal of phenolic benzene series in the surface water body; the dosing amount of the iron atom distance controllable catalyst is 0.2-0.6 g / L; the dosing amount of the persulfate is 100-600 μmol / L; and the concentration of the phenolic benzene series is 0-200 μmol / L. The phenolic benzene series is phenol, p-chlorophenol, p-hydroxybenzoic acid or p-nitrophenol.

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