A rare earth metal oxide cluster carbon-based material and its preparation method and singlet oxygen catalyst

Abstract

The present invention provides a rare earth metal oxide cluster carbon-based material, a preparation method thereof, and a singlet oxygen catalyst. The method comprises the following steps: (1) mixing a rare earth nitrate, a citric acid compound, and a first solvent to obtain a precursor; and (2) mixing and calcining the precursor obtained in step (1), a phenolic compound, an aldehyde compound, and a second solvent to obtain the rare earth metal oxide cluster carbon-based material. The preparation method of the rare earth metal oxide cluster carbon-based material provided by the present invention is simple to operate and low in cost, and the prepared carbon-based material can efficiently produce singlet oxygen under conditions without light, energy input, or chemical oxidants, and can therefore be widely used in the field of organic pollutant wastewater treatment and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst materials, and in particular relates to a rare earth metal oxide cluster carbon-based material, a preparation method thereof, and a singlet oxygen catalyst. Background Art

[0002] Singlet oxygen (1O2) is the excited state of triplet oxygen (3O2) and was discovered by H. Kautsky in 1938. It has 1Σg depending on the proportion of electrons in the π molecular orbital. + and 1Δg. Since 1Σg + The lifetime is less than 1ns, so 1O2 is usually considered to be 1Δg. The energy of 1O2 is about 0.95eV higher than that of 3O2, but its reaction activity is weaker and its oxidation potential is lower than that of ·SO4- and ·OH (E0(1O2 / ·O2 - )=0.81VNHE,E0(·SO4 - / SO4 2- )=2.60-3.10VNHE,E0(·OH / OH - )=1.90-2.70VNHE). In addition, with SO4 - Compared with free radicals such as ·OH, 1O2 has higher selectivity and wider pH tolerance for electron-rich organic pollutants, and is not easily quenched by ions in water. More importantly, the half-life of 1O2 (t1 / 2 = 4μs) is much longer than that of ·OH (t1 / 2 < 1μs), which allows for higher transient concentrations. 1O2 has been reported to be used in photodynamic therapy (PDT), chemodynamic therapy (CDT), the production of high-value-added chemicals, and the effective removal of organic pollutants. Therefore, 1O2 has broad application prospects in biomedicine, chemistry, and the environment.

[0003] Currently, there are three important methods for producing 1O2: photosensitivity / photocatalysis, electrocatalysis, and oxidation / enzymatic reactions. While these methods can produce 1O2, they have significant limitations. Sunlight penetration into solution is limited, and generating ultraviolet light requires significant energy consumption; electrocatalysis also requires high-intensity energy input; enzymatic reactions require strict temperature and pH conditions, and oxidation reactions require highly oxidizing chemicals, posing safety and secondary pollution risks.

[0004] CN108380195A discloses a preparation method and application of a molecular oxygen activation catalyst constructed based on surface oxygen defects. A series of C@MOx materials with controllable surface oxygen defect content are constructed (M is Ti, Mn or Si element, and the value of x is determined by the oxidation state of the M element). They can activate dissolved oxygen in water to produce reactive oxygen species: superoxide radicals (·O2-) and singlet oxygen (1O2), and quickly and effectively remove and degrade organic pollutants. CN115106079A discloses a catalyst that can promote the generation of singlet oxygen, its preparation method and application. The catalyst uses a modified honeycomb ceramic as a carrier and an oxygen-vacancy-containing manganese tetraoxide with an oxygen vacancy content of no more than 0.5wt% dispersed in the carrier as an active component. Manganese tetraoxide is rich in oxygen vacancies. When used in the deep treatment process of industrial wastewater, it can enhance the oxidant effect, increase the yield of singlet oxygen active groups, and achieve deep mineralization of organic pollutants.

[0005] Although the materials disclosed in the above patents can generate singlet oxygen to degrade organic pollutants, they have problems such as complex preparation process, high cost and low efficiency in generating singlet oxygen.

[0006] Therefore, there is an urgent need to provide a catalyst material that can efficiently produce singlet oxygen in the absence of light, energy input, and chemical oxidants, and has low cost and simple preparation process, which is of extremely important practical significance. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a rare earth metal oxide cluster carbon-based material, a preparation method thereof, and a singlet oxygen catalyst. The preparation method of the rare earth metal oxide cluster carbon-based material provided by the present invention is simple to operate and low in cost, and the prepared carbon-based material can reach 2 mmol under conditions without light, energy input, and chemical oxidants. 1 The singlet oxygen production efficiency of rare earth metals is 0.02 / mol, which can be widely used in the field of organic pollutant wastewater treatment and has broad application prospects.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a rare earth metal oxide cluster carbon-based material, the method comprising the following steps:

[0010] (1) mixing a rare earth nitrate, a citric acid compound, and a first solvent to obtain a precursor;

[0011] (2) Mixing and calcining the precursor, phenolic compound, aldehyde compound and second solvent obtained in step (1) to obtain the rare earth metal oxide cluster carbon-based material.

[0012] The present invention prepares a carbon-based material having rare earth metal oxide clusters by mixing rare earth nitrates with citric acid compounds to form a complex, thereby preventing the generation of rare earth precipitates and obtaining a precursor with uniformly distributed rare earth ions. The complex is then mixed with phenolic compounds and aldehyde compounds to obtain a resin matrix loaded with rare earth metal clusters. The resin matrix is ​​converted into a carbon substrate by calcining, thereby preparing a carbon-based material having rare earth metal oxide clusters. The carbon-based material contains active sites of rare earth oxide clusters and has a strong ability to generate singlet oxygen. In addition, the carbon-based material can generate singlet oxygen by absorbing and activating oxygen molecules in the absence of light, energy input, and chemical oxidants, thereby effectively degrading pollutants in water.

[0013] Preferably, the rare earth nitrate in step (1) includes any one or a combination of at least two of scandium nitrate, yttrium nitrate, lanthanum nitrate, cerium nitrate, praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, terbium nitrate, dysprosium nitrate, holmium nitrate, erbium nitrate, thulium nitrate, ytterbium nitrate or lutetium nitrate, preferably gadolinium nitrate.

[0014] In the present invention, gadolinium nitrate is selected because it has the advantages of being easily soluble and not introducing impurity elements, and the adsorption energy of gadolinium oxide clusters on oxygen molecules is moderate, which is conducive to the generation of singlet oxygen.

[0015] In the present invention, nitrates are not only easily soluble, but also have nitrogen that escapes as gas during calcination and does not remain in the material. If chlorides or phosphates are used, chlorine and phosphorus will remain during subsequent calcination.

[0016] Preferably, the citric acid compound in step (1) comprises any one of citric acid, potassium citrate or ammonium citrate, or a combination of at least two thereof, preferably citric acid.

[0017] In the present invention, citric acid is selected because it has the advantage of easily forming a stable and uniform complex with rare earth ions.

[0018] Preferably, the mass ratio of the rare earth nitrate and the citric acid compound in step (1) is (2-20):1, preferably (2-10):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, etc.

[0019] In the present invention, by adjusting the mass ratio of rare earth nitrate and citric acid compound, a stable and uniform rare earth metal organic complex is formed. If the mass ratio is too low, the citric acid compound will be wasted, and vice versa, the rare earth metal coordination will be incomplete, and uniform oxide clusters cannot be formed subsequently.

[0020] Preferably, in step (1), the first solvent comprises water.

[0021] Preferably, the mass ratio of the total mass of the rare earth nitrate and the citric acid compound to the first solvent in step (1) is 1:(10-100), for example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95, 1:100, etc.

[0022] In the present invention, the mass ratio of the total mass of the rare earth nitrate and the citric acid compound to the mass ratio of the first solvent is adjusted so that the reactants are at an appropriate reaction concentration. If the mass ratio is too low, the reaction rate will be reduced, resulting in a long reaction time. Conversely, if the concentration is too high, the reaction will be uneven.

[0023] Preferably, the mixing speed in step (1) is 200-1000 rpm, for example, it can be 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, etc.; the time is 6-24 h, for example, it can be 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc.

[0024] Preferably, the mixing in step (1) further includes a drying process.

[0025] Preferably, the drying temperature is 60-80°C, for example, 60°C, 65°C, 70°C, 75°C or 80°C.

[0026] Preferably, the drying time is 12-48 hours, for example, it can be 12 hours, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours or 48 hours.

[0027] Preferably, the phenolic compound in step (2) includes any one or a combination of at least two of phenol, catechol, hydroquinone or resorcinol, preferably phenol.

[0028] Preferably, the mass ratio of the phenolic compound to the precursor in step (2) is 1:(1-5), for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, etc.

[0029] In the present invention, by adjusting the mass ratio of the phenolic compound to the precursor, the rare earth metal is kept at a relatively appropriate loading amount on the substrate. If the mass ratio is too low, the substrate will be too small, resulting in uneven agglomeration of the loaded rare earth metal. Conversely, if the mass ratio is too high, the rare earth metal loading will be too dispersed, reducing the singlet oxygen concentration per unit mass of material.

[0030] Preferably, the aldehyde compound in step (2) includes formaldehyde.

[0031] Preferably, in step (2), the second solvent comprises ethanol and water.

[0032] Preferably, the mass ratio of the total mass of the phenolic compound and the precursor to the second solvent in step (2) is 1:(10-100), for example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95, 1:100, etc.

[0033] In the present invention, the mass ratio of the total mass of the phenolic compound and the precursor to the mass ratio of the second solvent is adjusted to ensure that the reaction substances are at an appropriate reaction concentration. If the mass ratio is too low, the reaction rate will be reduced, resulting in a long reaction time. Conversely, if the concentration is too high, the reaction will be uneven.

[0034] Preferably, the mixing in step (2) further includes a drying process.

[0035] Preferably, the calcination in step (2) is carried out under a protective atmosphere.

[0036] Preferably, the protective atmosphere comprises any one of nitrogen, carbon dioxide or an inert gas or a combination of at least two thereof, preferably argon.

[0037] Preferably, the heating rate of the calcination in step (2) is 5-15°C / min, for example, it can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min, etc.

[0038] Preferably, the calcination temperature in step (2) is 600-800°C, for example, it can be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, etc.

[0039] In the present invention, the calcination temperature is controlled to make the rare earth oxide clusters of moderate size. If the temperature is too low, the clusters will aggregate and grow, and the catalytic activity cannot be fully exerted. Otherwise, the cluster structure will be destroyed, resulting in material failure.

[0040] Preferably, the holding time during the calcination in step (2) is 1-8 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc.

[0041] Preferably, the calcination in step (2) further includes washing with alkaline solution.

[0042] Preferably, the alkali solution comprises sodium hydroxide solution.

[0043] In a second aspect, the present invention provides a rare earth metal oxide cluster carbon-based material, wherein the rare earth metal oxide cluster carbon-based material is prepared by the method for preparing a rare earth metal oxide cluster carbon-based material according to the first aspect.

[0044] In a third aspect, the present invention provides a singlet oxygen catalyst, which comprises the rare earth metal oxide cluster carbon-based material according to the second aspect.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention provides a method for preparing a carbon-based material with rare earth metal oxide clusters. The method comprises the steps of mixing rare earth nitrates with citric acid compounds to obtain a precursor, mixing the precursor with phenolic compounds and aldehyde compounds, and calcining the precursor to obtain a carbon-based material with rare earth metal oxide clusters. The carbon-based material contains rare earth oxide cluster active sites and has a strong ability to generate singlet oxygen. The carbon-based material can also generate singlet oxygen by absorbing and activating oxygen molecules in the absence of light, energy input, and chemical oxidants, thereby effectively degrading pollutants in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is an AC-TEM image of the rare earth metal oxide cluster carbon-based material provided in Example 1;

[0048] Figure 2 This is a singlet oxygen EPR signal detection diagram of the rare earth metal oxide cluster carbon-based material provided in Examples 1, 4 and 5 and Comparative Example 1;

[0049] Figure 3 Singlet oxygen concentration graph of the rare earth metal oxide cluster carbon-based material provided for Examples 1, 4 and 5 and Comparative Example 1;

[0050] Figure 4This is a diagram showing the effect of using the rare earth metal oxide cluster carbon-based material provided in Example 1 to degrade antibiotics. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below with reference to the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that the embodiments are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] Example 1

[0053] This embodiment provides a rare earth metal oxide cluster carbon-based material and a preparation method thereof, which comprises the following steps:

[0054] (1) 2 mmol of Gd(NO3)3·6H2O (model 10294-41-4, purchased from Shanghai MacLean Biochemical Technology Co., Ltd., purity 99.9%), 100 mg of sodium citrate, and 100 mL of distilled water were stirred at 500 rpm at 25°C for 8 h, and then dried at 60°C for 12 h to obtain the precursor;

[0055] (2) 500 mg of the precursor obtained in step (1), 500 mg of resorcinol, and 0.7 mL of formaldehyde were mixed, and a mixed solvent of 80 mL of anhydrous ethanol and 20 mL of distilled water was added. The mixture was stirred at 500 rpm at 25 ° C for 24 h, and then dried at 60 ° C for 12 h. Under argon, the temperature was increased at a rate of 10 ° C / min, and the mixture was kept warm and calcined at 700 ° C for 2 h. After washing with a sodium hydroxide solution with a concentration of 4 mol / L, the rare earth metal oxide cluster carbon-based material was obtained.

[0056] from Figure 1 It can be seen that Figure 1 The white coil in the middle is a rare earth gadolinium metal oxide cluster.

[0057] Example 2

[0058] The difference between this embodiment and embodiment 1 is that the calcination temperature in step (2) is 600° C., and the rest is the same as embodiment 1.

[0059] Example 3

[0060] The difference between this embodiment and embodiment 1 is that the calcination temperature in step (2) is 800° C., and the rest is the same as embodiment 1.

[0061] Example 4

[0062] The difference between this embodiment and embodiment 1 is that Gd(NO3)3·6H2O in step (1) is replaced by Sm(NO3)3·6H2O, and the rest is the same as embodiment 1.

[0063] Example 5

[0064] The difference between this embodiment and embodiment 1 is that Gd(NO3)3·6H2O in step (1) is replaced by Y(NO3)3·6H2O, and the rest is the same as embodiment 1.

[0065] Example 6

[0066] The difference between this embodiment and embodiment 1 is that the mass of sodium citrate in step (1) is 200 mg, and the rest is the same as embodiment 1.

[0067] Example 7

[0068] The difference between this embodiment and embodiment 1 is that the mass ratio of Gd(NO3)3·6H2O to sodium citrate in step (1) is 1:1, and the other steps are the same as those in embodiment 1.

[0069] Example 8

[0070] The difference between this embodiment and embodiment 1 is that the mass ratio of Gd(NO3)3·6H2O to sodium citrate in step (1) is 25:1, and the other steps are the same as those in embodiment 1.

[0071] Example 9

[0072] The difference between this embodiment and embodiment 1 is that the mass ratio of phenol to precursor in step (2) is 1:0.5, and the rest is the same as embodiment 1.

[0073] Example 10

[0074] The difference between this embodiment and embodiment 1 is that the mass ratio of phenol to precursor in step (2) is 1:10, and the rest is the same as embodiment 1.

[0075] Example 11

[0076] The difference between this embodiment and embodiment 1 is that the mass of sodium citrate in step (1) is 800 mg, and the rest is the same as embodiment 1.

[0077] Example 12

[0078] The difference between this embodiment and embodiment 1 is that the calcination temperature in step (2) is 400° C., and the rest is the same as embodiment 1.

[0079] Comparative Example 1

[0080] This comparative example provides a method for preparing a rare earth metal oxide cluster carbon-based material, which differs from Example 1 in that Gd(NO3)3·6H2O is replaced by Fe((NO3)3·9H2O, and the material is washed with a hydrochloric acid solution after calcination to completely wash away the metallic iron element, thereby obtaining a pure carbon material free of metal elements. The other conditions are the same as those in Example 1.

[0081] Test conditions

[0082] The rare earth metal oxide cluster carbon-based materials provided in Examples 1 to 12 and Comparative Example 1 were tested using the following test methods:

[0083] (1) The obtained material was subjected to an experiment to degrade the antibiotic ofloxacin in water. Specifically, 10 mg of the material was placed in 50 mL of a 20 mg / L ofloxacin solution, stirred at 500 rpm at room temperature (25 ± 2 ° C), and samples were taken at 5 min, 10 min, 20 min, 30 min, and 60 min, respectively. The ofloxacin concentration in the reaction solution was measured using a liquid chromatograph, and the ofloxacin concentration ratio (C / C0) was calculated. The concentration ratio = (ofloxacin concentration in the solution at the measurement time / initial concentration of ofloxacin) × 100%. When the concentration of ofloxacin in the solution no longer changed, the removal rate of ofloxacin was calculated. The removal rate = 1-concentration ratio;

[0084] (2) The obtained material was placed in a water system. Under dark conditions, 2,2,6,6,6-tetramethyl-4-piperidinol (TMP) was used as a capture agent to react with singlet oxygen to generate TMPN free radicals. TMPN was detected by electron paramagnetic resonance spectrometer (EPR). The detection results are as follows: Figure 2 shown. Figure 2 The graph shows that three 1:1:1 iso-peaks are generated from left to right, indicating that the material generates singlet oxygen in a water system without light and without the addition of an oxidant. Figure 3 The singlet oxygen content of the corresponding materials was displayed, proving that the increase in singlet oxygen content enhanced the material's ability to remove ofloxacin.

[0085] The test results are shown in Table 1:

[0086] Table 1

[0087]

[0088] As can be seen from Table 1, the following conclusions are drawn:

[0089] (1) From the data of Examples 1, 4, and 5 and Comparative Example 1, it can be seen that the provided rare earth metal oxide cluster carbon-based materials can generate singlet oxygen in the absence of light, energy input, and chemical oxidants, and in the experiment of decomposing ofloxacin in water, they can play a good oxidative degradation effect on the decomposition ofloxacin. Under optimal conditions, the removal rate of ofloxacin can reach more than 95%. Taking Example 1 as an example, Figure 4 The figure shows the effect of the material described in Example 1 on the removal of ofloxacin over time. It can be seen that the removal rate of ofloxacin reaches 98.5% in 60 minutes.

[0090] (2) From the data of Examples 1, 2, 3, and 12, it can be seen that in Example 1, the calcination temperature was 700°C, and the removal rate of ofloxacin was 98.5%; in Examples 2 and 3, the calcination temperatures were 600°C and 800°C, respectively, and the removal rates were 97.4% and 97.0%, respectively. In Example 12, the calcination temperature was 400°C, and the removal rate was only 59.8%. This shows that the present invention preferably controls the calcination temperature within a specific range (600-800°C), which can generate more active sites, improve the generation efficiency of singlet oxygen, and thus improve the removal efficiency of ofloxacin. Conversely, calcination temperatures that are too high or too low will affect the formation of active sites, thereby resulting in a decrease in degradation efficiency.

[0091] (3) From the data of Examples 1, 6, 7, 8, and 11, it can be seen that when the dosage of citric acid is 100 mg, the removal rate of ofloxacin is 98.5%, when the dosage of citric acid is 200 mg, the removal rate of ofloxacin is 95.2%, and when the dosage of citric acid is 800 mg, the singlet oxygen production is very low, and the removal rate of ofloxacin is only 59.3%. This shows that the present invention preferably controls the mass ratio of citric acid to rare earth nitrate within a specific range (1:(2-10)), which can generate more active sites, improve the generation efficiency of singlet oxygen, and thus improve the removal efficiency of ofloxacin. Excessive or insufficient dosage of citric acid will affect the loading and activity of rare earth metal active sites, affect the production of singlet oxygen, and thus affect the degradation performance of the material.

[0092] Comparative Example 1 shows that replacing Gd(NO3)3·6H2O with Fe((NO3)3·9H2O cannot achieve the technical effect of the present invention.

[0093] The applicant states that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A singlet oxygen catalyst, characterized in that The singlet oxygen catalyst comprises a rare earth metal oxide cluster carbon-based material; The rare earth metal oxide cluster carbon-based material is prepared by the following method, which comprises the following steps: (1) mixing gadolinium nitrate, a citric acid compound, and a first solvent to obtain a precursor; (2) mixing and calcining the precursor, phenolic compound, aldehyde compound and second solvent obtained in step (1) to obtain the rare earth metal oxide cluster carbon-based material; The mass ratio of gadolinium nitrate to citric acid compound in step (1) is (2-20):1; The calcination in step (2) is carried out under a protective atmosphere; The mass ratio of the phenolic compound to the precursor in step (2) is 1:(1-5).

2. The singlet oxygen catalyst according to claim 1, characterized in that The citric acid compound in step (1) includes any one of citric acid, potassium citrate or ammonium citrate, or a combination of at least two of them.

3. The singlet oxygen catalyst according to claim 2, characterized in that The citric acid compound in step (1) is citric acid.

4. The singlet oxygen catalyst according to claim 1, characterized in that The mass ratio of gadolinium nitrate to citric acid compound in step (1) is (2-10):

1.

5. The singlet oxygen catalyst according to claim 1, characterized in that In step (1), the first solvent includes water.

6. The singlet oxygen catalyst according to claim 1, characterized in that The mass ratio of the total mass of the gadolinium nitrate and the citric acid compound to the first solvent in step (1) is 1:(10-100).

7. The singlet oxygen catalyst according to claim 1, characterized in that The mixing speed in step (1) is 200-1000 rpm and the mixing time is 6-24 hours.

8. The singlet oxygen catalyst according to claim 1, characterized in that The mixing in step (1) further includes a drying process.

9. The singlet oxygen catalyst according to claim 8, characterized in that The drying temperature is 60-80°C.

10. The singlet oxygen catalyst according to claim 8, characterized in that The drying time is 12-48 hours.

11. The singlet oxygen catalyst according to claim 1, characterized in that The phenolic compound in step (2) includes any one of phenol, catechol, hydroquinone or resorcinol, or a combination of at least two of them.

12. The singlet oxygen catalyst according to claim 11, characterized in that The phenolic compound in step (2) is phenol.

13. The singlet oxygen catalyst according to claim 1, characterized in that The aldehyde compound in step (2) includes formaldehyde.

14. The singlet oxygen catalyst according to claim 1, characterized in that In step (2), the second solvent includes ethanol and water.

15. The singlet oxygen catalyst according to claim 1, characterized in that The mass ratio of the total mass of the phenolic compound and the precursor to the second solvent in step (2) is 1:(10-100).

16. The singlet oxygen catalyst according to claim 1, characterized in that The mixing in step (2) further includes a drying process.

17. The singlet oxygen catalyst according to claim 1, characterized in that The protective atmosphere in step (2) includes any one of nitrogen, carbon dioxide or an inert gas or a combination of at least two of them.

18. The singlet oxygen catalyst according to claim 17, characterized in that The protective atmosphere is argon.

19. The singlet oxygen catalyst according to claim 1, characterized in that The heating rate of the calcination in step (2) is 5-15°C / min.

20. The singlet oxygen catalyst according to claim 1, characterized in that The calcination temperature in step (2) is 600-800°C.

21. The singlet oxygen catalyst according to claim 1, characterized in that The holding time during the calcination in step (2) is 1-8 hours.

22. The singlet oxygen catalyst according to claim 1, characterized in that After the calcination in step (2), the step also includes washing with alkaline solution.

23. The singlet oxygen catalyst according to claim 22, characterized in that The alkali solution includes sodium hydroxide solution.

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