A PHI / zinc oxide heterojunction photocatalyst and a low-temperature synthesis method and application thereof

Abstract

The application discloses a PHI / zinc oxide heterojunction photocatalyst and a low-temperature synthesis method and application thereof. The structure of the photocatalyst is that PHI nanosheets grow well on the surface of ZnO and are tightly wrapped with ZnO, forming a sheet-shaped core layer structure, the thickness of the PHI nanosheet is 3-5 nm, and the ZnO is a wurtzite crystal structure. The low-temperature synthesis method comprises the following steps: mixing and heating a PHI precursor and a molten salt to obtain PHI, placing the PHI and a zinc oxide precursor in an aqueous solution, adding an alkali to adjust the pH, and then reacting to obtain the photocatalyst PHI / ZnO. The photocatalyst can be used for activating molecular oxygen to oxidize the C-H bond at the benzyl position of CM to prepare cumene hydroperoxide, and can also be used for a cascade oxidation reaction to form imine and sulfoxide series compounds. The application shows the advantages of the high-activity carbon nitride-based photocatalyst in the field of organic conversion, and provides an important platform for realizing the essence safety, green and efficient oxidation reaction by the peroxide strategy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalytic oxidation, and relates to a polyheptazine imide (PHI) and zinc oxide constructed heterojunction composite material, a preparation and application thereof, specifically, the PHI and zinc oxide constructed heterojunction composite material is used as a photocatalyst to efficiently activate molecular oxygen under visible light irradiation, high-selectivity cumene hydroperoxide (CHP) is prepared, and CHP is used as a platform peroxide to form imine and sulfoxide series compounds through coupling and oxidation of benzylamine. BACKGROUND

[0002] Organic peroxides are widely used and developed due to their high activity and strong oxidizing property. Among them, cumene hydroperoxide is a typical organic hydrogen peroxide, and more than 95% of phenol in the world is prepared by taking cumene hydroperoxide as a raw material. However, a traditional large-scale cumene hydroperoxide production process directly oxidizes molecular oxygen by using a thermal method at high temperature, which is dangerous, low in efficiency (Con. < 30%), and has a high accident frequency. The preparation of cumene hydroperoxide and the cumene hydroperoxide as an oxidation platform series oxidation process are isolated from each other, which increases the danger in processing, storage and reaction processes. An intrinsically safe oxidation process, that is, converting green and widely available molecular oxygen into cumene hydroperoxide under mild conditions, and safely and efficiently realizing the cumene hydroperoxide series oxidation process has important theoretical significance and application value. So far, the reported catalytic systems cannot perfectly solve the problems of high reaction temperature and poor safety in the traditional oxidation process, and the high-selectivity cumene hydroperoxide obtained under mild conditions and the high-efficiency series oxidation reaction have not been solved.

[0003] In addition, developing an ecological friendly strategy for selective oxidation of sulfides into sulfoxides and direct coupling of benzylamines into imines is still a great challenge in the field of sustainable organic chemistry. Sulfoxides and imines not only exist widely in drug molecules, but also are key intermediates in various organic processes. In the traditional process, the synthesis strategy of imines is still to cause an oxidation reaction of aldehydes and primary amines under the action of a Lewis acid catalyst. The oxidation of sulfides is usually performed by using a strong oxidant, and the selectivity of such a reaction system is limited, and a large amount of by-products, that is, sulfones, are often obtained. Therefore, developing a method for synthesizing high-selectivity imines and sulfoxides under mild conditions has great scientific significance. SUMMARY

[0004] In order to solve the problems described in the background art, the application discloses a PHI photocatalyst platform peroxide synthesized at low temperature, a method for realizing a series oxidation reaction of the photocatalyst, and a method for efficiently activating molecular oxygen under visible light irradiation, realizing room temperature, normal pressure, and solvent-free conditions, and preparing cumene hydroperoxide by oxidizing cumene (CM). On this basis, cumene hydroperoxide is used as a platform peroxide to couple benzylamine to form imine and oxidize thioether to generate a series of sulfoxide compounds. Specifically, the technical solutions of the application are as follows:

[0005] A PHI / zinc oxide heterojunction photocatalyst, wherein PHI nanosheets grow well on the surface of ZnO and are tightly wrapped with ZnO to form a sheet-shaped core layer structure; the thickness of the PHI nanosheets is 3-5 nm; and the ZnO has a wurtzite crystal structure.

[0006] A low-temperature synthesis method of a PHI / zinc oxide heterojunction photocatalyst, comprising the following steps:

[0007] S1: PHI precursor and molten salt are uniformly mixed at a mass ratio of 1:0.1-2, heated to 330-650°C under an atmosphere, and then cooled to room temperature to obtain PHI.

[0008] S2: PHI and zinc oxide precursor are placed in an aqueous solution, an alkali is added to adjust the pH to be greater than 10, and then reacted at 120-240°C, and then cooled, washed, and dried to obtain the photocatalyst PHI / ZnO, wherein the mass ratio of PHI to zinc oxide precursor is 1:0.1-10.

[0009] For the technical solutions described above, further preferably, the PHI precursor in the S1 step is at least one of melamine, urea, dicyandiamide, ammonium thiocyanate, thiourea, or guanidine hydrochloride.

[0010] For the technical solutions described above, further preferably, the mass ratio of the PHI precursor to the molten salt in the S1 step is 1:0.3-0.5.

[0011] For the technical solutions described above, further preferably, the mass ratio of PHI to zinc oxide precursor in the S2 step is 1:1-4.

[0012] For the technical solutions described above, further preferably, the molten salt in the S1 step is at least one of NaCl, NaOH, KOH, KCl, and LiCl.

[0013] For the technical solutions described above, further preferably, the heating condition in the S1 step is heating at a rate of 2-20°C / min under an air, oxygen, or nitrogen atmosphere. -1 For the technical solutions described above, further preferably, the heating condition in the S1 step is heating at a rate of 2-20°C / min under an air, oxygen, or nitrogen atmosphere.

[0014] For the technical solutions described above, further preferably, the zinc oxide precursor in the S2 step is selected from at least one of zinc nitrate, zinc sulfate, zinc carbonate, zinc acetate, and zinc phosphate.

[0015] For the technical solutions described above, further preferably, the base in the S2 step is selected from at least one of sodium hydroxide and potassium hydroxide.

[0016] For the technical solutions described above, further preferably, 1 part by weight of dicyandiamide is uniformly mixed and ground with 0.3-0.5 parts by weight of NaOH, and is heated at a rate of 2-5 ℃ / min to 330-400 ℃ under an air atmosphere, and is cooled to room temperature after being kept at a constant temperature for 2-4 h to obtain PHI; 1 part by weight of PHI is placed in an aqueous solution with 1-4 parts by weight of zinc nitrate, sodium hydroxide is added to adjust the pH value of the solution to >10, and after stirring and mixing, the mixture is transferred to a hydrothermal reactor for reaction at 160-200 ℃ for 10-16 h, and is cooled to room temperature after the reaction is completed, and is washed and dried to obtain a PHI / zinc oxide heterojunction photocatalyst. -1 For the technical solutions described above, further preferably, 1 part by weight of dicyandiamide is uniformly mixed and ground with 0.3-0.5 parts by weight of NaOH, and is heated at a rate of 2-5 ℃ / min to 330-400 ℃ under an air atmosphere, and is cooled to room temperature after being kept at a constant temperature for 2-4 h to obtain PHI; 1 part by weight of PHI is placed in an aqueous solution with 1-4 parts by weight of zinc nitrate, sodium hydroxide is added to adjust the pH value of the solution to >10, and after stirring and mixing, the mixture is transferred to a hydrothermal reactor for reaction at 160-200 ℃ for 10-16 h, and is cooled to room temperature after the reaction is completed, and is washed and dried to obtain a PHI / zinc oxide heterojunction photocatalyst.

[0017] The present application also protects the PHI / zinc oxide heterojunction photocatalyst prepared by the above method.

[0018] Application of the PHI / zinc oxide heterojunction photocatalyst.

[0019] For the technical solutions described above, further preferably, the application is efficient activation of molecular oxygen under visible light irradiation, to realize isopropylbenzene oxidation to prepare cumene hydroperoxide under normal temperature and pressure and in a solvent-free condition.

[0020] For the technical solutions described above, further preferably, the application is to use cumene hydroperoxide as a platform peroxide to realize cascade oxidation of benzylamine coupling to form imine and oxidation of thioether to form a series of sulfoxide compounds.

[0021] For the technical solutions described above, further preferably, the application is to use the PHI / zinc oxide prepared by the above method of the present application as a photocatalyst, isopropylbenzene as a solvent, molecular oxygen as an oxidant, cumene hydroperoxide as an initiator, benzylamine compounds or thioether compounds as substrates, and visible light or ultraviolet light as an excitation light source to perform photocatalytic reaction.

[0022] For the technical solutions described above, further preferably, the excitation light source includes visible light of 400-760 nm or ultraviolet light of 200-400 nm. Preferably, the excitation light source is purple light (395 nm), blue light (440 nm), or full-waveband white light.

[0023] For the technical solutions described above, further preferably, the mass ratio of the initiator to the solvent is 1:2-1:20; the mass ratio of the substrate to the solvent is 1:2-1:20; the mass ratio of the photocatalyst to the substrate is 1:1-1:5. Still further preferably, the mass ratio of the initiator to the solvent is 1:5-1:10; the mass ratio of the substrate to the solvent is 1:10-1:20; the mass ratio of the photocatalyst to the substrate is 1:1-1:2.

[0024] For the technical solutions described above, further preferably, the oxidant is oxygen and / or air.

[0025] For the technical solutions described above, further preferably, the benzylamine compound is as shown in formula I or as shown in formula II:

[0026]

[0027] wherein the substituent R1 adjacent to, interposed between or opposite to each other on the benzene ring is selected from one of hydrogen, methyl, methoxy, amino, tert-butyl, trifluoromethyl, bromine, chlorine, iodine;

[0028]

[0029] wherein the substituent R1 adjacent to, interposed between or opposite to each other on the benzene ring is selected from one of hydrogen, methyl, methoxy, amino, nitro, bromine, chlorine, iodine or pyridyl; R2 is selected from one of methyl, ethyl or phenyl.

[0030] Advantages of the present application:

[0031] The application discloses a PHI / zinc oxide heterojunction photocatalyst synthesized at low temperature. Under green and mild conditions, the photocatalyst realizes oxidation of a CM benzyl C-H bond by activated molecular oxygen to prepare high-restricted cumene hydroperoxide. On this basis, the photocatalyst realizes imine formation by coupling of benzylamine and realizes generation of a series of sulfoxide compounds by oxidation of a thioether. The photocatalyst also has good cycle stability and can be recycled repeatedly. The application shows advantages of a high-activity carbon nitride-based photocatalyst in the field of organic conversion and provides an important platform for realizing intrinsically safe, green and efficient oxidation reactions by a peroxide strategy. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A transmission electron microscope (TEM) image of a PHI / zinc oxide heterojunction photocatalyst (NCN / ZnO).

[0033] Figure 2 X-ray diffraction (XRD) spectra of different photocatalysts.

[0034] Figure 3The effect of different photocatalyst dosages on the reaction; as shown in the figure, the selectivity of the target product is best when the catalyst dosage is 0.10g.

[0035] Figure 4 The effect of different NaOH dosages on the reaction; as shown in the figure, the selectivity of the target product is best when the NaOH dosage is 90 mmol.

[0036] Figure 5 The effect of different initiator dosages on the reaction; as shown in the figure, the selectivity of the target product is best when the CHP dosage is 2 mmol.

[0037] Figure 6 The effect of different light sources on the reaction; as shown in the figure, the substrate conversion rate and the selectivity of the target product are the best when irradiated with white light.

[0038] Figure 7 The effect of different amounts of NCN and zinc oxide precursor on the reaction; as shown in the figure, the selectivity of the target product is the best when the NCN:zinc oxide precursor ratio is 2:8. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0040] Example 1

[0041] (1) Place 10g of dicyandiamide and 0.36g of NaOH in a mortar, grind thoroughly, then transfer to a muffle furnace and heat at 5℃ for 5 minutes under an air atmosphere. -1 The mixture was heated to 350°C at a constant temperature for 2 hours and then cooled to room temperature to obtain PHI(NCN).

[0042] (2) 8g of zinc nitrate and 2g of NCN were placed in 40ml of water, and NaOH was added to adjust the pH value to >10. The mixture was stirred for 30min, then transferred to a hydrothermal reactor at 180℃ and reacted for 12h. After the reaction, the mixture was cooled to room temperature, washed five times with ethanol and water, and then dried in an oven at 100℃. The resulting solid powder was labeled as NCN / ZnO. NCN nanosheets grew well on the ZnO surface and were tightly wrapped around ZnO, forming a sheet-like core-layer structure. The thickness of the NCN nanosheets was 3-5nm. Figure 1 As shown. ZnO prepared from zinc nitrate has a wurtzite crystal structure, as shown. Figure 2 As shown.

[0043] (3) Take 0.10 g of the NCN / ZnO photocatalyst prepared in step (2), 10 mmol of CM, and 2 mmol of CHP, and add them to a 20 ml reaction tube equipped with magnetic stirring and an air inlet. After vacuum replacement, seal the reaction tube and place it in a Wattcas light reactor, and connect the air inlet of the reaction tube to an oxygen balloon to provide molecular oxygen for the reaction system. Under the condition of room temperature and normal pressure white light irradiation with an intensity of 10 W, continuously react for 24 h; after the reaction is completed, separate the photocatalyst solid particles by centrifugation at 1200 r / min for 10 min. Performance detection: analyze the oxidation products by GC (SHIMADZU GC-2014, capillary column SE-3030 m x 0.32 mm x 1.0 μm), the conversion rate of CM is 28.7%, and the selectivity of CHP is 92.0%.

[0044] Example 2

[0045] According to the method of Example 1, except that "2 g NCN" in step (2) of Example 1 is replaced by "3 g, 5 g", respectively; the obtained solid powders are marked as NCN / ZnO-3, NCN / ZnO-5, respectively.

[0046] According to the method of step (3) in Example 1, except that "NCN / ZnO" is replaced by NCN / ZnO-3; performance detection: the conversion rate of CM is 26.9%, and the selectivity of CHP is 90.1%.

[0047] According to the method of step (3) in Example 1, except that "NCN / ZnO" is replaced by NCN / ZnO-5; performance detection: the conversion rate of CM is 30.3%, and the selectivity of CHP is 88.6%.

[0048] Example 3

[0049] Transfer 10 g of dicyandiamide and NaOH (take 3.2 g, 3.6 g, 4.0 g, and 4.4 g of different weights, respectively) to a mortar, grind repeatedly for 15 min, then transfer to a muffle furnace, heat to 350°C at a rate of 5°C / min under an air atmosphere, and cool to room temperature after constant temperature for 2 h to obtain PHI (NCN-3.2, NCN-3.6, NCN-4.0, and NCN-4.4). -1

[0050] Take 0.10 g of the above NCN-3.2 photocatalyst, 10 mmol of CM, and 2 mmol of CHP, and add them to a reaction tube, and continuously react for 24 h under the condition of room temperature and normal pressure white light irradiation according to Example 1; the conversion rate of CM is 22.9%, and the selectivity of CHP is 91.5%.

[0051] ​Weigh 0.10g of the above-mentioned NCN-3.6 photocatalyst, 10mmol of CM, and 2mmol of CHP and add them to the reaction tube. React continuously for 24h under room temperature and atmospheric pressure white light irradiation conditions as in Example 1. The conversion rate of CM is 25.7%, and the selectivity of CHP is 90.9%.

[0052] Weigh 0.10g of the above-mentioned NCN-4.0 photocatalyst, 10mmol of CM, and 2mmol of CHP and add them to the reaction tube. React continuously for 24h under white light irradiation at room temperature and atmospheric pressure as in Example 1. The conversion rate of CM is 26.9%, and the selectivity of CHP is 88.2%.

[0053] Weigh 0.10g of NCN-4.4 photocatalyst, 10mmol of CM, and 2mmol of CHP and add them to a reaction tube. React continuously for 24h under room temperature and atmospheric pressure white light irradiation conditions as in Example 1. The conversion rate of CM is 28.4%, and the selectivity of CHP is 86.8%.

[0054] Example 4

[0055] 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, and 2 mmol of CHP from Example 1 were weighed and added to a reaction tube. The reaction was carried out continuously for 24 h under white light irradiation at room temperature and atmospheric pressure with a light intensity of 10 W. The photocatalyst separated by centrifugation was washed three times with ethanol and water, and the filter cake was dried at 100°C for 12 h before being recycled for the next cycle. The conversion rate of CM was 28.7%, and the selectivity of CHP was 92.0%. After two cycles, the conversion rate of CM was 28.0%, and the selectivity of CHP was 91.3%. After three cycles, the conversion rate of ethylbenzene was 27.4%, and the selectivity of acetophenone was 90.1%. After four cycles, the conversion rate of ethylbenzene was 26.5%, and the selectivity of acetophenone was 88.7%. After five cycles, the conversion rate of ethylbenzene was 25.8%, and the selectivity of acetophenone was 85.9%. The conversion rate of CM and the selectivity of CHP remained almost constant throughout five consecutive operating cycles, indicating that the photocatalyst has stable catalytic ability in the photocatalytic oxidation process.

[0056] Example 5: Screening of Photocatalysts

[0057] Dicyandiamide or melamine was placed in ceramic crucibles and heated in a muffle furnace at 5°C for 5 min in an air atmosphere. -1 The mixture was heated to 550°C (4 h) at a certain rate, and then cooled to room temperature. The resulting solid powders were labeled as PCN and MCN, respectively. The reaction was carried out continuously for 24 h under room temperature, atmospheric pressure, and white light irradiation conditions, as described in Example 1. The conversion rates of CM were 30.1% and 24.0%, respectively, and the selectivities of CHP were 71.9% and 73.4%, respectively.

[0058] CN-TiO2 and PCN-ZnO, respectively. The conversion of CM and the selectivity of CHP were 31.9% and 70.6%, respectively, for PCN-TiO2, and 39.0% and 83.7%, respectively, for PCN-ZnO, under the same reaction conditions as in Example 1 for 24 h under white light irradiation at room temperature and atmospheric pressure.

[0059] CN was placed in a ceramic crucible and heated in a muffle furnace under air atmosphere at a rate of 5 °C min -1 -1 to 350 °C, 450 °C, 550 °C, 650 °C (2 h), and then cooled to room temperature. The obtained solid powders were labeled as CN, CN-450, CN-550, and CN-650, respectively. The conversion of CM and the selectivity of CHP were 21.2%, 25.8%, 28.1%, and 36.6%, respectively, for CN, CN-450, CN-550, and CN-650, under the same reaction conditions as in Example 1 for 24 h under white light irradiation at room temperature and atmospheric pressure.

[0060] Zinc nitrate (8 g) and CN (2 g) were placed in 40 ml of aqueous solution, and NaOH was added to adjust the pH value of the aqueous solution to > 10. The mixture was stirred for 30 min and then transferred to a hydrothermal reactor at 180 °C for 12 h. After the reaction, the mixture was cooled to room temperature, washed with ethanol and water for 5 times, and then dried in an oven at 100 °C. The obtained solid powder was labeled as CN / ZnO. The conversion of CM and the selectivity of CHP were 23.4% and 89.6%, respectively, under the same reaction conditions as in Example 1 for 24 h under white light irradiation at room temperature and atmospheric pressure.

[0061] CN was placed in a muffle furnace again and heated under air atmosphere at a rate of 5 °C min -1 -1 to 350 °C, 450 °C, 550 °C (2 h), and then cooled to room temperature. The obtained solid powders were labeled as ECN, RCN, and VCN, respectively. The conversion of CM and the selectivity of CHP were 23.7%, 28.5%, and 42.4%, respectively, for ECN, RCN, and VCN, under the same reaction conditions as in Example 1 for 24 h under white light irradiation at room temperature and atmospheric pressure.

[0062] Zinc nitrate (10 g) was placed in 40 ml of aqueous solution, and hydrothermal treatment was carried out according to the same procedure as above. The obtained solid powder was labeled as ZnO. The conversion of CM and the selectivity of CHP were 12.3% and 88.1%, respectively, under the same reaction conditions as in Example 1 for 24 h under white light irradiation at room temperature and atmospheric pressure.

[0063] Among the above photocatalysts, NCN / ZnO has the largest specific surface area, the strongest visible light absorption capacity, the lowest charge carrier recombination rate, and the fastest charge carrier migration rate. + The conjugated structure of CN is etched and destroyed in the process of low-temperature assisted thermal shrinkage, resulting in partial decomposition of the oxazine ring structure to form C≡N, thereby obtaining a surface alkali-rich hydroxyl and a cyanogen-modified CN. The construction of a heterojunction with ZnO accelerates the transfer of charges along a fixed path, improving the adsorption of reactants and the utilization rate of electrons.

[0064] Example 6 Optimization conditions

[0065] Using the photocatalyst NCN / ZnO prepared in Example 1, the following experiments were conducted:

[0066] (1) The single variable was the amount of different photocatalysts, and the other experimental conditions were the same as in Example 1, and the results are shown in Table 1. Figure 3

[0067] (2) The single variable was the amount of different NaOH, and the other experimental conditions were the same as in Example 1, and the results are shown in Table 2. Figure 4

[0068] (3) The single variable was the amount of different CHP, and the other experimental conditions were the same as in Example 1, and the results are shown in Table 3. Figure 5

[0069] (4) The single variable was the different light source, and the other experimental conditions were the same as in Example 1, and the results are shown in Table 4. Figure 6

[0070] (5) The single variable was the mass ratio of NCN to zinc oxide precursor, and the other experimental conditions were the same as in Example 1, and the results are shown in Table 5. Figure 7

[0071] Example 7 Preparation of imine compounds

[0072] Using the photocatalyst NCN / ZnO prepared in Example 1, the following experiments were conducted:

[0073] 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of benzylamine were weighed into a reaction tube, and the reaction was continuously carried out under the room temperature and atmospheric pressure white light irradiation conditions of Example 1 for 18 h, with a corresponding imine yield of 95%.

[0074] ​​​​​Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 88%.

[0075] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 74%.

[0076] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 88%.

[0077] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 74%.

[0078] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 74%.

[0079] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 74%.

[0080] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 74%.

[0081] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-methylbenzylamine in a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 74%.

[0082] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-bromo benzylamine in the reaction tube, and continuously react for 18 h under the white light irradiation conditions at room temperature and normal pressure according to Example 1, and the yield of the corresponding imine is 69%.

[0083] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-bromo benzylamine in the reaction tube, and continuously react for 18 h under the white light irradiation conditions at room temperature and normal pressure according to Example 1, and the yield of the corresponding imine is 64%.

[0084] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 2-bromo benzylamine in the reaction tube, and continuously react for 18 h under the white light irradiation conditions at room temperature and normal pressure according to Example 1, and the yield of the corresponding imine is 48%.

[0085] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-methoxy benzylamine in the reaction tube, and continuously react for 18 h under the white light irradiation conditions at room temperature and normal pressure according to Example 1, and the yield of the corresponding imine is 85%.

[0086] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-methoxy benzylamine in the reaction tube, and continuously react for 18 h under the white light irradiation conditions at room temperature and normal pressure according to Example 1, and the yield of the corresponding imine is 77%.

[0087] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 2-methoxy benzylamine in the reaction tube, and continuously react for 18 h under the white light irradiation conditions at room temperature and normal pressure according to Example 1, and the yield of the corresponding imine is 58%.

[0088] Take 0.10 g of NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-amino benzylamine in the reaction tube, and continuously react for 18 h under the white light irradiation conditions at room temperature and normal pressure according to Example 1, and the yield of the corresponding imine is 50%.

[0089] Take 0.10 g of the NCN / ZnO photocatalyst in Example 1, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-tert-butylbenzylamine into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 18 h according to Example 1, and the yield of the corresponding imine is 76%.

[0090] Example 8: Preparation of sulfoxide compounds

[0091] The following experiments were performed using the photocatalyst NCN / ZnO prepared in Example 1.

[0092] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of methyl phenyl sulfide into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, and the yield of the corresponding sulfoxide is 96%.

[0093] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-methyl anisole sulfide into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, and the yield of the corresponding sulfoxide is 99%.

[0094] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-methoxy anisole sulfide into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, and the yield of the corresponding sulfoxide is 93%.

[0095] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 2-methylthio pyridine into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, and the yield of the corresponding sulfoxide is 90%.

[0096] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-fluoro anisole sulfide into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, and the yield of the corresponding sulfoxide is 96%.

[0097] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-fluoro anisole sulfide into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, and the yield of the corresponding sulfoxide is 95%.

[0098] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 2-fluoro-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 95%.

[0099] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-chloro-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 95%.

[0100] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-chloro-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 95%.

[0101] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 2-chloro-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 94%.

[0102] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-bromo-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 91%.

[0103] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 3-bromo-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 89%.

[0104] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 2-bromo-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 88%.

[0105] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-amino-thioanisole into a reaction tube, and continuously react under the white light irradiation conditions of room temperature and normal pressure for 14 h according to Example 1, to obtain a corresponding sulfoxide with a yield of 78%.

[0106] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of 4-nitrothioanisole into a reaction tube, and continuously react for 14 h under the white light irradiation conditions of room temperature and normal pressure in Example 1. The yield of the corresponding sulfoxide is 54%.

[0107] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of dipropyl sulfide into a reaction tube, and continuously react for 14 h under the white light irradiation conditions of room temperature and normal pressure in Example 1. The yield of the corresponding sulfoxide is 97%.

[0108] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of dipropyl sulfide into a reaction tube, and continuously react for 14 h under the white light irradiation conditions of room temperature and normal pressure in Example 1. The yield of the corresponding sulfoxide is 97%.

[0109] Take 0.10 g of the above NCN / ZnO photocatalyst, 10 mmol of CM, 2 mmol of CHP, and 1 mmol of dipropyl sulfide into a reaction tube, and continuously react for 14 h under the white light irradiation conditions of room temperature and normal pressure in Example 1. The yield of the corresponding sulfoxide is 97%.

[0110] Comparative Example 1

[0111] Place guanidine hydrochloride or thiourea or ammonium thiocyanate in a ceramic crucible, and heat to 550°C (4 h) at a rate of 5°C min -1 in a muffle furnace in an air atmosphere, and then cool to room temperature to obtain solid powders, which are marked as GCN, SCN, and TCN, respectively. Continuously react for 24 h under the white light irradiation conditions of room temperature and normal pressure in Example 1; the conversion rates of CM are 26.5%, 58.5%, and 46.3%, respectively, and the selectivities of cumene hydroperoxide are 55.2%, 40.1%, and 63.2%, respectively.

[0112] Comparative Example 2

[0113] Place 4 g of dicyandiamide, 3 g of melamine, and 3 g of ammonium thiocyanate (5 g of dicyandiamide and 5 g of melamine, 5 g of dicyandiamide and 5 g of guanidine hydrochloride, 5 g of dicyandiamide and 5 g of ammonium thiocyanate, or 5 g of dicyandiamide and 5 g of urea) in a ceramic crucible, and treat by the same calcination procedure as above to obtain solid powders, which are marked as DMTPCN, DMPCN, DGPCN, DTPCN, and DUPCN, respectively. Continuously react for 24 h under the white light irradiation conditions of room temperature and normal pressure in Example 1; the conversion rates of CM are 52.1%, 51.4%, 45.1%, 29.1%, and 48.3%, respectively, and the selectivities of CHP are 59.0%, 56.3%, 58.6%, 61.0%, and 63.1%, respectively.

[0114] Comparative Example 3

[0115] Take 20 g of dicyandiamide and 10 g of bismuth vanadate or tungsten hydroxide or cadmium oxide or activated carbon into a beaker, add 40 mL of deionized water, stir and heat to 65°C until the water evaporates to dryness, then wash with ethanol and water until the pH value is neutral, transfer the solid powder to an oven at 100°C for drying, and treat with the same calcination procedure as above. The obtained catalysts are respectively marked as PCN-BiO4V, PCN-WO3, PCN-CdO and PCN-C. According to the room temperature and atmospheric pressure white light irradiation conditions of Example 1, continuously react for 24 h; the conversion rates of CM are 50.1%, 25.8%, 61.0% and 70.5% respectively, and the selectivities of CHP are 28.9%, 47.6%, 62.9% and 3.9% respectively.

[0116] Comparative Example 4

[0117] Take 0.10 g of NCN / ZnO photocatalyst in Example 1, 10 mmol of CM, 2 mmol of CHP and 1 mmol of 3-aminobenzylamine into a reaction tube, and continuously react for 18 h under the room temperature and atmospheric pressure white light irradiation conditions of Example 1. The yield of the corresponding imine is 39%.

[0118] Comparative Example 5

[0119] Take 0.10 g of NCN / ZnO photocatalyst in Example 1, 10 mmol of CM, 2 mmol of CHP and 1 mmol of 4-trifluoromethylbenzylamine into a reaction tube, and continuously react for 18 h under the room temperature and atmospheric pressure white light irradiation conditions of Example 1. The yield of the corresponding imine is 22%.

[0120] Comparative Example 6

[0121] Take 0.10 g of NCN / ZnO photocatalyst in Example 1, 10 mmol of CM and 2 mmol of CHP into a reaction tube, and continuously react for 24 h under the room temperature and atmospheric pressure conditions of Example 1. Replace the light source with dark conditions. The conversion rate of CM is 5.1%.

[0122] Comparative Example 7

[0123] Take 0.10 g of NCN / ZnO photocatalyst in Example 1, 10 mmol of CM into a reaction tube, and continuously react for 24 h under the room temperature and atmospheric pressure white light irradiation conditions of Example 1. The conversion rate of CM is 12.3%, and the selectivity of CHP is 71.2%.

[0124] Comparative Example 8

[0125] The reaction tube was charged with 0.10 g of the NCN / ZnO photocatalyst, 10 mmol of CM, and 2 mmol of CHP, and the reaction was continuously carried out under the same conditions as in Example 1 for 24 h at room temperature under normal pressure. The oxygen atmosphere was replaced with an air atmosphere, and the conversion of CM was 16.1% and the selectivity of CHP was 69.5%.

[0126] The above description is merely preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions easily conceived by those skilled in the art within the technical scope disclosed by the present application should be encompassed within the protection scope of the present application. Therefore, the protection scope of the present application should be defined by the protection scope of the claims.

Claims

1. An application of a PHI / zinc oxide heterojunction photocatalyst, characterized in that: The application uses cumene hydroperoxide as a platform peroxide, which is tandemly oxidized with benzylamine to form imine, and then thioethers are oxidized to generate a series of sulfoxide compounds. The structure of the PHI / zinc oxide heterojunction photocatalyst is that PHI nanosheets are grown on the surface of ZnO and encapsulated by ZnO to form a sheet-like core layer structure; the thickness of the PHI nanosheets is 3-5 nm; and the ZnO has a wurtzite crystal structure. The PHI / zinc oxide heterojunction photocatalyst was prepared by a low-temperature synthesis method including the following steps: S1: PHI precursor and molten salt are mixed at a mass ratio of 1:0.1 to 2, heated to 330-650℃ under an atmosphere and kept at a constant temperature, and then cooled to room temperature to obtain PHI; S2: PHI and zinc oxide precursor are placed in an aqueous solution, and after adjusting the pH to >10 with alkali, they are reacted at 120-240℃. After cooling, washing and drying, the photocatalyst PHI / ZnO is obtained; wherein the mass ratio of PHI to zinc oxide precursor is 1:0.1-10.

2. The application according to claim 1, characterized in that: The PHI precursor in step S1 is selected from at least one of melamine, urea, dicyandiamide, ammonium thiocyanate, thiourea, or guanidine hydrochloride. The molten salt in step S1 is selected from at least one of NaCl, NaOH, KOH, KCl, and LiCl.

3. The application according to claim 1, characterized in that: The zinc oxide precursor in step S2 is selected from at least one of zinc nitrate, zinc sulfate, zinc carbonate, zinc acetate, and zinc phosphate. The base used in step S2 is selected from at least one of sodium hydroxide and potassium hydroxide.

4. The application according to claim 1, characterized in that: The steps for preparing the PHI / zinc oxide heterojunction photocatalyst include: mixing 1 part by weight of dicyandiamide with 0.3-0.5 parts by weight of NaOH, and then incubating at 2-5°C in air for 1 minute. -1 The solution was heated to 330-400℃ and held at that temperature for 2-4 hours before being cooled to room temperature to obtain PHI. One part by weight of PHI and one to four parts by weight of zinc nitrate were placed in an aqueous solution, and sodium hydroxide was added to adjust the pH value of the solution to >10. After stirring and mixing, the solution was transferred to a hydrothermal reactor and reacted at 160-200℃ for 10-16 hours. After the reaction was completed, the solution was cooled to room temperature, washed and dried to obtain the photocatalyst NCN / ZnO.

5. The application according to claim 1, characterized in that: The application uses PHI / zinc oxide as a photocatalyst, cumene as a solvent, molecular oxygen as an oxidant, cumene hydroperoxide as an initiator, benzylamine or thioether compounds as substrates, and visible or ultraviolet light as an excitation source for photocatalytic reaction; the mass ratio of the initiator to the solvent is 1:2 to 1:20; the mass ratio of the substrate to the solvent is 1:2 to 1:20; and the mass ratio of the photocatalyst to the substrate is 1:1 to 1:

5.

6. The application according to claim 5, characterized in that: The excitation source includes visible light of 400-760 nm or ultraviolet light of 200-400 nm.

7. The application according to claim 5, characterized in that: The benzylamine compound is of formula I or formula II: I Wherein, the substituent R1 adjacent to, intercalated with or para-positioned on the benzene ring is selected from one of hydrogen, methyl, methoxy, amino, tert-butyl, trifluoromethyl, bromine, chlorine and iodine; Ⅱ In this embodiment, the substituent R1 adjacent to, intercalated with, or para-positioned on the benzene ring is selected from one of hydrogen, methyl, methoxy, amino, nitro, bromine, chlorine, iodine, or pyridyl; and R2 is selected from one of methyl, ethyl, or phenyl.

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