A CdS / ZnCr2O4 photocatalyst, its preparation method and application

Abstract

This invention discloses a CdS / ZnCr2O4 photocatalyst, its preparation method, and its applications. The CdS / ZnCr2O4 photocatalyst is a binary composite material composed of CdS nanorods and ZnCr2O4 nanoparticles, wherein the ZnCr2O4 nanoparticles are located on the surface of the CdS nanorods; the CdS nanorods and ZnCr2O4 nanoparticles form a heterojunction through a solvothermal reaction. The CdS / ZnCr2O4 photocatalyst prepared by this invention can achieve photocatalytic aldehyde oxidation and amidation reactions under mild conditions, with high yield, low cost, easy operation, and environmental friendliness, showing promising industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of materials preparation and catalytic synthesis technology, specifically to a CdS / ZnCr2O4 photocatalyst, its preparation method, and its application. Background Technology

[0002] Visible light-mediated photoredox catalysis has become a green synthetic strategy. Compared to homogeneous catalysts such as ruthenium or iridium transition metal complexes and various organic dyes, photoredox catalysis using heterogeneous photocatalysts has the inherent advantage of easy catalyst separation and recovery, attracting great interest in both industry and academia. Amides, as the structural backbone of proteins and peptides, and key functional groups in natural products and pharmaceuticals, play an important role in organic synthesis. Direct cross-dehydrogenation coupling of aldehydes and amines is one of the most economical methods for preparing amides. Various methods exist for forming amide bonds from aldehydes and amines, but traditional synthesis requires expensive transition metal catalysts, high temperatures, or excessive use of strong oxidants. Several reports have been published both domestically and internationally. For example, the literature (Asian J.Org.Chem. 2019, 8, 1411-1414) describes the oxidative amidation of aldehydes under oxygen conditions using anthraquinone as a photocatalyst, but the yield is low, and the oxygen requirement makes industrialization difficult. The literature (Org.Biomol.Chem. 2016, 14, 7028-7037) describes the oxidative amidation of aldehydes under air conditions using boron dipyrrolidone as a photocatalyst, but this requires the addition of 2,6-di-tert-butyl-p-cresol. Most existing methods involve the use of expensive catalysts or require additives, and the separation of homogeneous photocatalysts remains a problem. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies by providing a CdS / ZnCr2O4 photocatalyst, its preparation method, and its applications. This heterogeneous photocatalyst can be used for the photocatalytic oxidation and amidation of aldehydes, achieving high yields with low catalyst amounts under air and visible light conditions. This catalyst is low-cost, highly active, and environmentally friendly, showing promising prospects for industrial application.

[0004] ZnCr2O4 is a typical chromium-based spinel semiconductor with wide applications in gas sensing, humidity sensing, syngas conversion, and adsorption. However, its large bandgap and poor stability limit its application in photocatalysis. This invention combines ZnCr2O4 with CdS, which has good visible light absorption properties, to obtain an optimally proportioned CdS / ZnCr2O4 composite material, while simultaneously reducing the carrier recombination rate in CdS. The resulting composite material exhibits good electron-hole separation efficiency and can be used to efficiently achieve the photocatalytic oxidation and amidation reaction of aldehydes. This reaction can be carried out in air without other additives. The CdS / ZnCr2O4 composite material, as a heterogeneous catalyst, is easy to separate and has good prospects for industrialization.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A CdS / ZnCr2O4 photocatalyst, wherein the CdS / ZnCr2O4 photocatalyst is a binary composite material composed of CdS nanorods and ZnCr2O4 nanoparticles, wherein the ZnCr2O4 nanoparticles are on the surface of the CdS nanorods.

[0007] Preferably, CdS nanorods and ZnCr2O4 nanoparticles form a heterojunction through a solvothermal reaction.

[0008] Further preferred, CdS nanorods and ZnCr2O4 nanoparticles are combined via ZnCr2O4 nanoparticles and Cd... 2+ The source and thiourea undergo a solvothermal reaction to form CdS nanorods and ZnCr2O4 nanoparticles containing heterojunctions.

[0009] Preferably, the CdS / ZnCr2O4 photocatalyst can be used for photocatalytic aldehyde oxidation and amidation reactions.

[0010] The preparation method of the above-mentioned CdS / ZnCr2O4 photocatalyst includes the following steps:

[0011] (1) Cr 6+ Source, Zn 2+ The source, water and ethylene glycol are mixed and stirred to form a dispersion, which is then subjected to a solvothermal reaction. After the reaction is completed, the mixture is washed, dried and then calcined at high temperature to obtain ZnCr2O4 nanoparticles.

[0012] (2) The ZnCr2O4 nanoparticles and Cd prepared in step (1) are added to the substrate. 2+ The source, thiourea and ethylenediamine were mixed and stirred to form a dispersion, and a solvothermal reaction was carried out. After the reaction was completed, the mixture was washed and dried to obtain the CdS / ZnCr2O4 photocatalyst.

[0013] Preferably, the Cr described in step (1) 6+Source, Zn 2+ The dispersion formed by mixing and stirring Cr, water, and ethylene glycol refers to: 6+ The source is dissolved in water and added dropwise to a solution containing Zn. 2+ In the source of ethylene glycol;

[0014] Preferably, the Cr in step (1) 6+ Cr in the source 6+ and Zn 2+ Zn in the source 2+ The molar ratio is 3-1:3-1;

[0015] Further preferably, the Cr described in step (1) 6+ Cr in the source 6+ and Zn 2+ Zn in the source 2+ The molar ratio is 3-1:1;

[0016] Preferably, the volume ratio of water to ethylene glycol in step (1) is 2-20:2-20;

[0017] More preferably, the volume ratio of water to ethylene glycol in step (1) is 5-15:5-15;

[0018] Preferably, the Cr in step (1) 6+ The mass-to-volume ratio of the source and water is 2-5g: 2-20mL;

[0019] Further preferably, the Cr in step (1) 6+ The mass-to-volume ratio of the source and water is 2-4g:2-15mL;

[0020] Preferably, the stirring time in step (1) is 10-60 min;

[0021] More preferably, the stirring time in step (1) is 20-50 min;

[0022] Preferably, the temperature of the solvothermal reaction in step (1) is 100-200℃, and the time of the solvothermal reaction is 12-36h;

[0023] More preferably, the temperature of the solvothermal reaction in step (1) is 120-180℃, and the time of the solvothermal reaction is 15-32h;

[0024] Preferably, the Cr in step (1) 6+ The source is K2Cr2O7 or K2CrO4; the Zn 2+ The source is ZnCl2;

[0025] Preferably, the high-temperature calcination mentioned in step (1) refers to calcination in air;

[0026] Preferably, the high-temperature calcination in step (1) is carried out in a tubular furnace.

[0027] Preferably, the heating rate of the high-temperature calcination in step (1) is 2-10℃ / min; the temperature of the high-temperature calcination is 400-700℃; and the high-temperature calcination time is 1-6h.

[0028] Preferably, the washing method in step (1) is to wash with ultrapure water 3-5 times and ethanol 3-5 times; the drying method is to dry at 40-100℃, in an oven or in a vacuum, for a drying time of more than 6 hours.

[0029] Preferably, the water in step (1) is ultrapure water;

[0030] Preferably, the ZnCr2O4 nanoparticles and Cd2O4 nanoparticles mentioned in step (2) 2+ Cd in the source 2+ The dosage ratio (mass, molar mass, mass) of thiourea is 10-150 mg : 0.1-2 mmol : 200-500 mg;

[0031] More preferably, the ZnCr2O4 nanoparticles and Cd2O4 nanoparticles described in step (2) 2+ Cd in the source 2+ The dosage ratio (mass, molar mass, mass) of thiourea is 20-100 mg : 0.5-2 mmol : 250-450 mg;

[0032] More preferably, the ZnCr2O4 nanoparticles and Cd2O4 nanoparticles described in step (2) 2+ Cd in the source 2+ The dosage ratio (mass, molar mass) of thiourea is 20-150mg (20mg, 23mg, 46mg, 70mg, 93mg, 116mg, 150mg, etc.): 1.25mmol: 250-450mg;

[0033] Preferably, the ethylenediamine and Cd in step (2) 2+ The volume-to-mass ratio of the source is 5-25 mL: 0.2-1 g;

[0034] Further preferably, the ethylenediamine and Cd in step (2) 2+ The volume-to-mass ratio of the source is 5-20 mL: 0.2-0.8 g;

[0035] Preferably, the stirring time in step (2) is 10-60 min;

[0036] More preferably, the stirring time in step (2) is 20-60 min;

[0037] Preferably, the temperature of the solvothermal reaction in step (2) is 100-200℃, and the time of the solvothermal reaction is 12-36h;

[0038] More preferably, the temperature of the solvothermal reaction in step (2) is 120-200℃, and the time of the solvothermal reaction is 12-30h;

[0039] Preferably, the Cd in step (2) 2+ The source is Cd(NO3)2·4H2O.

[0040] Preferably, the washing method in step (2) is to wash with ultrapure water 3-5 times and ethanol 3-5 times; the drying method is to dry at 40-100℃, in an oven or in a vacuum, for a time of more than 6 hours.

[0041] The above-mentioned CdS / ZnCr2O4 photocatalyst is used in photocatalytic organic reactions.

[0042] Preferably, the photocatalytic organic reaction is a photocatalytic aldehyde oxidation and amidation reaction;

[0043] Preferably, the photocatalytic organic reaction is carried out under light irradiation.

[0044] Preferably, the CdS / ZnCr2O4 photocatalyst is used for the photocatalytic oxidation and amidation of aldehydes, comprising the following steps:

[0045] Compound 1, compound 2 and CdS / ZnCr2O4 photocatalyst were dissolved in a solvent and subjected to an aldehyde oxidation-amidation reaction under light irradiation to obtain compound 3;

[0046] The general reaction formula is:

[0047]

[0048] Among them, R 1 Selected from substituted or unsubstituted aryl groups, and substituted or unsubstituted heteroaryl groups; R 2 R 3 Each is independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or R 2 R 3 Together with nitrogen atoms, they form substituted or unsubstituted nitrogen-containing heterocyclic alkyl groups.

[0049] More preferably, the number of substituents in the substituted alkyl, substituted alkoxy, substituted cycloalkyl, substituted heterocycloalkyl, substituted aryl, substituted heteroaryl, and substituted nitrogen-containing heterocycloalkyl groups is one or more, and the multiple substituents may be the same or different; the substituents are one or more of hydrogen, cyano, nitro, halogen (fluorine, chlorine, bromine, iodine), alkyl (1-10 carbon atoms), and alkoxy (1-10 carbon atoms).

[0050] More preferably, the alkyl group in the substituted or unsubstituted alkyl group has 1-10 carbon atoms, the alkoxy group in the substituted or unsubstituted alkoxy group has 1-10 carbon atoms, the cycloalkyl group in the substituted or unsubstituted cycloalkyl group has 3-10 carbon atoms, the total number of carbon atoms and heteroatoms of the heterocycloalkyl group in the substituted or unsubstituted heterocycloalkyl group has 3-10, the aryl group in the substituted or unsubstituted aryl group has 6-12 carbon atoms, the total number of carbon atoms and heteroatoms of the heteroaryl group in the substituted or unsubstituted heteroaryl group has 6-12, and the total number of carbon atoms and heteroatoms of the nitrogen-containing heterocycloalkyl group in the substituted or unsubstituted nitrogen-containing heterocycloalkyl group has 3-10.

[0051] More preferably, the aryl group in the substituted or unsubstituted aryl group has 6 carbon atoms, and the total number of carbon atoms and heteroatoms in the heteroaryl group in the substituted or unsubstituted heteroaryl group is 6.

[0052] More preferably, the aryl group in the substituted or unsubstituted aryl group is a benzene ring.

[0053] More preferably, compound 1 is 4-cyanobenzaldehyde or a derivative thereof;

[0054] More preferably, the illumination is visible light; the conditions for the aldehyde oxidation-amidation reaction include:

[0055] Air or oxygen; the aldehyde oxidation-amidation reaction is carried out at room temperature;

[0056] More preferably, the solvent is one or more of water, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, and dioxane, and the volume molar ratio of the solvent to compound 1 is 5-15 mL / mmol;

[0057] More preferably, the volume molar ratio of the solvent to compound 1 is 8-15 mL / mmol;

[0058] More preferably, the molar ratio of the CdS / ZnCr2O4 photocatalyst to compound 1 is 5-35 mg / mmol; and the molar ratio of compound 1 to compound 2 is 1-5:1-5.

[0059] More preferably, the molar ratio of the CdS / ZnCr2O4 photocatalyst to compound 1 is 10-25 mg / mmol.

[0060] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0061] (1) By constructing a heterojunction, this invention effectively improves the separation efficiency and transport rate of photogenerated carriers in the catalyst, thereby exhibiting high catalytic activity;

[0062] (2) The CdS / ZnCr2O4 photocatalyst prepared in this invention can be used as a highly efficient photocatalyst to achieve aldehyde oxidation and amidation reaction;

[0063] (3) The raw materials of this invention are cheap and readily available, resulting in low input and high returns;

[0064] (4) The reaction conditions of this invention are simple and easy to realize large-scale mass production of aldehyde oxidation amidation. Attached Figure Description

[0065] Figure 1 This is a scanning electron microscope image of the CdS / ZnCr2O4 photocatalyst prepared in Example 1 of the present invention.

[0066] Figure 2 The images show the XRD patterns of the CdS, ZnCr2O4, and CdS / ZnCr2O4 photocatalysts prepared in Examples 1, 6, and 7 of this invention.

[0067] Figure 3-7 The NMR spectrum of the compound obtained in the reaction of Example 1 of this invention is shown. Detailed Implementation

[0068] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically specified, conventional techniques can be referred to. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0069] Example 1

[0070] (1) 3.88 g of K2CrO4 was ultrasonically dissolved in 12.5 mL of pure water, and 1.36 g of ZnCl2 was ultrasonically dissolved in 12.5 mL of ethylene glycol. The K2CrO4 solution was then added dropwise to the ZnCl2 solution, stirred at room temperature for 30 min, transferred to a polytetrafluoroethylene liner, and subjected to a solvothermal reaction in a reactor at 150 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature, and the precipitate was collected by centrifugation, washed several times with ethanol and ultrapure water, and dried in an oven at 60 °C for 12 h. Finally, the obtained solid was placed in a tube furnace and calcined in air at a rate of 5 °C / min to 600 °C for 2 h to obtain ZnCr2O4 nanoparticles.

[0071] (2) The ZnCr2O4 nanoparticles (70 mg), 384 mg of Cd(NO3)2·4H2O, 284 mg of thiourea, and 10 mL of ethylenediamine described in step (1) were added to a polytetrafluoroethylene liner and stirred for 30 min to form a uniform suspension. Then, a solvothermal reaction was carried out in a reactor at 180 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the bright yellow precipitate was collected by centrifugation. It was washed several times with ethanol and ultrapure water and dried in an oven at 60 °C for 12 h to obtain the CdS / ZnCr2O4 photocatalyst.

[0072] The scanning electron microscope (SEM) image of the CdS / ZnCr2O4 photocatalyst obtained in this embodiment is shown below. Figure 1 As shown, the XRD pattern of the CdS / ZnCr2O4 photocatalyst is as follows. Figure 2 As shown, this confirms the composition and morphology of the synthesized material.

[0073] The CdS / ZnCr2O4 photocatalyst obtained in this example was used for the aldehyde oxidation amidation reaction. The specific steps are as follows:

[0074] 26 mg of 4-cyanobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF), and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under a light source (40 W blue LED) for 14 h. After the reaction, 4-(pyrrolidine-1-carbonyl)benzonitrile (3a) was obtained by column chromatography with a yield of 94% (see Table 1). The 1H NMR spectrum of the product is shown below. Figure 3 As shown, the result characterization data is as follows:

[0075]

[0076] 4-(pyrrolidine-1-carbonyl)benzonitrile(3a)

[0077] Yield: 37.6 mg (94%);1 H NMR (500MHz, CDCl3) δ7.69 (d, J = 8.0Hz, 2H),

[0078] 7.60(d,J=8.0Hz,2H),3.64(t,J=7.0Hz,2H),3.36(t,J=6.6Hz,2H),2.00-1.94(m,2H),1.93-1.87(m,2H).

[0079] 20 μL of benzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF), and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under irradiation (40W blue LED) for 24 h. After the reaction, phenyl(pyrrolidine-1-yl) methyl ketone (3b) was obtained by column chromatography with a yield of 62%. The 1H NMR spectrum of the product is shown below. Figure 4 As shown, the result characterization data is as follows:

[0080]

[0081] phenyl(pyrrolidin-1-yl)methanone(3b)

[0082] Yield: 21.7 mg (62%); 1 H NMR (500MHz, CDCl3) δ7.52-7.50(m,2H),7.40(d,J=6.5Hz,3H),3.65(t,J=7.0Hz,2H),3.43(t,J=6.6Hz,2H),2.00-1.93(m,2H),1.90-1.85(m,2H).

[0083] 29 mg of p-chlorobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF), and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under a 40 W blue LED light source for 24 h. After the reaction, (4-chlorophenyl)(pyrrolidine-1-yl)methyl ketone (3c) was obtained by column chromatography with a yield of 89%. The 1H NMR spectrum of the product is shown below. Figure 5 As shown, the result characterization data is as follows:

[0084]

[0085] 4-chlorophenyl)(pyrrolidin-1-yl)methanone(3c)

[0086] Yield: 37.2 mg (89%); 1H NMR (500MHz, CDCl3) δ7.47 (d, J = 8.4Hz, 2H),

[0087] 7.38(d,J=8.4Hz,2H),3.64(t,J=7.0Hz,2H),3.42(t,J=6.6Hz,2H),2.00-1.94(m,2H),1.91-1.86(m,2H).

[0088] 24 μL of p-methoxybenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF), and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under a 40W blue LED light source for 24 h. After the reaction, (4-methoxyphenyl)(pyrrolidine-1-yl)methyl ketone (3d) was obtained by column chromatography with a yield of 60%. The 1H NMR spectrum of the product is shown below. Figure 6 As shown, the result characterization data is as follows:

[0089]

[0090] (4-methoxyphenyl)(pyrrolidin-1-yl)methanone(3d)

[0091] Yield: 24.6 mg (59%); 1 H NMR (500MHz, CDCl3) δ7.56-7.46 (m, 2H), 6.90 (d, J = 8.8Hz, 2H), 3.83 (s, 3H), 3.6 4(t,J=7.0Hz,2H),3.48(t,J=6.6Hz,2H),1.97-1.93(m,2H),1.89-1.86(m,2H).

[0092] 26 mg of 4-cyanobenzaldehyde, 53 μL of morpholine, 2 mL of tetrahydrofuran (THF), and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask, and the reaction was carried out under irradiation (40 W blue LED) for 18 h. After the reaction, 4-(morpholine-4-carbonyl)benzonitrile (3e) was obtained by column chromatography with a yield of 90%. The 1H NMR spectrum of the product is shown below. Figure 7 As shown, the result characterization data is as follows:

[0093]

[0094] 4-(morpholine-4-carbonyl)benzonitrile(3e)

[0095] Yield: 38.9 mg (90%); 1H NMR (500MHz, CDCl3) δ7.72 (d, J = 8.2Hz, 2H),

[0096] 7.50(d,J=8.2Hz,2H),3.77(s,4H),3.62(s,2H),3.37(s,2H).

[0097] Example 2

[0098] (1) 3.88 g of K2CrO4 was ultrasonically dissolved in 12.5 mL of pure water, and 1.36 g of ZnCl2 was ultrasonically dissolved in 12.5 mL of ethylene glycol. The K2CrO4 solution was then added dropwise to the ZnCl2 solution, stirred at room temperature for 30 min, transferred to a polytetrafluoroethylene liner, and subjected to a solvothermal reaction in a reactor at 150 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature, and the precipitate was collected by centrifugation, washed several times with ethanol and ultrapure water, and dried in an oven at 60 °C for 12 h. Finally, the obtained solid was placed in a tube furnace and calcined in air at a rate of 5 °C / min to 600 °C for 2 h to obtain ZnCr2O4 nanoparticles.

[0099] (2) The ZnCr2O4 nanoparticles (23 mg), 384 mg of Cd(NO3)2·4H2O, 284 mg of thiourea, and 10 mL of ethylenediamine described in step (1) were added to a polytetrafluoroethylene liner and stirred for 30 min to form a uniform suspension. Then, a solvothermal reaction was carried out in a reactor at 180 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the bright yellow precipitate was collected by centrifugation. It was washed several times with ethanol and ultrapure water and dried in an oven at 60 °C for 12 h to obtain the CdS / ZnCr2O4 photocatalyst.

[0100] The CdS / ZnCr2O4 photocatalyst obtained in this example was used for the aldehyde oxidation amidation reaction. The specific steps are as follows:

[0101] 26 mg of 4-cyanobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF) and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under light source (40 W blue LED) for 14 h. After the reaction was completed, 4-(pyrrolidine-1-carbonyl)benzonitrile (3a) was obtained by column chromatography with a yield of 59% (see Table 1).

[0102] Example 3

[0103] (1) 3.88 g of K2CrO4 was ultrasonically dissolved in 12.5 mL of pure water, and 1.36 g of ZnCl2 was ultrasonically dissolved in 12.5 mL of ethylene glycol. The K2CrO4 solution was then added dropwise to the ZnCl2 solution, stirred at room temperature for 30 min, transferred to a polytetrafluoroethylene liner, and subjected to a solvothermal reaction in a reactor at 150 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature, and the precipitate was collected by centrifugation, washed several times with ethanol and ultrapure water, and dried in an oven at 60 °C for 12 h. Finally, the obtained solid was placed in a tube furnace and calcined in air at a rate of 5 °C / min to 600 °C for 2 h to obtain ZnCr2O4 nanoparticles.

[0104] (2) The ZnCr2O4 nanoparticles (46 mg), 384 mg of Cd(NO3)2·4H2O, 284 mg of thiourea, and 10 mL of ethylenediamine described in step (1) were added to a polytetrafluoroethylene liner and stirred for 30 min to form a uniform suspension. Then, a solvothermal reaction was carried out in a reactor at 180 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the bright yellow precipitate was collected by centrifugation. It was washed several times with ethanol and ultrapure water and dried in an oven at 60 °C for 12 h to obtain the CdS / ZnCr2O4 photocatalyst.

[0105] The CdS / ZnCr2O4 photocatalyst obtained in this example was used for the aldehyde oxidation amidation reaction. The specific steps are as follows:

[0106] 26 mg of 4-cyanobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF) and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under light source (40 W blue LED) for 14 h. After the reaction was completed, 4-(pyrrolidine-1-carbonyl)benzonitrile (3a) was obtained by column chromatography with a yield of 85% (see Table 1).

[0107] Example 4

[0108] (1) 3.88 g of K2CrO4 was ultrasonically dissolved in 12.5 mL of pure water, and 1.36 g of ZnCl2 was ultrasonically dissolved in 12.5 mL of ethylene glycol. The K2CrO4 solution was then added dropwise to the ZnCl2 solution, stirred at room temperature for 30 min, transferred to a polytetrafluoroethylene liner, and subjected to a solvothermal reaction in a reactor at 150 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature, and the precipitate was collected by centrifugation, washed several times with ethanol and ultrapure water, and dried in an oven at 60 °C for 12 h. Finally, the obtained solid was placed in a tube furnace and calcined in air at a rate of 5 °C / min to 600 °C for 2 h to obtain ZnCr2O4 nanoparticles.

[0109] (2) The ZnCr2O4 nanoparticles (93 mg), 384 mg of Cd(NO3)2·4H2O, 284 mg of thiourea, and 10 mL of ethylenediamine described in step (1) were added to a polytetrafluoroethylene liner and stirred for 30 min to form a uniform suspension. Then, a solvothermal reaction was carried out in a reactor at 180 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the bright yellow precipitate was collected by centrifugation. It was washed several times with ethanol and ultrapure water and dried in an oven at 60 °C for 12 h to obtain the CdS / ZnCr2O4 photocatalyst.

[0110] The CdS / ZnCr2O4 photocatalyst obtained in this example was used for the aldehyde oxidation amidation reaction. The specific steps are as follows:

[0111] 26 mg of 4-cyanobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF) and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under light source (40 W blue LED) for 14 h. After the reaction was completed, 4-(pyrrolidine-1-carbonyl)benzonitrile (3a) was obtained by column chromatography with a yield of 93% (see Table 1).

[0112] Example 5

[0113] (1) 3.88 g of K2CrO4 was ultrasonically dissolved in 12.5 mL of pure water, and 1.36 g of ZnCl2 was ultrasonically dissolved in 12.5 mL of ethylene glycol. The K2CrO4 solution was then added dropwise to the ZnCl2 solution, stirred at room temperature for 30 min, transferred to a polytetrafluoroethylene liner, and subjected to a solvothermal reaction in a reactor at 150 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature, and the precipitate was collected by centrifugation, washed several times with ethanol and ultrapure water, and dried in an oven at 60 °C for 12 h. Finally, the obtained solid was placed in a tube furnace and calcined in air at a rate of 5 °C / min to 600 °C for 2 h to obtain ZnCr2O4 nanoparticles.

[0114] (2) The ZnCr2O4 nanoparticles (116 mg), 384 mg of Cd(NO3)2·4H2O, 284 mg of thiourea, and 10 mL of ethylenediamine described in step (1) were added to a polytetrafluoroethylene liner and stirred for 30 min to form a uniform suspension. Then, a solvothermal reaction was carried out in a reactor at 180 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the bright yellow precipitate was collected by centrifugation. It was washed several times with ethanol and ultrapure water and dried in an oven at 60 °C for 12 h to obtain the CdS / ZnCr2O4 photocatalyst.

[0115] The CdS / ZnCr2O4 photocatalyst obtained in this example was used for the aldehyde oxidation amidation reaction. The specific steps are as follows:

[0116] 26 mg of 4-cyanobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF) and 4 mg of CdS / ZnCr2O4 photocatalyst were added to a flask and reacted under light source (40 W blue LED) for 14 h. After the reaction was completed, 4-(pyrrolidine-1-carbonyl)benzonitrile (3a) was obtained by column chromatography with a yield of 80% (see Table 1).

[0117] Example 6

[0118] (1) 3.88 g of K2CrO4 was ultrasonically dissolved in 12.5 mL of pure water, and 1.36 g of ZnCl2 was ultrasonically dissolved in 12.5 mL of ethylene glycol. The K2CrO4 solution was then added dropwise to the ZnCl2 solution, stirred at room temperature for 30 min, transferred to a polytetrafluoroethylene liner, and subjected to a solvothermal reaction in a reactor at 150 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature, and the precipitate was collected by centrifugation, washed several times with ethanol and ultrapure water, and dried in an oven at 60 °C for 12 h. Finally, the obtained solid was placed in a tube furnace and calcined in air at a rate of 5 °C / min to 600 °C for 2 h to obtain the ZnCr2O4 photocatalyst.

[0119] The ZnCr2O4 photocatalyst obtained in this example was used for the aldehyde oxidation amidation reaction. Specific steps included:

[0120] 26 mg of 4-cyanobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF) and 4 mg of ZnCr2O4 photocatalyst were added to a flask and reacted under light source (40 W blue LED) for 14 h. After the reaction was completed, 4-(pyrrolidine-1-carbonyl)benzonitrile (3a) was obtained by column chromatography with a yield of 20% (see Table 1).

[0121] Example 7

[0122] (1) 384 mg of Cd(NO3)2·4H2O, 284 mg of thiourea, and 10 mL of ethylenediamine were added to a polytetrafluoroethylene liner and stirred for 30 min to form a uniform suspension. Then, a solvothermal reaction was carried out in a reactor at 180 °C for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The bright yellow precipitate was collected by centrifugation, washed several times with ethanol and ultrapure water, and dried in an oven at 60 °C for 12 h to obtain the CdS photocatalyst.

[0123] The CdS photocatalyst obtained in this embodiment was used in the aldehyde oxidation amidation reaction. The specific steps are as follows:

[0124] 26 mg of 4-cyanobenzaldehyde, 50 μL of pyrrolidine, 2 mL of tetrahydrofuran (THF) and 4 mg of CdS photocatalyst were added to a flask and reacted under light source (40 W blue LED) for 14 h. After the reaction was completed, 4-(pyrrolidine-1-carbonyl)benzonitrile (3a) was obtained by column chromatography with a yield of 38% (see Table 1).

[0125] Table 1

[0126]

[0127]

[0128] Standard conditions: 4-cyanobenzaldehyde (0.2 mmol), pyrrolidine (0.6 mmol), rt, 14 h, air, blue LED, NMR yield.

[0129] It can be seen that, under the same conditions, the CdS / ZnCr2O4 prepared in Example 1 has the best catalytic effect, proving that the present invention synthesizes a photocatalyst that can efficiently realize the oxidation and amidation of aldehydes.

[0130] The above embodiments are only used to explain the present invention and are not intended to limit the present invention in any way. Any simplifications, modifications, substitutions, and combinations made by those skilled in the art to the above embodiments based on the spirit and technical principles of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A CdS / ZnCr2O4 photocatalyst, characterized in that, The CdS / ZnCr2O4 photocatalyst is a binary composite material composed of CdS nanorods and ZnCr2O4 nanoparticles, wherein the ZnCr2O4 nanoparticles are on the surface of the CdS nanorods.

2. The preparation method of the CdS / ZnCr2O4 photocatalyst according to claim 1, characterized in that, Includes the following steps: (1) Cr 6+ Source, Zn 2+ The source, water and ethylene glycol are mixed and stirred to form a dispersion, which is then subjected to a solvothermal reaction. After the reaction is completed, the mixture is washed, dried and then calcined at high temperature to obtain ZnCr2O4 nanoparticles. (2) The ZnCr2O4 nanoparticles and Cd prepared in step (1) are added to the substrate. 2+ The source, thiourea and ethylenediamine were mixed and stirred to form a dispersion, and a solvothermal reaction was carried out. After the reaction was completed, the mixture was washed and dried to obtain the CdS / ZnCr2O4 photocatalyst.

3. The preparation method according to claim 2, characterized in that, The Cr mentioned in step (1) 6+ Source, Zn 2+ The dispersion formed by mixing and stirring Cr, water, and ethylene glycol refers to: 6+ The source is dissolved in water and added dropwise to a solution containing Zn. 2+ In the source of ethylene glycol; The Cr mentioned in step (1) 6+ Cr in the source 6+ and Zn 2+ Zn in the source 2+ The molar ratio is 3-1:3-1; The volume ratio of water to ethylene glycol in step (1) is 2-20:2-20; The Cr mentioned in step (1) 6+ The mass-to-volume ratio of the source and water is 2-5g: 2-20mL; The stirring time in step (1) is 10-60 min; The temperature of the solvothermal reaction in step (1) is 100-200℃, and the reaction time is 12-36h; The Cr mentioned in step (1) 6+ The source is K2Cr2O7 or K2CrO4; the Zn 2+ The source is ZnCl2; The high-temperature calcination mentioned in step (1) refers to calcination in air; The heating rate of the high-temperature calcination in step (1) is 2-10℃ / min; the temperature of the high-temperature calcination is 400-700℃; and the high-temperature calcination time is 1-6h.

4. The preparation method according to claim 2, characterized in that, The ZnCr2O4 nanoparticles and Cd mentioned in step (2) 2+ Cd in the source 2+ The dosage ratio of thiourea to thiourea is 10-150 mg: 0.1-2 mmol: 200-500 mg; The ethylenediamine and Cd mentioned in step (2) 2+ The volume-to-mass ratio of the source is 5-25 mL: 0.2-1 g; The stirring time in step (2) is 10-60 min; The temperature of the solvothermal reaction in step (2) is 100-200℃, and the reaction time is 12-36h; The Cd mentioned in step (2) 2+ The source is Cd(NO3)2·4H2O.

5. The preparation method according to claim 2, characterized in that, The drying in steps (1) and (2) is carried out at 40-100℃, using an oven or vacuum drying method, for a drying time of more than 6 hours; the washing method is to wash with ultrapure water 3-5 times and ethanol 3-5 times.

6. The application of the CdS / ZnCr2O4 photocatalyst according to claim 1 in photocatalytic organic reactions.

7. The application according to claim 6, characterized in that, The photocatalytic organic reaction is a photocatalytic aldehyde oxidation and amidation reaction; the photocatalytic organic reaction is carried out under light irradiation.

8. The application according to claim 7, characterized in that, The CdS / ZnCr2O4 photocatalyst is used for the photocatalytic oxidation and amidation of aldehydes, including the following steps: Compound 1, compound 2 and CdS / ZnCr2O4 photocatalyst were dissolved in a solvent and subjected to an aldehyde oxidation-amidation reaction under light irradiation to obtain compound 3; The general reaction formula is: Among them, R 1 Selected from substituted or unsubstituted aryl groups, and substituted or unsubstituted heteroaryl groups; R 2 R 3 Each is independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or R 2 R 3 Together with nitrogen atoms, they form substituted or unsubstituted nitrogen-containing heterocyclic alkyl groups.

9. The application according to claim 8, characterized in that, The substituents in the substituted alkyl, substituted alkoxy, substituted cycloalkyl, substituted heterocycloalkyl, substituted aryl, substituted heteroaryl, and substituted nitrogen-containing heterocycloalkyl groups are one or more of hydrogen, cyano, nitro, halogen, alkyl, and alkoxy groups; the alkyl group in the substituted or unsubstituted alkyl group has 1-10 carbon atoms, the alkoxy group in the substituted or unsubstituted alkoxy group has 1-10 carbon atoms, the cycloalkyl group in the substituted or unsubstituted cycloalkyl group has 3-10 carbon atoms, the total number of carbon atoms and heteroatoms of the heterocycloalkyl group in the substituted or unsubstituted heterocycloalkyl group has 3-10, the aryl group in the substituted or unsubstituted aryl group has 6-12 carbon atoms, the total number of carbon atoms and heteroatoms of the heteroaryl group in the substituted or unsubstituted heteroaryl group has 6-12, and the total number of carbon atoms and heteroatoms of the nitrogen-containing heterocycloalkyl group in the substituted or unsubstituted nitrogen-containing heterocycloalkyl group has 3-10.

10. The application according to claim 8, characterized in that, The illumination is visible light; the conditions for the aldehyde oxidation-amidation reaction include: air or oxygen; the aldehyde oxidation-amidation reaction is carried out at room temperature; The solvent is one or more of water, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, and dioxane, and the volume molar ratio of the solvent to compound 1 is 5-15 mL / mmol. The dosage of the CdS / ZnCr2O4 photocatalyst and the molar ratio of compound 1 are 5-35 mg / mmol; the molar ratio of compound 1 to compound 2 is 1-5:1-5.

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