Helical body MOC material photocatalyst and preparation method and application thereof

Abstract

The application discloses a preparation method and application of a spiro compound MOC material photocatalyst, which is a compound with a structural general formula (I). The compound is a photocatalyst capable of degrading dyes, tetracyclines and reduced hexavalent chromium under visible light, the catalyst is easy to separate from a solution, and has good structural stability and reusability.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of metal-organic cages (MOCs) and application of the material in the field of photocatalytic treatment of wastewater. BACKGROUND

[0002] Metal-organic cages (MOCs) are a kind of discrete supramolecular assemblies formed by the self-assembly of metal ions or clusters and organic ligands driven by coordination. They have specific sizes and cavities. MOCs have a clear molecular structure, usually composed of metal centers and organic ligands. The metal centers are connected to the organic ligands through coordination bonds, forming a cage-like structure with specific shape and size. Chemists such as Jonathan R. Nitschke have successively reported MOC materials with sandwiched layered, cubic, tetrahedral, octahedral, and icosahedral structures, many of which have cavities with different sizes and shapes. MOC materials have unique advantages in different fields due to their cavity structure and dynamic functional sites. In the adsorption field, MOCs can achieve selective separation and capture of specific molecules by customizing cavity size and functional sites. In the catalysis and transport field, their dynamic sites can effectively catalyze organic reactions. With the designability of structure and high specific surface area, MOCs can also be used as drug carriers for targeted delivery or achieve molecular selective transport in membrane separation, showing the development prospects of this material in the fields of biomedicine, gas separation, and environmental governance.

[0003] Dye wastewater mainly comes from dye production and processing industries. It is a difficult problem in wastewater treatment due to its complex composition, high colority, large discharge volume, and poor natural degradability. The main sources of chromium-containing wastewater include metallurgy, electroplating, leather tanning, and metal processing industries. The main component is hexavalent chromium (Cr(VI)). Cr(VI) is a highly toxic and carcinogenic substance that can cause respiratory, lung, and skin diseases, affect the immune and hematopoietic systems, and cause great harm to human health and the environment. Tetracycline, as a widely used antibiotic, has caused serious environmental pollution and public health problems due to improper use. The presence of tetracycline can lead to the gradual development of bacterial resistance. Aquatic organisms exposed to tetracycline can disrupt the balance of aquatic ecosystems. At the same time, humans may also ingest tetracycline through drinking contaminated water sources or through the food chain, posing a serious threat to human health.

[0004] In view of these wastewater pollution problems, researchers have developed various treatment methods, including physical methods (such as membrane filtration and physical adsorption), chemical methods (such as ozone oxidation and chlorination treatment), and biological methods (through microbial degradation). However, each of these methods has certain limitations, and photocatalytic degradation, as an emerging water treatment technology, has received widespread attention. Photocatalysts can efficiently and rapidly degrade dyes, tetracyclines, and Cr(VI) into harmless or low-toxicity substances under ultraviolet or visible light irradiation. Photocatalytic degradation has high treatment efficiency, is environmentally friendly, has a wide variety of photocatalytic materials, and flexible operating conditions, making it widely applicable in dealing with different water qualities and pollution levels.

[0005] However, photocatalytic degradation technology still faces many problems: low catalytic efficiency, narrow spectral response range, some catalysts are prone to photocorrosion under light, poor catalyst stability, and low recycling rate. Literature search found that MOC materials have not been reported in the field of photocatalytic treatment of wastewater, and are still blank. The present application aims to expand the application of MOC materials in the field of photocatalysis by designing and optimizing the structure of MOC materials, and to develop a MOC material with good performance in catalytic degradation of dyes, tetracyclines and reduction of Cr(VI) under visible light. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a helical MOC material photocatalyst.

[0007] Another object of the present application is to provide a preparation method of the above-mentioned helical MOC material and the application of the material in photocatalytic treatment of wastewater.

[0008] The technical solutions of the present application are as follows:

[0009] A helical MOC material is created, and the structure is shown in general formula (I):

[0010]

[0011] wherein M 2+ each independently is Zn 2+ , Fe 2+ .

[0012] A preparation method of the compound of general formula (I) according to claim 1. 2,7-Di(4-nitrophenoxyl)naphthalene is prepared from 2,7-naphthalenediol and p-chloronitrobenzene, and 4,4'-(naphthalene-2,7-diylbisoxo)dianiline is obtained by reduction with iron powder; helical MOC material (I) is synthesized by self-assembly from 4,4'-(naphthalene-2,7-diylbisoxo)dianiline, zinc triflate (ferrous triflate) and pyridine-2-carboxaldehyde. The reaction process is as follows:

[0013]

[0014]

[0015] wherein M 2+ each independently is Zn 2+ , Fe 2+ .

[0016] The conditions in reaction (3) are as follows: the reaction solvent can be acetonitrile, methanol or pyridine, preferably acetonitrile; and the reaction temperature can be 30-70°C, preferably 50°C.

[0017] The compound Zn2L3 helix MOC material and the Fe2L3 helix MOC material of the application can be used for photocatalytic degradation of wastewater.

[0018] The Zn2L3 helix MOC material prepared above has degradation rates of 75.6%, 66.4% and 83.9% for photocatalytic degradation of methyl orange, rhodamine B and reactive blue KN-B dye wastewater under LED light, respectively. After optimization of the degradation process, the degradation rate of methyl orange remains above 80% after 5 cycles, and the degradation rates of rhodamine B and reactive blue KN-B dye wastewater remain above 70% after 4 cycles. The degradation rate of tetracycline wastewater is 80.45%, and the degradation rate remains above 75% after 5 cycles. The reduction rate of Cr(VI) is 52.3%, and the reduction rate remains above 70% after 5 cycles after optimization of the reduction process. The comparison of nuclear magnetic resonance hydrogen spectra before and after photocatalytic treatment of the wastewater shows that the Zn2L3 helix MOC material has excellent structural stability and reusability.

[0019] The Fe2L3 helix MOC material prepared above has degradation rates of 89.84%, 71.32% and 87.83% for photocatalytic degradation of methyl orange, rhodamine B and reactive blue KN-B dye wastewater under LED light, respectively. The degradation rate of methyl orange is 82% after 7 cycles, the degradation rate of rhodamine B is above 63% after 4 cycles, and the degradation rate of reactive blue KN-B is above 83% after 5 cycles. The degradation rate of tetracycline wastewater is 71.6%, and the degradation rate remains above 65% after 5 cycles. The comparison of nuclear magnetic resonance hydrogen spectra before and after photocatalytic treatment of the wastewater shows that the structure of the Fe2L3 helix MOC material is consistent before and after the reaction, further confirming its excellent stability and reusability. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Nuclear magnetic hydrogen spectrum of Zn3L2 MOC material.

[0021] Figure 2High resolution mass spectrum of Zn3L2MOC material.

[0022] Figure 3 Selection of light source for photocatalytic degradation of each dye wastewater by Zn2L3MOC material.

[0023] Figure 4 Circulation performance of photocatalytic degradation of each dye wastewater by Zn2L3MOC material.

[0024] Figure 5 NMR hydrogen spectrum of each dye wastewater before and after photocatalytic circulation degradation by Zn2L3MOC material. (a) is before circulation degradation; (b) is after circulation degradation.

[0025] Figure 6 Photocatalytic degradation of tetracycline wastewater by Zn2L3MOC material.

[0026] Figure 7 Circulation performance of photocatalytic degradation of tetracycline by Zn2L3MOC material.

[0027] Figure 8 NMR hydrogen spectrum of tetracycline before and after photocatalytic circulation degradation by Zn2L3MOC material. (a) is before circulation degradation; (b) is after circulation degradation.

[0028] Figure 9 Selection of light source for photocatalytic reduction of Cr(VI) by Zn2L3MOC material.

[0029] Figure 10 Circulation performance of photocatalytic reduction of Cr(VI) by Zn2L3MOC material.

[0030] Figure 11 NMR hydrogen spectrum of Cr(VI) before and after photocatalytic circulation reduction by Zn2L3MOC material. (a) is before circulation reduction; (b) is after circulation reduction.

[0031] Figure 12 NMR hydrogen spectrum of Fe2L3MOC material.

[0032] Figure 13 High resolution mass spectrum of Fe2L3MOC material.

[0033] Figure 14 Structure ellipsoid diagram of Fe2L3MOC material.

[0034] Figure 15 Cell packing diagram of Fe2L3MOC material (containing four helices).

[0035] Figure 16 Selection of light source for photocatalytic degradation of each dye wastewater by Zn2L3MOC material.

[0036] Figure 17 Cycling performance of Fe2L3MOC material for photocatalytic degradation of each dye wastewater.

[0037] Figure 18 NMR of Fe2L3MOC material before and after photocatalytic cycling degradation of each dye wastewater. (a) before cycling degradation; (b) after cycling degradation.

[0038] Figure 19 Photocatalytic degradation of tetracycline wastewater by Fe2L3MOC material.

[0039] Figure 20 Cycling performance of Fe2L3MOC material for photocatalytic degradation of tetracycline.

[0040] Figure 21 NMR of Fe2L3MOC material before and after photocatalytic cycling degradation of tetracycline. (a) before cycling degradation; (b) after cycling degradation. DETAILED DESCRIPTION

[0041] Example 1

[0042] This example illustrates the preparation of 4,4'-(naphthalene-2,7-diylbis(oxy))diphenylamine

[0043] Into a 50 mL three-necked flask, 2,7-naphthalenediol 1.6 g (10 mmol), anhydrous potassium carbonate 3 g (22 mmol), 5 mL of toluene and 20 mL of DMF were added in sequence. The reaction was heated, stirred and refluxed. 3.5 g (22 mmol) of p-chloronitrobenzene was added and the refluxing reaction was continued for 8 h. After the reaction was completed, the mixture was cooled to 70 °C and filtered. The filtrate was cooled, allowed to stand, filtered, washed and dried to obtain 2,7-bis(4-nitrophenoxy)naphthalene 2.01 g, yield: 47%, melting point: 178-181 °C. 1 H NMR (400 MHz, CD3CN): 8.26 (d, J = 2.4 Hz, 1H, benzene-H), 7.97 (d, J = 8.8 Hz, 1H, benzene-H), 7.45 (d, J = 2.3 Hz, 1H, benzene-H), 7.28 (d, J = 2.3 Hz, 1H, benzene-H), 7.12 (d, J = 2.4 Hz, 1H, benzene-H).

[0044] Into a 50 mL flask, 0.402 g (1.0 mmol) of 2,7-di(4-nitrophenoxy)naphthalene, 0.82 g (15 mmol) of ammonium chloride, 15 mL of ethanol and 5 mL of water were added successively, and the reaction was stirred at 80°C. 0.81 g (15 mmol) of 100-mesh high-activity iron powder was added in three portions, and the reaction was continued for 5 h under reflux. After the reaction was completed, the filtrate was washed with hot ethanol, and the filtrate was adjusted to pH 9 with sodium bicarbonate, filtered, and desolvated. The obtained crude product was dried, dissolved in 0.5 mol / L hydrochloric acid, filtered, and the filtrate was adjusted to pH 7 with 5% sodium hydroxide solution, filtered, and washed with water to obtain off-white 4,4'-(naphthalene-2,7-diylbis(oxy))diphenylamine 0.157 g in a yield of 43%, and the melting point was 167-168°C. 1 H NMR (400 MHz, CD3CN): 7.81 (d, J = 8.9 Hz, 1H, benzene-H), 7.06 (d, J = 8.6 Hz, 1H, benzene-H), 6.94 (s, 1H, benzene-H), 6.79 (d, J = 8.6 Hz, 1H, benzene-H), 6.60 (d, J = 8.2 Hz, 1H, benzene-H), 4.99 (s, 2H, amino-H). IR (KBr pellet), cm -1 : 3415, 1632, 1498, 1227, 1156, 839.

[0045] Example 2

[0046] This example illustrates the preparation of a Zn2L3spiro MOC material

[0047] Into a 10 mL flask, 19.52 mg (0.057 mmol) of 4,4'-(naphthalene-2,7-diylbis(oxy))diphenylamine, 13.81 mg (0.038 mmol) of zinc triflate, and 12.21 mg (0.114 mmol) of pyridine-2-carboxaldehyde were added successively, dissolved in 5 mL of acetonitrile, and reacted at 50°C for 14 h. After the reaction was completed, 15 mL of isopropyl ether was added to induce phase separation, and the product was separated by centrifugation and dried to obtain 20.87 mg of a brownish yellow solid. The yield was 48%, and the melting point was >300°C. Characterization data of the Zn2L3spiro MOC material Figure 1 、 Figure 2 ): 1H NMR (400 MHz, CD3CN): δ 8.71 (s, 1H), 8.50 (m, 1H), 8.32 (d, J = 7.6 Hz, 1H), 7.95 (s, 1H), 7.92 (d, J = 5.1 Hz, 1H), 7.69 (s, 1H), 7.11 (d, J = 8.6 Hz, 2H), 6.63 (dd, J = 9.0, 1.8 Hz, 1H), 6.41 (d, J = 8.6 Hz, 2H), 6.32 (d, J = 8.9 Hz, 1H). HRMS (ESI): m / z = 423.10483 [Zn2L3] 4+ , 613.79175 [Zn2L3] 4+ [OTf] - , 995.66180 [Zn2L3] 4+ 2[OTf] - .

[0048] Example 3

[0049] This example illustrates the photocatalytic degradation of dye wastewater performance of Zn2L3 helical MOC material

[0050] Pre-treatment work before photocatalytic degradation: methyl orange dye solution was prepared with a concentration of 10 mg / L; rhodamine B dye solution was prepared with a concentration of 20 mg / L; reactive blue KN-B dye solution was prepared with a concentration of 20 mg / L. The maximum absorption wavelength of the methyl orange dye solution was 464 nm, the maximum absorption wavelength of the rhodamine B dye solution was 540 nm, and the maximum absorption wavelength of the reactive blue KN-B dye solution was 596 nm, which were determined by a UV-visible spectrophotometer. The absorbance of the dye solution was measured by a UV-visible spectrophotometer before and after wastewater treatment. The degradation rate was calculated according to the following formula:

[0051]

[0052] wherein A0 is the initial absorbance of the simulated dye wastewater; A t is the absorbance of the simulated dye wastewater at a certain time, and DR represents the degradation rate of the simulated dye wastewater.

[0053] (1) Selection of light source for photocatalytic degradation

[0054] In a 150 mL reactor, 120 mL of simulated dye wastewater solution and 60 mg of Zn2L3 helical MOC material were added, and the mixture was stirred for 1 h in the dark to achieve adsorption-desorption equilibrium. Then the reactor was placed in a 25°C water bath and irradiated under stirring under different light sources (LED light, halogen light, and natural diffuse light). At certain time intervals, 1 mL of sample was taken and filtered through a 0.22 μm filter membrane, and the absorbance was measured by a UV-visible spectrophotometer. Finally, the DR degradation rate was calculated. The degradation rate was calculated according to the following formula: Figure 3Data shows that the Zn2L3 helicate MOC material only has adsorption effect on methyl orange dye wastewater under dark condition, and the dye concentration no longer changes after 40 min of adsorption-desorption equilibrium, with an adsorption rate of 14.8%; for rhodamine B, the adsorption-desorption equilibrium is reached within 60 min, with an adsorption rate of 13.2%; for reactive blue, the adsorption-desorption equilibrium is reached within 40 min, with an adsorption rate of 18.3%. Under LED light, the Zn2L3 helicate MOC material has a photocatalytic degradation rate of 75.6% on methyl orange within 2 h, a photocatalytic degradation rate of 66.4% on rhodamine B within 3 h, and a photocatalytic degradation rate of 83.9% on reactive blue within 2 h. The Zn2L3 helicate MOC material shows significant photocatalytic degradation effect on various dye wastewaters. Among various light sources, LED has the best photocatalytic degradation performance.

[0055] (2) Photocatalytic degradation cycle experiment

[0056] The degradation solution of the Zn2L3 helicate MOC material was centrifuged, and the obtained solid sample was washed with water three times to remove surface impurities. Then the MOC material was placed in an oven at 110°C for drying for 3 h. Under the same optimized degradation process conditions, a cycle photocatalytic degradation experiment was carried out to determine the degradation rate of the target dye. From the data Figure 4 Data shows that under LED light, the degradation rate of the Zn2L3 helicate MOC material on methyl orange remains above 80% after 5 cycles of degradation; for rhodamine B and reactive blue, the photocatalytic degradation rate remains above 70% after 4 cycles of degradation. After the degradation cycle experiment, the Zn2L3 helicate MOC material before and after the degradation of the dye solution was characterized by nuclear magnetic resonance and compared. Figure 5 Data shows that after multiple cycles of use, the hydrogen spectrum of the Zn2L3 helicate MOC material is basically the same as that of the original MOC material, indicating that the Zn2L3 helicate MOC material has good structural stability.

[0057] Example 4

[0058] This example illustrates the photocatalytic degradation performance of the Zn2L3 helicate MOC material on tetracycline wastewater

[0059] Pre-treatment work before photocatalytic degradation: tetracycline solution was prepared with a concentration of 20 mg / L. The maximum absorption wavelength of the tetracycline solution was determined by UV-visible spectrophotometry to be 378 nm. The absorbance of the tetracycline solution was measured by UV-visible spectrophotometry before and after wastewater treatment. The degradation rate was calculated according to the following formula:

[0060]

[0061] where A0 is the initial absorbance of the simulated tetracycline wastewater; A tis the absorbance of the simulated tetracycline wastewater at a certain moment, and DR represents the degradation rate of the simulated tetracycline wastewater.

[0062] (1) Selection of light source for photocatalytic degradation

[0063] In a 100 mL reactor, 40 mL of tetracycline solution (20 mg / L) and 50 mg of Zn2L3 helical MOC material were sequentially added, and stirring was carried out for 1 h in the dark to achieve adsorption-desorption equilibrium. Then the reactor was placed in a 25°C water bath and irradiated under an LED light source. At certain time intervals, 1 mL of sample was taken and filtered through a 0.22 μm filter membrane, and the absorbance was measured using a UV-visible spectrophotometer. Finally, the degradation rate DR was calculated. From Figure 6 As can be seen from the data, after 90 min of dark reaction, the adsorption rate of Zn2L3 helical MOC material for tetracycline was only 9.3%. However, under LED light, the degradation rate of Zn2L3 helical MOC material for tetracycline was 80.45%. This indicates that the material has a significant photocatalytic degradation effect on tetracycline.

[0064] (2) Photocatalytic degradation cycle experiment

[0065] The degradation solution of Zn2L3 helical MOC material was centrifuged, and the obtained solid sample was washed with water three times to remove surface impurities. Subsequently, the MOC material was placed in an oven at 110°C and dried for 3 h. Under the same conditions, a cycle photocatalytic degradation experiment was carried out to determine the degradation rate of tetracycline. From Figure 7 As can be seen from the data, under LED light, the degradation rate of Zn2L3 helical MOC material for tetracycline remained above 75% after five cycles. After the cycle degradation, the Zn2L3 helical MOC material was characterized by NMR. From Figure 8 As can be seen from the data, the hydrogen spectrum of Zn2L3 helical MOC material before and after recycling is basically the same, indicating that the material exhibits good structural stability and good reusability.

[0066] Example 5

[0067] This example illustrates the performance of Zn2L3 helical MOC material for photocatalytic reduction of Cr(VI) wastewater

[0068] Pre-treatment for photocatalytic reduction: prepare a Cr(VI) wastewater solution with a concentration of 10 mg / L; measure Cr(VI) by the diphenyl carbonyl hydrazine spectrophotometric method (HJ-908-2017, DPC method) with a maximum absorption wavelength of 554 nm. Measure the absorbance of Cr(VI) wastewater before and after wastewater treatment using a UV-visible spectrophotometer. Calculate the reduction rate according to the following formula:

[0069]

[0070] wherein A0is the initial absorbance of the simulated Cr(VI)-containing wastewater; A t is the absorbance of the simulated Cr(VI)-containing wastewater at a certain time, and RR represents the reduction rate of the simulated Cr(VI)-containing wastewater.

[0071] (1) Selection of photocatalytic reduction light source

[0072] In a 100 mL beaker, 50 mL of simulated Cr(VI)-containing wastewater solution (10 mg / L) and 100 mg of Zn2L3spiral MOC material were added, and the mixture was stirred continuously in the dark for 1 h to achieve adsorption-desorption equilibrium. Then the beaker was placed in a 25°C water bath and irradiated under stirring for 180 min under different light sources (LED light, halogen light, and natural diffuse light). At certain time intervals, 1 mL of the sample was taken, filtered through a 0.22 μm filter membrane, added with DPC for color development, and the absorbance was measured by a UV-visible spectrophotometer. Finally, the reduction rate RR was calculated. The results are shown in Table 1. Figure 9 As can be seen from the data, the Zn2L3spiral MOC material reached adsorption-desorption equilibrium for Cr(VI) after 60 min in the dark, and the adsorption rate was 16.9%. Under LED light, halogen light, and natural light, the reduction rates of the Zn2L3spiral MOC material for Cr(VI) wastewater solution were 52.3%, 45.5%, and 31.3%, respectively. It can be seen that the Zn2L3spiral MOC material has a significant photocatalytic reduction effect on Cr(VI). The LED light has the best effect.

[0073] (2) Photocatalytic reduction cycle experiment

[0074] The reduced solution of the Zn2L3spiral MOC material was subjected to centrifugal separation treatment, and the obtained solid sample was washed with water three times to remove surface impurities. Subsequently, the MOC material was placed in an oven at 110°C and dried for 3 h. Under the same optimized reduction process conditions, the reduction rate of the target Cr(VI) was measured after the photocatalytic cycle reduction experiment. The results are shown in Table 2. Figure 10 As can be seen from the data, under LED light, the reduction rate of the Zn2L3spiral MOC material for Cr(VI) remained at 70% after 5 cycles. After completion, the Zn2L3spiral MOC material after degradation of the dye solution was subjected to nuclear magnetic resonance characterization. Compared with the hydrogen spectrum of the original MOC material, according to the change of the hydrogen spectrum of the Zn2L3spiral MOC material before and after the cycle experiment, it can be seen that the hydrogen spectrum of the Zn2L3spiral MOC material after the cycle experiment is basically the same as that of the original MOC material, indicating that the material has good structural stability. Figure 11 The results show that the hydrogen spectrum of the Zn2L3spiral MOC material after multiple cycles is basically the same as that of the original MOC material, indicating that the material has good structural stability.

[0075] Example 6

[0076] This example illustrates the preparation of Fe2L3spiral MOC material

[0077] In a 10 mL flask, 19.08 mg (0.056 mmol) of 4,4'-(naphthalene-2,7-diylbis(oxy))diphenylamine, 13.15 mg (0.037 mmol) of ferrous triflate, pyridine-2-carboxaldehyde 12.00 mg (0.112 mmol) were added in turn, dissolved with 5 mL of acetonitrile, and reacted at 50 °C for 14 h. After the reaction was completed, 15 mL of isopropyl ether was added to force the separation, centrifuged, and dried to obtain 30.00 mg of purple solid. The yield was 70.8%, and the melting point was >300 °C. Characterization data of Fe2L3 helix MOC material Figure 12 、 Figure 13 ) : 1 H NMR (400 MHz, CD3CN): δ 8.88 (s, 1H), 8.56 (d, J = 7.2 Hz, 1H), 8.44 (t, J = 7.4 Hz, 1H), 7.80 (m, 1H), 7.67 (s, 1H), 7.45 (d, J = 5.1 Hz, 1H), 6.93 (m, 4H), 5.45 (s, 2H). HRMS (ESI): m / z = 418.35852 [Fe2L3] 4+ , 607.45917 [Fe2L3] 4+ [OTf] - , 985.66821 [Fe2L3] 4+ 2[OTf] - , 2120.28979 [Fe2L3] 4+ 3[OTf] - .

[0078] To further confirm the structure of the Fe2L3 helix MOC material, single crystal culture and crystal structure analysis were performed on the synthesized product. Prism-shaped purple crystals were cultured using the acetonitrile-isopropyl ether diffusion method. The crystals were washed with petroleum ether three times and dried in vacuum for 30 min for crystal structure testing. Suitable single crystals were selected, stuck on glass fibers, and placed on a BRUKER Apex II CCD single crystal diffractometer at room temperature. Mo Kα rays were monochromatized by a graphite monochromator and scanned within a certain θ range. The crystal structure of the Fe2L3 helix MOC material was solved by the direct method, and the coordinates of the non-hydrogen atoms and the anisotropic thermal temperature factors in the MOC material were corrected to convergence by the full matrix least squares method. The positions of all hydrogen atoms were obtained by the theoretical hydrogenation method. Structure analysis, calculation, correction, and drawing of single crystal molecular patterns were completed by SHELXTL PC and MERCURY. Single crystal X-ray structure showed that the MOC material was a three-helix metal-organic cage structure compound, belonging to the triclinic system, and the space group was P-1 (#2). The ellipsoid diagram and the crystal cell stacking diagram are as follows Figure 14 ,Figure 15 The main crystal structure parameters are shown in Table 1.

[0079] Table 1 Crystal structure parameters of Fe2L3 MOC material

[0080]

[0081] Example 7

[0082] This example illustrates the photocatalytic degradation performance of Fe2L3 helical MOC material on dye wastewater

[0083] The dye solution preparation and degradation rate determination method are consistent with Example 3.

[0084] (1) Selection of light source for photocatalytic degradation

[0085] In a 150 mL reactor, 5 mg of Fe2L3 helical MOC material and 100 mL of simulated dye wastewater solution were added, and stirring was continued in the dark for 1 h to reach adsorption-desorption equilibrium. Then the reactor was placed in a 25°C water bath and irradiated under stirring under different light sources (LED light, halogen light, natural diffuse light). At certain time intervals, 1 mL of sample was taken and filtered through a 0.22 μm filter membrane, and the absorbance was measured using a UV-visible spectrophotometer to calculate the DR degradation rate. From Figure 16 As can be seen from the data, the Fe2L3 helical MOC material and methyl orange dye solution reached adsorption-desorption equilibrium after 90 min of dark reaction, with an adsorption rate of 20.49%; for rhodamine B dye, adsorption-desorption equilibrium was achieved within 60 min, with an adsorption rate of 30.52%; and for reactive blue, adsorption-desorption equilibrium was achieved within 40 min, with an adsorption rate of 16.46%. Under LED light, the photocatalytic degradation rate of Fe2L3 helical MOC material on methyl orange was 89.84% within 3 h, on rhodamine B was 71.32% within 3 h, and on reactive blue was 87.83% within 2 h. It can be seen that the Fe2L3 helical MOC material has good photocatalytic degradation performance.

[0086] (2) Photocatalytic degradation cycle experiment

[0087] The Fe2L3 helical MOC material degradation solution was centrifuged, the solid sample was washed with water three times to remove surface impurities, and the MOC material was placed in an oven at 110°C for drying for 3 h. The cycle degradation experiment was carried out under the same conditions, and the degradation rate of the target dye was measured. From Figure 17Data shows that under LED light, the degradation rate of Fe2L3 helix MOC material on methyl orange is 82% after 7 cycles; the degradation rate of rhodamine B is more than 63% after 4 cycles; the degradation rate of reactive blue KN-B is more than 83% after 5 cycles. The Fe2L3 helix MOC material after degrading the dye solution is characterized by nuclear magnetic resonance, Figure 18 It can be seen that the hydrogen spectrum of Fe2L3 helix MOC material before and after multiple cycle degradation is basically the same, indicating that Fe2L3 helix MOC material has good structural stability.

[0088] Example 8

[0089] This example illustrates the performance of Fe2L3 helix MOC material in photocatalytic degradation of tetracycline wastewater

[0090] The preparation of tetracycline wastewater, the determination of degradation rate, etc. are consistent with Example 4.

[0091] (1) Selection of light source for photocatalytic degradation

[0092] In a 100 mL reactor, 40 mL of tetracycline solution (20 mg / L) and 50 mg of Fe2L3 helix material were added in turn, and stirred in the dark for 1 h to reach adsorption-desorption equilibrium. The sample was placed in a 25°C water bath, and the reactor was placed under LED light source for irradiation. At certain time intervals, 1 mL of sample was taken and filtered through a 0.22 μm filter membrane, and the absorbance was measured by ultraviolet-visible spectrophotometer to calculate the DR degradation rate. From Figure 19 Data shows that after 90 min in the dark, the adsorption rate of Fe2L3 helix MOC material on tetracycline is only 28.0%. Under LED light, the degradation rate of Fe2L3 helix MOC material on tetracycline wastewater can reach 71.6%. It can be seen that MOC material has good photocatalytic degradation effect on simulated tetracycline wastewater.

[0093] (2) Photocatalytic degradation cycle experiment

[0094] The photocatalytic cycle degradation experiment of MOC material was carried out under LED light. After the Fe2L3 helix MOC material in the degradation system was centrifuged and recovered, it was washed 3 times to remove the impurities on the surface of the MOC material, and then placed in an oven at 110°C for drying for 3 h. The cycle degradation experiment was carried out under the same conditions, and the degradation rate of tetracycline wastewater was measured. From Figure 20 Data shows that under LED light, the degradation rate of Fe2L3 helix MOC material on tetracycline remains more than 65% after 5 cycles. The Fe2L3 helix MOC material before and after the cycle is characterized by nuclear magnetic resonance, Figure 21 It is shown that the hydrogen spectrum of Fe2L3 helix MOC material before and after multiple cycle use is basically the same, indicating that the material has good structural stability and recyclable practicality.

Claims

1. A helical MOC material photocatalyst, having a structure as shown in general formula (I) : wherein M 2+ each independently is Zn 2+ , Fe 2+ . 2.A method for preparing a helical MOC material photocatalyst, comprising synthesizing 4,4'-(naphthalene-2,7-diylbisoxy) diphenylamine triflate and pyridine-2-carboxaldehyde through self-assembly, and the reaction process is as follows: wherein M 2+ each independently is Zn 2+ , Fe 2+ .

3. Use of the helical MOC material photocatalyst produced by the production process according to claim 2, characterized by: for photocatalytic degradation of dye wastewater, photocatalytic degradation of tetracycline wastewater, or photocatalytic reduction of Cr(VI) wastewater.

Images