Spiral MOC material photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a preparation method and application of a spiral MOC material photocatalyst. The spiral MOC material photocatalyst is a compound with a structural general formula (I). The compound is a photocatalyst capable of degrading dye and tetracycline and reducing hexavalent chromium under visible light, and the catalyst is easy to separate from a solution and has good structural stability and reusability. # imgabs0 #

Description

Technical Field

[0001] The invention relates to a preparation method of a metal-organic cage-shaped supramolecular material (Metal-organic cages, MOCs), and application of the material in the technical field of photocatalytic wastewater treatment. Background Art

[0002] Metal-organic cages (MOCs) supramolecular materials are a class of discrete supramolecular assemblies formed by coordination-driven self-assembly of metal ions or clusters with organic ligands, with specific sizes and cavities. Metal-organic cages have a clear molecular structure and are usually composed of a metal center and an organic ligand. The metal center and the organic ligand are connected by coordination bonds to form a cage structure with a specific shape and size. Jonathan R. Nitschke and other chemists have successively reported MOC materials with three-dimensional structures such as sandwich layers, cubes, tetrahedrons, octahedrons, and icosahedrons, most of which have cavity structures with different sizes and shapes. MOC materials have unique advantages in different fields due to their own cavity structure and dynamic functional sites. In the field of adsorption, MOC can achieve selective separation and capture of specific molecules by customizing the cavity size and functional sites. In the field of catalysis and transport, its dynamic sites can effectively catalyze organic reactions. With its structural designability and high specific surface area, MOC can also be used as a drug carrier to achieve targeted delivery or to achieve selective molecular transport through pore properties in membrane separation, reflecting the development prospects of this type of material in biomedicine, gas separation, environmental governance and other fields.

[0003] Dye wastewater mainly comes from the dye production and processing industry. It is characterized by complex composition, high chroma, large discharge volume and poor natural degradation, which has always been a difficult problem in wastewater treatment. The main sources of chromium-containing wastewater include metallurgy, electroplating, leather tanning and metal processing industries. Its main component is dichromate (Cr(VI)). Cr(VI) is a highly toxic and carcinogenic substance that can cause respiratory, lung and skin diseases, affect the immune system and hematopoietic system, and cause great harm to human health and the environment. Tetracycline is a widely used antibiotic, and its improper use has brought serious environmental pollution and public health problems. The presence of tetracycline can cause bacteria to gradually develop drug resistance. When aquatic organisms come into contact with tetracycline, it will affect the balance of the aquatic ecosystem. At the same time, humans may also ingest tetracycline by drinking contaminated water or through the food chain, which seriously threatens human health.

[0004] In response to these wastewater pollution problems, researchers have developed a variety of 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 extensive attention. Using photocatalysts under ultraviolet or visible light irradiation, dyes, tetracycline, and Cr(VI) can be efficiently and rapidly degraded into harmless substances or low-toxic substances. Photocatalytic degradation has high treatment efficiency, is environmentally friendly, has a variety of photocatalytic materials, and flexible operating conditions, making it widely applicable in dealing with different water qualities and pollution levels.

[0005] However, the photocatalytic degradation technology still faces many problems: low catalytic efficiency, narrow spectral response range, some catalysts are prone to photocorrosion under light irradiation, poor catalyst stability, low recycling rate, etc. Literature retrieval found that there is no report on the research of MOC materials in the field of photocatalytic wastewater treatment, which is still blank. The present invention intends to expand the application of this material in the field of photocatalysis through the structural design and functional optimization of MOC materials, and develop a MOC material with good performance in catalytic degradation of dyes, tetracycline, and reduction of Cr(VI) under visible light. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the invention aims to provide a helical MOC material photocatalyst.

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

[0008] The technical solution of the present invention is as follows:

[0009] Create a helical MOC material, the structure of which is shown in the 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) as described in claim 1. Using 2,7-naphthalenediol and p-chloronitrobenzene as raw materials to prepare 2,7-bis(4-nitrophenoxy)naphthalene, and obtaining 4,4'-(naphthalene-2,7-diyl dioxy)dianiline by reduction with iron powder; using 4,4'-(naphthalene-2,7-diyl dioxy)dianiline, zinc trifluoromethanesulfonate (iron trifluoromethanesulfonate) and pyridine-2-carboxaldehyde to synthesize the helical MOC material (I) through self-assembly. The reaction process is as follows:

[0013]

[0014]

[0015] Among them, M 2+ is independently Zn 2+ , Fe 2+ .

[0016] The conditions in reaction (3) are as follows: the reaction solvent can be acetonitrile, methanol, pyridine, preferably acetonitrile; the reaction temperature can be 30 - 70 °C, preferably 50 °C. The present invention adopts a self-assembly synthesis method to directly obtain the target complex in one-step reaction, with high reaction yield and strong reproducibility.

[0017] The compound Zn 2 L 3 helical MOC material and Fe 2 L 3 helical MOC material of the present invention can be used for photocatalytic degradation of wastewater.

[0018] For the above-prepared Zn 2 L 3 helical MOC material under LED light, the degradation rates of methyl orange, rhodamine B, and reactive blue KN - B dye wastewater are 75.6%, 66.4%, and 83.9% respectively. After optimizing the degradation process conditions, 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 by photocatalysis is 80.45%, and the degradation rate remains above 75% after 5 cycles; the reduction rate of photocatalytic reduction of Cr(VI) is 52.3%, and after optimizing the reduction process conditions, the reduction rate can remain above 70% after 5 cycles. The comparison of the nuclear magnetic resonance hydrogen spectrum before and after photocatalytic treatment of each wastewater shows that the Zn2L 3 helical MOC material has excellent structural stability and reusability.

[0019] For the above-prepared Fe 2 L 3 helical MOC material under LED light, the degradation rates of methyl orange, rhodamine B, and reactive blue KN - B dye wastewater are 89.84%, 71.32%, and 87.83% 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 by photocatalysis is 71.6%, and the degradation rate can remain above 65% after 5 cycles. The comparison of the nuclear magnetic resonance hydrogen spectrum before and after photocatalytic treatment of wastewater shows that Fe 2 L 3The structure of the spiro MOC material remains consistent before and after the reaction, further confirming its excellent stability and reusability. Description of the Drawings

[0020] Figure 1 Zn 3 L 2 1H NMR spectrum of the MOC material.

[0021] Figure 2 Zn 3 L 2 High-resolution mass spectrum of the MOC material.

[0022] Figure 3 Zn 2 L 3 Selection of the light source for photocatalytic degradation of various dye wastewaters by the MOC material.

[0023] Figure 4 Zn 2 L 3 Recycling performance of the MOC material for photocatalytic degradation of various dye wastewaters.

[0024] Figure 5 Zn 2 L 3 1H NMR spectra of the MOC material before and after photocatalytic cyclic degradation of various dye wastewaters. (a) Before cyclic degradation; (b) After cyclic degradation.

[0025] Figure 6 Zn 2 L 3 Photocatalytic degradation of tetracycline wastewater by the MOC material.

[0026] Figure 7 Zn 2 L 3 Recycling performance of the MOC material for photocatalytic cyclic degradation of tetracycline.

[0027] Figure 8 Zn 2 L 3 Comparison of 1H NMR spectra of the MOC material before and after photocatalytic cyclic degradation of tetracycline. (a) Before cyclic degradation; (b) After cyclic degradation.

[0028] Figure 9 Zn 2 L 3 Selection of the light source for photocatalytic reduction of Cr(VI) by the MOC material.

[0029] Figure 10 Zn 2 L 3 Recycling performance of the MOC material for photocatalytic reduction of Cr(VI).

[0030] Figure 11 Zn 2 L 3 1H NMR spectra of MOC material before and after photocatalytic cyclic reduction of Cr(VI). (a) Before cyclic reduction; (b) After cyclic reduction.

[0031] Figure 12 Fe 2 L 3 1H NMR spectra of MOC material.

[0032] Figure 13 Fe 2 L 3 High-resolution mass spectrum of MOC material.

[0033] Figure 14 Fe 2 L 3 Ellipsoid diagram of MOC material structure.

[0034] Figure 15 Fe 2 L 3 Unit cell packing diagram of MOC material (including four helices).

[0035] Figure 16 Fe 2 L 3 Selection of light sources for photocatalytic degradation of various dye wastewaters by MOC material.

[0036] Figure 17 Fe 2 L 3 Cyclic performance of photocatalytic degradation of various dye wastewaters by MOC material.

[0037] Figure 18 Fe 2 L 3 1H NMR spectra of MOC material before and after photocatalytic cyclic degradation of various dye wastewaters. (a) Before cyclic degradation; (b) After cyclic degradation.

[0038] Figure 19 Fe 2 L 3 Photocatalytic degradation of tetracycline wastewater by MOC material.

[0039] Figure 20 Fe 2 L 3 Cyclic performance of photocatalytic degradation of tetracycline by MOC material.

[0040] Figure 21 Fe 2 L 3 Comparison of 1H NMR spectra of MOC material before and after photocatalytic cyclic degradation of tetracycline. (a) Before cyclic degradation; (b) After cyclic degradation. Detailed implementation mode

[0041] Example 1

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

[0043] 1.6 g (10 mmol) of 2,7-naphthalenediol, 3 g (22 mmol) of anhydrous potassium carbonate, 5 mL of toluene and 20 mL of DMF were successively added to a 50 mL three-necked flask. Heat, stir and reflux the reaction. Add 3.5 g (22 mmol) of p-chloronitrobenzene and continue refluxing for 8 h. After the reaction is completed, cool to 70 °C and filter by suction. After the filtrate is cooled, allowed to stand, filtered by suction, washed and dried, 2.01 g of 2,7-bis(4-nitrophenoxy)naphthalene is obtained, with a yield of 47% and a melting point of 178 - 181 °C. 1 H NMR (400 MHz, CD 3 CN): 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] 0.402 g (1.0 mmol) of 2,7-bis(4-nitrophenoxy)naphthalene, 0.82 g (15 mmol) of ammonium chloride, 15 mL of ethanol and 5 mL of water were successively added to a 50 mL flask, and the temperature was raised to 80 °C and stirred for reaction. 0.81 g (15 mmol) of 100-mesh highly active reduced iron powder was added in three portions, and the reflux reaction was continued for 5 h. After the reaction was completed, it was filtered while hot, and the filter cake was washed with hot ethanol. The obtained filtrate was adjusted to pH about 9 with sodium bicarbonate, filtered, desolvated, and the obtained crude product was dried and dissolved in 0.5 mol / L hydrochloric acid, filtered, and 5% sodium hydroxide solution was added to the filtrate to adjust the pH to about 7, filtered, washed with water, and 0.157 g of off-white 4,4'-(naphthalene-2,7-diyl dioxy)diphenylamine was obtained, with a yield of 43% and a melting point of 167 - 168 °C. 1 H NMR (400 MHz, CD 3 CN): 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 tablet), cm-1 : 3415, 1632, 1498, 1227, 1156, 839.

[0045] Example 2

[0046] This example illustrates Zn 2 L 3 Preparation of Spiro MOC Material

[0047] In a 10 mL flask, 19.52 mg (0.057 mmol) of 4,4′-(naphthalene-2,7-diyl dioxy)diphenylamine, 13.81 mg (0.038 mmol) of zinc trifluoromethanesulfonate, and 12.21 mg (0.114 mmol) of pyridine-2-carbaldehyde were added successively, dissolved in 5 mL of acetonitrile, and reacted at 50 °C for 14 h. After the reaction, 15 mL of isopropyl ether was added for precipitation, followed by centrifugation and drying to obtain 20.87 mg of a brownish-yellow solid. The yield was 48%, and the melting point > 300 °C. Zn 2 L 3 Characterization data of Spiro MOC material ( Figure 1 , Figure 2 ): 1 H NMR (400 MHz, CD 3 CN): 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 [Zn 2 L 3 4+ , 613.79175 [Zn 2 L 3 4+ [OTf] - , 995.66180 [Zn 2 L 3 4+ 2[OTf] - .

[0048] Example 3

[0049] This example illustrates the performance of Zn 2 L 3 Spiro MOC material in photocatalytic degradation of dye wastewater

[0050] ​​​Pretreatment for photocatalytic degradation: Prepare methyl orange dye solution with a concentration of 10 mg / L, rhodamine B dye solution with a concentration of 20 mg / L, and reactive blue KN-B dye solution with a concentration of 20 mg / L. Use a UV-visible spectrophotometer to measure the maximum absorption wavelengths of the methyl orange dye solution as 464 nm, the rhodamine B dye solution as 540 nm, and the reactive blue KN-B dye solution as 596 nm. Measure the absorbance of the dye solution with a UV-visible spectrophotometer before and after wastewater treatment. Calculate the degradation rate according to the following formula:

[0051]

[0052] where A 0 is the initial absorbance of the simulated dye wastewater; A t is the absorbance of the simulated dye wastewater at a certain moment, and DR represents the degradation rate of the simulated dye wastewater.

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

[0054] Add 120 mL of simulated dye wastewater solution and 60 mg of Zn 2 L 3 spiro MOC material into a 150 mL reactor, and continuously stir for 1 h under dark conditions to achieve adsorption-desorption equilibrium. Then place the reactor in a 25 °C water bath, irradiate and stir the reaction under different light sources (LED light, halogen light, natural diffused light). Take 1 mL of samples at certain time intervals, filter through a 0.22 μm filter membrane, and measure the absorbance with a UV-visible spectrophotometer, and finally calculate the DR degradation rate. From Figure 3 the data, it can be seen that the Zn 2 L 3 spiro MOC material only has an adsorption effect on methyl orange dye wastewater under dark conditions. After reaching the adsorption-desorption equilibrium state in 40 min, the dye concentration no longer changes, and the adsorption rate is 14.8%; for rhodamine B, it reaches the adsorption-desorption equilibrium within 60 min, and the adsorption rate is 13.2%; for reactive blue, it can reach the adsorption-desorption equilibrium within 40 min, and the adsorption rate is 18.3%. Under LED light, the Zn 2 L 3 spiro MOC material has a photocatalytic degradation rate of 75.6% for methyl orange within 2 h, a photocatalytic degradation rate of 66.4% for rhodamine B within 3 h, and a photocatalytic degradation rate of 83.9% for reactive blue within 2 h. The Zn 2 L 3 spiro MOC material shows a 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] For Zn 2 L 3 The degradation solution of the spiro MOC material of Zn was centrifuged, and the obtained solid sample was taken and washed three times with water 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 degradation process conditions, a cyclic photocatalytic degradation experiment was carried out to measure its degradation rate for the target dye. From Figure 4 the data, it can be seen that under the LED lamp, Zn 2 L 3 After the spiro MOC material of Zn was recycled for 5 times in the degradation of methyl orange, the degradation rate still remained above 80%; after 4 cycles of the degradation of rhodamine B and reactive blue, the photocatalytic degradation rate remained above 70%. After the degradation cycle experiment, nuclear magnetic characterization was carried out on the Zn 2 L 3 spiro MOC material before and after degrading the dye solution. From Figure 5 the data, it can be seen that after multiple cycles of use, the hydrogen spectrum of the Zn 2 L 3 spiro MOC material is basically the same as the hydrogen spectrum of the original MOC material, indicating that the Zn 2 L 3 spiro MOC material has good structural stability.

[0057] Example 4

[0058] This example illustrates the photocatalytic degradation performance of the Zn 2 L 3 spiro MOC material for tetracycline wastewater

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

[0060]

[0061] where A 0 is the initial absorbance of the simulated tetracycline wastewater; A t is 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 photocatalytic degradation light source

[0063] In a 100 mL reactor, 40 mL of tetracycline solution (20 mg / L) and Zn 2 L 350 mg of the spirochete MOC material was continuously stirred for 1 h under the condition of a light-shielded environment to achieve adsorption-desorption equilibrium. Then, the reactor was placed in a 25 °C water bath and irradiated under an LED light source. 1 mL of the sample was taken at certain time intervals and filtered through a 0.22 μm filter membrane, and then the absorbance was measured with a UV-visible spectrophotometer, and finally the DR degradation rate was calculated. From Figure 6 the data, it can be seen that after 90 min under the condition of no light-dark reaction, the adsorption rate of the Zn 2 L 3 spirochete MOC material for tetracycline was only 9.3%. Under the LED light, the degradation rate of the Zn 2 L 3 spirochete MOC material for tetracycline was 80.45%. It shows that the material has a significant photocatalytic degradation effect on tetracycline.

[0064] (2) Photocatalytic degradation cycle experiment

[0065] The degradation solution of the Zn 2 L 3 spirochete MOC material was centrifuged, and the obtained solid sample was taken and washed three times with water 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 cyclic photocatalytic degradation experiment was carried out to measure its degradation rate for tetracycline. From Figure 7 the data, it can be seen that under the LED light, the degradation rate of the Zn 2 L 3 spirochete MOC material remained above 75% after being recycled five times for tetracycline degradation. After the end, nuclear magnetic resonance characterization was carried out on the Zn 2 L 3 spirochete MOC material after cyclic degradation. From Figure 8 the data, it can be seen that the hydrogen spectrum of the Zn 2 L 3 spirochete MOC material was basically the same before and after cyclic use, indicating that the material showed good structural stability and good reusability.

[0066] Example 5

[0067] This example illustrates the photocatalytic reduction performance of the Zn 2 L 3 spirochete MOC material for Cr(VI)-containing wastewater

[0068] Pretreatment for photocatalytic reduction: Prepare a Cr(VI)-containing wastewater solution with a concentration of 10 mg / L; determine Cr(VI) by diphenylcarbazide spectrophotometry (HJ-908-2017, DPC method), and the maximum absorption wavelength is 554 nm. The absorbance of the Cr(VI)-containing wastewater was measured with a UV-visible spectrophotometer before and after wastewater treatment. The reduction rate was calculated according to the following formula:

[0069]

[0070] Among them, A 0 is 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 moment, and RR represents the reduction rate of the simulated Cr(VI)-containing wastewater.

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

[0072] Add 50 mL of the simulated Cr(VI)-containing wastewater solution (10 mg / L) and 100 mg of Zn 2 L 3 spirochetes into a 100 mL beaker, and continuously stir for 1 h under the condition of a light-shielded environment to achieve adsorption-desorption equilibrium. Then place the beaker in a 25 °C water bath, irradiate and stir the reaction for 180 min under different light sources (LED light, halogen light, natural diffused light), sample 1 mL at certain time intervals, filter through a 0.22 μm filter membrane, add DPC for color development, and measure its absorbance with a UV-visible spectrophotometer, and finally calculate the RR reduction rate. From Figure 9 the data, it can be seen that Zn 2 L 3 spirochete MOC material reaches adsorption-desorption equilibrium for Cr(VI) after 60 min under lightless conditions, and the adsorption rate is 16.9%. Under LED light, halogen light, and natural light, the reduction rates of Zn 2 L 3 spirochete MOC material for the Cr(VI) wastewater solution are 52.3%, 45.5%, and 31.3% respectively. It can be seen from this that Zn 2 L 3 spirochete 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] Centrifuge and separate the reduction solution of Zn 2 L 3 spirochete MOC material, take the obtained solid sample, wash it three times with water to remove surface impurities. Subsequently, place the MOC material in an oven at 110 °C and dry it for 3 h. Under the same optimized reduction process conditions, conduct a photocatalytic cycle reduction experiment and measure the reduction rate of the target Cr(VI). From Figure 10 the data, it can be seen that under LED light, the reduction rate of Zn 2 L 3 spirochete MOC material for Cr(VI) remains at 70% after 5 cycle reactions. After completion, for Zn 2 L3 The NMR characterization of the helical MOC material was carried out. By comparing with the hydrogen spectrum of the original MOC material, according to Figure 11 The results showed that Zn 2 L 3 After multiple cycles of use, the hydrogen spectrum of the helical MOC material was basically the same as that of the original MOC material, indicating that the material had good structural stability.

[0075] Example 6

[0076] This example illustrates the preparation of the Fe 2 L 3 helical MOC material

[0077] 19.08 mg (0.056 mmol) of 4,4'-(naphthalene-2,7-diyl dioxy)diphenylamine, 13.15 mg (0.037 mmol) of iron(III) trifluoromethanesulfonate, and 12.00 mg (0.112 mmol) of pyridine-2-carbaldehyde were successively added to a 10 mL flask, 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 for precipitation, followed by centrifugation and drying to obtain 30.00 mg of a purple solid. The yield was 70.8%, and the melting point was >300 °C. Fe 2 L 3 The characterization data of the helical MOC material ( Figure 12 , Figure 13 ): 1 H NMR (400 MHz, CD 3 CN): 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 [Fe 2 L 3 4+ , 607.45917 [Fe 2 L 3 4+ [OTf] - , 985.66821 [Fe 2 L 3 4+ 2[OTf] - , 2120.28979 [Fe 2 L 3 4+ 3[OTf] - .

[0078] To further confirm Fe 2 ​​​​L 3 For the structure of the helical MOC material, single crystal cultivation and crystal structure analysis were carried out on the synthesized product. Prismatic purple crystals were obtained by the acetonitrile-isopropyl ether diffusion method. The crystals were rinsed 3 times with petroleum ether and dried in vacuo for 30 min for crystal structure testing. Suitable single crystals were selected and adhered to glass fibers, and then placed on a BRUKER Apex II CCD single crystal diffractometer at room temperature, and irradiated with Mo Kα rays monochromatized by a graphite monochromator for scanning. Within a certain θ range, data were collected, and the Fe was solved by the direct method 2 L 3 Crystal structure of the helical MOC material. The coordinates of non-hydrogen atoms and anisotropic thermal temperature factors in the MOC material were refined to convergence by full matrix least squares method. All hydrogen atom positions were obtained by theoretical hydrogenation method. Structure analysis, calculation, refinement and drawing of single crystal molecular graphics were all completed by SHELXTL PC and MERCURY. The single crystal X-ray structure shows that the MOC material is a three-helical metal-organic cage structure compound, belonging to the triclinic system, and the space group is P-1 (#2). The ellipsoid diagram and the unit cell packing diagram are as Figure 14 、 Figure 15 shown. The main crystal structure parameters are shown in Table 1

[0079] Table 1 Fe 2 L 3 Crystal structure parameters of the MOC material

[0080]

[0081] Example 7

[0082] This example illustrates the performance of the Fe 2 L 3 helical MOC material in photocatalytic degradation of dye wastewater

[0083] The preparation of the dye solution, the measurement method of the degradation rate, etc. are the same as those in Example 3

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

[0085] Add 5 mg of Fe 2 L 3 helical MOC material and 100 mL of simulated dye wastewater solution into a 150 mL reactor, and continuously stir for 1 h in a dark environment to achieve adsorption-desorption equilibrium. Then place the reactor in a 25 °C water bath, irradiate and stir the reaction under different light sources (LED light, halogen light, natural diffused light). Take 1 mL of sample at certain time intervals, filter through a 0.22 μm filter membrane, and measure the absorbance with a UV-visible spectrophotometer to calculate the DR degradation rate. From Figure 16Data shows that Fe 2 L 3 The MOC material of Fe-L spirochete and methyl orange dye solution have no photoreaction for 90 min to reach the adsorption-desorption equilibrium, and the adsorption rate is 20.49%; for rhodamine B dye, the adsorption-desorption equilibrium is achieved within 60 min, and the adsorption rate reaches 30.52%. For reactive blue dye, the adsorption-desorption equilibrium is completed in 40 min, and the adsorption rate is 16.46%. Under the LED light, Fe 2 L 3 The MOC material of Fe-L spirochete has a photocatalytic degradation rate of 89.84% for methyl orange within 3 h, 71.32% for rhodamine B within 3 h, and 87.83% for reactive blue within 2 h. It can be seen that Fe 2 L 3 The MOC material of Fe-L spirochete has good photocatalytic degradation performance.

[0086] (2) Photocatalytic degradation cycle experiment

[0087] Centrifuge the degradation solution of the MOC material of Fe-L spirochete, take the solid sample and wash it three times with water to remove the surface impurities. Place the MOC material in an oven and dry it at 110 °C for 3 h, and conduct a cyclic degradation experiment under the same conditions to measure the degradation rate of the target dye. From 2 L 3 the data, under the LED light, the degradation rate of the MOC material of Fe-L spirochete for methyl orange after 7 cycles is 82%; for rhodamine B after 4 cycles, the degradation rate is more than 63%; for reactive blue KN-B after 5 cycles, the degradation rate is more than 83%. For the Fe Figure 17 L 2 L 3 spirochete MOC material after degrading the dye solution, conduct NMR characterization. It can be seen from 2 L 3 that before and after multiple cyclic degradations, the hydrogen spectrum of the Fe Figure 18 L 2 L 3 spirochete MOC material is basically the same, indicating that the Fe 2 L 3 spirochete MOC material has good structural stability.

[0088] Example 8

[0089] This example illustrates the photocatalytic degradation performance of the Fe 2 L 3 spirochete MOC material for tetracycline wastewater

[0090] The preparation of tetracycline wastewater and the measurement of the degradation rate are the same as those in Example 4.

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

[0092] In a 100 mL reactor, 40 mL of tetracycline solution (20 mg / L) and 50 mg of Fe 2 L 3 spirochete material were added successively, and it was continuously stirred for 1 h in a light-shielded environment to reach the adsorption-desorption equilibrium. The sample was placed in a 25 °C water bath, the reactor was irradiated under an LED light source, 1 mL of the sample was taken at certain time intervals, and after filtering through a 0.22 μm filter membrane, the absorbance was measured with a UV-visible spectrophotometer, and the DR degradation rate was calculated. As can be seen from Figure 19 the data, after 90 min under dark reaction conditions without light, the adsorption rate of Fe 2 L 3 spirochete MOC material for tetracycline was only 28.0%. Under the LED light, the degradation rate of Fe 2 L 3 spirochete MOC material for tetracycline wastewater could reach 71.6%. Thus, it can be seen that the MOC material has good photocatalytic degradation effect on simulated tetracycline wastewater.

[0093] (2) Photocatalytic degradation cycle experiment

[0094] The photocatalytic cycle degradation experiment of the MOC material was carried out under the LED light. The Fe 2 L 3 spirochete MOC material in the degradation system was centrifuged and separated, washed 3 times to remove the impurities on the surface of the MOC material, and placed in an oven at 110 °C for drying for 3 h. The degradation experiment was carried out in the same conditions, and the degradation rate of tetracycline wastewater was measured. As can be seen from Figure 20 the data, under the LED light, the degradation rate of Fe 2 L 3 spirochete MOC material remained above 65% after 5 cycles of degradation of tetracycline. The Fe 2 L 3 spirochete MOC material before and after cycling was characterized by NMR, Figure 21 indicating that the hydrogen spectrum of Fe 2 L 3 spirochete MOC material was basically the same before and after multiple cycles of use, indicating that the material has good structural stability and recyclability.

Claims

1. A spiral MOC material photocatalyst, the structure of which is shown in general formula (I): in, M 2+ Each independently is Zn 2+ , Fe 2+ .

2. A method for preparing the compound of general formula (I) as claimed in claim 1. The compound is synthesized by self-assembly using 4,4'-(naphthalene-2,7-diyldioxy)diphenylamine, trifluoromethanesulfonate and pyridine-2-carboxaldehyde. The reaction process is as follows: in, M 2+ Each independently is Zn 2+ , Fe 2+ .

3. The preparation method according to claim 2, wherein: The reaction solvent in reaction (1) is selected from acetonitrile, methanol, pyridine, preferably acetonitrile; the reaction temperature is 30-70°C, preferably 50°C.

4. Use of the spiral MOC material obtained by the preparation method according to any one of claims 1 to 3, characterized in that: Used for photocatalytic degradation of dye wastewater, photocatalytic degradation of tetracycline wastewater or photocatalytic reduction of Cr(VI) wastewater.

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