Crystalline metal organic cluster compound material, preparation method thereof and application of crystalline metal organic cluster compound material in photocatalytic degradation of polyester plastic

Abstract

The invention discloses a crystalline metal organic cluster compound material, a preparation method thereof and application of the crystalline metal organic cluster compound material in photocatalytic degradation of polyester plastics. Four N-hydroxy-1, 8-naphthalimide ligands and two metal atoms form a stable square tetranuclear skeleton, and the tetranuclear skeleton has excellent photoelectron transfer characteristic and stability, can react with ammonia water to form NH2 so as to attack ester bonds, and shows extremely high activity when being used for photocatalytic degradation of polyester plastics at room temperature. The crystalline metal organic cluster compound material can be prepared through solvothermal reaction, the preparation method is simple, complex reaction processes and harsh reaction conditions are not needed, and large-scale preparation can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology of metal-organic complexes, specifically relating to a crystalline metal-organic cluster material, its preparation method, and its application in photocatalytic degradation of polyester plastics. Background Technology

[0002] Polyester plastics (such as PET, PBT, and PLA) are widely used in packaging, textiles, and engineering plastics due to their excellent mechanical properties, chemical stability, and low cost. However, their highly stable chemical structure (such as the aromatic rings and ester bonds in PET) makes them difficult to degrade in the natural environment, causing serious white pollution problems. Unlike conventional pollutants, plastics are difficult to degrade naturally and can persist in the environment for a long time, forming microplastic particles through physical breakage or photo-oxidation. These microplastics can adsorb toxic substances, be transferred through the food chain, and accumulate in organisms, threatening ecosystem stability and human health. Therefore, the development of efficient plastic recycling and harmless treatment technologies has become an urgent need for global sustainable development.

[0003] To address plastic pollution, researchers have proposed several new strategies for upgrading and recycling polyester plastics. Chemical recycling is a promising method, depolymerizing PET into monomer units for subsequent polymerization or selective conversion into high-value chemicals. However, existing PET depolymerization systems typically rely on precious metal catalysts and require harsh conditions such as degrading agents and high temperatures and pressures during the reaction, which limits reaction efficiency and product purity, and the high cost hinders industrial application. Therefore, current research increasingly focuses on developing more efficient and economical catalytic systems. On the one hand, this involves designing novel ligands or multifunctional ligands to improve catalyst stability and activity while reducing dependence on precious metals; on the other hand, it involves exploring milder catalytic degradation pathways using clean energy sources such as light, electric fields, or low-temperature thermal energy to achieve highly selective and high-purity PET depolymerization. Summary of the Invention

[0004] Based on the above reasons, the first objective of this invention is to provide a crystalline metal-organic cluster material with a square tetranuclear framework structure, wherein the metal atoms and the naphthalenedicarboximide structure have excellent photoelectron transfer characteristics, promoting the reaction of carbonyl groups with ammonia to form NH2·, which in turn acts on the ester bond, and photocatalyzes the breaking of the ester bond.

[0005] The second objective of this invention is to provide a method for preparing crystalline metal-organic cluster materials, which can be prepared by solvothermal reaction. The preparation method is simple, does not require complex reaction processes and harsh reaction conditions, and can be prepared on a large scale.

[0006] A third objective of this invention is to provide an application of a crystalline metal-organic cluster material as a photocatalyst in the degradation of polyester plastics. It can serve as a homogeneous catalyst, which is beneficial for the degradation of polyester plastics.

[0007] The fourth objective of this invention is to provide a method for photocatalytic degradation of polyester plastics, which exhibits extremely high activity in the photocatalytic degradation of polyester plastics at room temperature, and can degrade polyester with significant degradation effect.

[0008] The first objective of this invention can be achieved by adopting the following technical solution:

[0009] A crystalline metal-organic cluster material, wherein the molecular formula of the crystalline metal-organic cluster material is C 48 H 28 N4O 14 M2 comprises four N-hydroxy-1,8-naphthalenedimide ligands, two coordinated water molecules, and two metal atoms M; wherein M is Zn or Ni.

[0010] Furthermore, in the single-crystal structure of the crystalline metal-organic cluster material, the N-hydroxy oxygen in the two N-hydroxy-1,8-naphthalenedicarboximide ligands acts as μ-O atoms and is coordinated with the two M metal atoms respectively; the two N-hydroxy-1,8-naphthalenedicarboximide ligands are coordinated with one of the two M metal atoms respectively, and the four N-hydroxy-1,8-naphthalenedicarboximide ligands and the two metal atoms M form a square tetranuclear framework.

[0011] Furthermore, the crystalline metal-organic cluster material is monoclinic with space group P21 / c; its unit cell parameters are: α=90°, β=100.666(2)°, γ=90°.

[0012] The second objective of this invention can be achieved by adopting the following technical solution:

[0013] A method for preparing a crystalline metal-organic cluster material includes the following steps:

[0014] N-hydroxy-1,8-theradicarboximide and the M metal precursor are subjected to a solvothermal reaction in a solvent to prepare the crystalline metal-organic cluster material.

[0015] Furthermore, the M metal precursor is a sulfate, nitrate, or hydrate of the M metal.

[0016] Furthermore, the solvent is a mixture of DMF and water, with a volume ratio of DMF to water of 1:(0.7-1.6).

[0017] Furthermore, the molar-volume ratio of N-hydroxy-1,8-theacarboximide to the solvent is 1 mmol: (5-20) mL.

[0018] Furthermore, the molar ratio of N-hydroxy-1,8-theradicarboximide to the M metal precursor is 1:(0.8-1.5).

[0019] Furthermore, the reaction was carried out in the presence of triethylamine, with a volume ratio of triethylamine to solvent of 1:(5-20).

[0020] Furthermore, the reaction conditions are: 40-100℃ for 24-96 hours.

[0021] Furthermore, it also includes an activation step: the crystalline metal-organic cluster material and ammonia water are placed in a sealed container without direct contact, and activated for 0.5-12 hours.

[0022] The third objective of this invention can be achieved by adopting the following technical solution:

[0023] The application of the crystalline metal-organic cluster material as a photocatalyst in the degradation of polyester plastics.

[0024] The fourth objective of this invention can be achieved by adopting the following technical solution:

[0025] A method for photocatalytic degradation of polyester plastic, wherein the polyester is reacted in an ammonia solution in the presence of the crystalline metal-organic cluster material catalyst under sunlight irradiation or simulated sunlight irradiation.

[0026] Furthermore, the mass concentration of ammonia water is 25-35%.

[0027] Furthermore, the simulated solar radiation reaction conditions are: Xe lamp light source, 200-400W, reaction time 48-72h.

[0028] Furthermore, the polyester is polyethylene terephthalate; the mass-to-volume ratio of polyester to ammonia is 1g:(100-150)mL.

[0029] Furthermore, the mass ratio of the crystalline metal-organic cluster catalyst to the polyester is (1-2) g: 50 g.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The present invention provides a crystalline metal-organic cluster material in which metal atoms and naphthalenedicarboximide form a square tetranuclear framework structure, which has excellent stability; and the structure of metal atoms and naphthalenedicarboximide promotes the photoelectron transfer characteristics of the material, and the carbonyl group of naphthalenedicarboximide can react with ammonia water to form NH2·, which then attacks the ester bond and accelerates the breaking of the ester bond.

[0032] 2. The present invention provides a method for preparing a crystalline metal-organic cluster material, which can be prepared by a solvothermal reaction. The preparation method is simple, does not require a complex reaction process or harsh reaction conditions, and can be prepared on a large scale.

[0033] 3. The application of the crystalline metal-organic cluster material of the present invention as a photocatalyst in the degradation of polyester plastics; as a homogeneous catalyst, it can achieve highly active degradation of polyester plastics under sunlight irradiation at room temperature. Attached Figure Description

[0034] Figure 1 A schematic diagram of the molecular structure of Zn2L4 prepared in Example 1;

[0035] Figure 2 A schematic diagram of the molecular structure of Ni2L4 prepared for Comparative Example 2;

[0036] Figure 3 The images show the crystal morphology of the crystalline organometallic cluster material prepared in Example 1; the left image shows Zn2L4 prepared in Example 1; and the right image shows Ni2L4 prepared in Example 2.

[0037] Figure 4 The Zn2L4 prepared in Example 1 was activated to Zn2L4· - A schematic diagram of the process;

[0038] Figure 5 Zn2L4 and Zn2L4· prepared in Example 1 - (Left) and solid-state UV-Vis spectra of Ni2L4 prepared in Example 2 (Right);

[0039] Figure 6 Zn2L4 and Zn2L4· prepared in Example 1 - X-ray powder diffraction patterns of Zn2L4; where a) is the spectrum of Zn2L4 after treatment in different solvents and the simulated spectrum of Zn2L4 single crystal; b) is the spectrum of Zn2L4· - Experimental and simulated spectra of Zn2L4;

[0040] Figure 7 X-ray powder diffraction pattern of Ni2L4 prepared in Example 2, and X-ray powder diffraction patterns of Ni2L4 after treatment in different solvents;

[0041] Figure 8 Zn2L4 and Zn2L4· prepared in Example 1 - (Left) and the infrared spectra of Ni2L4 prepared in Example 2 (Right);

[0042] Figure 9 Zn2L4 and Zn2L4· prepared in Example 1 - Thermogravimetric analysis (TGA) of Ni2L4 prepared in Example 2 (left) and (right).

[0043] Figure 10 This is a diagram showing the reaction state during the degradation experiment in Example 3;

[0044] Figure 11 The above is the 1H NMR spectrum of the solid product from the degradation experiment in Example 3;

[0045] Figure 12 The image shows the 1H NMR spectrum of pure terephthalamide.

[0046] Figure 13 The 1H NMR spectrum of the liquid product from the degradation experiment in Example 3;

[0047] Figure 14 The image shows the 1H NMR spectrum of pure ethylene glycol.

[0048] Figure 15 This is a schematic diagram showing the catalytic activity and ethylene glycol yield in the degradation experiments of Example 3 and the comparative example;

[0049] Figure 16 The images show the mass spectra of the catalyst before and after the degradation experiment in Example 3; the lower image shows the catalyst separated after the degradation reaction; the upper image shows the mass spectrum of the initially added Zn2L4 catalyst.

[0050] Figure 17 Schematic diagram showing the catalytic activity and ethylene glycol yield in degradation experiments of different PET sources;

[0051] Figure 18 This is a schematic diagram showing the catalytic activity and ethylene glycol yield in the multiple cyclic degradation experiment of Example 5;

[0052] Figure 19 The image shows the X-ray powder diffraction patterns of the catalyst before and after the degradation experiment in Example 3. Detailed Implementation

[0053] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] Metal-organic clusters (MOCs), with their discrete molecular structure, high-density active sites, and tunable coordination microenvironments, offer highly efficient catalytic solutions for the degradation of plastics (such as PET and polyolefins), particularly through photocatalysis, hydrolysis, or redox pathways to achieve efficient depolymerization and resource recovery of plastics. However, MOCs are widely hampered by demanding preparation conditions and low yields, hindering their large-scale application. Therefore, this application provides a crystalline metal-organic cluster material, its preparation method, and its application in the photocatalytic degradation of polyester plastics.

[0055] A crystalline metal-organic cluster material, wherein the molecular formula of the crystalline metal-organic cluster material is C 48 H 28 N4O 14 M2 comprises four N-hydroxy-1,8-naphthalenedimide ligands, two coordinated water molecules, and two metal atoms M; wherein M is Zn or Ni.

[0056] The molecular structure of the N-hydroxy-1,8-naphthalenediamine ligand is as follows.

[0057]

[0058] Containing a polycyclic conjugated structure, its coordination with metal atoms facilitates photoelectron transfer and enhances photocatalytic activity. Furthermore, the carbonyl groups it contains serve two purposes: some coordinate with metal atoms, increasing the chemical and physical stability of the crystalline metal-organic cluster material; others act as reaction sites, providing potential for subsequent catalytic reactions.

[0059] In one embodiment, in the single-crystal structure of the crystalline metal-organic cluster material, the N-hydroxy oxygen in the two N-hydroxy-1,8-naphthalenedicarboximide ligands acts as μ-O atoms and is coordinated with the two M metal atoms respectively; the two N-hydroxy-1,8-naphthalenedicarboximide ligands are coordinated with one of the two M metal atoms respectively, and the four N-hydroxy-1,8-naphthalenedicarboximide ligands and the two metal atoms M form a square tetranuclear framework.

[0060] In the two N-hydroxy-1,8-naphthalenedicarboximide ligands, the N-hydroxyl oxygen atom acts as a μ-O atom and coordinates with two M metal atoms, forming a square tetranuclear structure. One of the two carbonyl groups adjacent to the hydroxyl group coordinates with the same metal atom, while in the other two N-hydroxy-1,8-naphthalenedicarboximide ligands, the hydroxyl and carbonyl groups of each ligand coordinate with the same metal atom, and the two ligands coordinate with two metal atoms respectively. The four N-hydroxy-1,8-naphthalenedicarboximide ligands form a square tetranuclear framework with two metal atoms. When the metal is Zn, the single-crystal structure and the three-dimensional supramolecular stacked structure are as follows: Figure 1As shown; when the metal is Ni, the single-crystal structure and the three-dimensional supramolecular stacked structure are as follows. Figure 2 As shown.

[0061] The square tetranuclear framework provides unique photothermal and chemical stability to crystalline metal-organic cluster materials; the uncoordinated carbonyl groups provide reaction sites.

[0062] As one embodiment, the crystalline metal-organic cluster material is monoclinic with space group P21 / c; its unit cell parameters are: α=90°, β=100.666(2)°, γ=90°.

[0063] The present application discloses a method for preparing a crystalline metal-organic cluster material, comprising the following steps:

[0064] N-hydroxy-1,8-theradicarboximide and the M metal precursor are subjected to a solvothermal reaction in a solvent to prepare the crystalline metal-organic cluster material.

[0065] Solvothermal reactions offer high yields and are easy to achieve under suitable conditions, making them a suitable method for large-scale synthesis that can significantly reduce material costs. This allows for the preparation of materials in the hundreds of grams in the laboratory.

[0066] In one embodiment, the M metal precursor is a sulfate, nitrate, or hydrate of the M metal. Preferably, when the M metal is zinc, the precursor is zinc sulfate or zinc sulfate heptahydrate; when the M metal is nickel, the precursor is nickel nitrate or nickel nitrate hexahydrate.

[0067] In one embodiment, the solvent is a mixture of DMF and water, with a volume ratio of DMF to water of 1:(0.7-1.6). DMF and water are commonly used reagents. MDF is miscible with water and has good solubility for both the metal precursor and N-hydroxy-1,8-theradicarboximide, which is beneficial for the formation of solvothermal crystalline metal-organic cluster materials. Furthermore, the formed crystalline metal-organic cluster material can precipitate after the reaction solution cools, facilitating separation.

[0068] As one embodiment, the molar-volume ratio of N-hydroxy-1,8-theacarboximide to solvent is 1 mmol:(5-20) mL.

[0069] In one embodiment, the molar ratio of N-hydroxy-1,8-theradicarboximide to the M metal precursor is 1:(0.8-1.5).

[0070] As one embodiment, the reaction is carried out in the presence of triethylamine, with a volume ratio of triethylamine to solvent of 1:(5-20).

[0071] As one implementation method, the reaction conditions are: 40-100℃ for 24-96 h. High-yield large-scale synthesis is achieved under mild conditions, atmospheric pressure, and 40-100℃.

[0072] One implementation method also includes a separation and purification process. After the precipitated crystals are separated into solid and liquid phases, they are washed thoroughly several times with a mixed solution of DMF and H2O until the solution becomes clear.

[0073] As one implementation method, an activation step is also included: the crystalline metal-organic cluster material and ammonia water are placed in a sealed container without direct contact, and activated for 24-96 hours.

[0074] This application describes the use of crystalline metal-organic cluster materials as photocatalysts in the degradation of polyester plastics; the polyester is reacted in an ammonia solution under the presence of the crystalline metal-organic cluster material catalyst, either by solar irradiation or simulated solar irradiation.

[0075] Crystalline metal-organic clusters can serve as homogeneous catalysts, achieving significant enhanced reactivity through thorough contact with the substrate. Uncoordinated carbon groups (C=O) in the catalyst can adsorb NH3 from the reaction solvent, forming NH2·, which then attacks the ester bonds, leading to the selective degradation of polyesters.

[0076] When the polyester is polyethylene terephthalate (PET), the degradation products are terephthalamide and ethylene glycol. It exhibits extremely high activity in the photocatalytic degradation of polyester plastics at room temperature, and selectively generates ethylene glycol (EG). The product can be easily separated by vacuum distillation after the reaction, demonstrating excellent recyclability.

[0077] In one implementation method, the mass concentration of ammonia water is 25-35%. Ammonia water forms NH2· free radicals, and then reacts to form ammonia water again, so there is no loss.

[0078] As one implementation method, the simulated solar radiation reaction conditions are: Xe lamp light source, 200-400w, reaction time 48-72h.

[0079] In one embodiment, the polyester is polyethylene terephthalate; the mass-to-volume ratio of polyester to ammonia is 1g:(100-150)mL.

[0080] In one embodiment, the mass ratio of the crystalline metal-organic cluster catalyst to the polyester is (1-2) g: 50 g. The crystalline metal-organic cluster material serves as a homogeneous catalyst. After the reaction is complete, the reaction solution is fractionated under reduced pressure to obtain a liquid product. The crystalline metal-organic cluster catalyst can be obtained by evaporating the reaction solution to dryness and can be recycled.

[0081] The following provides a further explanation using specific implementation methods.

[0082] Example 1

[0083] A method for preparing a crystalline binuclear zinc organic cluster material includes the following steps:

[0084] 100 mmol of N-hydroxy-1,8-naphthalenediamine and 100 mmol of ZnSO4·7H2O were dispersed in a mixed solution of 600 mL of DMF and 600 mL of H2O and mixed thoroughly to obtain a mixture. 150 mL of triethylamine was added to the mixture, and the mixture was stirred for 10 min to dissolve and mix. The resulting mixture was then placed in a round-bottom flask. The flask containing the mixture was heated to 80 °C for 3 days. After cooling to room temperature, the treated sample was filtered. The obtained solid crystals were thoroughly washed with a mixed solution of DMF and H2O until the solution became clear, yielding a crystalline organometallic cluster material with the molecular formula C. 48 H 26 N4O 14 Zn2; named Zn2L4; appearance diagram as follows Figure 3 As shown in the left figure;

[0085] The obtained Zn₂L₄ crystals were placed in a petri dish, which was then placed in a beaker containing 5 mL of ammonia solution, ensuring that the Zn₂L₄ in the petri dish did not directly contact the ammonia solution. The opening of the beaker was sealed with sealing film. After 1 hour, blocky crystals were obtained and named Zn₂L₄· - The activation process is as follows: Figure 4 As shown.

[0086] Example 2

[0087] A method for preparing a crystalline binuclear nickel organic cluster material includes the following steps:

[0088] 100 mmol of N-hydroxy-1,8-naphthalenediamine and 120 mmol of Ni(NO3)2·6H2O were dispersed in a mixed solution of 500 mL DMF and 800 mL H2O and mixed thoroughly to obtain a mixture. 100 mL of triethylamine was added to the mixture, and the mixture was stirred for 10 min to dissolve and mix. The resulting mixture was then placed in a round-bottom flask. The flask containing the mixture was heated to 100 °C for 24 h. After cooling to room temperature, the treated sample was filtered. The obtained solid crystals were thoroughly washed with a mixed solution of DMF and H2O until the solution became clear, yielding a crystalline organometallic cluster material with the molecular formula C. 48 H 26 N4O 14 Ni2; named Ni2L4; appearance diagram as follows Figure 3 As shown in the right figure;

[0089] The obtained Ni₂L₄ crystals were placed in a petri dish, which was then placed in a beaker containing 5 mL of ammonia solution, ensuring that the Ni₂L₄ in the petri dish did not directly contact the ammonia solution. The opening of the beaker was sealed with sealing film. After 3 hours, blocky crystals were obtained; these were named Ni₂L₄· - .

[0090] Material characterization:

[0091] (1) The Zn2L4 and Zn2L4· prepared in Example 1 - Solid-state ultraviolet-visible spectroscopy (UV / Vis) was performed, and the UV-vis spectrum is shown below. Figure 5 The left figure shows the solid-state UV-Vis spectroscopy (UV / Vis) test performed on the Ni2L4 prepared in Example 2. The UV-Vis spectrum is shown below. Figure 5 As shown in the figure on the right.

[0092] from Figure 5 It can be seen that Ni₂L₄ exhibits nearly 100 nm greater light absorption than its ligand; activated Zn₂L₄· - The ultraviolet absorption is significantly enhanced, extending by nearly 100 nm compared to unactivated Zn2L4.

[0093] (2) The Zn2L4 and Zn2L4· prepared in Example 1 - X-ray powder diffraction tests were performed, and the X-ray powder diffraction pattern is shown below. Figure 6 As shown; where a) are the spectra of Zn2L4 after treatment in different solvents (soaking for 24 h) and the simulated spectrum of Zn2L4 single crystal; b) are the spectra of Zn2L4· - Experimental and simulated spectra of Zn₂L₄ are shown. X-ray powder diffraction (XRD) was performed on Ni₂L₄ prepared in Example 2. The XRD pattern of Ni₂L₄ and the spectra of Ni₂L₄ after treatment in different solvents (immersion for 24 hours) are shown below. Figure 7 As shown.

[0094] from Figure 6 and Figure 7 It can be seen that Zn2L4, Zn2L4· - Both Ni2L4 and Ni2L4 maintain good stability in a variety of base solvents.

[0095] (3) The Zn2L4 and Zn2L4· prepared in Example 1 - The Ni2L4 prepared in Example 2 was subjected to infrared spectroscopy testing, and the results are as follows: Figure 8 As shown, the left figure is a crystalline binuclear zinc organic cluster material; the right figure is a crystalline binuclear nickel organic cluster material.

[0096] Figure 8In the left image, the Zn2L4 sample is at 1630-1680 cm⁻¹. -1 The ν(C=O) vibrations within the range show a significant shift compared to the pure ligand. This indicates electron transfer in Zn₂L₄, indicative of the characteristic coordination between the imide and the metal; similarly, in the right figure, the Ni₂L₄ sample exhibits a similar shift within the 1630-1680 cm⁻¹ range. -1 The ν(C=O) vibrations within the range show a significant shift compared to the pure ligand; this also indicates the presence of electron transfer in Ni2L4, which is characteristic of imide coordination with metal.

[0097] (4) The Zn2L4 and Zn2L4· prepared in Example 1 - The Ni₂L₄ prepared in Example 2 was subjected to thermogravimetric analysis (TGA). The TGA results are as follows: Figure 9 As shown, the left figure is a crystalline binuclear zinc organic cluster material; the right figure is a crystalline binuclear nickel organic cluster material.

[0098] Zn2L4 and Zn2L4· - Both Zn2L4 and Ni2L4 exhibit good thermal stability. - The thermogravimetric analysis curves of Ni2L4 remain stable around 350℃; Ni2L4 remains stable at 350℃, indicating good thermal stability.

[0099] Example 3

[0100] 15g of the Zn2L4 catalyst prepared in Example 1 was mixed with 500g of polyethylene terephthalate, and 10L of 30% ammonia solution was added. The reactor was then sealed. A Xe lamp (300W) was used to simulate sunlight irradiation of the reactor for 55 hours, with stirring applied (reaction state as shown). Figure 10 (As shown); after the reaction is complete, the solid product is obtained by filtration; the filtrate is heated to 70°C and the condensate is collected; then the liquid product is obtained by vacuum distillation and the catalyst is separated.

[0101] The solid product was analyzed by NMR, and the NMR spectrum is as follows: Figure 11 As shown; NMR spectrum of pure terephthalamide ( Figure 12 The results are consistent with those obtained by NMR analysis of the liquid product, as shown in the NMR spectrum. Figure 13 As shown; NMR spectrum of pure ethylene glycol ( Figure 14 Consistent with.

[0102] The separated catalyst was analyzed by mass spectrometry. Figure 16 The molecular weight (see figure below) is related to the added Zn2L4 catalyst (…). Figure 16 The above figure shows the same result, indicating that the Zn2L4 catalyst was separated.

[0103] X-ray powder diffraction (XPD) was performed on the Zn₂L₄ catalyst before the reaction and the separated catalyst. The XPD patterns are shown below. Figure 19 As shown, the catalyst crystals did not undergo significant changes, indicating that the catalyst structure was stable and not damaged.

[0104] Catalytic activity and ethylene glycol yield, as follows Figure 15 As shown.

[0105] Example 4

[0106] The PET from cola bottles, tissues, shirts, and backpacks was degraded using the conditional method of Example 3. The degradation results are as follows: Figure 17 As shown.

[0107] Example 5

[0108] The catalyst separated in Example 3 was recycled under the catalytic conditions of Example 3 for 2, 3, 4, and 5 cycles. The yield of ethylene glycol was as follows: Figure 18 As shown.

[0109] Comparative Example

[0110] Catalytic degradation was carried out using N-hydroxy-1,8-naphthalenedicarboximide ligand, zinc sulfate, or a mixture of N-hydroxy-1,8-naphthalenedicarboximide ligand and zinc sulfate as catalysts, according to the method in Example 3. The results are as follows: Figure 15 As shown; the reaction was carried out according to the reaction procedure of Example 3 without any catalyst, and the results are as follows. Figure 15 As shown.

[0111] The results of Example 3 show that the Zn2L4 catalyst exhibits excellent degradation performance, with a degradation activity reaching 1.1 × 10⁻⁶. 4 mg PET d -1 g cat -1 The yield of ethylene glycol reached over 95%. However, N-hydroxy-1,8-naphthalenedicarboximide ligand, zinc sulfate, and a mixture of N-hydroxy-1,8-naphthalenedicarboximide ligand and zinc sulfate as catalysts only showed slightly better performance than the blank group, and were far inferior to the Zn₂L₄ catalyst.

[0112] The results of Example 4 show that the Zn2L4 catalyst has a good degradation effect on PET from various sources.

[0113] The results of Example 5 show that the performance of the Zn2L4 catalyst decreases slightly with increasing cycle number, but after 5 cycles, the catalytic activity still reaches 0.9 × 10⁻⁶. 4 mg PET d -1 g cat-1 The yield of ethylene glycol was close to 80%, indicating that the Zn2L4 catalyst exhibits excellent stability and cycling performance.

[0114] In summary, the crystalline metal-organic cluster material of this application, as a homogeneous catalyst, forms NH2· radicals from NH3, which can act on ester bonds. It exhibits extremely high activity in the photocatalytic degradation of polyester plastics at room temperature, and selectively degrades PET into terephthalamide and ethylene glycol (EG) with high selectivity. The residue can be separated by simple vacuum distillation after the reaction, demonstrating excellent recyclability.

[0115] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A crystalline metal-organic cluster material, characterized in that, The molecular formula of the crystalline metal-organic cluster material is C. 48 H 28 N4O 14 M2 comprises four N-hydroxy-1,8-naphthalenedimide ligands, two coordinated water molecules, and two metal atoms M; wherein M is Zn or Ni.

2. The crystalline metal-organic cluster material according to claim 1, characterized in that, In the single-crystal structure of the crystalline metal-organic cluster material, the N-hydroxy oxygen in the two N-hydroxy-1,8-naphthalenediamine ligands acts as μ-O atoms and is coordinated with the two M metal atoms respectively; the two N-hydroxy-1,8-naphthalenediamine ligands are coordinated with one of the two M metal atoms respectively, and the four N-hydroxy-1,8-naphthalenediamine ligands and the two metal atoms M form a square tetranuclear framework.

3. The crystalline metal-organic cluster material according to claim 1, characterized in that, The crystalline metal-organic cluster material is monoclinic with space group P21 / c; its unit cell parameters are: α=90°, β=100.666(2)°, γ=90°.

4. A method for preparing a crystalline metal-organic cluster material, characterized in that, Includes the following steps: N-hydroxy-1,8-theradicarboximide and the M metal precursor are subjected to a solvothermal reaction in a solvent to prepare the crystalline metal-organic cluster material.

5. The method for preparing the crystalline metal-organic cluster material according to claim 4, characterized in that, The M metal precursor is a sulfate, nitrate, or hydrate of the M metal; The solvent is a mixture of DMF and water, with a volume ratio of DMF to water of 1:(0.7-1.6).

6. The method for preparing the crystalline metal-organic cluster material according to claim 4, characterized in that, The molar-volume ratio of N-hydroxy-1,8-theacarboximide to solvent is 1 mmol: (5-20) mL; The molar ratio of N-hydroxy-1,8-theacarboximide to the M metal precursor is 1:(0.8-1.5); The reaction was carried out in the presence of triethylamine, with a volume ratio of triethylamine to solvent of 1:(5-20); The reaction conditions are: 40-100℃ for 24-96 hours.

7. The method for preparing the crystalline metal-organic cluster material according to claim 4, characterized in that, It also includes an activation step: the crystalline metal-organic cluster material and ammonia water are placed in a sealed container without direct contact, and activated for 0.5-12 hours.

8. The application of the crystalline metal-organic cluster material according to any one of claims 1-7 as a photocatalyst in the degradation of polyester plastics.

9. A method for photocatalytic degradation of polyester plastics, characterized in that, The polyester is reacted in an aqueous ammonia solution in the presence of a catalyst of the crystalline metal-organic cluster material according to any one of claims 1-8, under solar irradiation or simulated sunlight irradiation.

10. The method for photocatalytic degradation of polyester plastics according to claim 9, characterized in that, The mass concentration of ammonia water is 25-35%; The simulated solar radiation reaction conditions are: Xe lamp source, 200-400w, reaction time 48-72h; The polyester is polyethylene terephthalate; the mass-to-volume ratio of polyester to ammonia is 1g:(100-150)mL. The mass ratio of the crystalline metal-organic cluster catalyst to polyester is (1-2)g:50g.

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