Metal organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a metal organic framework material and a preparation method and application thereof, the chemical formula of the metal organic framework material is {[Ce2 (L2) (HL2) 2 (H2O) 2 (H2O)]} n, {[CMe (L2) 4 (H2O) (CH3COO)]} n, {[Eu (HL2) (PTA) 0.5 (DMF) 2]. DMF} n and {[Eu (L2) (C2O4) 0.5 (H2O)]} n, and the metal organic framework material is used for preparing a degradable PBAT / PLA film. A metal organic framework material, modified nano calcium carbonate and modified cassava starch are added into the degradable film, the metal organic framework is used as a catalyst to catalyze nano cellulose to graft polylactic acid, an obtained graft copolymer is used as a solubilizer, and calcium carbonate and the like are added, so that the cost is reduced; meanwhile, the mechanical property of the degradable film can be effectively improved, and the degradable film has the fluorescence characteristic.

Description

Technical Field

[0001] The present invention relates to the technical field of degradable films. More specifically, the present invention relates to a metal-organic framework material and its preparation method and application. Background Art

[0002] PLA has great development potential and has been attracting much attention in the research field of biodegradable materials in the past few decades. PLA has good biocompatibility and biodegradability. At the same time, PLA also has some defects, such as high brittleness and low impact resistance. Therefore, researchers have modified PLA to expand its application scope, mainly including copolymerization modification, blending modification, and plasticization modification. PBAT is polymerized by transesterification or direct esterification and can be naturally degraded by microorganisms in the soil like PLA. There is a synergistic effect between PBAT and PLA, and they can be used to prepare biodegradable composites with good flexibility. However, the cost is relatively high. Many researchers have reduced the cost by adding fillers to the composite film, but the addition of fillers will lead to a decline in the performance of the film. Summary of the Invention

[0003] An object of the present invention is to solve at least the above problems and provide at least the advantages described hereinafter.

[0004] Another object of the present invention is to provide a metal-organic framework material, which adds a metal-organic framework material as a catalyst to a degradable film to catalyze the grafting of nanocellulose onto polylactic acid. The obtained graft copolymer is used as a solubilizer, and calcium carbonate and the like are added to reduce the cost. While reducing the cost, the mechanical properties of the degradable film can be effectively improved, and it has fluorescence characteristics.

[0005] To achieve these and other advantages in accordance with the present invention, there is provided a metal-organic framework material, and the chemical formula of the metal-organic framework material is {[Ce2(L 2 )(HL 2 )2(H2O)2(H2O)]} n 、{[Се з (L 2 )4(Η2O) з (СH3COO)]} n 、

[0006] {[Eu(HL2)(PTA) 0.5 (DMF)2]·DMF} n 、or {[Eu(L 2 )(C2O4) 0.5 (H2O)]} n 。

[0007] Preferably, the metal-organic framework material is prepared by a hydrothermal method using a ligand and a metal salt as raw materials, wherein the ligand is (5-(1H-imidazolyl)isophthalic acid, and the metal salt is Ce(NO3)3·6H2O or Eu(NO3)3·6H2O.

[0008] In addition, an application of the metal-organic framework material is also provided, and the metal-organic framework material is used for preparing a modified degradable PBAT / PLA film.

[0009] Preferably, the preparation method of the degradable PBAT / PLA film is as follows:

[0010] Step 1: Using cellulose and L-lactide as raw materials and the metal-organic framework material as a catalyst, prepare a cellulose-polylactide graft copolymer, wherein the cellulose is cotton nanofiber or banana cellulose;

[0011] Step 2: Using the cellulose-polylactide graft copolymer, polylactic acid, poly(butylene adipate terephthalate), and an additive as raw materials, obtain a degradable film, wherein the additive is modified nano calcium carbonate or modified cassava starch.

[0012] Preferably, the preparation method of the modified nano calcium carbonate is as follows: First, prepare a mixed solution of a silane coupling agent and absolute ethanol, then adjust the pH of the mixed solution to 4-5 using acetic acid, then add calcium carbonate and stir for 0.5 h, filter and dry to obtain the modified nano calcium carbonate.

[0013] Preferably, the preparation method of the modified cassava starch is as follows: Add a silane coupling agent and cassava starch to a beaker, and stir at 100 °C for 20 min to obtain the modified cassava starch.

[0014] Preferably, in Step 1, the dosage of the metal-organic framework material is 1-3% of the total mass of L-lactide.

[0015] Preferably, in Step 2, the addition amount of the cellulose-polylactide graft copolymer is 2-6 wt% of the total mass of polylactic acid and poly(butylene adipate terephthalate).

[0016] The present invention has at least the following beneficial effects:

[0017] First, the Ce-MOF-2, Ce-MOF-1, Eu-MOF-1, and Eu-MOF-2 prepared by the present invention have good thermal stability, high catalytic activity, and low toxicity.

[0018] Second, the degradable film prepared in Example 5 of the present invention has fluorescence properties. The method for preparing the degradable film of the present invention can improve the hydrophilic property of the film. Through DSC testing, it is found that the cellulose-polylactide graft is a good compatibilizer, which can solve the problem of poor compatibility between PBAT and PLA. The mechanical property test results show that the tensile strength, elongation at break, and elastic modulus of the pure PBAT / PLA film are 15.3 Mpa, 851.83%, and 21.2 Mpa respectively. After adding modified nano-calcium carbonate, the mechanical properties decline. However, when adding a compatibilizer cellulose-polylactide graft on the basis of adding 10 wt% calcium carbonate, the results show that the elongation at break of the degradable film is increased by 3.2 times again. The addition of the cellulose-polylactide graft effectively improves the compatibility between the matrixes.

[0019] Third, the degradable film prepared in Example 7 of the present invention is tested by DSC. The toughness of the film is improved, the stiffness of the degradable material is reduced, and the performance of the degradable film is enhanced. In the mechanical property analysis, when considering both high mechanical properties and maximum cost reduction, 10% tapioca starch is selected as the additive and 4 wt% cellulose-polylactide graft is added simultaneously, and the mechanical properties of the degradable film are further improved.

[0020] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the crystal structure diagram of the metal-organic framework material prepared in Example 1 of the present invention;

[0022] Figure 2 It is the crystal structure diagram of the metal-organic framework material prepared in Example 2 of the present invention;

[0023] Figure 3 It is the crystal structure diagram of the metal-organic framework material prepared in Example 3 of the present invention;

[0024] Figure 4 It is the crystal structure diagram of the metal-organic framework material prepared in Example 4 of the present invention;

[0025] Figure 5 It is the infrared spectrum diagram of the metal-organic framework materials prepared in Example 1 and Example 2 of the present invention;

[0026] Figure 6 It is the infrared spectrum diagram of the metal-organic framework materials prepared in Example 3 and Example 4 of the present invention;

[0027] Figure 7Thermogravimetric analysis diagrams of the metal-organic framework materials prepared in Example 1 and Example 2 of the present invention;

[0028] Figure 8 Thermogravimetric analysis diagrams of the metal-organic framework materials prepared in Example 3 and Example 4 of the present invention;

[0029] Figure 9 Surface morphology analysis of the metal-organic framework materials prepared in Example 1 and Example 2 of the present invention;

[0030] Figure 10 1H NMR spectrum of the cellulose-poly(lactide) graft copolymer prepared in Example 5 of the present invention;

[0031] Figure 11 1H NMR spectrum of the cellulose-poly(lactide) graft copolymer prepared in Example 6 of the present invention;

[0032] Figure 12 1H NMR spectrum of the cellulose-poly(lactide) graft copolymer prepared in Example 7 of the present invention;

[0033] Figure 13 Mechanical property diagram of the degradable film prepared in Example 5 of the present invention;

[0034] Figure 14 SEM diagram of the degradable film prepared in Example 5 of the present invention;

[0035] Figure 15 Thermogravimetric diagram of the degradable film prepared in Example 5 of the present invention, where (a) is the cooling curve diagram and (b) is the heating curve diagram;

[0036] Figure 16 Fluorescence diagram of the degradable film prepared in Example 5 of the present invention, where (a) is the fluorescence emission spectrum diagram and (b) is the fluorescence excitation spectrum diagram;

[0037] Figure 17 Contact angle of the degradable film prepared in Example 5 of the present invention;

[0038] Figure 18 Mechanical property diagram of the degradable film prepared in Example 7 of the present invention;

[0039] Figure 19 Contact angle analysis of the degradable film prepared in Example 7 of the present invention;

[0040] Figure 20 Fluorescence analysis of the degradable film prepared in Example 7 of the present invention;

[0041] Figure 21 DSC analysis of the degradable film prepared in Example 7 of the present invention. Detailed implementation manners

[0042] The following further elaborates on the present invention in conjunction with embodiments, so that those skilled in the art can implement it with reference to the text of the specification.

[0043] <Example 1>

[0044] The chemical formula of the metal-organic framework material is {[Ce2(L 2 )(HL 2 )2(H2O)2(H2O)]} n (Ce-MOF-1 prepared in Example 1);

[0045] Preparation method of the metal-organic framework material:

[0046] Weigh the required ligand H2L 2 (0.2 mmol, 0.0464 g, (5-(1-H-imidazolyl) isophthalic acid) and Ce(NO3)3·6H2O (0.1 mmol, 0.0434 g), then place them in a hydrothermal reaction kettle, add 2 mL of absolute ethanol and 4 mL of deionized water, stir for 30 min first, and then place it in an oven at 140 °C for reaction for 72 hours. After the reaction, wash the crystals three times with absolute ethanol. The obtained product is colorless regular square crystals, with a yield of 0.0581 g and a yield of 56.66% (based on Ce 3+ ). Elemental analysis (%): C 33 H 24 N6O 15 Ce (Mr = 1024.82), theoretical values: C, 38.64; H, 2.34; N, 8.19; actual values: C, 38.65; H, 2.36; N, 8.21. Infrared spectrum data: (KBr, cm -1 ): 3624 (w), 3066 (w), 1666 (s), 1619 (s), 1572 (s), 1380 (w) 457 (w).

[0047] <Example 2>

[0048] The chemical formula of the metal-organic framework material is {[Се з (L 2 )4(Η2O) з (СH3COO)]} n (Ce-MOF-2 prepared in Example 2);

[0049] Preparation method of the metal-organic framework material:

[0050] Weigh H2L 2(0.1 mmol, 0.0232 g, (5-(1H-imidazolyl)isophthalic acid)) and Ce(NO3)3·6H2O (0.1 mmol, 0.0434 g) were poured into a hydrothermal reactor, 1 mL of acetonitrile and 9 mL of deionized water were added, stirred for 30 min, then placed in an oven at 170 °C for reaction for 72 hours, filtered and washed three times with the upper pure mother liquor. Finally, colorless square-shaped strip crystals were obtained, with a yield of 0.1236 g and a yield rate of 84.89% (based on Ce 3+ ). Elemental analysis (%): C 46 H 36 Ce3N8O 21 (Mr = 1456.18), theoretical values: C, 37.91; H, 2.47; N, 7.70; actual values: C, 37.92; H, 2.46; N, 6.69. Infrared spectrum data: (KBr, cm -l ) : 3626(w), 3135(w), 3070(w), 1659(s), 1615(s), 1564(s), 1373(w)461(w).

[0051] <Example 3>

[0052] The chemical formula of the metal-organic framework material is {[Eu(HL2)(PTA) 0.5 (DMF)2]·DMF}n (the metal-organic framework material Eu-MOF-1 prepared in Example 3);

[0053] Preparation method of the metal-organic framework material:

[0054] Weigh H2L 2 (0.1 mmol, 0.0232 g), Eu(NO3)3·6H2O (0.1 mmol, 0.0446 g) and terephthalic acid (PTA, 0.1 mmol, 0.16613 g) and place them in a reaction kettle, add 4 mL of DMF, stir for 30 min, then put the reaction kettle into an oven at 120 °C for reaction for 72 h, cool to room temperature, wash 3 times with absolute ethanol, and place it in a vacuum drying oven at 120 °C for drying for 3 h to obtain colorless transparent square-shaped strip crystals, with a yield of 0.0576 g, and the calculated yield rate is 84.33% (based on Eu 3+ ). Elemental analysis (%): C 24 H 29 EuN5O9 (Mr = 683.48), theoretical values: C: 42.14; H: 4.24; N: 10.24; actual values: C: 42.16; H: 4.26; N: 10.22. Infrared spectrum data: (KBr, cm -1 ) :

[0055] 3381(br), 3117(w), 3070(w), 1662(w), 1622(w), 1550(s), 1384(s), 454(s).

[0056] <Example 4>

[0057] The chemical formula of the metal-organic framework material is {[Eu(L 2 )(C2O4) 0.5 (H2O)]}n (the metal-organic framework material Eu-MOF-2 prepared in Example 4);

[0058] Preparation method of the metal-organic framework material:

[0059] Weigh H2L 2 (0.15 mmol, 0.0348 g, (5-(1H-imidazolyl)isophthalic acid)), Eu(NO3)3·6H2O (0.1 mmol, 0.0446 g) and oxalic acid (0.3 mmol, 0.0271 g), place them in a reaction kettle with a capacity of 15 mL, add 10 mL of deionized water, stir for 30 min, then place the reaction kettle in an oven at 160 °C for reaction for 72 h. After the reaction is completed, cool it to room temperature and wash it 3 times with deionized water to obtain pink transparent needle-shaped strip crystals. The yield is 0.0399 g, and the calculated yield is 90.01% (based on Eu 3+ ). Elemental analysis (%) : C 12 H8EuN2O7 (Mr = 444.16), theoretical values: C: 32.42; H: 1.81; N: 6.31; actual values: C: 32.40; H: 1.79; N: 6.30. Infrared spectrum data: (KBr, cm -1 ) :

[0060] 3585(w), 3138(w), 3099(w), 1673(w), 1622(s), 1572(s), 1373(s), 476(s).

[0061] <Example 5>

[0062] Using the metal-organic framework material prepared in Example 1 to prepare a degradable film, the preparation method includes the following steps:

[0063] Step 1: Weigh 0.25 g of cotton nanofibers and 5 g of type B ionic liquid (BmimCl), mix them and pour them into a three-necked flask. React at 80 °C for 2 h, then raise the temperature to 110 °C, add a catalyst (the metal-organic framework material prepared in Example 1) and L-lactide, and react for 8 h (the reaction is carried out under nitrogen protection throughout). After the reaction is completed, use absolute ethanol to remove the unreacted L-lactide and type B ionic liquid, then pour it into dichloromethane and soak for 1.5 h, and dry to obtain a cellulose-polylactide graft. Among them, the mass ratio of cotton fiber to L-lactide is 1:20, and the catalyst dosage is 2 wt% of the total mass of L-lactide;

[0064] Step 2: Weigh PBAT (polybutylene adipate terephthalate) and PLA (polylactic acid) according to a mass ratio of 8:2, and modified nano-calcium carbonate accounting for 10 wt% of the total mass of PBAT and PLA. At 180 °C, put PLA, PBAT and modified nano-calcium carbonate in sequence, mix them evenly, cool to room temperature, add 100 mL of dichloromethane, let it stand for 12 h, stir for 30 min, and then pour it into a petri dish to make a film with a thickness of about 0.3 mm, that is, a degradable film is obtained.

[0065] Among them, the preparation method of the modified nano-calcium carbonate is: prepare a KH570 (γ-methacryloxypropyltrimethoxysilane) silane coupling agent solution (KH570: absolute ethanol = 1:4), then adjust the pH of the solution to 4 - 5 with acetic acid, add calcium carbonate, stir for 0.5 h, filter, and dry to obtain the modified nano-calcium carbonate. The dosage of KH570 in the experiment is 5 wt% of the mass of calcium carbonate.

[0066] <Example 6>

[0067] The degradable film is prepared by the method of Example 5, where the difference is that the catalyst is the metal-organic framework material prepared in Example 2.

[0068] <Example 7>

[0069] Prepare a degradable film with the metal-organic framework material prepared in Example 3. The preparation method includes the following steps:

[0070] Step 1: The reaction was carried out under nitrogen protection throughout the experiment. Weighed 0.25 g of banana cellulose (BNCF) and 5 g of ionic liquid (BmimCl), mixed them, stirred at 80 °C for 2 h, then heated to 110 °C, added 0.0445 g of catalyst (metal-organic framework material prepared in Example 3) and 2.225 g of L-lactide, and reacted for 8 h. After the reaction ended, the product was poured into a 250 mL beaker, then 100 mL of absolute ethanol was poured into the beaker, filtered to remove the absolute ethanol, and then 100 mL of dichloromethane was added and soaked for 2 h. After the washing was completed, the beaker was placed in a fume hood and waited for the dichloromethane to volatilize completely naturally, and then dried to obtain the cellulose-polylactide graft copolymer;

[0071] Step 2: Take a washed and dried beaker with a capacity of 150 mL, fix it on an oil bath pot that has been heated to 190 °C with an iron stand and an iron clamp. Pour 1.7543 g of PLA into the beaker. After it changes from granular to molten state, add 7.071 g of PBAT and 0.3509 g of cellulose-polylactide graft copolymer in sequence, and stir until evenly mixed. After the reaction ends, wait for the beaker to cool to room temperature, add 100 mL of dichloromethane to the beaker, add modified cassava starch, and stir for another 8 h (dichloromethane is extremely volatile. To prevent excessive volatilization of dichloromethane during the dissolution process, it is necessary to seal the beaker mouth with plastic wrap). After the reaction ends, pour it into a petri dish to make a film with a thickness of about 0.4 mm, which is the degradable film.

[0072] Among them, the preparation method of the modified cassava starch is as follows: Add silane coupling agent KH550 (γ-aminopropyltriethoxysilane) and 0.8772 g of cassava starch to the beaker, stir at 100 °C and a rotation speed of 1000 r / min for 20 min. The mass of the silane coupling agent KH550 is 0.03 times the mass of the cassava starch to obtain the modified cassava starch.

[0073] <Example 8>

[0074] The degradable film was prepared by the method of Example 7, wherein the difference is that the catalyst is the metal-organic framework material prepared in Example 4.

[0075] <Result Characterization>

[0076] 1. Crystal Structure Characterization

[0077] 1.1 Crystal structure description of the metal-organic framework material Ce-MOF-1 prepared in Example 1

[0078] It can be seen from the single crystal X-ray diffraction data that the prepared Ce-MOF-1 in the example belongs to the triclinic system, P 1 space group;

[0079] AsFigure 1 As shown in (a), the asymmetric unit of the single crystal contains two Ce(III) ions, one fully deprotonated L 2 ligand, two incompletely deprotonated HL 2 ligands and three coordinated molecules. As Figure 1 shown in (b), the Ce1(III) ion coordinates with O2, O3, O4, O5, O4A, O5A, O14B, O14C (symmetry code A: 1 - x, 1 - y, - z; B: - 1 + x, + y, + z; C: 2 - x, 1 - y, - z) on the ligand L 2 and O1, Ce1A from the coordinated water molecule and the nitrogen atom N2D (symmetry code D: 1 + x, y, - 1 + z) on the coordinated imidazole ring. Ce2(III) coordinates with two oxygen atoms O8, O9 from the coordinated water molecule and O6, O7F, O10, O10E, O11E (symmetry code E: 1 - x, - y, 1 - z), O12F, O13F (symmetry code F: 1 - x, - y, 1 - z) from the L2 ligand and Ce2(III)F. As 2 shown in (c), both Ce1(III) and Ce2(III) are in a 10 - coordinate configuration. Ce1 is connected to Ce1A and Ce2 is connected to Ce2F to form a binuclear structure, which constitutes the three - dimensional space of Ce - MOF - 1. As Figure 1 shown in (d), the pore characteristics of Ce - MOF - 1 are shown in Figure 3 (d). Calculated by the Platon program, the unit cell volume of Ce - MOF - 1 is Figure 1 The pore volume that the guest molecules can pass through in each unit cell is The porosity is 8.7%.

[0080] 1.2 Crystal structure description of the metal - organic framework material Ce - MOF - 2 prepared in Example 2

[0081] Single - crystal X - ray diffraction data of Ce - MOF - 2 show that it belongs to the monoclinic system, space group P21;

[0082] From Figure 2 the smallest structural unit of the crystal in (a), the asymmetric unit contains three Ce(III) ions, four incompletely deprotonated L 2 ligands and three water molecules coordinated with Cel(III) ion, Ce2(III) ion, Ce3(III) ion and one coordinated acetic acid molecule. As Figure 2 shown in (b), the Cel(III) ion coordinates with the L from 2O3, O9, O10A (symmetry code: 1+x, +y, +z), O12A, O18B (symmetry code B: +x, +y, -1+z), O20C (symmetry code C: 1-x, 1 / 2+y, 1-z), O22C on the ligand, and O1 on the coordinated water molecule are coordinated. The Ce2(III) ions are respectively from L 2 O4C, O7C, O11, O13, O14, O15, O19D (symmetry code D: -x, 1 / 2+y, 1-z), O2ID on the ligand, and O16 on the coordinated water molecule are coordinated. The Ce3(III) ions are respectively coordinated with L 2 O3, O4, O6, O7, O8, O9, O15E (symmetry code E: 1-x, -1 / 2+y, I-z), N23F (symmetry code F: +x, +y, -1+z) on the ligand, and O5 from the coordinated water molecule are coordinated. Among them, Cel(III) connects Ce2(III) and Ce3(III) to form a trinuclear cluster structure, which constitutes the three-dimensional space of Ce-MOF-2. As Figure 2 (c) shows, the Cel(III) ion has an 8-coordinate configuration, and the Ce2(III) and Ce3(III) ions both have a 9-coordinate configuration. As Figure 2 (d) shows, the unit cell volume of Ce-MOF-2 calculated by the Platon program is The pore volume that the guest molecules can pass through in each unit cell is The porosity is 4.7%. Compared with Ce-MOF-1, the pore volume that the guest molecules can pass through decreases, mainly due to the end-group blocking effect of acetic acid molecules and the presence of coordinated water molecules.

[0083] 1.3 Crystal structure description of the metal-organic framework material Eu-MOF-1 prepared in Example 3

[0084] It is known from the single-crystal X-ray diffraction data of Eu-MOF-1 that it belongs to the monoclinic system of the P21 / c space group.

[0085] As Figure 3 (a) shows, the asymmetric unit contains one Eu(III) ion, one incompletely deprotonated L 2 ligand, half a deprotonated terephthalic acid molecule, two coordinated DMF molecules and one free DMF molecule. As Figure 3 (b) shows, the Eu1 ion is respectively coordinated with two oxygen atoms O1 and O4 from two DMF molecules, two carboxyl oxygen atoms 02 and 03 of terephthalic acid, and from L 2The carboxyl oxygen atoms O5, O5A (symmetry code A: 1 - x, 1 - y, 1 - z), O6A, O7 (symmetry code: 1 - x, 1 / 2 + y, 3 / 2 - z), O8 (symmetry code: +x, 1 / 2 - y, -1 / 2 + z) of the ligand are coordinated, where the not fully deprotonated L 2 The ligand connects three Eu(III) ions, where one carboxyl atom is monodentate - bridged and the other is bidentate - chelated to connect Eu1(III) and EulA(III), so the not fully deprotonated L 2 The coordination mode of the ligand can be expressed as: (k 0 -k 1 )-(k 1 -k 1 )-μ 3 , Similarly, Eu1(III) and Eu1B(III) (symmetry code B: 2 - x, 1 - y, 1 - z) are respectively bidentate - chelated with the carboxyl oxygen atoms from the terephthalic acid molecule. The coordination mode of the auxiliary ligand terephthalic acid can be expressed as: (k 0 -k 1 )-(k 0 -k 1 )-μ 2 . Among them, Eu1 has a 9 - coordination configuration, and the distance between Eu1 and Eu1A is which is in line with the reported range in the literature. The three - dimensional packing of MOFs is as shown in Figure 1 (c). The terephthalic acid molecule coordinates with Eu(III) ions to form a two - dimensional molecular network, and such two - dimensional molecular networks are further bridged by the not fully deprotonated L 2 to construct a three - dimensional molecular network of MOFs. The pore characteristics of MOFs are as shown in Figure 4 (d). It can be seen from the figure that MOF has relatively large pores. Using computer programs to calculate, the unit cell volume in Eu - MOF - 1 is The pore volume in each unit cell is and the porosity is 49.7%.

[0086] 1.4 Crystal structure description of the metal - organic framework material Eu - MOF - 2 prepared in Example 4

[0087] From the single - crystal X - ray diffraction data of Eu - MOF - 2, it is known that it belongs to the monoclinic system in the same space group as Eu - MOF - 1.

[0088] As shown in Figure 4 (a), there is one Eu(III) ion and one deprotonated L in its asymmetric unit 2The ligands are half of a fully deprotonated oxalic acid molecule and a free water molecule. For clarity, some hydrogen atoms are omitted herein. As Figure 4 (b) shows, the Eu1(I) ion coordinates with O1, O5A (symmetry code A: 1 - x, 1 - y; 1 - z), O6B (symmetry code B: x, 3 / 2 - y, 1 / 2 + z), O7B, O7C (symmetry code C: 1 - x, -1 / 2 + y; 1 / 2 - z) from the L 2 ligand, and N2D (symmetry code D: -1 + x, 3 / 2 - y - 1 / 2 + z) on the imidazole ring of the L 2 ligand, O3 of the oxalic acid molecule, O4E (symmetry code E: -X, 1 - y; 1 - z), and O2 from the coordinated water molecule. The four carboxyl oxygen atoms on the auxiliary ligand oxalic acid molecule are connected to Eul(III) and EulA(II) respectively through monodentate bridging, forming a one-dimensional chain (ID) structure of the MOF. The axial oxygen atoms on the carboxyl group of the L 2 ligand connect three Eu(ID) ions to form its three-dimensional framework (3D). As Figure 4 (c, d) shows, where the Eu(III) ion has a 9-coordinate configuration, Eul(II) and EulA(III) are directly connected to form a binuclear structure of MOF 9, and the distance between Eul(III) and EulA(II) is within the range reported in the literature. The porosity of the MOF cannot be calculated by the Platon program, which may be due to the close-packed ABAB… stacking of the L 2 ligand in the MOF ([[]] Figure 4 c).

[0089] 2. Infrared Analysis

[0090] 2.1 Infrared Characterization of the Metal-Organic Framework Materials Ce-MOF-1 and Ce-MOF-2 Prepared in Examples 1 and 2

[0091] As Figure 5 (a)(b) shows, infrared spectroscopy tests were performed on the ligand H2L 2 , Ce-MOF-1, and Ce-MOF-2 respectively to determine the chemical structure and composition of the single crystal. Through peak comparison and analysis, it can be seen that the signal peak around 1689 cm -1 usually corresponds to C=O. Compared with the C=O bond in the ligand H2L 2 , the peak in Ce-MOF-1 and Ce-MOF-2 decreases and shifts to a lower wavenumber, indicating that protonation has occurred. In addition, the characteristic peak around 1572 cm -1 corresponds to the vibration peak of the benzene ring skeleton C=C bond. The ligand H2L 2 is at 3105, 1720 cm-1 The peaks at

[0092] 2.2. Infrared spectrum of the metal-organic framework material Eu-MOF-1 prepared in Example 3

[0093] As Figure 6 (a) shows, Figure 6 (a) is the infrared spectrum of Eu-MOF-1 and its main ligand H2L 2 . It can be easily seen from the figure that the absorption peak at a wavenumber of 1720 cm -1 is due to the stretching vibration of the C=O bond in the main ligand H2L 2 . In the infrared curve of Eu-MOF-1, we can find that the wavenumber of this peak gradually weakens and moves towards the wavenumber of the absorption peak at 1662 cm -1 . This phenomenon indicates that the carboxyl group in Eu-MOF-1 has been completely deprotonated, and the C=O therein has coordinated with Eu 2+ in a coordination reaction. In the infrared curve of Eu-MOF-1, the absorption peak at a wavenumber of 454 cm -1 should be the coordination absorption peak on the Eu-O bond; the absorption peak at a wavenumber of 1622 cm -1 may be caused by the stretching vibration of the C=C bond in the benzene ring, and the absorption peak at a wavenumber of 3117 cm -1 may be the vibration of the C-H bond in the benzene ring; there is a broad absorption peak at a wavenumber of 3585 cm -1 . However, there are no lattice water molecules and coordinated water molecules in Eu-MOF-1, so this absorption peak can only be the peak caused by the incompletely dried and residual H2O in the Eu-MOF-1 material. Combining the above analysis, the data analysis results in the infrared spectrum of Eu-MOF-1 are generally the same as the above crystal structure data.

[0094] 2.3 Infrared spectrum of the metal-organic framework material Eu-MOF-2 prepared in Example 4

[0095] As Figure 6 (b) shows, Figure 6 (b) is the infrared spectrum of Eu-MOF-2 and its main ligand H2L 2 . It can be easily seen from the figure that the absorption peak at a wavenumber of 1720 cm -1 is due to the main ligand H2L 2caused by the stretching vibration of the C=O bond in it. In the infrared curve of Eu-MOF-2, we can find that the wave number of this peak gradually weakens and moves to a wave number of 1673 cm -1 in the direction. This phenomenon indicates that the carboxyl group in Eu-MOF-2 has been completely deprotonated, and the C=O bond in it has reacted with Eu 2+ coordination reaction. In the infrared curve of Eu-MOF-2, the absorption peak at a wave number of 476 cm -1 should be the coordination absorption peak on the Eu-O bond; the absorption peak at a wave number of 1622 cm -1 may be caused by the stretching vibration of the C=C bond in the benzene ring, and the absorption peak at a wave number of 3138 cm -1 may be the vibration of the C-H bond in the benzene ring; the absorption peak at a wave number of 3585 cm -1 may be the peak caused by the vibration of the O-H bond in the H2O contained in Eu-MOF-2. Combining the above analysis, the data analysis results in the infrared spectrum of Eu-MOF-2 are generally the same as the above crystal structure data.

[0096] 3. Thermal Gravimetric Characterization Analysis

[0097] 3.1 Thermogravimetric analysis of the metal-organic framework material Ce-MOF-1 prepared in Example 1;

[0098] As Figure 7 (a) shows, the water molecules present in the Ce-MOF-1 sample will evaporate and escape due to heat at the beginning of the experiment and lose weight first, manifested as a slow decline in the curve before 100 °C, and the weight loss rate is 4.5 wt%. After that, the curve is relatively flat between 200 and 380 °C, which may be the continuous drying stage before the weight loss of metal Ce-MOF-1. When the temperature rises to 380 °C, Ce-MOF-1 decomposes rapidly, and the weight loss rate of the sample reaches 61.8% at this time, and the weight loss rate of the sample is the fastest at 448 °C.

[0099] 3.2 Thermogravimetric analysis of the metal-organic framework material Ce-MOF-2 prepared in Example 2

[0100] Figure 7 (b) shows the thermogravimetric curve of Ce-MOF-2. The slow decomposition of the sample before 150 °C is also due to the weight loss caused by the evaporation of water molecules. After that, the curve shows a plateau until about 380 °C, and the weight loss rate in this stage is 8.7%. After that is the main decomposition region of Ce-MOF-2, and the curve drops rapidly, and the weight loss rate of the sample reaches 54.8%. Similarly, the weight loss rate is the fastest at about 450 °C. The thermal stability values of the two single crystals reach about 400 °C.

[0101] 3.3 Thermogravimetric analysis of the metal-organic framework material Eu-MOF-1 prepared in Example 3

[0102] As Figure 8 (a) shows, the decomposition of Eu-MOF-1 before about 380 °C is relatively slow and the curve is relatively flat. This may be because the free DMF molecules in the Eu-MOF-1 crystal slowly escape after being heated, causing the mass of Eu-MOF-1 to decrease. Rapid decomposition occurs after 380 °C, and the mass drops rapidly until the entire MOF is broken down and decomposed.

[0103] 3.4 Thermogravimetric analysis of the metal-organic framework material Eu-MOF-2 prepared in Example 4

[0104] As Figure 8 (b) shows, the decomposition of Eu-MOF-2 before about 300 °C is relatively slow and the curve is relatively flat. This may be due to the slow escape of free water molecules and coordinated water molecules in Eu-MOF-2 after being heated. Rapid decomposition occurs after 410 °C, and the mass drops rapidly until the entire Eu-MOF-2 is damaged and decomposed.

[0105] 4. Surface morphology analysis

[0106] 4.1 Morphology analysis of the metal-organic framework materials Ce-MOF-1 and Ce-MOF-2 prepared in Example 1 and Example 2

[0107] The surface morphology of Ce-MOF-1 is as Figure 9 (a) and (b) show. Ce-MOF-1 has regular morphology and relatively small crystal particles, with a size of about 100 nm to 1 μm. The surface morphology of Ce-MOF-2 is as Figure 9 (c) and (d) show. The size of the Ce-MOF-2 crystal is much larger than that of Ce-MOF-1, about 1 mm.

[0108] 5. 1 Analysis of the ¹H-NMR characterization results of the cellulose-polylactide graft copolymer

[0109] 5.1 ¹H-NMR characterization of the cellulose-polylactide graft copolymer prepared in Example 5 and Example 6 1 ¹H-NMR characterization

[0110] As Figure 10 and Figure 11It can be seen that the chemical shift at δ = 1.27 ppm corresponds to the signal peak of the hydrogen (b) on -CH3 in the internal repeating unit of polylactide, and δ = 1.40 ppm and δ = 1.40 ppm correspond to the signal peaks of the hydrogen (b') on the terminal methyl -CH3. The signal peaks appearing between δ = 3.04 - 5.5 ppm belong to the hydrogen on the cellulose glucose unit. Among them, the chemical shifts of the hydrogen on C2, C3, and C6 of the glucose unit are 5.55, 5.45, and 4.33 ppm respectively. When the hydrogen on their hydroxyl -OH is replaced by PLA, the intensity of the peak is significantly lower than that of the hydrogen before substitution.

[0111] Using 1 The grafting rate of PLA can be calculated by the 1H-NMR spectrum. Mark the integral area values of the hydrogen signal peaks on the methyl carbon of PLA and the hydrogen signal peaks on the glucose unit on the spectrum respectively. The ratio of the two is the molar substitution degree of PLA (the number of PLA on each basic glucose structural unit), and based on this, the mass percentage content of PLA in the polymer is calculated. The formula is as follows:

[0112] MS = [I(b + b') / I(O2H + O3H + O6H)] (3.1)

[0113] W PLA = 72MS / (162 + 72MS)*100% (3.2)

[0114] In the formula: 72 g·mol -1 represents the molar mass of the L-lactide repeating unit; 162 g·mol -1 represents the molar mass of the cellulose glucose unit.

[0115] The grafting rates of the two grafted products are calculated by the formula. Among them, the grafting rate of WGLA(1) (the cellulose - polylactide grafted product prepared in Example 6) is 82.63%, and that of WGLA(2) (the cellulose - polylactide grafted product prepared in Example 6) is 47.06%. It can be seen that the grafting effect of the former is better than that of the latter. Therefore, it is used as the compatibilizer for subsequent research.

[0116] 5.2 1H-NMR Characterization of the Cellulose - Polylactide Grafted Product Prepared in Example 7 1 1H-NMR

[0117] As Figure 12 shown is the 1H-NMR spectrum of the graft copolymer Eu - BGLA - 1 (the cellulose - polylactide grafted product prepared in Example 7). The signal peak of the hydrogen (H 1 ) on the -CH3 in the repeating unit of polylactide is at a chemical shift of 1.29 ppm, while the hydrogen (H a ) in the -CH3 on the end group of polylactide is at a chemical shift of 1.39 ppm.a ') signal peak. In addition, the chemical shifts of 5.18 ppm and 5.11 ppm correspond to the hydrogen (H d ) in the repeating unit -CH- of PLA and the hydrogen (H d ') on -CH- in the end group of polylactide, respectively. The signal peaks of H on the cellulose glucose unit will appear between the chemical shifts of 3.05 ppm and 5.6 ppm. The chemical shifts of the hydrogens at the C2, C3, and C6 positions of the glucose unit are 5.54 ppm, 5.45 ppm, and 5.19 ppm, respectively. Some remaining miscellaneous peaks on the spectrum indicate that the catalyst Eu-MOF-1 has been embedded inside the grafted product.

[0118] 6. Analysis of the test results of the degradable film prepared in Example 5

[0119] 6.1 Mechanical property analysis

[0120] As can be seen from Figure 13 (a)(b), the tensile strength of the pure PBAT / PLA (8:2) film is 15.3 MPa, and the elongation at break is 851.83%. After adding calcium carbonate, the mechanical properties of the film gradually decline. The change range of the tensile strength is relatively small, while the elongation at break has decreased sharply; at the same time, it can be seen from Figure 13 (c) that the elastic modulus of the film also increases significantly, and the film tends to transform into rigidity; in Figure 13 (d), it can be seen from the stress-strain diagram that the stress borne by the film decreases continuously after adding different calcium carbonate contents, reducing the toughness of the material. Example 5 selects to add 10 wt% calcium carbonate content after fully considering reducing costs and maintaining good mechanical properties.

[0121] Example 5 prepares a degradable film by adding 4 wt% of the grafted product as a compatibilizer on the basis of adding 10 wt% calcium carbonate. As can be seen from Figure 13(b) In terms of the elongation at break, for the film with the grafted substance added, its elongation at break is increased by 3.2 times compared to the original 10 wt%, and the toughness is increased. This indicates that the grafted substance WGLA (the grafted substance prepared in Example 5) effectively improves the mechanical properties of the film. The reason is that there are problems with poor compatibility between PBAT and PLA themselves, which may form phase separation on the film surface and affect the film quality. With the addition of fillers, the incompatibility between the matrices increases. As one of the compatibilizers, the grafted substance can improve the compatibility between the matrices and make the blending effect better because it promotes the dispersion of cellulose-polylactide grafted substances and calcium carbonate in the PBAT / PLA matrix. In addition, (Ce-MOF-1) crystals are well dispersed in the PBAT / PLA matrix. There are probably two reasons for this. On the one hand, there are van der Waals forces, such as dipole-dipole (Keesom), induced dipole (Deby), and dispersion force (London) interactions between the metal-organic framework material and PBAT / PLA molecules. On the other hand, the porous structure of the metal-organic framework material may lead to the adsorption and diffusion of PBAT / PLA molecules on the metal-organic framework material. Therefore, when using fillers to reduce the production cost of degradable films, the mechanical properties can be improved again by adding grafted substances. Figure 13 Among them, PPC5 indicates that the addition amount of modified nano calcium carbonate is 5 wt%, and PPC 10 indicates that the addition amount of modified nano calcium carbonate is 10 wt%, and PPC 15 indicates that the addition amount of modified nano calcium carbonate is 15 wt%, and PPC 20 indicates that the addition amount of modified nano calcium carbonate is 20 wt%, and PPC 10 W4 represents the degradable film prepared in Example 5 (the same below), and PBAT / PLA represents the film prepared without adding modified calcium carbonate and metal-organic framework materials.

[0122] 6.2 Surface Morphology Analysis

[0123] As Figure 14As shown, the cross-sectional morphology of the film PBAT / PLA (prepared by the method of Example 5, except that modified calcium carbonate and metal-organic framework materials were not added) is relatively flat, smooth and uniform; Figure (b) is the surface morphology of Ce-MOF-1; Figure (c) is the cross-sectional morphology of the film with 10 wt% calcium carbonate added, where the white particles are calcium carbonate, and Figure (d) is the cross-sectional morphology of the composite film with 4% cellulose-polylactide graft copolymer added as a compatibilizer on the basis of adding 10 wt% calcium carbonate. In the figure, white calcium carbonate and rod-shaped Ce-MOF-1 were found at the same time. SEM further confirmed the stability of Ce-MOF-1. Compared with Figure (b), after the grafting reaction, the particle size of Ce-MOF-1 remained unchanged and the surface morphology did not change. It was found from Figure (d) that calcium carbonate adhered to Ce-MOF-1, and SEM further confirmed that Ce-MOF-1 could promote the dispersion of calcium carbonate and the graft copolymer in PBAT / PLA.

[0124] 6.3 Analysis of the Thermodynamic Performance Characterization Results of Degradable Films

[0125] Figure 15 In the figure, (a) corresponds to the cooling curve and (b) corresponds to the heating curve, and the relevant data are shown in Tables 1 and 2. From Figure 15 Tables 1 and 2, it can be seen that although the crystallization enthalpy and melting enthalpy of the degradable films did not show an obvious change pattern, they were all smaller than the values of the original pure PBAT / PLA. However, the crystallization temperature and melting temperature of the films increased with the addition amount of calcium carbonate. The peak value of PBAT showed an obvious increase and tended to move towards the high-temperature region, while PLA basically remained stable. After adding WGLA, the double peaks in the curve of the original 10 wt% calcium carbonate gradually became flat and approached the first single peak, gradually changing from the original sharp peak to a broad peak, and the crystallinity of the film decreased, indicating that WGLA, as a good compatibilizer, improved the compatibility of the PBAT / PLA two-phase interface.

[0126] Table 1 shows the crystallization temperature and enthalpy values of the degradable films

[0127]

[0128] Table 2 shows the melting temperature and enthalpy values of the degradable films

[0129]

[0130]

[0131] 6.4 Analysis of the Fluorescence Performance Characterization Results of Degradable Films

[0132] Figure 16(a) and (b) are the fluorescence spectra of single crystal (Ce-MOF-1 used), WGLA, the degradable film prepared in Example 5, and raw materials PBAT and PLA. It can be seen that the raw material PBAT has a strong fluorescence intensity. Although the fluorescence intensity of WGLA has decreased compared with that of the single crystal, the decrease is not significant and it still has a strong fluorescence effect. The strong fluorescence intensity detected in the raw material PLA is mainly because the PLA used in this experiment has been modified. Based on the comprehensive analysis of the experimental results, the developed composite film still has a good fluorescence intensity. The composite film can convert ultraviolet rays in the sun into visible light, which can effectively promote plant growth, and at the same time is beneficial to extending the service life of the film and can slow down aging to a certain extent.

[0133] Analysis of the contact angle characterization results of the 6.5 degradable film

[0134] Plastic agricultural film, as a greenhouse film, has obvious advantages in aspects such as plant growth due to its high strength, high transparency, and low haze characteristics. Super-hydrophilic films are very suitable for this demand. When the hydrophilicity is lower than 40°, a good anti-fog effect can be achieved. At this time, a water film is formed on the surface of the matrix material, which can prevent light refraction and scattering, reduce crop rot, and improve its quality.

[0135] From Figure 17 it can be seen that the contact angle of the pure PBAT / PLA film is 65°, which belongs to a hydrophilic film. However, due to the weak hydrophilicity of PLA and PBA, the contact angle is relatively large. After adding fillers, the contact angle value continuously increases on the original basis. When the addition amount is 20 wt%, the contact angle reaches 78°, and the hydrophilicity decreases. In the second-stage experiment, with the addition amount of 10 wt% calcium carbonate unchanged, 4% of WGLA is added, and it is seen that the contact angle drops to 61°, a decrease of 14.1%, indicating that the addition of the grafted product improves the hydrophilicity of the film.

[0136] 7. Performance characterization of the degradable film prepared in Example 7

[0137] 7.1 Tensile mechanical property test analysis

[0138] From Figure 18 (a) is the bar chart of the tensile strength of the degradable film. From Figure 18It can be seen that the tensile strength of the PBAT / PLA (8:2) composite film before adding modified cassava starch is very high, about 15.5 MPa. This is because the compatibility between PBAT and PLA is very good, and the resulting composite film has a large tensile strength. However, before adding different amounts of modified cassava starch, the tensile strength gradually decreases. When 5% modified cassava starch is added, the tensile strength is 7.1 MPa, which is 118% lower than that of the 8:2 composite film. As the amount of modified cassava starch increases gradually, the tensile strengths are 6.3 MPa, 4.7 MPa, and 4.1 MPa respectively, which are 144%, 231%, and 279% lower respectively. It can be known that the more modified cassava starch is added, the more the tensile strength decreases. This is because modified cassava starch can reduce the compatibility between PBAT and PLA, making the tensile strength of the composite film lower. Figure 18 (b) is a bar chart of the elongation at break of the degradable film. From Figure 18 (b), it can be seen that the elongation at break of the PBAT / PLA (8:2) degradable film before adding modified cassava starch is very high, 722%. However, after adding different amounts of modified cassava starch, the elongation at break decreases significantly. This is because the toughness of the degradable film becomes smaller after adding modified cassava starch. As the amount of modified cassava starch increases, the elongation at breaks of the degradable film are 231.8%, 212.9%, 82.5%, and 57.3% respectively. It can be known that the more modified cassava starch is added, the smaller the elongation at break of the degradable film, and the smaller the toughness of the degradable film will be. From Figure 18 (a) and Figure 18 (b), it is known that it is more appropriate to add 5% or 10% of modified cassava starch to the degradable film. Since the initial purpose of adding modified cassava starch is to reduce the production cost of the degradable film, and the tensile strength and elongation at break are similar when 5% and 10% of modified cassava starch are added to the degradable film, the optimal addition amount of modified cassava starch should be 10%. Then, when 4 wt% Eu-BGLA (indicating the cellulose-polylactide graft prepared in Example 9) is added to the PBAT / PLA degradable film containing 10% modified cassava starch, both the tensile strength and elongation at break are effectively improved, 7.7 MPa and 464% respectively, which are 22.22% higher in tensile strength and 118% higher in elongation at break than those without adding Eu-BGLA. This is because Eu-BGLA acts as a compatibilizer in the degradable film, promoting the compatibility of the degradable film, so that the tensile strength and elongation at break of the degradable film are improved to a certain extent. Therefore, Eu-BGLA can improve the compatibility of the composite film and increase the toughness of the degradable film.

[0139] 7.2 Contact Angle Test Analysis

[0140] Figure 19It is the contact angle change curve of the degradable film. Five groups of data were measured for each sample, and three similar groups were selected and averaged. From Figure 19 It can be seen that when no filler is added, the measured contact angle of the PBAT / PLA (8:2) composite film is 77°, showing hydrophobicity. After adding 5% of modified cassava starch, the contact angle decreases to a certain extent, and the measured value is 73°. Its hydrophilicity is increased by 5.19% compared with before. This is because cassava starch has hydrophilicity. Adding hydrophilic modified cassava starch to the PBAT / PLA composite film makes the contact angle of the composite film smaller. After adding 10% of modified cassava starch, the measured contact angle is 71°. After adding 15% of modified cassava starch, the measured contact angle is 69°. When adding 20% of modified cassava starch (without cellulose-polylactide graft copolymer), the measured contact angle is 65°. When adding 4wt% of cellulose-polylactide graft copolymer (i.e., the degradable film prepared by the method of Example 7), the measured contact angle drops to 62°, which is 4.61% lower than that before adding cellulose-polylactide graft copolymer. The decrease in the contact angle indicates that the hydrophilicity of the degradable film is enhanced. Since the cellulose-polylactide graft copolymer shows hydrophilicity, adding the cellulose-polylactide graft copolymer can improve the hydrophilicity of the degradable film, enabling the composite film to play a certain role when applied in the agricultural field.

[0141] 7.3 Fluorescence analysis of degradable films

[0142] Figure 20 (a) is the emission spectrum diagram of the degradable film, Figure 20(b) is the excitation spectrum of the degradable film. From the figure, it can be seen that when 5% of modified cassava starch is added to the degradable film, the emission wavelength is 451 nm, the fluorescence intensity is 269.1 a.u., the excitation wavelength is 382 nm, and the fluorescence intensity is 264.5 a.u.; when 10% of modified cassava starch is added, the emission wavelength is 451 nm, the fluorescence intensity is 190 a.u., the excitation wavelength is 379 nm, and the fluorescence intensity is 192.2 a.u.; when 15% of modified cassava starch is added, the emission wavelength is 451 nm, the fluorescence intensity is 185.2 a.u., the excitation wavelength is 382 nm, and the fluorescence intensity is 185.5 a.u.; when 20% of modified cassava starch is added, the emission wavelength is 451 nm, the fluorescence intensity is 182 a.u., the excitation wavelength is 383 nm, and the fluorescence intensity is 181 a.u. (in the above experiments of changing the content of modified cassava starch, no cellulose-polylactide graft was added); when 4 wt% of Eu-BGLA is added to the degradable film (the degradable film prepared in Example 9), the emission wavelength is 460 nm, the fluorescence intensity is 91.24 a.u., the excitation wavelength is 378 nm, and the fluorescence intensity is 91 a.u.; the emission wavelength of the raw material PBAT is 441 nm, the fluorescence intensity is 168.2 a.u., the excitation wavelength is 363 nm, and the fluorescence intensity is 164.3 a.u.; for comparison, we also measured the blend of PBAT and PLA sold on the market, with an emission wavelength of 463 nm, a fluorescence intensity of 21.98 a.u., an excitation wavelength of 386 nm, and a fluorescence intensity of 22.08 a.u.; the emission wavelength of Eu-BGLA is 448 nm, the fluorescence intensity is 11.59 a.u., the excitation wavelength is 386 nm, and the fluorescence intensity is 22.08 a.u. From this, it can be obtained that the intensity data gap between the emission spectra and excitation spectra of the above materials is within a reasonable range, so the above data is reasonable. From the figure, it can be seen that when only 5% of modified cassava starch is added, its fluorescence intensity is very high and the fluorescence effect is very good. This may be because the modified cassava starch itself has a certain fluorescence intensity. Therefore, the blend of 5% of cassava starch and PBAT / PLA enhances its fluorescence. All the degradable films obtained in this experiment have fluorescence effects and can be used for drug loading and drug targeting research in the medical field. The fluorescence effect can be used to track the direction of drugs.

[0143] 7.4 DSC Analysis

[0144] Figure 21 (a) is the crystallization peak of the degradable film, Figure 21 (b) is the melting peak of the degradable film. From Figure 21 the curve analysis, the data table in Table 3 is obtained. From Figure 21(a) It can be seen that the degradable crystalline peaks of PBAT / PLA (8:2) are two, which are the crystalline peaks of PBAT and PLA respectively. After adding 5% modified cassava starch, there are still two crystalline peaks. Moreover, the crystalline peak of PLA becomes flatter and flatter, the crystalline peak of PBAT becomes steeper and steeper, and also shifts a lot to the right. This may be because with the addition of modified cassava starch, the compatibility between PBAT and PLA is enhanced, the crystallization ability is improved, and the crystallization rate of the PBAT / PLA blend is accelerated. Therefore, the two crystalline peaks will get closer and closer. With the gradual increase of cassava starch, the crystalline peak of PLA becomes flatter and flatter until it disappears. At this time, the crystalline peak is the crystalline peak of the PBAT / PLA blend. This may be because with the gradual increase of cassava starch, the increase of molecular hydrogen bonds, the increase of the mixing degree of the blend system, and the increase of viscosity, the two crystalline peaks of its cooling curve gradually merge into one crystalline peak. After adding 4wt% Eu-BGLA (the degradable film prepared in Example 7), compared with the curve without adding 4wt% Eu-BGLA, ΔH C has a certain decrease, indicating that its crystallization ability is enhanced.

[0145] It can be seen from Figure (b) that the melting peaks of the composite film of PBAT / PLA (8:2) are two, which are the melting peaks of PBAT and PLA respectively, and the peaks are relatively flat. After adding 5% modified cassava starch, the melting peaks become steeper. With the gradual increase of modified cassava starch, the peak value of the melting peak changes little, and its ΔH m has a certain degree of increase, indicating that the modified cassava starch reduces the toughness of the composite film. After adding 4wt% Eu-BGLA (the degradable film prepared in Example 7), the melting peak becomes very flat, and ΔH m decreases, indicating that Eu-BGLA increases the toughness and compatibility of the degradable film. From this, it can be obtained that Eu-BGLA reduces the crystallinity of the degradable material and enhances the performance of the degradable film.

[0146] Table 3 shows the DSC data of the degradable film

[0147]

[0148] Although the embodiments of the present invention have been disclosed as above, it is not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the examples shown and described here.

Claims

1. A metal-organic framework material, characterized in that, The chemical formula of the metal-organic framework material is {[Ce2(L 2 )(HL 2 )2(H2O)2(H2O)]} n 、{[Ce з (L 2 )4(H2O) з (CH3COO)]} n 、 {[Eu(HL2)(PTA) 0.5 (DMF)2]·DMF} n 、 or {[Eu(L 2 )(C2O4) 0.5 (H2O)]} n 。 2. The preparation method of the metal-organic framework material according to claim 1, characterized in that The metal-organic framework material is prepared by a hydrothermal method using a ligand and a metal salt as raw materials. Among them, the ligand is (5-(1H-imidazolyl)isophthalic acid, and the metal salt is Ce(NO3)3·6H2O or Eu(NO3)3·6H2O.

3. The application of the metal-organic framework material according to claim 1, characterized in that, The metal-organic framework material is used for preparing a modified degradable PBAT / PLA film.

4. The application of the metal-organic framework material according to claim 3, characterized in that, Preparation method of the degradable PBAT / PLA film: Step 1: Using cellulose and L-lactide as raw materials and the metal-organic framework material as a catalyst to prepare a cellulose-polylactide graft. Among them, the cellulose is cotton nanofiber or banana cellulose; Step 2: Using the cellulose-polylactide graft, polylactic acid, poly(butylene adipate-co-terephthalate), and an additive as raw materials to obtain a degradable film. Among them, the additive is modified nano calcium carbonate or modified cassava starch.

5. The application of the metal-organic framework material according to claim 4, wherein The preparation method of the modified nano calcium carbonate is: first prepare a mixed solution of a silane coupling agent and absolute ethanol, then adjust the pH of the mixed solution to 4-5 using acetic acid, then add calcium carbonate and stir for 0.5 h, filter and dry to obtain the modified nano calcium carbonate.

6. The application of the metal-organic framework material according to claim 4, wherein The preparation method of the modified cassava starch is: add a silane coupling agent and cassava starch to a beaker and stir at 100 °C for 20 min to obtain the modified cassava starch.

7. The application of the metal-organic framework material according to claim 4, characterized in that, In Step 1, the dosage of the metal-organic framework material is 1-3% of the total mass of L-lactide.

8. The application of the metal-organic framework material according to claim 4, characterized in that, In Step 2, the addition amount of the cellulose-polylactide graft is 2-6 wt% of the total mass of polylactic acid and poly(butylene adipate-co-terephthalate).

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