Process for the preparation of copper-based coordination polymer catalysts with catalytic ring-opening polymerization

Abstract

This invention relates to a method for preparing copper-based coordination polymer catalysts capable of catalyzing ring-opening polymerization. The method describes the preparation and application of two copper-based coordination polymer catalysts capable of catalyzing ring-opening polymerization. The copper-based coordination polymer catalysts of this invention use ligands L1 and L2, obtained by reacting 1-(3-aminopropyl)imidazolium with o-vanillin and 5-chlorosalicylaldehyde, respectively, as ligands. These ligands are then reacted with copper salt CuCl2·2H2O. By changing the reaction conditions, catalysts Cu-L1 and Cu-L2 are obtained through hydrothermal (solvothermal) synthesis and dehydration condensation. The two novel catalysts have well-defined structures and are stable to water and air. They exhibit excellent catalytic activity in the ring-opening polymerization of lactide without the need for solvents or co-catalysts, and the post-processing steps are simple.

Description

Technical Field

[0001] This invention relates to a method for preparing a polymer catalyst, and more particularly to a method for preparing a copper-based coordination polymer catalyst capable of catalyzing ring-opening polymerization. Technical Background

[0002] Schiff base ligands are frequently used to construct diverse coordination polymers with metal centers due to their easily modifiable structures and ability to coordinate with transition metal ions. They also generally exhibit good structural stability in catalytic reactions, enabling highly efficient catalysis under relatively mild reaction conditions. With the continuous development of coordination chemistry and polymer catalysis research, novel metal catalytic materials based on Schiff base ligands are constantly being developed, and their catalytic applications are continuously expanding. In addition to traditional catalytic conversions, they also demonstrate excellent catalytic potential in areas such as ring-opening polymerization of cyclic ester monomers and the controlled synthesis of functional polymers.

[0003] Copper-based catalytic systems have attracted widespread attention in the field of catalysis due to their advantages such as low raw material cost, good biocompatibility, and environmental friendliness. They have been applied to various reaction types, including polymerization catalysis and oxidative coupling, becoming an important research direction to replace noble metal catalytic systems. The ring-opening polymerization of lactide is the core reaction for preparing biodegradable polylactic acid (PLA) materials. This reaction achieves chain growth by catalytically breaking the lactone bonds in the lactide ring. The prepared PLA materials exhibit good biodegradability and biocompatibility, and have significant application value in fields such as biopharmaceutical carriers, environmentally friendly polymer materials, and biodegradable packaging products. Developing efficient and mild Schiff base copper-based coordination polymer catalytic systems is of significant research and application value for achieving the green and controllable synthesis of PLA materials. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a copper-based coordination polymer catalyst with catalytic ring-opening polymerization. In this method, two copper-based coordination polymers with catalytic ring-opening polymerization properties undergo a highly efficient catalytic ring-opening polymerization reaction of lactide monomer under the action of a catalyst. This polymerization process is a key reaction in the synthesis of biodegradable polylactic acid materials, the preparation of green polymer materials, and the development of biomedical carrier materials. The method is simple, structurally stable, and exhibits excellent catalytic activity during the catalytic process.

[0005] The objective of this invention is achieved through the following technical solution: A method for preparing copper-based coordination polymer catalysts capable of catalyzing ring-opening polymerization reactions is disclosed. This method includes the preparation of two types of one-dimensional copper-based coordination polymer catalysts, and the steps are as follows: a) Preparation of Schiff base-imidazolium ligands: 1-(3-aminopropyl)imidazolium solid was dissolved in ethanol solution, and o-vanillin dissolved in ethanol was slowly added dropwise. After the addition, the mixture was stirred at room temperature for 1 h to obtain L1 ligand; L2 ligand was prepared by the same method. b) Preparation of one-dimensional copper-based coordination polymer catalyst: CuCl2·2H2O and L1 were dissolved in a 1:1 ratio in a mixed solution of DMSO and distilled water. After ultrasonic oscillation at room temperature for 5 min, the solution was transferred to a hydrothermal reactor. The temperature was controlled by a program, and the reaction was carried out for 3 days. After cooling to room temperature, Cu-L1 was obtained. The preparation method of Cu-L2 was the same as above, except that the reaction solvent was replaced with a mixed solution of ethanol and water. The two one-dimensional copper-based coordination polymer catalysts are prepared by reacting CuCl2·2H2O as a precursor with ligands L1 and L2 obtained by reacting 1-(3-aminopropyl)imidazolium with o-vanillin and 5-chlorosalicylaldehyde, respectively. Catalysts Cu-L1 and Cu-L2 are then synthesized via dehydration condensation using a hydrothermal (solvothermal) synthesis technique by changing the reaction conditions. The general structural formulas of the two one-dimensional copper-based coordination polymer catalysts are shown in the figure below.

[0006] The method for preparing a copper-based coordination polymer catalyst capable of catalyzing ring-opening polymerization is described above. The coordination polymer was tested using L-lactide (L-LA) as a substrate to perform lactide ring-opening polymerization on two catalysts. Under solvent-free and co-catalyst-free conditions, the catalyst-lactide ratio was 1:50, and the reaction temperature was 160℃. The catalytic conversion rate of Cu-L1 catalyst was 99%, and that of Cu-L2 catalyst was 92.6%. The different ligand substituents in the two coordination polymers have different effects on the catalytic performance.

[0007] The advantages and effects of this invention are: 1. The two one-dimensional copper-based coordination polymer catalysts of this invention both use CuCl2·2H2O as a precursor and 1-(3-aminopropyl)imidazolium reacting with o-vanillin and 5-chlorosalicylaldehyde to obtain products L1 and L2 as ligands for the reaction. Catalysts Cu-L1 and Cu-L2 are synthesized via a hydrothermal method. The choice of ligand substituents in the coordination polymer affects the catalytic ring-opening polymerization conditions of lactide.

[0008] 2. The two one-dimensional copper-based coordination polymer catalysts have well-defined structures and should have excellent catalytic effects on the ring-opening polymerization of lactide. Moreover, they are simple to process and are a class of lactide ring-opening polymerization catalysts with application value. Detailed Implementation

[0009] The present invention will be described in detail below with reference to embodiments: This invention relates to a copper-based coordination polymer catalyst capable of catalyzing the ring-opening polymerization of lactide, and its preparation method and reaction conditions are as follows.

[0010] a) Preparation of Schiff base-imidazolium ligand.

[0011] 1-(3-aminopropyl)imidazolium solid was dissolved in ethanol solution, and o-vanillin dissolved in ethanol was slowly added dropwise. After the addition, the mixture was stirred at room temperature for 1 h to prepare L1 ligand.

[0012] The preparation method for L2 ligands is the same as above.

[0013] b) Preparation of one-dimensional copper-based coordination polymer catalysts.

[0014] CuCl₂·2H₂O and L₁ were dissolved in a 1:1 ratio in a mixed solution of DMSO and distilled water. After ultrasonic vibration at room temperature for 5 min, the solution was transferred to a hydrothermal reactor. The reaction was carried out under programmed temperature control for 3 days, and then cooled to room temperature to obtain Cu-L₁.

[0015] The preparation method of Cu-L2 is the same as above, except that the reaction solvent is replaced with a mixed solution of ethanol and water.

[0016] This invention relates to a copper-based coordination polymer catalyst for the ring-opening polymerization of lactide. The catalytic performance of the synthesized catalysts was tested. The effects of temperature and catalyst dosage on the ring-opening polymerization of lactide catalyzed by copper-based catalysts were investigated. The results showed that both coordination polymers exhibited catalytic activity, with the Cu-L1 catalyst showing the highest activity, achieving a catalytic conversion rate of 99%.

[0017]

[0018] The two novel one-dimensional copper-based coordination polymer catalysts of this invention both use CuCl2·2H2O as a precursor and react 1-(3-aminopropyl)imidazolium with o-vanillin and 5-chlorosalicylaldehyde, respectively, using L1 and L2 as ligands. By changing the reaction conditions, catalysts Cu-L1 and Cu-L2 are obtained through hydrothermal (solvothermal) synthesis via dehydration condensation. The choice of ligand substituents in the coordination polymer affects the catalytic conditions for the ring-opening polymerization of lactide. Cu-L1 exhibits the highest activity, with a catalytic conversion rate of 99%, indicating that this type of catalyst is a valuable catalyst for the ring-opening polymerization of lactide.

Claims

1. A process for the preparation of a copper-based coordination polymer catalyst having catalytic ring-opening polymerization activity, characterized in that, The method comprises preparation of two one-dimensional copper-based coordination polymers catalysts, steps as follows: a) Preparation of Schiff base-imidazole ligand: 1-(3-aminopropyl) imidazole solid is dissolved in ethanol solution, and o-vanillin dissolved in ethanol is slowly added dropwise, after dropwise addition, the reaction is stirred at room temperature for 1h to obtain L1 ligand; the preparation method of L2 ligand is the same as above; b) Preparation of one-dimensional copper-based coordination polymer catalyst: CuCl2·2H2O and L1 are dissolved in a mixed solution of DMSO and distilled water in a proportion of 1:1, and after ultrasonic oscillation at room temperature for 5min, it is transferred into a hydrothermal reaction kettle; after programmed temperature control and reaction for 3d, it is cooled to room temperature to obtain Cu-L1; the preparation method of Cu-L2 is the same as above, wherein the reaction solvent is changed to a mixed solution of ethanol and water; The two one-dimensional copper-based coordination polymer catalysts are prepared by taking CuCl2·2H2O as a precursor, and reacting with ligands L1 and L2 obtained by reacting 1-(3-aminopropyl) imidazole with o-vanillin and 5-chlorosalicylaldehyde, respectively, and by changing the conditions in the reaction process, and by hydrothermal (solvothermal) synthesis technology to obtain catalysts Cu-L1 and Cu-L2; the structural general formula of the two one-dimensional copper-based coordination polymer catalysts is shown in the following figure: 。 2. The process for the preparation of copper-based coordination polymer catalysts with catalytic ring-opening polymerization according to claim 1, characterized in that, The coordination polymers are tested for lactide ring-opening polymerization reaction by taking L-lactide (L-LA) as a substrate; under the conditions of no solvent and no auxiliary catalyst, the ratio of catalyst to lactide is 1:50, and the reaction temperature is 160℃; the catalytic conversion rate of Cu-L1 catalyst is 99%, and the catalytic conversion rate of Cu-L2 catalyst is 92.6%. The different substituents of the ligands in the two coordination polymers have different effects on the catalytic performance.

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