Preparation method of photoresponsive acylhydrazone covalent organic framework and application of the photoresponsive acylhydrazone covalent organic framework in adsorption and separation of rare earth ions

Abstract

The application discloses a preparation method of a photoresponsive acylhydrazone covalent organic framework and application of the photoresponsive acylhydrazone covalent organic framework in adsorption and separation of rare earth ions, and belongs to the technical field of environmental protection. 2,5-diethoxybenzene-1,4-bis(formylhydrazine) and trialkyl aldehyde are reacted through a Schiff base reaction to prepare an acylhydrazone covalent organic framework; the acylhydrazone covalent organic framework takes an acylhydrazone functional group with photoresponsive performance as a connecting unit, the acylhydrazone functional group of the acylhydrazone covalent organic framework is subjected to E-Z isomerization under the action of 365 nm ultraviolet light, and the photoresponsive acylhydrazone covalent organic framework after the action of ultraviolet light can be used for efficient adsorption and separation of rare earth ions. The photoresponsive acylhydrazone covalent organic framework prepared by the method has simple preparation, high crystallinity, superior photoresponsive isomerization performance, and superior adsorption and separation performance for rare earth ions, and can be used as an efficient adsorbent for low-concentration rare earth tail water.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental protection, and particularly relates to a preparation method of a light-responsive acylhydrazone covalent organic framework and application thereof to adsorption and separation of rare earth ions. BACKGROUND

[0002] With the increasing pressure of resources and environment, it is of great scientific value and practical significance to further improve the level of green and efficient development and utilization of rare earth resources and to carry out research on new intelligent rare earth separation technology based on solid-liquid separation methods. Intelligent response materials are a class of functional materials that can undergo chemical / physical response under external stimuli such as light stimuli. These dynamic, reversible and adaptive characteristics make them have good application prospects in various frontier fields such as separation sensing, optoelectronic devices, information storage, biomedicine, etc. (Yin, Y.; Rogers, J. A., Introduction: smart materials. Chem. Rev. 2022, 122 (5), 4885-4886. In general, the current application of intelligent response materials in the field of rare earth separation is less researched, and the materials are mainly composed of relatively disordered amorphous materials such as aerogels, composite gels and polymers. Due to the disordered distribution of stimulus response functional groups, there are problems such as slow response speed, low energy conversion efficiency and lack of rational analysis and design based on clear structure (Xu, T.; Zheng, X.; Zhang, X.; Li, G.; Mei, J.; Li, Z., Construction of smart photo-responsive imprinted composite aerogel and its selective adsorption for recovery of rare earth dysprosium ions. Sep. Purif. Technol. 2023, 324 , 124618.; Li, G.; Zheng, X.; Xu, T.; Zhang, X.; Ji, B.; Xu, Z.; Bao, S.; Mei, J.; Li, Z., Preparation of imprinted bacterial cellulose aerogel with intelligent modulation of thermal response stimulation for selective adsorption of Gd(III) from wastewater. Environ.Sci.&Pollut. Res. 2023, 30 (60), 125806-125815. Covalent organic frameworks (COFs) are a class of organic porous crystalline materials formed by stable covalent bonds between organic building blocks. Due to their regular pore structure, large specific surface area, low density, and adjustable surface functional groups, COFs are an ideal platform for the preparation of various smart response materials. Among them, light-stimulated smart COFs have the advantages of adjustable pore size, dynamic light response, and high selectivity for target metal ions, and have great application prospects in the field of metal ion separation (Yin, C.; Zhang, Z.; Si, Z.; Shi, X.; Wang, Y., Smart covalent organic frameworks with intrapore azobenzene groups for light-gated ion transport. Chem. Mater. 2022, 34 (20), 9212-9220.; Ren, L.; Chen, J.; Han, J.; Liang, J.; Wu, H., Biomimetic construction of smart nanochannels in covalent organic framework membranes for efficient ion separation. Chem. Eng. J. 2024,482, 148907. However, as of now, there have been no related research reports on light-stimulated smart COFs materials in the field of rare earth separation. Designing and synthesizing light-responsive COFs for efficient adsorption and separation of rare earth ions remains a major difficulty. SUMMARY

[0003] The application aims to provide a preparation method of a photoresponsive acylhydrazone covalent organic framework and an application thereof in adsorbing and separating rare earth ions. The application prepares an acylhydrazone covalent organic framework COF-DEH-Tb (E) through Schiff base reaction between 2,5-diethoxybenzene-1,4-bis(formylhydrazine) (DEH) and tri-aldehyde benzene (Tb). The COF-DEH-Tb (E) is connected by acylhydrazone functional groups, has superior photoresponsive performance and can occur E-Z isomerization under ultraviolet light irradiation. After isomerization, the material COF-DEH-Tb (Z) has a reduced pore size, thereby constructing a novel rare earth ion capture nanochannel in the material, so that the COF-DEH-Tb (Z) under photoresponse has excellent adsorption and separation performance for rare earth ions, and the photoresponsive COF-DEH-Tb (Z) has the highest distribution coefficient for Sm 3+ Therefore, the photoresponsive COF-DEH-Tb (Z) can be used for efficient adsorption and separation of rare earth ions in mine tail water.

[0004] The application provides a preparation method of a photoresponsive acylhydrazone covalent organic framework, comprising:

[0005] The acylhydrazone covalent organic framework is treated by ultraviolet light to obtain a photoresponsive acylhydrazone covalent organic framework.

[0006] The acylhydrazone covalent organic framework is prepared through Schiff base reaction by taking 2,5-diethoxybenzene-1,4-bis(formylhydrazine) and tri-aldehyde benzene as raw materials.

[0007] Further, the ultraviolet light treatment adopts ultraviolet light with a wavelength of 365 nm.

[0008] Further, the ultraviolet light power is 288 mW / cm 2 , and the light treatment duration is 10-100 h.

[0009] Further, the preparation method of the acylhydrazone covalent organic framework comprises:

[0010] 1) 2,5-diethoxybenzene-1,4-bis(formylhydrazine) and tri-aldehyde benzene are taken as raw materials, a solvent is added, and ultrasonic is mixed to obtain a reaction solution.

[0011] 2) The obtained reaction solution is degassed through freeze-thaw cycle, sealed by flame and heated at 100-200 DEG C for 1-5 days, and then the precipitate is collected, washed and dried to obtain the acylhydrazone covalent organic framework.

[0012] Further, the mass ratio of 2,5-diethoxybenzene-1,4-bis(formylhydrazine) to tri-aldehyde benzene in step 1) is (1-2):1.

[0013] Further, the solvent in step 1) is composed of 1,4-dioxane, 1,3,5-trimethylbenzene and acetic acid in a volume ratio of (1-5):(5-15):1; the concentration of the acetic acid is 6 M.

[0014] The application also provides application of the photoresponsive acylhydrazone covalent organic framework obtained by the preparation method in adsorption and separation of rare earth ions.

[0015] Further, the rare earth ions are at least one of La 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3 + , Tm 3+ , Yb 3+ , Lu 3+ , Y 3+ .

[0016] Compared with the prior art, the application has the following beneficial effects:

[0017] (1) The photoresponsive acylhydrazone covalent organic framework has high crystallinity and simple preparation method.

[0018] (2) The acylhydrazone covalent organic framework prepared by the application has excellent photoresponsive performance and can undergo E-Z isomerization under the action of ultraviolet light.

[0019] (3) The photoresponsive acylhydrazone covalent organic framework prepared by the application has a reduced pore size, can construct a novel rare earth ion capture nanochannel in the material, and makes the photoresponsive COF-DEH-Tb (Z) have excellent adsorption and separation performance for rare earth ions.

[0020] (4) The photoresponsive acylhydrazone covalent organic framework prepared by the application has the highest distribution coefficient for Sm 3+ .

[0021] (5) The photoresponsive acylhydrazone covalent organic framework prepared by the application can realize efficient adsorption and separation of rare earth ions in mine tail water and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a preparation process schematic diagram of COF-DEH-Tb (E).

[0023] Figure 2is the experimental test PXRD pattern of DEH, Tb and COF-DEH-Tb (E).

[0024] Figure 3 is the infrared spectrum of DEH, Tb and COF-DEH-Tb (E).

[0025] Figure 4 is the infrared spectrum of COF-DEH-Tb (E) and COF-DEH-Tb (Z).

[0026] Figure 5 is the E-Z isomer schematic of the acylhydrazone functional group (a) and the E-Z isomer schematic of COF-DEH-Tb (b).

[0027] Figure 6 is the adsorption capacity of COF-DEH-Tb (E) and COF-DEH-Tb (Z) for rare earth ions.

[0028] Figure 7 is the distribution coefficient of COF-DEH-Tb (Z) for rare earth ions. DETAILED DESCRIPTION

[0029] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with examples. If specific conditions are not indicated in the examples, conventional conditions or the conditions suggested by the manufacturers are used. If the manufacturers of the reagents or instruments are not indicated, they are all conventional products that can be purchased in the market.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0031] Example 1: Preparation and characterization of acylhydrazone covalent organic framework COF-DEH-Tb (E)

[0032] A 15 mL Pirex tube was charged with 2,5-diethoxybenzene-1,4-di(formhydrazide) (DEH, 18 mg), triformylphenyl (Tb, 7 mg), 1,4-dioxane (0.25 mL) and 1,3,5-trimethylbenzene (0.75 mL), sonicated for 10 min, and then 6 M acetic acid solution (0.10 mL) was added to give a reaction mixture; the Pirex tube containing the reaction mixture was degassed by three freeze-pump-thaw cycles, flame sealed and heated in an oven at 120 °C for 3 days, cooled and filtered, the white solid product was washed with anhydrous tetrahydrofuran (THF), acetone several times, the solid was collected and dried under vacuum at 60 °C for 12 h to give acylhydrazone covalent organic framework (COF-DEH-Tb (E)).

[0033] Figure 1 is a schematic diagram of the preparation process of acylhydrazone covalent organic framework COF-DEH-Tb (E).

[0034] The crystal structure of acylhydrazone covalent organic framework COF-DEH-Tb (E) was characterized by powder X-ray diffraction (PXRD) technology. Figure 2 is the experimental test PXRD diagram of DEH, Tb and COF-DEH-Tb (E). The crystallization of COF-DEH-Tb (E) was determined by powder X-ray diffraction, and COF-DEH-Tb (E) was analyzed by Material Studio simulation software. The peaks at 3.47°, 6.93°, 9.23°, 26.71° correspond to the 100, 200, 210, 003 crystal planes of COF-DEH-Tb (E), respectively, indicating that the synthesized material has high crystallinity. At the same time, there is no diffraction peak of reaction monomer DEH, Tb in the PXRD of COF-DEH-Tb (E), indicating that the reaction proceeds completely in the process of material synthesis.

[0035] Figure 3 is the infrared spectrum of DEH, Tb and COF-DEH-Tb (E). From Figure 3 it can be seen that the vibration peak at 1629 cm -1 comes from the C=N double bond vibration in COF-DEH-Tb (E). In addition, the infrared peak near 1658 cm -1 comes from the C=O double bond vibration in COF-DEH-Tb (E), while the C=O double bond vibration peak in the reaction monomer DEH appears at 1641 cm -1nearby. The red shift of the corresponding functional group in the material is due to the resonance of the C=O double bond and the imine bond in COF-DEH-Tb (E), which causes the vibration of the C=O double bond to weaken. The vibration of the C=O double bond in the reaction monomer Tb occurs at 1694 cm -1 nearby, the above infrared peak is not observed in COF-DEH-Tb (E), which indicates the completeness of the chemical reaction during the synthesis of the material. Through the above characterization, it is shown that the acylhydrazone covalent organic framework is successfully prepared.

[0036] The characterization results of PXRD, infrared spectrum and the like prove that the acylhydrazone covalent organic framework COF-DEH-Tb (E) with high crystallinity and acylhydrazone as the connecting unit is successfully prepared.

[0037] Example 2: Preparation and characterization of the photoresponsive acylhydrazone covalent organic framework COF-DEH-Tb (Z)

[0038] The COF-DEH-Tb (E) is irradiated by a 365 nm ultraviolet LED lamp, and it is found that the color of the material changes from white to yellow. The reason for the change is that the acylhydrazone functional group in COF-DEH-Tb (E) undergoes E-Z isomerization under ultraviolet light irradiation, causing the material's light absorption performance to change, thereby causing the color to change. Figure 4 is the infrared spectrum of COF-DEH-Tb (E) and COF-DEH-Tb (Z). From Figure 4 it can be seen that after irradiation, the peak intensity of COF-DEH-Tb (Z) at 1535 cm -1 nearby sharply decreases, because the N-H vibration in the material is broken during the E-Z configuration change. Through the above experiment, it is shown that the material undergoes E-Z isomerization under ultraviolet light irradiation, which proves the successful preparation of the photoresponsive acylhydrazone covalent organic framework COF-DEH-Tb (Z) synthesized by the present application.

[0039] Figure 5 (a) is a schematic diagram of E-Z isomerization of the acylhydrazone functional group under ultraviolet light irradiation, from Figure 5 (a) it can be seen that along with the process of excited-state intramolecular proton transfer (ESIPT), the configuration of the acylhydrazone functional group changes (E-Z isomerization), that is, the hydrogen atom is transferred from the hydrogen donor (N-H) to the hydrogen acceptor (ether oxygen group). Figure 5(b) is an E-Z isomerization schematic diagram of COF-DEH-Tb. COF-DEH-Tb (E) in E configuration, in which the hydrogen atom on N-H can form intramolecular hydrogen bond with the oxygen on alkoxy group, thus forming a six-membered ring form. After photoisomerization occurs, the proton acceptor (i.e. the oxygen in alkoxy group) can obtain a hydrogen atom from the nearby N-H and form a new six-membered ring with the nearby nitrogen atom. At the same time, after E-Z isomerization of COF-DEH-Tb (E), the Z isomer can be stabilized by non-covalent interactions in COF-DEH-Tb (Z), such as π···π interactions, intralayer hydrogen bonds, interlayer hydrogen bond interactions, etc. After isomerization, COF-DEH-Tb (Z), the E-Z isomerization of acylhydrazone functional group causes the contraction of the pore structure of the material, and the pore size becomes smaller, thus constructing a new type of rare earth ion capture nanochannel in the material, and enhancing the affinity of the material for rare earth ions.

[0040] Example 3: Adsorption and separation application of photoresponsive acylhydrazone covalent organic framework COF-DEH-Tb (Z) for rare earth ions

[0041] The adsorption and separation performance of COF-DEH-Tb (E) and COF-DEH-Tb (Z) for rare earth ions (La 3+ , Ce 3 + , Pr 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , Lu 3+ , Y 3+ ) were investigated. In 10 mL of rare earth mixed solution, 5 mg of COF-DEH-Tb (E) and COF-DEH-Tb (Z) were added respectively, stirred for 12 h, filtered with 0.22 μm microporous filter membrane, and the content of rare earth ions in the filtrate was measured by inductively coupled plasma emission spectrometer. The adsorption capacity of COF-DEH-Tb (E) and COF-DEH-Tb (Z) for rare earth ions was calculated respectively. Figure 6 is the adsorption capacity of COF-DEH-Tb (E) and COF-DEH-Tb (Z) for rare earth ions. From Figure 6It can be seen that COF-DEH-Tb (E) before UV irradiation has almost no adsorption capacity for rare earth ions, and the adsorption capacity of COF-DEH-Tb (Z) for rare earth ions is greatly improved after UV irradiation. This is mainly due to the acylhydrazone E-Z isomerization of the material after UV irradiation, which causes the shrinkage of the pore structure, thereby constructing a new type of rare earth ion capture nanochannel in the material, greatly improving the adsorption performance of the material for various rare earth ions including La 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , Lu 3 + , Y 3+ .

[0042] In addition, by calculating the distribution coefficient of COF-DEH-Tb (Z) for rare earth ions, the affinity of COF-DEH-Tb (Z) for rare earth ions was studied. Figure 7 is the distribution coefficient of COF-DEH-Tb (Z) for rare earth ions. From Figure 7 it can be seen that COF-DEH-Tb (Z) has the highest affinity for Sm 3+ ion after UV irradiation, which is due to the E-Z isomerization of the acylhydrazone functional group of the material under the stimulation of UV light, causing the shrinkage of the pore structure of the material, which has the strongest size matching effect for Sm 3+ .

[0043] The above-described embodiments only express several preferred embodiments of the present application, which are described in detail and specifically, but are not used to limit the present application. It should be noted that for those skilled in the art, the present application can also have various changes and modifications, and any modification, equivalent replacement, improvement, etc. made within the concept and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Application of a photoresponsive acylhydrazone covalent organic framework in the adsorption and separation of rare earth ions; The preparation method of the photoresponsive acylhydrazone covalent organic framework includes: Acylhydrazone covalent organic frameworks were prepared by Schiff base reaction using 2,5-diethoxybenzene-1,4-bis(formylhydrazine) and trialdehydebenzene as raw materials. Photoresponsive acylhydrazone covalent organic frameworks were obtained by treating the acylhydrazone covalent organic frameworks with ultraviolet light. The rare earth ion is La. 3+ Ce 3+ Pr 3+ 、Nd 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ Lu 3 + Y 3+ At least one of them; The structure of the acylhydrazone covalent organic framework is as follows: , The structure of the photoresponsive acylhydrazone covalent organic framework is as follows: .

2. The application according to claim 1, characterized in that, The ultraviolet irradiation treatment uses ultraviolet light with a wavelength of 365 nm.

3. The application according to claim 2, characterized in that, The ultraviolet light power is 288 mW / cm². 2 The light treatment time is 10-100 hours.

4. The application according to claim 1, characterized in that, The preparation method of the acylhydrazone covalent organic framework includes: 1) Using 2,5-diethoxybenzene-1,4-bis(formylhydrazine) and trialdehyde benzene as raw materials, a solvent was added, the mixture was sonicated, and a reaction solution was obtained; 2) The obtained reaction solution was degassed by freezing-thawing cycle, sealed with a flame and heated at 100-200 °C for 1-5 days. The precipitate was collected, washed and dried to obtain the acylhydrazone covalent organic framework.

5. The application according to claim 4, characterized in that, In step 1), the molar ratio of 2,5-diethoxybenzene-1,4-bis(formylhydrazine) to trialdehyde benzene is (1-2):

1.

6. The application according to claim 4, characterized in that, Step 1) The solvent is composed of 1,4-dioxane, 1,3,5-trimethylbenzene and acetic acid in a volume ratio of (1-5):(5-15):1; the concentration of the acetic acid is 6 M.

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