Metal crown ether trimer complex with electrocatalytic performance, preparation method and application

Abstract

The present invention belongs to the technical field of rare earth transition complex preparation, and discloses a metal crown ether trimer complex with electrocatalytic performance, a preparation method and an application. The preparation method provided by the present invention is as follows: organic ligands H3sha, Y(CF3SO3)3, NaHCO3, and H2bdca are dissolved in a DMF solution in a certain proportion, and stirred at a constant speed for 30 minutes using a magnetic stirrer. Mn(OAc)2·4H2O is added to a C2H5OH solution, and an ultrasonic instrument is used to accelerate its dissolution. The prepared solution is added to the previous solution, and the mixed solution is stirred for 9 hours, filtered, transferred to a beaker and allowed to stand for two weeks to obtain dark brown long strip crystals. The dark brown long strip crystals are metal crown ether trimer complexes with electrocatalytic performance.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth complex preparation, and relates to a metal crown ether trimer complex with electrocatalytic performance, a preparation method and application. Background Art

[0002] Metal crown ethers (MCs) are a class of macrocyclic metal complexes that are similar in structure and function to organic crown ethers. The metal ions in the metal crown ether ring can interact with other atoms or ions, and exhibit special properties that are different from organic crown ethers. As an important class of compounds in self-assembled multinuclear complexes, metal crown ethers have similar skeletons and effective cavities, and can coordinate with metal heteroatoms to form stable compounds (J.Am.Chem.Soc.,2012,51(9),2160-2163). This makes metal crown ether compounds exhibit more valuable properties and have a wide range of applications in biological activity, molecular recognition, organic catalysis, liquid crystals, single-molecule magnets, and surface science simulations, attracting close attention (Chem.Soc.Rev.,2016,45(10),2976-3016). In recent years, with the rapid development of metal crown ethers, crown ethers containing both rare earth and transition metal ions have gradually attracted the attention of scientists. Due to the particularity of their structure, electrons are transferred from ligands to metals, and at the same time, metals are transferred to electrons. This special electron transfer phenomenon and the ability to recognize guest groups give metal crown ethers rich physical, chemical and biological properties (J.Am.Chem.Soc., 2020, 59(48), 21693-21697). Summary of the Invention

[0003] The present invention aims to provide a metal crown ether trimer complex with electrocatalytic performance, a preparation method and an application thereof, and to provide ideas for the preparation of the metal crown ether trimer complex as an electrocatalytic material.

[0004] The technical solutions provided by the present invention are as follows:

[0005] A metal crown ether trimer complex having electrocatalytic properties, the metal crown ether trimer complex belonging to the hexagonal crystal system, and having a molecular formula of [{Y[12-MC sha,Mn(III) -4](H3O)}3(bdca)6]·29DMF·39H2O (H3sha=salicyloximic acid, sha=deprotonated hydroxoximic acid, H2bdca=4,4'-biphenyldicarboxylic acid, bdca=deprotonated 4,4'-biphenyldicarboxylic acid), space group is P63. Unit cell parameters are: α=90°, β=90°, γ=120°,

[0006] A method for preparing the aforementioned metal crown ether trimer complex with electrocatalytic properties comprises: dissolving organic ligands H3sha, Y(CF3SO3)3, NaHCO3, and H2bdca in a DMF solution in a certain proportion, stirring uniformly with a magnetic stirrer, and waiting for the solution to turn turbid, milky white to obtain a mixed solution (referred to as solution 1). Mn(OAc)2·4H2O is added to a C2H5OH solution and dissolved using an ultrasonic device to accelerate the dissolution, obtaining an ethanol solution of Mn(OAc)2·4H2O (referred to as solution 2). Solution 2 is added to solution 1, stirred, filtered, and the filtrate allowed to evaporate, thereby obtaining dark brown, elongated crystals, which constitute the target complex 1.

[0007] The synthetic route of the metal crown ether trimer complex is shown below:

[0008]

[0009] In the above formula, complex 1 is a metal crown ether trimer complex [{Y[12-MC sha,Mn(III) -4](H3O)}3(bdca)6]·29DMF·39H2O.

[0010] Furthermore, in the mixed solution, the molar ratio of the organic ligands H3sha, Y(CF3SO3)3, NaHCO3 and H2bdca is 4:1:16:2.

[0011] Furthermore, in the mixed solution, the amount of DMF added per 0.1 mmol H3sha was 2 mL.

[0012] Furthermore, in the ethanol solution of Mn(OAc)2·4H2O, 2 mL of ethanol was added per 0.1 mmol of Mn(OAc)2·4H2O.

[0013] Furthermore, the volume ratio of the mixed solution to the Mn(OAc)2·4H2O ethanol solution is 1:1.

[0014] The present invention also provides a use of the above-mentioned metal crown ether trimer complex or the metal crown ether trimer complex prepared by the above-mentioned preparation method in electrocatalytic hydrogen and oxygen production.

[0015] Compared to existing technologies, the present invention employs a room-temperature volatilization synthesis strategy to produce a metal crown ether trimer complex with electrocatalytic properties. The preparation of this complex is simple and easy, and the raw materials are readily available. This not only provides new insights into the synthesis of metal crown ether complexes, but also injects new vitality into the field of electrochemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Molecular structure of complex 1;

[0017] Figure 2 Y Ⅲ Coordination configuration diagram of ions;

[0018] Figure 3 Mn II Coordination configuration diagram of ions;

[0019] Figure 4 IR spectrum of complex 1;

[0020] Figure 5 Thermogravimetric diagram of complex 1;

[0021] Figure 6 HER performance test diagram; (a) LSV comparison diagram; (b) overpotential comparison bar graph of different current densities; (c) Tafel slope curve; (d) EIS comparison diagram; (e) CV diagram of electrode 2; (f) C dl Comparison chart;

[0022] Figure 7 OER performance test diagram; (a) LSV polarization curve; (b) overpotential comparison bar graph at different current densities; (c) Tafel slope curve; (d) EIS diagram; (e) CV diagram of electrode 4; (f) C dl Comparison picture. Specific implementation plan

[0023] The present invention will be further described with reference to specific embodiments. It should be understood that these embodiments are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and that equivalent changes or modifications also fall within the scope defined by the claims of this application.

[0024] It should be noted that all reagents in the following examples were purchased directly from the market and were of analytical grade and were not further purified before use.

[0025] Example 1: [{Y[12-MC sha,Mn(III) Preparation of [4-(H3O)}3(bdca)6]·29DMF·39H2O (complex 1)

[0026] [{Y[12-MC sha,Mn(III)-4](H3O)}3(bdca)6]·29DMF·39H2O (complex 1): Weigh 15.3 mg of organic ligand salicyloxime H3sha (0.1 mmol), 13.4 mg Y(CF3SO3)3 (0.025 mmol), 33.6 mg NaHCO3 (0.4 mmol) and 12.1 mg H2bdca (0.05 mmol) in a certain proportion and dissolve them in 2 mL DMF solution. Stir at a constant speed with a magnetic stirrer for 30 minutes until the solution becomes turbid milky white. 15.2 mg of Mn(OAc)2·4H2O (0.1 mmol) was added to 2 mL of C2H5OH solution and dissolved using an ultrasonic device. The prepared solution was added to the previous solution, and the mixed solution was stirred for 9 hours. The filtrate was transferred to a beaker and sealed with plastic wrap. After standing for two weeks, dark brown elongated crystals were obtained, which were the target complex 1.

[0027] Example 2: Crystal structure determination

[0028] Single crystals with good structural integrity and suitable size were selected for structure determination. Data of complex 1 were collected at 120 K using a Rigaku Oxford diffractometer with Mo Kα radiation from a graphite monochromator. The diffraction data were collected and processed using the SHELXS-2014 and SHELXL-2014 packages.

[0029] The results of single crystal X-ray diffractometer showed that complex 1 crystallized in the hexagonal P63 space group and consisted of six H2bdca ligands connected to three ion pairs {Y[12-MC Mn(III) -4]} 3+ and hydronium ions, wherein the building blocks {Y[12-MC Mn(III) -4]} is achieved by four H3sha ligands using μ3:η 2 :η 1 :η 1 :η 1 The bridging mode and two Mn III ions and a Y III Ionic coordination formation, six bridging ligands H2bdca adopt μ4:η 1 :η 1 :η 1 :η 1 Pattern and construction unit {Y[12-MC Mn(III) -4]} are connected to Y and Mn, and complex 1 is finally formed into a triangular macrocyclic molecule composed of three metal crown ethers ( Figure 1 ).

[0030] Table 1 Partial CShM values ​​of Y ions in complex 1

[0031]

[0032] Y in complex 1 III The ion has an octagonal inverse prismatic configuration ( Figure 2 ), connected to it by eight oxygen atoms, four of which are provided by the carboxyl groups in the four ligands H2bdca, and the other four oxygen atoms come from the hydroxyl groups in H3sha. The average bond length of YO is The bond angle of OYO ranges from 65.3 to 142.1°. III There are two coordination configurations of ions, two of which are hexacoordinated octahedral configurations (Mn1, Mn3), and the other two are pentacoordinated tetrahedral configurations (Mn2, Mn4) ( Figure 3 On the plane of {Mn4}, three oxygens and one nitrogen are provided by the ligand H3sha, and two hexacoordinated Mn II The two oxygen atoms of the ion come from water and 4,4'-biphenyldicarboxylic acid, respectively, and the two penta-coordinated Mn II One oxygen atom of the ion is derived from 4,4'-diphenyldicarboxylic acid. The coordination geometry of all metal ions was confirmed using Shape software (Tables 1-3).

[0033] Table 2 CShM values ​​of some Mn ions in complex 1

[0034]

[0035] Table 3 CShM values ​​of some Mn ions in complex 1

[0036]

[0037] The infrared spectrum of complex 1 is shown in Figure 4 As shown, complex 1 has a wavelength of 3400 cm -1 to 2500cm -1 There is a broad absorption peak in the range, which is the stretching vibration of -OH. -1 There is an absorption peak of C=O stretching vibration and an associated hydroxyl group at 1650cm -1 , 1500cm -1 The two absorption peaks at 900-650cm are the absorption peaks of the skeleton vibration of the benzene ring. -1 The out-of-plane deformation vibration of the CH on the aromatic ring appeared in the region. The infrared results showed that the amide group and hydroxyl group of the ligand H3sha and the carboxyl group of H2bdca participated in the coordination.

[0038] The structural thermal stability analysis of complex 1 was carried out between 30 and 800 °C under N2 atmosphere (heating rate: 10 °C / min -1 ), because there are many holes in the complex, which makes the weight loss process more complicated. Figure 5 As shown, the thermogravimetric curve of complex 1 decreases rapidly between 30 and 100°C, reaching a plateau at around 300°C. The first step of weight loss is approximately 13.0%, which is due to the loss of crystalline water and solvent. As the temperature continues to rise, the loss of the coordinating solvent causes the structure of complex 1 to collapse.

[0039] Example 3: Study on the electrocatalytic properties of double-layer metal crown ether complexes

[0040] Preparation of powder: Weigh 10 mg of complex 1, place it in a tube furnace, continuously introduce nitrogen, wait for 30 minutes, set the program to heat the tube furnace to 300 ° C at 2 ° C / min and then keep the temperature constant for 3 hours, then start the 2 ° C / min program to cool to room temperature to obtain a black powder of complex 1. Take the powder of complex 1 in a 2mL centrifuge tube, add 1mL of ethanol solution, and then add 5μL of perfluorosulfonic acid (Nafion) adhesive, ultrasonicate for 30 minutes to obtain a suspended liquid, and the powder of uncalcined complex 1 is used as a control. Use a pipette to draw 5μL of solution, apply it on the electric rod to be tested, dry it under the irradiation of infrared lamp, and repeat the application three to four times.

[0041] Electrochemical test: The electrolyte used was 1.0 mol / L KOH alkaline solution. The electrode coated with the test sample was used as the working electrode, the standard Hg / HgO (0.098V) was used as the reference electrode, and the carbon rod was used as the counter electrode. Electrochemical tests were performed on the electrode coated with the uncalcined complex 1 powder and the electrode coated with the calcined complex 1 powder as the working electrode. The HER test results of the three electrode systems are shown in the figure below. Figure 6 At a scanning speed of 5mV / s, 1×10 -5 The experimental results were analyzed and processed using electrochemical impedance spectroscopy (EIS) technology with a frequency of up to 100 kHz and iR correction. The Tafel slope directly indicates the efficiency of water electrolysis to produce hydrogen and oxygen. Figure 7 To test the electrocatalytic OER performance of complex 1. The electrocatalytic test showed that for HER, the electrode composed of the calcined complex 1 powder showed good performance in LSV, EIS, C dl In the tests, the performance was better than that of the electrode composed of the powder of the uncalcined complex 1. After calcination, the C dl The value is 0.17mF·cm -2 Increased to 0.73mF·cm -2 For OER, the electrode composed of the calcined powder of complex 1 showed good performance in EIS, Cdl In terms of performance, C dl Value 0.29mF·cm -2 Increased to 0.92mF·cm -2 Therefore, it can be concluded that the electrocatalytic performance of the complex can be improved by calcination.

Claims

1. A metal crown ether trimer complex with electrocatalytic performance, characterized in that: The metal crown ether trimer complex belongs to the hexagonal crystal system and has the molecular formula [{Y[12-MC sha,Mn(III) -4](H3O)}3(bdca)6]·29DMF·39H2O, space group is P63; unit cell parameters are: a= α=90°, β=90°, γ=120°, Wherein, SHA = deprotonated hydroxyl oxime acid; BDCA = deprotonated 4,4'-biphenyldicarboxylic acid.

2. A method for preparing the metal crown ether trimer complex according to claim 1, characterized in that: The synthetic route of the preparation method is shown below: The preparation method comprises the following steps: S1 H3sha, Y (CF3SO3) 3, NaHCO3 and H2bdca were mixed and dissolved in DMF solution, stirred until uniformly dispersed to obtain a mixed solution; S2. Add an ethanol solution of Mn(OAc)2·4H2O to the mixed solution and stir. After stirring, filter and allow the filtrate to evaporate to obtain complex 1, ie, the metal crown ether trimer complex.

3. A preparation method according to claim 2, characterized in that: In the mixed solution, the molar ratio of the organic ligands H3sha, Y(CF3SO3)3, NaHCO3 and H2bdca is 4:1:16:

2.

4. The preparation method according to claim 3, characterized in that In the mixed solution, the amount of DMF added per 0.1 mmol H3sha was 2 mL.

5. The preparation method according to claim 4, characterized in that In the ethanol solution of Mn(OAc)2·4H2O, 2 mL of ethanol was added per 0.1 mmol of Mn(OAc)2·4H2O.

6. The preparation method according to claim 5, characterized in that The volume ratio of the mixed solution to the Mn(OAc)2·4H2O ethanol solution is 1:

1.

7. Use of the metal crown ether trimer complex according to claim 1 or the metal crown ether trimer complex prepared by the preparation method according to any one of claims 2 to 6 in electrocatalytic hydrogen and oxygen production.

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