Conductive polymer containing tempos in side chain and preparation method and application thereof

Abstract

The present application relates to the field of electrochemistry, and discloses a kind of side chain containing TEMPO conductive polymer and its preparation method and application.2,5-diformylfuran is prepared by using 5-hydroxymethylfurfural as raw material, and there are problems of catalyst recovery and separation difficulty with product. In order to solve the above technical problems, the small molecule catalyst TEMPO is connected to the conductive polymer, and the conductive polymer obtained by connection realizes heterogeneous electrochemical catalytic oxidation of 5-hydroxymethylfurfural to generate 2,5-diformylfuran. The conductive polymer is used as the catalyst for the electrocatalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-diformylfuran, which avoids the problem of difficult separation of catalyst and product, and has the characteristics of high reaction rate and high product yield.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a conductive polymer containing TEMPO in its side chain, its preparation method, and its application. Background Technology

[0002] With the continuous depletion of fossil resources such as petroleum, the development and utilization of renewable and abundant biomass resources to produce bulk chemicals, fine chemicals, and polymer materials is of great significance in supplementing the shortage of petroleum resources. Carbohydrates constitute the largest proportion of biomass resources. Through acid-catalyzed dehydration of carbohydrates such as fructose, glucose, and cellulose, 5-hydroxymethylfurfural (HMF), which has a broad market application, can be produced. HMF is one of the biomass-based platform compounds and an important intermediate in the synthesis of various fine chemicals and furan-based polymers, attracting widespread attention both domestically and internationally.

[0003] Oxidation of HMF yields several important platform compounds, such as 2,5-dicarboxyfuran (DFF), 2,5-furandicarboxylic acid (FDCA), 5-aldehyde-2-furancarboxylic acid (FFCA), and 5-hydroxymethylfurfural acid (HMFCA). Among these, DFF, FDCA, and HMFCA are important downstream products obtained from the selective oxidation of HMF. 2,5-dicarboxyfuran is one of the most important derivatives of 5-hydroxymethylfurfural, with wide applications in the chemical industry, and it can also be used to prepare pesticide intermediates, fungicides, and heterocyclic compounds.

[0004] Currently, 2,5-dicarboxyfuran is prepared from 5-hydroxymethylfurfural using oxidants such as manganese dioxide, chromium trioxide, and sodium hypochlorite. However, this preparation method causes serious environmental pollution, has a long reaction time, requires large amounts of oxidants and reaction solvents, and has a very low product yield, making separation difficult and unsuitable for large-scale industrial production.

[0005] For example, Chinese patent CN101987839A discloses a method for preparing 2,5-dicarboxyfuran by oxidizing 5-hydroxymethylfurfural. Using a Cu(NO3)2 and VOSO4 composite catalytic system, with molecular oxygen as the oxygen source, the reaction is carried out in acetonitrile at 80°C for 1.5 h, achieving a 98% DFF yield. This process has mild reaction conditions and a high DFF yield. However, the recovery and recycling of the catalyst in this system is relatively difficult.

[0006] The 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO) possesses a highly stable nitroxide radical due to the resonance structure formed by the movement of a single electron between nitrogen and oxygen atoms. As a highly efficient and stable small-molecule catalyst, TEMPO is widely used in the selective oxidation of various hydroxyl functional groups. Applying TEMPO as a catalyst in the preparation of 2,5-dicarboxyfuran from 5-hydroxymethylfurfural yields a high reaction rate. However, as a homogeneous catalyst, TEMPO is difficult to recover and purify, presenting challenges in separating the catalyst from the product. Summary of the Invention

[0007] In existing technologies, the preparation of 2,5-dicarboxyfuran from 5-hydroxymethylfurfural presents challenges in catalyst recovery and product separation. To address these issues, this invention provides a conductive polymer with TEMPO side chains, its preparation method, and its applications. This invention connects the small-molecule catalyst TEMPO to a conductive polymer, enabling the heterogeneous electrochemical catalytic oxidation of 5-hydroxymethylfurfural to 2,5-dicarboxyfuran via the resulting conductive polymer. Using this conductive polymer as a catalyst for the electrocatalytic oxidation of 5-hydroxymethylfurfural to 2,5-dicarboxyfuran avoids the difficulties in catalyst-product separation and offers advantages such as high reaction rate and high product yield.

[0008] The specific technical solution of this invention is as follows:

[0009] On one hand, the present invention provides a conductive polymer containing TEMPO in its side chains, which has the following structural formula:

[0010]

[0011] Where n = 4 to 100, x = 1 to 10, and y = 1 to 10.

[0012] Currently, the catalysts used in the preparation of 2,5-dicarboxyfuran from 5-hydroxymethylfurfural include sodium hypochlorite and TEMPO, all of which are homogeneous catalysts, leading to difficulties in separating the catalyst from the product. Other catalysts, such as the Cu(NO3)2 and VOSO4 composite catalytic system proposed in Chinese patent CN101987839A, also suffer from difficulties in separating the catalyst from the reaction solution. This invention provides a conductive polymer with TEMPO contained in its side chains, using 3,4-ethylenedioxythiophene (EDOT) and 2,2'-bisthiophene (BTh) as monomers. This conductive polymer achieves TEMPO immobilization. Using this conductive polymer as a catalyst in the electrochemical catalytic oxidation reaction of 5-hydroxymethylfurfural to 2,5-dicarboxyfuran achieves heterogeneous electrocatalysis of TEMPO, avoiding the difficulty in separating the catalyst from the product, and also features fast reaction and high product yield.

[0013] To achieve TEMPO immobilization, this invention selects 3,4-ethylenedioxythiophene (EDOT) and 2,2'-bisthiophene (BTh) as monomers to copolymerize and form a conductive polymer. 3,4-ethylenedioxythiophene possesses a low oxidation potential, good molecular symmetry, low steric hindrance condensation rings, and a wide anodic potential window. Poly(PEDOT) obtained by electropolymerization of EDOT has the advantage of high electrical conductivity. However, when TEMPO is attached to 3,4-ethylenedioxythiophene (PEDOT) as a catalyst for the preparation of 2,5-dicarboxyfuran from 5-hydroxymethylfurfural, the polymer stability is poor, resulting in low product yield. Therefore, this invention further utilizes EDOT and BTh copolymerization to form a copolymer, and immobilizes TEMPO onto this copolymer as a catalyst to further improve the yield of 2,5-dicarboxyfuran. Both EDOT and BTh are thiophene derivatives, with BTh having a lower initial oxidation potential. Copolymerizing EDOT derivatives (EDOT-TEMPO) with TEMPO groups in the side chains with BTh can not only reduce the oxidation potential and prevent over-oxidation, but also increase the length of the polymer backbone, reduce the steric hindrance of the side chains, and further improve the stability of the polymer.

[0014] On the other hand, the present invention provides a method for preparing the above-mentioned conductive polymer containing TEMPO in the side chain, comprising the following steps:

[0015] (1) Using (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid (C4-EDOT-COOH) and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitrogen oxide radical (4-OH-TEMPO) as reactants, a catalyst and a dehydrating agent were added to carry out the reaction to obtain 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical (EDOT-TEMPO);

[0016] (2) A three-electrode system was adopted, with Pt electrodes as the working electrode and auxiliary electrode, and Ag / Ag+ electrode as the reference electrode. In a dichloromethane solution containing tetrabutylammonium perchlorate, monomers 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical (EDOT-TEMPO) and 2,2'-bisthiophene (BTh) were added to carry out an electropolymerization reaction.

[0017] (3) After the electropolymerization reaction is completed, the surface of the working electrode is rinsed and dried to obtain a conductive polymer (P(EDOT-TEMPO / BTh)) film with TEMPO side chains attached to the surface of the working electrode.

[0018] The reaction expression for the preparation method provided by this invention is as follows:

[0019]

[0020] As a preferred embodiment of the above-mentioned technical solution of the present invention, in step (1), the molar ratio of (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitric oxide radical is 1:1 to 1.5.

[0021] As a preferred embodiment of the above technical solution of the present invention, in step (1), the catalyst is 4-dimethylaminopyridine.

[0022] Further preferred, the molar ratio of (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid and 4-dimethylaminopyridine is 1:0.1 to 0.5.

[0023] As a preferred embodiment of the above technical solution of the present invention, in step (1), the dehydrating agent is dicyclohexylcarbodiimide.

[0024] Further preferred, the molar ratio of (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid to dicyclohexylcarbodiimide is 1:1 to 1.5.

[0025] As a preferred embodiment of the above technical solution of the present invention, in step (1), the reaction time is 8 to 14 hours.

[0026] Specifically, in step (1), after the reaction, the method for obtaining the product 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy free radical from the reaction solution is as follows:

[0027] The reaction solution was filtered, and the solvent was removed by rotary evaporation. The crude product was purified by column chromatography using a mixed solution of petroleum ether / ethyl acetate = 5 / 1 (v / v). The eluent containing the target compound was collected, and the eluent was removed by evaporation to obtain an orange-yellow solid, which is 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical (EDOT-TEMPO).

[0028] As a preferred embodiment of the above-mentioned technical solution of the present invention, in step (2), the molar ratio of monomer 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical (EDOT-TEMPO) and 2,2'-bisthiophene (BTh) is 1:0.2 to 0.8.

[0029] In this invention, EDOT-TEMPO and BTh are copolymerized, and the preferred molar ratio is 1:0.2 to 0.8. Excessive BTh content results in a relatively low TEMPO content in the copolymer, leading to poor catalytic performance; insufficient BTh content results in poor copolymer structural stability, thus affecting catalytic performance.

[0030] As a preferred embodiment of the above technical solution of the present invention, in step (2), the molar concentration of tetrabutylammonium perchlorate in the dichloromethane solution is 0.1 to 0.15 mol / L.

[0031] As a preferred embodiment of the above technical solution of the present invention, in step (2), the polymerization potential of the electropolymerization reaction is -0.5 to 1.5V, the scanning speed is 50mV / s, and the number of scanning cycles is 4 to 10.

[0032] As a preferred embodiment of the above technical solution of the present invention, in step (3), the surface of the working electrode is rinsed with dichloromethane and acetonitrile respectively.

[0033] This invention provides the application of the above-mentioned conductive polymer and the conductive polymer prepared by the above-mentioned preparation method in the catalytic generation of 2,5-dicarboxyfuran from 5-hydroxymethylfurfural.

[0034] The conductive polymer P (EDOT-TEMPO / BTh) provided by this invention has the catalytic activity of TEMPO. When polymer P (EDOT-TEMPO / BTh) is used for the electrocatalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-dicarboxyfuran, the results show that it has good catalytic oxidation performance.

[0035] Compared with the prior art, the present invention has the following technical effects:

[0036] This invention provides a conductive polymer P (EDOT-TEMPO / BTh) as a catalyst in the electrochemical oxidation reaction of 5-hydroxymethylfurfural to 2,5-dicarboxyfuran. It can realize heterogeneous electrocatalysis of the reaction, avoid the problem of difficult separation of catalyst and product, and has the characteristics of fast reaction and high product yield. Attached Figure Description

[0037] Figure 1 The 1H NMR spectrum of EDOT-TEMPOH prepared in Example 1 of this invention;

[0038] Figure 2 The carbon NMR spectrum of EDOT-TEMPOH prepared in Example 1 of this invention;

[0039] Figure 3 This is a scanning electron microscope image of polymer P (EDOT-TEMPO / BTh) prepared in Example 4 of the present invention;

[0040] Figure 4 The elemental mapping diagram of polymer P (EDOT-TEMPO / BTh) prepared in Example 4 of this invention;

[0041] Figure 5 Cyclic voltammetric polymerization curve of polymer P (EDOT-TEMPO / BTh) prepared in Example 4 of this invention;

[0042] Figure 6 Cyclic voltammetry diagram for stability testing of polymer P (EDOT-TEMPO / BTh) prepared in Example 4 of this invention. Detailed Implementation

[0043] The present invention will be further described below with reference to embodiments and accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0044] General Embodiments This invention provides a conductive polymer P (EDOT-TEMPO / BTh) and its preparation method, the preparation method comprising the following steps:

[0045] (1) Using (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid (C4-EDOT-COOH) and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitrogen oxide radical (4-OH-TEMPO) as reactants, a catalyst and a dehydrating agent were added to carry out the reaction to obtain 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical (EDOT-TEMPO);

[0046] (2) A three-electrode system is adopted, with Pt electrodes as the working electrode and auxiliary electrode, and Ag / Ag as the reference electrode. + Electrode, in a dichloromethane solution containing tetrabutylammonium perchlorate, is subjected to electropolymerization reaction by adding monomers 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical (EDOT-TEMPO) and 2,2'-bisthiophene (BTh);

[0047] (3) After the electropolymerization reaction is complete, the surface of the working electrode is rinsed and dried to obtain a conductive polymer film (P(EDOT-TEMPO / BTh)) with TEMPO-containing side chains attached to the surface of the working electrode. The polymer P(EDOT-TEMPO / BTh) has the following structural formula:

[0048]

[0049] Where n = 4 to 100, x = 1 to 10, and y = 1 to 10.

[0050] Preferably, in step (1), the catalyst is 4-dimethylaminopyridine (DMAP).

[0051] Preferably, in step (1), the dehydrating agent is dicyclohexylcarbodiimide (DCC).

[0052] Further preferred, in step (1), the molar ratio of (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid (C4-EDOT-COOH), 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical (4-OH-TEMPO), 4-dimethylaminopyridine (DMAP), and dicyclohexylcarbodiimide (DCC) is 1:1~1.5:0.1~0.5:1~1.5.

[0053] Preferably, in step (1), the reaction time is 8 to 14 hours.

[0054] Specifically, in step (1), after the reaction, the method for obtaining the product 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy free radical from the reaction solution is as follows:

[0055] The reaction solution was filtered, and the solvent was removed by rotary evaporation. The crude product was purified by column chromatography using a mixed solution of petroleum ether / ethyl acetate = 5 / 1 (v / v). The eluent containing the target compound was collected, and the eluent was removed by evaporation to obtain an orange-yellow solid, which is 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical (EDOT-TEMPO).

[0056] Preferably, in step (2), the molar ratio of monomer 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical and 2,2'-bisthiophene is 1:0.2 to 0.8.

[0057] Preferably, in step (2), the molar concentration of tetrabutylammonium perchlorate in the dichloromethane solution is 0.1–0.15 mol / L.

[0058] Preferably, in step (2), the polymerization potential of the electropolymerization reaction is -0.5 to 1.5V, the scanning speed is 50mV / s, and the number of scanning cycles is 4 to 10.

[0059] Preferably, in step (3), the surface of the working electrode is rinsed with dichloromethane and acetonitrile, respectively.

[0060] The reaction expression for the above preparation method is as follows:

[0061]

[0062] Example 1: Synthesis of EDOT-TEMPO

[0063] In a 250 mL round-bottom flask, 3.26 g C4-EDOT-COOH (12.0 mmol), 2.07 g 4-OH-TEMPO (12.0 mmol), 0.15 g 4-dimethylaminopyridine (DMAP) (1.2 mmol), and 60 mL dichloromethane were added. 2.97 g dicyclohexylcarbodiimide (DCC, 14.4 mmol) was dissolved in 50 mL dichloromethane and added dropwise to the above solution using a 50 mL dropping funnel. The reaction was monitored by thin-layer chromatography and stirred at 25 °C for 18 h. After the reaction was complete, the reaction solution was filtered to remove N,N'-dicyclohexylurea (DCU), and the solvent was removed by rotary evaporation. The crude product was purified by column chromatography (using a 5 / 1 (v / v) mixture of petroleum ether and ethyl acetate as eluent) to obtain 2.86 g of orange-yellow solid EDOT-TEMPO, with a yield of 56%.

[0064] The yellow solid obtained in this embodiment was subjected to mass spectrometry analysis. The results are as follows: High-resolution mass spectrometry result (ESI+): m / z, calculated for C 20 H 29 NO7S + [M+H] + :427.1659; found:427.1652.

[0065] EDOT-TEMPO contains free radicals and cannot be directly characterized by NMR. Therefore, in this embodiment, EDOT-TEMPO was reduced to EDOT-TEMPOH with L-ascorbic acid before being characterized by NMR. The proton NMR spectrum and carbon NMR spectrum are shown below. Figure 1 , Figure 2 The NMR data are as follows:

[0066] 1 H NMR (400MHz, CDCl3) δ6.46 (s, 2H), 5.16 (s, 1H), 4.44 (s, 3H), 4.33 (d, J = 9.9Hz, 1H), 4.16 (s,1H),2.74(d,J=14.7Hz,5H),2.00(d,J=9.6Hz,2H),1.65(s,2H),1.50-1.13(m,12H).

[0067] 13C NMR (101MHz, CDCl3) δ169.99, 169.69, 139.20, 139.01, 98.54, 98.23 (d, J = 12. 7Hz),69.49,65.30,63.75,60.69,57.29,41.83,30.11,27.33,26.99,18.44.

[0068] Example 2: Synthesis of EDOT-TEMPO

[0069] The main difference between this embodiment and Example 1 is that the amount of 4-OH-TEMPO added is 14.4 mmol, the amount of DMAP added is 2.4 mmol, the amount of DCC added is 18.0 mmol, and the reaction time is 16 h.

[0070] In this embodiment, the separation yield of EDOT-TEMPO was 64%.

[0071] Example 3: Synthesis of EDOT-TEMPO

[0072] The main difference between this embodiment and Example 1 is that the amount of 4-OH-TEMPO added is 18 mmol, the amount of DMAP added is 6.0 mmol, the amount of DCC added is 12.0 mmol, and the reaction time is 14 h.

[0073] In this embodiment, the separation yield of EDOT-TEMPO was 58%.

[0074] Example 4: Preparation of P (EDOT-TEMPO / BTh)

[0075] Electrochemical polymerization was performed on a Pt substrate electrode using a three-electrode system via cyclic voltammetry on a CHI600e electrochemical workstation. The working electrode and auxiliary electrode were both platinum sheet electrodes, and the reference electrode was an Ag / Ag electrode. +The electrode (0.1 mol / L AgNO3 / CH3CN solution) was placed in a 25 mL non-split electrochemical cell. A 15 mL solution of 0.75 mmol EDOT-TEMPO, 0.37 mmol BTh, and 0.1 mol / L tetrabutylammonium perchlorate in dichloromethane was added. The solution was ultrasonically cleaned for 5 min to completely dissolve the monomers EDOT-TEMPO and BTh. The electrochemical cell was placed in a 25°C constant temperature water bath. Polymer P (EDOT-TEMPO / BTh) was obtained on the working electrode using cyclic voltammetry, with a potential range of -0.5 V to 1.5 V, a scan rate of 50 mV / s, and 4 scan cycles. After polymerization, the electrode was removed and its surface was rinsed with dichloromethane and acetonitrile solutions. A blue-black polymer P (EDOT-TEMPO / BTh) film was obtained adhering to the electrode surface. Polymer P (EDOT-TEMPO / BTh) has the following structural formula:

[0076]

[0077] Where n = 4 to 100, x = 1 to 10, and y = 1 to 10.

[0078] The scanning electron microscope image of polymer P(EDOT-TEMPO / BTh) in this embodiment is shown below. Figure 3 See the element mapping diagram. Figure 4 Cyclic voltammetric polymerization curves are shown below. Figure 5 .from Figure 5 It can be seen that as the number of scan cycles increases, the oxidation peak current gradually increases, indicating that the conductivity of the polymer is getting better and better.

[0079] The polymer P (EDOT-TEMPO / BTh) prepared in this example was subjected to electrochemical stability testing, and its cyclic voltammogram is shown in [Figure number missing]. Figure 6 .

[0080] Depend on Figure 6 It can be seen that the oxidation peak current in the first cycle is 2.07 mA. The oxidation peak current continues to rise in the second cycle, reaching a maximum of 2.41 mA in the 10th cycle. Then, from the 10th to the 18th cycles, the oxidation peak current remains constant at 2.41 mA, representing 116% of its initial value. Subsequently, the oxidation peak current begins to decrease, reaching 1.60 mA in the 100th cycle (77% of its initial value), and 1.08 mA in the 200th cycle (still reaching 52% of its initial value). This demonstrates that the P(EDOT-TEMPO / BTh) modified electrode exhibits excellent electrochemical stability in cyclic voltammetry.

[0081] Example 5: Preparation of P (EDOT-TEMPO / BTh)

[0082] The main difference between the reaction steps and those in Example 4 is that the amount of monomer EDOT-TEMPO added is 1.5 mmol, and the amount of BTh added is 0.3 mmol. The specific reaction steps in this example are as follows:

[0083] Electrochemical polymerization was performed on a Pt substrate electrode using a three-electrode system via cyclic voltammetry on a CHI600e electrochemical workstation. The working electrode and auxiliary electrode were both platinum sheet electrodes, and the reference electrode was an Ag / Ag electrode. + An electrode (0.1 mol / L AgNO3 / CH3CN solution) was placed in a 25 mL non-split electrochemical cell. 1.5 mmol EDOT-TEMPO, 0.3 mmol BTh, and 15 mL of a 0.1 mol / L tetrabutylammonium perchlorate dichloromethane solution were added. The solution was ultrasonically cleaned for 5 min to completely dissolve the monomers EDOT-TEMPO and BTh. The electrochemical cell was placed in a 25°C constant-temperature water bath. Cyclic voltammetry was used to obtain polymer P (EDOT-TEMPO / BTh) on the working electrode, with a potential range of -0.5 V to 1.5 V, a scan rate of 50 mV / s, and 4 scan cycles. After polymerization, the electrode was removed and its surface was rinsed with dichloromethane solution and acetonitrile solution, respectively. A blue-black P (EDOT-TEMPO / BTh) polymer film was obtained adhering to the electrode surface.

[0084] Example 6: Preparation of P (EDOT-TEMPO / BTh)

[0085] The main difference between the reaction steps and those in Example 4 is that the amount of monomer EDOT-TEMPO added is 1.5 mmol, and the amount of BTh added is 1.2 mmol. The specific reaction steps in this example are as follows:

[0086] Electrochemical polymerization was performed on a Pt substrate electrode using a three-electrode system via cyclic voltammetry on a CHI600e electrochemical workstation. The working electrode and auxiliary electrode were both platinum sheet electrodes, and the reference electrode was an Ag / Ag electrode. +An electrode (0.1 mol / L AgNO3 / CH3CN solution) was placed in a 25 mL non-split electrochemical cell. 1.5 mmol EDOT-TEMPO, 1.2 mmol BTh, and 15 mL of a 0.1 mol / L tetrabutylammonium perchlorate dichloromethane solution were added. The solution was ultrasonically cleaned for 5 min to completely dissolve the monomers EDOT-TEMPO and BTh. The electrochemical cell was placed in a 25°C constant-temperature water bath. Cyclic voltammetry was used to obtain polymer P (EDOT-TEMPO / BTh) on the working electrode, with a potential range of -0.5 V to 1.5 V, a scan rate of 50 mV / s, and 4 scan cycles. After polymerization, the electrode was removed and its surface was rinsed with dichloromethane solution and acetonitrile solution, respectively. A blue-black P (EDOT-TEMPO / BTh) polymer film was obtained adhering to the electrode surface.

[0087] Example 7: Preparation of P (EDOT-TEMPO / BTh)

[0088] The main difference between the reaction steps and those in Example 4 is that the concentration of the tetrabutylammonium perchlorate solution in dichloromethane is 0.15 mol / L, and the number of scan cycles is 10. The specific reaction steps in this example are as follows:

[0089] Electrochemical polymerization was performed on a Pt substrate electrode using a three-electrode system via cyclic voltammetry on a CHI600e electrochemical workstation. The working electrode and auxiliary electrode were both platinum sheet electrodes, and the reference electrode was an Ag / Ag electrode. + The electrode (0.1 mol / L AgNO3 / CH3CN solution) was placed in a 25 mL non-splitting electrochemical cell. A 15 mL solution of 0.75 mmol EDOT-TEMPO, 0.37 mmol BTh, and 0.15 mol / L tetrabutylammonium perchlorate in dichloromethane was added. The solution was ultrasonically cleaned for 5 min to completely dissolve the monomers EDOT-TEMPO and BTh. The electrochemical cell was placed in a 25°C constant-temperature water bath. Cyclic voltammetry was used to obtain polymer P (EDOT-TEMPO / BTh) on the working electrode, with a potential range of -0.5 V to 1.5 V, a scan rate of 50 mV / s, and 10 scan cycles. After polymerization, the electrode was removed and its surface was rinsed with dichloromethane and acetonitrile solutions. A blue-black P (EDOT-TEMPO / BTh) polymer film was obtained adhering to the electrode surface.

[0090] Comparative Example 1

[0091] The main difference from Example 4 is that BTh is not added; polymer P (EDOT-TEMPO) is prepared by homopolymerization of the monomer EDOT-TEMPO. The specific preparation steps are as follows:

[0092] Electrochemical polymerization was performed on a Pt substrate electrode using a three-electrode system via cyclic voltammetry on a CHI600e electrochemical workstation. The working electrode and auxiliary electrode were both platinum sheet electrodes, and the reference electrode was an Ag / Ag electrode. + An electrode (0.1 mol / L AgNO3 / CH3CN solution) was placed in a 25 mL non-split electrochemical cell. 1.12 mmol of EDOT-TEMPO and 15 mL of a 0.1 mol / L tetrabutylammonium perchlorate dichloromethane solution were added, and the solution was ultrasonically cleaned for 5 min to completely dissolve the EDOT-TEMPO monomer. The electrochemical cell was placed in a 25°C constant-temperature water bath, and polymer P (EDOT-TEMPO) was obtained on the working electrode using cyclic voltammetry. The potential range was -0.5 V to 1.5 V, the scan rate was 50 mV / s, and the number of scans was 4. After polymerization, the electrode was removed, and the electrode surface was rinsed with dichloromethane and acetonitrile solutions. A dark blue polymer P (EDOT-TEMPO) film was obtained adhering to the electrode surface.

[0093] Comparative Example 2

[0094] The main difference from Example 4 is that the monomer EDOT-TEMPO(4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical) is replaced with 4-(((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)carbonyl)-2,2,6,6-tetramethylpiperidine-1-oxy radical (comparative monomer). The structural formula of 4-(((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)carbonyl)-2,2,6,6-tetramethylpiperidine-1-oxy radical is:

[0095]

[0096] The specific preparation steps are as follows:

[0097] Electrochemical polymerization was performed on a Pt substrate electrode using a three-electrode system via cyclic voltammetry on a CHI600e electrochemical workstation. The working electrode and auxiliary electrode were both platinum sheet electrodes, and the reference electrode was an Ag / Ag electrode. +The electrode (0.1 mol / L AgNO3 / CH3CN solution) was placed in a 25 mL non-split electrochemical cell. 0.75 mmol of the control monomer, 0.37 mmol of BTh, and 15 mL of a 0.1 mol / L tetrabutylammonium perchlorate dichloromethane solution were added. The solution was ultrasonically cleaned for 5 min to completely dissolve the monomer. The electrochemical cell was placed in a 25°C constant-temperature water bath. Polymer was obtained on the working electrode using cyclic voltammetry, with a potential range of -0.5 V to 1.5 V, a scan rate of 50 mV / s, and 4 scan cycles. After polymerization, the electrode was removed, and the electrode surface was rinsed with dichloromethane and acetonitrile solutions. A blue-purple polymer film was obtained adhering to the electrode surface.

[0098] Comparative Example 3

[0099] The main difference from Example 4 is that the amounts of monomer EDOT-TEMPO and BTh are 0.75 mmol and 0.07 mmol, respectively.

[0100] Comparative Example 4

[0101] The main difference from Example 4 is that the amounts of monomer EDOT-TEMPO and BTh are 0.75 mmol and 0.75 mmol, respectively.

[0102] Catalytic performance testing of P(EDOT-TEMPO / BTh) electrocatalytic oxidation of 5-hydroxymethylfurfural

[0103] The catalytic performance testing method was as follows: the electrocatalytic oxidation reaction was carried out on an electrochemical workstation CHI600e using a three-electrode system. The Pt electrodes with polymer films attached to their surfaces obtained in Examples 4-7 and Comparative Examples 1-4 were used as the working electrodes, and the Pt electrode was used as the auxiliary electrode. The Ag / Ag ratio was... + The reference electrode was 0.1 mol / L AgNO3 / CH3CN. 15 mL of 0.1 mol / L NaClO4 / CH3CN solution was prepared and added to a 25 mL non-split electrochemical cell. 5-Hydroxymethylfurfural (0.5 mmol) and 2,6-dimethylpyridine (0.5 mmol) were added, and the mixture was ultrasonically dissolved for 5 min in an ultrasonic cleaner. The electrochemical cell was then placed in a 25°C constant-temperature water bath and electrolyzed at a constant current of 2 mA. After 8 h of electrolysis, the content of 2,5-diformylfuran in the reaction solution was detected by gas chromatography.

[0104] The Pt electrodes with polymer films attached to their surfaces obtained in Examples 4-7 and Comparative Examples 1-4 were used as working electrodes, and the yields of electrocatalytic oxidation of 5-hydroxymethylfurfural to 2,5-dicarboxyfuran are shown in Table 1.

[0105] Table 1

[0106] Group Yield / % Example 4 94 Example 5 87 Example 6 82 Example 7 90 Comparative Example 1 71 Comparative Example 2 73 Comparative Example 3 79 Comparative Example 4 63

[0107] As shown in Table 1:

[0108] ①As can be seen from the data in Examples 4 to 7, the conductive polymer P (EDOT-TEMPO / BTh) provided by the present invention can be used as a catalyst in the electrochemical catalytic oxidation reaction of 2,5-dicarboxyfuran prepared from 5-hydroxymethylfurfural, which is a biomass platform compound. The heterogeneous electrocatalysis of the reaction has the characteristics of fast reaction and high product yield.

[0109] ② Comparative analysis of Comparative Examples 1-2 and Example 4 shows that the conductive polymer prepared using EDOT-TEMPO and BTh provided by this invention as monomers has a better catalytic effect on the electrochemical catalytic oxidation reaction of 5-hydroxymethylfurfural to 2,5-dicarboxyfuran. In Comparative Example 1, PEDOT-TEMPO obtained by electropolymerization using EDOT-TEMPO as a monomer has the advantage of high conductivity, but its catalytic performance is still poor. In Example 4, the addition of BTh for copolymerization to form a copolymer product greatly improves its catalytic performance. This demonstrates the significant advantage of adding BTh for copolymerization with EDOT derivatives (EDOT-TEMPO) containing TEMPO groups in the side chain. Further analysis reveals that the reason is that BTh copolymerization can not only reduce the oxidation potential and avoid over-oxidation, but also increase the length of the polymer backbone, reduce the steric hindrance of the side chains, and further improve the stability of the polymer. Comparative Example 2 demonstrates that the 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical is more advantageous as a provider of TEMPO structure than the comparative monomer 4-(((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)carbonyl)-2,2,6,6-tetramethylpiperidine-1-oxy radical.

[0110] ③ Comparative analysis of Comparative Examples 3-4 and Example 4 shows that the addition of BTh to form a copolymer with EDOT-TEMPO has a significant impact on the catalytic performance of the copolymer P (EDOT-TEMPO / BTh). The molar ratio of EDOT-TEMPO to BTh in the copolymerization should be in the range of 1:0.2-0.8. Excessive BTh leads to a relatively low content of TEMPO in the copolymer, resulting in poor catalytic performance; insufficient BTh leads to poor structural stability of the copolymer, thus affecting catalytic performance.

[0111] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a conductive polymer containing TEMPO in its side chains, characterized in that: Includes the following steps: (1) Using (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitric oxide radical as reactants, a catalyst and a dehydrating agent are added to carry out the reaction to obtain 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical; (2) A three-electrode system is adopted, with Pt electrodes as the working electrode and auxiliary electrode, and Ag / Ag+ electrode as the reference electrode. In a dichloromethane solution containing tetrabutylammonium perchlorate, monomers 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical and 2,2'-bisthiophene are added to carry out an electropolymerization reaction; wherein, the molar ratio of monomers 4-((4-((2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyryl)oxy)-2,2,6,6-tetramethylpiperidine-1-oxy radical and 2,2'-bisthiophene is 1:0.2~0.8; (3) After the electropolymerization reaction is completed, the surface of the working electrode is rinsed and dried to obtain a conductive polymer film with TEMPO side chains attached to the surface of the working electrode.

2. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of (4-(2,3-dihydrothiophene[3,4-b][1,4]dioxin-2-yl)methoxy)-4-oxobutyric acid and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitric oxide radical is 1:1~1.

5.

3. The preparation method according to claim 1, characterized in that: In step (1), the catalyst is 4-dimethylaminopyridine.

4. The preparation method according to claim 1, characterized in that: In step (1), the dehydrating agent is dicyclohexylcarbodiimide.

5. The preparation method according to claim 1, characterized in that: In step (1), the reaction time is 14-18 hours.

6. The preparation method according to claim 1, characterized in that: In step (2), the molar concentration of tetrabutylammonium perchlorate in the dichloromethane solution is 0.1~0.15 mol / L.

7. The preparation method according to claim 1, characterized in that: In step (2), the polymerization potential of the electropolymerization reaction is -0.5~1.5 V, the scanning speed is 50 mV / s, and the number of scanning cycles is 4~10.

8. The application of the conductive polymer prepared by the preparation method according to any one of claims 1 to 7 in the catalytic generation of 2,5-dicarboxyfuran from 5-hydroxymethylfurfural.

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