A porphyrin-based COFs for gold recovery and its preparation method and application

Abstract

A porphyrin-based COFs for gold recovery and its preparation method and application, wherein the method comprises: using 1,2-dichlorobenzene and n-butanol as solvents, mixing 5,10,15,20-tetrakis(4-aminophenyl)porphyrin monomer and 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-diformaldehyde monomer, and adding anhydrous acetic acid as a catalyst to react under N2 protection; after the reaction is completed, washing with distilled water, anhydrous ethanol, acetone and dichloromethane, filtering by suction, and drying to obtain a porphyrin-based COFs material. The synthesis process of the porphyrin-based COFs of the present invention is simple, and its application in the treatment of wastewater containing gold ions is expected to provide an effective way to solve the problems of large environmental pollution and high energy consumption in the gold recovery process. The porphyrin-based COFs of the present invention are applied to gold recovery, combining the structural characteristics of COFs and the characteristics of photocatalytic reduction, can achieve efficient adsorption and recovery of gold, simple operation, green and environmentally friendly, and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of COFs materials, and in particular to porphyrin-based COFs for gold recovery, and a preparation method and application thereof. Background Art

[0002] Global electronic waste production averages approximately 50 million tons per year. The wastewater leached from electronic waste is rich in precious metals such as gold, silver, and platinum. Gold (Au), a precious metal resource, is widely used in various industries, including semiconductors, healthcare, and jewelry, due to its excellent ductility, good conductivity, and chemical stability. Traditional gold extraction methods, including mechanical and hydrometallurgical methods, both involve the use of toxic chemicals and pose significant environmental risks. Therefore, it is imperative to develop an efficient, low-pollution, and low-energy method for extracting and recovering gold from acidic electronic waste leachate.

[0003] The adsorption method has the advantages of low chemical consumption, low space requirements, and simple operation. There are many adsorption materials currently on the market, among which covalent organic frameworks (COFs) are crystalline materials with an ordered porous structure formed by covalently connecting light elements such as C, O, N, and B. They have the characteristics of ordered pores, large specific surface area, and designable functional groups, and have great potential in the adsorption of Au.

[0004] One of the major limitations of all adsorbents is the process of removing the adsorbed Au to recover the Au and regenerate the adsorbent, which is a particularly important consideration for effective but expensive adsorbents such as CNTs. Recovery of Au from adsorbents typically involves the use of strong acids or mixed reagents, which increases costs through chemical consumption, increases disposal risks, and adds additional environmental challenges during processing. The structural characteristics of COFs are conducive to improving the light collection rate and diffusion of catalytic species, and have great potential in photocatalytic reduction. Therefore, how to use COFs to treat gold-contaminated wastewater and recover gold at low cost and high efficiency remains a focus of current research. Summary of the Invention

[0005] Based on the technical problems existing in the technology, the present invention provides an environmentally friendly and efficient gold recovery material to solve the problems of high pollution and high energy consumption of gold recovery materials in the existing technology, and provides an environmentally friendly and efficient gold recovery material.

[0006] To achieve the above objectives, on the one hand, the present invention provides porphyrin-based COFs for gold recovery, which have the following structural formula:

[0007]

[0008] Porphyrin has a large conjugated structure with 18 π electrons and excellent visible light absorption capacity, and its large conjugated structure provides a stable node for constructing the COF topology. 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) is combined with 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde (DTD) to construct a porous adsorption material with a large specific surface area. According to another aspect of the present invention, the present invention also provides a method for preparing porphyrin-based COFs, characterized in that it comprises the following steps:

[0009] S1. dissolving 5,10,15,20-tetrakis(4-aminophenyl)porphyrin monomer and 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde monomer in a mixed solvent containing two organic solvents, mixing well, adding anhydrous acetic acid as a catalyst, and reacting under N2 protection;

[0010] S2. After the reaction is completed, the product is washed with distilled water, anhydrous ethanol, acetone and dichloromethane, filtered and dried to obtain a porphyrin-based COFs material.

[0011] As a further preferred technical solution of the present invention, in step S1, the molar ratio of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin monomer to 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde monomer is (0.5-3):1; and / or, 5,10,15,20-tetrakis(4-aminophenyl)porphyrin monomer is added to the mixed solvent at a concentration of 0.01 to 0.05 mol / L, and 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde monomer is added to the mixed solvent at a concentration of 0.02 to 0.05 mol / L.

[0012] As a further preferred technical solution of the present invention, in step S1, the mixed solvent is a mixture of any two of xylene, 1,12-dichlorobenzene, benzyl alcohol, 1,4-dioxane, ethyl acetate, n-hexane, and diethyl ether.

[0013] As a further preferred technical solution of the present invention, in step S1, the amount of the catalyst is 1% to 10% of the total volume of 1,2-dichlorobenzene and n-butanol.

[0014] As a further preferred technical solution of the present invention, in step S2, the reaction temperature is 120° C. and the reaction time is 48 to 72 hours.

[0015] As a further preferred technical solution of the present invention, the 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde monomer is synthesized by the following steps:

[0016] 1,4-Dibromo-2,5-dimethoxybenzene, 4-formylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and sodium carbonate were dissolved in a toluene aqueous solution and heated under nitrogen protection for reaction. After the reaction, the product was poured into deionized water, extracted with dichloromethane, and dried over anhydrous sodium sulfate to obtain a crude product of 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde, which was finally separated and purified by silica gel column chromatography and analyzed by chromatography.

[0017] According to another aspect of the present invention, the present invention also provides an application of porphyrin-based COFs in gold recovery.

[0018] As a further preferred technical solution of the present invention, porphyrin-based COFs are added to a solution containing gold ions, and the porphyrin-based COFs have a reductive adsorption effect on the gold ions, reducing the gold ions to obtain elemental gold.

[0019] Compared with the existing technology, the following beneficial effects can be achieved:

[0020] 1) The synthesis process of the porphyrin-based COFs of the present invention is simple. Its application in the treatment of wastewater containing gold ions is expected to provide an effective way to solve the problems of severe environmental pollution and high energy consumption in the gold recovery process.

[0021] 2) The porphyrin-based COFs of the present invention are applied to gold recovery, which combines the structural characteristics of COFs with the characteristics of photocatalytic reduction, can achieve efficient adsorption and recovery of gold, is simple to operate, is green and environmentally friendly, and has low cost.

[0022] 3) Photocatalytic reduction has the advantages of low cost and environmental friendliness. The process primarily involves the absorption of light by the material, which generates photogenerated electrons and holes, followed by reduction reactions on the photogenerated electrons and oxidation reactions on the photogenerated holes. The present invention utilizes porphyrin-based COFs to reduce Au(III) to Au(0), which not only helps increase adsorption capacity but also facilitates subsequent elution of Au from the adsorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 The synthetic route of porphyrin-based COFs in Example 1;

[0025] Figure 2 is the NMR 1H spectrum of 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde (DTD) in Example 1;

[0026] Figure 3FTIR spectra of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) and porphyrin-based COFs (TAPP-DTD-COF) in Example 1;

[0027] Figure 4 (a) UV-vis absorption spectrum of TAPP-DTD-COF and TAPP in Example 1; (b) Tauc plot; (c) XPS spectrum; (d) band structure;

[0028] Figure 5 This is the EDS image of TAPP-DTD-COFs before gold ion adsorption in Example 1;

[0029] Figure 6 This is the EDS graph of TAPP-DTD-COFs after gold ion adsorption in Example 1;

[0030] Figure 7 The adsorption and removal rate of gold ions by TAPP-DTD-COF in Example 1, (a) the adsorption and removal rate of TAPP-DTD-COF under light and dark conditions; (b) XPS Au 4f after adsorption under light.

[0031] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0032] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0033] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0034] Example 1

[0035] See Figure 1 The present embodiment provides an environmentally friendly and efficient method for preparing porphyrin-based COFs with gold recovery, which is as follows:

[0036] Step 1: Preparation of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) monomer

[0037] Add 1 g (0.0016 mol) of tetraphenylporphyrin to a three-necked flask, use CHCl3 as the solvent, and stir at 0°C for 10 min under N2 protection. Slowly add 2.28 mL (0.0512 mol) of fuming nitric acid using a dropping funnel. After the addition is complete, continue the reaction for 1 h. After quenching the reaction with excess ammonia water, wait for the solution to return to room temperature, extract, recrystallize, and dry in vacuo to obtain a crude purple 5,10,15,20-tetrakis(tetranitrophenyl)porphyrin product.

[0038] Dissolve 0.40 mol of crude 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin in 80 mL of concentrated hydrochloric acid, add 20 mL of a concentrated hydrochloric acid solution of 0.088 mol of stannous chloride, and stir for 2 hours. Heat to 65°C and react for 0.5 hours. Cool in an ice-water bath to separate a dark green tetraaminophenyl hydrochloride solid, which is then dispersed in 200 mL of deionized water. Neutralize with concentrated ammonia to pH 8, filter, and vacuum dry the resulting brown-purple solid.

[0039] The brown-purple solid product was dissolved in acetone, filtered to obtain a deep red solution, and dried to obtain blue-purple crystals, which were separated by column chromatography and analyzed by chromatography.

[0040] Step 2: Synthesis of 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde (DTD) monomer

[0041] 0.2 mmol of 1,4-dibromo-2,5-dimethoxybenzene, 1 mmol of 4-formylphenylboronic acid, 0.03 mmol of tetrakis(triphenylphosphine)palladium, 1 mmol of sodium carbonate, 1 mL of water, and 5 mL of toluene were added to a reaction tube, and the mixture was reacted at 90°C for 10 h under nitrogen protection. After the reaction, the mixture was poured into water, extracted with dichloromethane three times, and dried over anhydrous sodium sulfate. Finally, the crude product was purified on a silica gel column with an eluent of dichloromethane:petroleum ether = 3:2 to obtain a green solid, which was then analyzed by chromatography.

[0042] Step 3: Synthesis of TAPP-DTD3-COF

[0043] 0.01 mmol TAPP monomer and 0.02 mmol DTD monomer were weighed into a reaction tube, 5 ml dichlorobenzene and 5 ml n-butanol were added, and after ultrasonication for 10 min, 1 ml anhydrous acetic acid was added, and then the mixture was reacted at 120°C under N2 protection for 72 h.

[0044] After the reaction, the product was washed with distilled water, anhydrous ethanol, acetone, and dichloromethane in sequence, filtered, and dried at 100°C for 24 hours to obtain porphyrin-based COFs.

[0045] In this example, 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) was combined with 2',5'-dimethoxy-[1,1':4',1"-terphenyl]-4,4"-dicarbaldehyde (DTD) to prepare a porous COFs adsorption material with a large specific surface area, which has multiple absorption peaks in the entire visible light range, such as Figure 2 and 3 As shown. Figure 4 As shown, by drawing the Tauc curve of TAPP-DTD-COF, it is found that its optical band gap is 2.12eV, indicating its strong light absorption ability. The XPS band spectrum infers that the lowest unoccupied molecular orbital (LUMO) energy level of TAPP-DTD-COF is -0.83eV, which is higher than E Au(III) The reduction potential of 1.49 V is more negative, indicating that the photocatalytic reduction of Au(III) to Au(0) is favorable from a thermodynamic point of view.

[0046] The TAPP-DTD3-COF prepared above was applied to gold recovery.

[0047] 10 mg of TAPP-DTD-COF sample was placed in 100 mL of AuCl4Na solution with an initial Au(III) content of 100 ppm, and comparative experiments were carried out in dark and light environments. Figure 7 As shown in (a), the adsorption removal rate of gold ions by TAPP-DTD-COF in a dark environment is as high as 97.4%, and in a light environment it is as high as 98%. This shows that this material has a high removal rate for Au(III). Figure 5 and Figure 6 As shown in the EDS diagram before and after adsorption, it can be seen that TAPP-DTD3-COF effectively adsorbs Au(III). Figure 7 (b) The XPS Au 4f image under light conditions shows that TAPP-DTD-COF reduces most of the Au(III) to Au(0), proving that this material also has the ability to adsorb Au(III) and reduce it to Au(0) in practical applications.

[0048] Examples 2 and 3

[0049] The preparation method was basically the same as that in Example 1, except that the ratio of TAPP monomer and DTD monomer used in step 3 was different. In Example 2, the TAPP monomer and DTD monomer were both 0.02 mmol, while in Example 3, the TAPP monomer and DTD monomer were 0.02 mmol and 0.03 mmol, respectively.

[0050] The TAPP-DTD3-COF prepared by methods 2 and 3 was used to recover gold, and the adsorption removal rate of gold ions was tested, which was more than 97% in a dark environment and more than 98% in a light environment.

[0051] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A porphyrin-based COFs for gold recovery, characterized in that: The structural formula of the porphyrin-based COFs is: 。 2. A method for preparing porphyrin-based COFs according to claim 1, characterized in that: The following steps are involved: S1. Dissolve 5,10,15,20-tetrakis(4-aminophenyl)porphyrin monomer and 2',5'-dimethoxy-[1,1':4',1''-terphenyl]-4,4''-dicarbaldehyde monomer in a mixed solvent containing two organic solvents, mix well, add anhydrous acetic acid as a catalyst, and react under N2 protection; S2. After the reaction in step S1 is completed, the product is washed with distilled water, anhydrous ethanol, acetone and dichloromethane, filtered and dried to obtain a porphyrin-based COFs material.

3. The method for preparing porphyrin-based COFs for recovering gold according to claim 2, wherein In step S1, the molar ratio of the 5,10,15,20-tetrakis(4-aminophenyl)porphyrin monomer to the 2',5'-dimethoxy-[1,1':4',1''-terphenyl]-4,4''-dicarbaldehyde monomer is (0.5-3):1; and / or the 5,10,15,20-tetrakis(4-aminophenyl)porphyrin monomer is added to the mixed solvent at a concentration of 0.01-0.05 mol / L, and the 2',5'-dimethoxy-[1,1':4',1''-terphenyl]-4,4''-dicarbaldehyde monomer is added to the mixed solvent at a concentration of 0.02-0.05 mol / L.

4. The method for preparing porphyrin-based COFs for recovering gold according to claim 2, wherein In step S1, the mixed solvent is a mixture of any two of xylene, 1,12-dichlorobenzene, benzyl alcohol, 1,4-dioxane, ethyl acetate, n-hexane, and diethyl ether.

5. The method for preparing porphyrin-based COFs for recovering gold according to claim 2, wherein In step S1, the amount of catalyst used is 1% to 10% of the total volume of the mixed solvent.

6. The method for preparing porphyrin-based COFs for recovering gold according to claim 2, wherein In step S1, the reaction temperature is 120° C. and the reaction time is 48 to 72 h.

7. The method for preparing porphyrin-based COFs for gold recovery according to claim 2, wherein: The 2',5'-dimethoxy-[1,1':4',1''-terphenyl]-4,4''-dicarbaldehyde monomer is synthesized by the following steps: 1,4-Dibromo-2,5-dimethoxybenzene, 4-formylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and sodium carbonate were dissolved in a toluene aqueous solution and heated to react under nitrogen protection. After the reaction, the product was poured into deionized water, extracted with dichloromethane, and dried over anhydrous sodium sulfate to obtain a crude product of 2',5'-dimethoxy-[1,1':4',1''-terphenyl]-4,4''-dicarbaldehyde, which was finally separated and purified by silica gel column chromatography and analyzed by chromatography.

8. Use of the porphyrin-based COFs according to claim 1 and the porphyrin-based COFs prepared by the method according to any one of claims 2 to 7 in recovering gold.

9. The use according to claim 8, characterized in that Porphyrin-based COFs are added to a solution containing gold ions, and the porphyrin-based COFs act as a reductive adsorbent on the gold ions, reducing the gold ions to obtain elemental gold.

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