Pyridine-porphyrin-based porous organic polymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of gold recovery, in particular to a pyridine-porphyrin-based porous organic polymer as well as a preparation method and application thereof. The pyridine-porphyrin-based porous organic polymer Pyd-PPOPs-Br is reasonably designed and synthesized by integrating a pyridine site with positive charges and a porphyrin part into a framework. When the Pyd-PPOPs-Br is used as an Au (III) recovery adsorbent, the Pyd-PPOPs-Br shows excellent performance, and the obvious adsorption capacity of 3.787 g / g is achieved. In a practical application experiment, the Pyd-PPOPs-Br selectively recovers more than 90% of gold from the electronic waste leachate.

Description

Technical Field

[0001] This invention relates to the field of gold recovery technology, specifically to a pyridine-porphyrin-based porous organic polymer and its preparation method and application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Gold possesses excellent physicochemical properties and plays an indispensable role in many key fields such as instrumentation, electronics manufacturing, catalysts, and medicine. With the continuous increase in the consumption of electronic equipment and catalysts, the demand for gold is also gradually increasing. Furthermore, gold is a non-renewable energy source, leading to a continuous rise in its price and a supply shortage. These electronic wastes contain considerable gold resources, and the proper recycling and utilization of these gold resources is of great significance for environmental protection and resource recycling. However, selective gold recovery still faces challenges due to interference from various metal ions in secondary resources.

[0004] Currently, commonly used gold extraction technologies include membrane separation, electrodeposition, ion exchange, and solvent extraction. Adsorption methods, due to their simplicity, low cost, and environmental friendliness, have shown great potential in the field of metal recovery. For gold recovery, some functional adsorbent materials (such as COP-180, Fe-BTC / PpPDA, and JNM-100-AO) have been reported, exhibiting good selective adsorption capabilities. Efficient recovery of gold (Au) from electronic waste is of great significance for sustainable resource utilization and environmental protection. However, these methods still face two key challenges in practical applications: 1. Extremely low gold content: The gold concentration in electronic waste is usually extremely low, resulting in insufficient recovery efficiency of traditional separation technologies. 2. Interference from complex coexisting metals: The presence of high concentrations of other metal ions (such as Cu, Ni, and Fe) in the system severely interferes with the selective capture of gold. Therefore, given the complex composition and low gold concentration of electronic waste, developing functional adsorbent materials with high selective recognition capabilities, excellent physicochemical stability, and good regeneration performance has become a research hotspot and key research direction in this field. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a pyridine-porphyrin-based porous organic polymer, its preparation method, and its application. This invention prepares a cationic framework-based porphyrin-based POP (Pyd-PPOPs-Br) by integrating an ionic pyridine monomer (DR-1) with pyrrole. This POP exhibits high adsorption capacity and can be used to recover gold from electronic waste leachate.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a pyridine-porphyrin-based porous organic polymer, Pyd-PPOPs-Br, with the following structural formula:

[0008]

[0009] Secondly, the present invention provides a method for preparing the above-mentioned pyridine-porphyrin-based porous organic polymer, specifically comprising the following steps:

[0010] (1) 1,3,5-tris(bromomethyl)benzene and 4-(4-pyridyl)benzaldehyde were mixed and dissolved in an organic solvent in a certain proportion, and the mixture was refluxed for 10-15 h. After the reaction was completed, DR-1 was obtained.

[0011] (2) Mix DR-1 and propionic acid in proportion, add a certain amount of pyrrole, stir under N2 atmosphere, reflux for 10-15 h, and after the reaction is completed, prepare porous organic polymer Pyd-PPOPs-Br.

[0012] The synthesis route is shown below:

[0013]

[0014] Further, in step (1), the molar ratio of 1,3,5-tris(bromomethyl)benzene to 4-(4-pyridyl)benzaldehyde is 0.3-0.5:1; preferably 0.3:1.

[0015] Furthermore, in step (1), the organic solvent is a mixture of DMF and THF, which improves the yield. The volume ratio of DMF to THF is 1-5:1, preferably 1-3:1; more preferably 2:1.

[0016] Further, in step (1), after the reaction is completed, the mixture is cooled to room temperature, and acetone is added to the reaction product mixture to obtain a pale yellow solid precipitate; the precipitate is filtered, washed with acetone, and dried to obtain a pale yellow solid DR-1. The amount of acetone added to the reaction product mixture is 2-5 times the volume of the mixed solvent of DMF and THF.

[0017] Furthermore, in step (2), the molar ratio of DR-1 to pyrrole is 1:2-5.

[0018] Further, in step (2), after the reaction is completed, the solid is cooled to room temperature, centrifuged to separate the solid, and washed with water, THF and methanol in sequence; after freeze-drying for 12 h, the brown-black product Pyd-PPOPs-Br is obtained.

[0019] Thirdly, the present invention provides the application of the pyridine-porphyrin-based porous organic polymer described in the first aspect or the pyridine-porphyrin-based porous organic polymer prepared in the second aspect in the recovery of gold.

[0020] Furthermore, the pyridine-porphyrin-based porous organic polymer of the present invention can perform gold adsorption and recovery under various conditions, such as ideal conditions or conditions with metal ion interference. Therefore, the application of the pyridine-porphyrin-based porous organic polymer of the present invention in gold recovery can also be used for the recovery of gold from circuit boards, gold foil, computer processing units and other electronic waste.

[0021] Furthermore, the metal ion interference can be interference from ions such as Ag(I), Cr(VI), Pd(II), Na(I), K(I), Mn(II), Mg(II), Co(II), Ca(II), Ce(III), Ni(II), Cd(II), Cu(II), and Zn(II).

[0022] Fourthly, the present invention provides a method for recovering gold from a gold-containing solution, specifically comprising the following steps: adding the above-mentioned polymer or the product obtained by the above-mentioned polymer preparation method to a gold-containing solution for adsorption treatment, and then centrifuging and desorbing to recover the gold.

[0023] Further, after adsorption, the solid is collected by centrifugation and washed with acidified thiourea solution and deionized water for desorption; after desorption, the polymer is freeze-dried and recycled.

[0024] Furthermore, the acidified thiourea solution is a mixture of thiourea and hydrochloric acid, where the sulfur in the thiourea can effectively coordinate with gold, achieving efficient gold elution. The mass ratio of thiourea to hydrochloric acid is 1.3:1; the acidified thiourea solution and deionized water are eluted 3 to 5 times each.

[0025] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0026] (1) The pyridine-porphyrin-based porous organic polymer disclosed in this invention has a large specific surface area, suitable pore volume, and abundant active sites, and has a large number of gold adsorption sites, which can achieve effective gold adsorption.

[0027] (2) The pyridine-porphyrin-based porous organic polymer disclosed in this invention achieves gold recovery under the interference of metal ions, exhibiting high selectivity, and the polymer shows good regeneration ability in recycling experiments.

[0028] (3) The preparation method of the pyridine-porphyrin-based porous organic polymer described in this invention is simple, the raw materials are readily available, and it is suitable for industrial production. In addition, the use of mixed solvents during the preparation process improves the reaction yield. Furthermore, the process of recovering gold is simple, requiring only the addition of the polymer to a solution containing gold, followed by centrifugation, elution, and desorption. The operation is simple and feasible. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 This is a schematic diagram illustrating the principle of synthesizing Pyd-PPOPs-Br according to the present invention;

[0031] Figure 2 These are characterization diagrams of Pyd-PPOPs-Br from Example 1, where (a) shows the stability of Pyd-PPOPs-Br in common solvents; (b) shows the TGA image of Pyd-PPOPs-Br; and (c, d) show the FT-IR and FT-IR images of Pyd-PPOPs-Br. 13 CCP / MAS NMR spectra; (e, f) SEM and TEM images of Pyd-PPOPs-Br; (gi) SEM EDS-mapping of PID-PPOPs-Br;

[0032] Figure 3 This is the PXRD spectrum of Pyd-PPOPs-Br in Example 1;

[0033] Figure 4 This is an adsorption performance diagram of Pyd-PPOPs-Br in Example 1; where (a) is the adsorption amount of Pyd-PPOPs-Br at pH 1–11; (b) is the Zeta potential of Pyd-PPOPs-Br at pH 1–9; (c) is the adsorption rate of Pyd-PPOPs-Br at high Au(III) concentration; (d) is the adsorption rate of Pyd-PPOPs-Br at low Au(III) concentration; (e, f) are pseudo-first-order and pseudo-second-order kinetic models of Pyd-PPOPs-Br at high Au(III) concentration; and (g, h) are pseudo-first-order and pseudo-second-order kinetic models of Pyd-PPOPs-Br at low Au(III) concentration.

[0034] Figure 5 These are the N2 adsorption-desorption isotherms and pore size distribution curves of Pyd-PPOPs-Br in Example 1; where (a) is the N2 adsorption-desorption isotherm and (b) is the pore size distribution curve.

[0035] Figure 6This is a graph showing the adsorption performance of gold by Pyd-PPOPs-Br in Example 1; where (a) the effect of the initial concentration of Au(III) on the adsorption capacity of Pyd-PPOPs-Br; (bd) the fitting results of the Langmuir, Freundlich and Temkin models; (e) the selectivity of Pyd-PPOPs-Br; and (f) the effect of different anions on the adsorption performance of Pyd-PPOPs-Br.

[0036] Figure 7 This is a graph showing the changes in elemental content before and after Pyd-PPOPs-Br adsorption in Example 1;

[0037] Figure 8 Characterization diagrams of Pyd-PPOPs-Br or Pyd-PPOPs-Br / Au are shown below; (a) the relationship between temperature and adsorption capacity of Pyd-PPOPs-Br; (b) the linear curve of ln Kc versus 1 / T; (c) XPS spectra of Pyd-PPOPs-Br and Pyd-PPOPs-Br / Au; (d) PXRD patterns of Pyd-PPOPs-Br and Pyd-PPOPs-Br / Au; (e) SEM image of Pyd-PPOPs-Br / Au; (f) EDS mapping of Pyd-PPOPs-Br / Au; (g, h) high-resolution XPS spectra of N1s and Au4f; (i) TEM images of Pyd-PPOPs-Br / Au at different adsorption times; and (j) TEM image of gold particles.

[0038] Figure 9 These are the cyclic voltammetry curves and HOMO-LUMO spectra of Pyd-PPOPs-Br in Example 1; wherein (a) are the cyclic voltammetry curves of ferrocene and Pyd-PPOPs-Br; and (b) are the HOMO-LUMO spectra of Pyd-PPOPs-Br.

[0039] Figure 10 These are the cycling performance diagram and applicable performance diagram of Pyd-PPOPs-Br in Example 1; wherein (a) is the cycling performance diagram of Pyd-PPOPs-Br; and (b) is the applicable performance diagram of Pyd-PPOPs-Br.

[0040] Figure 11 The FTIR spectra and SEM images of recycled Pyd-PPOPs-Br are: (a) FTIR spectra of recycled Pyd-PPOPs-Br; and (b) SEM images of recycled Pyd-PPOPs-Br. Detailed Implementation

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, 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 invention pertains.

[0042] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0043] Example 1: Synthesis of pyridine-porphyrin-based porous organic polymer (Pyd-PPOPs-Br)

[0044] (1) Synthesis of DR-1:

[0045] 1,3,5-Tris(bromomethyl)benzene (107 mg, 0.3 mmol) and 4-(4-pyridyl)benzaldehyde (183 mg, 1 mmol) were added to a mixed solution of DMF (10 mL) and THF (5 mL), and the mixture was refluxed for 12 h. After cooling to room temperature, 50 mL of acetone was poured into the mixture, and a pale yellow solid precipitate was observed. The precipitate was then filtered, washed with acetone, and dried under vacuum to give a pale yellow solid in 52.38% yield.

[0046] (2) Synthesis of pyridine-porphyrin-based porous organic polymers (Pyd-PPOPs-Br):

[0047] DR-1 (151.3 mg, 0.166 mmol) and 15 mL of propionic acid were placed in a 25 mL three-necked flask, followed by the addition of pyrrole (33.6 mg, 0.5 mmol). The mixture was then stirred under a nitrogen atmosphere and refluxed for 12 hours. After cooling to room temperature, the solid was centrifuged and washed successively with water, THF, and methanol. After lyophilization for 12 hours, a brownish-black product was obtained, with a yield of 47.07%.

[0048] Structural characterization and performance testing:

[0049] Pyd-PPOPs-Br is a dark brown, fluffy powder that maintains stability in texture and internal chemical structure in common solvents. Figure 2 a). From Figure 2 Thermogravimetric analysis (TGA) of b showed only a 10% weight loss at 227°C, revealing the excellent thermal stability of Pyd-PPOPs-Br. Fourier transform infrared (FT-IR) and solid-state... 13 CCP / MAS NMR ( 13 The internal chemical structure of Pyd-PPOPs-Br was characterized by C10 NMR spectroscopy, such as... Figure 2 As shown in cd. The 1700 cm⁻¹ region originating from the aldehyde group in DR-1 is absent in the Pyd-PPOPs-Br spectrum.-1 The characteristic peak at 1634 cm⁻¹ indicates that the aldehyde-containing DR-1 has been depleted during polymerization. Conversely, both DR-1 and Pyd-PPOPs-Br exhibit a peak at 1634 cm⁻¹. -1 The C=N stretching vibration peak at 1602 cm⁻¹ indicates that the pyridine unit of DR-1 is retained in the final POP. Furthermore, the peak value at 1602 cm⁻¹ in the Pyd-PPOPs-Br spectrum... -1 The new peak at this location is attributed to the C=N stretching vibration of the porphyrin macrocycle, providing strong evidence for the formation of the porphyrin ring. From... 13 Similar results were obtained in the C1NMR spectrum. The aldehyde signal (195.9 ppm) in the DR-1 spectrum disappeared in the Pyd-PPOPs-Br spectrum, and the characteristic resonance peak of the porphyrin carbon appeared at 108.4 ppm, confirming the presence of the porphyrin unit. The remaining peaks in the 130-160 ppm range belong to aromatic hydrocarbons in Pyd-PPOPs-Br, while the resonance signal at 62.6 ppm belongs to the methylene group in DR-1.

[0050] Powder X-ray diffraction (PXRD) experimental results are as follows: Figure 3 As shown, no diffraction peaks were observed in the small-angle region, indicating the amorphous nature of Pyd-PPOPs-Br. The morphology and microstructure of Pyd-PPOPs-Br were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, as shown... Figure 2 As shown in ef, Pyd-PPOPs-Br exhibits as an aggregate of numerous spherical particles with diameters ranging from 0.3 to 1.5 μm. SEM-EDS reveals that C, N, and Br elements are uniformly dispersed on Pyd-PPOPs-Br, as shown in ef. Figure 2 As shown in gi, this demonstrates the successful construction of the material. Figure 5 The nitrogen adsorption isotherm of a indicates that Pyd-PPOPs-Br exhibits a type III adsorption curve, and the calculated Brunauer-Emmett-Teller (BET) surface area is 11.7 m². 2 / g. The nonlocal density functional theory (NLDFT) model determined the major pore size distribution of Pyd-PPOPs-Br to be in the range of 4.00 to 10.86 nm, highlighting its mesoporous characteristics, such as... Figure 5 As shown in b.

[0051] The effect of pH on the gold adsorption performance of Pyd-PPOPs-Br:

[0052] The effect of pH on adsorption behavior was investigated by mixing Au(III) solution (500 ppm, pH = 1-11) with Pyd-PPOPs-Br and stirring at 298 K for 48 hours. Samples were separated using a 0.45 μm filter membrane, and the Au(III) content in the samples was determined by ICP-AES. The pH was adjusted with diluted HCl and NaOH solutions.

[0053] from Figure 4 As shown in a and Table 1, the adsorption capacity of Pyd-PPOPs-Br is highest at pH 6 (1227 mg / g). On the one hand, the abundant cationic pyridine units endow the material with inherent positive charge properties. Zeta potential test results verify this fact. From... Figure 4 As shown in b and Table 2, the potential value of Pyd-PPOPs-Br is positive in the pH range of 1-9. Considering that the existing form of Au(III) in liquid is the negatively charged AuCl4... - It can interact with the cation sites on Pyd-PPOPs-Br through electrostatic attraction, thus resulting in a superior adsorption capacity.

[0054] Table 1. Adsorption capacity of Pyd-PPOPs-Br at pH 1–11

[0055] pH 1 2 3 4 5 6 7 9 11 <![CDATA[Q e (mg / g)]]> 629.5 604 833.5 896 1012.5 1227 1004 150.5 339

[0056] Table 2. Zeta potentials of Pyd-PPOPs-Br at pH 1–9

[0057] pH 1 2 3 4 5 6 7 9 <![CDATA[Z p (V)]]> 5.99 25.2 27.73 16.97 9.68 13.166 9.393 9.393

[0058] Adsorption kinetics study:

[0059] For kinetic studies, Pyd-PPOPs-Br (20 mg) was mixed with Au(III) solutions of different concentrations (100 ppm and 5 ppm), stirred at 298 K, and samples were taken at different adsorption time points. The samples were separated using a 0.45 μm filter membrane, and the Au(III) content in the samples was determined by ICP-AES.

[0060] like Figure 4 As shown in Figure cd, the time-dependent adsorption curves exhibit rapid absorption rates at both high concentrations (100 ppm) and low concentrations (5 ppm) of Au(III), indicating that Pyd-PPOPs-Br has kinetic efficiency in adsorbing Au(III). Particularly at low Au(III) concentrations, adsorption reaches equilibrium in less than 1 minute, with an adsorption efficiency of approximately 99%. Pseudo-first-order and pseudo-second-order kinetic models, representing physisorption and chemisorption respectively, were used. Figure 4The adsorption rate was analyzed using the quasi-second-order kinetic model (see Table 3). The results showed that the correlation coefficient (Rh) of the quasi-second-order kinetic model was [missing information]. 2 The correlation coefficients (0.99993 and 0.99999) are significantly higher than those of the pseudo-first-order kinetic model (0.84308 and 0.44417), indicating that the significant adsorption rate on Pyd-PPOPs-Br originates from the chemisorption of abundant cation sites on Pyd-PPOPs-Br, and AuCl4 can be effectively adsorbed through electrostatic interactions. - To gain a deeper understanding of the dispersion process of Au(III) on Pyd-PPOPs-Br, the Weber-Morris model was employed. For example... Figure 4 As shown in i, the process is divided into three distinct stages: rapid external surface adsorption, moderate intraparticle diffusion, and slow final equilibrium (Table 4).

[0061] Table 3 Parameters of pseudo-first-order and pseudo-second-order dynamic models

[0062] Kinetic models Parameters Value (100ppm) Value (5ppm) Pseudo-first-order kinetic <![CDATA[k1(min -1 )]]> 0.00316 0.17864 <![CDATA[Q e (mg L -1 )]]> 128.018 1.1675 <![CDATA[R 2 ]]> 0.84308 0.44417 Pseudo-second-order kinetic <![CDATA[k2(g mg -1 min -1 )]]> 0.00011 1.2503 <![CDATA[Q e (mg L -1 )]]> 540.541 19.704 <![CDATA[R 2 ]]> 0.99993 0.99999

[0063] Table 4. Parameters of the Weber-Morris model at different stages

[0064] Stage <![CDATA[k3(mg g 1 min 0.5 )]]> C <![CDATA[R 2 ]]> I 29.93 185.63 0.9502 II 8.096 342.38 0.9930 III 0.224 525.05 0.5267

[0065] Adsorption isotherm experiment:

[0066] In the isothermal experiment, Pyd-PPOPs-Br (2 mg) was mixed with Au(III) solution (pH = 6) at an initial concentration of 100–1500 ppm. After adsorption at 298 K for 48 hours, the sample was separated using a 0.45 μm filter membrane, and the Au(III) content in the sample was determined by ICP-AES.

[0067] By analyzing different initial AuCl4 - Adsorption data collected at concentrations (100-1500 ppm) were used to study the adsorption isotherms of Au(III) by Pyd-PPOPs-Br.

[0068] Figure 6 The results show that Pyd-PPOPs-Br exhibits better adsorption performance at higher Au(III) concentrations. The adsorption capacity reaches 3.787 g / g at adsorption equilibrium. Fitting results (Tables 5-6 and...) Figure 6 The results show that the Langmuir model describes the adsorption behavior of Pyd-PPOPs-Br better than the Freundlich model (0.92679) and the Temkin model (0.94418), respectively. The correlation coefficient (0.98186) indicates that monolayer adsorption plays a crucial role in the adsorption of gold on Pyd-PPOPs-Br.

[0069] Table 5 Selectivity study of adsorption isotherm model parameters of Au(III) on Pyd-PPOPs-Br:

[0070]

[0071] Table 6. Separation Factor RL of the Langmuir Model

[0072] <![CDATA[C0(mg g -1 )]]> <![CDATA[R L ]]> 88.23 0.005253 146.3 0.003175 210.1 0.002213 261.1 0.001781 321 0.001449 428.6 0.001086 551.3 0.000844 632.4 0.000736 740.1 0.000629 913.9 0.00051 1042.8 0.000447 1143.6 0.000407 1267.2 0.000368 1445.6 0.000322 1607.3 0.00029

[0073] Pyd-PPOPs-Br's selectivity for gold

[0074] 3 mg of Pyd-PPOPs-Br was added to 15 mL of a solution containing Ag(I), Au(III), Pd(II), Na(I), K(I), Mn(II), Mg(II), Co(II), Ca(II), Ce(III), Ni(II), Cd(II), Cu(II), Zn(II), and Au(III) ions. The concentration of Au(III) was set to 10 ppm, and the others to 100 ppm. After adsorption at 298 K for 24 h, the sample was separated using a 0.45 μm filter membrane, and the content of all metal ions in the liquid was determined by ICP-AES.

[0075] The sample contained multiple interfering ions, each at a concentration of 100 ppm, which was 10 times higher than that of Au(III). From Figure 6 As shown in Tables e and 7, Pyd-PPOPs-Br exhibits high selectivity for gold capture in the presence of various high concentrations of metal ions, with almost 100% of Au(III) detaching from the solution. Furthermore, we investigated the effect of different anions on the adsorption performance of Pyd-PPOPs-Br. Figure 6 f shows that even in the presence of NO3 - SO4 2- PO4 3- Cl - and F - In this case, Pyd-PPOPs-Br can also achieve almost complete Au(III) recovery.

[0076] Table 7 Adsorption selectivity coefficients of Pyd-PPOPs-Br

[0077] Au / other metalions Selectivity coefficients Au / Ag 4.50000045 Au / Cr 6.333334811 Au / Pd 7.111111111 Au / Na 20.49999488 Au / K 49.92436459 Au / Mn 103.2780452 Au / Mg 121.1974306 Au / Co 179.7494293 Au / Ca 265.6889314 Au / Ce 334.3475208 Au / Ni 625.2735572 Au / Cd 1084.245907 Au / Cu 2229.654404 Au / Zn 2626.05042

[0078] Adsorption thermodynamics experiment:

[0079] Two mg of Pyd-PPOPs-Br was added to 10 mL of 1000 ppm Au(III) solution. The mixture was stirred at pH 6 for a certain period of time at temperatures of 298 K, 308 K, 318 K, and 328 K to perform adsorption thermodynamic tests. After adsorption, the sample was separated using a 0.45 μm filter membrane, and the Au(III) content in the sample was determined by ICP-AES.

[0080] First, the correlation between the adsorption performance of Pyd-PPOPs-Br and temperature change was investigated. Figure 8 (ab). The corresponding thermodynamic parameters were calculated and summarized, as shown in Table 8. The combination of negative ΔG values ​​with positive ΔH and ΔS values ​​indicates that the adsorption of Au(III) onto Pyd-PPOPs-Br is a spontaneous endothermic and entropy-driven process. Subsequently, X-ray photoelectron spectroscopy (XPS), PXRD, SEM, and EDS mapping were used to verify the capture of Au(III) by Pyd-PPOPs-Br. Figure 8 CD-ROM showed new peaks in both XPS and PXRD plots of Pyd-PPOPs-Br after adsorption (Pyd-PPOPs-Br / Au), which may be attributed to the gold absorbed by the material. According to EDS results, the Au content in Pyd-PPOPs-Br / Au increased sharply to 59.85% compared to the original material, while the Br content decreased from 20.64% to 10.42%. Figure 7 ).

[0081] Furthermore, EDS mapping showed that Au elements were uniformly dispersed on the Pyd-PPOPs-Br / Au surface, such as Figure 8 As shown in ef. These phenomena demonstrate that Pyd-PPOPs-Br effectively captures gold ions, which may be attributed to AuCl4. - and Br - Significant ion exchange occurred between them. Then, high-resolution XPS spectra of N1s and Au4f were measured before and after adsorption to understand the interaction between Pyd-PPOPs-Br and Au(III). Figure 8 The binding energies of 398.32 eV, 399.82 eV, and 401.64 eV in the N1s spectrum of Pyd-PPOPs-Br correspond to porphyrin-NH, porphyrin-C=N, and pyridine-N, respectively. After adsorption, their binding energies increase to 398.68 eV, 399.85 eV, and 401.70 eV, respectively, indicating electron transfer between these sites and the adsorbed Au(III). Given the positively charged nature of the pyridine-N sites on Pyd-PPOPs-Br in aqueous solution, the anion AuCl4... -They can bind to them through electrostatic interactions. At the same time, due to their unique molecular structure, porphyrin centers can bind to Au(III) through coordination, resulting in a transfer of binding energy.

[0082] Table 8. Thermodynamic parameters of adsorbed Au(III)

[0083]

[0084] Several new peaks appeared at 2θ at 38.1°, 44.3°, 64.5°, 77.6°, and 81.6° in the PXRD spectrum, corresponding to the (111), (200), (220), (311), and (222) planes of Au(0), respectively. Figure 8 d). Furthermore, in the high-resolution XPS Au4f spectrum of Pyd-PPOPs-Br / Au, the peaks at 88.02 eV and 84.33 eV belong to Au(0)4f, respectively. 5 / 2 and Au(0)4f 7 / 2 ( Figure 8 These observations indicate that the adsorption process is accompanied by reduction, in which Au(III) is reduced to Au(0). To explore the redox mechanism, cyclic voltammetry (CV) experiments were subsequently performed to determine the energy levels of Pyd-PPOPs-Br. Figure 9 The remarkable reducing power of Pyd-PPOPs-Br likely stems from two synergistic effects: firstly, the extensive distribution of porphyrin rings on the Pyd-PPOPs-Br backbone, which serves as active redox sites for its well-known photoredox capabilities; and secondly, the inherent electron-rich π-conjugated framework, which continuously provides electrons for redox reactions.

[0085] There are differences between Pyd-PPOPs-Br and Pyd-PPOPs-Br / Au in the SEM images. Compared with the smooth surface of Pyd-PPOPs-Br, Pyd-PPOPs-Br / Au shows many gold fragments in the SEM images. Figure 8 e). This phenomenon indicates that reduced Au(0) may aggregate and grow into gold particles. To visualize the growth process, sequential TEM images of Pyd-PPOPs-Br / Au at different adsorption times were collected. Figure 8 i). Notably, as adsorption proceeds, gold particles gradually appear and grow, with the largest particle reaching a size of 2 μm. Figure 8 j).

[0086] Cyclic experiment:

[0087] 10 mg of Pyd-PPOPs-Br was mixed with 10 mL of Au(III) aqueous solution (50 ppm, pH = 6) and stirred for 12 hours. After adsorption, the solid was collected by centrifugation, eluted three times each with 10 mL of acidified thiourea solution (10% thiourea + 5% hydrochloric acid) and deionized water, and then freeze-dried before being added to the next adsorption cycle.

[0088] Studies have shown that Au captured on Pyd-PPOPs-Br can be readily eluted by thiourea-hydrochloric acid solution. Even after 8 adsorption-elution cycles, Pyd-PPOPs-Br still effectively captured 0.99 mg of Au(III) (total 1 mg) from the solution. Figure 10 As shown in Figure a. Compared to the unadsorbed Pyd-PPOPs-Br, the overall morphology of the regenerated Pyd-PPOPs-Br remained almost unchanged, as shown in Figure a. Figure 11 As shown in a. Furthermore, the absorption peaks in the FTIR spectrum of the regenerated Pyd-PPOPs-Br are consistent with those of the original material. Figure 11 b). Practical applications of gold recycling from electronic waste:

[0089] The practicality of Pyd-PPOPs-Br was then verified by treating it with leachate from a discarded computer processing unit (CPU). After 30 minutes of treatment, the capture rate reached as high as 90%, demonstrating the rapid adsorption performance of Pyd-PPOPs-Br. Figure 10 b). Therefore, Pyd-PPOPs-Br holds promise for the efficient and selective recovery of gold from real-world e-waste.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pyridine-porphyrin-based porous organic polymer, characterized in that, The pyridine-porphyrin-based porous organic polymer has the following structural formula:

2. The method for preparing the pyridine-porphyrin-based porous organic polymer as described in claim 1, characterized in that, Includes the following steps: (1) 1,3,5-tris(bromomethyl)benzene and 4-(4-pyridyl)benzaldehyde were mixed and dissolved in an organic solvent in a certain proportion, and the mixture was refluxed for 10-15 h. After the reaction was completed, DR-1 was obtained. (2) Mix DR-1 and propionic acid in proportion, add a certain amount of pyrrole, stir under N2 atmosphere, reflux for 10-15 h, and after the reaction is completed, prepare porous organic polymer Pyd-PPOPs-Br. The reaction route is shown below:

3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of 1,3,5-tris(bromomethyl)benzene to 4-(4-pyridyl)benzaldehyde is 0.3-0.5:1, preferably 0.3:

1.

4. The preparation method according to claim 2, characterized in that, In step (1), the organic solvent is a mixture of DMF and THF, wherein the volume ratio of DMF to THF is 1-5:1, preferably 1-3:1, and more preferably 2:

1.

5. The preparation method according to claim 2, characterized in that, In step (1), after the reaction is completed, the mixture is cooled to room temperature and acetone is added to the reaction product mixture to obtain a pale yellow solid precipitate. The precipitate is filtered, washed with acetone, and dried to obtain a pale yellow solid DR-1.

6. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of DR-1 to pyrrole is 1:2-5.

7. The preparation method according to claim 2, characterized in that, In step (2), after the reaction is completed, the solid is cooled to room temperature, centrifuged to separate the solid, and washed with water, THF and methanol in sequence; after freeze-drying for 12 h, the brown-black product Pyd-PPOPs-Br is obtained.

8. The application of the pyridine-porphyrin-based porous organic polymer as described in claim 1 in the recovery of gold.

9. The application as described in claim 8, characterized in that, The pyridine-porphyrin-based porous organic polymer can be used for the recovery of gold from circuit boards, gold foil, computer processing units, and other electronic waste.

10. A method for recovering gold from a gold-containing solution, characterized in that, The process includes the following steps: adding the pyridine-porphyrin-based porous organic polymer of claim 1 into a gold-containing solution for adsorption treatment, followed by centrifugation and desorption to recover the gold.

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