Porous organic polymer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of adsorption, and relates to a porous organic polymer as well as a preparation method and application thereof. The structural formula of the porous organic polymer TB-POP is as follows: # imgabs0 # TB-POP molecules contain S and N functional groups which are chelated and coordinated with Au (III), so that selective adsorption of gold ions is realized, a pi-conjugated system of the TB-POP is expanded by carbon-carbon double bonds, the capability of electron donating reduction of Au (III) by the TB-POP is remarkably improved, and the adsorption performance of the TB-POP on Au (III) is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of gold recovery, and in particular relates to a porous organic polymer and a preparation method and application thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Gold, with its excellent physical and chemical properties, plays an indispensable role in numerous key fields, including instrumentation, electronics manufacturing, catalysis, and healthcare. With the continued increase in the consumption of electronic equipment and catalysts, the use of gold has also been steadily increasing. Furthermore, gold is a non-renewable energy source, contributing to its rising price and supply shortages. These electronic wastes contain considerable gold resources, and proper recycling of these resources would be of great significance for environmental protection and resource recycling. However, the selective recovery of gold remains challenging due to interference from various metal ions in secondary resources.

[0004] At present, gold recovery technologies mainly include precipitation, ion exchange, solvent extraction, adsorption and other methods. However, most technologies still have many problems, such as the need to introduce organic solvents, high cost, low efficiency, high labor intensity and easy secondary pollution to the environment. Among the various separation technologies, the adsorption method has attracted widespread attention due to its advantages such as environmental friendliness, low cost, few by-products and easy operation. However, the inventors found that most adsorption materials lack rich functional groups, have poor adsorption properties, poor selectivity for gold, and poor repeatability. Therefore, the research and development of functional adsorption materials with high selective recognition ability, excellent physical and chemical 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 the shortcomings of the prior art, the present invention aims to provide a porous organic polymer and its preparation method and application. The porous organic polymer of the present invention has the advantages of significant adsorption capacity, fast adsorption kinetics, good stability, outstanding selectivity and recyclability.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] In a first aspect, the present invention provides a porous organic polymer TB-POP, the structural chemical formula of which is:

[0008]

[0009] In a second aspect, the present invention provides a method for preparing the porous organic polymer TB-POP, comprising the following steps:

[0010] 1,3,5-Tris(4-cyanomethyl)benzene (TCPB) and 2,5-bis(methylthio)terephthalaldehyde (BMTTPA) are mixed and dissolved in a first solvent in appropriate proportions. An alkaline catalyst is added to the mixture and mixed thoroughly. The mixture is then reacted at 100-140°C for 60-90 hours. TB-POP is obtained after the reaction is complete.

[0011] Furthermore, the first solvent is selected from one or a mixed solvent of 1,4-dioxane, mesitylene, isopropylbenzene, diethylene glycol dimethyl ether, etc., to ensure that the solvent can dissolve 1,3,5-tris(4-cyanomethylbenzene)benzene and 2,5-bis(methylthio)terephthalaldehyde at the same time, thereby ensuring that the reaction can proceed more fully.

[0012] Furthermore, the alkaline catalyst is selected from any one of sodium hydroxide and potassium hydroxide, and the concentration of the sodium hydroxide solution or potassium hydroxide solution is 2-5 mol·L -1 .

[0013] Furthermore, the molar ratio of 1,3,5-tris(4-cyanomethylbenzene)benzene to 2,5-bis(methylthio)terephthalaldehyde is 1:1-3.

[0014] Furthermore, the mixing process of the 1,3,5-tris(4-cyanomethylbenzene)benzene, 2,5-bis(methylthio)terephthalaldehyde and the catalyst is performed by ultrasonic-assisted dissolution, and the ultrasonic time is preferably 2-10 minutes.

[0015] Furthermore, after the reaction is completed, the reaction product is washed, solvent extracted, and dried to obtain TB-POP.

[0016] After the reaction is completed, the polymer is washed with N,N-dimethylformamide (DMF), acetone (ACE), and tetrahydrofuran (THF). Washing can dissolve unconsumed raw materials or oligomers. If washing is not performed, unconsumed raw materials or oligomers may adhere to the polymer surface, failing to fully expose adsorption sites and affecting subsequent adsorption and separation of gold.

[0017] The solvent extraction is Soxhlet extraction, and the extraction solvent is THF, which further removes unreacted monomers.

[0018] The drying operation is carried out in a vacuum drying oven at 80-100°C.

[0019] In a third aspect, the present invention provides the use of the porous organic polymer or a product prepared from the porous organic polymer in gold recovery.

[0020] The beneficial effects of the present invention are:

[0021] (1) The irreversible C=C connection structure in the porous organic polymer prepared by the present invention gives the material good thermal stability and chemical stability, enabling it to maintain the stability of the chemical structure under harsh conditions such as high temperature, strong acid and strong base, thus providing a guarantee for the long-term stable Au(III) adsorption process.

[0022] (2) Based on the theory of hard and soft acid-base, the electron-rich groups methylthio (-SCH3) and cyano (-CN) in the material act as soft base groups and easily undergo coordination and chelation with gold ions (soft acid), thereby achieving specific recognition and efficient capture of gold ions (maximum theoretical adsorption capacity of 925 mg g -1 ).

[0023] (3) The carbon-carbon double bond expands the π-conjugated system of TB-POP, which is beneficial to the electron transition under photoexcitation and significantly enhances the ability of TB-POP to donate electrons to reduce Au(III), thereby further improving the adsorption performance of Au(III). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is an infrared spectrum of TB-POP prepared in an embodiment of the present invention;

[0026] Figure 2 TB-POP prepared in accordance with the present invention 13 C CP / MAS NMR spectrum;

[0027] Figure 3 The scanning electron microscope image and EDS element scanning image of TB-POP prepared in an embodiment of the present invention; wherein, (a) is a scanning electron microscope image, and (b) is an EDS element scanning image;

[0028] Figure 4 FT-IR spectra of TB-POP prepared in an embodiment of the present invention after being immersed in different media for 3 days;

[0029] Figure 5 This is a TGA graph of TB-POP prepared in an embodiment of the present invention;

[0030] Figure 6 N2 adsorption-desorption isotherms of TB-POP prepared in the embodiment of the present invention;

[0031] Figure 7This is the pore size distribution diagram of TB-POP prepared in an embodiment of the present invention;

[0032] Figure 8 The adsorption amount of Au(III) by TB-POP prepared in the embodiment of the present invention at different pH values;

[0033] Figure 9 The zeta potential values of TB-POP prepared in the embodiment of the present invention at different pH values;

[0034] Figure 10 The effect of adsorption time on the adsorption efficiency of Au(III) by TB-POP prepared in the embodiment of the present invention;

[0035] Figure 11 Fitting the adsorption kinetics of Au(III) by TB-POP prepared in the embodiment of the present invention;

[0036] Figure 12 Langmuir and Freundlich adsorption isotherm models of TB-POP prepared in an embodiment of the present invention under dark conditions and light conditions; (a) is the Langmuir and Freundlich adsorption isotherm model under dark conditions; (b) is the Langmuir and Freundlich adsorption isotherm model under dark conditions;

[0037] Figure 13 The adsorption efficiency of TB-POP prepared in the embodiment of the present invention for different metal ions in the simulated actual leachate;

[0038] Figure 14 The adsorption efficiency of TB-POP prepared in the embodiment of the present invention at different times of use;

[0039] Figure 15 FT-IR spectrum of TB-POP prepared in an embodiment of the present invention after 5 adsorption-desorption cycles;

[0040] Figure 16 This is the full XPS spectrum of TB-POP prepared in an embodiment of the present invention before and after adsorption;

[0041] Figure 17 is the Au 4f spectrum of TB-POP-Au;

[0042] Figure 18 is the PXRD pattern of TB-POP-Au;

[0043] Figure 19 TEM image of TB-POP-Au;

[0044] Figure 20The S2p and N1s spectra of TB-POP prepared in an embodiment of the present invention before and after Au adsorption; wherein, (a) is the S2p spectrum; (b) is the N1s spectrum;

[0045] Figure 21 FT-IR spectra of TB-POP prepared in an embodiment of the present invention before and after Au adsorption;

[0046] Figure 22 UV-visible-near-infrared diffuse reflectance spectrum of TB-POP prepared in an embodiment of the present invention;

[0047] Figure 23 This is the Tauc plot of TB-POP prepared in an embodiment of the present invention;

[0048] Figure 24 CV curves of Ferrocene and TB-POP prepared in the examples of the present invention;

[0049] Figure 25 Schematic diagram of the redox reaction mechanism proposed based on the energy level perspective;

[0050] Figure 26 This is the reaction scheme of Example 1 of the present invention. DETAILED DESCRIPTION

[0051] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0052] The present invention will be further described below with reference to the embodiments.

[0053] Example 1: Synthesis of TCPB-BMTTPA-POP (TB-POP)

[0054] First, 1,3,5-tris(4-cyanomethylbenzene)benzene (TCPB) (84.70 mg, 0.2 mmol) and 2,5-bis(methylthio)terephthalaldehyde (BMTTPA) (67.90 mg, 0.3 mmol) were added to the polytetrafluoroethylene lining of the reactor, and then 1,4-dioxane (10 mL) and mesitylene (2 mL) were added as solvents. Ultrasonication was performed for 5 minutes to fully dissolve the monomers. Then, 4 mol·L - 1NaOH solution (1.2 mL) was used as a catalyst, and then ultrasonicated for 5 minutes to mix the components evenly. Afterwards, the liner was placed in a reactor and transferred to an oven for reaction at 120°C for three days. After the reaction, the product was washed three times with N,N-dimethylformamide (DMF), acetone (ACE), and tetrahydrofuran (THF), respectively. Soxhlet extraction was then performed using THF as a solvent to further remove unreacted monomers. Finally, the product was dried in a vacuum drying oven at 80°C to obtain 111.86 mg of orange-red solid powder with a yield of 78.89%.

[0055] Fourier transform infrared spectrum of TB-POP

[0056] The chemical structure of TB-POP was characterized by Fourier transform infrared spectroscopy (FT-IR). Figure 1 As shown in the FT-IR spectrum, 2250 cm –1 The absorption peak at 1430 cm-1 belongs to the characteristic stretching vibration peak of the cyano group (-CN) of TCPB monomer, while the absorption peak at 1430 cm-1 belongs to the characteristic stretching vibration peak of the cyano group (-CN) of TCPB monomer. –1 、1679cm –1 and 2918cm –1 The peaks at 1679cm and 1689cm correspond to the stretching vibration peaks of the aldehyde group (-CHO), the bending vibration peaks of the CSC bond, and the stretching vibration peaks of the methyl group (CH) of the BMPPTA monomer. –1 ) completely disappears, and at 1595cm –1 A new characteristic vibration absorption peak of the carbon-carbon double bond (C=C) appears at 2211 cm-1, indicating that the aldehyde group participates in the condensation reaction and forms a C=C structure. In addition, the TB-POP spectrum retains the bending vibration peaks of the methyl group (CH) and CSC from the BMPPT monomer at the same position. At the same time, the characteristic peak of -CN from the TCPB monomer is also retained and shifted to 2211 cm-1. –1 Comprehensive analysis showed that BMPPTA and TCPB were successfully constructed through Knoevenagel condensation reaction to form a porous organic polymer (TB-POP) with C=C as the connecting unit.

[0057] TB-POP solid state 13 C NMR spectroscopy

[0058] Further carbon-13 cross-polarization magic angle spinning nuclear magnetic resonance ( 13 The chemical structure of TB-POP was analyzed by C CP / MAS NMR ( Figure 2). No characteristic peak of aldehyde carbon was detected at 190ppm in the NMR spectrum, confirming that the aldehyde group has fully participated in the condensation process. The characteristic peaks at 139ppm and 111ppm in the spectrum correspond to the chemical shifts of the two unequal carbon atoms in the newly generated C=C, while the signals at 126ppm and 15ppm are attributed to the nitrile carbon and the terminal carbon atom of the methylthio group, respectively. Comprehensive analysis of the above experimental results, through FT-IR and 13 The collaborative characterization of C CP / MAS NMR confirmed the successful construction of the C=C-linked porous organic polymer.

[0059] Morphological characterization of TB-POP

[0060] The microstructure of TB-POP was characterized by scanning electron microscopy (SEM). Figure 3 As shown in (a), TB-POP is irregular in shape and is composed of micron-sized rough spherical particles. Further characterization by energy dispersive X-ray spectroscopy (EDS) revealed that Figure 3 As shown in (b), the three characteristic elements C, N, and S show highly uniform spatial distribution characteristics in the TB-POP skeleton, indicating that the monomer molecules form a structure with uniform chemical composition during the condensation process.

[0061] Stability of TB-POP

[0062] To evaluate the chemical stability of TB-POP materials, they were placed in water and hydrochloric acid solution (1 mol·L –1 ), sodium hydroxide solution (1 mol·L –1 After immersing in THF, DMF and other media for 3 days, FT-IR was used to characterize and analyze its chemical structure. Figure 4 As shown in the figure, after being treated with different chemical media, the characteristic peak positions and intensities of the materials did not change significantly, which was highly consistent with the spectral characteristics of the untreated samples. In addition, the thermal stability of TB-POP was investigated by thermogravimetric analysis (TGA). Figure 5 As shown, when the temperature reaches 336°C, its mass decreases by only 10%, and the main weight loss phase occurs after 300°C, indicating its excellent thermal stability. In summary, the experimental analysis shows that TB-POP maintains its intact chemical structure in strong acids, strong bases, organic solvents, and at high temperatures. In particular, the material's structural integrity in strong acidic media effectively prevents adsorption performance degradation caused by skeleton degradation or functional group loss, thereby ensuring its long-term effectiveness and reusability in gold recovery applications.

[0063] Porosity characterization of TB-POP

[0064] The porosity of TB-POP was characterized by nitrogen adsorption-desorption isotherm test. Figure 6 The analysis results show that the material has good specific surface area characteristics, and its BET specific surface area reaches 84m 2 ·g –1 , and the Langmuir specific surface area based on the monolayer adsorption model is as high as 341m 2 ·g –1 This high specific surface area provides TB-POP with abundant active sites, which can effectively improve its capture ability and adsorption capacity of target molecules. In addition, its pore size distribution is concentrated in the range of 2-50nm, indicating that TB-POP is a mesoporous material ( Figure 7 ).

[0065] Effect of pH Value of Au(Ⅲ) Solution on Adsorption Performance of TB-POP

[0066] In order to explore the effect of pH on the adsorption performance of Au(III) by TB-POP, a series of adsorption experiments were carried out in the pH range of 2-9. Figure 8 As shown in the figure, the adsorption capacity of TB-POP for Au(III) exceeded 800 mg·g in the pH range of 2 to 5. –1 , where the adsorption capacity reaches its maximum value (1037 mg·g –1 Under neutral conditions, the adsorption capacity of Au(III) by TB-POP can still reach 305 mg·g –1 However, under alkaline conditions, the adsorption capacity of TB-POP for Au(III) is almost lost. In this regard, the zeta potential test was performed and the test results are as follows: Figure 9 When the pH value is lower than 2.55, the surface of TB-POP is positively charged, and the main form of Au(III) is AuCl4 - Therefore, the positively charged TB-POP can effectively capture AuCl4 through electrostatic interaction. - , thus showing a higher adsorption capacity. When the pH value is higher than 2.55, the surface zeta potential of TB-POP becomes negative, resulting in electrostatic repulsion between it and the negatively charged Au(III) species, inhibiting the adsorption process and thus reducing the adsorption capacity. It is worth noting that although the TB-POP surface is strongly negatively charged (-41mV) at pH = 4, and theoretically there is no electrostatic attraction with Au(III) species, the adsorption capacity of TB-POP at this pH value is still as high as 895mg·g –1 This indicates that in addition to electrostatic interactions, there are other mechanisms (coordination, chelation, redox, etc.) that allow TB-POP to maintain a high adsorption capacity. In addition, as the pH increases, AuCl4- The ions will gradually hydrolyze and convert into hydroxide complexes, such as AuCl3(OH) - , AuCl2(OH)2 - , AuCl(OH)3 - These complexes are generally difficult to adsorb, especially under alkaline conditions. This inhibitory effect is particularly pronounced, resulting in a near-complete loss of TB-POP's adsorption capacity for Au(III). Considering that industrial wastewater and electronic waste leachates are often acidic, TB-POP's excellent adsorption performance at low pH values provides a strong foundation for its practical application.

[0067] Adsorption kinetics of TB-POP

[0068] In this experiment, the Au(Ⅲ) adsorption efficiency of TB-POP at different times was investigated. Figure 10 It can be seen that in the initial stage of adsorption, the adsorption efficiency of TB-POP for Au(III) showed a rapid upward trend, reaching 83.92% within 5 hours; as the adsorption time prolonged, the growth rate of the adsorption efficiency gradually slowed down, reaching 98.81% at 24 hours. The results show that the material has a rapid adsorption rate for Au(III).

[0069] In order to further explore the adsorption kinetics of Au(Ⅲ) by TB-POP, this study used pseudo-first-order kinetic model and pseudo-second-order kinetic model to perform nonlinear fitting analysis on the experimental data. Kinetic fitting results ( Figure 11 ) shows that the correlation coefficient of the pseudo-first-order kinetic model (R 2 ) was 0.9865, while the R 2 The value reached 0.9987, closer to the theoretical value of 1, indicating that the pseudo-second-order kinetic model is more suitable for describing the adsorption process of TB-POP. Based on kinetic model theory, the pseudo-first-order kinetic model is primarily applicable to processes dominated by physical adsorption, while the pseudo-second-order kinetic model is more suitable for processes dominated by chemical adsorption. Based on these results, the pseudo-second-order kinetic model is more suitable for describing the adsorption behavior of TB-POP on Au(III). Therefore, chemical adsorption plays a dominant role in this adsorption process.

[0070] Adsorption isotherm of TB-POP

[0071] To investigate the effects of initial Au(III) concentration and external light environment on the adsorption performance of TB-POP, this study conducted adsorption isotherm experiments in a dark environment and under 40W LED light. With the increase of initial Au(III) concentration, the adsorption amount of Au(III) by TB-POP gradually increased and reached the maximum experimental adsorption capacity of 772 mg·g at the adsorption saturation stage. –1 (protect from light) and 1776 mg g –1 (light), respectively Figure 12 (a) and (b) show that experimental data show that light can significantly improve the adsorption performance of the material.

[0072] Then, the Langmuir and Freundlich adsorption isotherm models were used to fit the experimental data. The fitting results showed that under two different illumination conditions, the R 2 The theoretical maximum adsorption capacities calculated by the Langmuir model are 786 mg·g -1 and 1924 mg·g -1 , which is consistent with the maximum adsorption capacity (772 mg·g -1 and 1776 mg·g -1 ), demonstrating good model applicability. These results confirm that the adsorption process of Au(III) by TB-POP is more consistent with the Langmuir model, i.e., monolayer adsorption. Notably, the theoretical maximum adsorption capacity of TB-POP under illumination is 2.45 times that under dark conditions, confirming the enhanced effect of illumination on the adsorption of Au(III) by TB-POP.

[0073] Adsorption selectivity of TB-POP for Au(III)

[0074] In view of the fact that the actual electronic waste leachate usually contains a variety of metal ions. For example: Al (III), Co (ⅠⅠ), Cu (ⅠⅠ), Ni (ⅠⅠ), Mn (ⅠⅠ) and Cr (VI), etc., they will interfere with the adsorption of Au (III) by competing for the adsorption sites of the adsorbent, thereby reducing the adsorption efficiency of the adsorbent for Au (III). Therefore, the development of an adsorbent that can efficiently and selectively enrich Au (III) in a multi-metal cation system has valuable practical application value for improving the purity and efficiency of gold recovery. In this study, in order to evaluate the selective adsorption performance of TB-POP in a complex multi-ion environment, a simulated electronic waste leachate containing the above-mentioned multiple metal ions was prepared, in which the concentration of interfering ions was 100 ppm, which is 10 times that of Au (III), in order to simulate the high interfering ion concentration environment that may be encountered in actual applications. The experimental results are as follows Figure 13 As shown, TB-POP achieved a recovery efficiency of 99.07% for Au(III), compared to only 2.13%-14.16% for other interfering ions. This result demonstrates that TB-POP can still exhibit excellent selective adsorption of Au(III) even in a complex environment with high concentrations of interfering ions, indicating that TB-POP has promising application prospects for gold recovery from electronic waste leachate.

[0075] TB-POP recycling test

[0076] In this study, the recyclability of TB-POP was evaluated by adsorption-desorption cycle experiments. First, 2 mg of TB-POP was immersed in 10 ml of 100 mg·L –1 The Au(III) solution was stirred and adsorbed. After each adsorption, the material was desorbed and regenerated using a thiourea-hydrochloric acid mixed solution, and then the regenerated material was put into the next round of adsorption experiment. The cycle performance test results are shown in Figure 2. Figure 14 As shown in the figure, the recovery efficiency of TB-POP for Au(III) remained above 95% during the five cycles, indicating that the material has good cycle stability and regeneration ability. FT-IR was further used to compare and analyze the samples before and after the cycles to explore the stability of the material's chemical structure. Figure 15 As shown, the infrared spectrum of the TB-POP sample after five adsorption-desorption cycles closely matches that of the original material, with no significant changes in the peak positions and intensities of the characteristic functional groups. This indicates that the material maintains its chemical structural stability after multiple cycles. These results confirm the excellent reusability of the TB-POP material based on C=C covalent linkages, laying a solid foundation for its practical application in gold recovery.

[0077] Adsorption mechanism of TB-POP

[0078] This study revealed the adsorption mechanism of TB-POP on Au(III) through a variety of characterization methods. First, by comparing the X-ray photoelectron spectroscopy (XPS) spectra before and after TB-POP adsorbed Au(III) ( Figure 16 ) found that the sample (TB-POP-Au) after adsorption showed a characteristic double peak of Au 4f in the binding energy range of 82-91eV, confirming that the material successfully captured Au species. The Au 4f spectrum showed two groups of characteristic peaks after peak separation ( Figure 17 ): located at 85.54eV (Au 4f 7 / 2 ) and 89.24eV(Au 4f 5 / 2 ) corresponds to Au(III), while the peak at 83.87eV (Au 4f 7 / 2 ) and 87.55eV(Au 4f 5 / 2 ) is attributed to Au(0), which indicates that part of Au(III) is reduced to Au(0) during the adsorption process. The powder X-ray diffraction (PXRD) test results are shown in Figure 2. Figure 18 , the typical diffraction peaks of Au(0) can be observed in the spectrum, corresponding to the (111), (200), (220), (311) and (222) crystal planes of Au(0), which once again verifies the occurrence of Au(III) reduction behavior. Transmission electron microscopy (TEM) characterization more intuitively shows the formation of irregular gold nanoparticles on the surface of the material ( Figure 19 ), which once again confirmed the existence of Au(0).

[0079] According to the hard and soft acid-base theory, the sulfur and nitrogen functional groups rich in lone pair electrons on TB-POP can act as soft bases to form chelate coordination with soft acid Au(III). To confirm this process, the XPS spectrum of S2p orbital was analyzed ( Figure 20 (a)) and XPS spectra of N1s orbital ( Figure 20 (b) It was found that the S2p of CSC after adsorption 3 / 2 and S2p 1 / 2 The binding energies shifted from 163.60eV and 164.78eV to 166.26eV and 167.46eV, respectively, while the N1s binding energy increased from 399.33eV to 399.58eV. This chemical shift phenomenon indicates that S and N atoms act as electron donors to coordinate with Au(III) during the adsorption process. In addition, a ions at 168.18eV (S2p 3 / 2 ) and 169.36eV(S2p 1 / 2), corresponding to the formation of S=O groups, confirming that TB-POP underwent redox reaction during the adsorption of Au(III), and the sulfur-containing functional groups were oxidized to S=O groups, corresponding to the reduction process of Au(III) mentioned above.

[0080] Further comparison of the FT-IR spectra of TB-POP before and after adsorption of Au(III) ( Figure 21 ) found that TB-POP-Au at 1430 cm –1 The CSC characteristic peak at 1035cm –1 A new characteristic peak belonging to S=O appears at , indicating that CSC is oxidized to S=O during the adsorption process, which once again confirms the above-mentioned redox mechanism.

[0081] The C=C connection expands the π-conjugated framework of TB-POP, further improving the light utilization efficiency of the material. This result is also confirmed by UV-Vis-NIR DRS. Figure 22 As shown in Figure 2, TB-POP exhibits good light absorption performance in the ultraviolet and visible wavelength range. This study further explored the redox mechanism of TB-POP adsorption of Au(III) through UV-Vis-NIR DRS and CV tests. First, the band gap width of TB-POP was found to be 2.03 eV ( Figure 23 ), combined with the CV test results ( Figure 24 ) calculated that its lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) are -3.503 and -5.533 eV respectively. Figure 25 As shown, AuCl4 - The standard reduction potential of Au(0) (E0 = 1.002 V vs NHE) is exactly between the HOMO and LUMO of TB-POP. This energy level matching relationship enables the electrons generated by the excitation of TB-POP to be effectively transferred to Au(III), providing the driving force for its reduction.

[0082] Based on the experimental characterization and theoretical analysis, the adsorption mechanism of TB-POP on Au(III) can be summarized as the following synergistic process: (1) In acidic medium, protonated TB-POP captures AuCl4 by electrostatic attraction. – Anions; (2) The electron-rich S and N functional groups on the material surface undergo chelation and coordination with Au(III), achieving selective adsorption of gold ions; (3) TB-POP reduces some Au(III) to Au(0) through redox reactions, which aggregate to form gold nanoparticles. This multi-mechanism synergistic effect significantly improves the material's adsorption capacity and selectivity for gold ions.

[0083] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A porous organic polymer, characterized in that Its structural chemical formula is:

2. The method for preparing a porous organic polymer according to claim 1, characterized in that: The method comprises the following steps: dissolving 1,3,5-tris(4-cyanomethyl)benzene and 2,5-bis(methylthio)terephthalaldehyde in a first solvent in a certain proportion, adding an alkaline catalyst to the mixture, and mixing the mixture evenly; and reacting the mixture at 100-140° C. for 60-90 hours. After the reaction is completed, TB-POP is obtained.

3. The method for preparing a porous organic polymer according to claim 2, wherein: The first solvent is selected from one or a mixed solvent of two of 1,4-dioxane, mesitylene, cumene, and diglyme.

4. The method for preparing a porous organic polymer according to claim 3, wherein: The first solvent is a mixed solvent of 1,4-dioxane and mesitylene.

5. The method for preparing a porous organic polymer according to claim 2, wherein: The alkaline catalyst is selected from any one of sodium hydroxide and potassium hydroxide, and the concentration of the sodium hydroxide or potassium hydroxide solution is 2-5 mol·L -1 .

6. The method for preparing a porous organic polymer according to claim 2, wherein: The molar ratio of 1,3,5-tris(4-cyanomethylbenzene)benzene to 2,5-bis(methylthio)terephthalaldehyde is 1:1-3.

7. The method for preparing a porous organic polymer according to claim 2, wherein: The mixing process of the 1,3,5-tris(4-cyanomethylbenzene)benzene, the 2,5-bis(methylthio)terephthalaldehyde and the catalyst is carried out by using ultrasound to assist dissolution.

8. The method for preparing a porous organic polymer according to claim 2, wherein: After the reaction is completed, the reaction product is washed, extracted with a solvent, and dried to obtain TB-POP.

9. The method for preparing a porous organic polymer according to claim 8, characterized in that: The washing operation is to wash with N,N-dimethylformamide, acetone and tetrahydrofuran respectively after the reaction is completed; the extraction solvent in the solvent extraction process is THF.

10. Use of the porous organic polymer according to claim 1 or the porous organic polymer prepared by the method according to any one of claims 2 to 9 in the adsorption and separation of gold.

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