Zr-based MOF boron adsorbent as well as preparation method and application thereof

Abstract

The invention discloses a Zr-based MOF boron adsorbent as well as a preparation method and application thereof. The prepared Zr-DHTP and Zr-BTEC materials have excellent saturated adsorption capacity, and compared with commercial boron adsorption resin IRA-743, the adsorption capacity of the Zr-DHTP and Zr-BTEC materials is improved by 5.6 times and 8.7 times respectively. In a complex system in which common ions (such as Na, K, Ca2, Mg2 and the like) coexist, the material not only maintains high adsorption capacity, but also shows a synergistic promotion effect, and shows good selective adsorption performance. In addition, the adsorbent shows efficient boron absorption capacity in a real brine system, the adsorption process is stable, and the adsorbent has excellent cyclic regeneration performance. In conclusion, the zirconium-based metal organic framework Zr-MOF boron adsorbent has outstanding performance in the aspects of selective separation and enrichment of boron, can be widely applied to the fields of salt lake brine boron extraction, electro-catalysis, photocatalysis, photoelectrochemical cells, electrode materials, supercapacitors and the like, and has remarkable scientific research value and industrial application prospect.

Description

Technical Field

[0001] This invention relates to the fields of materials and fine chemical technology, specifically to a Zr-based MOF boron adsorbent, its preparation method, and its application. Background Technology

[0002] According to the annual mineral report released by the China Nonmetallic Minerals Industry Association and the U.S. Geological Survey, as of 2024, my country had become one of the world's largest consumers of boron, with an annual total consumption of approximately 140,000-180,000 tons of boron. Meanwhile, China's import dependence on boron resources was as high as 50%, and boron demand was projected to exceed 200,000 tons by 2025. my country's boron resources in salt lakes exist in the form of dissolved boric acid (B2O3), accounting for approximately 30%-40% of the country's total reserves, or about 6-12 million tons. Major boron-producing salt lakes in China include the Qarhan Salt Lake and Keke Salt Lake in Qinghai Province, and the Zabuye Salt Lake in Tibet Province, with the Qarhan Salt Lake alone having boron reserves of approximately 2-3 million tons. China's annual production capacity of 99.5% pure boric acid from salt lakes is approximately 30,000-40,000 tons. Currently, the industrial extraction rate of boric acid from salt lakes in my country is less than 30%, far below the international advanced level. For example, the boric acid extraction rate from Lake Sears in the United States exceeds 90%. In 2024, my country's actual output of boric acid from salt lakes was approximately 25,000 tons, accounting for 15%-20% of the country's total boric acid production. Furthermore, the production cost of boric acid from salt lakes is approximately 4,000-5,000 yuan / ton, significantly lower than that of the traditional ore-based method, which costs over 6,000 yuan / ton. If the purity of boric acid from salt lakes were increased to electronic grade purity of 99.99%, its price could reach 60,000-80,000 yuan / ton.

[0003] In the old brine of the Qarhan Salt Lake, sodium chloride, carnallite, and magnesium chloride hexahydrate form a tri-salt co-saturated system, with boron concentrations reaching 1000-5000 mg / L. However, this system contains lithium-boron-magnesium symbiotic minerals, such as Li₂B₄O₇·3H₂O, and due to pH ≤ 7.0 and variations in ionic strength, the speciation of boron exhibits complex dynamic changes, mainly including B(OH)₃, B(OH)₄⁻, B₃O₃(OH)₄⁻, and B₄O₅(OH)₄. 2 ⁻. Compared to the Dead Sea brine, the boron concentration in the Chaka Salt Lake brine is about 5 times that of the Dead Sea, but its Mg content is lower. 2 The ⁺ / B molar ratio is typically greater than 100:1, while in the Dead Sea it is less than 10:1. Based on these characteristics, the development of boron resources in the old brine of the Qarhan Salt Lake faces the following technical bottlenecks: (1) Solvent extraction method: The commonly used extractant is 2-ethyl-1,3-hexanediol, but in Mg 2 ⁺ Under certain conditions, severe emulsification can easily occur, resulting in an organic phase loss of more than 20%; (2) Adsorption method: Conventional amino resins (such as Amberlite IRA-743) have an adsorption capacity of less than 20 mg / g for boron, and are affected by Mg.2 ⁺Competitive adsorption effect, adsorbent regeneration difficulty is greater; In view of the problems of the prior art, researchers mainly carried out research on the improvement of adsorption performance and mechanism of polyol and MOF adsorbents. However, the construction of boron adsorbents with high selectivity and high adsorption capacity is still a research hotspot in the field. In view of the above problems, a new type of Zr-MOF boron adsorbent is designed and developed, which shows excellent boron adsorption performance and selectivity, and on this basis, the adsorption conditions are studied in detail, which lays a foundation for industrial production. SUMMARY

[0004] Based on the above technical problems, the Zr-MOF boron adsorbent is prepared by one-step simple hydrothermal reaction, and the metal Zr salt and the organic ligand are reacted in a closed hydrothermal kettle under certain conditions. The purpose of the application is to provide a Zr-MOF boron adsorbent and a preparation method and application thereof.

[0005] The application protects a preparation method of a Zr-MOF boron adsorbent, which adopts a metal Zr salt and an organic ligand in a closed hydrothermal kettle, and a Zr-MOF boron adsorbent can be obtained by one-step hydrothermal reaction under certain reaction conditions; the reaction conditions are: temperature 100-130 DEG C, reaction time more than 15 hours; and the organic ligand is 2,5-dihydroxyterephthalic acid or pyromellitic acid.

[0006] The application protects a preparation method of a Zr-MOF boron adsorbent, which specifically includes the following steps: Step 1, a certain amount of metal Zr salt and organic ligand are weighed and dissolved in N,N-dimethylformamide (DMF), then formic acid and concentrated hydrochloric acid are added for adjustment, and ultrasonic dispersion is carried out at room temperature for 10-20 minutes until complete dissolution; Step 2, the above mixture is transferred to a hydrothermal kettle with a polytetrafluoroethylene lining, sealed and reacted at 100-130 DEG C for 15-24 hours; Step 3, after the reaction is completed, the kettle is opened, the obtained product is washed with DMF and ultrapure water for 3 times respectively, and then vacuum drying and activation are carried out at 100 DEG C overnight.

[0007] Further, the addition ratio of the metal Zr salt and the organic ligand is metal Zr salt: organic ligand = 0.5-0.69: 0.27-0.42; and the addition ratio of N,N-dimethylformamide (DMF), formic acid and concentrated hydrochloric acid is N,N-dimethylformamide (DMF): formic acid: concentrated hydrochloric acid = 60: 10: 1.

[0008] Furthermore, the metal Zr salt is any one of zirconium chloride (ZrCl4), zirconium dichloride (ZrOCl2), zirconium oxynitrate (ZrO(NO3)2), and zirconium oxychloride octahydrate (ZrOCl2·8H2O).

[0009] This invention also protects the Zr-based MOF boron adsorbent prepared by the above method, wherein the Zr-based MOF boron adsorbent is Zr-DHTP or Zr-BTEC.

[0010] Furthermore, the Zr-DHTP and Zr-BTEC boron adsorbents are: Zr-DHTP-1, Zr-DHTP-2, Zr-DHTP-3, Zr-BTEC-1, Zr-BTEC-2, and Zr-BTEC-3.

[0011] This invention also protects the application of the above-mentioned Zr-based MOF boron adsorbent, which is used in the fields of brine boron adsorption, electrocatalysis, photocatalysis, photoelectrochemical cells, electrode materials, and supercapacitor research.

[0012] Compared with existing technologies, the present invention has the following beneficial effects: The Zr-DHTP and Zr-BTEC materials prepared in this invention exhibit excellent saturated adsorption capacities, representing increases of 5.6 times and 8.7 times, respectively, compared to the commercial boron adsorption resin IRA-743. They also demonstrate superior adsorption capacity in the presence of common coexisting ions (such as Na⁺, K⁺, Ca²⁺, and Ca²⁺). 2 ⁺、Mg 2 In complex systems (such as those containing zirconium, etc.), this type of material not only maintains high adsorption capacity but also exhibits a synergistic promoting effect, demonstrating excellent selective adsorption performance. Furthermore, this adsorbent exhibits highly efficient boron adsorption capacity in real brine systems, with a stable adsorption process and excellent regeneration performance. In summary, this zirconium-based metal-organic framework (Zr-MOF) boron adsorbent demonstrates outstanding performance in the selective separation and enrichment of boron, and can be widely applied in fields such as boron extraction from salt lake brine, electrocatalysis, photocatalysis, photoelectrochemical cells, electrode materials, and supercapacitors, possessing significant scientific research value and promising industrial application prospects.

[0013] The adsorption conditions of the Zr-based MOF boron adsorbent prepared in this invention were also investigated; the effects of different initial boron concentrations and temperatures on the boron adsorption capacity of Zr-DHTP and Zr-BTEC were studied; and the boron adsorption capacity and regeneration capacity in real brine were demonstrated as follows: 1. Adsorption conditions The optimal pH is 10. In an initial boron solution concentration of 0.08 M, boron mainly exists as B(OH)3, B(OH)4⁻, B3O3(OH)4⁻, and B3O3(OH)5⁻. 2It exists in the forms of B⁻ and B4O5(OH)4⁻, and reaches saturation adsorption capacity after 8 hours.

[0014] 2. Adsorption capacity at different initial boron concentrations and temperatures The boron adsorption capacity increased with increasing initial boron concentration, specifically for B3O3(OH)4⁻ and B3O3(OH)5⁻. 2 The total proportion of these three substances, B4O5(OH)4, is also increasing. Therefore, before the adsorbent reaches its saturation adsorption capacity, the adsorption capacity of Zr-DHTP and Zr-BTEC for boron will continue to increase and the rate of increase will gradually increase.

[0015] 3. Boron adsorption capacity in real brine It exhibits good selectivity for boron, and its adsorption performance further increases in simulated brine due to the salt effect. The presence of other strong electrolytes promotes the dissociation of boric acid. The test solution system contains B3O3(OH)4⁻ and B3O3(OH)5⁻. 2 The concentrations of these three boron compounds, B⁻ and B�O₅(OH)⁻, are further increased, thereby promoting boron adsorption.

[0016] 4. Regeneration ability In four cyclic experimental periods, the adsorption capacities of Zr-DHTP and Zr-BTEC decreased by 23.37% and 22.76%, respectively, indicating that the adsorption performance of MOF boron adsorbents remained stable and had good cyclic regeneration performance. Attached Figure Description

[0017] Figure 1 The nitrogen adsorption-desorption isotherms and pore size distribution diagrams of the boron adsorbent Zr-DHTP-1 of this invention are shown below. Figure 2 The nitrogen adsorption-desorption isotherm and pore size distribution diagram of the boron adsorbent Zr-BTEC-1 of this invention are shown below. Figure 3 The microstructure of the boron adsorbent Zr-DHTP-2 of this invention (it has a rod-like structure). Figure 4 The microstructure of the boron adsorbent Zr-BTEC-2 of this invention (it exhibits a spherical morphology). Figure 5 This shows the change in adsorption capacity of the boron adsorbent Zr-DHTP-3 at different pH values. Figure 6 This shows the change in adsorption capacity of the boron adsorbent Zr-BTEC-3 at different pH values. Figure 7 This shows the trend of the adsorption capacity of the boron adsorbent Zr-DHTP-3 of the present invention changing over time. Figure 8The trend of the adsorption capacity of the boron adsorbent Zr-BTEC-3 of the present invention changing over time; Figure 9 The adsorption thermodynamic model spectrum of boron compounds by the boron adsorbent Zr-DHTP-3 of this invention is shown. Figure 10 The adsorption thermodynamic model spectrum of boron compounds by the boron adsorbent Zr-BTEC-3 of this invention is shown. Figure 11 This is a diagram showing the ion competition of the boron adsorbent Zr-DHTP in brine according to the present invention. Figure 12 This is a diagram showing the ion competition of the boron adsorbent Zr-BTEC in brine according to the present invention. Figure 13 This is a cyclic stability diagram of the boron adsorbents Zr-DHTP and Zr-BTEC of the present invention.

[0018] Appendix Figure 9 In the image, (a) adsorption isotherm of boron on Zr-DHTP-3; (b) Henry model; (c) Freundlich model; (d) Langmuir model; Appendix Figure 10 In the figures, (a) adsorption isotherm of boron on Zr-BTEC-3; (b) Henry model; (c) Freundlich model; (d) Langmuir model. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] The specific methods used in the specific embodiments of the present invention are as follows: A method for preparing a Zr-based MOF boron adsorbent specifically includes the following steps: Step 1: Weigh 0.5-0.69g of a metallic Zr salt (any one of zirconium chloride (ZrCl4), zirconium oxychloride (ZrOCl2), zirconium oxynitrate (ZrO(NO3)2), zirconium oxychloride octahydrate (ZrOCl2·8H2O)) and 0.27-0.42g of an organic ligand (2,5-dihydroxyterephthalic acid or pyromellitic acid), add 60mL of N,N-dimethylformamide (DMF) to dissolve, then add 10mL of formic acid and 1mL of concentrated hydrochloric acid to adjust the solution, and sonicate at room temperature for 10-20 minutes until completely dissolved; Step 2: Transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react it at 100-130°C for 15-24 hours. Step 3: After the reaction is complete, allow the mixture to cool naturally to room temperature, open the vessel, and wash the obtained product three times each with DMF and ultrapure water, then vacuum dry and activate it overnight at 100°C. Step 4: The microstructure and adsorption performance of the boron adsorbent material prepared above were preliminarily characterized and evaluated.

[0021] Example 1 A method for preparing a Zr-based MOF boron adsorbent (Zr-DHTP-1) Weigh 0.5 g of zirconium chloride and 0.42 g of 2,5-dihydroxyterephthalic acid, dissolve them in 60 mL of N,N-dimethylformamide (DMF), then add 10 mL of formic acid and 1 mL of concentrated hydrochloric acid for adjustment, and sonicate at room temperature for 10-20 minutes until completely dissolved; transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react at 130 °C for 24 hours; after the reaction is completed, allow it to cool naturally to room temperature, open the reactor, and wash the obtained product three times each with DMF and ultrapure water, then vacuum dry and activate it overnight at 100 °C to obtain Zr-MOF boron adsorbent, designated Zr-DHTP-1.

[0022] Example 2 A method for preparing a Zr-based MOF boron adsorbent (Zr-DHTP-2) Weigh 0.69 g of zirconium oxychloride octahydrate and 0.42 g of 2,5-dihydroxyterephthalic acid, dissolve them in 60 mL of N,N-dimethylformamide (DMF), then add 10 mL of formic acid and 1 mL of concentrated hydrochloric acid for adjustment, and sonicate at room temperature for 10-20 minutes until completely dissolved; transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react at 130 °C for 24 hours; after the reaction is completed, allow it to cool naturally to room temperature, open the reactor, and wash the obtained product three times each with DMF and ultrapure water, then vacuum dry and activate it overnight at 100 °C to obtain the Zr-MOF boron adsorbent, designated Zr-DHTP-2.

[0023] Example 3 A method for preparing a Zr-based MOF boron adsorbent (Zr-DHTP-3) Weigh 0.5 g of zirconium oxynitrate and 0.42 g of 2,5-dihydroxyterephthalic acid, dissolve them in 60 mL of N,N-dimethylformamide (DMF), then add 10 mL of formic acid and 1 mL of concentrated hydrochloric acid for adjustment, and sonicate at room temperature for 10-20 minutes until completely dissolved; transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react at 130 °C for 24 hours; after the reaction is completed, allow it to cool naturally to room temperature, open the reactor, and wash the obtained product three times each with DMF and ultrapure water, then vacuum dry and activate it overnight at 100 °C to obtain the Zr-MOF boron adsorbent, designated Zr-DHTP-3.

[0024] Example 4 A method for preparing a Zr-based MOF boron adsorbent (Zr-BTEC-1) Weigh 0.5 g of zirconium chloride and 0.27 g of pyromellitic acid, dissolve them in 60 mL of N,N-dimethylformamide (DMF), then add 10 mL of formic acid and 1 mL of concentrated hydrochloric acid for adjustment, and sonicate at room temperature for 10-20 minutes until completely dissolved; transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react at 130 °C for 24 hours; after the reaction is completed, allow it to cool naturally to room temperature, open the reactor, and wash the obtained product three times each with DMF and ultrapure water, then vacuum dry and activate it overnight at 100 °C to obtain the Zr-MOF boron adsorbent, designated Zr-BTEC-1.

[0025] Example 5 A method for preparing a Zr-based MOF boron adsorbent (Zr-BTEC-2) Weigh 0.69 g of zirconium oxychloride octahydrate and 0.27 g of pyromellitic acid, dissolve them in 60 mL of N,N-dimethylformamide (DMF), then add 10 mL of formic acid and 1 mL of concentrated hydrochloric acid for adjustment, and sonicate at room temperature for 10-20 minutes until completely dissolved; transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react at 130 °C for 24 hours; after the reaction is completed, allow it to cool naturally to room temperature, open the reactor, and wash the obtained product three times each with DMF and ultrapure water, then vacuum dry and activate it overnight at 100 °C to obtain the Zr-MOF boron adsorbent, designated Zr-BTEC-2.

[0026] Example 6 A method for preparing a Zr-based MOF boron adsorbent (Zr-BTEC-3) Weigh 0.5 g of zirconium oxynitrate and 0.27 g of pyromellitic acid, dissolve them in 60 mL of N,N-dimethylformamide (DMF), then add 10 mL of formic acid and 1 mL of concentrated hydrochloric acid for adjustment, and sonicate at room temperature for 10-20 minutes until completely dissolved; transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react at 130 °C for 24 hours; after the reaction is completed, allow it to cool naturally to room temperature, open the reactor, and wash the obtained product three times each with DMF and ultrapure water, then vacuum dry and activate it overnight at 100 °C to obtain the Zr-MOF boron adsorbent, designated Zr-BTEC-3.

[0027] Example 7 Investigating the specific surface area and pore size of Zr-based MOF boron adsorbents As an adsorbent, the porosity of the adsorbent directly affects the number of active sites and steric hindrance, thus influencing adsorption performance. To investigate the specific surface area and pore size of the Zr-based MOF boron adsorbent, nitrogen adsorption-desorption isotherms were used for testing. (See attached...) Figures 1-2 As shown, both Zr-DHTP-1 and Zr-BTEC-1 adsorbents exhibit type I adsorption curves. Based on the DFT method, their specific surface areas are 63.66 and 95.13 m², respectively. 2 / g, as can be seen from the pore size analysis diagram, Zr-DHTP-1 has micropores at 0.7 and 1.2 nm (see appendix for details). Figure 1 Zr-BTEC-1 has micropores at 0.8 and 1.2 nm (see appendix for details). Figure 2 ).

[0028] Example 8 Investigating the microstructure of the prepared Zr-based MOF boron adsorbent To investigate the microstructure of the prepared Zr-based MOF boron adsorbent, Zr-DHTP-2 and Zr-BTEC-2 samples were randomly selected for scanning electron microscopy (SEM) characterization. (See attached image.) Figure 3 As shown, Zr-DHTP-2 has a rod-like structure, approximately 5 μm in length and 1 μm in diameter; it is composed of attached... Figure 4 It is evident that Zr-BTEC-2 exhibits a spherical morphology with a particle size distribution ranging from 2 to 3 μm. In summary, the prepared materials all have particle sizes greater than 2 μm, falling into the category of relatively large particles. During the separation process, a 2 μm pore size filter membrane is used for solid-liquid separation. After adsorption, the material can be easily recovered from the solution via centrifugation, resulting in minimal material loss. This characteristic provides favorable conditions for its efficient solid-liquid separation in industrial production.

[0029] Example 9 The adsorption conditions for the Zr-based MOF boron adsorbent prepared by the study To further investigate the adsorption conditions of the prepared boron adsorbents, Zr-DHTP-3 and Zr-BTEC-3 boron adsorbents were selected. The effects of solution pH and adsorption time on the saturated adsorption capacity were examined using the controlled variable method. The results are attached. Figure 5 and attached Figure 6 As shown, it is clear that within the pH range of 3-8, their adsorption capacity for boron compounds does not change significantly, and the adsorption amount is relatively low. When the pH exceeds 8, the adsorption amount increases rapidly with increasing solution pH. Finally, the adsorption capacity reaches its maximum at pH 10, and within the pH range of 10 to 12, the adsorption capacity gradually decreases with increasing solution pH. Therefore, the optimal pH value for Zr-DHTP-3 and Zr-BTEC-3 boron adsorbents is 10. When the solution pH is 10, the initial boron solution concentration reaches 0.08M, and boron mainly exists as B(OH)3, B(OH)4⁻, B3O3(OH)4⁻, and B3O3(OH)5⁻. 2 The boron exists in the forms of B3O3(OH)4⁻ and B4O5(OH)4⁻. However, the Zr-based MOF boron adsorbent exhibits poor adsorption capacity in low-pH boron solutions. Furthermore, the variation in the form of boron with pH in a 0.08M boron concentration solution indicates that the Zr-based MOF boron adsorbent primarily adsorbs B3O3(OH)4⁻ and B3O3(OH)5⁻. 2 These are three types of boron compounds: B⁻, B₄O₅(OH)⁻, and B₄O₅(OH)⁻.

[0030] The trend of the adsorption capacity of Zr-DHTP-3 adsorbent over time when the initial boron concentration is 0.08 mol / L is shown in the attached figure. Figure 7 and attached Figure 8 As shown, the adsorption rate increases rapidly in the first hour. As the adsorption time increases from 1 hour to 8 hours, the adsorption amount increases slowly. The adsorption reaches equilibrium at 8 hours, and the adsorption amount hardly changes with the increase of time. The trend of Zr-BTEC-3 adsorption amount with adsorption time is similar to that of Zr-DHTP-3. The adsorption amount increases rapidly in the first 2 hours, and the adsorption amount increases slowly from 2 to 8 hours, reaching saturation adsorption amount at 8 hours.

[0031] Example 10 This study investigated the effects of different initial boron concentrations and temperatures on the adsorption capacity of Zr-DHTP and Zr-BTEC on boron. To further investigate the effects of concentration and temperature on adsorption, the adsorption capacity of Zr-DHTP-3 and Zr-BTEC-3 for boron was studied at different initial boron concentrations (0.008, 0.016, 0.032, 0.048, 0.064, and 0.080 mol / L) and different temperatures (25℃, 35℃, and 45℃). (See attached...) Figure 9 and 10The adsorption thermodynamic model spectra of boron compounds by Zr-DHTP and Zr-BTEC can be obtained sequentially. Their boron adsorption capacity increases with increasing initial boron concentration. (B3O3(OH)4⁻, B3O3(OH)5⁻) 2 The total proportion of these three substances (⁻, B4O5(OH)4⁻) is also increasing. Therefore, before reaching the adsorbent saturation adsorption capacity, the adsorption capacity of Zr-DHTP and Zr-BTEC for boron will continue to increase, and the rate of increase will gradually increase. The good fit of the Henry model indicates that Zr-DHTP and Zr-BTEC are ideal adsorption models for boron adsorption. The Langmuir model cannot fit the adsorption results well, while the Freundlich model can fit them well, indicating that the adsorption of boron on Zr-DHTP and Zr-BTEC is non-ideal, non-uniform surface adsorption, and multilayer adsorption. The thermodynamic fitting data are detailed in Table 1.

[0032] Table 1. Adsorption isotherm model parameters for boron by Zr-DHTP and Zr-BTEC adsorbents Example 11 The boron adsorbent prepared in the study was tested for its boron adsorption capacity in real brine. To simulate the boron adsorption capacity of the prepared Zr-DHTP and Zr-BTEC materials in real brine, the ion competition of the adsorbents was tested. In a boron solution with an initial boron concentration of 0.08 M and a pH of 10, interfering ions of 0.2 M were present. Compared to pure boron solution, the boron adsorption capacity of both Zr-DHTP and Zr-BTEC prepared in the solution containing interfering ions was improved. The coexisting ion (Na₂O₃) was tested. + Li + K + Cl - SO4 2- The almost unchanged performance indicates that the prepared Zr-DHTP and Zr-BTEC materials have good selectivity for boron, and their adsorption performance in simulated brine will further increase. This is due to the salt effect, which promotes the dissociation of boric acid in the presence of other strong electrolytes. The test solution showed almost no change in the concentrations of B3O3(OH)4⁻ and B3O3(OH)5⁻. 2 The concentrations of these three boron compounds, B⁻ and B₄O₅(OH)⁻, are further increased, thereby promoting boron adsorption (see appendix for details). Figure 11 and 12 ).

[0033] Example 12 This study investigates the cycling stability (regeneration capacity) of the Zr-based MOF boron adsorbent prepared in this application. Regeneration capacity is a key parameter for evaluating the practical potential of adsorbents in real-world applications. Specifically, after the adsorption process, the Zr-based MOF boron adsorbent was obtained by centrifugation and then washed sequentially: first, it was washed three times with 20 mL of hydrochloric acid aqueous solution with a pH of 3-4; then, it was washed three times with 20 mL of hydrochloric acid aqueous solution with a pH of 5-6; finally, it was washed with 20 mL of deionized water until the supernatant was neutral. The desorption process was performed using a constant-temperature water bath shaker at 25°C for 20 min per desorption cycle. Subsequently, the adsorbent powder was centrifuged and freeze-dried for reuse in the next adsorption cycle. (See attached image) Figure 13 As shown, the adsorption capacities of Zr-DHTP and Zr-BTEC decreased by 23.37% and 22.76%, respectively, during the four cyclic experimental periods. This indicates that the adsorption performance of the MOF boron adsorbent remains stable and exhibits good cyclic regeneration performance.

[0034] Comparative Example This paper compares the adsorption capacity of the Zr-based MOF boron adsorbent prepared in this application with that of commercially available adsorption resin (IRA-743) and adsorbents from literature sources. Detailed single-factor experiments on boron adsorption were conducted, providing relatively detailed adsorption conditions, especially ion competition experiments. The results show that the saturated adsorption capacities of Zr-DHTP and Zr-BTEC prepared in this application are 5.6 times and 8.7 times higher, respectively (see Table 2). The Zr-based MOF boron adsorbent prepared in this application not only did not decrease its adsorption capacity in the presence of other common ions, but also exhibited a promoting effect, thus demonstrating high selective adsorption and practical application potential. Therefore, this invention has significant scientific and practical application value.

[0035] Table 2. Comparison of adsorption performance of Zr-DHTP and Zr-BTEC with existing adsorbents. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Zr-based MOF boron adsorbent, characterized in that, Zr-based MOF boron adsorbents can be obtained by reacting metal Zr salts with organic ligands in a closed hydrothermal reactor under certain reaction conditions through a one-step hydrothermal reaction. The reaction conditions are: temperature 100-130℃, reaction time ≥15 hours. The organic ligands are 2,5-dihydroxyterephthalic acid or pyromellitic acid.

2. The method for preparing a Zr-based MOF boron adsorbent according to claim 1, characterized in that, The preparation method specifically includes the following steps: Step 1: Weigh a certain amount of metal Zr salt and organic ligand, dissolve them in N,N-dimethylformamide (DMF), then add formic acid and concentrated hydrochloric acid to adjust the concentration, and ultrasonically disperse at room temperature for 10-20 minutes until completely dissolved; Step 2: Transfer the above mixture to a hydrothermal reactor with a polytetrafluoroethylene liner, seal it, and react it at 100-130°C for 15-24 hours. Step 3: After the reaction is complete, allow the mixture to cool naturally to room temperature, open the vessel, and wash the obtained product three times each with DMF and ultrapure water. Then, vacuum dry and activate the product overnight at 100°C.

3. The method for preparing a Zr-based MOF boron adsorbent according to claim 2, characterized in that, The addition ratio of the metal Zr salt and the organic ligand is metal Zr salt: organic ligand = 0.5-0.69: 0.27-0.42; the addition ratio of N,N-dimethylformamide DMF, formic acid, and concentrated hydrochloric acid is N,N-dimethylformamide DMF: formic acid: concentrated hydrochloric acid = 60:10:

1.

4. The method for preparing a Zr-based MOF boron adsorbent according to claim 2, characterized in that, The metal Zr salt is any one of zirconium chloride ZrCl4, zirconium dichloride ZrOCl2, zirconium oxynitrate ZrO(NO3)2, and zirconium oxychloride octahydrate ZrOCl2·8H2O.

5. A Zr-based MOF boron adsorbent, characterized in that, The adsorbent is a Zr-based MOF boron adsorbent prepared by the method according to any one of claims 1-4, wherein the Zr-based MOF boron adsorbent is Zr-DHTP or Zr-BTEC.

6. The Zr-based MOF boron adsorbent according to claim 5, characterized in that, The Zr-DHTP and Zr-BTEC boron adsorbents are: Zr-DHTP-1, Zr-DHTP-2, Zr-DHTP-3, Zr-BTEC-1, Zr-BTEC-2, and Zr-BTEC-3.

7. The application of the Zr-based MOF boron adsorbent according to claim 6, characterized in that, The Zr-based MOF boron adsorbent is applied in the research fields of brine boron adsorption, electrocatalysis, photocatalysis, photoelectrochemical cells, electrode materials, and supercapacitors.

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