Two-dimensional L-FMPBA-MOF, hybrid matrix membrane and Rb in adsorbed water + and Cs + Applications in this area

Abstract

This invention belongs to the field of adsorption material technology, and provides a two-dimensional L-FMPBA-MOF, a mixed matrix membrane, and Rb adsorption in water. + and Cs + Applications in this area. The two-dimensional L-FMPBA-MOF is a metal-organic framework material with a two-dimensional sheet-like structure, and the metal ion in the metal-organic framework material is Fe. 3+ and Mn 2+ The two-dimensional L-FMPBA-MOF exhibits Prussian blue analogue diffraction characteristics in its X-ray diffraction pattern. The two-dimensional sheet-like structure of the L-FMPBA-MOF provides an ultra-short transport channel for ion exchange, effectively shortening the ion diffusion path and improving ion transport efficiency. The Fe in the two-dimensional L-FMPBA-MOF... 3+ and Mn 2+ They complement each other in terms of coordination environment and ion exchange mechanism, and their synergistic effect lowers the specific ion migration barrier and significantly improves Rb. + and Cs + The amount of adsorption.

Description

Technical Field

[0001] This invention belongs to the field of adsorption material technology, and relates to a two-dimensional L-FMPBA-MOF (Layered-FeMn-PBA-MOF) and its preparation method, a mixed matrix membrane, and Rb adsorption in water. + and Cs + Applications in this area. Background Technology

[0002] Rubidium (Rb) and cesium (Cs) are important rare alkali metals with unique physicochemical properties, finding wide application in precision timing, specialty glasses, catalysis, energy conversion, and biomedicine. In the new energy sector, rubidium, cesium, and their compounds demonstrate indispensable value: rubidium-cesium atomic clocks are core components for high-precision time synchronization in satellite navigation, 5G / 6G communication networks, and smart grids, directly impacting the stability and scheduling efficiency of renewable energy grid connection; cesium compounds, as highly efficient optoelectronic materials, can improve the photoelectric conversion efficiency and long-term stability of perovskite solar cells; rubidium-cesium alloys are key working fluids for magnetohydrodynamic power generation and ion propulsion, with potential applications in aerospace and advanced energy systems; furthermore, the special functions of rubidium and cesium in novel high-energy-density batteries, nuclear energy, and energy storage systems are increasingly prominent.

[0003] However, rubidium and cesium are extremely rare and highly dispersed in the Earth's crust, making them difficult to recover economically using traditional ore extraction processes. Salt lake brines, especially lithium-rich old brine, are important carriers of rubidium and cesium. However, brine systems contain high concentrations of sodium. + K + Mg 2+ and Ca 2+ Interference from coexisting ions, and Rb + and Cs + Low concentration and similar hydrated ionic radii lead to highly selective separation and extraction of Rb. + and Cs + Facing enormous challenges, therefore, developing efficient Rb for salt lake brine is crucial. + and Cs + Adsorption separation technology is not only crucial for ensuring the security of key raw material supply, but also a core foundational link that directly supports the iteration of new energy technologies, high-end equipment manufacturing, and the upgrading of the next-generation information technology industry.

[0004] Commonly used methods for extracting Rb + and Cs + Methods for treating Rb include precipitation, extraction, and adsorption. Adsorption has become the most popular method due to its advantages such as recyclability, ease of operation, high recovery rate, and simple process. + and Cs + The performance of mainstream separation and enrichment technologies depends primarily on the design of the adsorption materials.

[0005] Existing adsorbent materials face a significant challenge in applications: traditional adsorbent materials are limited by bulk structures or inefficient interface designs, resulting in long ion diffusion paths, low utilization of internal active sites, and high mass transfer resistance, making it difficult to adsorb low concentrations of Rb in complex brine systems. + and Cs + Achieving rapid, high-capacity adsorption. However, powder materials still face challenges in industrial operations, such as difficulties in solid-liquid separation and easy loss of active components. Especially in response to the demand from the new energy industry for large-scale, low-cost, and green extraction of key metal resources, existing Rb... + and Cs + Adsorption technology struggles to simultaneously meet the multiple challenges of high selectivity, rapid kinetics, and reliability for engineering applications.

[0006] Therefore, developing novel adsorbent materials that combine ultra-short transport channels, abundant active sites, and low migration barriers, while also meeting the demands of industrial applications, is crucial for improving the Rb content of salt lake brine. + and Cs + The urgent need for separation efficiency. Summary of the Invention

[0007] To address the limitations of existing adsorbent materials in complex brine systems for adsorbing low concentrations of Rb... + and Cs + To address the problem of rapid, high-capacity adsorption, this invention provides a two-dimensional L-FMPBA-MOF, a hybrid matrix membrane, and an adsorption method for Rb in water. + and Cs + Applications in this area.

[0008] This invention is achieved through the following technical solution:

[0009] In a first aspect, the present invention provides a two-dimensional L-FMPBA-MOF, wherein the two-dimensional L-FMPBA-MOF is a metal-organic framework material having a two-dimensional sheet-like structure, and the metal ion in the metal-organic framework material is Fe. 3+ and Mn 2+ The two-dimensional L-FMPBA-MOF exhibits the diffraction characteristics of a Prussian blue analog in X-ray diffraction patterns.

[0010] Secondly, the present invention provides a method for preparing the aforementioned two-dimensional L-FMPBA-MOF, comprising the following steps:

[0011] S1, polyvinylpyrrolidone is coordinated with soluble manganese salt and soluble iron salt to obtain FMPBA-MOF precursor;

[0012] S2, the FMPBA-MOF precursor is peeled off to obtain the two-dimensional L-FMPBA-MOF.

[0013] Preferably, S1 specifically includes:

[0014] (1) Dissolve polyvinylpyrrolidone in a mixed solution of ethanol and water, then add soluble manganese salt and tert-butanol, and stir until dissolved to form solution A; dissolve soluble iron salt in water to form solution B;

[0015] (2) Add solution A dropwise to solution B and mix to obtain suspension C;

[0016] (3) The suspension C was stirred and reacted, then the solid and liquid were separated, the solid product D was collected and dried to obtain the FMPBA-MOF precursor.

[0017] Preferably, the soluble manganese salt is manganese sulfate monohydrate, and the soluble iron salt is potassium ferricyanide.

[0018] Preferably, the mass ratio of polyvinylpyrrolidone to soluble manganese salt and soluble iron salt is (200~300) mg:(140.5~169.5) mg:(140.5~169.5) mg.

[0019] Preferably, S2 specifically includes: mixing the FMPBA-MOF precursor with hydrochloric acid solution, water and N,N-dimethylformamide, reacting at a constant temperature, separating the solid product and washing and drying it to obtain the two-dimensional L-FMPBA-MOF.

[0020] Furthermore, the reaction under constant temperature specifically refers to the reaction being carried out at 60~100 ℃ for 6~28 h.

[0021] Thirdly, the present invention provides a hybrid matrix membrane, wherein the hybrid matrix membrane uses polyvinylidene fluoride as a matrix and is filled with two-dimensional L-FMPBA-MOF as described above.

[0022] Preferably, the two-dimensional L-FMPBA-MOF accounts for 50% to 80% of the mass of the mixed matrix membrane.

[0023] Fourthly, the present invention provides the two-dimensional L-FMPBA-MOF or the hybrid matrix membrane described above for adsorbing Rb in water. + and / or Cs + Applications in this area.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The two-dimensional L-FMPBA-MOF described in this invention is a metal-organic framework material with a two-dimensional sheet-like structure, which contains Fe 3+ and Mn 2+The bimetallic sites formed, when the two-dimensional L-FMPBA-MOF is applied in mixed matrix membranes (MMMs), the unique two-dimensional sheet-like structure of L-FMPBA-MOF constructs ultra-short transport channels for ion exchange, effectively shortening the ion diffusion path and improving ion transport efficiency. Simultaneously, the Fe in the two-dimensional L-FMPBA-MOF... 3+ and Mn 2+ Complementary in coordination environment and ion exchange mechanism, Fe 3+ The nodes provide a stable framework and charge density center, Mn 3+ The node introduces more active sites, and the synergistic effect of these two factors lowers the specific ion migration barrier, significantly increasing Rb. + and Cs + The amount of adsorption.

[0026] The preparation method of this invention uses polyvinylpyrrolidone (PVP) as a structure directing agent. The amide group (-CON-) on the polyvinylpyrrolidone molecular chain can react with Mn 2+ Fe 3+ Through weak coordination or hydrogen bonding, an organic coating layer is formed during the crystal nucleation stage, which inhibits the disordered aggregation and excessive growth of particles, thereby making the material tend to grow in two dimensions. The resulting FMPBA-MOF precursor has a layered structure, and two-dimensional L-FMPBA-MOF with a two-dimensional sheet structure is obtained by peeling.

[0027] Furthermore, in the preparation method of this invention, the soluble manganese salt is first prepared as solution A and the soluble iron salt is prepared as solution B, and then the two are mixed together. On the one hand, this allows the soluble manganese salt and soluble iron salt to dissolve fully; on the other hand, it allows the structure-directing agent PVP to preferentially react with Mn. 2+ Pre-coordination occurs, forming a stable complex structure, effectively regulating crystal nucleation and growth kinetics, thereby guiding the material to form a layered FMPBA-MOF precursor that is conducive to subsequent exfoliation.

[0028] Furthermore, the present invention uses hydrochloric acid solution to treat the FMPBA-MOF precursor, which can not only achieve the exfoliation of the FMPBA-MOF precursor, but also adjust the surface charge of the two-dimensional L-FMPBA-MOF obtained by exfoliation, which is beneficial for the adsorption of alkali metal ions.

[0029] This invention combines two-dimensional L-FMPBA-MOF with polyvinylidene fluoride (PVDF) to form a compound that can efficiently adsorb Rb. + and Cs + The hybrid matrix membrane obtained by this invention has a higher Rb value.+ and Cs + Adsorption capacity, especially for Rb adsorption in complex brine. + and Cs + It exhibits excellent adsorption performance in Rb. The research results show that the hybrid matrix membrane of this invention exhibits excellent adsorption performance in Rb. + and Cs + The highest adsorption capacities reached 0.68 mg / g and 0.84 mg / g, respectively, achieving industry-leading levels and providing a high-efficiency adsorption capacity for Rb. + and Cs + This provides a new and effective strategy. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is an atomic force microscope image of the two-dimensional L-FMPBA-MOF prepared in Example 3.

[0032] Figure 2 This is the X-ray diffraction (XRD) pattern of the two-dimensional L-FMPBA-MOF prepared in Example 3. Detailed Implementation

[0033] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0035] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0036] This invention provides a two-dimensional L-FMPBA-MOF, where L represents layered structure and F represents Fe. 3+ M represents Mn 2+ PBA (Prussian Blue Analogues) represents Prussian blue analogues, and MOF (Metal Organic Frameworks) represents metal-organic framework materials. The two-dimensional L-FMPBA-MOF is a metal-organic framework material with a two-dimensional sheet-like structure, and the metal ion in the metal-organic framework material is Fe. 3+ and Mn 2+ The X-ray diffraction pattern of the two-dimensional L-FMPBA-MOF exhibits diffraction characteristics of Prussian blue analogues.

[0037] The two-dimensional sheet-like structure of the two-dimensional L-FMPBA-MOF of this invention enables efficient ion transport within a hybrid matrix membrane by constructing ultrashort transport channels. Simultaneously, two metal ions, Fe, are introduced into the two-dimensional L-FMPBA-MOF. 3+ and Mn 2+ Formation of bimetallic sites, Fe 3+ and Mn 2+ Complementary in coordination environment and ion exchange mechanism, Fe 3+ The nodes provide a stable framework and charge density center, Mn 2+ The nodes introduce more active sites, and the synergistic effect of both lowers the specific ion migration barrier, enabling the active sites to efficiently carry out Rb transport through ion exchange mechanisms in solution. + and Cs + Adsorption effectively enhanced Rb + and Cs + The adsorption efficiency.

[0038] The preparation method of the two-dimensional L-FMPBA-MOF of the present invention includes the following steps:

[0039] S1, PVP is coordinated with soluble manganese salt and soluble iron salt to obtain FMPBA-MOF precursor;

[0040] S2, the FMPBA-MOF precursor is peeled off to obtain a two-dimensional L-FMPBA-MOF with bimetallic sites.

[0041] In this invention, PVP is used as a structure directing agent, and the amide groups (-CON-) on its molecular chain can react with metal ions (Mn). 2+ and Fe 3+ Through weak coordination or hydrogen bonding, an organic coating layer is formed during the crystal nucleation stage, inhibiting disordered particle aggregation and excessive growth, thus enabling the material to tend towards two-dimensional growth. The resulting FMPBA-MOF precursor has a layered structure, providing a structural basis for subsequent exfoliation. Secondly, PVP acts as a dispersant to ensure uniform reaction, laying the foundation for the exfoliation preparation of well-defined MOFs. The layered FMPBA-MOF precursor, through exfoliation, transforms its originally tightly stacked structure into a loose two-dimensional sheet-like structure, increasing active sites and resulting in two-dimensional L-FMPBA-MOFs with bimetallic sites.

[0042] In some preferred embodiments of the present invention, S1 specifically includes:

[0043] (1) Dissolve PVP in a mixed solution of ethanol and water, then add soluble manganese salt and tert-butanol (C4H4H2O). 10 O), stir until dissolved to form solution A; dissolve the soluble iron salt in water to form solution B;

[0044] (2) Add solution A dropwise to solution B and mix to obtain suspension C;

[0045] (3) The suspension C was stirred and reacted, then the solid and liquid were separated, the solid product D was collected and dried to obtain the FMPBA-MOF precursor.

[0046] The present invention prepares solutions A and B separately, and then blends them for two purposes: first, to ensure that the soluble manganese salt and soluble iron salt are fully dissolved before mixing, resulting in a more homogeneous bimetallic salt solution; second, the structure-directing agent PVP preferentially reacts with Mn. 2+ Pre-coordination occurs, forming a stable complex structure that can effectively regulate crystal nucleation and growth kinetics, thereby guiding the material to form a layered FMPBA-MOF precursor that is conducive to subsequent exfoliation.

[0047] In a further preferred embodiment of the present invention, the ratio of polyvinylpyrrolidone, ethanol, water, soluble manganese salt, and tert-butanol in solution A is (200~300) mg: (30~40) mL: (20~40) mL: (140.5~169.5) mg: (30~95) mL. Step (1) involves stirring at room temperature (15~35 ℃) until dissolved, at a stirring speed of 500~800 rpm, to form solution A.

[0048] In a further preferred embodiment of the present invention, in step (2), the dropping rate of solution A into solution B is 10~30 mL / min.

[0049] In a further preferred embodiment of the present invention, in step (3), the stirring speed is 300~600 rpm and the reaction time is 8~12 h; the solid-liquid separation is carried out by centrifugation at a speed of 8500~10000 rpm, and the collected solid product D is dried to constant weight at a constant temperature of 50~80 ℃ for 48~72 h to obtain the FMPBA-MOF precursor.

[0050] In some preferred embodiments of the present invention, the soluble manganese salt is manganese sulfate monohydrate (MnSO4·H2O), and the soluble iron salt is potassium ferricyanide (K3[Fe(CN)6]). 4- The ions have highly ordered multi-coordination properties and can act as bridging units to form ordered coordination structures with manganese ions.

[0051] In some preferred embodiments of the present invention, the mass ratio of polyvinylpyrrolidone to soluble manganese salt and soluble iron salt is (200~300) mg:(140.5~169.5) mg:(140.5~169.5) mg.

[0052] In some preferred embodiments of the present invention, S2 specifically includes: mixing the FMPBA-MOF precursor with hydrochloric acid solution (HCl), water, and N,N-dimethylformamide (DMF), reacting at a constant temperature, separating the solid product, washing, and drying to obtain a two-dimensional L-FMPBA-MOF with bimetallic sites. The present invention uses hydrochloric acid solution treatment to loosen the structure of the FMPBA-MOF precursor and remove impurity phases, weakening the metal-ligand interaction forces to achieve exfoliation, while simultaneously adjusting the surface charge of the two-dimensional L-FMPBA-MOF, which is beneficial for the adsorption of alkali metal ions.

[0053] In a further preferred embodiment of the present invention, the ratio of hydrochloric acid solution, water, and N,N-dimethylformamide is (5~15) mL:(5~15) mL:(10~45) mL, and the reaction at a constant temperature is specifically carried out at 60~100 °C for 6~28 h. The separated solid product is dried at 50~80 °C for 48~72 h to constant weight to obtain a two-dimensional L-FMPBA-MOF with bimetallic sites.

[0054] The two-dimensional L-FMPBA-MOF obtained by the above-described preparation method of the present invention has a two-dimensional sheet-like structure, enabling it to efficiently transport ions in a hybrid matrix membrane by constructing ultrashort transport channels; simultaneously, the two-dimensional L-FMPBA-MOF has bimetallic sites, and the bimetallic (Fe) 3+ and Mn 2+ The introduction of ) provides more affinity sites for specific ions while lowering the energy barrier for ion transport and adsorption, resulting in highly efficient and selective adsorption of Rb. + and Cs + .

[0055] Based on the two-dimensional L-FMPBA-MOF described above, the present invention provides a hybrid matrix membrane, wherein the hybrid matrix membrane uses polyvinylidene fluoride as the matrix and is filled with a filler, wherein the filler is the two-dimensional L-FMPBA-MOF described in the present invention.

[0056] In some preferred embodiments of the present invention, the two-dimensional L-FMPBA-MOF accounts for 50% to 80% of the mass of the mixed matrix membrane.

[0057] In some preferred embodiments of the present invention, the thickness of the hybrid base film is 109~132 μm.

[0058] The method for preparing the hybrid matrix membrane is as follows: PVDF is dissolved in a mixed solution of ethanol and water to obtain a PVDF matrix solution; two-dimensional L-FMPBA-MOF is physically blended with the PVDF matrix solution to obtain a casting solution; the casting solution is cast and then dried to obtain the hybrid matrix membrane.

[0059] This invention prepares a product capable of efficiently adsorbing Rb by physically blending the prepared two-dimensional L-FMPBA-MOF with polyvinylidene fluoride and then undergoing phase inversion. + Cs + The present invention provides a mixed matrix membrane. The preparation process of the mixed matrix membrane is simple, the reaction is controllable, the raw materials are inexpensive and readily available, and the conditions are mild, which can promote the complementary advantages of the filler and the polymer matrix.

[0060] The two-dimensional L-FMPBA-MOF with bimetallic sites provided by this invention can be used to adsorb Rb in water. + and / or Cs +Specifically, a two-dimensional L-FMPBA-MOF was prepared into a hybrid matrix membrane as described above and used to adsorb Rb from water. + and / or Cs + The water body mentioned can be brine.

[0061] Example 1: Preparation of two-dimensional L-FMPBA-MOF

[0062] (1) Dissolve 200 mg of polyvinylpyrrolidone in a mixed solvent of 30 mL of ethanol and 20 mL of deionized water, then add 140.5 mg of manganese sulfate monohydrate and 30 mL of tert-butanol, and stir at room temperature (25 °C) and 500 rpm until completely dissolved to form a clear solution A.

[0063] (2) Dissolve 140.5 mg of potassium ferricyanide in 30 mL of deionized water to form solution B. Slowly add solution A to solution B at a dropping rate of 10 mL / min and mix thoroughly to obtain suspension C.

[0064] (3) The suspension C was stirred at 300 rpm for 10 h. After the reaction was completed, the solid product D was collected by centrifugation at 8500 rpm and dried at 50 °C for 48 h to obtain the FMPBA-MOF precursor.

[0065] (4) The obtained FMPBA-MOF precursor was mixed with 5 mL of hydrochloric acid solution (1 M), 5 mL of deionized water and 10 mL of N,N-dimethylformamide, and reacted at 80 °C for 12 h. After cooling, the product was centrifuged and washed three times with deionized water and ethanol, and finally dried at 60 °C for 48 h to constant weight to obtain two-dimensional L-FMPBA-MOF.

[0066] Example 2: Preparation of two-dimensional L-FMPBA-MOF

[0067] (1) Dissolve 300 mg of polyvinylpyrrolidone in a mixed solvent of 40 mL of ethanol and 40 mL of deionized water, then add 169.5 mg of manganese sulfate monohydrate and 95 mL of tert-butanol, and stir at room temperature (25 °C) and 800 rpm until completely dissolved to form a clear solution A.

[0068] (2) Dissolve 169.5 mg of potassium ferricyanide in 40 mL of deionized water to form solution B. Slowly add solution A to solution B at a dropping rate of 30 mL / min and mix thoroughly to obtain suspension C.

[0069] (3) The suspension C was stirred at 600 rpm for 10 h. After the reaction was completed, the solid product D was collected by centrifugation at 10000 rpm and dried at 80 ℃ for 72 h to obtain the FMPBA-MOF precursor.

[0070] (4) The obtained FMPBA-MOF precursor was mixed with 15 mL of hydrochloric acid solution (1 M), 15 mL of deionized water and 45 mL of N,N-dimethylformamide, and reacted at 80 °C for 12 h. After cooling, the product was centrifuged, washed three times with deionized water and ethanol, and finally dried at 60 °C to constant weight to obtain two-dimensional L-FMPBA-MOF.

[0071] Example 3: Preparation of two-dimensional L-FMPBA-MOF

[0072] (1) Dissolve 250 mg of polyvinylpyrrolidone in a mixed solvent of 35 mL of ethanol and 30 mL of deionized water, then add 165.5 mg of manganese sulfate monohydrate and 67 mL of tert-butanol, and stir at room temperature (25 °C) and 600 rpm until completely dissolved to form a clear solution A.

[0073] (2) Dissolve 165.5 mg of potassium ferricyanide in 35 mL of deionized water to form solution B. Slowly add solution A to solution B at a dropping rate of 20 mL / min and mix thoroughly to obtain suspension C.

[0074] (3) The suspension C was stirred at 450 rpm for 10 h. After the reaction was completed, the solid product D was collected by centrifugation at 9000 rpm and dried at 65 ℃ for 60 h to obtain the FMPBA-MOF precursor.

[0075] (4) The obtained FMPBA-MOF precursor was mixed with 10 mL of hydrochloric acid solution (1 M), 10 mL of deionized water and 25 mL of N,N-dimethylformamide, and reacted at 80 °C for 12 h. After cooling, the product was centrifuged, washed three times with deionized water and ethanol, and finally dried at 60 °C to constant weight to obtain two-dimensional L-FMPBA-MOF.

[0076] Example 4: Preparation of two-dimensional L-FMPBA-MOF

[0077] (1) Dissolve 250 mg of polyvinylpyrrolidone in a mixed solvent of 35 mL of ethanol and 30 mL of deionized water, then add 165.5 mg of manganese sulfate monohydrate and 67 mL of tert-butanol, and stir at room temperature (25 °C) and 600 rpm until completely dissolved to form a clear solution A.

[0078] (2) Dissolve 165.5 mg of potassium ferricyanide in 35 mL of deionized water to form solution B. Slowly add solution A to solution B at a dropping rate of 20 mL / min and mix thoroughly to obtain suspension C.

[0079] (3) The suspension C was stirred at 450 rpm for 10 h. After the reaction was completed, the solid product D was collected by centrifugation at 9000 rpm and dried at 65 ℃ for 60 h to obtain the FMPBA-MOF precursor.

[0080] (4) The obtained FMPBA-MOF precursor was mixed with 5 mL of hydrochloric acid solution (1 M), 5 mL of deionized water and 10 mL of N,N-dimethylformamide, and reacted at 60 °C for 6 h. After cooling, the product was centrifuged, washed three times with deionized water and ethanol, and finally dried at 60 °C for 48 h to constant weight to obtain two-dimensional L-FMPBA-MOF.

[0081] Example 5: Preparation of two-dimensional L-FMPBA-MOF

[0082] (1) Dissolve 250 mg of polyvinylpyrrolidone in a mixed solvent of 35 mL of ethanol and 30 mL of deionized water, then add 165.5 mg of manganese sulfate monohydrate and 67 mL of tert-butanol, and stir at room temperature (25 °C) and 600 rpm until completely dissolved to form a clear solution A.

[0083] (2) Dissolve 165.5 mg of potassium ferricyanide in 35 mL of deionized water to form solution B. Slowly add solution A to solution B at a dropping rate of 20 mL / min and mix thoroughly to obtain suspension C.

[0084] (3) The suspension C was stirred at 450 rpm for 10 h. After the reaction was completed, the solid product D was collected by centrifugation at 9000 rpm and dried at 65 ℃ for 60 h to obtain the FMPBA-MOF precursor.

[0085] (4) The obtained FMPBA-MOF precursor was mixed with 15 mL of hydrochloric acid solution (1 M), 15 mL of deionized water and 45 mL of N,N-dimethylformamide, and reacted at 100 °C for 28 h. After cooling, the product was centrifuged and washed three times with deionized water and ethanol, and finally dried at 60 °C for 48 h to constant weight to obtain two-dimensional L-FMPBA-MOF.

[0086] Figure 1 This is an atomic force microscope image of the two-dimensional L-FMPBA-MOF prepared in Example 3. Figure 1As can be seen, L-FMPBA-MOF exhibits a two-dimensional nanosheet morphology with a nanosheet thickness of approximately 1 nm. This result demonstrates the successful fabrication of two-dimensional L-FMPBA-MOF materials and their ability to effectively construct ultrashort transport paths, providing a large specific surface area basis for the high exposure of bimetallic sites. Further fabrication of MMMs can significantly improve Rb. + Cs + The exchange efficiency is improved, effectively enhancing its adsorption performance.

[0087] Characterization showed that the two-dimensional L-FMPBA-MOFs prepared in Examples 1, 2, 4 and 5 all possessed typical two-dimensional sheet-like structures.

[0088] Figure 2 This is the XRD pattern of the two-dimensional L-FMPBA-MOF prepared in Example 3. In the XRD pattern, a strong characteristic peak (2...) appears in the low-angle region. θ The reflection peaks (≈11.9°) can be attributed to interlayer diffraction of the sheet-like structure in the (00l) direction. Meanwhile, typical reflection peaks of the Prussian blue analogue (PBA) framework still exist in the mid-to-high angle region, approximately at 17.4° (200), 24.7° (220), 35.2° (400), 39.5° (420), 43.4° (422), and 50.6° (440), indicating that the material retains the ordered structure of the Mn-Fe cyanide bridge framework after exfoliation. Therefore, this XRD pattern provides direct evidence for the coexistence of the "sheet-like structure + PBA framework" in the two-dimensional L-FMPBA-MOF. The sheet-like structure can provide higher outer surface / edge sites and shorter diffusion paths, while retaining the PBA framework provides a stable Mn-Fe cyanide bridge framework and potential coordination / ion exchange sites, which is beneficial to adsorption capacity and cycling stability.

[0089] Example 6: Preparation of Hybrid Matrix Membranes

[0090] 0.537 g of PVDF was weighed and dissolved in 10 mL of a 7:3 mixture of ethanol and water. The solution was heated and stirred in an 80 °C water bath for 2 h to ensure complete dissolution of the PVDF particles, resulting in a 6 wt% PVDF matrix solution. 0.28 g of the two-dimensional L-FMPBA-MOF prepared in Example 3 was physically blended with the 6 wt% PVDF matrix solution and stirred at room temperature for 4 h to obtain a casting solution. The casting solution was poured onto a clean petri dish for casting; dried at room temperature (25 °C) for 48 h, and then vacuum dried at 40 °C in a vacuum drying oven to remove residual solvent from the surface of the mixed matrix membrane, yielding a PVDF / L-FMPBA-MOF-50 mixed matrix membrane with a thickness of 116 μm. The two-dimensional L-FMPBA-MOF constitutes 50% of the PVDF / L-FMPBA-MOF-50 mixed matrix membrane, hence the name PVDF / L-FMPBA-MOF-50 MMMs.

[0091] This embodiment also tested the adsorption performance of the prepared PVDF / L-FMPBA-MOF-50 MMMs. Specifically, the prepared PVDF / L-FMPBA-MOF-50 MMMs were used for Rb adsorption. + and Cs + Adsorption test; the test steps are as follows:

[0092] Prepare Rb in an Erlenmeyer flask + and Cs + 100 mL of raw brine standards with concentrations of 30 ppm and 110 ppm were added to 5 g of PVDF / L-FMPBA-MOF-50 MMMs, placed in a shaker, and adsorbed at 160 rpm for 2 h at room temperature. After that, the amount of solute in the solution was measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0093] Test results show that the PVDF / L-FMPBA-MOF-50 MMMs have good resistance to Rb. + and Cs + The adsorption capacities were 0.48 mg / g and 0.68 mg / g, respectively.

[0094] Example 7: Preparation of Hybrid Matrix Membranes

[0095] In this embodiment, 0.336 g of the two-dimensional L-FMPBA-MOF prepared in Example 3 was physically blended with 6 wt% PVDF matrix solution. The mixture was stirred at room temperature for 4 h to obtain a casting solution, which was then poured onto a clean petri dish for casting. The mixture was dried at room temperature (25°C) for 48 h, and then vacuum dried at 40°C in a vacuum drying oven to remove residual solvent from the surface of the mixed matrix membrane, yielding a PVDF / L-FMPBA-MOF-60 mixed matrix membrane with a thickness of 125 μm. The two-dimensional L-FMPBA-MOF accounted for 60% of the mass of the PVDF / L-FMPBA-MOF-60 mixed matrix membrane, which was named PVDF / L-FMPBA-MOF-60MMMs.

[0096] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-60 MMMs was tested using the method described in Example 6. The test results showed that the PVDF / L-FMPBA-MOF-60 MMMs adsorbed Rb + and Cs + The adsorption capacities were 0.57 mg / g and 0.76 mg / g, respectively.

[0097] Example 8: Preparation of Hybrid Matrix Membranes

[0098] In this embodiment, 0.392 g of the two-dimensional L-FMPBA-MOF prepared in Example 3 was physically blended with 6 wt% PVDF matrix solution. The mixture was stirred at room temperature for 4 h to obtain a casting solution, which was then poured onto a clean petri dish for casting. The mixture was dried at room temperature (25°C) for 48 h, and then vacuum dried at 40°C in a vacuum drying oven to remove residual solvent from the surface of the mixed matrix membrane, yielding a PVDF / L-FMPBA-MOF-70 mixed matrix membrane with a thickness of 125 μm. The two-dimensional L-FMPBA-MOF accounted for 70% of the mass of the PVDF / L-FMPBA-MOF-70 mixed matrix membrane, and it was named PVDF / L-FMPBA-MOF-70MMMs.

[0099] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-70 MMMs was tested using the method described in Example 6. The test results showed that the PVDF / L-FMPBA-MOF-70 MMMs adsorbed Rb + and Cs + The adsorption capacities were 0.68 mg / g and 0.84 mg / g, respectively.

[0100] Example 9: Preparation of Hybrid Matrix Membranes

[0101] In this embodiment, 0.448 g of the two-dimensional L-FMPBA-MOF prepared in Example 3 was physically blended with 6 wt% PVDF matrix solution. The mixture was stirred at room temperature for 4 h to obtain a casting solution, which was then poured onto a clean petri dish for casting. The mixture was dried at room temperature (25°C) for 48 h, and then vacuum dried at 40°C in a vacuum drying oven to remove residual solvent from the surface of the mixed matrix membrane, yielding a PVDF / L-FMPBA-MOF-80 mixed matrix membrane with a thickness of 125 μm. The two-dimensional L-FMPBA-MOF accounted for 80% of the mass of the PVDF / L-FMPBA-MOF-80 mixed matrix membrane, and it was named PVDF / L-FMPBA-MOF-80MMMs.

[0102] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-80 MMMs was tested using the method described in Example 6. The test results showed that the PVDF / L-FMPBA-MOF-80 MMMs exhibited good adsorption properties for Rb. + and Cs + The adsorption capacities were 0.65 mg / g and 0.82 mg / g, respectively.

[0103] Example 10: Hybrid matrix membranes based on different MOF preparation conditions and their adsorption properties

[0104] Weigh 0.392 g of the two-dimensional L-FMPBA-MOF prepared in Example 1 and physically blend it with 6 wt% PVDF matrix solution (preparation method as in Example 6). Stir at room temperature for 4 h to obtain casting solution. Subsequent casting and drying steps are exactly the same as in Example 6 to obtain PVDF / L-FMPBA-MOF-70 MMMs.

[0105] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-70 MMMs was tested using the method described in Example 6. The test results showed that the PVDF / L-FMPBA-MOF-70 MMMs adsorbed Rb + and Cs + The adsorption capacities were 0.57 mg / g and 0.77 mg / g, respectively.

[0106] Example 11: Hybrid matrix membranes based on different MOF preparation conditions and their adsorption properties

[0107] 0.392 g of the two-dimensional L-FMPBA-MOF prepared in Example 2 was weighed and physically blended with 6 wt% PVDF matrix solution (prepared by the same method as in Example 6). The mixture was stirred at room temperature for 4 h to obtain a casting solution. The subsequent casting and drying steps were exactly the same as in Example 6 to obtain PVDF / L-FMPBA-MOF-70 MMMs.

[0108] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-70 MMMs was tested using the method described in Example 6. The test results showed that the PVDF / L-FMPBA-MOF-70 MMMs adsorbed Rb + and Cs + The adsorption capacities were 0.58 mg / g and 0.86 mg / g, respectively.

[0109] Example 12: Hybrid matrix membranes based on different MOF preparation conditions and their adsorption properties

[0110] Weigh 0.392 g of the two-dimensional L-FMPBA-MOF prepared in Example 4 and physically blend it with 6 wt% PVDF matrix solution (preparation method as in Example 6). Stir at room temperature for 4 h to obtain casting solution. The subsequent casting and drying steps are exactly the same as in Example 6 to obtain PVDF / L-FMPBA-MOF-70 MMMs.

[0111] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-70 MMMs was tested using the method described in Example 6. The test results showed that the PVDF / L-FMPBA-MOF-70 MMMs adsorbed Rb + Cs + The adsorption capacities were 0.53 mg / g and 0.79 mg / g, respectively.

[0112] Example 13: Hybrid matrix membranes based on different MOF preparation conditions and their adsorption properties

[0113] Weigh 0.392 g of the two-dimensional L-FMPBA-MOF prepared in Example 5 and physically blend it with 6 wt% PVDF matrix solution (preparation method as in Example 6). Stir at room temperature for 4 h to obtain casting solution. The subsequent casting and drying steps are exactly the same as in Example 6 to obtain PVDF / L-FMPBA-MOF-70 mixed matrix membrane.

[0114] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-70 MMMs was tested using the method described in Example 6. The test results showed that its Rb + Cs + The adsorption capacities were 0.56 mg / g and 0.81 mg / g, respectively.

[0115] Comparative Example 1: Preparation of filler-free pure PVDF membrane

[0116] As a comparison, 0.537 g of PVDF particles were weighed and dissolved in a mixed solution of ethanol and water with a mass ratio of 7:3. After stirring at 80 °C for 2 h, the resulting casting solution was poured onto a clean ultraflat petri dish for casting and dried at room temperature (25 °C) for 48 h. Then, it was placed in a vacuum oven at 40 °C for 24 h to remove residual solvent, resulting in a PVDF film with a thickness of 109 μm.

[0117] The adsorption performance of the prepared PVDF membrane was tested using the method described in Example 6. The test results showed that the PVDF membrane adsorbed Rb + and Cs + The adsorption capacities were 0.12 mg / g and 0.14 mg / g, respectively.

[0118] Comparative Example 2: Preparation of PVDF / L-FMPBA-MOF-70 particles

[0119] In comparison, in this embodiment, 0.392 g of the two-dimensional L-FMPBA-MOF prepared in Example 3 was physically blended with 6 wt% PVDF matrix solution and stirred at room temperature for 4 h to obtain a gel-like mixture with an L-FMPBA-MOF filling amount of 70 wt%. This mixture was slowly added to a granulator and extruded uniformly. Finally, it was dried at room temperature (25 ℃) for 48 h and then vacuum dried at 40 ℃ in a vacuum drying oven to remove residual solvent from the particle surface, resulting in a granular product of PVDF / L-FMPBA-MOF-70 with a diameter of approximately 3 mm and a length of 1 cm.

[0120] The adsorption performance of the prepared PVDF / L-FMPBA-MOF-70 particles was tested using the method described in Example 6. The test results showed that the PVDF / L-FMPBA-MOF-70 particles exhibited good adsorption performance for Rb. + and Cs + The adsorption capacities were 0.54 mg / g and 0.78 mg / g, respectively.

[0121] Comparative Example 3: Preparation of MMMs with FMPBA-MOF precursor as filler

[0122] In comparison, 0.392 g of the FMPBA-MOF precursor prepared in Example 3 was physically blended with 6 wt% PVDF matrix solution and stirred at room temperature for 4 h to obtain a casting solution. The casting solution was poured onto a clean petri dish for casting; dried at room temperature (25 ℃) for 48 h, and then vacuum dried at 40 ℃ in a vacuum drying oven to remove residual solvent from the surface of the mixed matrix film, yielding PVDF / FMPBA-MOF-70 MMMs. The thickness of this mixed matrix film was 125 μm. The FMPBA-MOF precursor accounted for 70% of the mass of PVDF / FMPBA-MOF-70 MMMs, and it was named PVDF / FMPBA-MOF-70 MMMs.

[0123] The adsorption performance of the prepared PVDF / FMPBA-MOF-70 MMMs was tested using the method described in Example 6. The test results showed that the PVDF / FMPBA-MOF-70 MMMs adsorbed Rb + and Cs + The adsorption capacities were 0.35 mg / g and 0.42 mg / g, respectively.

[0124] Comparing Examples 6-9, it can be seen that when the mass ratio of two-dimensional L-FMPBA-MOF in the mixed matrix membrane is 70%, the adsorption performance of the mixed matrix membrane is optimal.

[0125] Comparing Example 6 and Comparative Example 1, it can be seen that the PVDF membrane without two-dimensional L-FMPBA-MOF has a better effect on Rb + and Cs + The adsorption capacity is very low, indicating that the two-dimensional L-FMPBA-MOF of this invention has low adsorption capacity in Rb + and Cs + The important role of adsorption.

[0126] Comparing Example 6 and Comparative Example 2, it can be seen that, under the same two-dimensional L-FMPBA-MOF loading, there is a difference in the adsorption performance between PVDF / L-FMPBA-MOF-70 MMMs and PVDF / L-FMPBA-MOF-70 particles. The adsorption performance of the mixed matrix membrane formed by two-dimensional L-FMPBA-MOF and PVDF is better than that of the particles formed by two-dimensional L-FMPBA-MOF and PVDF.

[0127] Comparing Example 6 and Comparative Example 3, it can be seen that the adsorption effect of the unexfoliated FMPBA-MOF precursor as a filler is significantly lower than that of the exfoliated two-dimensional L-FMPBA-MOF as a filler. This further illustrates that the large specific surface area of ​​the two-dimensional sheet-like structure increases the exposure of active sites and shortens the ion transport path, significantly improving Rb adsorption.+ and Cs + Adsorption effect.

[0128] The above test results show that the hybrid matrix membranes prepared using two-dimensional L-FMPBA-MOF as filler in the various embodiments of the present invention have good Rb content. + and Cs + All of them exhibited excellent and stable adsorption performance.

[0129] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hybrid matrix membrane, characterized in that, The hybrid matrix membrane uses polyvinylidene fluoride (PVDF) as a matrix, and the matrix is ​​filled with two-dimensional L-FMPBA-MOF, which accounts for 70% of the mass of the hybrid matrix membrane. The two-dimensional L-FMPBA-MOF is a metal-organic framework material with a two-dimensional sheet-like structure, and the metal ion in the metal-organic framework material is Fe. 3+ and Mn 2+ The two-dimensional L-FMPBA-MOF exhibits the diffraction characteristics of a Prussian blue analog in X-ray diffraction patterns; The preparation method of the two-dimensional L-FMPBA-MOF includes the following steps: S1, Polyvinylpyrrolidone undergoes a coordination reaction with soluble manganese salt and soluble iron salt to obtain the FMPBA-MOF precursor; specifically including: (1) Dissolve polyvinylpyrrolidone in a mixed solution of ethanol and water, then add soluble manganese salt and tert-butanol, and stir until dissolved to form solution A; dissolve soluble iron salt in water to form solution B; (2) Add solution A dropwise to solution B and mix to obtain suspension C; (3) The suspension C was stirred for 8-12 h, then the solid and liquid were separated, the solid product D was collected and dried to obtain the FMPBA-MOF precursor; S2, the FMPBA-MOF precursor is mixed with 1 M hydrochloric acid solution, water and N,N-dimethylformamide, and reacted at a constant temperature. The solid product is separated, washed and dried to obtain the two-dimensional L-FMPBA-MOF. The ratio of 1 M hydrochloric acid solution, water and N,N-dimethylformamide is (5~15) mL: (5~15) mL: (10~45) mL.

2. The hybrid matrix membrane according to claim 1, characterized in that, The soluble manganese salt is manganese sulfate monohydrate, and the soluble iron salt is potassium ferricyanide.

3. The hybrid matrix membrane according to claim 1, characterized in that, The mass ratio of polyvinylpyrrolidone to soluble manganese salt and soluble iron salt is (200~300) mg: (140.5~169.5) mg: (140.5~169.5) mg.

4. The hybrid matrix membrane according to claim 1, characterized in that, The reaction is carried out at a constant temperature of 60~100 ℃ for 6~28 h.

5. The hybrid matrix membrane of claim 1 in adsorbing Rb in water + and / or Cs + Applications in this area.

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