MOF (Metal Organic Framework)-based porous nanofiber fluid permeable membrane with ionized water layer regulation and control function as well as preparation method and application of MOF-based porous nanofiber fluid permeable membrane
By growing an MOF layer in situ on a flexible SiO2 nanofiber membrane and constructing a PDA/PEI shell, the problem of low ion flux and power density of permeation energy conversion membrane materials was solved, achieving high selectivity and high flux permeation energy conversion effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-07
AI Technical Summary
Existing permeation energy conversion membrane materials have the problem that it is difficult to improve ion selectivity and permeability simultaneously. MOF membranes tend to be densely packed during the interface growth process, resulting in insufficient number of pores and high energy barrier for desolvation of hydrated ions, leading to low ion flux and low power density.
MOF layers were grown in situ on the surface of flexible SiO2 nanofiber membranes and constructed using PDA/PEI shells to regulate the desolvation process of hydrated ions. The ion transport channels were optimized by combining the potential characteristics of SiO2 nanofibers.
It significantly improves ion flux and power density, achieves highly selective and high-flux permeation energy conversion, reduces transport energy barriers, enhances membrane performance, and the preparation method is environmentally friendly and cost-effective.
Smart Images
Figure CN121797111A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a MOF-based porous nanofiber fluid permeation membrane with ion hydration layer regulation function, its preparation method and application, belonging to the field of nanofluid membrane and permeation energy conversion technology. Background Technology
[0002] Infiltration energy is a renewable energy source generated by mixing solutions of different salinities and is considered one of the most promising clean energy sources. Reverse electrodialysis (RED) technology converts the concentration difference between seawater and river water into electricity.
[0003] Currently, membrane materials used for permeation energy conversion mainly include polymer ion exchange membranes and two-dimensional nanosheet films (such as graphene oxide, MXene, and molybdenum disulfide). Polymer ion exchange membranes generally suffer from the problem of difficulty in simultaneously improving ion selectivity and permeability, resulting in low energy conversion efficiency and difficulty in achieving high power density output. Two-dimensional nanosheets have the advantages of easily functionalizable surfaces, unique nanoscale pores, and scalability; therefore, two-dimensional nanosheet films can reduce ion transport resistance while exhibiting good ion selectivity. However, the fabrication process of these films is complex and costly, and the poor interlayer stability of the nanosheets leads to poor long-term operational stability.
[0004] Recently, metal-organic frameworks (MOFs) have shown promise in the field of permeation energy harvesting due to their well-defined pore structures and easily modifiable chemical properties. However, existing MOF membranes still face several challenges in application. First, during interfacial growth or assembly, MOFs tend to undergo dense packing, resulting in a significantly lower number of effective pores than theoretically expected, making it difficult to meet the demands of rapid ion transport. Furthermore, MOF pores typically lack effective interfacial control capabilities, preventing a significant reduction in the desolvation barrier for hydrated ions, thus limiting their performance improvement in permeation energy conversion.
[0005] Existing technologies, such as Photo-controllable ion-gated metal-organic framework MIL-53 sub-nanochannels for efficient osmotic energy generation (ACS Nano 2022, 16, 16343-16352), utilize hydration synthesis to obtain MOF films with regular pore structures and some permeation energy collection capabilities. However, their ion transport flux is still limited by the high dehydration barrier of hydrated ions in the MOF pores, resulting in low power density (<5 W / m²). 2 This makes it difficult to meet the requirements of nanofluid membranes in permeation energy conversion.
[0006] Therefore, it is necessary to develop a MOF composite nanofiber membrane with ion hydration layer regulation function to reduce the ion dehydration energy barrier while maintaining high selectivity, thereby achieving high ion flux and good ion selectivity to overcome the shortcomings of existing permeation energy conversion technology. Summary of the Invention
[0007] To address the shortcomings of existing technologies, the present invention aims to provide a MOF-based porous nanofiber fluid permeation membrane with ion hydration layer regulation function, its preparation method, and its application, in order to solve the problem of low ion flux and low power density caused by the high dehydration energy barrier of hydrated ions in existing permeation energy collection membranes.
[0008] To achieve the above objectives, the following technical solution is provided: The first objective of this invention is to provide a MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function. The MOF-based porous nanofiber fluid channel membrane includes a flexible SiO2 nanofiber membrane, a MOF layer grown in situ on the surface of the flexible SiO2 nanofiber membrane, and a polydopamine / polyethyleneimine (PDA / PEI) shell layer coated on the surface of the MOF by in situ polymerization.
[0009] In one embodiment, the MOF is ZIF-67 or ZIF-90.
[0010] In one embodiment, the MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function can achieve a power density of 12.1~12.5 W / m² in an electrolyte with a 50-fold NaCl concentration gradient. 2 It is far greater than the commercial standard of 5W / m 2 .
[0011] The second objective of this invention is to provide a method for preparing the MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function as described above, the method comprising the following steps: (1) Preparation of flexible nanofiber membrane substrate Tetraethyl orthosilicate, water, and oxalic acid were weighed and prepared into a sol, which was stirred at room temperature to form a precursor solution. The precursor solution was added to an electrospinning jet and electrospinned to obtain a hybrid fiber membrane. The hybrid fiber membrane was calcined to obtain a flexible nanofiber membrane. (2) In situ growth of MOF Metal salts and organic ligands are mixed and added to polyethylene glycol and ground thoroughly to obtain MOF precursor solution. The precursor solution is transferred to the flexible nanofiber membrane obtained in step (1), and after hot pressing, washing and drying, MOF composite membrane is obtained. (3) In-situ construction of PDA / PEI shell The MOF composite membrane obtained in step (2) was immersed in a Tris-HCl buffer solution containing dopamine and polyethyleneimine and reacted at room temperature. After the reaction, it was washed and dried to obtain a MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function.
[0012] In one embodiment, the molar ratio of tetraethyl orthosilicate, water and oxalic acid in step (1) is 1:10~15:0.01~0.05; preferably 1:10:0.01.
[0013] In one embodiment, the stirring time at room temperature in step (1) is 5 to 10 hours.
[0014] In one embodiment, the parameters of electrospinning in step (1) are: temperature 25~30℃, humidity 40~60%, voltage 10-25kV, receiving distance 5-30cm, and flow rate 0.5-10mL / h.
[0015] In one embodiment, the calcination conditions in step (1) are: heating to 600-800°C at a rate of 3-5°C / min and calcining for 1-2 hours.
[0016] In one embodiment, the substrate of the flexible nanofiber membrane in step (1) is SiO2, the fiber diameter is 100-600nm, and the membrane thickness is 10-200μm.
[0017] In one embodiment, the metal salt in step (2) includes either a cobalt salt or a zinc salt.
[0018] In one embodiment, the cobalt salt includes any one of cobalt nitrate, cobalt chloride, and cobalt sulfate; the zinc salt includes any one of zinc nitrate or zinc acetate.
[0019] In one embodiment, the organic ligand in step (2) includes either 2-methylimidazole or 2-formylimidazole.
[0020] In one embodiment, the molar ratio of the metal salt and organic ligand in step (2) is 1:3-1:6, and the mass fraction of polyethylene glycol is 5%-30%.
[0021] In one embodiment, the molecular weight of the polyethylene glycol in step (2) is 2000~4000.
[0022] In one embodiment, the MOF in step (2) is either ZIF-67 or ZIF-90 to provide regular sub-nanometer nanofluid channels.
[0023] In one embodiment, the precursor solution in step (2) has a mass fraction of 30-40%, based on the mass of the flexible nanofiber membrane.
[0024] In one embodiment, the pressure of hot pressing in step (2) is 10-20 kPa, the temperature is 100-130°C, and the time is 10-20 min; hot pressing allows MOF to grow in situ on the fiber surface.
[0025] In one embodiment, the washing in step (2) specifically involves washing with ethanol or deionized water 3-5 times.
[0026] In one embodiment, the drying temperature in step (2) is 70~80°C.
[0027] In one embodiment, the concentration of dopamine in the Tris-HCl buffer solution containing dopamine and polyethyleneimine in step (3) is 2~10 mg / mL.
[0028] In one embodiment, the concentration of polyethyleneimine in the Tris-HCl buffer solution containing dopamine and polyethyleneimine in step (3) is 2~10 mg / mL.
[0029] In one embodiment, the concentration of the Tris-HCl buffer solution in step (3) is 10~50 mmol / L, the water / methanol volume ratio is 1:1, and the pH is 8~9.
[0030] In one embodiment, the room temperature reaction time in step (3) is 2-4 hours; a PDA / PEI hydration control layer is formed on the MOF surface by Michael addition and dopamine self-polymerization reaction.
[0031] In one embodiment, the PDA / PEI shell thickness is 5-30 nm, the molar ratio of DA to PEI is 1:1-1:5, the composite membrane water contact angle is ≤20°, and it is connected to Cl through polar groups (such as hydroxyl and amino groups). - Water molecules in the hydrated shell compete to form hydrogen bonds, weakening its strong hydration structure and making Cl... - Partial desolvation occurs at the interface, thereby lowering the transport energy barrier and increasing transmembrane flux.
[0032] The third objective of this invention is to provide an application of the MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function described above in the preparation of osmotic energy conversion, salinity gradient power generation, and micro / nano-scale fluid devices.
[0033] The fourth objective of this invention is to provide an application of the MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function described above in permeation energy conversion.
[0034] In one embodiment, the application directly converts the chemical potential energy between two aqueous solutions with different salinities into electrical energy.
[0035] A fourth objective of this invention is to provide a method for improving the power density of permeation energy harvesting in MOF-based porous nanofiber fluid channel membranes, the method comprising the following: (1) Preparation of flexible nanofiber membrane substrate Tetraethyl orthosilicate, water, and oxalic acid were weighed and prepared into a sol, which was stirred at room temperature to form a precursor solution. The precursor solution was added to an electrospinning jet and electrospinned to obtain a hybrid fiber membrane. The hybrid fiber membrane was calcined to obtain a flexible nanofiber membrane. (2) In situ growth of MOF Metal salts and organic ligands are mixed and added to polyethylene glycol and ground thoroughly to obtain MOF precursor solution. The precursor solution is transferred to the flexible nanofiber membrane obtained in step (1), and after hot pressing, washing and drying, MOF composite membrane is obtained. (3) In-situ construction of PDA / PEI shell The MOF composite membrane obtained in step (2) was immersed in a Tris-HCl buffer solution containing dopamine and polyethyleneimine and reacted at room temperature. After the reaction, it was washed and dried to obtain a MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function.
[0036] Beneficial effects: (1) This invention constructs a PDA / PEI shell outside the MOF channels, utilizing the amino groups of PEI in the shell and Cl - The strong interaction between hydrated water and hydrated chloride ions (Cl) enables the hydration of chloride ions. - The regulation of the desolvation process has broken through the bottleneck of high energy barrier for dehydration of hydrated ions and limited ion transport in traditional MOF nanopores, effectively improving ion flux while ensuring high ion selectivity. (2) The SiO2 nanofiber membrane used in this invention has a negative zeta potential. When it comes into contact with a mixed solution with a salinity gradient, the SiO2 nanofiber can repel chloride ions and promote the diffusion of chloride ions in the MOF pores, thereby further increasing the possibility of it approaching the MOF nanopore channels and improving the ion transport flux. (3) The solvent-free MOF synthesis method and PDA / PEI in-situ polymerization method adopted in this invention effectively avoid the aggregation of MOF and PDA / PEI polymer on the surface of nanofiber membrane, and effectively improve the utilization rate of ion transport channels in MOF; in addition, the preparation method does not use organic solvents, which has significant advantages in terms of environmental impact and cost-effectiveness. Attached Figure Description
[0037] Figure 1SEM images of the nanofiber membranes prepared in Examples 1, 2, and Comparative Examples 1 and 2 are shown below; (a) is the SiO2 / ZIF-67 / PDA-PEI nanofiber membrane prepared in Example 1; (b) is the SiO2 / ZIF-90 / PDA-PEI nanofiber membrane prepared in Example 2; (c) is the SiO2 nanofiber membrane of Comparative Example 1; and (d) is the SiO2 / ZIF-67 nanofiber membrane of Comparative Example 2. Figure 2 The graph shows the relationship between the output power density and the external resistance of the composite membranes in Examples 1 and 2 under a 50-fold salinity gradient. Figure 3 The maximum output power density diagrams for Examples 1 and 2 and Comparative Examples 1 to 3 are shown under a 50-fold salinity gradient. Detailed Implementation
[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.
[0039] The testing method involved in this invention: 1. Morphological characteristics Using scanning electron microscopy (SEM, SU) The morphology of the fiber membrane sample was characterized by 8010 (Hitachi, Japan).
[0040] 2. Zeta potential The pore size distribution of the membrane was determined using a particle size and potential analyzer (Nano-ZS90, USA).
[0041] 3. Permeation energy conversion performance test A 50-fold freshwater / seawater salinity difference was simulated by injecting 0.01M NaCl solution into the left side of a dual-chamber electrochemical cell and 0.5M NaCl solution into the right side. A 5mm × 5mm sample was fixed between the two chambers, resulting in an effective test area of 0.03mm² for the membrane. 2 .
[0042] Using a pair of Ag / AgCl electrodes with saturated salt bridges and an adjustable external load resistor (R) L The relationship curves between transmembrane voltage and transmembrane current as a function of the external load resistance were recorded. The IV curves were obtained by applying a scan of -0.5V to 0.5V, with the scan rate fixed at 0.05V / s. The maximum output power density of the membrane was calculated using formula (1).
[0043] (1).
[0044] Example 1 A method for preparing a MOF composite nanofiber membrane with ion hydration layer regulation function, the specific steps of which are as follows: S1: Preparation of fiber membrane substrate Tetraethyl orthosilicate, water, and oxalic acid were mixed in a molar ratio of 1:10:0.01 to form a sol, which was stirred at room temperature for 8 hours to form a precursor solution. The precursor solution was added to an electrospinning jet and electrospinned under conditions of 20 kV voltage, 15 cm receiving distance, and 1 mL / h flow rate. The ambient temperature and humidity during the electrospinning process were 25 ± 3 °C and 45 ± 5%, respectively. After spinning, a hybrid fiber membrane was obtained. The obtained hybrid fiber membrane was calcined at 800 °C for 1 hour at a rate of 5 °C / min to remove the organic template, thereby obtaining a flexible SiO2 nanofiber membrane with a fiber diameter of 250–550 nm and a thickness of 80 μm. S2: In-situ growth of MOF 0.7g cobalt nitrate, 1.2g 2-methylimidazole, and 0.4g polyethylene glycol (molecular weight 4000) were mixed and ground for 20 min to obtain a ZIF-67 precursor solution. The precursor solution was transferred at 30 wt% onto the flexible SiO2 nanofiber membrane obtained in S1. A pressure of 18 kPa was applied by a hot press, and the membrane was heated to 110℃ for 20 min to allow ZIF-67 to grow in situ on the fiber surface. After the reaction, the membrane was repeatedly washed with ethanol and deionized water and then vacuum dried at 60℃ to obtain the MOF composite membrane. S3: In-situ construction of the PDA / PEI shell; The MOF composite membrane obtained in S2 was immersed in 20 ml of Tris-HCl buffer solution (50 mM, pH=8.5) containing dopamine (5 mg / mL) and polyethyleneimine (5 mg / mL), and reacted at room temperature (25 °C) for 2 h. After repeated washing with ethanol and deionized water, it was dried under vacuum at 80 °C to obtain the MOF composite nanofiber membrane with hydration regulation function.
[0045] The MOF composite nanofiber membrane with hydration regulation function obtained in this embodiment has a MOF layer and a PDA / PEI polymer shell coated on the fiber surface. The power density of the permeation energy collected by this membrane can reach 12.5 W / m³. 2 It is far greater than the commercial standard of 5W / m 2 .
[0046] Example 2 A method for preparing a MOF composite nanofiber membrane with hydration regulation function, the specific steps of which are as follows: S1: Preparation of fiber membrane substrate Tetraethyl orthosilicate, water, and oxalic acid were mixed in a molar ratio of 1:10:0.01 to form a sol, which was stirred at room temperature for 8 hours to form a precursor solution. The precursor solution was added to an electrospinning jet and electrospinned under conditions of 20 kV voltage, 15 cm receiving distance, and 1 mL / h flow rate. The ambient temperature and humidity during the electrospinning process were 25 ± 3 °C and 45 ± 5%, respectively. After spinning, a hybrid fiber membrane was obtained. The obtained hybrid fiber membrane was calcined at 800 °C for 1 hour at a rate of 5 °C / min to remove the organic template, thereby obtaining a flexible SiO2 nanofiber membrane with a fiber diameter of 250–550 nm and a thickness of 80 μm. S2: In-situ growth of MOF 0.5 g zinc acetate, 1.8 g 2-formylimidazole, and 0.3 g polyethylene glycol (molecular weight 4000) were mixed and ground for 20 min to obtain a ZIF-90 precursor solution. The precursor solution was transferred at 30 wt% onto the flexible SiO2 nanofiber membrane obtained in S1. A pressure of 20 kPa was applied by a hot press, and the membrane was heated to 120 °C for 20 min to allow ZIF-90 to grow in situ on the fiber surface. After the reaction, the membrane was repeatedly washed with ethanol and deionized water and then vacuum dried at 60 °C to obtain a MOF composite membrane. S3: In-situ construction of the PDA / PEI shell The MOF composite membrane obtained in S2 was immersed in 20 mL of Tris-HCl buffer solution (50 mM, pH=8.5) containing dopamine (5 mg / mL) and polyethyleneimine (5 mg / mL), and reacted at room temperature (25 °C) for 2 h. It was then repeatedly washed with ethanol and deionized water and vacuum dried at 80 °C to obtain a MOF composite nanofiber membrane with hydration regulation function.
[0047] The MOF composite nanofiber membrane with hydration regulation function obtained in this embodiment has a MOF layer and a PDA / PEI polymer shell coated on the fiber surface. The power density of the permeation energy collected by this membrane can reach 12.1 W / m³. 2 It is far greater than the commercial standard of 5W / m 2 .
[0048] Comparative Example 1 The only difference from Example 1 is that only a flexible SiO2 nanofiber membrane was obtained.
[0049] The SEM image of the product prepared in this comparative example is as follows: Figure 1 As shown in c, compared with Example 1, the sample of Comparative Example 1 only contains nanofibers, without MOF layer structure and PDA / PEI shell.
[0050] The power density of the permeation energy collected by the comparative example flexible SiO2 nanofiber membrane is 0.08 W / m.2 .
[0051] Comparative Example 2 The only difference from Example 1 is that step S3: the in-situ construction process of the PDA / PEI shell is omitted, and only the MOF composite membrane is obtained.
[0052] The SEM image of the product prepared in this comparative example is as follows: Figure 1 As shown in d, compared with Example 1, the final sample obtained in Comparative Example 2 only contained MOF-coated nanofibers, without the PDA / PEI shell.
[0053] The MOF composite membrane obtained in this comparative example achieves a power density of 3.5 W / m² for permeation energy collection. 2 Less than the commercial standard of 5W / m 2 .
[0054] Comparative Example 3 The only difference from Example 1 is that step S3: only PDA in-situ construction is used, and other parameters and conditions are the same as in Example 1.
[0055] The MOF composite membrane obtained in this comparative example achieves a power density of 3.6 W / m² for permeation energy collection. 2 Less than the commercial standard of 5W / m 2 .
[0056] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.
Claims
1. A MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function, characterized in that, The MOF-based porous nanofiber fluid channel membrane includes a flexible SiO2 nanofiber membrane, an MOF layer grown in situ on the surface of the flexible SiO2 nanofiber membrane, and a polydopamine / polyethyleneimine shell layer coated on the surface of the MOF by in situ polymerization.
2. The MOF-based porous nanofiber fluid channel membrane according to claim 1, characterized in that, The MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function can achieve a power density of 12.1~12.5 W / m² in an electrolyte with a 50-fold NaCl concentration gradient. 2 It is far greater than the commercial standard of 5W / m 2 .
3. A method for preparing a MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function as described in claim 1, characterized in that, The method includes the following steps: (1) Preparation of flexible nanofiber membrane substrate Tetraethyl orthosilicate, water, and oxalic acid were weighed and prepared into a sol, which was stirred at room temperature to form a precursor solution. The precursor solution was added to an electrospinning jet and electrospinned to obtain a hybrid fiber membrane. The hybrid fiber membrane was calcined to obtain a flexible nanofiber membrane. (2) In situ growth of MOF Metal salts and organic ligands are mixed and added to polyethylene glycol and ground thoroughly to obtain MOF precursor solution. The precursor solution is transferred to the flexible nanofiber membrane obtained in step (1), and after hot pressing, washing and drying, MOF composite membrane is obtained. (3) In-situ construction of PDA / PEI shell The MOF composite membrane obtained in step (2) was immersed in a Tris-HCl buffer solution containing dopamine and polyethyleneimine and reacted at room temperature. After the reaction, it was washed and dried to obtain a MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function.
4. The method according to claim 3, characterized in that, The molar ratio of tetraethyl orthosilicate, water and oxalic acid in step (1) is 1:10~15:0.01~0.
05.
5. The method according to claim 3, characterized in that, The precursor solution in step (2) has a mass fraction of 30-40%, based on the mass of the flexible nanofiber membrane.
6. The method according to claim 3, characterized in that, The hot-pressing composite in step (2) has a pressure of 10-20 kPa, a temperature of 100-130℃, and a time of 10-20 min; the hot-pressing composite allows the MOF to grow in situ on the fiber surface.
7. The method according to claim 3, characterized in that, In step (3), the concentration of dopamine in the Tris-HCl buffer solution containing dopamine and polyethyleneimine is 2~10 mg / mL.
8. The method according to claim 3, characterized in that, The room temperature reaction time in step (3) is 2-4 hours; a PDA / PEI hydration control layer is formed on the MOF surface through Michael addition and dopamine self-polymerization reaction.
9. The application of the MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function as described in claim 1 in the preparation of osmotic energy conversion, salinity gradient power generation, and micro / nano-scale fluid devices.
10. A method for improving the power density of permeation energy harvesting in MOF-based porous nanofiber fluid channel membranes, characterized in that, The method includes the following: (1) Preparation of flexible nanofiber membrane substrate Tetraethyl orthosilicate, water, and oxalic acid were weighed and prepared into a sol, which was stirred at room temperature to form a precursor solution. The precursor solution was added to an electrospinning jet and electrospinned to obtain a hybrid fiber membrane. The hybrid fiber membrane was calcined to obtain a flexible nanofiber membrane. (2) In situ growth of MOF Metal salts and organic ligands are mixed and added to polyethylene glycol and ground thoroughly to obtain MOF precursor solution. The precursor solution is transferred to the flexible nanofiber membrane obtained in step (1), and after hot pressing, washing and drying, MOF composite membrane is obtained. (3) In-situ construction of PDA / PEI shell The MOF composite membrane obtained in step (2) was immersed in a Tris-HCl buffer solution containing dopamine and polyethyleneimine and reacted at room temperature. After the reaction, it was washed and dried to obtain a MOF-based porous nanofiber fluid channel membrane with ion hydration layer regulation function.