Disclosure of Invention
Aiming at the defects of the propranolol separation technology, the membrane separation technology and the traditional molecularly imprinted membrane technology, the invention aims to overcome the technical defects in the prior art and explore and evaluate the propranolol separation performance and the separation stability of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane aiming at the bottleneck problem of the molecularly imprinted membrane material. According to the invention, a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane with high adsorbability and high selectivity is constructed by using a porous and transparent structure of a polycarbonate track etching imprinted membrane and combining polydopamine and its coordinated MOFs modified composite layer as a substrate and optimally designing a sol-gel imprinting process. The method overcomes the technical defects in the prior art, researches and evaluates the propranolol separation performance and separation stability of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane aiming at the bottleneck problem of a molecularly imprinted membrane material, researches the relevance between membrane preparation and performance, and the selective separation mechanism and separation process of the imprinted membrane through adsorption and selective permeation experiments, realizes the synergistic enhancement of selective permeability and flux, and finally realizes the selective adsorption and separation of propranolol. The method widens the application field and the selection range of the membrane separation material, realizes the preparation of the molecularly imprinted membrane with high osmotic selectivity, high flux and high structure stability, and provides a new theoretical support for further perfecting the recognition mechanism and the osmosis mechanism in the selective separation process of the molecularly imprinted membrane.
The present invention achieves the above technical objects by the following technical means.
The preparation method of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane comprises the following steps:
s1, preparing a polydopamine modified polycarbonate track etching film: dissolving tris (hydroxymethyl) aminomethane hydrochloride and dopamine hydrochloride in deionized water to obtain a mixed solution, adjusting the pH value of the mixed solution, immersing the polycarbonate track etching membrane into the mixed solution, oscillating for a period of time at room temperature, washing with water, and drying to obtain a polydopamine modified polycarbonate track etching membrane;
s2, preparing a ZIF/poly dopamine-based polycarbonate track etching film: immersing the polydopamine modified polycarbonate track-etched membrane prepared in the step S1 into a solution containing a certain amount of Zn (NO)3)2·6H2Standing for a period of time in a methanol solution of O; then adding a methanol solution of 2-methylimidazole, carrying out oscillation reaction at room temperature for a period of time, after the reaction is finished, cleaning a final product by using methanol, and drying at a certain temperature to obtain a ZIF/poly dopamine-based polycarbonate track etching membrane;
s3, preparing a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane: dissolving a certain amount of propranolol and aminopropyltriethoxysilane in ethanol, stirring at room temperature to fully dissolve the propranolol and the aminopropyltriethoxysilane, adding tetraethyl orthosilicate, and continuously stirring for a certain time to obtain a mixed solution; and finally, immersing the ZIF/poly dopamine-based polycarbonate track etching membrane prepared in the step S2 into the mixed solution, adding ammonia water to initiate sol-gel imprinting polymerization, continuously stirring the whole reaction process for a certain time to obtain a final product, washing the final product for multiple times by using eluent to remove template molecules and unreacted monomers, washing the final product by using methanol, and drying the final product in vacuum to obtain the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinting membrane.
For comparison, the synthesis method of the non-imprinted membrane is similar to that of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, except that the template molecule propranolol is not added in the whole synthesis process.
Preferably, in step S1, the carbonate track etching membrane is a commercially available membrane with a diameter of 25cm and a pore size of 0.2 μm.
Preferably, in step S1, the dosage ratio of the tris (hydroxymethyl) aminomethane hydrochloride, dopamine hydrochloride and deionized water is 0.12g:0.2g:100 mL; the pH value of the mixed solution is adjusted to be 8.5.
Preferably, in step S1, the polycarbonate track etching film is immersed in the mixed solution in an amount of 1 to 2 sheets; the shaking time is 6.0h under the room temperature condition.
Preferably, in step S2, the polydopamine modified polycarbonate track etching membrane prepared in step S1 is immersed in the mixed solution in an amount of 1 to 2 sheets, and the diameter of the membrane is 25 cm.
Preferably, in step S2,the Zn (NO)3)2·6H2The dosage ratio of O, methanol A, 2-methylimidazole and methanol B is 0.595g to 20 mL: 0.3284g, 20 mL.
Preferably, in step S2, the standing time is 30 min; the oscillation reaction is carried out for 60 min; the temperature of the drying is 45 ℃.
Preferably, in step S3, the ratio of the propranolol to the aminopropyltriethoxysilane to the ethanol to the tetraethyl orthosilicate is 0.25 mmol/0.5 mL/45 mL/1.5 mL/0.5 mL.
Preferably, in step S3, the ZIF/poly dopamine-based polycarbonate track etching membrane is immersed in the mixed solution in an amount of 1 sheet, and the diameter of the membrane is 25 cm.
Preferably, in step S3, the stirring is performed for 30 min; the sol-gel imprinting polymerization time is 8-12 h.
Preferably, in step S3, the eluent is a mixed solution of methanol and acetic acid, and the volume ratio of methanol to acetic acid is 95: 5.
Preferably, in step S3, the elution is performed by shaking at room temperature, changing the eluent every 3 hours, and the elution lasts for 3 days.
The carbonate track etching membrane in the technical scheme is used as a base membrane material for preparing a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane.
The tris (hydroxymethyl) aminomethane hydrochloride described in the above technical scheme functions as a buffer.
The dopamine hydrochloride in the technical scheme is used as a carbonate track etching film modifier and a secondary reaction platform of a poly dopamine-based MOFs composite layer.
Zn (NO) as defined in the above technical solution3)2·6H2And O solution which is used as a Zn source of the nano composite modified layer.
The propranolol in the technical scheme is used as a template molecule.
The aminopropyl triethoxysilane and tetraethyl orthosilicate in the technical scheme are used as a functional monomer and a cross-linking agent of a sol-gel imprinting system.
The ammonia water in the technical scheme acts as an initiator in the sol-gel imprinting process.
The methanol in the technical scheme is used as a solvent.
The ethanol in the technical scheme is used as a solvent.
The invention also comprises the application of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane in the selective adsorption and separation of propranolol in a propranolol-containing mixed solution, and particularly in the selective adsorption and separation of propranolol in a mixed solution of propranolol, atenolol, bisoprolol and celiprolol.
Testing the performance of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane:
(1) isothermal adsorption experiment
Respectively weighing 7 parts of three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and non-imprinted membrane, respectively putting the membranes into test tubes, respectively adding 10mL of propranolol aqueous solution with the concentration of 10, 30, 60, 90, 120, 150 and 200mg/L, standing and adsorbing for 30min at room temperature, measuring the concentration of the unadsorbed propranolol in the solution by using an ultraviolet-visible spectrophotometer after adsorption is finished, and calculating the adsorption capacity (Q) according to the resulte,mg/g):
Q=(C0-Ce)×V/m (1)
Wherein C is0(mg/L) and Ce(mg/L) is the concentration of propranolol molecules in the solution before and after adsorption, V (mL) is the volume of the adsorption solution, and m (g) is the mass of the added three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane or non-imprinted membrane.
(2) Dynamic adsorption experiment
Respectively weighing 8 parts of three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching blotting membrane and non-blotting membrane, putting the three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching blotting membrane and non-blotting membrane into a test tube, respectively adding 10mL of 90mg/L propranolol aqueous solution, standing and adsorbing for 5, 10, 15, 20, 30, 60, 90 and 120min at room temperature, and adsorbingAfter completion, the concentration of non-adsorbed propranolol in the solution was measured by an ultraviolet-visible spectrophotometer, and the amount of adsorption (Q) was calculated from the resultt,mg/g):
Qt=(C0-Ct)×V/m (2)
Wherein C is0(mg/L) and Ct(mg/L) is the concentration of propranolol molecules in the solution before and after adsorption, V (mL) is the volume of the adsorption solution, and m (g) is the mass of the added three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane or non-imprinted membrane.
(3) Selective adsorption experiment
Respectively weighing 4 parts of three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and non-imprinted membrane, putting the membrane into a test tube, respectively adding 10mL of 90mg/L mixed solution of propranolol, atenolol, bisoprolol and celiprolol, standing and adsorbing for 30min at room temperature, respectively measuring the concentrations of the unadsorbed propranolol, atenolol, bisoprolol and celiprolol in the solution by an ultraviolet-visible spectrophotometer after adsorption is finished, and calculating the adsorption quantity (Q) according to the resulte,mg/g):
Q=(90mg/L-C)×V/m (3)
Wherein C (mg/L) is the concentration of propranolol, atenolol, bisoprolol and celiprolol in the adsorbed solution, V (mL) is the volume of the adsorbed solution, and m (g) is the mass of the imprinted membrane or the non-imprinted membrane etched by the added three-dimensional porous MOFs/poly dopamine-based polycarbonate track.
(4) Permselectivity experiments
Placing the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane or non-imprinted membrane in the middle of an H-shaped glass tube to realize that the H-shaped glass tube is divided into two cavities which are completely the same by the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane or non-imprinted membrane, adding 100mL of ethanol mixed solution of propranolol, atenolol, bisoprolol and celiprolol with the concentration of 200mg/L into one cavity, simultaneously adding 100mL of deionized water into the other cavity, respectively taking 5mL of solution (permeate) from a pure solvent cavity and immediately backfilling 5mL of pure solvent to ensure that the two cavities have no pressure difference when 15, 30, 45, 60, 90, 120, 150 and 180min are carried out, and measuring propranolol, atenolol, celiprolol, and the like in the sample permeate liquid, Bisoprolol and celiprolol concentrations.
The invention has the advantages and the technical effects that:
(1) compared with the existing molecularly imprinted polymer, the three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane prepared by the invention has the advantages of easy recovery, convenient subsequent separation, no secondary pollution to separated substances, applicability to a continuous process and the like, and effectively solves the defects of difficult recovery, easy generation of secondary pollution and the like of the existing propranolol molecularly imprinted polymer; in addition, the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane prepared by the method has high selectivity on propranolol, and can effectively separate propranolol molecules from a mixed solution of propranolol, atenolol, bisoprolol and celiprolol.
(2) Compared with the existing molecular imprinting membrane, the invention utilizes the porous and transparent structure of the polycarbonate track etching membrane, combines polydopamine and the coordinated MOFs modified composite layer thereof as the substrate, and constructs the three-dimensional-porous MOFs/polydopamine-based polycarbonate track etching imprinting membrane with high adsorbability and high selectivity by optimally designing the sol-gel imprinting process. And (2) combining a sol-gel imprinting technology to construct a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, successfully realizing efficient imprinting of propranolol, improving the contact efficiency of propranolol and surface sites, and obtaining the high-density and high-selectivity propranolol imprinted polycarbonate track etching membrane.
(3) Compared with the existing molecularly imprinted membrane, the method solves the problems of uneven distribution, poor stability and the like of a nano composite layer, obtains a membrane surface with high specific surface area, high adsorbability and stable structure, integrates various modification and imprinting technologies to design a synergistic imprinting strategy, constructs propranolol imprinted sites with high selectivity, adsorption capacity and stability, realizes synergistic enhancement of selective permeability and flux, and establishes a novel method for separating and purifying propranolol based on a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane.
Detailed Description
The invention is further described with reference to the drawings and the detailed description.
Example 1:
s1, preparing a polydopamine modified polycarbonate track etching film:
taking a polycarbonate track etching membrane as a base membrane, dissolving 0.12g of tris (hydroxymethyl) aminomethane hydrochloride and 0.2g of dopamine hydrochloride in 100mL of deionized water to obtain a mixed solution, adjusting the pH value of the solution to 8.5, adding 2 sheets of the polycarbonate track etching membrane into the mixed solution, oscillating for 6 hours at room temperature, washing with water, and drying to obtain the polydopamine modified polycarbonate track etching membrane;
s2, preparing a ZIF/poly dopamine-based polycarbonate track etching film:
2 pieces of polydopamine modified polycarbonate track-etched membrane were immersed in a solution containing 0.595g of Zn (NO)3)2·6H2O in 20mL of methanol solution, and standing for 30 min. Then, 20mL of a methanol solution containing 0.3284g of 2-methylimidazole was added to the above solution, and the reaction was stirred at room temperature for 60 min. After the reaction is finished, cleaning the final product by using methanol, and drying at 40 ℃ to obtain a ZIF/poly dopamine-based polycarbonate track etching film for later use;
s3, preparing a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane:
0.25mmol of propranolol and 0.5mL of aminopropyltriethoxysilane were dissolved in 45mL of ethanol, stirred at room temperature to dissolve them sufficiently, and then 1.5mL of tetraethyl orthosilicate was added to the solution and stirred for another 30 min. And finally, adding 1 ZIF/poly dopamine-based polycarbonate track etching membrane and 0.5mL ammonia water into the mixed solution to initiate sol-gel imprinting polymerization, and continuously stirring the whole reaction process for 8 hours to obtain a final product. And finally, eluting the obtained membrane sample by using a methanol/acetic acid (V/V,95/5) mixed solution, removing template molecules and unreacted monomers, finally cleaning by using methanol, and drying in vacuum to obtain the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. For comparison, the synthesis method of the non-imprinted membrane is similar to that of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, except that the template molecule propranolol is not added in the whole synthesis process.
In fig. 1, a (a1, a2, a3), b (b1, b2, b3), c (c1, c2, c3) and d (d1, d2, d3) are respectively the scanning electron micrographs of a polycarbonate track etching film, a polydopamine modified polycarbonate track etching film, a ZIF/polydopamine based polycarbonate track etching film and a three-dimensional-porous MOFs/polydopamine based polycarbonate track etching blotting film: from a comparison of fig. 1 a and fig. 1 b, a polydopamine modified layer is clearly observed. As shown in fig. 1 c, after the MOFs are modified, a distinct MOFs-based nanocomposite structure is obtained. Finally, as shown in d in fig. 1, after sol-gel imprinting, an obvious polymer-based composite structure can be seen on the surface of the three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, which proves that the propranolol imprinted layer is successfully constructed on the surface of the membrane.
Fig. 2(a) is an isothermal adsorption curve of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and non-imprinted membrane, which are adsorbed in propranolol ethanol solutions with concentrations of 10, 30, 60, 90, 120, 150 and 200mg/L for 30min, and the adsorption results are shown in table 1 (a). The invention compares the propranolol adsorption capacity of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and the non-imprinted membrane, and discusses the propranolol adsorption capacity of the imprinted membrane on a template molecule by researching the isothermal adsorption curve of the imprinted membrane. The experimental results show that the prepared three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has far higher adsorption capacity on propranolol molecules than a non-imprinted membrane in propranolol solution with the concentration of 10-200 mg/L, namely the prepared molecularly imprinted membrane material has excellent adsorption selectivity and recognition capability on propranolol.
TABLE 1(a) isothermal adsorption data of three-dimensional porous MOFs/polydopamine-based polycarbonate track etching blotting membranes
Fig. 2(b) is a kinetic adsorption curve of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and the prepared non-imprinted membrane, the work compares the adsorption capacity of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and the prepared non-imprinted membrane to propranolol, and the kinetic adsorption process of propranolol is studied by controlling the contact time (5, 10, 15, 20, 30, 60, 90 and 120min) of the membrane and the propranolol solution in the experiment. The prepared three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and non-imprinted membrane are tested in propranolol solution with the concentration of 90mg/L, and the adsorption results are shown in the table 1 (b). The experimental result shows that the adsorption rate of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane shows a remarkable rapid adsorption rate within 20min, the adsorption amount is higher than 80% of the equilibrium adsorption amount, and the equilibrium is achieved within 30 min. The propranolol molecule on the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has obvious and rapid adsorption kinetic performance. It can be easily found that the non-imprinted membrane shows a much slower adsorption rate and a lower equilibrium adsorption amount compared with the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. The rapid kinetic adsorption performance probably comes from propranolol imprinted sites with high activity and high selectivity on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, namely the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has the effect of rapid selective adsorption and separation on propranolol.
TABLE 1(b) kinetic adsorption data of three-dimensional-porous MOFs/poly dopamine based polycarbonate track etching imprinted membranes
Fig. 2(c) is a selective adsorption curve of the prepared three-dimensional porous MOFs/polydopamine-based polycarbonate track etching imprinted membrane and non-imprinted membrane, in order to study specific adsorption performances of the three-dimensional porous MOFs/polydopamine-based polycarbonate track etching imprinted membrane and the non-imprinted membrane, an ethanol mixed solution of propranolol, atenolol, bisoprolol and celiprolol is selected to perform a specific adsorption experiment, the concentration of a competitive adsorption solution containing four compounds is 90mg/L, and the adsorption result is shown in table 1 (c). The three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has very high adsorption capacity to template molecule propranolol and is far greater than the adsorption capacity to atenolol, bisoprolol and celiprolol, because in the imprinting process, a specific space complementary imprinting cavity to propranolol is formed on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. In contrast, since propranolol molecules are not added during the preparation of the non-imprinted membrane, no imprinted sites having specific recognition and adsorption to propranolol are formed, the non-imprinted membrane exhibits similar and lower adsorption capacity to all molecules including propranolol, atenolol, bisoprolol and celiprolol. The results show that the prepared three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has higher specific adsorption capacity on propranolol.
TABLE 1(c) Selective adsorption data for three-dimensional porous MOFs/poly dopamine based polycarbonate track etch blotting membranes
The osmotic selectivity is an important index for testing the comprehensive performance of the molecularly imprinted membrane material, and the method researches the osmotic selectivity of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and further verifies the osmotic selectivity through a competitive permeation experiment. Fig. 2(d) is a concentration curve of a permeate obtained by the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane in a selective permeation experiment, a mixed solution with a concentration of 200mg/L is used as a stock solution, the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane is used as a permeation medium, the concentrations of propranolol, atenolol, bisoprolol and celiprolol in the permeate at 15, 30, 45, 60, 90, 120, 150 and 180min are detected, and the results of the permeation concentrations of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane to different molecules are shown in table 1 (d). The experimental result shows that the permeation flux of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane to propranolol is obviously lower than that of non-imprinted molecules such as atenolol, bisoprolol and celiprolol, which is probably because binding sites with specific adsorption capacity to template molecules propranolol are formed on the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane in the imprinting polymerization process, so that excellent selective separation capacity is shown. In addition, in the permeation process, propranolol can be adsorbed on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, and other non-template molecules such as atenolol, bisoprolol and celiprolol can hardly be subjected to the resistance of specific adsorption of imprinted sites, so that propranolol permeates through the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. The selective separation mechanism for molecularly imprinted membrane materials can be generalized into two distinct and opposite permeation mechanisms: promoting penetration and delaying penetration. The experimental results show that the propranolol molecule firstly contacts with the three-dimensional porous MOFs/poly dopamine based polycarbonate track to etch the imprinted site on the imprinted membrane and then is absorbed to the imprinted cavity, and atenolol, bisoprolol and celiprolol can directly pass through the three-dimensional porous MOFs/poly dopamine based polycarbonate track to etch the imprinted membrane through diffusion or convection.
TABLE 1(d) Selective permeation data for three-dimensional-porous MOFs/polydopamine based polycarbonate track etch blotting membranes
Example 2:
s1, preparing a polydopamine modified polycarbonate track etching film:
taking a polycarbonate track etching membrane as a base membrane, dissolving 0.12g of tris (hydroxymethyl) aminomethane hydrochloride and 0.2g of dopamine hydrochloride in 100mL of deionized water to obtain a mixed solution, adjusting the pH value of the solution to 8.5, adding 2 polycarbonate track etching membranes into the mixed solution, oscillating for 6h at room temperature, washing with water, and drying to obtain a polydopamine modified polycarbonate track etching membrane;
s2, preparing a ZIF/poly dopamine-based polycarbonate track etching film:
2 sheets of polydopamine modified polycarbonate track etch membrane were immersed in a solution containing 0.595g Zn (NO)3)2·6H2O in 20mL of methanol solution, and standing for 30 min. Then, 20mL of a methanol solution containing 0.3284g of 2-methylimidazole was added to the above solution, and the reaction was stirred at room temperature for 60 min. Reaction junctionAfter that, the final product is cleaned by methanol and dried at 40 ℃ to obtain a ZIF/poly dopamine-based polycarbonate track etching membrane for later use;
s3, preparing a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane:
dissolving 0.25mmol of propranolol and 0.5mL of aminopropyltriethoxysilane in 45mL of ethanol, stirring at room temperature to fully dissolve the propranolol and the aminopropyltriethoxysilane, adding 1.5mL of tetraethyl orthosilicate into the solution, and continuing stirring for 30 min; and finally, adding 1 ZIF/poly dopamine-based polycarbonate track etching membrane and 0.5mL ammonia water into the mixed solution to initiate sol-gel imprinting polymerization, and continuously stirring the whole reaction process for 10 hours to obtain a final product. And finally, eluting the obtained membrane sample by using a methanol/acetic acid (V/V,95/5) mixed solution, removing template molecules and unreacted monomers, finally cleaning by using methanol, and drying in vacuum to obtain the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. For comparison, the synthesis method of the non-imprinted membrane is similar to that of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, except that the template molecule propranolol is not added in the whole synthesis process.
Fig. 3(a) is an isothermal adsorption curve of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and non-imprinted membrane, which are adsorbed in propranolol ethanol solutions with concentrations of 10, 30, 60, 90, 120, 150 and 200mg/L for 30min, and the adsorption results are shown in table 2 (a). The invention compares the propranolol adsorption capacity of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and the non-imprinted membrane, and discusses the propranolol adsorption capacity of the imprinted membrane on a template molecule by researching the isothermal adsorption curve of the imprinted membrane. The experimental results show that the prepared three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has far higher adsorption capacity on propranolol molecules than a non-imprinted membrane in propranolol solution with the concentration of 10-200 mg/L, namely the prepared molecularly imprinted membrane material has excellent adsorption selectivity and recognition capability on propranolol.
TABLE 2(a) isothermal adsorption data for three-dimensional porous MOFs/polydopamine based polycarbonate track etch blotting membranes
Fig. 3(b) is a kinetic adsorption curve of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and the prepared non-imprinted membrane, the work compares the adsorption capacity of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and the prepared non-imprinted membrane to propranolol, and the kinetic adsorption process of propranolol is studied by controlling the contact time (5, 10, 15, 20, 30, 60, 90 and 120min) of the membrane and the propranolol solution in the experiment. The prepared three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and non-imprinted membrane are tested in propranolol solution with the concentration of 90mg/L, and the adsorption results are shown in the table 2 (b). The experimental result shows that the adsorption rate of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane shows a remarkable rapid adsorption rate within 20min, the adsorption amount is higher than 80% of the equilibrium adsorption amount, and the equilibrium is reached within 30 min. The propranolol molecule on the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has obvious and rapid adsorption kinetic performance. It can be easily found that the non-imprinted membrane shows a much slower adsorption rate and a lower equilibrium adsorption amount compared with the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. The rapid kinetic adsorption performance probably comes from propranolol imprinted sites with high activity and high selectivity on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, namely the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has the effect of rapid selective adsorption and separation on propranolol.
TABLE 2(b) kinetic adsorption data of three-dimensional porous MOFs/polydopamine-based polycarbonate track etching imprinted membrane
Fig. 3(c) is a selective adsorption curve of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and non-imprinted membrane, in order to study the specific adsorption performance of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and non-imprinted membrane, an ethanol mixed solution of propranolol, atenolol, bisoprolol and celiprolol was selected for a specific adsorption experiment, the concentration of a competitive adsorption solution containing four compounds was 90mg/L, and the adsorption results are shown in table 2 (c). The three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has very high adsorption capacity to template molecule propranolol and is far greater than the adsorption capacity to atenolol, bisoprolol and celiprolol, because in the imprinting process, a specific space complementary imprinting cavity to propranolol is formed on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. In contrast, since propranolol molecules are not added during the preparation of the non-imprinted membrane, no imprinted sites having specific recognition and adsorption to propranolol are formed, the non-imprinted membrane exhibits similar and lower adsorption capacity to all molecules including propranolol, atenolol, bisoprolol and celiprolol. The results show that the prepared three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has higher specific adsorption capacity on propranolol.
TABLE 2(c) Selective adsorption data for three-dimensional porous MOFs/poly dopamine based polycarbonate track etch blotting membranes
The osmotic selectivity is an important index for testing the comprehensive performance of the molecularly imprinted membrane material, and the method researches the osmotic selectivity of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and further verifies the osmotic selectivity through a competitive permeation experiment. Fig. 3(d) is a concentration curve of a permeate obtained by the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane in a selective permeation experiment, a mixed solution with a concentration of 200mg/L is used as a stock solution, the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane is used as a permeation medium, the concentrations of propranolol, atenolol, bisoprolol and celiprolol in the permeate at 15, 30, 45, 60, 90, 120, 150 and 180min are detected, and the results of the permeation concentrations of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane to different molecules are shown in table 2 (d). The experimental result shows that the permeation flux of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane to propranolol is obviously lower than that of non-imprinted molecules such as atenolol, bisoprolol and celiprolol, which is probably because binding sites with specific adsorption capacity to template molecules propranolol are formed on the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane in the imprinting polymerization process, so that excellent selective separation capacity is shown. In addition, in the permeation process, propranolol can be adsorbed on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, and other non-template molecules such as atenolol, bisoprolol and celiprolol can hardly be subjected to the resistance of specific adsorption of imprinted sites, so that propranolol permeates through the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. The selective separation mechanism for molecularly imprinted membrane materials can be generalized into two distinct and opposite permeation mechanisms: promoting penetration and delaying penetration. The experimental results show that the propranolol molecule firstly contacts with the three-dimensional porous MOFs/poly dopamine based polycarbonate track to etch the imprinted site on the imprinted membrane and then is absorbed to the imprinted cavity, and atenolol, bisoprolol and celiprolol can directly pass through the three-dimensional porous MOFs/poly dopamine based polycarbonate track to etch the imprinted membrane through diffusion or convection.
TABLE 2(d) Selective permeation data for three-dimensional-porous MOFs/polydopamine based polycarbonate track etch blotting membranes
Example 3:
s1, preparing a polydopamine modified polycarbonate track etching film:
taking a polycarbonate track etching membrane as a base membrane, dissolving 0.12g of tris (hydroxymethyl) aminomethane hydrochloride and 0.2g of dopamine hydrochloride in 100mL of deionized water to obtain a mixed solution, adjusting the pH value of the solution to 8.5, adding 2 sheets of polycarbonate track etching membranes into the mixed solution, oscillating for 6h at room temperature, washing with water, and drying to obtain the polydopamine modified polycarbonate track etching membrane.
S2, preparation of a ZIF/poly dopamine-based polycarbonate track etching film:
2 sheets of polydopamine modified polycarbonate track etch membrane were immersed in a solution containing 0.595g Zn (NO)3)2·6H2O in 20mL of methanol solution, and standing for 30 min. Then, 20mL of a methanol solution containing 0.3284g of 2-methylimidazole was added to the above solution, and the reaction was stirred at room temperature for 60 min. After the reaction is finished, the final product is washed by methanol and dried at 40 ℃ for later use.
S3, preparing a three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane:
0.25mmol of propranolol and 0.5mL of aminopropyltriethoxysilane were dissolved in 45mL of ethanol, stirred at room temperature until they were sufficiently dissolved, 1.5mL of tetraethyl orthosilicate was added to the solution, and stirring was continued for 30 min. And finally, adding 1 ZIF/poly dopamine-based polycarbonate track etching membrane and 0.5mL ammonia water into the mixed solution to initiate sol-gel imprinting polymerization, and continuously stirring the whole reaction process for 12 hours to obtain a final product. And finally, eluting the obtained membrane sample by using a methanol/acetic acid (V/V,95/5) mixed solution, removing template molecules and unreacted monomers, finally cleaning by using methanol, and drying in vacuum to obtain the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. For comparison, the synthesis method of the non-imprinted membrane is similar to that of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, except that the template molecule propranolol is not added in the whole synthesis process.
Fig. 4(a) is isothermal adsorption curves of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane and non-imprinted membrane, which are adsorbed in propranolol ethanol solutions with concentrations of 10, 30, 60, 90, 120, 150 and 200mg/L for 30min, and the adsorption results are shown in table 3 (a). The invention compares the propranolol adsorption capacity of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and the non-imprinted membrane, and discusses the propranolol adsorption capacity of the imprinted membrane on a template molecule by researching the isothermal adsorption curve of the imprinted membrane. The experimental results show that the prepared three-dimensional-porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has far higher adsorption capacity on propranolol molecules than a non-imprinted membrane in propranolol solution with the concentration of 10-200 mg/L, namely the prepared molecularly imprinted membrane material has excellent adsorption selectivity and recognition capability on propranolol.
TABLE 3(a) isothermal adsorption data for three-dimensional porous MOFs/polydopamine based polycarbonate track etch blotting membranes
Fig. 4(b) is a kinetic adsorption curve of the prepared three-dimensional porous MOFs/polydopamine-based polycarbonate track etching imprinted membrane and the prepared non-imprinted membrane, the work compares the adsorption capacities of the three-dimensional porous MOFs/polydopamine-based polycarbonate track etching imprinted membrane and the prepared non-imprinted membrane to propranolol, and the kinetic adsorption process of propranolol is studied by controlling the contact time (5, 10, 15, 20, 30, 60, 90 and 120min) of the membrane and a propranolol solution in an experiment. The prepared three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and non-imprinted membrane are tested in propranolol solution with the concentration of 90mg/L, and the adsorption results are shown in the table 3 (b). The experimental result shows that the adsorption rate of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane shows a remarkable rapid adsorption rate within 20min, the adsorption amount is higher than 80% of the equilibrium adsorption amount, and the equilibrium is achieved within 30 min. The propranolol molecule on the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has obvious and rapid adsorption kinetic performance. It can be easily found that the non-imprinted membrane shows a much slower adsorption rate and a lower equilibrium adsorption amount compared with the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. The rapid kinetic adsorption performance probably comes from propranolol imprinted sites with high activity and high selectivity on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, namely the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has the effect of rapid selective adsorption and separation on propranolol.
TABLE 3(b) kinetic adsorption data for three-dimensional porous MOFs/poly dopamine based polycarbonate track etch imprinted membranes
Fig. 4(c) is a selective adsorption curve of the prepared three-dimensional porous MOFs/polydopamine-based polycarbonate track etching imprinted membrane and non-imprinted membrane, in order to study specific adsorption performances of the three-dimensional porous MOFs/polydopamine-based polycarbonate track etching imprinted membrane and the non-imprinted membrane, an ethanol mixed solution of propranolol, atenolol, bisoprolol and celiprolol is selected to perform a specific adsorption experiment, the concentration of a competitive adsorption solution containing four compounds is 90mg/L, and the adsorption result is shown in table 3 (c). The three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has very high adsorption capacity to template molecule propranolol and is far greater than the adsorption capacity to atenolol, bisoprolol and celiprolol, because in the imprinting process, a specific space complementary imprinting cavity to propranolol is formed on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. In contrast, since propranolol molecules are not added during the preparation of the non-imprinted membrane, no imprinted site having specific recognition and adsorption to propranolol is formed, the non-imprinted membrane exhibits similar and lower adsorption capacity to all molecules including propranolol, atenolol, bisoprolol and celiprolol. The results show that the prepared three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane has higher specific adsorption capacity on propranolol.
TABLE 3(c) Selective adsorption data for three-dimensional porous MOFs/poly dopamine based polycarbonate track etch blotting membranes
The osmotic selectivity is an important index for testing the comprehensive performance of the molecularly imprinted membrane material, and the method researches the osmotic selectivity of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane and further verifies the osmotic selectivity through a competitive permeation experiment. Fig. 4(d) is a concentration curve of a permeate obtained by the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane in a selective permeation experiment, a mixed solution with a concentration of 200mg/L is used as a stock solution, the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane is used as a permeation medium, the concentrations of propranolol, atenolol, bisoprolol and celiprolol in the permeate at 15, 30, 45, 60, 90, 120, 150 and 180min are detected, and the results of the permeation concentrations of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane to different molecules are shown in table 3 (d). The experimental result shows that the permeation flux of the prepared three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane to propranolol is obviously lower than that of non-imprinted molecules such as atenolol, bisoprolol and celiprolol, which is probably because binding sites with specific adsorption capacity to template molecules propranolol are formed on the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane in the imprinting polymerization process, so that excellent selective separation capacity is shown. In addition, in the permeation process, propranolol can be adsorbed on the surface of the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane, and other non-template molecules such as atenolol, bisoprolol and celiprolol can hardly be subjected to the resistance of specific adsorption of imprinted sites, so that propranolol permeates through the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane. The selective separation mechanism for molecularly imprinted membrane materials can be generalized into two distinct and opposite permeation mechanisms: promoting penetration and delaying penetration. The experimental results show that the propranolol molecule firstly contacts with the three-dimensional porous MOFs/poly dopamine based polycarbonate track to etch the imprinted site on the imprinted membrane and then is absorbed to the imprinted cavity, and atenolol, bisoprolol and celiprolol can directly pass through the three-dimensional porous MOFs/poly dopamine based polycarbonate track to etch the imprinted membrane through diffusion or convection.
TABLE 3(d) Selective permeation data for three-dimensional-porous MOFs/polydopamine based polycarbonate track etch blotting membranes
Finally, as can be seen from the isothermal adsorption curve, the kinetic adsorption curve, the selective adsorption curve and the permeation selectivity curve of the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane on propranolol in FIGS. 2 to 4, the three-dimensional porous MOFs/poly dopamine based polycarbonate track etching imprinted membrane prepared by the invention has higher adsorption selectivity on propranolol in a mixed solution of propranolol and structural analogues thereof, and can realize effective separation of propranolol from analogues in a permeation process. In conclusion, the three-dimensional porous MOFs/poly dopamine-based polycarbonate track etching imprinted membrane prepared by the invention has higher osmotic selectivity and recognition performance on the template molecule propranolol, and can be used as an effective molecular imprinted membrane separation method for efficiently and selectively separating a target compound.
Description of the drawings: the above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; thus, while the present invention has been described in detail with reference to the various embodiments thereof, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted; all such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.