A ZIF-8/6 FDA-BI: DAM (1:1) hybrid membrane and preparation method and application thereof
阅读说明：本技术 一种zif-8/6fda-bi：dam(1:1)杂化膜及其制备方法和应用 (A ZIF-8/6 FDA-BI: DAM (1:1) hybrid membrane and preparation method and application thereof ) 是由 樊燕芳 李南文 袁茜娅 于 2021-07-07 设计创作，主要内容包括：本发明提供了一种ZIF-8/6FDA-BI：DAM(1:1)杂化膜及其制备方法和应用。该ZIF-8/6FDA-BI：DAM(1:1)杂化膜以6FDA-BI：DAM(1:1)为基质,以ZIF-8为填料,以该ZIF-8/6FDA-BI：DAM(1:1)杂化膜的总质量为100％计,填料ZIF-8的质量分数为10wt％-40wt％。本发明还提供了上述ZIF-8/6FDA-BI：DAM(1:1)杂化膜的制备方法。本发明的ZIF-8/6FDA-BI：DAM(1:1)杂化膜具有高MOFs负载量且界面无缺陷,可以用于分离H-(2)/CH-(4)混合气、CO-(2)/CH-(4)混合气。(The invention provides a ZIF-8/6 FDA-BI: DAM (1:1) hybrid membrane, and preparation method and application thereof. The ZIF-8/6 FDA-BI: DAM (1:1) hybrid membranes were prepared at 6FDA-BI: DAM (1:1) is used as a matrix, ZIF-8 is used as a filler, and the ZIF-8/6 is prepared by mixing the components of FDA-BI: the total mass of the DAM (1:1) hybrid membrane is 100%, and the mass fraction of the filler ZIF-8 is 10-40 wt%. The invention also provides the ZIF-8/6 FDA-BI: a method for preparing a DAM (1:1) hybrid membrane. ZIF-8/6FDA-BI of the present invention: DAM (1:1) hybrid membranes have high MOFs loading and no defects at the interface, and can be used for separating H 2 /CH 4 Mixed gas, CO 2 /CH 4 And (4) mixing the gases.)
1. A ZIF-8/6 FDA-BI: DAM (1:1) hybrid membrane, the ZIF-8/6 FDA-BI: DAM (1:1) hybrid membranes were prepared at 6FDA-BI: DAM (1:1) is used as a matrix, ZIF-8 is used as a filler, wherein the ZIF-8/6 FDA-BI: the total mass of the DAM (1:1) hybrid membrane is 100%, and the mass fraction of the filler ZIF-8 is 10-40 wt%.
2. The ZIF-8/6FDA-BI of claim 1: DAM (1:1) hybrid membrane, wherein the ZIF-8/6 FDA-BI: the thickness of the DAM (1:1) hybrid membrane is 40 μm-70 μm.
3. The ZIF-8/6FDA-BI of claim 1 or 2: a method for preparing a DAM (1:1) hybrid membrane, wherein the method comprises the following steps:
the ratio of 6FDA-BI: dissolving DAM (1:1) in a first solvent to obtain a first mixed solution;
dispersing ZIF-8 in a second solvent to obtain a second mixed solution;
mixing the first mixed solution with the second mixed solution to obtain a mixed solution; the first solution is added in the amount of 6FDA-BI: the mass of DAM (1:1), the adding amount of the second solution is calculated by the mass of ZIF-8, and the mass fraction of ZIF-8 in the mixed solution is 10-40%;
uniformly coating the mixed solution on a substrate, drying, separating a film from the substrate, soaking the film in anhydrous methanol for 12-24 h, drying, and thermally crosslinking at 200-400 ℃ for 10-24 h to obtain ZIF-8/6 FDA-BI: DAM (1:1) thermally crosslinked hybrid membranes.
4. The method according to claim 3, wherein the first solvent and the second solvent are the same and are selected from N, N-dimethylacetamide and N, N-dimethylformamide.
5. The preparation method according to claim 3, wherein, in the first mixed solution, the mixture is mixed at the ratio of 6FDA-BI: the addition amount of the first solvent is 0.05g/mL-0.1g/mL by mass of DAM (1: 1);
preferably, in the second mixed solution, the second solvent is added in an amount of 0.02g/mL to 0.2g/mL, based on the mass of the ZIF-8.
6. The method according to claim 3, wherein the rate of temperature increase in the thermal crosslinking is 0.25 ℃/min to 10 ℃/min.
7. The preparation method according to claim 3, wherein the drying is drying at 50-80 ℃ for 2-10 h;
preferably, the drying is at 100-120 deg.C for 12-24 h.
8. The production method according to claim 3, wherein the second mixed solution is produced by:
and (3) dispersing ZIF-8 in a second solvent, stirring for 1-2 h, and carrying out ultrasonic treatment at 100-120W for 10-20 min until particles are uniformly dispersed in the solvent to obtain a second mixed solution.
9. The method according to claim 3, wherein the step of preparing the mixed solution comprises:
and mixing and stirring the first mixed solution and the second mixed solution for 2-5 h, and carrying out ultrasonic treatment for 5-20 min to obtain a mixed solution.
10. The ZIF-8/6FDA-BI of claim 1 or 2: use of a DAM (1:1) hybrid membrane, wherein the ZIF-8/6 FDA-BI: DAM (1:1) hybrid membranes for separation of H2/CH4Mixed gas, CO2/CH4And (4) mixing the gases.
Technical Field
The invention relates to a separation membrane and a preparation method thereof, in particular to a separation membrane prepared from ZIF-8/6 FDA-BI: a DAM (1:1) hybrid membrane and a preparation method thereof belong to the technical field of gas separation.
Background
The membrane separation technology is an energy-saving gas separation technology, has the advantages of low energy consumption, low cost, high efficiency, small occupied area and the like, and becomes a research hotspot at present. Common gas separation membrane materials include polymer membranes, inorganic membranes, hybrid membranes, and the like. The hybrid membrane, also called as Mixed Matrix Membranes (MMMs), is a membrane material prepared based on inorganic materials/polymers, has the advantages of easy processing of polymer membranes, high stability of inorganic membranes and excellent separation performance, overcomes the problem that the permeability and the selectivity cannot be improved simultaneously, and is widely concerned by researchers. The commonly used dispersed phase comprises zeolite molecular sieve, carbon nano tube, mesoporous and non-porous nano material, metal organic framework material and the like. The metal organic framework Materials (MOFs) have the advantages of large specific surface area, porosity, adjustable pore channel structure, unsaturated metal sites and surface modification, so that the MOFs becomes an ideal dispersed phase for preparing the hybrid membrane.
To further optimize the separation performance of the hybrid membrane, the doping amount of the MOFs must be increased to maximize the possible performance of the unique molecular sieving characteristics of the MOFs. However, as filler content increases, the two-phase compatibility deteriorates, and the hybrid membrane is prone to problems of particle agglomeration, segment rigidification, phase interface defect structure, etc., so it is challenging to manufacture defect-free hybrid membranes with high loadings, typically no more than 30 wt.%. In order to improve the interface defect and improve the separation performance of the membrane material, the membrane material needs to be modified, and crosslinking is the simplest and most effective modification method.
CN105289337A discloses a crosslinkable polyimide gas separation membrane and a preparation method thereof. In particular to a preparation method of a crosslinkable polyimide gas separation membrane. Firstly, synthesizing a polyimide polymer, then performing functional modification on the polyimide polymer, coating the polyimide polymer with a film, and then performing chemical crosslinking at 120-220 ℃ for 24 hours in vacuum or inert atmosphere. Wherein CO is2/CH4After selective crosslinking, the maximum reaches 46 percent, which is improved by 64 percent compared with that before crosslinking. However, the method adopts vacuum or inert atmosphere for crosslinking and crosslinking for 24 hours, and has the disadvantages of complicated operation, high energy consumption and less selectivity improvement.
CN110433668A discloses a UiO-66-NH2A matrix membrane in situ cross-linked with PIM-1 and a preparation method thereof. By using UiO-66-NH2Is an inorganic filler, and PIM-1 is a polymer. MOF to PIM-1 in situ CrossCO associated with composite matrix membranes2The flux is increased by nearly one time, and CO2/CH4Selectivity to PIM-1 membrane of 12.3 and UiO-66-NH2The 12.0 of the/PIM-1 blend membrane is increased to 31.9. However, in the method, UIO-66 is copolymerized with a polymer monomer, and then a crosslinked film is obtained through post-treatment, the highest loading of MOFs in the work is 38%, the preparation process is complex, and H is not reported yet2/CH4The separation performance of (3).
Kertik, A., et al, (high selective gas separation membrane use-simple inorganic structures. energy Environ Sci,2017: p.10.1039. C.7EE01872J.) describes a novel amorphous ZIF-8 based mixed matrix membrane that can separate CO with high selectivity2/CH4And (3) mixing. In the work, Matrimid is used as a polymer phase, ZIF-8 is used as an inorganic filler to prepare a mixed matrix membrane, and then heat treatment is carried out in the air atmosphere. The binary gas mixture gas permeation result shows that the ZIF-8/Matrimid membrane with the doping amount of 40 wt.% is crosslinked for 24 hours at 250 ℃ and 350 ℃, and then CO is subjected to the test conditions of 10bar and 35 DEG C2The permeability is respectively 11.8 +/-1.3 and 4.9 +/-1.2 Barrer, CO2/CH4The selectivity reaches 52.6 +/-1.9 and 91.5 +/-12 respectively. Despite the CO of the membrane2/CH4The selectivity is obviously improved, and the CO of the membrane2The permeability is very low and cannot meet the requirements of industrial application.
CN101959577A discloses a high performance UV cross-linked polymer functionalized molecular sieve/polymer mixed matrix membrane. Porous molecular sieves are used as the dispersed filler and polymers as the continuous polymer matrix, which have no large cavities or only cavities smaller than a few angstroms at the interface of the polymer matrix and the molecular sieve. To CO2/CH4And H2/CH4The system exhibits significantly enhanced gas separation selectivity and permeability. However, the selected polymer has lower permeability and the selectivity of the mixed matrix membrane is improved less than that of a pure membrane.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a ZIF-8/6FDA-BI having a high MOFs loading and no defects at the interface, while having excellent gas separation performance: DAM (1:1) hybrid membranes and methods of making the same.
To achieve any of the above objects, the present invention provides a ZIF-8/6 FDA-BI: DAM (1:1) (4,4' - (hexafluoroisopropylidene) diphthalic anhydride-2- (4-aminophenyl) -5-aminobenzimidazole-2, 4, 6-trimethyl-1, 3-phenylenediamine) hybrid membrane, the ZIF-8/6 FDA-BI: DAM (1:1) hybrid membrane was prepared with polyimide 6FDA-BI: DAM (1:1) is used as a matrix, ZIF-8 is used as a filler, wherein the ZIF-8/6 FDA-BI: the total mass of the DAM (1:1) hybrid membrane is 100%, and the mass fraction of the filler ZIF-8 is 10-40 wt%. Wherein the ZIF-8/6 FDA-BI: the thickness of the DAM (1:1) hybrid membrane is 40 μm-70 μm.
The invention also provides the ZIF-8/6 FDA-BI: a method for preparing a DAM (1:1) hybrid membrane, wherein the method comprises the following steps:
the ratio of 6FDA-BI: dissolving DAM (1:1) in a first solvent to obtain a first mixed solution;
dispersing ZIF-8 in a second solvent to obtain a second mixed solution;
mixing the first mixed solution and the second mixed solution to obtain a mixed solution; wherein the first solution is added in an amount of 6FDA-BI: the mass fraction of ZIF-8 based on the mass of ZIF-8 in the second solution is 10-40% (preferably 10%, 20%, 30% or 40%) based on the mass of DAM (1: 1);
uniformly coating the mixed solution on a substrate, drying, separating a film from the substrate, soaking the film in anhydrous methanol for 12-24 h (preferably 12h), drying, and thermally crosslinking at 200-400 ℃ for 10-24 h to obtain ZIF-8/6 FDA-BI: DAM (1:1) thermally crosslinked hybrid membranes.
In the preparation method, ZIF-8/6 FDA-BI: when the DAM (1:1) hybrid membrane is thermally crosslinked, the ratio of 6FDA-BI: the methyl groups in DAM (1:1) are oxidized to form methylene groups providing crosslinking sites allowing ZIF-8/6 FDA-BI: the DAM (1:1) hybrid membrane is subjected to oxidative crosslinking, the interaction force of the polymer and ZIF-8 is enhanced, and the MOFs loading capacity and the performance of the hybrid membrane are larger and more excellent by the method. The invention is realized by mixing ZIF-8/6 FDA-BI: the DAM (1:1) hybrid membrane is thermally crosslinked to form a thermally crosslinked membrane with extremely high separation performance.
In one embodiment of the present invention, when preparing the first mixed solution and the second mixed solution, the same solvent is used for the first mixed solution solvent and the second mixed solution solvent, and N, N-Dimethylacetamide (DMAC) or N, N-Dimethylformamide (DMF) solvent can be used.
In one embodiment of the present invention, in the first mixed solution, the ratio of 6FDA-BI: the amount of the first solvent added is 0.05g/mL-0.1g/mL based on the mass of DAM (1: 1). In the second mixed solution, the amount of the second solvent added is 0.02g/mL-0.2g/mL, based on the mass of ZIF-8.
In one embodiment of the present invention, ZIF-8 is prepared according to the following steps:
70mL of a methanol solution containing 3.3g (40mmol) of 2-methylimidazole (molecular weight: 82.1) was added to 70mL of a methanol solution containing 1.5g (5mmol) of Zn (NO)3)2.6H2O (molecular weight: 297.4) in methanol was stirred at room temperature for 24 hours, and then centrifuged, and the resulting solid was washed with 50mL of methanol 3 times and finally dried in a vacuum oven at 80 ℃ for 12 hours to obtain white ZIF-8 powder.
In one embodiment of the present invention, the ratio of 6FDA-BI: DAM (1:1) was prepared according to the following procedure:
the molar ratio of 2,4, 6-trimethyl-1, 3-phenylenediamine (DAM) to 2- (4-aminophenyl) -5-aminobenzimidazole (BI) was 1: 1. High molecular weight polyamic acid (PAA) was first produced at low temperature (. about.5 ℃), DAM (1.5022g, 0.01mol) and BI (2.2426g, 0.01mol) with NMP (N-methylpyrrolidone) (50mL) were dissolved in a 100mL round bottom three-necked flask equipped with a stir bar and nitrogen purge. When DAM and BI were completely dissolved in NMP, 4' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA) (8.8848g, 0.02mol) was slowly added to the above mixed solution, and reacted at room temperature for 24 hours to prepare a high molecular weight polyamic acid solution.
The second step is imidization, i.e., ring closure by releasing water and producing chemically stable polyimides (6 FDA-BI: DAM (1: 1)). Acetic anhydride (18.9ml, 0.2mol) and 3-methylpyridine (1.94ml, 0.02mol) were sequentially injected into the above reaction mixture, and reacted for 24 hours to complete imidization of polyamic acid. Thus, a 6FDA-DAM polyimide solution was successfully synthesized. Finally, the resulting polyimide solution is precipitated and washed with methanol and then dried under vacuum at 100 ℃ to 120 ℃ for 12h to 24h to yield 6FDA-BI: DAM (1:1) polyimide.
In one embodiment of the present invention, the prepared 6FDA-BI: DAM (1:1) and ZIF-8 were dried at 120 ℃ and 80 ℃ respectively. This drying step may be performed in a vacuum oven.
In one embodiment of the present invention, the temperature increase rate of thermal crosslinking is 0.25 ℃/min to 10 ℃/min.
In one embodiment of the present invention, the drying is performed for 2h to 10h (preferably 5h) at 50 ℃ to 80 ℃ (preferably 60 ℃).
In one embodiment of the invention, the vacuum drying is carried out at 120 ℃ for 12 h.
In one embodiment of the present invention, the preparation of the second mixed solution comprises the following steps:
dispersing ZIF-8 in a second solvent, stirring for 1-2 h, and performing ultrasonic treatment at 100-120W for 10-20 min until the particles are uniformly dispersed in the solvent to obtain a second mixed solution.
In one embodiment of the present invention, the preparation of the mixed solution comprises the following steps:
mixing the first mixed solution and the second mixed solution, stirring for 2-5 h, and performing ultrasonic treatment for 5-20 min (preferably 10min) to obtain a mixed solution.
In one embodiment of the present invention, the coating substrate is a ceramic sheet substrate or a glass substrate. Thermal crosslinking on a substrate can overcome the problem of poor mechanical properties of the film.
ZIF-8/6FDA-BI of the present invention: DAM (1:1) hybrid membranes for separation of H2/CH4、CO2/CH4And (4) mixing the gases. Especially for the separation of H2/CH4Has outstanding separation performance.
The invention also provides a method for separating H2/CH4ZIF-8/6 FDA-BI: DAM (1:1) thermal-crosslinked hybrid membrane, which is prepared according to the above preparation method of the present invention. For example,the coating method comprises the following steps:
0.2g of 6FDA-BI is weighed: DAM (1:1) was dissolved in 1mL of N, N-Dimethylacetamide (DMAC) solvent. After standing and defoaming, the mixture was cast on a preheated glass plate, and the film thickness was controlled by a doctor blade (75 μm), and the casting was carried out in an oven at 60 ℃ for 5 hours. The thin film was removed from the glass substrate and immersed in anhydrous methanol for 24 hours to remove the residual solvent. The film was then dried in a vacuum oven at 120 ℃ for 12h to give 6FDA-BI: DAM (1:1) neat film;
and (3) preparing the prepared 6FDA-BI: drying DAM (1:1) pure membrane and ZIF-8 in vacuum drying oven at 120 deg.C and 80 deg.C respectively;
0.2g of dried 6FDA-BI: dissolving a DAM (1:1) pure membrane in 1mL of DMAC to obtain a polymer solution; dispersing ZIF-8 in DMAC, stirring for 1h, and carrying out ultrasonic treatment in a 120W ultrasonic instrument for 10min until particles are uniformly dispersed in the solution to obtain a ZIF-8 solution; adding the ZIF-8 solution to a polymer solution, mixing and sonicating to form a homogeneous liquid suspension; the mixture was poured onto a clean glass plate preheated to 50-80 ℃ and cast dry with a spatula in an oven at 60 ℃ for 5 h. Separating the film from the glass substrate and immersing the film in anhydrous methanol for 24 hours to remove the residual solvent; drying the film in a vacuum oven at 120 ℃ for 12 h; binding the film on a steel plate by using a copper wire, putting the steel plate into a tube furnace or a muffle furnace, and carrying out heat treatment for 10 hours at 200-400 ℃ in an air atmosphere to obtain ZIF-8/6 FDA-BI: DAM (1:1) thermally crosslinked hybrid membranes.
The ZIF-8/6FDA-BI prepared by the preparation method of the invention is: DAM (1:1) thermal cross-linking hybrid membrane has high MOFs loading amount, no defect on interface and excellent gas separation performance, especially on H2/CH4The mixed gas has higher separation performance.
ZIF-8/6FDA-BI of the present invention: the preparation method of the DAM (1:1) thermal crosslinking hybrid membrane is simple and easy to implement, the raw materials are easy to obtain, and the energy consumption is low.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited thereto.
The permeability of the membrane is tested by adopting a constant volume variable pressure device. Pure gas permeability of the polymer and hybrid membranes was performed at 35 ℃ and determined using the time-lag method by custom-designed constant volume/variable pressure devices. Testing of pure gas (H) at feed pressures of 5bar to 30bar2，N2，CH4，CO2) Before testing, a circular film sample was made, covered with aluminum tape, and then sealed with epoxy to prevent leakage. The masked membrane was mounted in a stainless steel gas permeation cell. The upstream and downstream are evacuated by introducing feed gas upstream of the permeate cell. The upstream and downstream pressures are recorded by pressure sensors. Leak testing was performed prior to gas permeability measurement, with leak rates less than 1 × 10-5torr/s. The volume ratio of 1: 1H2/CH4The mixture was tested for permeability of the mixed gas at 35 ℃. The downstream gas composition was analyzed by gas chromatography (Fuli GC9790 Plus). Before measuring gas permeability, the equipment is subjected to leakage detection test, and the leakage rate is less than 1 multiplied by 10- 5torr/s。
Comparative example 1
Weighing 0.022g of ZIF-8, dispersing in 1mL of N, N-Dimethylacetamide (DMAC), stirring for 1h, and ultrasonically treating in a 120W ultrasonic instrument for 10min until particles are uniformly dispersed in the solution; weighing 0.2g of 6FDA-DAM, dissolving 0.05g of 6FDA-DAM in 1mL of DMAC, mixing and stirring with a ZIF-8 solution for 2h after complete dissolution, and performing ultrasonic treatment for 10min to obtain a mixed solution; the remaining polymer 6FDA-DAM was added in two portions (0.05, 0.1g) to the above mixed solution, and the ultrasonic step was repeated twice each to form a uniform liquid suspension.
Casting the suspension on a preheated glass plate after defoaming, controlling the film thickness by a scraper (75 mu m), and casting for 5 hours in an oven at 60 ℃; removing the thin film from the glass substrate and immersing it in anhydrous methanol for 24 hours to remove residual solvent, and then drying the film in a vacuum oven at 120 ℃ for 12 hours to obtain 40 wt.% ZIF-8/6FDA-DAM hybrid film; binding 40 wt.% of ZIF-8/6FDA-DAM hybrid membrane on a steel plate by using a copper wire, putting the steel plate into a tube furnace or a muffle furnace, and carrying out heat treatment for 10h at 300 ℃ in an air atmosphere, wherein the heating rate of 25-285 ℃ is 10 ℃/min, and the heating rate of 285-300 ℃ is 0.25 ℃/min, so as to obtain 40 wt.% of ZIF-8/6FDA-DAM (1:1) thermal crosslinking hybrid membrane.
Carrying out gas separation performance test on the membrane; monocomponent H of the film2Has a permeability of 140.4Barrer, H2/CH4The selectivity was 34.3.
Comparative example 2
Weighing 0.086g of ZIF-8, dispersing in 1mL of N, N-Dimethylacetamide (DMAC), stirring for 1h, and carrying out ultrasonic treatment in a 120W ultrasonic instrument for 10min until the particles are uniformly dispersed in the solution; 0.2g of 6FDA-BI is weighed: dissolving 0.05g of DAM (1:1) in 1mL of DMAC (dimethylacetamide), mixing with a ZIF-8 solution after complete dissolution, stirring for 2h, and performing ultrasonic treatment for 10min to obtain a mixed solution; the remaining polymer 6FDA-BI: DAM (1:1) was added to the above mixed solution in two portions (0.05g, 0.1g), and the ultrasonic step was repeated twice each to form a uniform liquid suspension.
Casting the suspension on a preheated glass plate after defoaming, controlling the film thickness by a scraper (75 mu m), and casting for 5 hours in an oven at 60 ℃; removing the thin film from the glass substrate and immersing it in anhydrous methanol for 24 hours to remove the residual solvent; the membrane was then dried in a vacuum oven at 120 ℃ for 12h, yielding 30 wt.% ZIF-8/6 FDA-BI: DAM (1:1) hybrid membranes; 30 wt.% of ZIF-8/6 FDA-BI: binding the DAM (1:1) hybrid membrane on a steel plate, putting the steel plate into a tube furnace or a muffle furnace, carrying out heat treatment for 10h at 300 ℃ in an air atmosphere, wherein the heating rate of 25-285 ℃ is 10 ℃/min, and the heating rate of 285-300 ℃ is 0.25 ℃/min, so as to obtain 30 wt.% of ZIF-8/6 FDA-BI: DAM (1:1) thermally crosslinked hybrid membranes.
Carrying out gas separation performance test on the membrane; monocomponent H of the film2Has a permeability of 312.2Barrer, H2/CH4The selectivity was 79.6.
Comparative example 3
Weighing 0.133g of ZIF-8, dispersing in 1mL of N, N-Dimethylacetamide (DMAC), stirring for 1h, and carrying out ultrasonic treatment in a 120W ultrasonic instrument for 10min until the particles are uniformly dispersed in the solution; 0.2g of 6FDA-BI is weighed: dissolving 0.05g of DAM (1:1) in 1mL of DMAC (dimethylacetamide), mixing with a ZIF-8 solution after complete dissolution, stirring for 2h, and performing ultrasonic treatment for 10min to obtain a mixed solution; the remaining polymer 6FDA-BI: DAM (1:1) was added to the above mixed solution in two portions (0.05g, 0.1g), and the ultrasonic step was repeated twice each to form a uniform liquid suspension.
Casting the suspension on a preheated glass plate after defoaming, controlling the film thickness by a scraper (75 mu m), and casting for 5 hours in an oven at 60 ℃; removing the thin film from the glass substrate and immersing it in anhydrous methanol for 24 hours to remove the residual solvent; the membrane was then dried in a vacuum oven at 120 ℃ for 12h to give 40 wt.% uncrosslinked ZIF-8/6 FDA-BI: DAM (1:1) hybrid membranes.
Carrying out gas separation performance test on the membrane; monocomponent H of the film2Has a permeability of 715.0Barrer, H2/CH4The selectivity was 23.4.
Comparative example 4
Weighing 0.133g of ZIF-8, dispersing in 1mL of N, N-Dimethylacetamide (DMAC), stirring for 1h, and carrying out ultrasonic treatment in a 120W ultrasonic instrument for 10min until the particles are uniformly dispersed in the solution; 0.2g of 6FDA-BI is weighed: dissolving 0.05g of DAM (1:1) in 1mL of DMAC (dimethylacetamide), mixing with the ZIF-8 solution after complete dissolution, stirring for 2h, and performing ultrasonic treatment for 10min to obtain a mixed solution. The remaining polymer 6FDA-BI: DAM (1:1) was added to the above mixed solution in two portions (0.05g, 0.1g), and the ultrasonic step was repeated twice each to form a uniform liquid suspension.
Casting the suspension on a preheated glass plate after defoaming, controlling the film thickness by a scraper (75 mu m), and casting for 5 hours in an oven at 60 ℃; removing the thin film from the glass substrate and immersing it in anhydrous methanol for 24 hours to remove the residual solvent; the film was dried in a vacuum oven at 120 ℃ for 12h to give 40 wt.% ZIF-8/6 FDA-BI: DAM (1:1) hybrid membranes; 40 wt.% of ZIF-8/6 FDA-BI: the DAM (1:1) hybrid membrane is bound on a steel plate and placed into a tube furnace or a muffle furnace, and is subjected to heat treatment at 200 ℃ for 10h under an air atmosphere (the heating rate of the first stage is 10 ℃/min, and the heating rate of the second stage is 0.25 ℃/min), so that 40 wt% of ZIF-8/6FDA-BI subjected to heat treatment at 200 ℃ is obtained: DAM (1:1) hybrid membranes.
Carrying out gas separation performance test on the membrane; monocomponent H of the film2Has a permeability of 821.3Barrer, H2/CH4The selectivity was 57.1.
Example 1
This example provides a ZIF-8/6 FDA-BI: the preparation method of the DAM (1:1) thermal crosslinking hybrid membrane comprises the following steps:
ZIF-8 is prepared by the following steps:
70mL of a methanol solution containing 3.3g (40mmol) of 2-methylimidazole (molecular weight: 82.1) was added to 70mL of a methanol solution containing 1.5g (5mmol) of Zn (NO)3)2.6H2O (molecular weight: 297.4) in methanol was stirred at room temperature for 24 hours, and then centrifuged, and the resulting solid was washed with 50mL of methanol 3 times and finally dried in a vacuum oven at 80 ℃ for 12 hours to obtain white ZIF-8 powder.
6FDA-BI: DAM (1:1) was prepared according to the following procedure:
the molar ratio of DAM to BI is 1: 1; the synthesis was a two-step reaction, first producing high molecular weight polyamic acid (PAA) at low temperature (. about.5 ℃), DAM (1.5022g, 0.01mol) and BI (2.2426g, 0.01mol) were dissolved with NMP (N-methylpyrrolidinone) (50mL) in a 100mL round bottom three-necked flask equipped with a stir bar and nitrogen purge. When DAM and BI were completely dissolved in NMP, 6FDA (8.8848g, 0.02mol) was slowly added to the above mixed solution, and reacted at room temperature for 24 hours to prepare a high molecular weight polyamic acid solution.
The second step is imidization, i.e., by releasing water to close the ring and produce a chemically stable polyimide (6 FDA-BI: DAM (1: 1)); acetic anhydride (18.9ml, 0.2mol) and 3-methylpyridine (1.94ml, 0.02mol) are injected into the reaction mixture in sequence to react for 24 hours, and the imidization reaction of the polyamic acid is completed; thus, a 6FDA-DAM polyimide solution was successfully synthesized; finally, the resulting polyimide solution was precipitated and washed with methanol, and then dried under vacuum at 100 ℃ for 24 hours to give 6FDA-BI: DAM (1: 1).
0.133g of ZIF-8 was weighed out and dispersed in 1mL of N, N-Dimethylacetamide (DMAC), stirred for 1h, and sonicated in a 120W sonicator for 10min until the particles were uniformly dispersed in the solution. 0.2g of 6FDA-BI is weighed: dissolving 0.05g of DAM (1:1) in 1mL of DMAC (dimethylacetamide), mixing with the ZIF-8 solution after complete dissolution, stirring for 2h, and performing ultrasonic treatment for 3min to obtain a mixed solution. The remaining polymer 6FDA-BI: DAM (1:1) was added to the above mixed solution in two portions (0.05g, 0.1g), and the ultrasonic step was repeated twice each to form a uniform liquid suspension.
Casting the suspension on a preheated glass plate after defoaming, controlling the film thickness by a scraper (75 mu m), and casting for 5 hours in an oven at 60 ℃; removing the thin film from the glass substrate and immersing it in anhydrous methanol for 24 hours to remove the residual solvent; the film was dried in a vacuum oven at 120 ℃ for 12h to give 40 wt.% ZIF-8/6 FDA-BI: DAM (1:1) hybrid membranes; 40 wt.% of ZIF-8/6 FDA-BI: the DAM (1:1) hybrid membrane is bound on a steel plate and placed into a tube furnace or a muffle furnace, and heat treatment is carried out for 10h at 300 ℃ in an air atmosphere (the first temperature rise rate is 10 ℃/min, and the second temperature rise rate is 0.25 ℃/min), so that 40 wt.% of ZIF-8/6FDA-BI is obtained: DAM (1:1) thermally crosslinked hybrid membranes.
Carrying out gas separation performance test on the membrane; monocomponent H of the film2Has a permeability of 68.2Barrer, H2/CH4The selectivity was 150.3.
Table 1 shows H of comparative example and example2/CH4Comparison of gas permeability properties.
TABLE 1
H2Permeability (Barrer)
H2/CH4Selectivity is
Comparative example 1
140.4
34.3
Comparative example 2
312.2
79.6
Comparative example 3
715.0
23.4
Comparative example 4
821.3
57.1
Example 1
68.2
150.3
As can be seen from table 1: by changing the doping amount of the polymer and the ZIF-8, the crosslinking temperature and the data of a comparative non-thermal crosslinked membrane, the gas permeability of DAM/40% ZIF-8 is reduced after the heat treatment at 300 ℃ in the air for 10 hours, the selectivity is obviously improved, and the defects are repaired.
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