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CN-121988189-A - Ultrathin mixed matrix membrane with high ZIF-8 load capacity and preparation method and application thereof

CN121988189ACN 121988189 ACN121988189 ACN 121988189ACN-121988189-A

Abstract

The invention relates to the technical field of preparation of mixed matrix membranes and gas separation, in particular to an ultrathin mixed matrix membrane with high ZIF-8 loading capacity, and a preparation method and application thereof. The ultra-thin mixed matrix membrane with high ZIF-8 loading prepared by the method has the ZIF-8 loading amount of 84.3wt.% and the thickness of 160nm. And the existence of the inter-crystalline polymer cross-linked network not only enhances the compactness of the membrane and improves the solubility of the membrane to CO 2 , but also improves the gas sieving capability of ZIF-8 crystals. Therefore, the ultrathin mixed matrix membrane with high ZIF-8 loading capacity has excellent CO 2 permeation rate and higher CO 2 /N 2 separation selectivity in CO 2 /N 2 separation.

Inventors

  • GU ZHENJIE
  • LI PENG
  • SUN YUXIU
  • QIAO ZHIHUA
  • ZHONG CHONGLI

Assignees

  • 天津工业大学

Dates

Publication Date
20260508
Application Date
20260114

Claims (10)

  1. 1. A preparation method of an ultrathin mixed matrix membrane with high ZIF-8 loading is characterized by comprising the following steps: (1) Preparing HPAN a substrate, namely immersing a PAN support in NaOH aqueous solution, hydrolyzing for a certain time in a blast oven, and washing with deionized water until the pH value reaches neutrality to obtain a HPAN substrate; (2) HPAN-Zn 2+ substrate is prepared by removing water on the surface of PAN support, immersing the surface in hexahydrate zinc nitrate aqueous solution, pouring out redundant solution after a certain time, taking out membrane, fully cleaning and replacing with deionized water and methanol solution to obtain HPAN-Zn 2+ substrate, and storing in methanol solution; (3) MMMs preparation: Preparing zinc nitrate hexahydrate methanol solution, preparing Hmim/PEI methanol solution, separating the zinc nitrate hexahydrate methanol solution and the Hmim/PEI methanol solution by utilizing a HPAN-Zn 2+ substrate, keeping the modified side of the HPAN-Zn 2+ substrate towards the zinc nitrate hexahydrate methanol solution and the reverse side of the HPAN-Zn 2+ substrate towards the Hmim/PEI methanol solution, reacting, taking out the prepared film, soaking the film with methanol, washing the film, and drying the film in a constant temperature and humidity box to obtain the mixed matrix film.
  2. 2. The method of preparing an ultra-thin mixed matrix membrane with high ZIF-8 loading according to claim 1, wherein in step (1), the PAN support is an ultrafiltration membrane with a molecular weight cut-off of 40-50 kDa.
  3. 3. The method for preparing an ultra-thin mixed matrix membrane with high ZIF-8 loading according to claim 1, wherein in the step (1), the concentration of NaOH aqueous solution is 2.0 mol/L, the temperature of the air oven is 65 ℃ and the hydrolysis time is 1h.
  4. 4. The method of preparing an ultra-thin mixed matrix membrane with high ZIF-8 loading according to claim 1, wherein in step (2), the concentration of the aqueous solution of zinc nitrate hexahydrate is 3wt.%, the immersion time is 0.5h, and the deionized water and methanol are washed and replaced no less than 3 times.
  5. 5. The method for preparing an ultrathin mixed matrix film with high ZIF-8 loading according to claim 1, wherein in the step (3), the molar ratio of Hmim to Zn 2+ is (8-32): 1, and the reaction time is 1-30min.
  6. 6. The method of preparing an ultra-thin mixed matrix membrane with high ZIF-8 loading according to claim 1, wherein in step (3), the concentration of PEI in Hmim/PEI methanol solution is 0.1wt.% to 1wt.%.
  7. 7. The method for preparing an ultrathin mixed matrix membrane with high ZIF-8 loading, as claimed in claim 1, wherein in the step (3), the reaction condition is 30-40 ℃ and the humidity is 40%, the methanol soaking time is 30min, and the drying condition of the obtained membrane in a constant temperature and humidity box is 30 ℃ and the humidity is 40% and is not lower than 12h.
  8. 8. A mixed matrix membrane prepared by the method of claim 1-7, wherein the mixed matrix membrane has a ZIF-8 loading of 74.4wt.% to 96.8wt.%.
  9. 9. The mixed matrix membrane of claim 8, wherein the thickness of the mixed matrix membrane is 138-228nm.
  10. 10. Use of an ultra-thin mixed matrix membrane with high ZIF-8 loading prepared by the preparation method of any one of claims 1-7 in CO 2 /N 2 separation.

Description

Ultrathin mixed matrix membrane with high ZIF-8 load capacity and preparation method and application thereof Technical Field The invention belongs to the technical field of preparation of mixed matrix membranes and gas separation, and particularly relates to an ultrathin mixed matrix membrane with high ZIF-8 loading capacity, and a preparation method and application thereof. Background The efficient separation of CO 2 and N 2 is a key link for realizing clean utilization of fossil fuel and Carbon Capture and Sequestration (CCS), and has important strategic significance for relieving climate change and maintaining energy safety. Compared with the traditional separation technologies such as absorption and adsorption, the membrane separation technology has received a great deal of attention because of the advantages of low energy consumption, simple and convenient operation, environmental friendliness and the like. Among them, the mixed matrix membrane (MMMs hereinafter) is one of ideal ways to realize high-performance gas separation by dispersing porous filler in polymer matrix, which is expected to break through the upper limit of the selectivity-permeability of the traditional polymer membrane. Among the fillers, ZIF-8, which is a member of metal-organic framework materials (MOFs for short), has wide application prospect in improving the separation performance of CO 2/N2 due to the adaptive screening pore diameter (0.34 nm) and good affinity of CO 2. To fully integrate the easy processability of the polymer matrix with the excellent gas sieving characteristics of ZIF-8, developing MMMs for high filler loadings is critical to effectively improve separation performance. However, for high filler loadings MMMs, conventional preparation strategies still rely on a multi-step procedure-typically requiring separate synthesis of the MOF particles prior to their dispersion in the polymer solution for subsequent processing. Besides the complex process flow, this method is very prone to cause secondary agglomeration of particles during the mixing, casting and drying stages, thus impeding the formation of a structurally complete, excellent mixed matrix film. And this problem is particularly pronounced when the film thickness is significantly reduced to the ultra-thin range (< 300 nm a). Therefore, developing a ultrathin MMMs preparation technology compatible with high ZIF-8 loading capacity and without defects has important significance for promoting the industrial application of the CO 2/N2 separation membrane. Disclosure of Invention In order to increase the loading amount of ZIF-8 in MMMs and prepare ultrathin MMMs and fully improve the gas separation performance, the application provides an ultrathin mixed matrix membrane with high ZIF-8 loading amount, and a preparation method and application thereof. The method comprises the steps of firstly hydrolyzing a Polyacrylonitrile (PAN) substrate by using a sodium hydroxide (NaOH) aqueous solution to obtain HPAN, and then immersing the HPAN substrate surface into a zinc nitrate hexahydrate aqueous solution to obtain a Zn 2+ modified HPAN substrate (HPAN-Zn 2+). Finally, zinc nitrate hexahydrate methanol solution and 2-methylimidazole (hereinafter abbreviated as Hmim)/polyethyleneimine (hereinafter abbreviated as PEI) methanol solution are introduced into two sides of the membrane, and an anti-diffusion method is utilized to gradually grow in situ to prepare the ultrathin MMMs with high ZIF-8 loading capacity. In the technical scheme, hmim ligand diffuses preferentially to HPAN-Zn 2+ surface and Zn 2+ to form ZIF-8 crystal as MMMs main body phase. Subsequently, PEI participates in the formation of ZIF-8 films by diffusion. Wherein, PEI and Zn 2+ form a nano cross-linked network, which can effectively make up the inter-crystal defect of ZIF-8 and improve the compactness of the film. The process imparts a ZIF-8 loading of MMMs up to 74wt.% to 97 wt.%. In addition, PEI effectively reduces the crystal size of ZIF-8 by accelerating the crystallization reaction rate of ZIF-8 and inhibiting the Oswald ripening mechanism of the PEI in the growth process. The self-limiting effect of the back diffusion method is combined to obtain MMMs with ultra-thin thickness. In the CO 2/N2 separation process, the existence of the PEI-Zn 2+ cross-linked network improves the CO 2 solubility of the membrane, rigidifies the framework structure of the ZIF-8 and improves the gas separation capability of the ZIF-8. Thus, the resulting MMMs exhibited excellent CO 2 permeation rate and higher CO 2/N2 selectivity during CO 2/N2 separation. The invention is realized by the following technical scheme: a preparation method and application of an ultrathin mixed matrix membrane with high ZIF-8 loading capacity are provided, and the preparation method comprises the following steps: (1) And HPAN, preparing the substrate, namely immersing the PAN support body in a NaOH aqueous solution, hydrolyzing for a certain