CN115282782A - A kind of total heat exchange membrane doped with functionalized ZIF-7 nanoparticles and preparation method thereof - Google Patents

Abstract

The invention discloses a full heat exchange membrane doped with functionalized ZIF-7 nanoparticles, comprising an ultrafiltration membrane support layer, a polyamide separation layer and functionalized ZIF-7 nanoparticles; the polyamide separation layer is distributed in The surface and holes of the ultrafiltration membrane support layer; the functionalized ZIF-7 nanoparticles are distributed in the polyamide separation layer. The present invention realizes the functionalization of the ZIF-7 nanoparticles by regulating the ligand structure of the ZIF-7 nanoparticles, and successfully adds the functionalized ZIF-7 particles during the interface polymerization process. The doping of functionalized ZIFs nanoparticles in the polyamide separation layer is realized, which can effectively control the interphase interaction force, avoid interfacial voids, and accurately build a fast transport and selective "microscopic channel", while increasing the mechanical properties of the membrane and increasing the surface of the membrane. Roughness, increasing the surface area of the separation layer, thereby improving moisture permeability, gas barrier and heat recovery efficiency.

Description

A total heat exchange membrane mixed with functionalized ZIF-7 nanoparticles and its preparation method

technical field

The invention belongs to the field of moisture permeability barrier and heat recovery, and in particular relates to a total heat exchange membrane mixed with functionalized ZIF-7 nanoparticles and a preparation method thereof.

Background technique

Nearly one-third of my country's electricity consumption is used in residential buildings and shopping malls, and nearly half of it is used in air conditioning. In addition, people spend more than 80% of their time indoors, so ventilation is extremely important during the frequent use of air conditioners. From the perspective of saving energy, protecting the environment and health, the ventilation system using the principle of total heat exchange energy saving plays an important role in maintaining human health and energy saving. While using outdoor fresh air to exchange indoor polluted air (such as carbon dioxide, formaldehyde and other harmful gases) to improve indoor air quality, in order to reduce the energy required to adjust the temperature of fresh air, scientists designed a total heat exchanger as an energy-saving fresh air system. Core equipment to enable energy recovery between outdoor fresh air and indoor polluted air. With the rapid development of membrane technology, the total heat exchanger with membrane as the heat recovery medium can achieve good energy recovery and gas (such as CO ₂ ) under the premise of ensuring the ventilation effect under the modification of ZIF nanoparticles. Barrier effect.

The total heat exchanger uses the total heat exchange membrane as a medium to obtain high-efficiency recovery through sensible heat exchange and latent heat exchange. Sensible heat exchange has no mass transfer process, and only the fresh air and exhaust air pass through energy transfer, resulting in temperature changes; while latent heat exchange is the exchange of water vapor mass between fresh air and exhaust air, thereby adjusting the concentration of water vapor in the air, causing The increase or decrease of the latent heat of water vapor achieves the purpose of energy saving. Due to the high latent heat of vaporization of water vapor in the air, the proportion of energy in humid air is relatively large. Therefore, the latent heat contribution rate of total heat exchange between indoor and outdoor air is far greater than the sensible heat contribution rate. Therefore, in order to improve the energy recovery rate of the total heat exchanger and ensure the fresh air in the closed space, improving the moisture permeability and gas barrier performance of the total heat exchange membrane is an important research direction.

For now, most of the total heat exchange membranes, the core components of total heat exchange equipment, use commercial paper membranes. This membrane has the following disadvantages: 1. The paper membrane is a fully permeable membrane, which cannot effectively block _CO2 gas. At the same time, the mechanical Poor performance; 2. The paper film is not flame retardant, and it is easy to mold during use, causing secondary pollution to the air; 3. There is a "trade-off" between moisture permeability and gas barrier properties. The composite polyamide total heat exchange membrane constructed by interfacial polymerization has boundary defects and different degrees of gas leakage. Previous attempts to add nanoparticles such as montmorillonite, silica, and ZIF-7 to the membrane to improve the moisture permeability of the membrane by improving the hydrophilicity of the membrane or constructing selective "microscopic channels" in the membrane, however, Due to the agglomeration of nanoparticles, interfacial voids will appear in the film, and gas leakage will occur, resulting in a decrease in the gas barrier performance of the film. In order to obtain a total heat exchange membrane with ultra-high gas barrier, it is necessary to find a reasonable treatment method on the basis of ensuring the heat exchange efficiency.

Contents of the invention

In order to overcome the shortcomings of the existing total heat exchange membrane, the invention provides a total heat exchange membrane mixed with functional ZIF-7 nano particles and a preparation method thereof. The total heat exchange membrane of the invention is composed of an ultrafiltration membrane support layer, a polyamide separation layer and functionalized ZIF-7 nanoparticles distributed in the polyamide layer. The preparation process is as follows: adding functionalized ZIF-7 nanometer particles into the oil phase, and forming a polyamide ultra-thin separation layer added with functionalized ZIF-7 nanometer particles by means of interfacial polymerization. Functionalized ZIF-7 nanoparticles can effectively regulate the phase-interface interaction force, avoid interfacial voids, increase the compactness of the film, precisely construct a fast transport selective "microscopic channel", and increase the mechanical properties and flame retardancy of the film. The surface roughness of the membrane increases the surface area of the separation layer, thereby improving moisture permeability, gas barrier and heat recovery efficiency. The total heat exchange membrane prepared by the present invention has the characteristics of high moisture permeability, high gas barrier and high heat recovery efficiency, and the preparation method is simple, feasible and easy to operate, and can be applied to air energy recovery, indoor air purification, fresh air system and chemical environmental protection fields. It has a good industrial application prospect.

Technical scheme of the present invention is as follows:

A total heat exchange membrane mixed with functional ZIF-7 nanoparticles, comprising: an ultrafiltration membrane support layer, a polyamide separation layer, and functionalized ZIF-7 nanoparticles distributed in the polyamide layer;

The support layer of the ultrafiltration membrane can be prepared from one or more of polysulfone, polyethersulfone, polyetherketone, polyarylsulfone, polyacrylonitrile, and polyvinylidene fluoride;

The ultrafiltration membrane contains holes with a diameter of 1 nm to 0.2 μm, a small part of the polyamide is located in the holes of the ultrafiltration membrane, and most of them are located on the surface of one side of the ultrafiltration membrane.

The polyamide separation layer is prepared by interfacial polymerization of water-phase amine monomers and oil-phase acid chloride monomers;

The functionalized ZIF-7 nanoparticles include but not limited to ZIF-7-NH ₂ , ZIF-7-OH, ZIF-7-CH ₃ , ZIF-7-CH ₂ OH, ZIF-7-C ₂ H ₅ , A combination of one or more functionalized ZIF-7 nanoparticles such as ZIF-7-C ₃ H ₇ ; the particle diameter of the functionalized ZIF-7 nanoparticles is 20-500nm.

A preparation method of a total heat exchange membrane mixed with functional ZIF-7 nanoparticles, the preparation method is:

(1) Synthesis of functionalized ZIF-7 nanoparticles

Mix the metal precursor solution and the ligand solution, stir and react at room temperature (20-30°C) for 0.5-12h, then centrifuge to collect nano-sized solid particles, wash (with methanol), and vacuum-dry (50-120°C, 6- 12h), obtain functionalized ZIF-7 nanoparticles;

The concentration of the metal precursor solution is 0.01-1mol/L, the solvent is DMF (N,N-2 methylformamide), and the metal precursor is selected from zinc oxide, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate one or more of these;

The concentration of the ligand solution is 0.01～1mol/L, the solvent is methanol, and the ligand is a mixture of benzimidazole and benzimidazole containing functional groups; the benzimidazole containing functional groups is selected from 2- Aminobenzimidazole, 2-hydroxybenzimidazole, 2-methylbenzimidazole, 2-hydroxymethylbenzimidazole, 2-ethylbenzimidazole, 2-propylbenzimidazole and other benzimidazoles one or more;

The volume ratio of the metal precursor solution to the ligand solution is 1:1;

(2) Preparation of membrane solution

At room temperature, dissolve the amine monomer in deionized water to make an aqueous phase solution, dissolve the acid chloride monomer in an organic solvent and add the functionalized ZIF-7 nanoparticles obtained in step (1), and disperse uniformly by ultrasonic to obtain an oil phase solution ,spare;

In the aqueous phase solution, the mass fraction of amine monomers is 0.01-5% (preferably 1-3%), and amine monomers include but not limited to piperazine, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine Diamine, ethylenediamine, hexamethylenediamine, 1,4-butanediamine, 4,4-diaminodiphenyl ether, 4,4,-diaminodiphenylmethane, o-benzidine, 1,2- Propylenediamine, 1,3-propylenediamine, 2,4-diaminotoluene, 1,2-cyclohexanediamine, 4,5-dichloro-o-phenylenediamine, diethylenetriamine, s-benzenetriamine and one or more of its derivatives;

In the oil phase solution, the mass fraction of the acid chloride monomer is 0.01 to 5% (preferably 0.1 to 0.5%), and the mass fraction of the functionalized ZIF-7 nanoparticles is 0.001 to 5% (preferably 0.03 to 1%). The solvent is selected from one or more of alkanes such as n-hexane, n-heptane, n-octane, n-dodecane, isododecane, and isohexadecane, and the acid chloride monomer includes but not limited to isophthalo One or more of acid chloride, terephthaloyl chloride, phthaloyl chloride, trimesoyl chloride, polyaromatic sulfonyl chloride and its derivatives;

(3) Preparation of polyamide layer by interfacial polymerization

At room temperature, first immerse the support layer of the ultrafiltration membrane in the water phase solution for 1-10 minutes (preferably 2-5 minutes), then remove the excess water phase solution on the surface of the membrane, and then immerse the support layer of the ultrafiltration membrane in the oil phase solution Interfacial polymerization reaction takes place in 20s～10min (preferably 30s～2min), then take out and dry in the air, form the polyamide layer that adds functionalized ZIF-7 nanoparticles on the surface of the ultrafiltration membrane support layer;

(4) post-processing

The membrane is heat-treated at 50-90°C (preferably 60-80°C) for 5-30min (preferably 8-20min) to obtain a total heat exchange membrane doped with functional ZIF-7 nanoparticles.

The type of the total heat exchange membrane mixed with the functional ZIF-7 nanoparticles prepared in the invention includes a flat membrane, a hollow fiber homogeneous membrane or a hollow composite membrane and a tubular membrane.

The beneficial effects of the present invention are:

By adjusting the ligand structure of ZIF-7 nanoparticles, the functionalization of ZIF-7 nanoparticles was realized, and the functionalized ZIF-7 particles were successfully added in the interfacial polymerization process. Realized the doping of functionalized ZIFs nanoparticles in the polyamide separation layer, which can effectively control the phase-interface interaction force, avoid interfacial voids, accurately construct a fast transport selective "microscopic channel", and at the same time increase the mechanical properties of the membrane and increase the surface area of the membrane. Roughness, which increases the surface area of the separation layer, thereby improving moisture permeability, gas barrier and heat recovery efficiency.

Functionalized ZIF-7 nanoparticles interact with polyamide (PA) membranes by forming hydrogen bonds or coordinate bonds, thereby increasing the binding affinity without introducing severe defects, so ZIFs nanoparticles can be immobilized in the polyamide layer and On the surface, the rapid transport selective "microscopic channel" is precisely constructed; at the same time, nanoparticles can be fine-tuned through surface functionalization, crystal size and morphology control to achieve high moisture permeability and high gas barrier properties.

The total heat exchange membrane mixed with functional ZIF-7 nanoparticles of the present invention has higher moisture permeability, gas barrier and heat recovery than the total heat exchange membrane prepared by adding unfunctionalized ZIFs nanoparticles performance, and the preparation method is simple, feasible, and easy to operate. It is suitable for air total heat recovery, air conditioning HVAC energy recovery, indoor air purification, air dehumidification and heat moisture recovery, and chemical and environmental protection fields.

Description of drawings

Figure 1 is a flow chart of the preparation process of the total heat exchange membrane mixed with functionalized ZIF-7 nanoparticles.

Fig. 2 is the electron micrograph of the polyamide separation layer prepared by (a) comparative example 1, (b) embodiment 3, (c) embodiment 5 and (d) embodiment 6;

Figure 3 is the infrared image of ZIF-7 nanoparticles and functionalized ZIF-7 nanoparticles.

Fig. 4 is the performance test diagram of the blank total heat exchange membrane of comparative example 1, the total heat exchange membrane of comparative example 2 mixed with unfunctionalized ZIF-7 nanoparticles and the total heat exchange membrane prepared in Examples 1-6 , where (a) is the water vapor and CO ₂ permeation diagram, and (b) is the total heat exchange efficiency data diagram.

Detailed ways

The present invention is further described below through specific examples, but the protection scope of the present invention is not limited thereto.

The indoor environment for the preparation of all total heat exchange membranes in the examples is as follows: the temperature is 25° C., the humidity is 45%, and normal pressure.

The polysulfone ultrafiltration membrane support layer used in the examples was purchased from Hangzhou Water Treatment Center.

Example 1:

Preparation of total heat exchange membranes doped with functional ZIF-7 nanoparticles. The concrete steps of its preparation method are as follows:

(1) Dissolve 5mmol Zn(NO ₃ ) ₂ ·6H ₂ O in 50ml DMF to make Zn ²⁺ solution; dissolve 5mmol benzimidazole and 5mmol 2-aminobenzimidazole in 50ml methanol to make imidazole solution; The imidazole solution was quickly poured into the Zn ²⁺ solution at room temperature and stirred for 6 hours to obtain a milky white ZIF-7-NH ₂ dispersion. The obtained nano-sized ZIF-7-NH ₂ particles were collected by high-speed centrifugation, washed with methanol to obtain pure ZIF-7-NH ₂ , and dried in vacuum at 120°C for 12 hours to obtain solid powder ZIF-7-NH ₂ ;

(2) earlier the ultrafiltration membrane supporting layer is immersed in 2wt% MPD (m-phenylenediamine) solution 3min, forms the water phase liquid layer on its surface, after taking out, dry the excess water phase solution on the membrane surface, then ultrafiltration The support layer of the filter membrane is immersed in 0.1wt% TMC (trimesoyl chloride) and 0.05wt% ZIF-7-NH ₂ n-hexane solution for 1min, interfacial polymerization reaction occurs, take it out and dry it in the air, and then heat-treat at 70°C 15 minutes, drying to obtain a total heat exchange membrane mixed with amino-functionalized ZIF-7 nanomaterials.

The water vapor permeability, _CO2 permeability and enthalpy exchange efficiency of the total heat exchange membrane prepared in Example 1 mixed with amino functionalized ZIF-7 nanoparticles are shown in Figure 4, the water vapor permeability is 571.71GPU, and the _CO2 permeability is 16.72GPU, wet exchange 43.76%, enthalpy exchange efficiency 62.73%, heat exchange 96.08%.

Example 2:

The rest of embodiment 2 is the same as the method of embodiment 1, except that the 5mmol 2-aminobenzimidazole in step (1) of embodiment 1 is replaced with 5mmol 2-hydroxybenzimidazole;

The water vapor permeability, _CO permeability and enthalpy exchange efficiency of a functionalized ZIF-7 nanomaterial modified total heat exchange membrane prepared in Example 2 are shown in Figure 4, the water vapor permeability is 580.24GPU, and the _CO permeability The rate is 27.93GPU, the wet exchange is 44.83%, the enthalpy exchange efficiency is 63.51%, and the heat exchange is 96.91%.

Example 3:

The rest of embodiment 3 is the same as the method of embodiment 1, except that the 5mmol benzimidazole in step (1) of embodiment 1 is replaced with 5mmol 2-methylbenzimidazole;

The total heat exchange membrane water vapor permeability, _CO2 permeability, and enthalpy exchange efficiency of a functionalized ZIF-7 nanomaterial modified total heat exchange membrane prepared in Example 3 are shown in Figure 4. The water vapor permeability is 614.61GPU, and the _CO2 permeation rate The rate is 34.09GPU, the wet exchange is 45.59%, the enthalpy exchange efficiency is 63.03%, and the heat exchange is 96.88%.

Example 4:

The rest of embodiment 4 is the same as the method of embodiment 1, except that the 5mmol benzimidazole in step (1) of embodiment 1 is replaced with 5mmol 2-hydroxymethylbenzimidazole;

The water vapor permeability, _CO2 permeability and enthalpy exchange efficiency of a functionalized ZIF-7 nanomaterial modified total heat exchange membrane prepared in Example 4 are shown in Figure 4, the water vapor permeability is 587.63GPU, and the _CO2 permeation The rate is 21.46GPU, the wet exchange is 43.64%, the enthalpy exchange efficiency is 61.97%, and the heat exchange is 96.08%.

Example 5:

The rest of Example 5 is the same as the method of Example 1, except that the 5mmol benzimidazole in the step (1) of Example 1 is replaced with 5mmol 2-ethylbenzimidazole;

The water vapor permeability, _CO2 permeability and enthalpy exchange efficiency of a functionalized ZIF-7 nanomaterial modified total heat exchange membrane prepared in Example 5 are shown in Figure 4, the water vapor permeability is 623.06GPU, and the _CO2 permeation The rate is 27.86GPU, the wet exchange is 46.19%, the enthalpy exchange efficiency is 63.73%, and the heat exchange is 96.77%.

Embodiment 6:

The rest of embodiment 6 is the same as the method of embodiment 1, except that the 5mmol benzimidazole in step (1) of embodiment 1 is replaced with 5mmol 2-propylbenzimidazole;

The water vapor permeability, _CO2 permeability and enthalpy exchange efficiency of a functionalized ZIF-7 nanomaterial modified total heat exchange membrane prepared in Example 6 are shown in Figure 4, the water vapor permeability is 624.65GPU, and the _CO2 permeation The rate is 20.42GPU, the wet exchange is 45.88%, the enthalpy exchange efficiency is 62.42%, and the heat exchange is 96.75%.

The polyamide separation layer that embodiment 3,5,6 makes is as shown in Figure 2 (b) (c) (d), can see obvious functionalized ZIFs nanoparticles on the polyamide layer, and the particle size of particle is in 30-200nm.

Comparative example 1:

Step (1): first immerse the support layer of the ultrafiltration membrane in 2wt% MPD solution for 3 minutes to form an aqueous phase liquid layer on its surface, and remove the excess aqueous phase solution on the surface of the membrane after taking it out;

Step (2): Submerge the support layer of the ultrafiltration membrane in 0.1wt% TMC n-hexane solution for 1 minute, interfacial polymerization reaction occurs, take it out and dry it in the air, then heat treat it at 70°C for 10 minutes, and dry it to obtain a blank total heat exchange membrane.

Fig. 2(a) is an electron microscope image of the polyamide separation layer prepared in Comparative Example 1, in which only the polyamide layer without nanoparticles can be seen.

The water vapor permeability, _CO2 permeability and enthalpy exchange efficiency of a total heat exchange membrane prepared in Comparative Example 1 without adding ZIFs nanoparticles are shown in Figure 4, the water vapor permeability is 586.07GPU, and the _CO2 permeability is 152.59GPU , Humidity exchange 40.35%, enthalpy exchange efficiency 60.83%, heat exchange 95.15%.

Comparative example 2:

The method of comparative example 2 is the same as that of Example 1, except that 5mmol benzimidazole and 5mmol 2-aminobenzimidazole in step (1) of embodiment 1 are replaced with 10mmol benzimidazole;

The water vapor permeability of the total heat exchange membrane mixed with unfunctionalized ZIF-7 nanoparticles prepared in Comparative Example ₂ , CO The permeability and enthalpy exchange efficiency are shown in Figure 4, the water vapor permeability is 589.05GPU, and the _CO permeation The rate is 77.49GPU, the wet exchange is 42.76%, the enthalpy exchange efficiency is 61.91%, and the heat exchange is 95.99%.

_CO permeability test conditions for all examples and comparative examples: temperature 25°C, tested by differential pressure method; test conditions for enthalpy exchange efficiency: fresh air temperature 35°C, RH40%; exhaust air temperature 25°C, RH25%.

In the total heat exchange membrane mixed with functionalized ZIF-7 nanoparticles according to the present invention, the functionalized ZIF-7 nanoparticles are added to the oil phase, and the polyamide mixed with functionalized ZIF-7 nanoparticles is formed by interfacial polymerization The ultra-thin skin layer ensures high moisture permeability, high gas barrier and high heat recovery efficiency. Compared with the comparative example, it not only has an extremely low CO ₂ gas transmission rate (10-40GPU), but also maintains the same enthalpy exchange efficiency (60-65 %). At the same time, the preparation method is simple, feasible, easy to operate and low in cost, and is applicable to air energy recovery, gas separation, indoor fresh air system and chemical environmental protection fields.

The present invention is not limited to the above-mentioned embodiments, as long as the requirements of the present invention are met, they all belong to the protection scope of the present invention.

Claims (10)

1. A total heat exchange membrane doped with functionalized ZIF-7 nano particles is characterized by comprising an ultrafiltration membrane supporting layer, a polyamide separation layer and functionalized ZIF-7 nano particles;

the polyamide separation layer is distributed on the surface and in the holes of the ultrafiltration membrane support layer;

the functionalized ZIF-7 nanoparticles are distributed in the polyamide separation layer.

2. The PEM incorporating the functionalized ZIF-7 nanoparticles of claim 1, wherein the ultrafiltration membrane support layer is made of one or more of polysulfone, polyethersulfone, polyetherketone, polyarylsulfone, polyacrylonitrile, and polyvinylidene fluoride.

3. The pem of claim 1 incorporating functionalized ZIF-7 nanoparticles wherein said functionalized ZIF-7 nanoparticles comprise ZIF-7-NH ₂ 、ZIF-7-OH、ZIF-7-CH ₃ 、ZIF-7-CH ₂ OH、ZIF-7-C ₂ H ₅ 、ZIF-7-C ₃ H ₇ One or more of them, the particle size is 20-500 nm.

4. The enthalpy exchange membrane doped with functionalized ZIF-7 nanoparticles, according to claim 1, wherein the type of the enthalpy exchange membrane is a flat sheet membrane, a hollow fiber homogeneous membrane, or a hollow composite membrane and a tubular membrane.

5. The method of preparing a total heat exchange membrane incorporating functionalized ZIF-7 nanoparticles as claimed in claim 1, comprising the steps of:

(1) Synthesis of functionalized ZIF-7 nanoparticles

Mixing a metal precursor solution and a ligand solution, stirring and reacting at room temperature, then centrifugally collecting nano-scale solid particles, cleaning with methanol, and drying in vacuum to obtain functionalized ZIF-7 nanoparticles;

(2) Preparation of film-forming solution

Dissolving amine monomers in deionized water at room temperature to prepare a water phase solution, dissolving acyl chloride monomers in an organic solvent, adding the functionalized ZIF-7 nanoparticles obtained in the step (1), and uniformly dispersing by ultrasonic to obtain an oil phase solution for later use;

(3) Preparation of polyamide layer by interfacial polymerization

Immersing an ultrafiltration membrane supporting layer in an aqueous phase solution for 1-10 min at room temperature, taking out, removing the excessive aqueous phase solution on the surface of the membrane, immersing the ultrafiltration membrane supporting layer in an oil phase solution for 20 s-10 min to generate an interfacial polymerization reaction, taking out, airing in the air, and forming a polyamide layer containing functionalized ZIF-7 nano particles on the surface of the ultrafiltration membrane supporting layer to obtain a composite membrane;

(4) Post-treatment

And (4) carrying out heat treatment on the composite membrane obtained in the step (3) at 50-90 ℃ for 5-30 min to obtain the full heat exchange membrane doped with the functional ZIF-7 nano particles.

6. The method of preparing a total heat exchange membrane incorporating functionalized ZIF-7 nanoparticles, according to claim 5, wherein in step (1), the volume ratio of the metal precursor solution to the ligand solution is 1:1, stirring for 0.5 to 12 hours at the temperature of between 20 and 30 ℃ under the condition of stirring reaction; the vacuum drying conditions were: drying for 6-12 h at 50-120 ℃.

7. The method of preparing the enthalpy exchange membrane doped with the functionalized ZIF-7 nanoparticles according to claim 5, wherein in the step (1):

the concentration of the metal precursor solution is 0.01-1 mol/L, the solvent is N, N-2 methyl formamide DMF, and the metal precursor is selected from one or more of zinc oxide, zinc nitrate, zinc chloride, zinc sulfate and zinc acetate;

the concentration of the ligand solution is 0.01-1 mol/L, the solvent is methanol, the ligand is a mixture of benzimidazole and benzimidazole containing functional groups, and the benzimidazole containing the functional groups is selected from one or more of 2-aminobenzimidazole, 2-hydroxybenzimidazole, 2-methylbenzimidazole, 2-hydroxymethylbenzimidazole, 2-ethylbenzimidazole and 2-propylbenzimidazole.

8. The method of preparing a total heat exchange membrane doped with functionalized ZIF-7 nanoparticles as claimed in claim 5, wherein in the step (2):

in the aqueous phase solution, the mass fraction of amine monomers is 0.01-5%, the amine monomers comprise but are not limited to one or more of piperazine, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, ethylenediamine, hexanediamine, 1,4-butanediamine, 4,4-diaminodiphenyl ether, 4,4, -diaminodiphenylmethane, o-biphenylmethylamine, 1,2-propanediamine, 1,3-propanediamine, 2,4-diaminotoluene, 1,2-cyclohexanediamine, 4,5-dichloroo-phenylenediamine, diethylenetriamine and pyromellitic triamine;

in the oil phase solution, the mass fraction of acyl chloride monomer is 0.01-5%, the mass fraction of functionalized ZIF-7 nano particles is 0.001-5%, the organic solvent is selected from one or more of n-hexane, n-heptane, n-octane, n-dodecane, isododecane and isohexadecane, and the acyl chloride monomer comprises one or more of isophthaloyl dichloride, terephthaloyl dichloride, phthaloyl dichloride, trimesoyl chloride and multi-element aromatic sulfonyl chloride.

9. The method of preparing the enthalpy-exchange membrane doped with the functionalized ZIF-7 nanoparticles, according to claim 5, wherein in the step (3), the ultrafiltration membrane support layer is immersed in the aqueous phase solution for 2 to 5min and immersed in the oil phase solution for 30s to 2min.

10. The method of preparing a total heat exchange membrane doped with functionalized ZIF-7 nanoparticles, according to claim 5, wherein the post-treatment temperature in the step (4) is 60 to 80 ℃ and the time is 8 to 20min.

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