CN113083252A

CN113083252A - Organic metal framework material mixed matrix membrane and preparation method thereof

Info

Publication number: CN113083252A
Application number: CN202110374749.2A
Authority: CN
Inventors: 高明; 王学东; 王慧利; 张薇
Original assignee: Foshan Nanhai Suke Environmental Research Institute
Current assignee: Foshan Nanhai Suke Environmental Research Institute
Priority date: 2021-04-07
Filing date: 2021-04-07
Publication date: 2021-07-09

Abstract

The invention discloses a syringe type membrane microextraction technology combined HPLC method (SMME/HPLC-FLD) based on a metal organic framework-mixed matrix membrane (MOF-MMM) for detecting PAHs in tea soup. We have made four MOF-MMMs, namely UiO-66(Zr) -MMM, MIL-53(Al) -MMM, MIL-101-MMM and NH 2-MIL-101-MMM. The MOF-MMM with the diameter of 25mm is cut and put into a replaceable membrane filter head, and then a simple extraction device can be assembled by means of a needle cylinder. In the enrichment extraction process, the benzene ring in the MOFs is combined with PAHs in a pi-pi interaction and/or hydrophobic interaction mode, so that the PAHs in the tea soup can be efficiently separated and enriched. The injector type membrane micro-extraction device has the advantages of convenient carrying, simple operation, low cost and the like; meanwhile, the UiO-66(Zr) -MMM can simply and quickly enrich PAHs in the process of contacting with a sample, vortex or ultrasound is not needed in the adsorption process, and after adsorption, MOFs particles after adsorption are not needed to be collected through centrifugation. The method is very suitable for analyzing and detecting trace PAHs in food samples.

Description

Organic metal framework material mixed matrix membrane and preparation method thereof

Technical Field

The invention belongs to the field of membrane materials, and particularly relates to an organic metal framework material mixed matrix membrane and a preparation method thereof.

Background

In recent years, development of some green and environmentally friendly pretreatment techniques with no or little use of organic solvents has been the main research direction in the field of analytical chemistry. Among them, solid phase extraction technology using metal-organic frameworks (MOFs) as adsorbents is becoming mature day by day. MOFs are a new class of porous materials, which are generally porous crystals with an infinitely expanding network structure formed by two parts of inorganic metal ions and organic ligands through hybridization. Due to the diversity of self-structure and properties, the MOFs are widely applied in many fields, such as catalysis, gas separation and storage, sensors, nonlinear optical drug delivery, organic matter removal and the like, wherein the MOFs have a wide potential application prospect in the field of analytical chemistry due to a plurality of functional groups. In order to simplify the process of collecting the MOFs after extraction, in recent years, many researchers develop magnetic MOFs, which are separated under the action of an external magnetic field, are simple and convenient to operate, and can be reused. However, some processes for magnetizing MOFs are too cumbersome. Therefore, Denny and Cohen propose to prepare metal organic framework mixed matrix thin films (MOF-MMMs) using MOFs as an adsorbent and polyvinylidene fluoride (polymeric macromolecules) as a membrane support macromolecule. Uniformly dispersing MOFs in acetone to prepare a solution A, dissolving PVDF powder in dimethylacetamide (DMAc) to prepare a solution B, mixing the solutions A and B in a physical mode, then evaporating the acetone to obtain a liquid like ink, and drying a coating film to obtain the MOF-MMMs. Thus, the porosity of the MOFs is reserved, the stability and the flexibility are good, and the synthesis in-situ modification can be carried out, so that the MOFs are easier to process and use.

At present, the MOF-MMMs are mainly applied to aspects of gas phase separation, nano-scale filtration, molecular sieving, catalysis and the like, and are rarely applied to aspects of solid phase extraction. Few scholars have pointed out that as the doping amount of MOFs increases, both the water flux and the hydrophilicity of MOF-MMM increase. Therefore, this project attempted to explore the application of MOF-MMMs to syringe solid phase membrane microextraction (SMME).

Tea is second only to water. Due to their high surface area and special production process, tea leaves may be contaminated with Polycyclic Aromatic Hydrocarbons (PAHs) in the air. PAHs are polycyclic aromatic hydrocarbons consisting of two or more fused aromatic rings, a well-known class of carcinogens found in food products. Thus, for many years, many reports have been published relating to the analysis of PAHs in food and environmental samples, e.g., QuEChERS, MSPE and DLLME. In order to expand the application of the MOF-MMMs and reduce the dependence on experimental instruments, the MOF-MMMs are cut and put into a replaceable membrane filter head, and then the MOF-MMMs are assembled into a simple injector type solid membrane micro-extraction device by virtue of a needle cylinder. The membrane extraction process can be carried out at normal temperature by pushing under pressure.

In conclusion, we propose a syringe type membrane micro-extraction based on MOF-MMMs combined with HPLC/FLD method to detect PAHs in tea soup, so as to expand the application of MOF-MMMs. The MOFs film with high doping amount has the characteristics of good mechanical stability, good flexibility, low cost and the like. Meanwhile, auxiliary extraction means such as vortexes and ultrasound are avoided, and the recovery problem of the extracted MOFs is solved. This will make the application range of MOF-MMMs wider.

Disclosure of Invention

The invention aims to provide a metal organic framework material-based mixed matrix membrane (MOF-MMMs), which replaces the filler of a traditional solid phase extraction column, and uses a disposable needle cylinder as a simple injector type micro-extraction device to realize the high-efficiency separation and enrichment of field polycyclic aromatic hydrocarbon.

The second purpose of the invention is to provide a preparation method of the organic metal framework material mixed matrix membrane.

The third purpose of the invention is to provide the application of the organometallic framework material mixed matrix membrane as an extraction material in an injector extraction device.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

the organic framework material mixed matrix membrane material is prepared by taking a porous material MOF as an adsorbent, mixing the MOF, PVDF and a membrane preparation solvent, and then coating, drying and the like. The porous property of the MOFs is reserved, the stability and the flexibility are good, and the synthesis in-situ modification can be carried out, so that the MOFs are easier to process and use. The membrane can be combined with a syringe to establish a micro-extraction method suitable for field rapid enrichment; the device is simple, and no additional experimental instruments such as vortex and ultrasound are needed for assistance; the extraction device has the advantages of low cost, convenient carrying, wide obtaining way, various specifications, high practical value and good application prospect in the rapid extraction, enrichment and detection of the field environment sample of the trace polycyclic aromatic hydrocarbon pollutants.

The preparation method of the organic metal framework material mixed matrix film comprises the following steps;

1) zirconium chloride (0.318g) and terephthalic acid (0.204g) were mixed with 40mL of DMF, and after magnetically stirring for 10min, it was placed in an autoclave and reacted at 120 ℃ for 24 h.

2) After cooling, the mixture was soaked in 50mL of DMF for 30min and centrifuged at 8000rpm for 5min to collect the solid product.

3) Washed three times with ultrapure water and ethanol each, and then vacuum-dried at 60 ℃ for 10h to obtain a white powder. Making the MOF material.

4)20mg of UiO-66(Zr) powder was dispersed in 5mL of acetone and sonicated for 30 min.

5)3.5mL of PVDF solution (100mg of PVDF powder dissolved in 4mL of N, N-dimethylacetamide) was added dropwise to the above mixture and sonicated for 30 min.

6) Acetone was blown dry with nitrogen and the resulting mixture was uniformly coated onto a round glass substrate with a d ═ 8cm and placed in a 60 ℃ forced air drying oven for 1h to remove the solvent.

7) After complete drying, the glass substrate was immersed in methanol and the MMM rapidly delaminated into a film, which was then dried in air. And preparing the organic metal framework material mixed matrix film.

The metal organic framework mixed matrix film (MOF-MMMs) is a novel mixed material, combines the functionality of MOFs and the strong plasticity of polymeric macromolecules, and has huge development and application values. In addition, the MOF-MMMs mixed matrix membrane has uniform texture and tough material, is very suitable for being used as a membrane material for adsorbing and extracting trace pollutants in combination with an injector extraction device, and has very wide application prospect in the rapid analysis and detection of the trace pollutants in a field environment sample.

The method for using the organic metal framework material mixed matrix membrane in combination with the injector micro-extraction device mainly comprises the following steps:

1) the film was punched and cut to obtain a circular piece having a diameter d of 25 mm.

2) The resulting circular MOF-MMMs membrane was loaded into a filter head of a replaceable filter membrane, which was then attached to a syringe with luer-lock tip.

3) Sample solution (10mL, 5. mu. g L)^-1pH 4) was charged into a syringe and passed through a filter head containing UiO-66(Zr) -MMM at a certain flow rate, which was repeated six times.

4) Elution was performed with 1mL of acetonitrile containing 3% hydrochloric acid, and repeated six times.

5) 5 μ L of the eluate was injected into the HPLC system for detection.

The invention has the following outstanding advantages: (1) the MOF-MMMs membrane fixes MOF crystal materials, reduces the loss of adsorbents, solves the problem of difficult recovery after MOFs extraction, and simultaneously expands the application of non-magnetic solid materials; (2) the MOFs and the polymer macromolecules can be replaced according to specific requirements, so that high-selectivity adsorption of different pollutants can be realized, and the variability of the method is reflected. The MOF-MMMs in the method are simple to synthesize and can be modified after synthesis, which is beyond the reach of common materials; (3) the combined injector extraction device has a simple structure, can be used for releasing the limitation of experimental instruments (vortex instruments and ultrasonic instruments), and expands the application of MOF-MMM to field rapid enrichment; (4) the device has the advantages of low cost, convenient carrying, wide obtaining way and various specifications. (5) The MOF-MMMs can be developed into an automatic core component to participate in the extraction process due to the free cutting.

Drawings

FIG. 1 is a process scheme of the preparation method of the organometallic framework material mixed matrix film of the present invention

FIG. 2 is a scanning electron microscope image of a MOF-MMMs membrane of the invention (A is a magnification of 20,000X, B is a partial magnified view of A, magnification of 160,000X);

FIG. 3 is a graph of the MOF-MMMs membrane contact angle measurement analysis of the present invention;

FIG. 4 is a graph of the surface charge analysis of MOF-MMMs membranes of the invention;

FIG. 5 is a high performance liquid chromatogram of the MOF-MMMs membrane of the invention used for detecting multiple trace polycyclic aromatic hydrocarbons.

Detailed Description

The MOF-MMMs of the invention are further illustrated below with reference to specific examples.

Example 1

The method for preparing the UiO-66(Zr) -MMMs mixed matrix membrane of the embodiment adopts the following steps:

1) UiO-66 (Zr): zirconium chloride (0.318g) and terephthalic acid (0.204g) were mixed with 40mL of DMF, and after magnetically stirring for 10min, it was placed in an autoclave and reacted at 120 ℃ for 24 h. After cooling, the mixture was soaked in 50mL of DMF for 30min, centrifuged at 8000rpm for 5min to collect the solid product, washed three times with ultrapure water and ethanol each, and then vacuum-dried at 60 ℃ for 10h to obtain a white powder. The present embodiment should have the following features: the characteristic peak of UiO-66(Zr) appears near the positions of theta 7.3 degrees, 8.4 degrees, 25.7 degrees and the like as a result of X-ray diffraction, and the UiO-66(Zr) is made into a film and still maintains a certain crystal structure; fourier transform infrared spectroscopy at 1568, 1020, 742, 665 and 1180cm^-1There is a characteristic absorption peak near the equal parts.

Example 2

The method for preparing the MIL-53(Al) -MMMs mixed matrix membrane of the embodiment adopts the following steps:

1) MIL-53 (Al): 3.38g of aluminum nitrate nonahydrate and 1.00g of terephthalic acid were dispersed in a mixed solution of 44mL of DMF and 16mL of ultrapure water, and mechanically stirred in a water bath at 40 ℃ for 2 hours. The mixture was transferred to an autoclave having a volume of 100mL, and then reacted in an oven at 130 ℃ for 48 hours. After cooling, the mixture was soaked in 50mL of DMF for 30min, centrifuged at 8000rpm for 5min to collect the solid product, washed three times with ultrapure water and ethanol each, and then vacuum-dried at 60 ℃ for 10h to obtain a white powder.

Example 3

NH of this example₂-MIL-101(Fe) -MMMs mixed matrix membrane preparation method, using the following steps:

1)NH₂-MIL-101 (Fe): preparation of NH Using a Solvothermal Process₂MIL-101 (Fe). To a solution of 60mL DMF was added ferric chloride hexahydrate (19.75mmol, 5.338g) and terephthalic acid (10.0mmol, 1.812g), the mixture was magnetically stirred for 10min, then transferred to a 100mL stainless steel autoclave with a Teflon liner and heated at 110 ℃ for 24 h. After cooling, the mixture was soaked in 50mL of DMF for 30min, centrifuged at 8000rpm for 5min to collect the solid product, washed three times with ultrapure water and ethanol each, and then vacuum-dried at 60 ℃ for 10h to give a dark brown solid powder.

Example 4

The method for preparing the MIL-101(Fe) -MMMs mixed matrix membrane of the embodiment adopts the following steps:

MIL-101 (Fe): the synthesis of MIL-101(Fe) is similar to the above method. 5.338g of ferric chloride hexahydrate (19.75mmol) and 1.661mg of terephthalic acid (10mmol) were dissolved in 60mL of DMF. Stirring vigorously at room temperature for 10min, transferring the mixed solution into a polytetrafluoroethylene liner, transferring into a stainless steel autoclave, sealing the autoclave, and heating at 110 deg.C for 24 h. After cooling, the mixture was soaked in 50mL of DMF for 30min, centrifuged at 8000rpm for 5min to collect the solid product, washed three times with ultrapure water and ethanol each, and then vacuum-dried at 60 ℃ for 10h to give an orange solid powder.

And (3) performance testing:

1) membrane reuse number test:

the UiO-66(Zr) -MMM is put into ultrapure water to be soaked overnight, the surface appearance is not changed according to visual observation, and no solid residue is observed in the water, which indicates that the membrane structure of the UiO-66(Zr) -MMM is stable. Although the extraction membrane in the extraction device was designed for single use, we tested it for re-use performance. And (3) taking out the extracted UiO-66(Zr) -MMM by using tweezers, and respectively taking a certain amount of acetonitrile and ultrapure water for rinsing. The membrane was placed back on the filter head, the SMME extraction process was repeated under the optimum experimental conditions, and the PAHs recovery effect was determined, with the result that after four cycles of use, the recovery rate decreased only by about 0.4%, indicating that the UiO-66(Zr) -MMM could be reused. However, the membrane starts to break during the fourth extraction, probably due to the friction between the membrane and the closing ring when the filter head is unscrewed.

2) Performance evaluation of the microextraction method:

coefficient of correlation (R) by standard curve equation²) Linear Range (LRs), limit of detection (LOD), limit of quantitation (LOQ), and daily and diurnal precision (RSD) novel evaluations of MOF-MMMs membranes of the invention in conjunction with syringe microextraction methods were performed. Results are shown in Table 1, R²The value is between 0.9982 and 0.9993, and the LRs of the five PAHs are between 0.07 and 25 mu g L^-1In ultrapure water, the LOD range is 0.02-0.08 μ g L at a signal-to-noise ratio S/N of 3^-1LOQ ranges from 0.07 to 0.27 μ g L at a signal-to-noise ratio S/N of 10^-1. Three concentration levels, low, medium and high (low ═ 1 μ g L) were detected^-1In ═ 5 μ gL^-1And high 10 μ g L^-1) Intra-day and inter-day RSD to assess the accuracy of the experiment. Detecting the same batch of samples once every 2h and continuously detecting for 6 times when the recovery rate in the detection day is measured; when the daytime recovery rate is measured, a group of two samples are subjected to sample injection detection at 8:00 a.m. every day, and the samples are continuously tested for 3 days to obtain the intra-day and daytime RSD data. The intra-day and inter-day accuracies (expressed as RSD) were 1.2 to 6.7% and 0.3 to 8.4%, respectively. These data indicate that the SMME process has a high R²The value, wide LRs and high precision, so the SMME/HPLC-FLD method has wide application range, good stability, good reproducibility and repeatability.

TABLE 1 analytical Properties of the methods

Note: the concentrations of the related substances in the performance analysis are respectively mu g L^-1

3) Comparison with other detection methods

TABLE 2 comparison of the method of the invention with other detection methods

Table 2 shows the comparison of the performance of the extraction process with other extraction processes, and the RSDs and LODs of the process are comparable to those of published documents. For example, the detection limit of the SMME method (0.02-0.08. mu. g L)^-1) Is 20 times lower than the detection limit of the Agr-Ch-C18-mu SPE/HPLC-UV method (0.67 mu g L)^-1) (ii) a Precision of SMME method: (<10.7%) ratio HPLC-FLD/UV-VIS method (<18.7%) was much lower.

Claims

1. A metal organic framework-mixed matrix film characterized as a white film; the structure is in a classical cubo-octahedral structure under a scanning electron microscope; the ray diffractometer shows that the crystallinity of the crystal is high and the crystal form is good; the contact angle showed higher hydrophilicity; the isoelectric point of the membrane is about 4 by analyzing the surface charge of the membrane.

2. A method for preparing metal organic framework-mixed matrix membranes (MOF-MMMs) according to claim 1, comprising the steps of:

1) mixing zirconium chloride (0.2-0.4 g) and terephthalic acid (0.1-0.3 g) with 20-60 mL of DMF, magnetically stirring for 5-15 min, then putting the mixture into an autoclave, and reacting for 12-36 h at 120 ℃;

2) after cooling, soaking the mixture in 50mL of DMF for 20-40 min, and centrifuging at 6000-10000 rpm for 2-8 min to collect a solid product;

3) washed three times with ultrapure water and ethanol each, and then vacuum-dried at 60 ℃ for 10h to obtain a white powder. Making a MOF material;

4) dispersing 10-30 mg of UiO-66(Zr) powder in 5mL of acetone, and carrying out ultrasonic treatment for 20-40 min;

5) dripping 2-5 mL of PVDF solution into the mixture, and carrying out ultrasonic treatment for 10-50 min;

6) blowing acetone by nitrogen, uniformly coating the obtained mixture on a round glass substrate with the d being 8cm, and placing the glass substrate in a 60 ℃ forced air drying oven for 0.5-2 h to remove the solvent;

3. A method of using the organometallic framework material mixed matrix membrane of claim 1 in conjunction with an injector microextraction device, consisting essentially of the steps of:

1) punching and cutting the film to obtain a wafer with the diameter d equal to 25 mm;

2) loading the obtained circular MOF-MMMs membrane into a filter head of a replaceable filter membrane, and connecting the filter head to a syringe with a luer-lock tip;

3) mixing the sample solution (5-20 mL, 5 mu g L)^-1) Loading into an injector, and enabling the injector to pass through a filter head filled with UiO-66(Zr) -MMM at a certain flow rate, and repeating for 1-10 times;

4) eluting with 0.5-2 mL of acetonitrile containing 3% hydrochloric acid, and repeating for 1-10 times;

5) 5 μ L of the eluate was injected into the HPLC system for detection.