CN102775430B - Coordination polymer porous material MAF-X8 and preparing method and application thereof - Google Patents

Abstract

The invention discloses a coordination polymer porous material MAF-X8 as well as its preparation method and application. The chemical formula of the coordination polymer porous material MAF-X8 involved in the present invention is [Zn(mpba)], wherein mpba ^2- represents the organic ligand 4-(3,5-dimethyl-pyrazol-4-yl)benzene Anion of formic acid (H ₂ mpba) after deprotonation. The MAF-X8 crystal of the present invention is in the orthorhombic crystal system, Ibca space group, and is a three-dimensional frame structure with one-dimensional channels and a porosity of 50% formed by mpba ^2- ligands bridging four-coordinated Zn ²⁺ ions , its Langmuir specific surface is greater than 1300m ² /g, and it has good thermal stability and chemical stability. In particular, the porous material MAF-X8 can be conveniently prepared as a thin film and applied in solid phase microextraction (SPME), and exhibits strong enrichment ability and adsorption selectivity for non-polar benzene series, and has The adsorption and desorption time is short, the detection limit is low, and the linear range is wide.

Description

A coordination polymer porous material MAF-X8 and its preparation method and application

technical field

The invention relates to the field of microporous coordination polymer porous materials, in particular to a coordination polymer porous material MAF-X8 and a preparation method thereof.

Background technique

Porous coordination polymers (PCPs) are crystalline materials composed of metal ions and organic ligands. They have the advantages of large specific surface area, low density, adjustable pore size, and strong modification of the pore surface. They can be widely used in Gas and liquid storage, separation, heterogeneous catalysis and other fields (US 5862796; US 6624318; US6930193; US 7196210; US 20080121105).

Although the commonly used polycarboxylic acid organic ligands have various coordination modes and are conducive to the formation of rich network structures, most of the PCPs constructed with them have low stability. In recent years, many studies have shown that PCPs constructed by ligands with imidazole or pyrazole groups usually have high thermal/chemical stability, special optomagnetic and adsorption properties, which have attracted the attention of international researchers. In addition, it is worth noting that most of the current PCPs are basically applied in the form of a large amount of powder because it is difficult to directly grow into a regular film, which undoubtedly limits its wider application in micro-devices, sensing and analysis and detection. Applications.

For example, solid-phase microextraction (SPME) is an efficient sample pretreatment and enrichment technology that integrates the whole process of sample extraction, separation and concentration, and is easy to combine with gas chromatography, high performance liquid chromatography and other analytical instruments, so It has been widely used in the fields of environment, biology, medicine, food and so on. The core of this technology lies in the solid-phase coating material and coating technology of the probe. However, due to the lack of mature adsorption materials, the current commercial probes and laboratory-made probes still face the problem of low enrichment and thermal stability. and poor chemical stability, poor reproducibility, long adsorption equilibrium time, and poor selectivity or anti-interference ability. In the face of increasingly complex sample matrix interference and higher requirements for trace and ultra-trace analysis, it is very important to seek an efficient adsorption material with superior performance.

Accordingly, we designed a bifunctional ligand with both carboxyl and pyrazolyl groups, and constructed a new type of porous coordination polymer with zinc ions, which has good chemical and thermal stability. Moreover, this coordination polymer can be easily prepared into high-quality thin films, which can be used to prepare high-efficiency SPME probes.

Contents of the invention

The object of the present invention is to provide a coordination polymer porous material MAF-X8 based on zinc pyrazole benzoate.

Another object of the present invention is to provide a method for preparing the above-mentioned porous material.

Another object of the present invention is to provide the application of the above porous material.

The object of the invention is achieved through the following technical solutions:

A coordination polymer porous material MAF-X8, its chemical formula is [Zn(mpba)], wherein mpba ² -represents organic ligand 4-(3,5-dimethyl-pyrazol-4-yl)benzoic acid (H ₂ mpba) anion after deprotonation. The porous material MAF-X8 of the present invention is crystallized in an orthorhombic crystal system, with Ibca space group, and is formed by mpba ² -ligands bridging four-coordinated Zn ²⁺ ions with one-dimensional channels (the widest and narrowest points respectively for and ) three-dimensional frame structure with a porosity of 50%. The methyl groups on the ligands completely block the Zn atoms and partly block the coordination O atoms, thus improving the hydrophobicity of the pores.

The preparation method of coordination polymer porous material MAF-X8 of the present invention:

Add H ₂ mpba, zinc nitrate and solvent together into a hydrothermal reactor, heat to 120°C for 3 days to obtain MAF-X8 single crystal or powder samples. The solvent is a mixture of N,N-dimethylacetamide (DMA) and methanol.

The preparation method of the thin film of coordination polymer porous material MAF-X8 of the present invention:

Add H ₂ mpba, zinc nitrate and solvent together into the hydrothermal reaction kettle, and put the substrate whose surface has been activated with acid into the reaction solution and heat it to 120°C for 1 day to obtain the MAF-X8 film.

Specifically: H ₂ mpba (0.1mmol), Zn(NO ₃ ) ₂ 6H ₂ O (0.1mmol), DMA (1.5mL) and methanol (4.5mL) were added together to the reaction with Teflon substrate Put the acid-activated substrate (such as a stainless steel needle) into the reaction solution, heat it to 120°C and keep it for 1 day to grow a MAF-X8 film on the surface of the substrate. The surface of the substrate was then washed with an appropriate amount of methanol and dried.

The MAF-X8 material of the present invention can be used in storage, separation, catalysis, sensing, molecular recognition or heat exchange materials by adsorbing guest molecules. In particular, the polymer material can be prepared as a thin film for use in solid phase microextraction.

Compared with the prior art, the present invention has the following beneficial effects:

(1) MAF-X8 designed and synthesized by the present invention has excellent thermal stability, which can be stabilized to 450°C; water stability is also very good, and its framework structure will not be damaged even if it is exposed to saturated water vapor; while general polycarboxylate Most acid-structured PCPs have poor thermal/water stability;

(2) MAF-X8 synthesized by the present invention has very large porosity and specific surface area. The specific surface and porosity of this material are obtained by utilizing low-temperature nitrogen adsorption and using the Langmuir and Dubinin-Raduskhvich equations to calculate respectively. Its Langmuir specific surface area is greater than ^{1300m2g -1} ;

(3) MAF-X8 synthesized by the present invention has very high enrichment for non-polar benzene series (such as benzene (B), toluene (T), ethylbenzene (E), xylene (X), BTEX for short) Under the same conditions, the enrichment amount is 18 to 157 times that of commercial PDMS coating materials, and 2 to 8 times that of commercial PDMS/DVB coating materials;

(4) The MAF-X8 synthesized by the present invention has a very short adsorption equilibrium time (7 minutes) and a very short desorption time (0.5 minutes) for non-polar benzene series, and has the advantages of low detection line and wide linear range. , very suitable for efficient and rapid analysis and detection;

(5) The MAF-X8 synthesized by the present invention has strong adsorption selectivity and anti-interference ability. Under the same conditions, it hardly adsorbs polar phenolic compounds, even when the amount of polar interfering substances greatly exceeds that of the analytes. When the amount of BTEX is increased, its adsorption to the latter is still very stable, basically not affected by a large amount of interfering substances. Under the same conditions, the effect of commercial PDMS or PDMS/DVB materials is much worse, such as the enrichment of BTEX will be significantly reduced with the increase of interferents.

Description of drawings

Fig. 1 is the structure of novel porous material MAF-X8 of the present invention;

Fig. 2 is the X-ray powder diffraction pattern of MAF-X8 of the present invention, including the original synthetic powder, the powder scraped off from the film and various powders after heat treatment;

Fig. 3 is the thermogravimetric curve figure of MAF-X8 of the present invention;

Fig. 4 is the nitrogen adsorption isotherm of MAF-X8 of the present invention at 77K;

Fig. 5 is the scanning electron micrograph of the film prepared by MAF-X8 of the present invention;

Fig. 6 is the adsorption equilibrium curve of SPME probe prepared by MAF-X8 of the present invention to BTEX;

Fig. 7 is the enrichment comparison of SPME probe prepared by MAF-X8 of the present invention and commercial PDMS and PDMS/DVB probe;

Fig. 8 is a comparison of the adsorption selectivity of the SPME probe prepared by MAF-X8 of the present invention and commercial PDMS and PDMS/DVB probes.

Detailed ways

The present invention is further explained below in conjunction with the examples, but the examples do not limit the present invention in any form.

Embodiment 1 Zinc pyrazole benzoate porous material MAF-X8 single crystal preparation

Ligand H ₂ mpba (0.022g, 0.1mmol), Zn(NO ₃ ) ₂ ·6H ₂ O (0.030g, 0.1mmol), N,N-dimethylacetamide (DMA, 0.1mL), ethanol ( 2.5mL), water (2.5mL) and mesitylene (1.0mL) were added into a hydrothermal reactor, heated to 120°C for 3 days to obtain a colorless MAF-X8 single crystal with a yield of 54%.

Example 2 Preparation of a large amount of powder of zinc pyrazole benzoate porous material MAF-X8

Add H ₂ mpba (0.0108g, 0.5mmol), Zn(NO ₃ ) ₂ ·6H ₂ O (0.150g, 0.5mmol), DMA (3.0mL), methanol (9mL) into the hydrothermal reaction kettle together, Heated to 120 ° C for 1 day, cooled to room temperature, washed with DMA and methanol to obtain a white to light yellow powder with a yield of 62%. The obtained powder was heated at 200°C for 30 min under a nitrogen atmosphere to remove the guest molecules, and the guest-free MAF-X8 could be obtained. The X-ray diffraction pattern of the product is shown in Figure 2.

Example 3 Structural Characterization of MAF-X8 Containing Guest Molecules and No Guest

Single crystal X-ray diffraction data were collected on a Bruker Smart APEX CCD diffractometer, graphite monochromator, with X-rays, data were collected in ω-scan mode, and absorption correction was performed using the SADABS program. The direct method is used for analysis, and then the coordinates of all non-hydrogen atoms are obtained by the difference Fourier function method and the least square method, and finally the structure is corrected by the least square method. The organic hydrogen atoms of the compound are obtained by the theoretical hydrogenation method, and the hydrogen of the guest water molecule is found by the difference Fourier map. The calculation work is done on the PC using SHELXTL program. The detailed crystal determination data are shown in Table 1. The structure is shown in Figure 1.

Table 1

^[a] R ₁ =∑||F _o |-|F _c ||/∑|F _o |. ^[b] wR ₂ =[∑w(F _o ² -F _c ² ) ² /∑w(F _o ² ) ² ] ^1/2 .

Example 4 The thermal stability characterization of the porous coordination polymer MAF-X8 obtained in Example 1 and 2

The thermal stability of the porous material was obtained by thermogravimetric analysis. The thermogravimetric curve is shown in Figure 3.

Example 5 Characterization of gas adsorption properties of porous coordination polymer MAF-X8 obtained in Example 2

The porous material to remove the guest was put into a glass sample tube, and then its nitrogen adsorption isotherm was measured on an ASAP 2020M adsorption instrument at 77K. The N ₂ adsorption isotherm is type I adsorption, the Langmuir specific surface area is 1306m ² ·g ^-1 , and the BET specific surface area is 1161m ² ·g ^-1 . The adsorption isotherm diagram is shown in Fig. 4 .

Embodiment 6 is the preparation of the SPME probe of coating with MAF-X8

First, immerse one end of the stainless steel needle in aqua regia for 15 minutes to activate the surface, and then wash it with pure water. Then H ₂ mpba (22 mg, 0.1 mmol), Zn(NO ₃ ) ₂ ·6H ₂ O (30 mg, 0.1 mmol), N,N-dimethylacetamide (1.5 mL) and methanol (4.5 mL) were added together Put the above-mentioned activated stainless steel needle into the reaction kettle with a polytetrafluoroethylene substrate vertically, heat it to 120°C in an airtight manner and keep it for 1 day to obtain the probe of the MAF-X8 film grown on the surface. Needle. Then the surface of the steel needle was washed with an appropriate amount of methanol and aged in a gas chromatograph. The SEM image of the film is shown in Figure 5.

Example 7 The adsorption equilibrium time of the SPME probe obtained in Example 6, the enrichment amount and the adsorption selectivity characterization

First configure BTEX or BTEX and phenolic compounds with different concentration ratios, (including 2-chlorophenol (CP), p-cresol (P), 2-nitrophenol (PC), 2,4-dichlorophenol (DCP) ), 2,4,6-trichlorophenol (TCP)) in aqueous solution. Then the prepared SPME probe was used for headspace extraction, and then thermal desorption was performed on gas chromatography-mass spectrometry (GC-MS) for separation and detection. The chromatographic peak retention time was used for qualitative analysis and peak area for quantitative analysis. Commercial PDMS (100 μm) and PDMS/DVB (65 μm) probes were also tested under the same conditions to compare the enrichment and adsorption selectivity with the prepared MAF-X8 probe. The adsorption equilibrium time is shown in Figure 6, and the enrichment amount and adsorption selectivity are shown in Figures 7 and 8, respectively.

Claims (4)

1. A coordination polymer porous material MAF-X8, its chemical formula is [Zn(mpba)], wherein mpba ^2- represents organic ligand 4-(3,5-dimethyl-pyrazol-4-yl) The anion of benzoic acid H ₂ mpba after deprotonation, the porous material crystallizes in the orthorhombic crystal system, Ibca space group, a=13.9249 Å, b=23.653 Å, c=23.637 Å, through the mpba ^2- ligand bridge A three-dimensional framework structure with one-dimensional channels formed by four-coordinated Zn ²⁺ ions. 2. The preparation method of the coordination polymer porous material MAF-X8 according to claim 1 is characterized in that it comprises the following steps: 4-(3,5-dimethyl-pyrazol-4-yl)benzoic acid, zinc nitrate and Add the solvent together into the hydrothermal reaction kettle, heat to 120°C and react for 3 days to obtain MAF-X8 single crystal or powder samples. 3. The preparation method of the thin film of the coordination polymer porous material MAF-X8 according to claim 1 is characterized in that it comprises the following steps: 4-(3,5-dimethyl-pyrazol-4-yl) benzoic acid, nitric acid Zinc and solvent were added into the hydrothermal reaction kettle together, and the substrate whose surface was activated with acid was put into the reaction solution and heated to 120°C for 1 day to obtain the MAF-X8 film. 4. The preparation method according to claim 2 or 3, characterized in that the solvent is a mixture of N,N-dimethylacetamide and methanol.