CN102250128B - Organometallic compound sensing material and preparation and application thereof - Google Patents

Abstract

The invention relates to a metal-organic compound sensing material and its preparation and application. The metal-organic compound is a metal-organic framework compound formed by the coordination of lithium salt and 1,4-naphthalene dicarboxylic acid, and is composed of a two-dimensional layered structure. The wireless extended three-dimensional structure belongs to the P2(1)/c space group and is a monoclinic crystal system; its structural formula is Li ₂ (1,4-ndc)(DMF), and the molecular formula of the crystal is C ₁₅ H ₁₃ Li ₂ NO ₅ , the coordination of lithium is a distorted tetrahedral configuration; the solvent-accessible void free volume of this compound accounts for 3.9% of the total volume. The material prepared by the invention has good sensing performance of solvent molecules and carbon dioxide, has regular response to solvent molecules and carbon dioxide of different concentrations under normal temperature and normal pressure conditions, and has high sensitivity, good selectivity, stable performance and easy regeneration.

Description

A metal organic compound sensing material and its preparation and application

technical field

The invention relates to a preparation method of a metal organic compound and its sensing performance to solvent molecules and carbon dioxide. Specifically, the metal organic compound is prepared by controlling synthesis conditions, and has good sensing performance to solvent molecules and carbon dioxide.

Background technique

Metal-organic compounds generally refer to metal-organic framework crystal materials with periodic network structures formed by self-assembly of organic molecular ligands and metal ions. Its crystal structure exhibits different topologies due to the different coordination modes of metals and ligands. The one-dimensional, two-dimensional or three-dimensional space formed by this material has an infinite network structure. Due to its unique pore structure, large specific surface area and selective adsorption of small molecules, its research has been highly valued by researchers from all over the world, and has achieved rapid development in the last ten years. The representative work is the coordination polymer MOF-5 (HailianLi, Mohamed Eddaoudi, M.O'Keeffe, O.M.Yaghi, Nature, 1999, 402, 6759, 276), based on the structure of the complex, the Yaghi research group selected zinc salts to interact with various rigid aromatic carboxylic acid bridging ligands to construct a series of pores with different sizes. It has potential applications in gas storage (especially hydrogen storage), gas separation, catalysis, nonlinear optics, magnetism, etc.

Quartz Crystal Microbalance QCM (Quartz Crystal Microbalance) is a resonant sensor composed of an AT-cut quartz crystal plate and metal electrodes plated on its upper and lower surfaces. As a micro-mass sensor, QCM has the advantages of simple structure, low cost, high sensitivity, and measurement accuracy of nanogram level. It is widely used in various scientific fields for composition analysis of gases and liquids and measurement of micro-mass. Detection of film thickness, etc. The porous metal-organic compound with a certain selective adsorption capacity is modified on the surface of the quartz crystal microbalance (QCM), and the adsorbed substance can be monitored qualitatively and quantitatively online by detecting the frequency change caused by the adsorption capacity of the material to different substances The concentration range varies within a certain range. At present, there are few research reports on the use of metal-organic compounds as chemical sensors in the world. Sun Dalin's research group at Fudan University successfully used QCM to measure the hydrogen storage properties of metal-organic complexes (Chen Guorong, Sun Dalin, Xu Huahua, Cao Guanying, Nano-metal-organic complex hydrogen storage materials and their preparation methods, patent publication No.: CN1546495); Sun Lixian's group of Dalian Institute of Chemical Physics applied QCM to the sensing of metal organic compounds for the first time (Ying-Ya Liu, Jian Zhang, Fen Xu, Li-Xian Sun, Tao Zhang, Wan-Sheng You, Yi Zhao , Julan Zeng, Zhong Cao, Daowu Yang, Crystal Growth & Design, 2008, 8, 3127). At present, most of the metal-organic compounds synthesized in the world are synthesized by the coordination of transition metals and rare earth metals, while there are few studies on the coordination polymers of alkali metals and alkaline earth metals, but the coordination forms of the coordination polymers of light metals are different. Compared with traditional transition and rare earth metals, it is possible to construct novel topological structures; and light metals can be directional designed and synthesized into lightweight metal-organic frameworks, which will have great advantages in gas storage and other aspects.

We synthesized a lithium metal organic compound with the molecular formula Li ₂ (1,4-ndc)(DMF) by a solvothermal method, and studied its sensing properties for different solvent molecules and carbon dioxide.

Contents of the invention

The object of the present invention is to provide a metal organic compound sensing material and its preparation and application, which has good sensing properties of solvent molecules and carbon dioxide.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

b＝15.630

c＝9.939

β＝111.999°，晶胞体积为1491.4

结构中含有两个晶体学独立的四配位的锂原子，Li-O的键长在1.881～2.061

之间，所以锂的配位是一个扭曲的四面体构型。由Platon软件计算得该化合物的溶剂可达的空自由体积占总体积的3.9％。Metal-organic compounds are new metal-organic framework compounds formed by the coordination of lithium salts and 1,4-naphthalene dicarboxylic acid. It is a wirelessly extended three-dimensional structure formed by stacking two-dimensional layered structures, belonging to the P2(1)/c space group, is a monoclinic crystal system. Its structural formula is Li ₂ (1,4-ndc) (DMF), and its structure is determined by testing on Bruker Samrt APEX II X-ray single crystal diffractometer. The results show that the molecular formula of the crystal is C ₁₅ H ₁₃ Li ₂ NO ₅ , unit cell parameter a=10.354

b=15.630

c=9.939

β=111.999°, the unit cell volume is 1491.4

The structure contains two crystallographically independent four-coordinated lithium atoms, and the bond length of Li-O is between 1.881 and 2.061

Between, so the coordination of lithium is a distorted tetrahedral configuration. Calculated by Platon software, the solvent accessible void free volume of this compound accounts for 3.9% of the total volume.

The metal organic compound sensing material can be prepared according to the following steps:

1) Hydrothermal or solvothermal synthesis: metal inorganic salts and organic carboxylic acids are dissolved in water or organic solvents according to different proportions, and metal organic compounds are obtained at different reaction temperatures and different crystallization reaction times;

The stoichiometric ratio of metal inorganic salt and organic carboxylic acid is 1.1-3.0 according to metal cation and acid radical ion; the reaction temperature is 60-160°C, and the crystallization reaction time is 24-72 hours;

2) Collect the product, filter it with suction, wash it with water or an organic solvent, and dry it in vacuum at 30-150° C. to prepare a metal-organic compound material with sensing properties.

The metal inorganic salt in the step 1) is nickel chloride, lithium chloride, chromium nitrate, zinc nitrate, lithium perchlorate or aluminum nitrate; the organic acid is formic acid, oxalic acid, isophthalic acid, terephthalic acid or 1 , 4-naphthalene dicarboxylic acid. The organic solvent is N, N'-dimethylformamide, 1.4-dioxane, ethanol, tetrahydrofuran or methanol.

The drying time of step 2) is adjustable from 2 to 24 hours.

The metal organic compound sensing material has good sensing performance for solvent molecules and carbon dioxide, and can be used for the adsorption detection of solvent molecules or carbon dioxide; the solvent molecules are water or ethylene glycol.

The sensing performance test of the sensing material is carried out on a Maxtek company quartz crystal microbalance (QCM: Quartz Crystal Microbalance), and the specific operation process is:

1) Weigh about 0.005-0.05g of sample, put it into 10-50ml of solvent, vibrate in ultrasonic for 1-2 hours, and the sample is fully dispersed in the solvent. The solvent is water, N, N'-dimethylformamide, ethanol or methanol;

2) Take 3-25 μl of the ultrasonically dispersed solution and drop it on the surface of the wafer, heat and evaporate the solvent to obtain a modified QCM wafer.

3) Put the wafer in a 0.5L airtight detection cell to test the sensing performance, monitor the frequency change of the wafer with a computer to know the sensing performance (adsorption and desorption performance) of the material to solvent molecules and carbon dioxide.

The sensing material and preparation method provided by the present invention have the following advantages:

1. The synthesis is simple and the cost is low. By adopting hydrothermal or solvothermal synthesis, the product with higher yield can be obtained in a short time.

2. Compounds can be prepared by controlling the synthesis conditions. For the same reactant, the same compound can be obtained by changing the reaction temperature, reaction time, ratio of reactant, solvent and other conditions within a certain range.

3. It has selective sensing effect for different solvent molecules, and is quite sensitive. Different concentrations of solvent molecules correspond to different frequency changes of the chip. The content of solvent molecules in the atmosphere can be judged by the change of chip frequency, and reproduce Good sex.

4. Reversible adsorption and desorption of carbon dioxide gas at room temperature, can be used as a carbon dioxide sensor.

Description of drawings

Fig. 1 is the schematic diagram of the effect of the QCM modified by the metal organic compound of the specific embodiment 1 of the present invention on the response frequency change effect of different concentrations of water;

Fig. 2 is a schematic diagram of the effect of the QCM modified by the metal organic compound in the specific example 1 of the present invention on the response frequency change of different concentrations of ethylene glycol.

Fig. 3 is a schematic diagram showing the effect of the metal organic compound modified QCM on the response frequency change of different concentrations of carbon dioxide according to the specific example 1 of the present invention.

Fig. 4 is the a-axis stacking diagram of the metal organic compound of specific example 1 of the present invention. It can be seen that the compound is a two-dimensional layered structure, and there are C-H...π interactions between the DMF and the naphthalene ring between the layers.

Fig. 5 is the X-ray diffraction spectrum of the metal organic compound of the embodiment 2 of the present invention, the embodiment 1 and the single crystal data simulation. It can be seen that the diffraction peaks of specific examples 1 and 2 are consistent with the simulated data, indicating that specific examples 1 and 2 are the same substance.

Detailed ways

The preparation process of the invention is simple, the cost is low, and a class of novel metal organic compounds can be prepared under mild conditions. The prepared material has good sensing performance of solvent molecules and carbon dioxide, and has a regular response to solvent molecules and carbon dioxide of different concentrations under normal temperature and pressure conditions, and has high sensitivity, good selectivity, stable performance, and easy regeneration.

Example 1

1. Weigh 0.18g of lithium chloride and 0.22g of 1,4-naphthalene dicarboxylic acid dissolved in 16ml of N,N'-dimethylformamide and 8ml of tetrahydrofuran mixed solution, magnetic stirring to fully dissolve, and then mix the solution Transfer to a 50ml stainless steel reaction kettle lined with polytetrafluoroethylene, crystallize in a synthesis oven at 150°C for 72 hours, and cool naturally to room temperature.

2. Suction filter the product, wash with N,N'-dimethylformamide, and dry under vacuum at 50°C for 24 hours to obtain the target product.

3. Sensing performance test: Take 0.06g of the target product, put it in 10ml of N,N'-dimethylformamide, and oscillate ultrasonically for 1 hour to make the product evenly dispersed in the solvent. Use a microsampler to take 10 μl of the ultrasonic solution and drop it on the surface of the wafer, heat and evaporate the solvent to obtain a modified QCM wafer. Processing conditions: evacuate the 0.5L airtight detection cell to below 0.01MPa, and the fundamental frequency change of the wafer reaches a stable baseline; Test conditions: Inject different amounts of solvent and carbon dioxide sequentially with an injector, and observe the frequency change of the wafer. It can be seen from Figure 1 that when the concentration of water injected into the airtight detection pool is 2-9ppm, the frequency changes of the corresponding wafers are also different, and as the concentration of water increases, the response frequency of the wafer changes more. When the corresponding frequency is close to stable, vacuumize the detection cell again, and the response frequency of the chip can return to the fundamental frequency, which shows that the sensing of water has good reproducibility; When the concentration of ethylene glycol is 0.2-0.8ppm, the response frequency of the corresponding chip changes to 600-2100Hz, and finally after the chip frequency is stable, the detection cell is evacuated, and the response frequency of the chip returns to the fundamental frequency, indicating that the material The sensing of ethylene glycol has good reproducibility; as can be seen from Figure 3, when the concentration of carbon dioxide injected into the airtight detection cell is 0.17-0.83mmol/L, the response frequency of the corresponding chip changes as 8-24Hz, wait until the frequency of the chip is stable and then evacuate the detection cell, the response frequency of the chip returns to the fundamental frequency, indicating that the material has good reproducibility in sensing carbon dioxide.

Example 2

1. Weigh 0.17g of lithium chloride and 0.21g of 1,4-naphthalene dicarboxylic acid dissolved in 18ml of N,N'-dimethylformamide and 6ml of tetrahydrofuran mixed solution, magnetic stirring to fully dissolve, and then mix the solution Transfer to a 50ml stainless steel reaction kettle lined with polytetrafluoroethylene, crystallize in a synthesis oven at 140°C for 48 hours, and cool naturally to room temperature.

2. Suction filter the product, wash it with N,N'-dimethylformamide, and dry it under vacuum at 60°C for 16 hours. The obtained crystal is determined to be consistent with the target product by X'Pert PRO powder X-ray diffractometer. Both have the same diffraction pattern, see Figure 5.

The preparation process of the invention is simple, the cost is low, and a class of novel metal organic compounds can be prepared under mild conditions. The prepared material has good sensing performance of solvent molecules and carbon dioxide, and has a regular response to solvent molecules and carbon dioxide of different concentrations under normal temperature and pressure conditions, and has high sensitivity, good selectivity, stable performance, and easy regeneration.

Claims (4)

1. A metal-organic compound sensing material, characterized in that: the sensing material is a metal-organic framework compound formed by the coordination of lithium chloride and 1,4-naphthalene dicarboxylic acid, which is composed of a two-dimensional layered structure The infinitely expanded three-dimensional structure formed by stacking belongs to the P2(1)/c space group and is a monoclinic crystal system; its structural formula is Li ₂ (1,4-ndc)(DMF), and the molecular formula of the crystal is C ₁₅ H ₁₃ Li ₂ NO ₅ , unit cell parameters

β=111.999°, the unit cell volume is

The structure contains two crystallographically independent four-coordinated lithium atoms, and the Li-O bond length is

Between, so the coordination of lithium is a distorted tetrahedral configuration; the solvent-accessible void free volume of this compound accounts for 3.9% of the total volume. 2. a preparation method of metal-organic compound sensing material as claimed in claim 1, characterized in that: it is prepared as follows, 1) Solvothermal synthesis: Lithium chloride and 1,4-naphthalene dicarboxylic acid are dissolved in DMF at a stoichiometric ratio of metal cations to acid radical ions of 1.1 to 3.0, and crystallized at a reaction temperature of 60 to 160°C. The metal organic compound is obtained under the reaction time of 24 to 72 hours; 2) Collect the product, filter it with suction, wash it with water or an organic solvent, and dry it in vacuum at 30-150° C. to prepare a metal-organic compound material with sensing properties. the 3. The preparation method according to claim 2, characterized in that: the drying time of the step 2) is adjustable from 2 to 24 hours. the 4. an application of metal organic compound sensing material as claimed in claim 1, characterized in that: said metal organic compound sensing material has good solvent molecule and carbon dioxide sensing performance, and can be used for the adsorption of solvent molecule or carbon dioxide detection; Wherein, the solvent molecule is water or ethylene glycol. the

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