CN109879898B

CN109879898B - Two-dimensional binuclear cadmium coordination polymer and preparation method and application thereof

Info

Publication number: CN109879898B
Application number: CN201910292342.8A
Authority: CN
Inventors: 卢丽萍; 李少东
Original assignee: Shanxi University
Current assignee: Shanxi University
Priority date: 2019-04-12
Filing date: 2019-04-12
Publication date: 2021-07-02
Anticipated expiration: 2039-04-12
Also published as: CN109879898A

Abstract

The invention provides a two-dimensional binuclear cadmium coordination polymer, which has a chemical simple formula as follows: { [ Cd)₂(cpota)(H₂cpota)(2,2'‑bpy)₂(H₂O)]·2H₂O}_nIn which H is₃cpota is ortho- (p-carboxyphenyl) oxyterephthalic acid (which in its deprotonated form is H, respectively)₂cpota‑，Hcpota^2‑And cpota^3‑) 2,2'-bpy is 2,2' -bipyridine, and n represents polymerization. The coordination polymer is prepared by a hydrothermal method, namely: adding Cd (NO) into the solution at a molar ratio of 2:2:1:300-350₃)₂·6H₂Adding O, 2' -bipyridyl, O- (p-carboxyphenyl) oxy terephthalic acid and water into a polytetrafluoroethylene tube, adjusting the pH value to 5 by using 0.5mol/L KOH, stirring for 30 minutes, putting the polytetrafluoroethylene tube into a hydrothermal reaction kettle, reacting for 3 days at 413K, naturally cooling to room temperature, collecting colorless blocky crystals, washing by using distilled water, and drying in vacuum. The coordination polymer is a two-dimensional structure having binuclear cadmium dimer units. The coordination polymer has good selectivity detection (detection limit is 3.37 multiplied by 10) on bivalent copper ions in aqueous solution^‑6M), and can be repeatedly used at least five times or more.

Description

Two-dimensional binuclear cadmium coordination polymer and preparation method and application thereof

Technical Field

The invention relates to a coordination polymer, in particular to a coordination polymer with a two-dimensional structure constructed on the basis of transition metal cadmium (II), o- (p-carboxyphenyl) oxy terephthalic acid and 2,2' -bipyridyl, a preparation method thereof and application of the coordination polymer as a chemical sensor for detecting divalent copper ions in an aqueous solution.

Background

Cu²⁺The ions are essential trace elements of human bodies and play a vital role in the fields of environment, biology, chemistry and the like. However, Cu in human body²⁺Both lack and excess of ions may cause some types of serious disease, including alzheimer's disease, parkinson's disease and wilson's disease. In addition, copper is also an important metal contaminant due to its widespread use in modern society. Therefore, from environmental protection and human body safetyIn all aspects, it is desirable to monitor Cu²⁺Ion, thereby developing Cu which is convenient and economical²⁺Ion detection methods are of critical importance. Recently, the use of metal organic coordination polymers as fluorescent probes has been rapidly developed because they can provide a simple, rapid, highly selective, and cost-effective real-time monitoring method. However, some of these fluorescent probes of coordination polymer cannot exist stably in an aqueous solution, and their application is greatly limited. Therefore, the synthesis of Cu in aqueous solution is designed²⁺The fluorescent probe with the ion selective recognition function is a problem which needs to be solved urgently at present and is a key direction of the research.

Disclosure of Invention

The invention aims to provide a two-dimensional binuclear cadmium coordination polymer, a preparation method thereof and a fluorescent probe for detecting Cu in an aqueous solution by using the coordination polymer based on the technical current situation²⁺Application of ions.

The invention provides a two-dimensional cadmium coordination polymer, which has a chemical simple formula as follows: [ Cd ]₂(cpota)(H₂cpota)(2,2'-bpy)₂(H₂O)]_n·2nH₂O, wherein H₃cpota is o- (p-carboxyphenyl) oxyterephthalic acid (which in deprotonated and fully deprotonated form is H, respectively)₂cpota^-And cpota^3-) 2,2'-bpy is 2,2' -bipyridine, n represents polymerization; the structural formula (wave line represents polymeric linkage) is:

the crystal of the cadmium coordination polymer belongs to a monoclinic system, and the space group is P_21/cThe unit cell parameters are:

α is 90 °, β is 96.800(1 °), and γ is 90 °. Two adjacent pro-cadmiumThe two carboxylic acid oxygen atoms are bridged to form a binuclear cadmium dimer unit. The Cd1 atom is coordinated with four O atoms of three different carboxyl groups and two N atoms from 2,2' -bipyridine; cd2 atom is coordinated with four O atoms of three different carboxyl groups, one coordinated water and two N atoms from 2,2' -bipyridine, and the Cd-O bond length is in the range of

The Cd-N bond length range is

Two carboxyl groups are each syn-syn, mu₂The-oxo mode connects two Cd ions to form [ Cd ]₂(2,2'-bpy)₂(μ₂-COO)₄(H₂O)]Dimer units, each dimer unit linking three fully deprotonated cpota^3–Ligand, per cpota^3–The ligand is connected with three dimer units to form the binuclear two-dimensional cadmium metal organic coordination polymer. X-ray powder diffraction confirmed that the crystalline sample was homogeneous and stable.

The preparation method of the cadmium coordination polymer provided by the invention comprises the following steps:

(1) adding Cd (NO) into the solution at a molar ratio of 2:2:1:300-350₃)₂·6H₂O, 2' -bipyridine, O- (p-carboxyphenyl) oxyterephthalic acid and water were added to a polytetrafluoroethylene tube and the pH was adjusted to 5 with 0.5mol/L KOH;

(2) placing the polytetrafluoroethylene tube in a stainless steel reaction kettle, reacting for three days at 413K, naturally cooling to room temperature to precipitate colorless blocky crystals, washing with distilled water, and vacuum drying to obtain 75-85% yield.

Compared with the prior art, the invention has the beneficial effects that:

the cadmium coordination polymer is obtained under the hydrothermal synthesis condition, the preparation process is simple, and the yield and the purity are high. Thermogravimetric analysis shows that the structure decomposes above 290 ℃, and the practical temperature range is below 290 ℃. The cadmium coordination polymer of the present invention is prepared from two different deprotonated 2- (4-carboxyphenoxy) terephthalic acids (H)₃cpota) ligand construction, fully deprotonated cpota^3–Ligand binding [ Cd₂(2,2'-bpy)₂(μ₂-COO)₄(H₂O)]Dimer units form two-dimensional structures, partially deprotonated H₂cpota^–The ligand provides a carboxy organic site. The cadmium coordination polymer can not only exist stably in water, but also can be used as Cu in a water phase²⁺Fluorescent probes for ions.

Drawings

FIG. 1 is a crystal structure diagram of a cadmium coordination polymer of the present invention.

FIG. 2 is an X-ray powder diffraction pattern at 298K of a cadmium coordination polymer of the present invention.

FIG. 3 is a thermogravimetric analysis of a cadmium coordination polymer of the present invention.

FIG. 4 is a fluorescence spectrum of a cadmium coordination polymer of the present invention mixed with various metal ion solutions in an aqueous solution.

FIG. 5 adding Cu of different concentrations to the cadmium coordination polymer aqueous solution of the present invention²⁺Fluorescence pattern of the ions.

FIG. 6 adding Cu to the aqueous solution of cadmium coordination polymer of the present invention²⁺And (b) a fluorescence linear calibration curve (a) and a Stern-Volmer curve (b) of the ions.

FIG. 7 detection of Cu by cadmium coordination polymer in aqueous solution²⁺Fluorescence intensity of the ions.

Detailed Description

EXAMPLE 1 preparation of cadmium coordination Polymer

0.1mmol H is weighed₃cpota, 0.2mmol of 2,2' -bpy and 0.2mmol of Cd (NO)₃)₂·6H₂O was added to 6mL of H₂In a 13mL polytetrafluoroethylene tube of O, KOH at a concentration of 0.5mol/L was slowly added dropwise to the stirred mixture to adjust the pH to 5, and stirring was continued for 30 minutes. Placing the polytetrafluoroethylene tube into a stainless steel reaction kettle, heating for three days at 413K, naturally cooling to room temperature to precipitate colorless blocky crystals, washing with water, and vacuum drying to obtain the product with yield of 83%. Elemental analysis: c₅₀H₃₈N₄O₁₇Cd₂Calculated as C50.34, H3.19, N4.70%; the experimental values are C50.62, H2.94 and N5.03%.

EXAMPLE 2 determination of the Crystal Structure of cadmium coordination Polymer

The crystal structure is measured by adopting X-ray single crystal diffraction, a test instrument is Bruker D8Venture, a radiation light source is Mo-Kalpha rays monochromatized by a graphite monochromator, a scanning mode is omega, and diffraction data are collected at room temperature. Data were restored by SAINT program and then corrected for absorbance using SADABS program. The crystal structure is obtained by direct resolution of SHELXL-2016. The detailed crystal determination data are shown in Table 1, and the crystal structure is shown in two-dimensional structure in FIG. 1.

TABLE 1 crystallography data for cadmium coordination polymer materials

Example 3 powder diffraction analyte phase

The X-ray powder diffraction experiment map is consistent with the simulation map, which shows that the phase of the cadmium coordination polymer crystal sample is uniform, and is shown in figure 2.

Example 4 thermal stability analysis of cadmium coordination polymers

As shown in FIG. 3, the thermogravimetric analysis result shows that the coordination polymer gradually loses about 3.84% of weight between 100 ℃ and 180 ℃, and proves that two free water molecules (theoretical value is 3.29%) exist in the coordination polymer, and gradually loses one coordination water between 200 ℃ and 276 ℃, and the weight loss is about 1.62%. It can be seen from thermogravimetric analysis that the main structure is decomposed at 290 ℃ or higher, indicating that the cadmium coordination polymer of the present invention is suitable for temperatures below 290 ℃.

Example 5 cadmium coordination polymers of the invention to Cu in Water²⁺Selective identification of ions

First, 10mL of a 1X 10-concentrated solution was prepared^-4Different cation solutions of mol/L (the cations are respectively Cd)²⁺、Ba²⁺、Co²⁺、Pb²⁺、Ca²⁺、Ni²⁺、Fe²⁺、Na⁺、K⁺、Fe³⁺、Mn²⁺、Cu²⁺And Cr³⁺). 2mg of the coordination polymer was added to 10mL of each of the different anion solutions, and sonicated for 30 minutes and precipitated for three days. And taking the supernatant, and measuring the fluorescence emission spectrum intensity of the supernatant under the conditions that the excitation wavelength is 290nm and the slit width is 10 nm. As shown in FIG. 4, Co²⁺、Fe²⁺And Fe³⁺Ions all cause certain quenching on the fluorescence of the cadmium coordination polymer, particularly the Cu coordination polymer²⁺The ions have unique fluorescence selectivity.

Example 6 identification of Cu in Water by cadmium coordination polymers of the invention²⁺Ion sensitivity 2mg of the coordination polymer was added to 10mL of water, sonicated for 30 minutes, and allowed to settle for three days to form a uniform suspension of cadmium coordination polymer. 2mL of the supernatant was gradually added dropwise at a concentration of 1X 10^-4mol/L of Cu²⁺Ionic, as can be seen in FIG. 5, the aqueous suspension of cadmium coordination polymer shows very strong fluorescence at 327nm at an excitation wavelength of 290 nm. Titration curves show that with Cu in the system²⁺The fluorescence of the solution decreases significantly with increasing ion concentration. Furthermore, as shown in fig. 6b, at low concentrations, the quenching effect can be handled with the Stern-Volmer equation: i is₀/I＝1+K_sv×[M]，I₀The fluorescence intensity of the aqueous suspension of cadmium coordination polymer, I the addition of Cu to the aqueous suspension of cadmium coordination polymer²⁺Fluorescence intensity after ionization, [ M ]]Is Cu²⁺Concentration of ion, K_svIs the quenching constant. The Cu²⁺The quenching constant for the coordination polymer is K_sv＝1.318×10⁴M^-1. In addition, the cadmium coordination polymer is used for Cu²⁺The detection limit of the ions is 3.37X 10^-6M, showing that the coordination polymer is to Cu in aqueous solution²⁺The ions have higher response sensitivity. The circulation test experiment shows that the coordination polymer is in the presence of Cu²⁺The fluorescence intensity was maintained after 5 cycles of ion detection (FIG. 7)Has good repeated utilization rate. The experiments show that the coordination polymer can be used for detecting Cu in water²⁺A probe for the ion.

Claims

1. A two-dimensional binuclear cadmium coordination polymer has a chemical formula: { [ Cd)₂(cpota)(H₂cpota)(2,2'-bpy)₂(H₂O)]·2H₂O}_nIn which H is₃cpota is o- (p-carboxyphenyl) oxy terephthalic acid, 2,2'-bpy is 2,2' -bipyridine, and n represents polymerization; it is characterized in that the structural formula is as follows:

the crystal of the cadmium coordination polymer belongs to a monoclinic system, and the space group is

The unit cell parameters are:a = 13.100(4) Å，b = 17.559(6) Å，c = 20.802(7) Å，α = 90°，β = 96.800(1)°，γ= 90 °; two adjacent cadmium atoms are bridged by two carboxylic acid oxygen atoms to form a binuclear cadmium dimer unit.

2. The method of claim 1, wherein the method comprises the steps of:

(1) cd (NO) is added according to the molar ratio of 2:2:1:300-₃)₂·6H₂O, 2' -bipyridine, O- (p-carboxyphenyl) oxyterephthalic acid and water were added to a polytetrafluoroethylene tube and adjusted with 0.5mol/L KOHpH to 5;

(2) placing the polytetrafluoroethylene tube in a stainless steel reaction kettle, reacting for 3 days at 413K, naturally cooling to room temperature to precipitate colorless blocky crystals, washing with water, and vacuum drying.

3. The use of the two-dimensional binuclear cadmium coordination polymer of claim 1 as a chemical sensor for detecting divalent copper ions in water.