CN112480423A

CN112480423A - Metal organic framework complex of semi-rigid tricarboxylic acid, preparation method and application thereof

Info

Publication number: CN112480423A
Application number: CN202011410256.1A
Authority: CN
Inventors: 王艳宁; 王少单; 常雪萍
Original assignee: Xinyang Normal University
Current assignee: Xinyang Normal University
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2021-03-12
Anticipated expiration: 2040-12-03
Also published as: CN112480423B

Abstract

The invention provides a metal organic framework complex of semi-rigid tricarboxylic acid, a preparation method and application thereof, wherein the chemical formula of the complex is [ Zn ]₃(L)₂(H₂O)₂]·3H₂O, ligand L^3‑Is 5- (3, 4-dicarboxyphenoxy) nicotinic acid, and has a molecular formula as follows: c₂₈H₂₂N₂O₁₉Zn₃The complex belongs to a triclinic system, the space group is P ī, and in the space group P ī, an asymmetric unit consists of two independent Zn²⁺Ion, one fully deprotonated L^3‑The ligand and one coordinated water molecule. The complex is to CO₂The complex has high capture performance, and meanwhile, the complex has the advantages of simplicity, convenience, rapidness and high sensitivity when being applied to acac detection.

Description

Metal organic framework complex of semi-rigid tricarboxylic acid, preparation method and application thereof

Technical Field

The invention belongs to the field of transition metal complex materials, and particularly relates to a metal organic framework complex of semi-rigid tricarboxylic acid, a preparation method and application thereof.

Background

Metal Organic Frameworks (MOFs) are a class of highly crystalline inorganic-organic hybrid materials, and have received increasing attention in recent decades due to their novel structures and broad application prospects in gas capture, gas separation, drug delivery, luminescence, iodine adsorption, catalysis, bio-imaging, and other aspects. In many application fields, the luminescent MOFs have the advantages of adjustable structure, high porosity, rich luminescent sources, and diverse detection mechanisms, and are widely studied in the chemical sensing field. In recent years, luminescent MOFs as fluorescent probes show good prospects for detection of environmentally harmful or toxic substances. Compared with other detection technologies, the fluorescent MOFs have the remarkable advantages of high response speed, low cost, convenience in operation, high sensitivity, strong selectivity and the like. Fluorescent MOFs have high sensitivity and selectivity, and can be used for detecting various analytes such as explosives, oxidative pollutants, toxic anions, cations, organic small molecules, biomolecules and the like.

Disclosure of Invention

Based on the above, the invention aims to disclose a metal organic framework complex of semi-rigid tricarboxylic acid, a preparation method and application thereof, wherein the complex has the advantages of simplicity, rapidness and high sensitivity when being applied to detection of acac, and the complex has CO detection sensitivity₂Has higher capture performance.

A metal organic framework complex of semi-rigid tricarboxylic acid, the chemical formula of the complex is [ Zn ]₃(L)₂(H₂O)₂]·3H₂O, ligand L^3-Is 5- (3, 4-dicarboxyphenoxy) nicotinic acid, and has a molecular formula as follows: c₂₈H₂₂N₂O₁₉Zn₃The complex belongs to a triclinic system, and the space group is P ī; in this space group P ī, the asymmetric unit is composed of two independent Zn²⁺Ion, one fully deprotonated L^3-Ligand and one coordinated water molecule, two Zn²⁺The ions are Zn1 ion and Zn2 ion respectively, Zn1 is different from three different L^3-Four carboxylic acid O atoms of the ligand and a fourth L from^3-One pyridine N atom of the molecule coordinates, Zn2 is in a hexa-coordinated octahedral structure consisting of two water molecules with O atoms occupying the equatorial plane and four different L atoms from the equatorial plane^3-Together with the O atom of the carboxylic acid(s); a Zn-O/N bond length of

The bond angle around the Zn atoms is between 57.09 ° and 180.0 °.

In one embodiment, each L^3-Using mu₆-η¹:η²:η¹:η²Coordination mode connecting six Zn²⁺A center, a dihedral angle between two aromatic rings is 83.31 °, and a bond angle of an ether bond is 118.71 °; l is^3-Three carboxyl groups in the (B) adopt three different coordination modes, namely (kappa)¹-κ⁰)-μ₁-COO-，(κ¹-κ¹)-μ₂-COO-and (kappa)¹-κ²)-μ₂-COO-。

In one embodiment, the complex has a three-dimensional supramolecular network structure formed by self-assembly of two-dimensional layers, wherein three Zn²⁺The ion, the O atom of two water molecules, two N atoms and six carboxyl groups form a trinuclear [ Zn ]₃(COO)₆O₂N₂]Cluster, adjacent Zn … Zn distance of

Two-dimensional layer consisting of one cluster and 8L^3-Connection formation; l is^3-The two adjacent phenyl rings and the two adjacent pyridine rings on the ligand molecules have pi … pi interaction, and the two-dimensional layer forms a three-dimensional supramolecular network structure through the pi … pi interaction and self-assembly; the two-dimensional layer has a channel along the a-axis with an aperture of about

Coordinated water molecules form intramolecular hydrogen bonds with adjacent carboxyl O atoms, and the distance of O … O is

In one embodiment, the complex has a fluorescence lifetimeThe service life is as follows: tau is₁＝0.68μs，τ₂＝7.82μs。

The preparation method of the metal-organic framework complex of the semi-rigid tricarboxylic acid comprises the following steps: 10.9mg of 0.05mmol of Zn (AcO)₂·2H₂O, 15.2mg of 0.05mmol of 5- (3, 4-dicarboxyphenoxy) nicotinic acid was dissolved in 8mL of distilled water with 1 mol. L^-1The mixture was transferred to a 20mL stainless steel autoclave lined with teflon, heated at 160 ℃ for 72 hours at constant temperature and cooled to room temperature to obtain colorless massive crystals with a yield of 48% calculated as zn (ii).

The metal-organic framework complex of the semi-rigid tricarboxylic acid is used for CO₂The capture application of (1): at 298K and standard pressure, the complex adsorbs 395cm³ g^-1CO of₂。

The metal organic framework complex of the semi-rigid tricarboxylic acid is applied as a chemical sensor: when the acac concentration is 0-160 mu M, the quenching effect formula of the complex on acac is as follows: i is₀/I＝2.9216×exp(0.0128[acac])-2.1265，R²0.9926, wherein I₀Represents the fluorescence emission intensity of MOF1 in aqueous solution, and I is the fluorescence emission intensity after the acac is added.

The metal organic framework complex of the semi-rigid tricarboxylic acid is applied as a chemical sensor: at acac concentration of 0-35. mu.M, I₀the/I and acac concentration curves conform to the Stern-Volmer equation: i is₀/I＝K_SV[acac]+1, where the Stern-Volmer constant K_SVIs 3.597X 10⁴M^-1，R²＝0.9910。

The metal organic framework complex of the semi-rigid tricarboxylic acid is applied as a chemical sensor: the complex has a detection limit of 50.77ppb for acac.

The selective detection method of acetylacetone by using the metal organic framework complex of the semi-rigid tricarboxylic acid as a chemical sensor comprises the following steps: dispersing a 2mg sample of the ground complex in 2ml of deionized water, and carrying out ultrasonic treatment for 30 minutes to form a stable suspension; respectively and slowly dripping 5 mu L of acetonitrile, methanol, ethanol, isopropanol, n-butanol, dichloromethane, trichloromethane, acetylacetone, dimethylacetamide and ethyl acetate into the 2mL of suspension solution; performing fluorescence detection at an excitation wavelength of 260nm to obtain the luminous intensity of the aqueous solution; the recognition capability of the complex on acac is judged by the luminous intensity.

The invention selects semi-rigid tricarboxylic acid ligand H₃L successfully synthesized a novel metal-organic framework complex (Zn (II) -MOF) material of a semi-rigid tricarboxylic acid. A large number of uncoordinated O atoms exist on the inner wall of the pore channel of the complex, so that the complex shows higher CO₂Performance is captured. In addition, the complex is used as a fluorescent probe, can detect the acac at ppb level in an aqueous solution, and has high sensitivity and good selectivity.

Drawings

Fig. 1 is a schematic diagram of a coordination structure of a complex 1 (hereinafter referred to as MOF 1) in the present embodiment, in which (a) a coordination environment and a coordination geometry of Zn1 ion; (b) coordination environment and coordination geometry of Zn2 ion; (c) l is^3-Coordination patterns in MOF1 (a: x-1, y, z + 1; b: x, y, z + 1; c: -x +2, -y +2, -z; d: x +1, y, z-1; e: x, y, z-1; f: -x +1, -y +2, -z + 1; g: -x +1, -y +2, -z; for the sake of clarity, all hydrogen atoms have been omitted).

FIG. 2 is a schematic diagram of the crystal structure of MOF1 in this example, wherein a) the asymmetric units; (b) [ Zn ]₃(COO)₆O₂N₂]Clustering; (c) two-dimensional layers and one-dimensional channels along the a-axis; (d) a one-dimensional channel viewed from the (111) direction; (e) a three-dimensional supramolecular network of MOF 1.

FIG. 3 is a powder X-ray diffraction (PXRD) pattern of MOF1 in this example.

FIG. 4 is MOF1 and H₃The infrared spectrum of L.

FIG. 5 is a graph of the thermogravimetric profile of MOF 1.

FIG. 6 shows N at 77K for MOF1₂And 298K CO₂Adsorption-desorption isotherms of (a).

FIG. 7a is MOF1 and H₃Solid state photoluminescence spectrum of L ligands.

FIG. 7b is a decay curve of MOF 1.

FIG. 8a is a graph of the luminescence spectra of MOF1 in aqueous solutions of different organic molecules, wherein the fluorescence intensity is normalized with the emission intensity of 2mg of complex 1 in 2ml of pure water, with excitation at a wavelength of 260 nm.

FIG. 8b is the normalized intensity of MOF1 in aqueous solutions of different organic molecules, wherein the fluorescence intensity is normalized with the emission intensity of 2mg of complex 1 in 2ml of pure water, with excitation at a wavelength of 260 nm.

FIG. 9 is the selectivity of MOF1 for acac under interference from other small organic molecule species, where the fluorescence intensity is normalized to the emission intensity of 2mg of MOF1 in 2ml of pure water.

FIG. 10a is the luminescence spectrum of an acac suspension of MOF1 as a function of acac concentration.

FIG. 10b is a graph of I0/I-1 versus acac concentration, with the inset: linear dependence of the curve at low acac concentration.

Fig. 11 is a PXRD pattern of MOF1 soaked in an aqueous solution containing different small organic molecules.

FIG. 12 is a graph of the UV-VIS absorption spectra of different small organic molecules and MOF 1.

FIG. 13 is H₃Electron density profile of L ligand front molecular orbitals.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

1. Metal organic framework complex 1 of semi-rigid tricarboxylic acid (chemical formula [ Zn ])₃(L)₂(H₂O)₂]·3H₂O, hereinafter abbreviated MOF 1):

reduction of Zn (AcO)₂·2H₂O (10.9mg, 0.05mmol), 5- (3, 4-dicarboxyphenoxy) nicotinic acid (H)₃L) (15.2mg, 0.05mmol) was dissolved in distilled water (8mL) and HCl (1 mol. L)^-1) Adjusting pH5, the mixture was transferred to a 20mL stainless steel reaction kettle lined with Teflon and heated at a constant temperature of 160 ℃ for 72 hours. After cooling to room temperature, colorless massive crystals were obtained. The yield was 48% (calculated as Zn (II)). The molecular formula is: c₂₈H₂₂N₂O₁₉Zn₃. Theoretical value of elemental analysis: c37.90, H2.48, N3.16%. Experimental values: c37.74, H2.67, N3.12%. Infrared Spectrum (KBr, cm)^–1):3340w,2362s,1615s,1576s,1471w,1398s,1349m,1307w,1266m,1216w,1152m,982w,844m,796m,675w,456w。

Determining the crystal structure of the MOF 1;

irradiation with Mo-Ka radiation on Bruker D8 QUEST ECO diffractometer

Single crystal data of MOF1 was collected. Adopting SHELTTL program, taking Olex2 as interface, adopting direct method to solve structure, and using SHELXL-2014/7³⁰And (5) performing structure fine trimming. The CCDC number of MOF1 is 2036743. Crystallographic data for MOF1 were finally obtained, see table 1.

TABLE 1 crystallographic data of MOF1

TABLE 2 hydrogen bond length of MOF1

And key angle (°) related parameter

MOF1 belongs to the triclinic P ī space group, and the asymmetric unit is composed of two independent Zn²⁺Ion (Zn1, Zn2), a fully deprotonated L^3-Ligand and one coordinated water molecule (O8) (fig. 2 a). As shown in FIG. 1, Zn1 is associated with a group of three different L^3-Four carboxylic acid O atoms of the ligand (O2d, O3d, O4c and O6) and from the fourth L^3-One pyridine N atom (N1e) of the molecule coordinates, forming a distorted trigonal bipyramidal configuration. Zn2 is in a hexa-coordinated octahedral geometry, consisting of two water molecule O atoms (O8 and O8g) occupying the equatorial plane and four different L's from the equatorial plane^3-The O atoms (O3e, O3f, O5g and O5) of the carboxylic acid(s) together. Zn-O/N bond length

In accordance with the normal range, the bond angle around the Zn atoms is between 57.09 ° and 180.0 °. In MOF1, each L^3-Using mu₆-η¹:η²:η¹:η²Coordination mode (FIG. 1c) linking six Zn²⁺At the center, the dihedral angle between the two aromatic rings was 83.31 °, and the bonding angle of the ether bond was 118.71 °. L is^3-Three carboxyl groups in the (B) adopt three different coordination modes, namely (kappa)¹-κ⁰)-μ₁-COO-,(κ¹-κ¹)-μ₂-COO-and (kappa)¹-κ²)-μ₂-COO-。

MOF1 has a two-dimensional layered structure. First, three Zn²⁺(two Zn1 and one Zn2) ions, two O atoms of water molecules, two N atoms and six carboxyl groups form a trinuclear [ Zn₃(COO)₆O₂N₂]Cluster, adjacent Zn … Zn distance of

(FIG. 2 b). Each cluster is divided into 8L^3-Connected to form a two-dimensional layer. The two-dimensional layer has a channel along the a-axis (FIGS. 2c and 2d) with an aperture of about

The solvent fillable volume was 17.2%. Coordinated water molecules (O8) form intramolecular hydrogen bonds with adjacent carboxyl O atoms (O6), and the distance of O … O is

The two-dimensional layer is made more stable. Furthermore, L^3-The pi … pi interaction exists between two adjacent phenyl rings and two adjacent pyridine rings on a ligand molecule (the distance from the centroid to the centroid is respectively

And

) These pi … pi interactions allow the two-dimensional layers to self-assemble into the final three-dimensional supramolecular network structure (fig. 2 e).

Powder X-ray diffraction (PXRD) analysis of MOF1

MOF1 was subjected to PXRD testing to ensure it was pure phase (fig. 3). The diffraction peak obtained by the experiment is consistent with the simulated diffraction peak obtained by fitting single crystal diffraction data, and the synthesized sample is proved to be pure phase.

Infrared Spectroscopy (IR) analysis of MOF1

FIG. 4 is an infrared spectrum of MOF 1. 3440 3200 cm-^-1The broad infrared absorption band in the range should be attributed to the O-H stretching vibrational peak on the coordinated or crystallized water molecule. 1615cm^-1The strong absorption peak is attributed to asymmetric stretching vibration of the coordinated carboxyl. 1398cm^-1The absorption peak is the symmetric stretching vibration peak of the coordination carboxyl. Further, upsilon_as(C ═ O) and upsilon_sThe band gap (. DELTA.) between (C ═ O) further confirms that the carboxylic acid groups coordinate to the metal atom in a corresponding coordination manner, which is consistent with the crystal structure results. MOF1 at 1730-1685cm^-1Has no absorption, verifies H₄Complete deprotonation of the bptc ligand.

5. Thermal analysis

To investigate the thermal stability of MOF1, the thermo-gravimetric behavior of MOF1 was tested. As shown in fig. 5, MOF1 underwent a weight loss step. The first step weight loss of about 10% occurs before 135 ℃, corresponding to the loss of 3 lattice waters and 2 coordinated water molecules (theoretical 10.15%). The metal-organic framework was stabilized to 425 ℃ and the residue was confirmed to be ZnO (residue content: theoretical 27.54%; experimental value about 28%).

6. Gas adsorption performance

To evaluate the porosity of MOF1, its N at 77K was tested₂Adsorption isotherms. Before measurement, a single crystal of MOF1 is placed in CH₂Cl₂Soaked for 48 hours and then activated under vacuum at 60 ℃ for 4 hours to give desolvated samples. The corresponding adsorption-desorption isotherms are shown in figure 6. The results show that in P/P₀Not less than 0.99, with a small amount of N₂Adsorption (about 10 cm)³g^-1). BET surface area and Langmuir surface area were 8.55m, respectively²G and 33.20m²(g) the average pore diameter reaches 7.18 nm. We also investigated its CO₂Adsorption of (3). As shown in FIG. 6, MOF1 can adsorb a large amount of CO at 298K and standard pressure₂(395cm³g^-1)。CO₂Is greater than N₂Probably, the one-dimensional channels of the MOF1 have relatively high polarity, and a large number of O atoms which do not participate in coordination are arranged on the inner surfaces of the channels. And CO₂Dipole moment and polarization performance ratio of N₂Stronger, so the one-dimensional pore channel is to CO₂Has stronger affinity. In addition, with CO₂

Compared with N₂

Has a larger value of kinetic diameter, thus making it more difficult to diffuse into the pore channels.

7. Optical characteristics

We tested the fluorescence spectra of MOF 1. As shown in FIG. 7(a), MOF1 has an emission peak at 440nm under 235nm excitation light, which is typical of blue light emission. Since the Zn (II) ion has d¹⁰The electronic structure, which is difficult to oxidize or reduce, is therefore subject to both metal-to-ligand charge transfer (MLCT) and ligand-to-metal transfer (LMCT). Therefore, it is probably due to H₃The L ligand has either pi-pi or pi-n charge transitions within the molecule. H₃The emission pattern of the L ligand further confirms our hypothesis. MOF1 vs. H₃L is preparedThe body shows a marked red shift (about 30nm) due to coordination between the metal and the ligand, the carboxyl group coordination to the metal center reducing either the pi-pi or pi-n spacing of the carboxylic acid ligand, resulting in a red shift of the emission peak. Furthermore, the decrease in luminescence intensity may also be the result of the ligand coordinating to the metal center. The coordination of the carboxyl groups to the metal center reduces the rigidity of the ligand, thereby increasing the energy loss due to molecular vibration. In addition, the fluorescence lifetime test of MOF1 shows that the lifetime decay curve accords with a double exponential decay curve, and the lifetime is tau₁＝0.68μs(66.81％),τ₂＝7.82μs(33.19％)(R²＝1.083)。

We also explored the effect of small organic molecules on MOF1 luminescence intensity. A sample of milled MOF 1(2mg) was dispersed in 2ml of deionized water and sonicated for 30 minutes to form a stable suspension. Separately, 5. mu.L of acetonitrile (CH)₃CN), methanol (CH)₃OH), ethanol (EtOH), isopropanol, n-butanol (n-BuOH), dichloromethane (CH)₂Cl₂) Trichloromethane (CHCl)₃) Organic small molecules such as acetylacetone (acac), Dimethylacetamide (DMA), and ethyl acetate (EtOAc) were slowly dropped into the above 2mL of the suspension solution, followed by fluorescence spectrum measurement. As shown in fig. 8, the acac has the most significant quenching effect on the luminescence property of MOF1, while other organic solvents have very small and negligible influence on the luminescence intensity. This result demonstrates that MOF1 can be used as a fluorescent probe to detect acac in aqueous solutions.

In addition, the anti-interference performance of the fluorescent probe plays an important role in practical application. Therefore, we investigated the anti-interference performance of MOF1 as a fluorescent probe for detecting acac in aqueous solution through a series of competition experiments. The acac solution is added into the aqueous solution containing other organic small molecules with 10 times of equivalent (figure 9), and the fluorescence test result shows that the luminescence quenching effect of the acac is not obviously changed in the mixed organic small molecules, which indicates that the MOF1 has higher selectivity to the acac.

Furthermore, to evaluate the detection limit of MOF1 as a fluorescent probe for detecting acac, we performed titration experiments. As shown in FIG. 10a, as acac was addedThe increase of the MOF1 fluorescence intensity is gradually reduced, which shows that the MOF1 has good sensing sensitivity to acac. Quenching Effect (I)₀I) and acac concentration ([ acac)]) The correlation of (c) is shown in fig. 10 b. When the acac concentration is in the range of 0-160. mu.M, it is in accordance with I₀/I＝2.9216×exp(0.0128[acac])-2.1265(R²0.9926) formula, wherein I₀Represents the fluorescence emission intensity of MOF1 in aqueous solution, and I is the fluorescence emission intensity after the acac is added. At lower concentrations (0-35. mu.M), I₀the/I and acac concentration curves conform to the Stern-Volmer equation: i is₀/I＝K_SV[acac]+1, where the Stern-Volmer constant K_SVIs 3.597X 10⁴M^-1(R²0.9910) (inset of fig. 10 b). According to 3 sigma/K_SV(sigma 10 blank signal standard deviations; K_SVSlope), calculated to have a MOF1 to acac detection limit of 50.77 ppb. We examined the limit of detection of ACAC by MOF1 and K_SVThe values were compared with the values reported in the literature (Table 3), and it can be seen that the detection limit of ACAC and K are determined by MOF1_SVThe values are not much different from the effect of the literature and are lower than the detection limit of the existing literature.

TABLE 3 comparison of the literature-reported fluorescent probes for acac detection with MOF 1.

8. Quenching mechanism study

We performed systematic analysis of the fluorescence sensing mechanism of acac for MOF 1: (i) the stability of MOF1 was demonstrated by the high consistency of PXRD patterns of MOF1 soaked in aqueous solutions containing different small organic molecules (fig. 11). Therefore, the mechanism of fluorescence quenching due to the decomposition or collapse of the crystal structure can be excluded; (ii) the UV-visible absorption spectra of acac (230-12). Namely, acac may reduce the absorption of photons by MOF1, thereby affecting energy conversion, and finally generating fluorescence quenching effect; (iii) generally, if the Lowest Unoccupied Molecular Orbital (LUMO) of the electron-rich framework has a higher energy level than the analyte, there may be electron transfer between the probe and the analyte. Therefore, we have carried out DFT theoretical calculation, and the calculation result shows that H₃The LUMO energy (-1.96eV, FIG. 13) of the L ligand was higher than that of acac (-2.36eV)³³Thus confirming the existence of an electron transfer mechanism; (iv) the acac molecule is due to the isomerism between keto-enol, so we speculate that the-OH moiety of the acac enol form may react with H₃Hydrogen bonding interactions may exist between the non-coordinating oxygen atoms of the L ligands, which may affect the electron transfer path of MOF1 to some extent, thereby facilitating fluorescence quenching. In summary, competitive absorption of excitation light, photo-induced electron transfer and hydrogen bonding interaction between acac and MOF1 may be the main reasons for fluorescence quenching.

In summary, we chose the semi-rigid tricarboxylic acid ligand H₃L successfully synthesized a novel example of Zn (II) -MOF material. The MOF1 material exhibits a high CO₂The trapping performance is related to the existence of a large amount of uncoordinated O atoms on the inner wall of the material pore channel. In addition, the MOF1 can be used as a fluorescent probe for detecting ppb level acac in an aqueous solution, and has high sensitivity and good selectivity. We firmly believe that the research results will play a certain role in promoting the design and development of multifunctional MOFs materials based on semi-rigid polycarboxylic acid ligands.

The above examples only express embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A metal-organic framework complex of a semi-rigid tricarboxylic acid, characterized in thatThen, the chemical formula of the complex is [ Zn ]₃(L)₂(H₂O)₂]·3H₂O, ligand L^3-Is 5- (3, 4-dicarboxyphenoxy) nicotinic acid, and has a molecular formula as follows: c₂₈H₂₂N₂O₁₉Zn₃The complex belongs to a triclinic system, and the space group is P ī; in this space group P ī, the asymmetric unit is composed of two independent Zn²⁺Ion, one fully deprotonated L^3-Ligand and one coordinated water molecule, two Zn²⁺The ions are Zn1 ion and Zn2 ion respectively, Zn1 is different from three different L^3-Four carboxylic acid O atoms of the ligand and a fourth L from^3-One pyridine N atom of the molecule coordinates, Zn2 is in a hexa-coordinated octahedral structure consisting of two water molecules with O atoms occupying the equatorial plane and four different L atoms from the equatorial plane^3-Together with the O atom of the carboxylic acid(s); a Zn-O/N bond length of

The bond angle around the Zn atoms is between 57.09 ° and 180.0 °.

2. A metal-organic framework complex of a semi-rigid tricarboxylic acid of claim 1 wherein each L^3-Using mu₆-η¹:η²:η¹:η²Coordination mode connecting six Zn²⁺A center, a dihedral angle between two aromatic rings is 83.31 °, and a bond angle of an ether bond is 118.71 °; l is^3-Three carboxyl groups in the (B) adopt three different coordination modes, namely (kappa)¹-κ⁰)-μ₁-COO-，(κ¹-κ¹)-μ₂-COO-and (kappa)¹-κ²)-μ₂-COO-。

3. A metal-organic framework complex of a semi-rigid tricarboxylic acid of claim 1 wherein the complex is a complex having a structure consisting ofThree-dimensional supermolecular network structure formed by self-assembly of two-dimensional layers, in which three Zn²⁺The ion, the O atom of two water molecules, two N atoms and six carboxyl groups form a trinuclear [ Zn ]₃(COO)₆O₂N₂]Cluster, adjacent Zn … Zn distance of

4. The metal-organic framework complex of a semi-rigid tricarboxylic acid of claim 1, 2, or 3, wherein the fluorescence lifetime of the complex is: tau is₁＝0.68μs，τ₂＝7.82μs。

5. The method of preparing a metal-organic framework complex of a semi-rigid tricarboxylic acid of claim 1 comprising the steps of: 10.9mg of 0.05mmol of Zn (AcO)₂·2H₂O, 15.2mg of 0.05mmol of 5- (3, 4-dicarboxyphenoxy) nicotinic acid was dissolved in 8mL of distilled water with 1 mol. L^-1The mixture was transferred to a 20mL stainless steel autoclave lined with teflon, heated at 160 ℃ for 72 hours at constant temperature and cooled to room temperature to obtain colorless massive crystals with a yield of 48% calculated as zn (ii).

6. Claim 1-3.5 the metal-organic skeleton complex of a semi-rigid tricarboxylic acid for CO₂Characterized in that the complex adsorbs 395cm at 298K and standard pressure³ g^-1CO of₂。

7. Use of a metal-organic framework complex of a semi-rigid tricarboxylic acid according to any one of claims 1 to 3, 5 as a chemical sensor, wherein: when the acac concentration is 0-160 mu M, the quenching effect formula of the complex on acac is as follows: i is₀/I＝2.9216×exp(0.0128[acac])-2.1265，R²0.9926, wherein I₀Represents the fluorescence emission intensity of MOF1 in aqueous solution, and I is the fluorescence emission intensity after the acac is added.

8. Use of a metal-organic framework complex of a semi-rigid tricarboxylic acid according to claims 1-3, 5 as a chemical sensor wherein I is at acac concentration of 0-35 μ M₀the/I and acac concentration curves conform to the Stern-Volmer equation: i is₀/I＝K_SV[acac]+1, where the Stern-Volmer constant K_SVIs 3.597X 10⁴M^-1，R²＝0.9910。

9. Use of a metal-organic framework complex of a semi-rigid tricarboxylic acid according to claims 1-3, 5 as a chemical sensor, wherein: the complex has a detection limit of 50.77ppb for acac.

10. The method for selectively detecting acetylacetone using the metal-organic skeleton complex of a semi-rigid tricarboxylic acid as defined in claims 1-3 and 5 as a chemical sensor is as follows: dispersing a 2mg sample of the ground complex in 2ml of deionized water, and carrying out ultrasonic treatment for 30 minutes to form a stable suspension; respectively and slowly dripping 5 mu L of acetonitrile, methanol, ethanol, isopropanol, n-butanol, dichloromethane, trichloromethane, acetylacetone, dimethylacetamide and ethyl acetate into the 2mL of suspension solution; performing fluorescence detection at an excitation wavelength of 260nm to obtain the luminous intensity of the aqueous solution; the recognition capability of the complex on acac is judged by the luminous intensity.