A thorium-based complex, a preparation method thereof, and applications thereof in fluorescence detection and separation of light hydrocarbons

Abstract

A thorium-based complex, a preparation method thereof, and applications thereof in fluorescence detection and separation of light hydrocarbons, belonging to the technical field of complexes. The chemical general formula of the thorium-based complex is [Th6O4(OH)4(BTDC)6], where Th is a tetravalent thorium ion and BTDC is a deprotonated 4,7-dicarboxy-2,1,3-benzothiadiazole ligand; the structure of the thorium-based complex belongs to the cubic crystal system, space group Fm-3m, its unit cell parameters are the axial length #imgabs0# the axial angles α = β = γ = 90°, the unit cell volume is #imgabs1# Z = 192. The thorium-based complex described in the present invention is a metal-organic framework structure, which can be used to prepare adsorption materials, antibacterial materials, catalytic materials, photo-electromagnetic materials and drug carrier materials, and is a composite functional porous material with great potential, and can be applied to the fields of fluorescence detection and separation of light hydrocarbon gases.

Description

Technical Field

[0001] The present invention belongs to the technical field of coordination compounds, and particularly relates to a thorium-based coordination compound, a preparation method thereof, and applications thereof in fluorescence detection and separation of light hydrocarbons. Background Art

[0002] Metal-organic frameworks (MOF for short) are assembled from organic ligands or organic bridging groups containing special coordinating atoms or coordinating functional groups and metals on the basis of behaviors such as molecular recognition and self-assembly. Their regular periodic structure, large specific surface area and porosity have made them a research hotspot in the fields of chemistry and materials, so that MOF has great application prospects in many fields such as gas adsorption, fluorescence probes, drug release, etc. In addition, MOF can be modified by chemical methods to change the structure and properties of the material, and is designed and synthesized at the molecular level, which is a kind of composite functional porous material with great potential.

[0003] So far, thorium (Th)-containing metal-organic complexes have diverse structures due to the high valence state and variable coordination ability of Th(IV), thus exhibiting various properties and functions, and having great application prospects in catalytic chemistry, materials science and other aspects. In recent years, many literatures have reported the synthesis methods and applications of thorium metal complexes. Most of the reported ones are MOFs assembled from thorium ions and polycarboxylic acid ligands. For example, Na Zhang, Li-Xian Sun, Feng-Ying Bai, Yong-Heng Xing, Inorg. Chem. 2020, 59(6), pp3964–3973 selected a polycarboxylic acid ligand 1,3,5-triazine-2,4,6-triamine hexaacetic acid to construct a hexanuclear thorium complex for the adsorption of elemental iodine; Sara E. Gilson, Melissa Fairley, Patrick Julien, Allen G. Oliver, Sylvia L. Hanna, Grace Arntz, Omar K. Farha, Jay A. LaVerne, Peter C. Burns, J. Am. Chem. Soc. 2020, 142(31), pp 13299–13304 selected 2,2′-dihydroxy-[1,1′-binaphthalene]-5,5′-dicarboxylic acid to construct a hexanuclear thorium complex to study its radiation resistance; Zhenzhen Xu, Xiaohong Xiong, Jianbo Xiong, Rajamani Krishna, Libo Li, Yaling Fan, Feng Luo, Banglin Chen, Nat. Commun. 2020, 11, 3163 selected 4-(1H-tetrazol-5-yl)benzoic acid to construct a hexanuclear thorium complex for C 2 H 4 Purification.

[0004] The ligands used to construct the above thorium complexes are all nitrogen-containing, hydroxyl-containing or simple aromatic carboxylic acid ligands. It has never been reported that a rigid aromatic carboxylic acid ligand 4,7-dicarboxy-2,1,3-benzothiadiazole (H 2 BTDC) and thorium nitrate hexahydrate are used to construct a thorium-based complex, thus lacking a thorium-based complex with composite functions. Summary of the Invention

[0005] In order to solve the technical problems existing in the above background technology, the purpose of the present invention is to provide a thorium-based complex with composite functions, a preparation method thereof, and its applications in fluorescence detection and light hydrocarbon separation.

[0006] A thorium-based complex according to the present invention has a general chemical formula of [Th 6 O 4 (OH) 4 (BTDC) 6 , where Th is a tetravalent thorium ion and BTDC is a deprotonated 4,7-dicarboxy-2,1,3-benzothiadiazole ligand.

[0007] The beneficial effect of the present invention is that the thorium-based complex described in the present invention belongs to a metal-organic framework structure and is a composite functional porous material with great potential, which can be used to prepare adsorption materials, antibacterial materials, catalytic materials, photo-electromagnetic materials and drug carrier materials.

[0008] The crystal structure of the thorium-based complex described in the present invention was tested with an Agilent SuperNova microfocus X-ray single crystal diffractometer at 150 K, and data was collected on an EosCCD. Using a graphite monochromator, λ(Cu Kα) is In a variable angular scan mode of ω-2θ, the CrysAlisPro tool was used for data analysis and absorption correction. All structures were directly solved using the SHELXS program encapsulated in SHELXTL, and structure refinement was performed using SHELXL full matrix least squares method. Anisotropic treatment was performed on all non-hydrogen atoms, and the hydrogen atoms of the organic ligands were generated by geometric symmetry It was determined that the structure of the thorium-based complex described in the present invention belongs to the cubic crystal system, the Fm-3m space group, and its unit cell parameters are the axial length The axial angles α = β = γ = 90°, the unit cell volume is Z = 192; the basic structural unit of the crystal is obtained by symmetry operation of the asymmetric unit, and the symmetry operation codes are 1 +X, 1-Z, +Y; 2 +X, 1-Y, 1-Z; 3 +X, +Z, 1-Y; 4 1-Y, +X, +Z; 5 1-Z, +Y, +X; 6 1-Y, +Z, 1-X; 7 1-Z, +X, 1-Y; 8 1-Z, 1-Y, 1-X; 9 1 / 2 + Z, 1-Y, -1 / 2 + X.

[0009] The asymmetric unit consists of a quarter of a deprotonated ligand BTDC, an eighth of a thorium ion, and a sixth of a coordinated μ 3-Hydroxyl / oxygen atoms. The thorium ion adopts an eight-coordination mode and is connected to eight oxygen atoms, which are respectively from the oxygen atoms (O2) in the four carboxylate groups (O2-C1-O2) of four different ligands BTDC, and four come from the coordinated μ 3 -Hydroxyl / oxygen atom (O1); the carboxylate group (O2-C1-O2) in the ligand adopts a bidentate bridging mode to connect adjacent Th ions, and finally a hexanuclear Th 6 O 4 (OH) 4 (COO) 12 Structure.

[0010] The present invention also provides a preparation method of the thorium-based complex, and the steps are as follows:

[0011] A. Dissolve the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand and thorium nitrate hexahydrate in a solvent to obtain a homogeneous mixed solution. The molar dosage ratio of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand to thorium nitrate hexahydrate is 1:1 to 2, and the concentration of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand in the mixed solution is 0.015 to 0.025 mmol / L;

[0012] B. Keep the mixed solution obtained in step A at 140-160 °C for 40-60 h to obtain the thorium-based complex.

[0013] The beneficial effects of the present invention are: the conditions of this preparation method are simple, the reaction can proceed rapidly, energy is saved, and time is saved. Moreover, the preparation method of the thorium-based complex of the present invention has a high yield, less ligand consumption, and cost savings.

[0014] Further, the solvent consists of N,N-dimethylformamide and hydrochloric acid, and the volume ratio of N,N-dimethylformamide to hydrochloric acid is 6:1.

[0015] The beneficial effect of adopting the above further scheme is that the solvent composed of N,N-dimethylformamide and hydrochloric acid is easy to obtain, low in price, and less polluting.

[0016] Further, the molar dosage ratio of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand to the thorium nitrate hexahydrate is 1:1.5, and the concentration of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand is 0.02 mmol / L.

[0017] The beneficial effect of adopting the above further scheme is that the thorium-based complex obtained with the determined concentration and molar dosage ratio has better quality and the reaction is more smooth.

[0018] The present invention also provides an application of a thorium-based complex in the field of fluorescence detection. The thorium-based complex is dissolved in a solvent to be detected as a fluorescent material, and then the fluorescence intensity is detected by a fluorescence spectrometer to achieve fluorescence detection.

[0019] The beneficial effect of the present invention is that the thorium-based complex can be applied to fluorescence detection, making the functions of the thorium-based complex more comprehensive.

[0020] The present invention also provides an application of a thorium-based complex in the field of low-carbon hydrocarbon gas separation. The thorium-based complex is used to perform adsorption tests on single-component CO 2 , CH 4 , C 2 H 2 , C 2 H 4 , and C 2 H 6 to obtain differential adsorption amounts for adsorption separation.

[0021] The beneficial effect of the present invention is that the thorium-based complex is applied to the field of low-carbon hydrocarbon gas separation, making the functions of the thorium-based complex more comprehensive. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of an asymmetric structural unit of the thorium-based complex of the present invention;

[0023] Figure 2 is a schematic structural diagram of the thorium-based complex of the present invention;

[0024] Figure 3 is a thermogravimetric curve of the thorium-based complex of the present invention, where the abscissa is temperature and the ordinate is the percentage of weight loss;

[0025] Figure 4 is an infrared spectrum of the thorium-based complex of the present invention, where the abscissa is wave number and the ordinate is transmittance;

[0026] Figure 5 is a solid-state fluorescence spectrum of the thorium-based complex of the present invention, where the abscissa is wavelength and the ordinate is intensity;

[0027] Figure 6 is an adsorption isotherm diagram of the thorium-based complex of the present invention for CO 2 , CH 4 , C 2 H 2 , C 2 H 4 , and C 2 H 6 at 273K, where the abscissa is pressure and the ordinate is adsorption amount;

[0028] Figure 7For the thorium-based complex of the present invention, the adsorption isotherm diagrams for CO 2 , CH 4 , C 2 H 2 , C 2 H 4 and C 2 H 6 are shown. The abscissa is pressure and the ordinate is the adsorption amount. Detailed implementation mode

[0029] The principle and characteristics of the present invention will be described in detail below in conjunction with the embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0030] Example 1:

[0031] A preparation method of a thorium-based complex specifically includes the following steps:

[0032] A. Accurately weigh 0.011 g (0.05 mmol) of 4,7-dicarboxy-2,1,3-benzothiadiazole (H 2 BTDC) ligand and 0.044 g (0.075 mmol) of thorium nitrate hexahydrate in a reaction vessel. At room temperature, add 2.5 mL of a mixed solvent composed of N,N-dimethylformamide and hydrochloric acid to the reaction vessel, and the volume ratio of N,N-dimethylformamide to hydrochloric acid is 6:1;

[0033] B. Place the mixed solution in step A in a glass bottle and keep it warm in a constant temperature blast oven at 150 °C for 48 h to obtain a thorium-based complex in the form of red-brown crystals.

[0034] The obtained red-brown crystal-like thorium-based complex was tested at 150 K using a SuperNova microfocus X-ray single crystal diffractometer from Agilent Technologies, and data was received on an Eos CCD. Using a graphite monochromator, λ(Cu Kα) is In the ω-2θ variable-speed arbitrary angle scanning mode, the CrysAlisPro tool was used for data analysis and absorption correction. All structures were directly solved using the SHELXS program encapsulated in SHELXTL, and structure refinement was performed using the SHELXL full matrix least squares method. Anisotropic treatment was performed on all non-hydrogen atoms, and the hydrogen atoms of the organic ligand were generated by geometric symmetry to obtain the crystal data shown in Table 1, the typical bond length data of the crystal shown in Table 2, and the typical bond angle data of the crystal shown in Table 3.

[0035] Table 1: Crystal data

[0036]

[0037]

[0038] Table 2: Typical bond length data of the crystal (unit: )

[0039] Th1 O2 2.457(17) Th1 <![CDATA[O2 1 > 2.457(17) Th1 <![CDATA[O2 2 > 2.457(17) Th1 <![CDATA[O2 3 > 2.457(17) Th1 <![CDATA[O1 4 > 2.388(18) Th1 <![CDATA[O1 5 > 2.388(18) Th1 <![CDATA[O1 6 > 2.388(18) Th1 <![CDATA[O1 7 > 2.388(18)

[0040] Table 3: Typical bond angle data of the crystal (unit: °)

[0041]

[0042]

[0043] Combining the crystal data in Table 1, Table 2 and Table 3, the following characterizations of the thorium-based complex are obtained:

[0044] As Figure 1 shown, the asymmetric unit consists of one-quarter of a deprotonated ligand BTDC, one-eighth of a thorium ion, and one-sixth of a coordinated μ 3 -hydroxy / oxygen atom.

[0045] As Figure 2 shown, the thorium ion adopts an eight-coordination mode and is connected to eight oxygen atoms, and these eight oxygen atoms are respectively the oxygen atoms (O2) in the four carboxylate groups (O2-C1-O2) from four different ligands, and four oxygen atoms (O1) from the coordinated μ 3 -hydroxy / oxygen atom;

[0046] The carboxylate group (O2-C1-O2) in the ligand adopts a bidentate bridging mode to connect adjacent Th ions, and finally forms a hexanuclear Th 6 O 4 (OH) 4 (COO) 12 structure. Its unit cell parameters are the axial length axial angles α = β = γ = 90°, the unit cell volume is Z = 192.

[0047] The structure of the thorium-based complex of the present invention belongs to the cubic crystal system, the Fm-3m space group, H 2 All the carboxyl groups in BTDC are deprotonated and adopt a bidentate bridging mode to connect adjacent Th ions. The Th ions are bridged by carboxylic acid oxygen bridges and μ 3 -hydroxy / oxygen bridges to form a hexanuclear secondary structure unit, and adjacent secondary structure units are connected by two carboxyl groups of the ligand.

[0048] As Figure 3As shown, the red-brown crystalline thorium-based complex was subjected to thermogravimetric curve analysis. The thermogravimetric test was carried out on a Mettler synchronous thermogravimetric analyzer, model RGA / DSC-1. The reaction gas and the protective gas were both nitrogen, with flow rates of 25 mL / min respectively. The running time was 50 minutes, the heating rate was 10 °C / min, and the test temperature range was 40 - 900 °C. From Figure 3 the thermogravimetric curve, we can know that the thorium-based complex can be stable up to about 500 °C; the coordinated solvent in the system is lost by the complex at 150 °C, and the weight loss from 150 °C to 300 °C is due to partial decomposition of the ligand. The thorium-based complex decomposes after 500 °C. This shows that the thorium-based complex of the present invention has good stability and can decompose at high temperatures.

[0049] As Figure 4 shown, the red-brown crystalline thorium-based complex was detected by infrared spectroscopy. The infrared test used the KBr tablet method, and the infrared spectrum in the range of 4000 - 400 cm -1 was collected on a Nicolet 330 FTIR spectrometer. From Figure 4 it can be seen that the absorption peak near 3400 cm -1 in the complex can be attributed to the O-H stretching vibration peak of water, and the absorption peaks near 1690 - 1605 cm -1 and 1440 - 1330 cm -1 can be respectively attributed to the antisymmetric and symmetric stretching vibration peaks of the carboxylate group.

[0050] As Figure 5 shown, the red-brown crystalline thorium-based complex was tested on an F-7000 type fluorescence spectrophotometer with an excitation wavelength of 330 nm to obtain a solid-state fluorescence spectrum diagram. From Figure 5 it can be known that when the incident and emission slits are 10 nm and 20 nm respectively, and the emission wavelength is 330 nm, the excitation wavelength of this thorium-based complex is near 439 nm. The H 2 BTDC ligand has strong fluorescence at 505 nm. Compared with the fluorescence characteristic peak of the H 2 BTDC ligand, the fluorescence characteristic peak of the thorium-based complex is shifted forward by 66 nm. This shows that the present thorium-based complex has strong fluorescence at 439 nm and can be applied to the field of fluorescence detection.

[0051] As Figure 6 and Figure 7 shown, the red-brown crystalline thorium-based complex was tested by an ASAP2020 instrument of Micromeritics, USA. The thorium-based complex was tested for single-component CO 2 , CH 4 , C 2 H 2 , C 2 H4 and C 2 H 6 exhibits the adsorption isotherm as shown in the figure. The adsorption amounts of CO 2 , CH 4 , C 2 H 2 , C 2 H 4 and C 2 H 6 at 273 K are 41.7 cm 3 / g, 25.4 cm 3 / g, 50.2 cm 3 / g, 53.7 cm 3 / g and 50.8 cm 3 / g respectively. The adsorption amounts of CO 2 , CH 4 , C 2 H 2 , C 2 H 4 and C 2 H 6 at 298 K are 34.4 cm 3 / g, 16.1 cm 3 / g, 42.4 cm 3 / g, 44.3 cm 3 / g and 40.8 cm 3 / g respectively. Therefore, from the differentiated adsorption amounts in the figure, it can be known that the thorium-based complex can be applied to the field of gas adsorption and separation.

[0052] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A thorium-based complex, characterized in that: Its chemical general formula is [Th 6 O 4 (OH) 4 (BTDC) 6 , where Th is a tetravalent thorium ion and BTDC is a deprotonated 4,7-dicarboxy-2,1,3-benzothiadiazole ligand; this thorium-based complex belongs to the cubic crystal system, space group Fm-3m, and its unit cell parameters are the axial lengths a = b = c = 22.0425(3) Å, axial angles α = β = γ = 90°, and the unit cell volume is 10709.8(4) Å 3 , Z = 192.

2. A preparation method of the thorium-based complex according to claim 1, comprising the following steps: A. Dissolve the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand and thorium nitrate hexahydrate in a solvent to obtain a homogeneous mixed solution. The molar ratio of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand to thorium nitrate hexahydrate is 1:1 to 2, and the concentration of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand in the mixed solution is 0.015 to 0.025 mmol / L; the solvent consists of N,N-dimethylformamide and hydrochloric acid, and the volume ratio of N,N-dimethylformamide to hydrochloric acid is 6:1; B. Keep the mixed solution in step A at 140 to 160 °C for 40 to 60 h to obtain the thorium-based complex.

3. The preparation method of a thorium-based complex according to claim 2, characterized in that: The molar ratio of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand to thorium nitrate hexahydrate is 1:1.5, and the concentration of the 4,7-dicarboxy-2,1,3-benzothiadiazole ligand is 0.02 mmol / L.

4. Application of the thorium-based complex according to claim 1 in fluorescence detection.

5. Application of the thorium-based complex according to claim 1 in separation of light hydrocarbons.

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