Preparation method of two column layer zinc-based complexes and low-carbon hydrocarbon separation application of two column layer zinc-based complexes

Abstract

The invention belongs to the technical field of new materials, and particularly relates to two zinc-based complexes as well as a preparation method and application thereof. The chemical general formulas are respectively [Zn2 (TMTA) (COO) (BPA) 2] n (UPC-198) and [Zn2 (TMTA) (COO) (BPE) 2] n (UPC-199), Zn is a divalent zinc ion, TMTA is a deprotonated 4, 4 ', 4' '-(2, 4, 6-triphenyl-1, 3, 5) tribenzoic acid ligand, BPA is 1, 2-bis (4-pyridyl) ethane, and BPE is 1, 2-bis (4-pyridyl) ethylene. Wherein the structure of the zinc-based complex belongs to a triclinic system and a P-1 space group, and the unit cell parameters of UPC-198 are as follows: the axial length # imgabs 0 #, the axial angle alpha is equal to 69.247 (3), the beta is equal to 88.215 (3), the gamma is equal to 68.462 (3), and the unit cell volume # imgabs 1 # Z is equal to 35. The unit cell parameters of the UPC-199 are as follows: the axial length # imgabs2 #, the axial angle alpha is equal to 69.029 (3), the beta is equal to 88.481 (3), the gamma is equal to 68.694 (4), and the unit cell volume # imgabs3 # Z is equal to 35. The zinc-based complex can be used for preparing an adsorption material, an antibacterial material, a catalytic material, a photoelectromagnetic material and a drug carrier material, belongs to a metal-organic framework structure, and is a composite functional porous material with great potential. The zinc-based complex can be applied to the field of low-carbon hydrocarbon gas separation.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, and specifically relates to a preparation method of two kinds of pillar-layered structure zinc-based complexes and their application in low-carbon hydrocarbon separation. Background Art

[0002] Gas separation and purification are very important industrial processes in the manufacture of products such as chemicals, fuels, plastics, etc. Taking ethylene (C2H4) and propylene (C3H6) as examples, they are the most demanded and important basic raw materials in the petrochemical industry, and are widely used in the manufacture of high-value organic chemicals. There are many types of related downstream products, which are applied to many fields closely related to production and life, including agriculture, packaging, construction, textiles, electronics and electrical appliances, automobiles, etc., and the product scale accounts for more than 75% of the total global petrochemical products. In the chemical industry, the separation system is a major energy consumer. Traditional cryogenic distillation belongs to a heat-driven energy-intensive process, which requires a large amount of energy and has extremely high requirements for equipment (high temperature, high pressure). During the separation process, the gas mixture will first be condensed into a liquid, and then separated according to the boiling point differences of different components. However, hydrocarbons with the same number of carbon atoms have similar boiling points. In order to meet the purity requirements, the rectification method has very high process control requirements in operation and the entire process has high energy consumption. In industrial production, multiple large distillation towers and extremely high reflux ratios are often required to achieve effective separation. The energy consumption of separating ethylene by conventional cryogenic rectification method is about 21.84 kJ·mol -1 −1, and the total energy consumption can reach more than 0.3% of the global energy consumption. Compared with traditional cryogenic distillation technology, adsorption separation through porous solid adsorbents under normal temperature and pressure conditions has potential advantages in terms of energy consumption, reproducibility and cost. The separation process does not involve phase change, so it is proposed as a potential alternative and complementary separation technology.

[0003] Since molecular sieves were synthesized in 1940, a variety of porous solid adsorbents have emerged, such as molecular sieves, activated carbon, silica gel and resins, etc., and the adsorption separation technology has also developed greatly. Due to its low cost and energy consumption, this separation technology has attracted people's attention. This technology uses a solid separation medium, which usually has pores smaller than 0.5 nm and has large internal pores and specific surface area (>300 m 2 ·g -1) are made of porous solid adsorbents or separation membranes. These materials have a high porosity and a large specific surface area, which is conducive to the transport and adsorption of gas molecules at the gas-solid interface. The physical and chemical microenvironment composed of their pore structure and surface functional groups determines their selectivity differences for different gases. Therefore, by regulating the pore structure of the adsorption material, highly selective adsorption for specific hydrocarbon components can be achieved, thereby achieving the separation of different hydrocarbon mixtures. However, due to the uneven pore size of these conventional adsorption materials, the separation effect for olefin gases with similar molecular structures is not ideal. For example, although activated carbon materials have rich surface functional groups, because their pore distribution ranges from 1 to 10,000 nm, they cannot effectively selectively separate hydrocarbons with the same carbon number with very small molecular differences. The separation of light hydrocarbons through traditional pore solid adsorbents has not been achieved yet

[0004] Among many porous materials, MOF materials have developed into a new generation of functional materials due to their high porosity / specific surface area, diverse pore channels, and designable and tailorable frameworks, showing unique advantages in the direction of gas adsorption and separation. Since the inventor and founder of MOF materials, Yaghi, first proposed the concept of MOF in 1995, in the following more than twenty years, MOF materials have gradually moved from the laboratory to industrialization, and the application of such crystalline porous materials in the field of gas separation has also developed to a new level. The characteristics of high selectivity, high-efficiency separation, and recyclability of MOF materials in gas separation all conform to the concept of green environmental protection and sustainable development. Compared with traditional adsorption materials, MOF materials have obvious advantages: (1) MOF has an ultra-high specific surface area and is easy to obtain an ultra-high adsorption capacity; (2) By selecting appropriate organic components and inorganic components for orderly combination, the structure of MOF can be pre-designed. Since the choice of ligand and metal salt combination is infinite, theoretically, the number of MOF structures that can be designed is also infinite; (3) By designing and modifying ligands and metal clusters, specific adsorption sites can be provided, precisely regulating the pore size and pore environment, and enhancing the interaction between the framework and specific gas molecules; (4) Flexible MOFs that can make dynamic responses with external stimuli such as temperature, pressure, and guest molecules are expected to achieve ideal separation through the "gate effect"; (5) With a clear periodic crystal structure, it is conducive to studying the adsorption and separation mechanism at the molecular level, clarifying the relationship between structure and performance, and providing an accurate theoretical basis for the design and synthesis of subsequent materials; (6) It can be recycled and has a high material utilization rate. Researchers are committed to using various means to regulate the interaction between gas molecules and the framework, thereby improving the gas adsorption capacity of MOF materials.

[0005] C2H4 is one of the core materials in the petrochemical field, and the level of its production can reflect the pros and cons of a country's petrochemical production level. Its downstream products such as polyethylene play a crucial role in the entire petrochemical industry. C2H4 is mainly used to manufacture synthetic rubber, synthetic resins, synthetic fibers, plastics, and various basic organic raw materials such as ethanol, acetaldehyde, acetic acid, and ethylene oxide, which are closely related to our lives. In recent years, with the rapid development of emerging industries represented by lithium batteries, the demand in emerging fields such as high-end polyolefin materials, electronic chemicals, and high-performance engineering plastics has continuously promoted the rapid growth of C2H4 consumption in recent years. C2H2 is mainly obtained through steam cracking of naphtha or C2H6, but this process inevitably produces various gaseous by-products. Among them, the content of C2H2 usually accounts for about 1% of the mixture. The presence of C2H2 not only significantly increases the explosion risk but also causes the inactivation of the catalyst during the ethylene polymerization process. Therefore, the efficient removal of acetylene from ethylene is a crucial industrial process in chemical production.

[0006] To date, many examples of MOFs for C2H2 / C2H4 separation have been reported. In recent years, many literatures have reported the synthesis methods of MOFs and their applications in C2H2 / C2H4 separation. In 2015, Tong-Liang Hu, Hailong Wang, Bin Li, Nat. Commun. 2015, 7, pp 7328 reacted an amino-tetrazole-derived carboxylic acid ligand with Cu to obtain a bifunctional MOF material UTSA-100a. The paddle-wheel-shaped binuclear copper is coordinated and connected with tetrazole to form a framework with an apo topology and one-dimensional pores. The limiting size of the pores for guest molecules to enter in this framework is exactly between the and molecular dynamic diameters of C2H4 and C2H2, and the separation of C2H4 and C2H2 can be achieved by sieving; in 2018, Libo Li, Hui-Min Wen, Chaohui He, Angew. Chem. Int. Ed. 2018, 57, pp 15183 - 15188 reported an ideal molecular sieve structure UTSA-200a for separating C2H2 / C2H4. Through extremely precise structure regulation, the pore diameter is controlled within 3 ·cm -3(0.01 bar, 298 K). This material perfectly solves the problem of the incompatibility between adsorption capacity and selectivity, and establishes a new benchmark for adsorption capacity and selectivity. In 2022, Xiao-Wen Gu, Jia-Xin Wang, Enyu Wu, J. Am. Chem. Soc. 2022, 144, pp 2614-2623 synthesized UiO-67-(NH2)2 by introducing -NH2 functional sites on the inert pore surface of UiO-67. This strategy not only divides the large pores into smaller cage-like pockets, but also modifies new binding sites, enhancing the adsorption capacity for C2H2.

[0007] The above-mentioned construction of complexes has been proven to be able to separate C2H2 and C2H4 through the molecular sieve mechanism and thermodynamic driving force. However, the development of highly efficient C2H2 / C2H4 separation MOFs with both high adsorption capacity and high selectivity remains a challenge. Some MOFs with larger pore sizes exhibit higher adsorption amounts, but often suffer from co-adsorption and generally low selectivity; very few MOFs based on selective molecular sieving have high selectivity, but due to porosity limitations, their adsorption capacity is less than satisfactory. Summary of the Invention

[0008] To solve the technical problems in the above-mentioned background art, the present invention provides a pillar-layered metal-organic framework material based on the introduction of flexible pillars, a preparation method thereof, and its application in the adsorption and separation of light hydrocarbons.

[0009] The technical solution of the present invention to solve the above technical problems is as follows: two zinc-based complexes, characterized in that: the chemical general formulas are [Zn2(TMTA)(COO)(BPA)2] n (UPC-198) and [Zn2(TMTA)(COO)(BPE)2] n (UPC-199), where Zn is a divalent zinc ion, TMTA is a deprotonated 4,4',4''-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, BPA is 1,2-bis(4-pyridyl)ethane, and BPE is 1,2-bis(4-pyridyl)ethylene;

[0010] Among them, the structure of the zinc-based complex belongs to the triclinic system, space group P-1. The unit cell parameters of UPC-198 are the axial lengths axial angle α = 69.247(3), β = 88.215(3), γ = 68.462(3), and the unit cell volume is Z = 35. The unit cell parameters of UPC-199 are the axial lengths axial angle α = 69.029(3), β = 88.481(3), γ = 68.694(4), and the unit cell volume is Z = 35.

[0011] The beneficial effects of the present invention are as follows: The zinc-based complex of the present invention can be used to prepare adsorption materials, antibacterial materials, catalytic materials, photo-electromagnetic materials, and drug carrier materials. The zinc-based complex of the invention belongs to the metal-organic framework structure and is a composite functional porous material with great potential. The crystal of the zinc-based complex of the present invention was tested at 150K using a SuperNova microfocus X-ray single crystal diffractometer from Agilent Technologies, and data was collected on an EosCCD. Using a graphite monochromator, λ(CuKα) is In the variable angular ω-2θ scanning mode, absorption correction was performed on the data using the CrysAlisPro tool. All structures were directly solved using the SHELXS program encapsulated in SHELXTL, and structure refinement was carried out using the 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 found that the structure of the zinc-based complex of the present invention belongs to the triclinic system, space group P-1. The basic structural unit of the crystal is obtained from the asymmetric unit through symmetry operations. The symmetry operation codes for UPC-198 are 1 +X,+Y,-1+Z; 2 -1+X,1+Y,-1+Z; 3 -1-X,1-Y,1-Z; 4 +X,+Y,1+Z; 5 1+X,-1+Y,1+Z; 6 1-X,2-Y,1-Z; The symmetry operation codes for UPC-199 are 1 +X,+Y,-1+Z; 2 -1+X,1+Y,+Z; 3 +X,+Y,1+Z; 4 -X,-Y,-Z; 5 2-X,1-Y,-Z; 6 1+X,-1+Y,+Z.

[0012] The asymmetric unit consists of a deprotonated ligand TMTA, a ligand BPA / BPE, two zinc ions, and a coordinated formic acid.

[0013] The zinc ion is connected to five atoms in a five-coordination mode. The five atoms connected to Zn1 are the oxygen atoms (O1) in four carboxylate groups (O1-C1-O1) from three different ligands, one oxygen atom (O2) from a formic acid molecule, and one nitrogen atom (N1) from a pillar ligand; the four atoms connected to Zn2 are the oxygen atoms (O1) in four carboxylate groups (O1-C1-O1) from three different ligands, one oxygen atom (O2) from a formic acid molecule, and one nitrogen atom (N1) from a pillar ligand; the carboxylate group (O2-C1-O2) in the ligand adopts a bidentate bridging mode to connect adjacent Zn ions, finally forming a binuclear [Zn2(TMTA)(COO)(BPA)2]n or [Zn2(TMTA)(COO)(BPE)2]n structure. The structure of the zinc-based complex belongs to the triclinic system, space group P-1. The unit cell parameters of UPC-198 are the axial lengths The axial angles are α = 69.247(3), β = 88.215(3), γ = 68.462(3), and the unit cell volume is Z = 35. The unit cell parameters of UPC-199 are the axial lengths The axial angles are α = 69.029(3), β = 88.481(3), γ = 68.694(4), and the unit cell volume is Z = 35.

[0014] The present invention also provides a preparation method of a zinc-based complex, comprising the following steps:

[0015] A. Dissolve the 4,4',4”-(2,4,6-trimethylbenzene-1,3,5) tribenzoic acid ligand, 1,2-bis(4-pyridyl)ethane or 1,2-bis(4-pyridyl)ethylene ligand and zinc nitrate hexahydrate in a solvent to obtain a homogeneous mixed solution. The molar dosage ratio of the 4,4',4”-(2,4,6-trimethylbenzene-1,3,5) tribenzoic acid ligand, 1,2-bis(4-pyridyl)ethane or 1,2-bis(4-pyridyl)ethylene ligand to zinc nitrate hexahydrate is 5:22:70, and the concentrations of the 4,4',4”-(2,4,6-trimethylbenzene-1,3,5) tribenzoic acid ligand and 1,2-bis(4-pyridyl)ethane / 1,2-bis(4-pyridyl)ethylene ligand in the solution are 5 mmol / L and 22 mmol / L respectively;

[0016] B. Place the mixed solution obtained in step A in a glass bottle and keep it at 90 °C for 24 - 48 h to obtain the zinc-based complex.

[0017] The beneficial effects of the present invention are as follows: The preparation method has simple conditions, the reaction can proceed rapidly, energy is saved, and time is saved. Moreover, the preparation method of the zinc-based complex of the present invention has a high yield, a small amount of ligand used, and cost is saved.

[0018] On the basis of the above technical solution, the present invention can be further improved as follows.

[0019] Further, the solvent is composed of N,N-dimethylformamide, ethanol and water, and the volume ratio of N,N-dimethylformamide, ethanol and water is 5:2:1.

[0020] The beneficial effect of adopting the above further solution is that the solvent composed of N,N-dimethylformamide, ethanol and water is easy to obtain, low in price and small in pollution.

[0021] Further, the molar dosage ratio of the 4,4',4''-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, 1,2-bis(4-pyridyl)ethane or 1,2-bis(4-pyridyl)ethylene ligand and the zinc nitrate hexahydrate is 5:22:70, and the concentrations of the 4,4',4''-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand and the 1,2-bis(4-pyridyl)ethane / 1,2-bis(4-pyridyl)ethylene ligand in the solution are 5 mmol / L and 22 mmol / L respectively.

[0022] The beneficial effect of adopting the above further solution is that the zinc-based complex obtained with the determined concentration and molar dosage ratio has better quality and the reaction proceeds more smoothly.

[0023] The present invention also provides an application of a zinc-based complex in the field of low-carbon hydrocarbon gas separation. The zinc-based complex conducts adsorption tests on low-carbon hydrocarbons composed of C2H2, C2H4, C2H6 and CO2, and the obtained differential adsorption amounts are used for adsorption separation.

[0024] The beneficial effects of the present invention are as follows: The zinc-based complex is applied to the field of low-carbon hydrocarbon gas separation, making the function of the zinc-based complex with a columnar structure more comprehensive. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the structural diagram of the asymmetric structural unit of the zinc-based complex of the present invention;

[0026] Figure 2 It is the interpenetrating structure diagram of the zinc-based complex of the present invention;

[0027] Figure 3 It is the thermogravimetric curve diagram of the zinc-based complex of the present invention, where the abscissa is temperature and the ordinate is the percentage of weight loss;

[0028] Figure 4This is the infrared spectrum of the zinc-based complex of the present invention. The abscissa is the wave number and the ordinate is the transmittance;

[0029] Figure 5 This is the adsorption isotherm diagram of the zinc-based complex UPC-198 of the present invention for C2H2, C2H4, C2H6 and CO2 at 298K. The abscissa is the pressure and the ordinate is the adsorption amount;

[0030] Figure 6 This is the adsorption isotherm diagram of the zinc-based complex UPC-198 of the present invention for C2H2, C2H4, C2H6 and CO2 at 273K. The abscissa is the pressure and the ordinate is the adsorption amount;

[0031] Figure 7 This is the adsorption isotherm diagram of the zinc-based complex UPC-199 of the present invention for C2H2, C2H4, C2H6 and CO2 at 298K. The abscissa is the pressure and the ordinate is the adsorption amount;

[0032] Figure 8 This is the adsorption isotherm diagram of the zinc-based complex UPC-199 of the present invention for C2H2, C2H4, C2H6 and CO2 at 273K. The abscissa is the pressure and the ordinate is the adsorption amount;

[0033] Figure 9 This is the dynamic breakthrough experiment diagram of the zinc-based complex of the present invention for C2H2 / CO2 (v / v = 50:50) at 298K. The abscissa is the time and the ordinate is the relative concentration;

[0034] Figure 10 This is the dynamic breakthrough experiment diagram of the zinc-based complex of the present invention for C2H2 / C2H4 (v / v = 1:99) at 298K. The abscissa is the time and the ordinate is the relative concentration. Detailed implementation mode

[0035] The principle and characteristics of the present invention will be described in detail below in conjunction with the examples. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0036] Example 1,

[0037] A preparation method of a zinc-based complex specifically includes the following steps:

[0038] A. Accurately weigh H3TMTA (2.60 mg, 0.005 mmol), Zn(NO3)2·6H2O (20 mg, 0.07 mmol), BPA or BPE (4 mg, 0.022 mmol) with an analytical balance into a reaction vessel. At room temperature, add 1.00 mL of a mixed solvent composed of N,N-dimethylformamide, ethanol and water to the reaction vessel. The volume ratio of N,N-dimethylformamide, ethanol and water is 5:2:1.

[0039] B. Place the mixed solution in step A in a glass bottle and keep it in a constant temperature blower at 90° C. for 48 hours to obtain a colorless, transparent, blocky zinc-based complex.

[0040] The obtained colorless and transparent crystalline zinc-based complex was tested at 150K using Agilent's SuperNova micro-focus X-ray single crystal diffractometer, and the data was received on the EosCCD. A graphite monochromator was used, and λ(CuKα) was Data analysis was performed using the CrysAlisPro tool with a variable speed arbitrary angle scan mode from ω to 2θ, and absorption correction was performed. All structures were solved directly using the SHELXS program packaged in SHELXTL, and the structure was refined using the SHELXL full matrix least squares method. All non-hydrogen atoms were treated anisotropically, and the hydrogen atoms of the organic ligands were generated by geometric symmetry. The crystal data shown in Table 1, the typical bond length data of the crystal shown in Tables 2 and 3, and the typical bond angle data of the crystal shown in Tables 4 and 5 were obtained. Tables 1 to 5 are as follows:

[0041] Table 1: Crystal data

[0042]

[0043]

[0044] Table 2: UPC-198 typical bond length data (unit: )

[0045] Zn1 O6 2.052(6) Zn1 O8 2.021(6) Zn1 O11 2.069(7) Zn1 O14 2.046(7) Zn1 N2 2.024(7) Zn2 O2 2.041(6) Zn2 O4 2.002(7) Zn2 O9 2.016(6) Zn2 N1 2.028(7)

[0046] Table 3: UPC-199 typical bond length data (unit: )

[0047] Zn1 O4 2.9384(14) Zn1 O8 2.062(6) Zn1 O9 2.038(7) Zn1 N1 2.033(7) Zn2 O2 2.016(6) Zn2 O6 2.016(6) Zn2 O9 2.047(6) Zn2 O13 2.056(7) Zn2 O16 2.001(7) Zn2 N1 2.030(7)

[0048] Table 4: Typical bond angle data of UPC-198 (unit: °)

[0049]

[0050]

[0051] Table 5: Typical bond angle data of UPC-199 (unit: °)

[0052] O4 Zn1 O14 76.43(17) O4 Zn1 O8 89.4(2) O4 Zn1 O9 160.8(3) O4 Zn1 N1 99.0(2) O8 Zn1 O12 158.2(3) O9 Zn1 O8 86.3(2) O9 Zn1 O12 87.3(3) N1 Zn1 O8 104.5(2) N2 Zn1 O9 100.1(3) N2 Zn1 O12 97.1(2) O2 Zn2 O6 88.7(2) O2 Zn2 O13 158.2(3) O4 Zn2 N21 104.2(3)

[0053] like Figure 1 and Figure 2As shown, the colorless transparent crystalline zinc-based complex was tested at 150 K using a SuperNova microfocus X-ray single crystal diffractometer from Agilent Technologies, and data was collected on an EosCCD. With a graphite monochromator, λ(Cu Kα) is In a variable angular ω-2θ scan mode, absorption correction was performed on the data using the CrysAlisPro tool. All structures were directly solved using the SHELXS program encapsulated in SHELXTL, and structure refinement was carried out using the 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 Combined with the crystal data in Tables 1 - 5, the following characterizations of the zinc-based complex were obtained:

[0054] The asymmetric unit consists of a deprotonated ligand TMTA, a ligand BPA / BPE, two zinc ions, and a coordinated formic acid molecule.

[0055] The zinc ions adopt a five-coordination mode and are connected to five atoms. The five atoms connected to Zn1 are the oxygen atoms (O1) from four carboxylate groups (O1-C1-O1) of three different ligands, an oxygen atom (O2) from a formic acid molecule, and a nitrogen atom (N1) from a pillar ligand; the four atoms connected to Zn2 are the oxygen atoms (O1) from four carboxylate groups (O1-C1-O1) of three different ligands, an oxygen atom (O2) from a formic acid molecule, and a nitrogen atom (N1) from a pillar ligand; the carboxylate group (O2-C1-O2) in the ligand adopts a bidentate bridging mode to connect adjacent Zn ions, finally forming a binuclear [Zn2(TMTA)(COO)(BPA)2] n or [Zn2(TMTA)(COO)(BPE)2] n structure. The structure of the zinc-based complex belongs to the triclinic system, space group P-1. The unit cell parameters of UPC-198 are the axial lengths axial angles α = 69.247(3), β = 88.215(3), γ = 68.462(3), and the unit cell volume is Z = 35. The unit cell parameters of UPC-199 are the axial lengths axial angles α = 69.029(3), β = 88.481(3), γ = 68.694(4), and the unit cell volume is Z = 35.

[0056] The structure of the zinc-based complex of the present invention belongs to the triclinic system, space group P-1. All the carboxyl groups in H3TMTA are deprotonated and adopt bidentate bridging to connect adjacent Zn ions. The Zn ions are bridged by carboxylate oxygen to form binuclear secondary structure units, and adjacent secondary structure units are connected by three carboxyl groups of the ligand.

[0057] As Figure 3 shown, the colorless transparent crystalline zinc-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 min, 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 two zinc-based complexes can be stable to about 472 °C and 429 °C respectively; for complex UPC-198, the coordinated solvent in the system is lost at 200 °C, the weight loss from 200 to 270 °C is due to partial decomposition of the ligand, and the zinc-based complex decomposes after 472 °C; for complex UPC-199, the coordinated solvent in the system is lost at 200 °C, the weight loss from 200 to 280 °C is due to partial decomposition of the ligand, and the zinc-based complex decomposes after 472 °C. This shows that the zinc-based complex of the present invention has good stability and can decompose at high temperatures.

[0058] As Figure 4 shown, the colorless transparent crystalline zinc-based complex was detected by infrared spectroscopy. The infrared test was carried out by the KBr tablet method, and the infrared spectrum in the range of 4000-400 cm -1 was collected on a Nicolet 330FTIR spectrometer. From Figure 4 it can be seen that the absorption peak near 3016 cm -1 in the complex can be attributed to the O-H stretching vibration peak of water, and the absorption peaks near 1596-1463 cm -1 and 1466-1406 cm -1 can be attributed to the asymmetric and symmetric stretching vibration peaks of the carboxylate group respectively.

[0059] As Figures 5 to 8 shown, the colorless transparent crystalline zinc-based complex was tested by an ASAP2020 instrument of Micromeritics, USA. At 298 K, the adsorption capacities of the zinc-based complex UPC-198 for C2H2, C2H4, C2H6 and CO2 are 53.70, 43.21, 48.51 and 28.77 cm 3 ·g -1; The adsorption capacities of the zinc-based complex UPC-199 for C2H2, C2H4, C2H6 and CO2 are 41.57, 28.05, 31.84 and 25.03 cm 3 ·g -1 . At 273 K, the adsorption capacities of the zinc-based complex UPC-198 for C2H2, C2H4, C2H6 and CO2 are 59.22, 51.13, 53.95 and 32.35 cm 3 ·g -1 ; The adsorption capacities of the zinc-based complex UPC-199 for C2H2, C2H4, C2H6 and CO2 are 46.83, 29.99, 31.54 and 30.02 cm 3 ·g -1 . Therefore, it can be shown from the differential adsorption amounts in the figure that the zinc-based complex can be applied to the field of gas adsorption separation.

[0060] As Figures 9 - 10 shown, the colorless transparent crystal-like zinc-based complex is tested by a multi-component competitive adsorption breakthrough curve analyzer. The total flow rate of the mixed gas is 2 mL / min, and the zinc-based complex shows the separation effects as shown in the figure for C2H2 / C2H4 and C2H2 / CO2. At 298 K, for C2H2 / CO2 (v:v = 50 / 50), the separation times of the zinc-based complex UPC-198 are 5 min / g and 21 min / g respectively; for C2H2 / C2H4 (v:v = 1 / 99), the separation times of the zinc-based complex UPC-199 are 3 min / g and 10 min / g respectively;

[0061] 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 in the protection scope of the present invention.

Claims

1. Two zinc-based complexes, characterized in that: The chemical general formulas are [Zn2(TMTA)(COO)(BPA)2] n (UPC-198) and [Zn2(TMTA)(COO)(BPE)2] n wherein Zn is a divalent zinc ion, TMTA is a deprotonated 4,4',4''-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, BPA is 1,2-bis(4-pyridyl)ethane, and BPE is 1,2-bis(4-pyridyl)ethylene; Among them, the structures of the two zinc-based complexes belong to the triclinic system, space group P-1. The unit cell parameters of UPC-198 are the axial lengths Axial angles α = 69.247(3), β = 88.215(3), γ = 68.462(3), and the unit cell volume is Z = 35. The unit cell parameters of UPC-199 are the axial lengths Axial angles α = 69.029(3), β = 88.481(3), γ = 68.694(4), and the unit cell volume is Z = 35..

2. A method for preparing the zinc-based complex as described in claim 1, characterized in that, It includes the following steps: A. Dissolve 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, 1,2-bis(4-pyridyl)ethane or 1,2-bis(4-pyridyl)ethylene ligand and zinc nitrate hexahydrate in a solvent to obtain a homogeneous mixed solution. The molar dosage ratio of 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, 1,2-bis(4-pyridyl)ethane or 1,2-bis(4-pyridyl)ethylene ligand to zinc nitrate hexahydrate is 5:22:

70. The concentrations of 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand and 1,2-bis(4-pyridyl)ethane / 1,2-bis(4-pyridyl)ethylene ligand in the solution are 5 mmol / L and 22 mmol / L respectively; B. Place the mixed solution obtained in step A in a glass bottle and keep it at 90 °C for 24 - 48 h to obtain the zinc-based complex.

3. The preparation method of the zinc-based complex according to claim 2, wherein The solvent consists of N,N-dimethylformamide, ethanol and water, and the volume ratio of N,N-dimethylformamide, ethanol and water is 5:2:

1.

4. The preparation method of the zinc-based complex according to any one of claims 2 or 3, characterized in that, The molar dosage ratio of 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand, 1,2-bis(4-pyridyl)ethane or 1,2-bis(4-pyridyl)ethylene ligand to zinc nitrate hexahydrate is 5:22:

70. The concentrations of 4,4',4”-(2,4,6-trimethylbenzene-1,3,5)tribenzoic acid ligand and 1,2-bis(4-pyridyl)ethane / 1,2-bis(4-pyridyl)ethylene ligand in the solution are 5 mmol / L and 22 mmol / L respectively.

5. Use of a zinc-based complex as described in claim 1 in the field of low-carbon hydrocarbon gas separation, characterized in that, The zinc-based complex is used to conduct adsorption tests on light hydrocarbons composed of CO2, C2H2, C2H4 and C2H6, and the differential adsorption amounts are obtained for adsorption separation.

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