A method for designing porous materials for specific adsorption of benzene based on density functional theory

Abstract

The invention discloses a method for designing a porous material for specific adsorption of benzene based on density functional theory, adopts a theoretical calculation method, uses an acetaldehyde group to modify an adsorption model, designs and constructs an adsorption model with specific adsorption to benzene molecules, uses a quantum chemical program to perform structural optimization and single-point energy calculation on the adsorption model modified by the acetaldehyde group based on density functional theory to obtain a quantum chemical calculation result file, uses quantum chemistry and wave function analysis methods to perform weak interaction theoretical analysis on the designed porous material adsorption model, studies the adsorption effect of the MOFs porous material adsorption model on benzene, thereby obtaining a MOFs framework structure with specific adsorption to benzene, and laying a solid theoretical basis for specific adsorption of benzene. Compared with directly using a laboratory "trial and error" adsorption method, the adsorption mechanism can be accurately and efficiently studied, and the porous material structure for specific adsorption of benzene can be obtained more conveniently and intuitively than experiments.

Description

Technical Field

[0001] The invention relates to a method for designing a porous material for specific adsorption of benzene based on density functional theory, and belongs to the category of quantum chemical calculation. Background Art

[0002] Benzene is commonly found in building decoration materials, coatings, paints and other materials. Benzene pollution poses a great threat to human health and the environment. Therefore, the treatment of benzene pollution has attracted widespread attention. Traditional adsorption methods are not only inefficient but also have long cycles and many disadvantages. MOFs are a new type of functional porous material with properties such as high specific surface area, adjustable structure and pore size. They are diverse in type and rich in structure and can be used to adsorb toxic substances. MOFs adsorption is mainly chemical adsorption, involving many different types of weak interactions such as hydrogen bonds and van der Waals interactions. It has been widely used in the adsorption of CO2, heavy metal pollutants in water, etc. Metal-organic frameworks are used to adsorb benzene molecules through the specific adsorption of synergistic effects, thereby achieving the purpose of reducing benzene pollution.

[0003] Using computer simulation technology, we can intuitively and specifically design a framework and qualitatively and quantitatively analyze the adsorption mechanism. Among them, Density Functional Theory (DFT) has excellent calculation performance and has become one of the most important quantum chemical methods for explaining various physical and chemical problems in recent years. Therefore, it is very advantageous and necessary to design and study the adsorption model of porous materials for benzene molecules through theoretical research instead of experimental methods. Summary of the invention

[0004] The purpose of the present invention is to provide a method for designing a porous material for specific adsorption of benzene based on density functional theory to solve the problems existing in the existing traditional adsorption technology. The process is realized by computer technology, avoiding chemical experiments, saving time and cost. The shortcomings of low efficiency and complex process in the traditional method for adsorbing benzene molecular pollutants are solved, and a porous material adsorption configuration method for specific adsorption of benzene with good universality, high efficiency and low cost based on molecular modeling is provided.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for designing a porous material for specific adsorption of benzene based on density functional theory, comprising the following steps:

[0007] 1) Selection of MOFs porous structure: The pore size suitable for the structure of benzene molecules is selected through the existing database. The selected MOFs pore structure is mainly composed of tetracyanoplatinum ions, 1,4-bis(4-pyridine)butyne and Fe II composition;

[0008] 2) Growth of porous structure: Mercury 3.6 chemical software was used to grow the selected minimum unit matrix into a three-dimensional structure; when the framework grew into a three-dimensional structure, since the growth direction was uncertain and the framework growth was infinite, GaussView 5.0 was used to process the framework;

[0009] 3) Selection of independent pore structure: The complete independent pore structure is cut from the structure grown in step 2), retaining the metal center Fe II The coordination environment of N atoms is replaced by NH3 molecules;

[0010] 4) Design and modeling of adsorption model: Based on the selected pore structure and the structural characteristics of the benzene ring, acetaldehyde group modification is used to design a porous structure with specific adsorption performance for benzene molecules by utilizing different adsorption sites;

[0011] 5) Structural optimization of the adsorption model: Using the quantum chemistry software Gaussian 16, the H atoms in the adsorption model structure, the acetaldehyde groups added in the adsorption model, and the guest benzene molecules were all structurally optimized, and the other parts retained their original structures, freezing all atoms except hydrogen atoms and guest molecules;

[0012] 6) Calculation: Use the quantum chemical calculation program Gaussian 16 to perform DFT calculations on the optimized adsorption model. The single-point energy calculation uses DFT-D3 dispersion correction at the M06-2X / def2-TZVP calculation level until all four required parameters converge, the configuration reaches the energy minimum point and the frequency has no imaginary frequency, and the corresponding file containing wave function information is obtained; convert the output file xx.chk of the adsorption model into a xx.fchk file;

[0013] 7) Weak interaction theoretical analysis: The wave function file obtained by step 6) is analyzed by using the quantum chemistry wave function analysis program Multiwfn; the area involved in weak interaction is determined by the weak interaction graphical analysis method - Reduced Density Gradient (RDG); the isosurface map is obtained in the Visual Molecular Dynamics (VMD) program;

[0014] 8) Based on the isosurface diagram obtained in step 6), the weak interaction of this adsorption model on benzene molecules is studied.

[0015] As a preferred solution, in step 2), the framework is grown into a three-dimensional structure using Mercury 3.6.

[0016] As a preferred solution, in step 3), the independent pore structure is captured and modified by GaussView 5.0.

[0017] As a preferred solution; in the step 3), the pore size of the complete independent pore structure matches the benzene molecule, and the structure can meet the requirements of specific adsorption of benzene molecules.

[0018] As a preferred solution, in step 4), GaussView 5.0 is used to design and build the adsorption model.

[0019] As a preferred embodiment; in step 4), the adsorption model is an adsorption model modified with acetaldehyde groups.

[0020] As a preferred embodiment; in the step 4), by introducing a hydrogen-containing functional group acetaldehyde to replace the H atom on the pyridine ring, an adsorption effect is generated between the large π bond of the benzene ring; by introducing an O-containing functional group acetaldehyde group to replace the H atom on the pyridine ring, a weak interaction is generated on the H on the benzene ring; the butyne conjugated bond of the organic ligand in the structure also has an excellent weak interaction with the H on the benzene ring.

[0021] As a preferred solution, in step 5), the structure is optimized using quantum chemistry software Gaussian 16.

[0022] As a preferred solution; in step 5), density functional theory DFT / M06-2X is used, basis set def2-TZVP is selected, and keyword opt is used for structural optimization to obtain the lowest energy stable configuration.

[0023] As a preferred solution; in step 6), DFT-D3 dispersion correction is used at the M06-2X / def2-TZVP calculation level, and the single-point energy calculation adopts 10 -8 Hartree convergence criterion.

[0024] As a preferred solution, in step 6), the output files xx.chk of the adsorption model are converted into xx.fchk files.

[0025] As a preferred solution; in the step 7), the wave function analysis is performed using the quantum chemistry wave function analysis program Multiwfn; the region involving weak interactions is determined by the weak interaction graphical analysis method (RDG); and the isosurface map is obtained in the visual molecular dynamics program (VMD).

[0026] As a preferred embodiment; in the step 8), the weak interaction of the adsorption model on benzene molecules is studied according to the isosurface diagram.

[0027] The present invention is based on the method of molecular modeling, and uses density functional theory DFT / M06-2X for calculation research. The quantum chemical program is used to perform structural optimization and single-point energy calculation on the acetaldehyde group modified adsorption model to obtain a quantum chemical calculation result file, and the method of quantum chemistry and wave function analysis is used to use Multiwfn software to perform weak interaction theoretical analysis on the designed porous material adsorption model, and the adsorption effect of the MOFs porous material adsorption model on benzene is studied, so as to obtain the MOFs framework structure with specific adsorption to benzene, and lay a solid theoretical basis for the specific adsorption of benzene. The adsorption mechanism can be studied accurately and efficiently, and the porous material structure for specific adsorption of benzene can be obtained more conveniently and intuitively than experiments. The advantage of this method is that the results are accurate and reliable, and the loss caused by repeated experiments can be reduced, and the environmental pollution caused by the experiment can be reduced.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) The present invention uses quantum chemical calculation and wave function analysis. The DFT / M06-2X method can obtain almost optimal structural and energy information after DFT-D3 dispersion correction, and uses the def2-TZVP basis set that can provide sufficiently accurate basis set for quantum chemical calculation. The porous structure of MOFs with specific adsorption to benzene molecules can be accurately and reliably obtained;

[0030] 2) The acetaldehyde group modified adsorption model in the present invention can produce a significant adsorption effect on benzene molecules, and has potential application prospects in the adsorption of benzene. The three adsorption effects in the acetaldehyde group modified adsorption model are synergistic and coupled, and benzene molecules are stably adsorbed in a chelating manner, which can be used as a good benzene adsorption material to reduce benzene pollution;

[0031] 3) The entire process of the present invention is realized by computer, which avoids experiments, reduces research and development costs, and is safe and reliable;

[0032] 4) The whole process of the present invention does not involve experiments, thus avoiding environmental pollution and conforming to the development concept of green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The growth framework of the MOFs porous structure selected for the present invention;

[0034] Figure 2 The complete independent pore structure captured by the present invention;

[0035] Figure 3 The acetaldehyde group modified adsorption model designed for the present invention;

[0036] Figure 4 This is the RDG analysis result of the acetaldehyde group modified adsorption model on the weak interaction of benzene molecules in the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0038] The present invention provides a method for designing a porous material for specific adsorption of benzene based on density functional theory, comprising the following steps:

[0039] 1. Select the porous structure of MOFs with pore size suitable for the benzene molecular structure, which is mainly composed of tetracyanoplatinum ions, 1,4-bis(4-pyridine)butyne and Fe II composition;

[0040] 2. Use Mercury 3.6 chemical software to grow the selected minimum unit matrix into a three-dimensional structure, and use GaussView 5.0 to process the framework structure, intercept the complete independent pore structure, and retain the metal center Fe II The coordination environment of N atoms is replaced by NH3 molecules;

[0041] 3. Based on the comprehensive consideration of the selected pore structure and the structural characteristics of the benzene ring, GaussView 5.0 was used to design the model, and the acetaldehyde functional group that can provide adsorption was used to modify the porous structure with specific adsorption performance for benzene molecules by using different adsorption sites; the designed adsorption model is the acetaldehyde group modified adsorption model;

[0042] 4. Using quantum chemistry software Gaussian 16, using functional M06-2X and def2-TZVP basis set, using keyword opt, the H atoms, added functional groups, and guest benzene molecules in the acetaldehyde group modified adsorption model were structurally optimized to obtain the lowest energy stable configuration;

[0043] 5. The optimized adsorption model was subjected to DFT calculation using the quantum chemical calculation program Gaussian 16. The single-point energy calculation was performed using DFT-D3 dispersion correction at the M06-2X / def2-TZVP calculation level. -8 Hartree convergence criterion, and obtain the corresponding file containing wave function information;

[0044] 6. Convert the output file xx.chk of the acetaldehyde group modified adsorption model obtained in step 5 into a xx.fchk file and input it into the Multiwfn quantum chemical wave function analysis software for weak interaction theoretical analysis;

[0045] 7. The weak interaction graphical analysis method RDG was used to determine the area involved in weak interactions. The corresponding isosurface diagram was obtained in the visual molecular dynamics program VMD to study the weak interaction of the acetaldehyde group modified adsorption model on benzene molecules, and the adsorption effect of the porous structure on benzene molecules was analyzed more intuitively:

[0046] 7.1. From the adsorption of H atoms on the large π bond of the benzene ring in the adsorption model modified by the acetaldehyde group, the C—H…π interaction in the adsorption model is strong, and the adsorption model modified by the acetaldehyde group appears as a continuous sheet on the RDG isosurface. In the scatter plot, the spikes corresponding to the adsorption model modified by the acetaldehyde group are denser. From the RDG analysis result diagram, it can be seen that the C—H…O weak interaction appears as a blue, relatively stable hydrogen bond on the RDG isosurface, which is a strong interaction. In addition, the two weak interactions C—H…π and C—H…O show coupling phenomenon;

[0047] 7.2. There are three weak interactions in the acetaldehyde group modified adsorption model. The adsorption between the acetaldehyde group O and the benzene ring H, and between the acetaldehyde group H and the large π bond of the benzene ring are both C—H…π weak interactions, and the adsorption between the butyne conjugated bond and the benzene ring H is a C—H…O weak interaction. The three adsorption effects in the acetaldehyde group modified adsorption model are synergistic and coupled, and the benzene molecules are stably adsorbed in a chelating manner. In the acetaldehyde group modified adsorption model, the synergy of C—H…O and C—H…π plays a leading role. The synergy and coupling between multi-site adsorption effects can adsorb benzene molecules more stably in the pore structure than other guest molecules, and the adsorption effect on benzene molecules is specific;

[0048] 7.3. Through the study of the adsorption model modified by acetaldehyde groups, it was found that the adsorption of benzene molecules can be significantly specific, which has potential application prospects in the adsorption of benzene. It can be used as a good material for adsorbing benzene to reduce benzene pollution.

Claims

1. A method for designing porous materials for specific adsorption of benzene based on density functional theory, characterized in that: The steps include: 1) Selection of MOFs porous structure: The pore size suitable for the structure of benzene molecules is selected through the existing database. The selected MOFs pore structure is mainly composed of tetracyanoplatinum ions, 1,4-bis(4-pyridine)butyne and Fe II composition; 2) Growth of porous structure: Mercury 3.6 chemical software was used to grow the selected minimum unit matrix into a three-dimensional structure; when the framework grew into a three-dimensional structure, GaussView 5.0 was used to process the framework; 3) Selection of independent pore structure: The complete independent pore structure is cut from the structure grown in step 2), retaining the metal center Fe II The coordination environment of N atoms is replaced by NH3 molecules; 4) Design and modeling of adsorption model: GaussView 5.0 was used to design and model the adsorption model. The adsorption model used acetaldehyde groups to replace hydrogen atoms on the pyridine ring and designed a porous structure with specific adsorption properties for benzene molecules by using different adsorption sites. 5) Structural optimization of the adsorption model: Using the quantum chemistry software Gaussian 16, the functional M06-2X and def2-TZVP basis set, and the keyword opt, the H atoms in the adsorption model structure, the acetaldehyde groups added in the adsorption model, and the guest benzene molecules were all structurally optimized, and the other parts retained the original structure, and the atoms other than the hydrogen atoms and guest molecules were frozen; 6) Calculation: The optimized adsorption model was subjected to DFT calculation using the quantum chemical calculation program Gaussian 16. The single-point energy calculation was performed using DFT-D3 dispersion correction at the M06-2X / def2-TZVP calculation level. -8 Hartree convergence standard, until all four required parameters converge, the configuration reaches the energy minimum and the frequency has no imaginary frequency, and the corresponding file containing wave function information is obtained; the output file xx.chk of the adsorption model is converted into xx.fchk file; 7) Weak interaction theoretical analysis: The wave function file obtained by step 6) is analyzed by using the quantum chemistry wave function analysis program Multiwfn; the area involved in weak interaction is determined by the weak interaction graphical analysis method - Reduced Density Gradient (RDG); the isosurface map is obtained in the Visual Molecular Dynamics (VMD) program; 8) Based on the isosurface diagram obtained in step 6), the weak interaction of the acetaldehyde group-modified adsorption model with benzene molecules is studied.

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