Construction method and application of porous carbon molecular structure model with adjustable pore structure
By constructing a porous carbon model using the random filling method and annealing molecular dynamics, the problem of pore structure control in existing technologies has been solved, enabling directional control and adsorption simulation of the porous carbon model and expanding the application range of activated carbon.
Patent Information
- Application Number
- CN202511044279.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-28
- Publication Date
- 2025-11-11
AI Technical Summary
Existing methods for constructing porous carbon models cannot accurately reflect pore structure characteristics or directionally control pore structure. There is an urgent need to develop methods for constructing porous carbon molecular structure models with tunable pore structure.
A porous carbon model was constructed using a random filling method. The development of pores in the model was regulated by adding virtual atoms, and a reasonable structure was formed through annealing molecular dynamics. By combining the structure reconstruction method and the simulation process method, a multi-scale model was constructed.
A porous carbon molecular structure model was generated that can widely control porosity and pore size distribution, accurately reflect pore structure characteristics, and be used for adsorption simulation, expanding the application range of activated carbon products and saving costs.
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Figure CN120932786A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of porous carbon materials technology, specifically relating to a method for constructing and applying a porous carbon molecular structure model with adjustable pore structure. Background Technology
[0002] Porous carbon possesses a highly developed pore structure, high specific surface area, and excellent electrochemical performance, making it widely used in catalysis, adsorption separation, and energy storage. The pore structure of porous carbon determines its practical applications, and controlling the pore network has always been a hot topic and a challenge in the preparation and research of porous carbon materials. While numerous pores exist in the solid structure of porous carbon, the carbon framework structural units, which form its basic structure, are mainly composed of amorphous carbon similar to amorphous carbon. Because amorphous carbon lacks a definite crystal structure, characterizing and fully understanding its nanostructure has always been a significant challenge. Since carbon can form numerous allotropes, the atomic details in the porous carbon structure are extremely complex. Experimental methods sometimes cannot resolve all important aspects of the structure, while the predictive power of simulation methods can complement experimental studies of amorphous carbon. The constructed porous carbon molecular structure models can also be further used for simulation studies of applications such as adsorption and catalysis.
[0003] Pore structure control is a challenge in constructing molecular structure models for porous carbon, and different construction methods all suffer from the inability to accurately reflect the characteristics of the pore structure. The simplest and most widely used method for constructing pores in porous carbon is the slit-pore model. This model consists of two parallel graphite sheets, with the spacing between them corresponding to the pore size. However, the slit-pore model has a very simple geometry of pores and cannot reflect the irregular morphology of pores in nanoporous amorphous materials. The random filling method requires repeated model construction to match the target experimental characteristics, and generating a model that matches the actual porosity requires multiple trials and errors; in the quenching molecular dynamics method, carbon atoms tend to aggregate in high-density regions, resulting in a small number of pores generated; the reverse Monte Carlo method and the hybrid reverse Monte Carlo method can reasonably characterize microporous structures, but lack mesoporous structures. Other strategies include creating pores by deleting atoms, which leads to changes and instability in molecular structure due to the breaking of bonds during pore creation. Inserting and deleting carbon nanotubes during the construction process can only generate mesoporous structures in the model due to the size limitations of carbon nanotubes. The strategy of adding virtual particles to the structure generates a more realistic porous structure, which can capture the heterogeneity of carbonaceous materials. For example, inserting a single virtual particle into the structure introduces pores, which is similar to inserting carbon nanotubes, but this method can only introduce a single pore.
[0004] Researchers have proposed numerous strategies to address the most challenging yet crucial aspect of constructing porous carbon material models: pore size control. However, these strategies all have limitations, and current methods fall short of achieving the goal of targeted pore structure control. Therefore, there is an urgent need to develop a method for constructing porous carbon molecular structure models with tunable pore structures. Summary of the Invention
[0005] The technical problem addressed by this invention is that the control of pore structure is both a key focus and a challenge in the construction of porous carbon models. Existing strategies for introducing pores all have limitations and cannot accurately reflect the characteristics of the pore structure. Furthermore, existing porous carbon model construction strategies cannot directionally control the pore structure of the model; therefore, there is an urgent need to develop a method for constructing porous carbon molecular structure models with tunable pore structure.
[0006] To address the aforementioned technical problems, this invention proposes a method for constructing a porous carbon model with tunable pore structure based on molecular simulation. This method utilizes a random filling method to construct the porous carbon model, employs the addition of virtual atoms to regulate the development of pores in the model, and then the model undergoes annealing molecular dynamics to form a reasonable structure. This invention combines the advantages of both structure reconstruction and simulation processes, achieving the goal of constructing multi-scale models.
[0007] Specifically, in view of the shortcomings of the existing technology, the present invention provides the following technical solution:
[0008] A method for constructing a porous carbon molecular structure model with tunable pore structure, characterized by comprising the following steps:
[0009] (1) Calculate the number of carbon atoms required for the porous carbon molecular structure model based on the density of the porous carbon molecular structure model, calculate the number of basic structural units in the model, and determine the number and radius of virtual atoms. The basic structural unit is a graphite sheet structure composed of 24 carbon atoms.
[0010] (2) A certain number of basic structural units and virtual atoms are encapsulated in a three-dimensional periodic boundary with a side length of 5 nm by using the random filling method, while keeping the position of the virtual atoms fixed, to obtain the initial configuration of the molecular structure model.
[0011] (3) The initial configuration obtained in step (2) is structurally optimized and subjected to annealing dynamics simulation. The system is gradually annealed from 6000K to 300K to form an equilibrium system.
[0012] (4) Remove the virtual atoms in the system obtained in step (3) to obtain a carbon skeleton structure. Add hydrogen atoms to the carbon skeleton structure and optimize the structure to obtain a porous carbon molecular structure model.
[0013] Preferably, in the above method for constructing a porous carbon molecular structure model, in step (1), the density of the porous carbon molecular structure model is 0.5 to 2.0 g / cc.
[0014] Preferably, the density of the porous carbon molecular structure model is 1.3 to 1.7 g / cc.
[0015] Preferably, in the above method for constructing a porous carbon molecular structure model, in step (1), the number of virtual atoms is 5% to 100% of the number of carbon atoms.
[0016] Preferably, the number of virtual atoms is 5% to 10% of the number of carbon atoms.
[0017] Preferably, in the above-mentioned method for constructing porous carbon molecular structure models, the radius of the virtual atom is 0.2 to 1.0 nm.
[0018] Preferably, the radius of the virtual atom is 0.2 to 0.4 nm.
[0019] Preferably, in the above method for constructing a porous carbon molecular structure model, in step (2), virtual atoms are filled into the three-dimensional periodic boundary using Packmol software.
[0020] Preferably, in the above method for constructing the porous carbon molecular structure model, open-source kinetic software is used to complete the annealing kinetic simulation process described in step (3).
[0021] Preferably, in the above method for constructing a porous carbon molecular structure model, in step (4), the number of hydrogen atoms is 10% to 15% of the number of carbon atoms.
[0022] The present invention also provides a porous carbon molecular structure model with adjustable pore structure, characterized in that it is obtained by the above-mentioned porous carbon molecular structure model construction method.
[0023] Preferably, the specific surface area of the porous carbon molecular structure model is 100-2500 m². 2 / g.
[0024] Preferably, the average pore size of the porous carbon molecular structure model is 0.5-2.0 nm.
[0025] This invention also provides the application of the above-mentioned porous carbon molecular structure model in the field of simulating the adsorption of volatile organic compounds.
[0026] Preferably, the application includes the following steps:
[0027] Using the porous carbon molecular structure model described in claim 8, the adsorption behavior of styrene gas on the porous carbon molecular structure model is simulated by the giant canonical Monte Carlo method. In this model, the porous carbon molecular structure model and the adsorbate molecules are considered as rigid spheres. The adsorbate molecules generate configurations through four movement operations: insertion, deletion, translation, and rotation. The Metropolis algorithm based on configuration energy changes is used to accept or reject each generated configuration. The COMPASS force field is used for calculation during the adsorption process.
[0028] The beneficial effects of this invention are: it solves the problem of the inability to directionally control the pore structure in the construction of porous carbon molecular structure models. The porous carbon molecular structure model generated by this invention under virtual atom control can produce an extremely wide range of porosity and pore size distributions. By changing the parameters of the virtual atoms, the pore structure can be controlled. The porous carbon molecular structure model construction method described in this invention not only accurately reflects the pore structure characteristics but also simulates adsorption of target substances, saving costs for activated carbon companies, expanding the application range of activated carbon products, and providing a reference for activated carbon users in their selection. Attached Figure Description
[0029] Figure 1 The diagram shows the molecular structure model of porous carbon obtained in Example 1.1.
[0030] Figure 2 The pore size distribution diagram is shown for the porous carbon molecular structure model NPC-SDG-AC obtained in Example 1.1.
[0031] Figure 3a , Figure 3b , Figure 3c The figures shown are porous carbon molecular structure model diagrams of NPC-1 obtained in Example 2.1, NPC-2 obtained in Example 2.2, and NPC-3 obtained in Example 2.3, respectively.
[0032] Figure 4 The pore size distribution diagrams are for the porous carbon molecular structure models of NPC-1 obtained in Example 2.1, NPC-2 obtained in Example 2.2, and NPC-3 obtained in Example 2.3.
[0033] Figure 5 The simulation results are for the adsorption of styrene gas by the porous carbon molecular structure models of NPC-1 obtained in Example 2.1, NPC-2 obtained in Example 2.2, and NPC-3 obtained in Example 2.3. Detailed Implementation
[0034] Given the current limitations of constructing porous carbon molecular structure models, which cannot directionally control the pore structure and accurately reflect its characteristics, this invention proposes a method for constructing porous carbon molecular structure models with adjustable pore structure. The method includes: constructing a porous carbon model using a random filling method; controlling the development of pores in the model by adding virtual atoms; and then subjecting the model to annealing molecular dynamics to form a reasonable structure.
[0035] In a preferred embodiment, the present invention constructs a porous carbon model based on a random-filling method, and uses the addition of virtual atoms to regulate the development of pores in the model, thereby achieving directional control of the pore structure of the porous carbon model. The pore structure of the model can be controlled by adjusting the number and size of the virtual atoms. Annealing molecular dynamics processes can improve the lack of amorphous structure in the random-filling model. High-temperature quenching of the initial structure can transform the overall structure from a condensed state to a glassy state, forming a true amorphous porous structure.
[0036] In another preferred embodiment, the method for constructing the porous carbon molecular structure model of the present invention specifically includes the following steps:
[0037] S1. Calculate the number of carbon atoms required for the density calculation model to determine the number of basic structural units of the model. The basic structural unit is a graphite sheet structure composed of 24 carbon atoms; determine the number and radius of virtual atoms.
[0038] S2, using the random filling method, a certain number of basic structural units and virtual atoms are encapsulated in a three-dimensional periodic boundary with a side length of 5nm, while keeping the position of the virtual atoms fixed, to obtain the initial configuration of the molecular structure model;
[0039] S3. The initial configuration obtained in step S2 is optimized by annealing kinetics simulation. The system is gradually annealed from 6000K to 300K to form an equilibrium system, and a porous carbon molecular structure model containing virtual atoms is obtained.
[0040] S4. Remove the virtual atoms in the system, maintain the carbon skeleton structure, add hydrogen atoms to the carbon skeleton, optimize the structure, and obtain the final porous carbon molecular structure model.
[0041] Preferably, the number of hydrogen atoms is 5% to 20% of the number of carbon atoms.
[0042] In another preferred embodiment, the process of constructing the initial configuration by random filling in step S2 above is performed using Packmol software, and the distance constraint tolerance is set to 0.2 nm to avoid structural overlap.
[0043] In step S3 above, the process of optimizing the model structure through annealing dynamics simulation uses the open-source dynamics software Large-scale Atomic / Molecular Massively Parallel Simulator (LAMMPS). The force fields used are available by default when compiling LAMMPS using the Manybody package. The model construction and annealing dynamics simulation utilize force fields such as Tersoff, Reaxff, and AIREBO.
[0044] In another preferred embodiment, the dummy atom interacts with the carbon atom through a soft repulsion potential, thereby excluding the space around the dummy atom and creating a repulsion volume. The form of the LAMMPS soft repulsion potential is:
[0045]
[0046] In the formula, U s It is the soft repulsive potential, measured in J; A s The pre-factor is a variable that changes over time from the start to the end of the run, and its unit is J; r is the distance between two atoms, and its unit is nm; r s The cutoff radius is the sum of the virtual atomic radius and the carbon atom radius, and the unit is nm.
[0047] The van der Waals radius calculated based on the Lennard-Jones size parameter σ (in nm) of the force field is: Based on the temperature during the quenching process, the energy parameter A is... s The scaling was applied so that the average kinetic energy of the atoms has the following relationship:
[0048]
[0049] In the formula, k B is Boltzmann's constant, in J / K; T is the temperature of the system, in K.
[0050] Annealing requires more potential energy to overcome the kinetic energy of atoms at higher temperatures and prevent carbon atoms from overlapping with virtual atoms. During the simulation, as the temperature decreases, the interaction between carbon atoms and virtual atoms gradually weakens, reducing artificial stress on the final structure.
[0051] Virtual radius is a method for controlling pore size distribution. In this invention, tests were conducted by changing different virtual radius values (0.2-1.0 nm). Preferably, the virtual radius of the virtual atom was set to 0.4 nm. Another important factor affecting pore structure is the number of carbon atoms in the system. Under a given volume, a high density of carbon atoms leads to a lower specific surface area and porosity. The number of carbon atoms is determined by the density of the system; therefore, bulk density is a key factor affecting the porosity of the system. This invention conducted tests by changing different density ranges (0.5-2 g / cc).
[0052] The following specific embodiments further illustrate the construction method and application of the porous carbon molecular structure model with tunable pore structure described in this invention.
[0053] Example 1: Construction of a porous carbon molecular structure model
[0054] Example 1.1
[0055] This embodiment provides the construction of a porous carbon model with actual pore size distribution. The specific steps are as follows:
[0056] S1, based on the model density of 1.5 g / cc, the number of carbon atoms required for the model is calculated to be 9408, the number of basic structural units of the model is determined to be 392, the number of virtual atoms is 941, and the virtual radius is 0.4 nm;
[0057] The formula for calculating the number of carbon atoms is as follows:
[0058] Number of carbon atoms = density x N A х Model volume / 12
[0059] Where, N A Here is Avogadro's constant, with a value of 6.022 × 10⁻⁶. 23 The model volume is 5 3 nm 3 .
[0060] S2, using Packmol software, employs a random filling method to encapsulate a defined number of basic structural units and virtual atoms in 5 3 nm 3 Within the three-dimensional periodic boundary, while keeping the positions of virtual atoms fixed, the initial configuration of the molecular structure model is obtained;
[0061] S3. The initial configuration obtained in step S2 is optimized by using the open-source kinetic software Large-scale Atomic / Molecular Massively Parallel Simulator (LAMMPS) to simulate annealing kinetics. The system is gradually annealed from 6000K to 300K to form an equilibrium system, resulting in a porous carbon molecular structure model containing virtual atoms.
[0062] S4. Virtual atoms were removed from the system while maintaining the carbon framework structure. Hydrogen atoms were added to the carbon framework at 10% of the carbon atoms to optimize the structure, resulting in the porous carbon molecular structure model NPC-SDG-AC with a realistic pore size distribution. The resulting porous carbon structure model is shown in the figure below. Figure 1 As shown, the aperture distribution diagram is as follows: Figure 2 As shown.
[0063] The commercially available activated carbon sample was named SDG-AC. The specific surface area, pore structure, and pore size distribution of the material were analyzed using an ASIQM0001.1 physical adsorption analyzer manufactured by Quantachrome, USA. (10...) -5 At kPa, activated carbon samples were degassed at 300℃ for 3 hours to remove gas and moisture, followed by analysis and testing of the adsorption-desorption isotherms. The specific surface area was calculated using the Bruauer-Emmet-Teller (BET) method, and the pore size distribution was calculated using the quenched solids density functional theory (QSDFT) equation. The results show that the specific surface area of SDG-AC is 952.4 m². 2 / g, with an average pore size of 1.86nm.
[0064] The adsorption performance of commercially available activated carbon for styrene was evaluated by testing the breakthrough curve of the activated carbon in a fixed-bed dynamic adsorption experiment. The fixed-bed dynamic adsorption experimental setup consisted of three main parts: a gas distribution system, a 40℃ adsorption column system, and a gas chromatography analysis system. Nitrogen gas was split into two streams: one stream passed through a bubbler containing liquid styrene, and the other stream was mixed with styrene gas in a buffer tank to prepare 1000 ppm styrene gas. The styrene gas was then passed through the fixed bed containing 0.25 g of adsorbent sample at a total flow rate of 100 ml / min. The concentration of styrene gas at the fixed bed outlet was quantitatively detected using gas chromatography equipped with a flame ionization detector (FID). The breakthrough curve of styrene gas on the activated carbon showed a breakthrough time of 231 min, a saturation time of 325 min, and a saturated adsorption capacity of 207 mg / g.
[0065] This embodiment determines the range of pore structure characteristics of a porous carbon molecular structure model by system density, and then precisely controls the pore structure characteristics of the model by changing virtual atomic parameters, thereby achieving the goal of targeted control of the model's pore structure. Using this method, an NPC-SDG-AC model comparable to commercially available activated carbon in terms of specific surface area and pore size distribution was developed. The specific surface area of this model is 916 m². 2 / g, with an average pore size of 1.25nm, compared to 952nm for the actual SDG-AC sample. 2 The pore size distribution of the NPC-SDG-AC model is very close to that of the actual porous carbon sample. The comparison between the pore size distribution of the NPC-SDG-AC model and the actual porous carbon sample shows that the NPC-SDG-AC model can accurately reproduce the microporous characteristics of the actual SDG-AC sample.
[0066] This embodiment simulates the adsorption of styrene gas using the NPC-SDG-AC model. The adsorption simulation process is as follows: the adsorption behavior of styrene gas on porous carbon was simulated using the Grand Canonical Monte Carlo (GCMC) method. The porous carbon structure model and adsorbate molecules were treated as rigid spheres. Adsorbate molecules generated configurations through four movement operations: insertion, deletion, translation, and rotation. The Metropolis algorithm based on configuration energy changes was used to accept or reject each generated configuration. The COMPASS force field was used for calculations during the adsorption process. Under a pressure of 101.325 kPa and a temperature of 303.15 K, the number of equilibrium steps in the simulation process was set to 1 × 10⁻⁶. 6 The production steps are set to 1×10. 7 The results showed that the model adsorption capacity for styrene at room temperature and pressure was 201 mg / g, which differed from the actual styrene gas adsorption result by 2.9%. The simulated adsorption result was very close to the actual adsorption result.
[0067] Example 1.2
[0068] This embodiment is similar to the model construction method in Embodiment 1.1, except that the number of virtual atoms in step S1 is different.
[0069] When the number of virtual atoms is 314, the specific surface area of the model is 1107 m². 2 / g, pore volume is 0.381cm³ 3 / g, with an average pore size of 1.42nm.
[0070] When the number of virtual atoms is 1886, the specific surface area of the model is 1888 m². 2 / g, pore volume is 0.336cm³ 3 / g, with an average pore size of 0.75nm.
[0071] When the number of virtual atoms is 3144, the specific surface area of the model is 1980 m². 2 / g, pore volume is 0.331cm³ 3 / g, with an average pore size of 0.66nm.
[0072] Example 1.3
[0073] This embodiment is similar to the model construction method in embodiment 1.1, except that the virtual radius in step S1 is different.
[0074] When the virtual radius is 0.2 nm, the specific surface area of the model is 830 m². 2 / g, pore volume is 0.389cm³ 3 / g, with an average pore size of 1.69nm.
[0075] When the virtual radius is 0.6 nm, the specific surface area of the model is 1470 m². 2 / g, pore volume is 0.392cm³ 3 / g, with an average pore size of 1.14nm.
[0076] When the virtual radius is 0.8 nm, the specific surface area of the model is 1212 m². 2 / g, pore volume is 0.455cm³ 3 / g, with an average pore size of 1.48nm.
[0077] When the virtual radius is 1.0 nm, the specific surface area of the model is 1007 m². 2 / g, pore volume is 0.510cm³ 3 / g, with an average pore size of 1.68nm.
[0078] Comparative Example 1
[0079] The difference between Comparative Example 1 and Example 1.1 is that no hydrogen atoms are added in step S4 of Comparative Example 1. A model was constructed using the same method as in Example 1.1 to simulate the adsorption process of styrene. The results show that the specific surface area of the model in Comparative Example 1 is 982 m². 2 / g, with an average pore size of 1.21nm, and an adsorption capacity of 175mg / g for styrene.
[0080] Example 2: Construction of porous carbon molecular structure models with different pore size distributions
[0081] This embodiment provides the construction of porous carbon models with different pore size distributions, as detailed below:
[0082] Example 2.1
[0083] The construction process of the NPC-1 model with micropore-mesopore distribution is as follows:
[0084] S1, based on a density of 0.5 g / cc, the number of carbon atoms required for the model is 3144, the number of basic structural units of the model is determined to be 131, the number of virtual atoms is 315, and the virtual radius is 0.4 nm;
[0085] S2, using a random filling method, encapsulates a fixed number of basic structural units and virtual atoms in 5 3 nm 3 Within the three-dimensional periodic boundary, while keeping the positions of virtual atoms fixed, the initial configuration of the molecular structure model is obtained;
[0086] S3. The initial configuration obtained in step S2 is optimized by annealing kinetics simulation. The system is gradually annealed from 6000K to 300K to form an equilibrium system, and a porous carbon molecular structure model containing virtual atoms is obtained.
[0087] S4, remove virtual atoms from the system, maintain the porous structure of the carbon skeleton, add hydrogen atoms to the carbon skeleton at 10% of the number of carbon atoms, optimize the structure, and obtain the porous carbon molecular structure model NPC-1 with micropore-mesopore distribution.
[0088] Example 2.2
[0089] The construction process of the NPC-2 model with submicropore distribution is as follows:
[0090] S1, based on a density of 0.7 g / cc, the number of carbon atoms required for the model is 4392, the number of basic structural units of the model is determined to be 183, the number of virtual atoms is 440, and the virtual radius is 0.4 nm;
[0091] S2, using a random filling method, encapsulates a fixed number of basic structural units and virtual atoms in 5 3 nm 3 Within the three-dimensional periodic boundary, while keeping the positions of virtual atoms fixed, the initial configuration of the molecular structure model is obtained;
[0092] S3. The initial configuration obtained in step S2 is optimized by annealing kinetics simulation. The system is gradually annealed from 6000K to 300K to form an equilibrium system, and a porous carbon molecular structure model containing virtual atoms is obtained.
[0093] S4. Remove virtual atoms from the system, maintain the porous structure of the carbon skeleton, add hydrogen atoms to the carbon skeleton at 10% of the number of carbon atoms, and optimize the structure to obtain the porous carbon molecular structure model NPC-2 with submicropore distribution.
[0094] Example 2.3
[0095] The construction process of the NPC-3 model with ultra-micropore distribution is as follows:
[0096] S1, based on a density of 1.75 g / cc, the number of carbon atoms required for the model is 10968, the number of basic structural units of the model is determined to be 457, the number of virtual atoms is 1097, and the virtual radius is 0.4 nm;
[0097] S2, using a random filling method, encapsulates a fixed number of basic structural units and virtual atoms in 5 3 nm 3 Within the three-dimensional periodic boundary, while keeping the positions of virtual atoms fixed, the initial configuration of the molecular structure model is obtained;
[0098] S3. The initial configuration obtained in step S2 is optimized by annealing kinetics simulation. The system is gradually annealed from 6000K to 300K to form an equilibrium system, and a porous carbon molecular structure model containing virtual atoms is obtained.
[0099] S4. Virtual atoms in the system are removed, the porous structure of the carbon skeleton is maintained, and hydrogen atoms are added to the carbon skeleton at 10% of the number of carbon atoms to optimize the structure and obtain the porous carbon molecular structure model NPC-3 with a small micropore distribution.
[0100] The molecular structure models of NPC-1, NPC-2, and NPC-3 porous carbon are shown below. Figure 3a , 3b As shown in Figure 3c, its pore size distribution diagram is as follows: Figure 4 As shown. NPC-1 is a microporous-mesoporous carbon model, exhibiting mesoporous distribution characteristics, in the range of ~ It exhibits mesopore peaks but lacks ultramicropore distribution. NPC-2 and NPC-3 are microporous carbon models, with NPC-2 showing submicropore distribution and NPC-3 showing ultramicropore distribution. NPC-1 and NPC-2 have wavelengths of 2015 and 1688 μm, respectively. 2 The NPC-1 has a high specific surface area of 156 m² / g, with NPC-1 having a porosity of up to 65.8% and NPC-2 having a porosity of 51.8%. NPC-3, due to its dense carbon structure, has a porosity of only 15.9%, resulting in a specific surface area of 156 m² / g. 2 / g.
[0101] To verify the practicality of the model, the simulation results of the porous carbon molecular structure model with different pore size distribution obtained in Example 2 adsorbing styrene gas are as follows: Figure 5As shown in the figure, according to the classification of the International Union of Pure and Applied Chemistry (IUPAC), the adsorption isotherms of all porous carbon models exhibit typical Type I Langmuir isotherm characteristics, indicating that they possess micro-mesoporous structure features. Due to the abundant micropore structure of porous carbon, its external surface area is much smaller than its internal pore surface area. Therefore, the adsorption curve rises rapidly in the low-pressure region, corresponding to the micropore filling process; while at higher pressures, external surface adsorption occurs in the flat region. The model demonstrates the pore structure diversity, surface heterogeneity, and uneven distribution of adsorption sites characteristic of real porous carbon materials.
[0102] In summary, the porous carbon molecular structure model construction method of this invention can directionally adjust the pore structure, generating a very wide range of porosity and pore size distributions, thereby achieving the goal of pore structure control. The porous carbon molecular structure model obtained by this invention can accurately reflect the pore structure characteristics of activated carbon, perform adsorption simulation on adsorption targets, and predict adsorption performance in advance.
Claims
1. A method for constructing a porous carbon molecular structure model with tunable pore structure, characterized in that, Includes the following steps: (1) Calculate the number of carbon atoms required for the porous carbon molecular structure model based on the density of the porous carbon molecular structure model, calculate the number of basic structural units in the model, and determine the number and radius of virtual atoms. The basic structural unit is a graphite sheet structure composed of 24 carbon atoms. (2) A certain number of basic structural units and virtual atoms are encapsulated in a three-dimensional periodic boundary with a side length of 5 nm by using the random filling method, while keeping the position of the virtual atoms fixed, to obtain the initial configuration of the molecular structure model. (3) The initial configuration obtained in step (2) is structurally optimized and subjected to annealing dynamics simulation. The system is gradually annealed from 6000K to 300K to form an equilibrium system. (4) Remove the virtual atoms in the system obtained in step (3) to obtain a carbon skeleton structure. Add hydrogen atoms to the carbon skeleton structure and optimize the structure to obtain a porous carbon molecular structure model.
2. The method for constructing a porous carbon molecular structure model according to claim 1, wherein, In step (1), the density of the porous carbon molecular structure model is 0.5 to 2.0 g / cc.
3. The method for constructing a porous carbon molecular structure model according to claim 1 or 2, wherein, In step (1), the number of virtual atoms is 5% to 100% of the number of carbon atoms.
4. The method for constructing a porous carbon molecular structure model according to any one of claims 1-3, wherein, The radius of the virtual atom is 0.2 to 1.0 nm.
5. The method for constructing a porous carbon molecular structure model according to any one of claims 1-4, wherein, In step (2), virtual atoms are filled into the three-dimensional periodic boundary using Packmol software.
6. The method for constructing a porous carbon molecular structure model according to any one of claims 1-5, wherein, The annealing dynamics simulation process described in step (3) is completed using open-source dynamics software.
7. The method for constructing a porous carbon molecular structure model according to any one of claims 1-6, wherein, In step (4), the number of hydrogen atoms is 5% to 20% of the number of carbon atoms.
8. A porous carbon molecular structure model with tunable pore structure, characterized in that, The porous carbon molecular structure model was obtained using the method described in any one of claims 1-7.
9. The application of the porous carbon molecular structure model of claim 8 in the field of simulating the adsorption of volatile organic compounds.
10. The application according to claim 9, characterized in that, Includes the following steps: Using the porous carbon molecular structure model described in claim 8, the adsorption behavior of styrene gas on the porous carbon molecular structure model is simulated by the giant canonical Monte Carlo method. In this model, the porous carbon molecular structure model and the adsorbate molecules are considered as rigid spheres. The adsorbate molecules generate configurations through four movement operations: insertion, deletion, translation, and rotation. The Metropolis algorithm based on configuration energy changes is used to accept or reject each generated configuration. The COMPASS force field is used for calculation during the adsorption process.