The molecular interpretation of separation mechanisms is one of the effective methods to develop new materials and at the same time improve existing materials. In Chapter 1 we provide a brief overview of separation processes and the need to develop an energy efficient separation process, together with a general background of the separation processes for CO2 and olefin/paraffin separations. Theoretical permeances with (001) and (101) out-of-plane oriented DDR membrane show that only the 8-MR pores with some defects made a relatively large contribution to the permeation of CO2 and H2 molecules under the separation conditions, also already a significant number of the 6-MR pores were arranged in the out-of-plane direction of the c-oriented membrane.
Furthermore, we propose that the stable CO adsorption originates from the facilitated regeneration of the Fe(II) site through the formation of a stable intermediate state in the Fe(III) reduction pathway.
Introduction
General Introduction to Separation Process
- Separation Process of CO 2
- Separation Process of Olefin and Paraffin Molecules
Introduction to Porous Materials
- Zeolites
- MOFs
Multiscale Molecular Simulation
- Density Functional Theory (DFT) Calculation
- Molecular Dynamics (MD) Simulation
- Monte Carlo (MC) Simulation
Highly Oriented Zeolite Membrane for Selective Permeation
Effective CO 2 Capture Using (h0h)-Oriented DDR Membrane with Insight into Its
- Introduction
- Computational Models and Methods
- Results and Discussion
- Conclusion
- References
To this end, reducing the adsorption amount of H2O on and in DDR zeolites using a hydrophobic silica membrane constituent25–27 is a good approach to ensure a high CO2/N2 separation performance in the presence of H2O. Furthermore, the nature of the hydrophobic effect on the permeation behavior of CO2/N2 molecules in the presence of H2O has not been elucidated much. Therefore, we investigated the effect of water on the adsorption and diffusion of gas molecules (i.e. CO2 and N2 molecules) on the inside and surface of the membrane by means of molecular simulations including GCMC simulation and DFT calculation.
GCMC Simulation We modeled the periodic crystal structure of DDR zeolite (Figure 2.1.1) and performed a GCMC simulation to elucidate the adsorption behaviors of guest molecules on DDR zeolite. We used a Sorbtion program (BIOVIA Material studio 201732) to estimate the average sorbed amounts of CO2 and N2 molecules in the presence and absence of H2O via GCMC simulation. Simulated adsorption isotherms of single CO2 and N2 components were in good agreement with experimental data in the literature validating the simulation approaches in this study (Figure 2.1.2a).
Taking into account the gradient in the adsorbed amount of CO2 across a DDR membrane, its diffusion and/or adsorption on the membrane surface will be crucial in determining the overall permeation rates in the presence of H2O. This leads to the likely existence of a surface resistance (or barrier) in the presence of H2O. Using the molecular simulations of the adsorption properties of CO2 and N2 molecules with and without H2O molecule, we observed the condensation of the water layer at the surface of the DDR membrane, and the adsorption of CO2 was further stabilized by the presence of water.
In contrast, H2O molecules adsorbed on the membrane surface significantly hindered the transport of the relatively large N2 molecules into the DDR zeolite pore mouth and subsequently across the membranes. Hydrogen bonding effects in adsorption of water-alcohol mixtures in zeolites and the consequences for the characteristics of the Maxwell-Stefan diffusivities.
New Insight into H 2 -Permselectivity at the c-Oriented DDR Membrane
- Introduction
- Computational Models and Methods
- Results and Discussion
- Conclusion
- References
Enhanced C–H···π Interactions in MOFs for Ethane-Selective Adsorption
- Introduction
- Adsorptive Separation in DUT-8(Cu, Ni)
- Computational Models and Methods
- Results and Discussion
- Adsorptive Separation in MIL-53 isomorphs
- Computational Models and Methods
- Results and Discussion
- Adsorptive Separation in CAU-3-NDCA
- Conclusion
- References
Carbon, hydrogen, oxygen and aluminum atoms are colored gray, white, red and pink, respectively. Al atoms are represented by a polyhedron, while the other atoms in CAU-3-NDCA are represented by a stick model. Carbon, hydrogen-oxygen, and aluminum atoms in CAU-3-NDCA are colored in gray, white, red, and pink, respectively.
CAU-3-NDCA and adsorbed molecule are presented by stick model and ball-and-stick models, respectively.
Incorporation of Inorganic Interaction Sites in Rationally Designed Porous Materials
Enhanced CO Selectivity and Adsorption Stability in Cu(Ⅰ)Zn@MIL-100(Fe)
- Introduction
- Computational Models and Methods
- Results and Discussion
- Conclusion
- References
One reason for such limitations may be the small surface areas of common host materials. The effects of Zn(Ⅱ) addition on the recycling of Fe(Ⅱ) sites and the binding properties of CO and CO2 molecules were investigated by DFT calculations. In addition, the affinity for CO increased as the amount of Zn(II) dopant increased.
As the amount of Zn(II) dopant increases, the intensity of the partial DOS corresponding to the 2π* orbital is slightly reduced, while that corresponding to 5σ increases (Figure 4.1.6a). Therefore, it is necessary to understand the role of ZnCl2 in improving these characteristics of the Cu(I)Zn@MIL-100(Fe) adsorbent. The regeneration of the Fe(Ⅱ) sites after Cu(Ⅱ) is reduced to Cu(Ⅰ) may be one reason for the increased Cu(Ⅰ) concentration in the Cu(Ⅰ)Zn@MIL-100(Fe) adsorbents.
For the DFT calculations, it was assumed that the radical intermediate (ie, Cl0) could be formed in the process of the redox reaction. As shown in Figure 4.1.7, the separation of the Cl0 radical from the Fe(Ⅲ) site in the cluster model requires a reaction energy of 52.67 kcal/mol (path 0). In this study, the origin of the enhanced CO adsorption of the new Cu(I)Zn@MIL-100(Fe) adsorbent was investigated by DFT calculations.
From the analyzes of the densities of state (DOS) and orbitals responsible for CO adsorption, enhanced CO adsorption was attributed to the relatively strong σ bond between Cu(I) and CO. Ab initio investigation of the adsorption of small molecules on metal-organic frameworks with oxo-centered trimetallic building units: the role of the undercoordinated metal ion.
Synergetic Binding Sites for CO 2 Adsorption in Porous Metallocage
- Introduction
- Computational Models and Methods
- Results and Discussion
- Conclusion
- References
Through the molecular simulation methods and experimental adsorption data, we investigated stable configurations of CO2 molecules adsorbed in UMC-1, and found that these two groups interact synergistically with CO2 molecules exhibiting highly selective CO2 adsorption toward N2. For the potential energy parameters, we started with the universal force field (UFF) and adjusted the parameters of UFF to reproduce the experimental adsorption isotherm and isosteric heat of CO2 adsorption. Table 4.1) Atomic partial charges of UMC-1 were obtained using the charge equilibrium method (Qeq). 106 equilibrium steps and 1 x 107 production steps to obtain thermodynamically equilibrated adsorption isotherms and isosteric heat of CO2 in UMC-1.
DFT calculation In order to investigate the adsorbed configuration of CO2 within the UMC-1, unit cell systems containing CO2 molecule and adsorption sites selected from the configurations obtained from the GCMC simulation were constructed. The GCMC simulation provided well-behaved adsorption isotherms at 273 and 298 K up to 1 bar and Qst of CO2 adsorption (Figure 4.2.3). Each adsorbed CO2 molecule at these sites was further optimized using DFT calculations to determine the most energetically favorable configuration of CO2 and location of adsorption (Figs.
At site Ⅱ-b, CO2 interacts with SO2 groups at an O2=C···O2=S distance of 3.078 Å, which is consistent with the results of a previous study on sulfonyl-functionalized Zr MOFs.44 Site Ⅲ, where the The ∆EBE of CO2 is −31.089 kcal/mol, is located outside the cages and forms many weak interactions to stabilize CO2 adsorption (Figure 4.2.7). Enhancement of the CO2 separation capacity of a metal-organic framework by post-synthetic ligand exchange with flexible aliphatic carboxylates. Highly efficient separation of carbon dioxide through a metal-organic framework full of open metal sites.
Tuning of metal-organic frameworks with open metal sites and its origin for CO2 affinity enhancement by metal substitution. A three-phase modulated hydrothermal approach for the synthesis of multivariate metal-organic frameworks with hydrophobic moieties for highly efficient moisture-resistant CO2 capture.
Summary and Future Perspectives
Summary
In Chapter 4, we presented a theoretical investigation of the preferential adsorption of gas molecules in rationally designed porous materials that include inorganic interaction sites, such as metal halides or functional groups. DFT calculations of the binding energy of CO and related electronic structure analyzes with bimetallic Cu(Ⅰ)Zn(Ⅱ)-incorporating MIL-100(Fe) revealed that Zn(Ⅱ) doping increased the occupancy in the bonding orbitals near the Fermi level, while when it reduces the occupancy in the antibonding orbitals, thereby increasing the bond strength between Cu sites and CO molecules. In addition, DFT calculations showed that Zn(Ⅱ) species can form more stable intermediate states when Fe(Ⅲ) is reduced to Fe(Ⅱ).
Meanwhile, in the UMC-1, multiple binding sites made by functional groups (μ2-OH and –SO2–) and favorable pore geometry contributed to the exceptionally strong CO2 adsorption in newly synthesized metallocages. Finally, we investigated the selective adsorption and diffusion phenomena of gas molecules in various porous materials, such as oriented zeolite membrane, aromaticity enhanced MOFs and MOF-based materials incorporating inorganic adsorption sites, using multiscale simulation methods. We expect that our theoretical study provides a basic understanding of the mechanisms of gas separation in porous materials from a molecular point of view and suggests a new strategy for the design of new materials for energy-efficient adsorption and membrane-based separation processes.
Future Perspectives
Jeong Hyeon Lee†, Jin Chul Kim†, Woo Cheol Jeon†, Soo Gyeong Cho* og Sang Kyu Kwak*,. Kyung Ho Cho, Ji Woong Yoon, Jeong Hyeon Lee, Jin Chul Kim, Kiwoong Kim, Jong-San Chang*, Sang Kyu Kwak*, U-Hwang Lee*, "Separation af ethan/ethylengasblanding ved ethan-selektiv. Oh†, Sung-Ha Park†, Jeong Hyeon Lee, Jin Chul Kim, Jong Bum Lee, Hyeong Ju Eun, Yun-Sang Lee, Bo Eun Seo, Woojin Yoon, Hoseop Yun, Sang Kyu Kwak*, O-Pil Kwon* og Jong H.
Xiaobo Shang†, Inho Song†, Myeonggeun Han, Jeong Hyeon Lee, Hiroyoshi Ohtsu, Wanuk Choi, Jin Chul Kim, Jaeyong Ahn, Sang Kyu Kwak and Joon Hak Oh*, “Majority Rules” Effect on Supramolecular Chirality and Optoelectronic Properties of Chiral Tetrachloroperylene Diimides". From Nhieu Le†, The Ky Vo†, Jeong Hyeon Lee, Jin Chul Kim, Tea-Hoon Kim, Kwang Hyun Oh, Youn-Sang Bae*, Sang Kyu Kwak* and Jinsoo Kim*, "New Approach for preparation. Xiaobo Shang†, Inho Song†, Jeong Hyeon Lee, Wanuk Choi, Jaeyong Ahn, Hiroyoshi Ohtsu, Jin Chul Kim, Jin Young Koo, Sang Kyu Kwak* and Joon Hak Oh*, “Surface-Doped Quasi-2D Chiral Organic Single Crystals for chiroptical detection".
Kyung Ho Cho, Ji Woong Yoon, Jeong Hyeon Lee, Jin Chul Kim, Kiwoong Kim, U-Hwang Lee, Sang Kyu Kwak*, and Jong-San Chang*, "Effect of framework rigidity in metal-organic frameworks for adsorptive separation of ethane /ethylene". Xiaobo Shang†, Inho Song†, Jeong Hyeon Lee, Myeonggeun Han, Jin Chul Kim, Hiroyoshi Ohtsu, Jaeyong Ahn, Sang Kyu Kwak*, and Joon Hak Oh*, “Tuning supramolecular chirality and optoelectronic performance of chiral perylene diimides via N Nanowire -Replace Side Chain Xiaobo Shang†, Inho Song†, Jeong Hyeon Lee, Wanuk Choi, Hiroyoshi Ohtsu, Gwan Yeong Jung, Jaeyong Ahn, Myeonggeun Han, Jin Young Koo, Masaki Kawano, Sang Kyu Kwak* and Joon Hak Oh* , “Heterochiral shelled supramolecular coordination networks for high-performance optoelectronics”.
Xiaobo Shang†, Inho Song†, Gwan Yeong Jung, Wanuk Choi, Hiroyoshi Ohtsu, Jeong Hyeon Lee, Jin Young Koo, Bo Liu, Jaeyong Ahn, Masaki Kawano, Sang Kyu Kwak* and Joon Hak Oh*. Soochan Lee, Jeong Hyeon Lee, Jin Chul Kim, Sungmin Lee, Sang Kyu Kwak* en Wonyoung Choe*, "Porous Zr6L3 Metallocage met synergetische bindingscentra voor CO2".
