Highly Porous Ionic rht Metal-Organic Framework for H2 and CO2 Storage and Separation: A Molecular Simulation Study

被引:73
作者
Babarao, R. [1 ]
Eddaoudi, M. [2 ,3 ]
Jiang, J. W. [1 ]
机构
[1] Natl Univ Singapore, Dept Chem & Biomol Engn, Singapore 117576, Singapore
[2] Univ S Florida, Dept Chem, Tampa, FL 33620 USA
[3] 4700 King Abdullah Univ Sci & Technol, KAUST Adv Membranes & Porous Mat Ctr, Chem & Life Sci & Engn Div, Thuwal 239556900, Saudi Arabia
关键词
MONTE-CARLO-SIMULATION; HYDROGEN ADSORPTION; BUILDING-BLOCKS; BINARY-MIXTURES; CARBON-DIOXIDE; DIFFUSION; GASES; METHANE; WATER; SILICALITE;
D O I
10.1021/la100509g
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The storage and separation of H-2 and CO2 are investigated in a highly porous ionic rht metal-organic framework (rht-MOF) using molecular simulation. The rht-MOF possesses a cationic framework and charge-balancing extraframework NO3- ions. Three types of unique open cages exist in the framework: rhombicuboctahedral, tetrahedral, and cuboctahedral cages. The NO3- ions exhibit small mobility and are located at the windows connecting the tetrahedral and cuboctahedral cages. At low pressures, H-2 adsorption occurs near the NO3- ions that act as preferential sites. With increasing pressure, H-2 molecules occupy the tetrahedral and cuboctahedral cages and the intersection regions. The predicted isotherm of H, at 77 K agrees well with the experimental data. The H-2 capacity is estimated to be 2.4 wt % at 1 bar and 6.2 wt % at 50 bar, among the highest in reported MOFs. In a four-component mixture (15:75:5:5 CO2/H-2/CO/CH4) representing a typical effluent gas of H-2 production, the selectivity of CO2/H-2 in rht-MOF decreases slightly with increasing pressure, then increases because of cooperative interactions, and finally decreases as a consequence of entropy effect. By comparing three ionic MOB (rht-MOF, soc-MOF, and rho-ZMOF), we find that the selectivity increases with increasing charge density or decreasing free volume. In the presence of a trace amount of H2O, the interactions between CO2 and NO3- ions are significantly shielded by H2O; consequently, the selectivity of CO2/H-2 decreases substantially.
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页码:11196 / 11203
页数:8
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