官能团及修饰位点对金属有机骨架化合物（MOFs）CO2/CH4分离性能的影响:蒙特卡洛模拟研究（英文）

Influence of Functional Groups and Modification Sites of Metal-Organic Frameworks on CO2/CH4 Separation:A Monte Carlo Simulation Study

本文采用巨正则蒙特卡罗（GCMC）模拟，研究金属有机骨架中官能团修饰的种类及位点对垃圾填埋气（CO2／CH4）吸附分离性能的影响．选用六种不同有机配体，分别组成六种铜基pcu构型MOFs，并采用三种官能团（-F、-NH2、-CH3）对其有机配体上距金属团簇不同距离的位点进行修饰，获得36种MOFs结构，并对它们在低压真空变压吸附（VsA）和高压变压吸附（PSA）的C02／CH4分离性能进行模拟．结果表明，在低压下，未修饰MOFs的CO2吸附量呈现出随孔径增大而减小的趋势．三种官能团中，-NH2修饰的MOFs因其强库伦相互作用而具有最优的C02吸附性能，其次，具有强范德华相互作用的MOF—CH3，而-F具有吸电子效应，且其作为单原子官能团的弱范德华相互作用使得它的C02吸附性能略逊于未修饰MOFs．此外，将官能团修饰于距金属团簇较远的位点（位点b）时，所造成的影响比修饰于近位点（位点a）更明显．

In order to explore the influence of modification sites of functional groups on landfill gas （CO2/CH4） separation performance of metal-organic frameworks （MOFs）, six types of or- ganic linkers and three types of functional groups （i.e. -F, -NH2, -CH3） were used to construct 36 MOFs of pcu topology based on copper paddlewheel. Grand canonical Monte Carlo sim- ulations were performed in this work to evaluate the separation performance of MOFs at low （vacuum swing adsorption） and high （pressure swing adsorption） pressures, respectively. Simulation results demonstrated that CO2 working capacity of the unfunctionalized MOFs generally exhibits pore-size dependence at 1 bar, which increases with the decrease in pore sizes. It was also found that -NH2 funetionalized MOFs exhibit the highest CO2 uptake due to the enhanced Coulombic interactions between the polar -NH2 groups and the quadrupole moment of CO2 molecules, which is followed by -CH3 and -F functionalized ones. Moreover, positioning the functional groups -NH2 and -CH3 at sites far from the metal node （site b） exhibits more significant enhancement on CO2/CH4 separation performance compared to that adjacent to the metal node （site a）.