烷烃在金属有机骨架MOF-5和Cu-BTC中吸附的蒙特卡罗模拟

Monte Carlo simulation for the adsorption of alkanes in metal-organic frameworks MOF-5 and Cu-BTC

采用蒙特卡罗方法(Monte Carlo,MC)研究烷烃在2种典型的金属有机骨架MOF-5和Cu-BTC(BTC,均苯三甲酸)中的吸附.模拟298 K下烷烃(CH4、C2H6、C3H8、正丁烷、正戊烷)在MOF-5和Cu-BTC中单组分吸附等温线,结果表明:随着压力的增加,烷烃的吸附量变大.在低压部分,吸附量由小到大的顺序是:CH4、C2H6、C3H8、正丁烷、正戊烷;而在高压部分,吸附量由小到大的顺序是:正戊烷、正丁烷、C3H8、C2H6、CH4.分析烷烃在MOF-5和Cu-BTC中的位置分布,得到烷烃在MOF-5和Cu-BTC中填充顺序:在MOF-5中,烷烃首先吸附在金属氧化物团簇Zn4O周围,然后进入孔道中间;在Cu-BTC中,烷烃首先吸附在四面体型的边孔道中,然后进入主孔道中.

The adsorption of alkanes in two representative metal-organic frameworks （MOFs） ： MOF-5 and Cu-BTC （BTC,benzene-1,3,5-tricarboxylate） had been simulated using Monte Carlo method. The single component adsorption isotherms of alkanes （methane, ethane, propane, n-butane, n-pentane） in MOF-5 and Cu-BTC at 298 K had been simulated. The results indicated that the adsorbed amounts increased with increasing pressure. At low pressures, adsorbed amounts were in the order of methane 〈 ethane 〈 propane 〈 n-butane 〈 n-pentane. While, at high pressures, adsorbed amounts were in the order of n-pentane 〈 n-butane 〈 propane 〈 ethane 〈 methane. The adsorption sites of alkanes in MOF-5 and Cu-BTC were analyzed and the sequences of pore filling in MOF-5 and Cu-BTC were obtained： in MOF-5, alkanes first occupied near metal oxide Zn4O clusters, then occupied the center of the cavities; in Cu-BTC, alkanes first occupied the tetrahedron-shaped side pockets, then occupied the main channels.