Molecular Simulations Of Thiophene / Benzene Adsorption In Novel Skeleton Materials

Metal-Organic Frameworks and Covalent Organic Frameworks are new families of nanoporous frameworks materials. Due to their porosities, extremely high accessible areas, chemical diversities and designed structures, they have been recongised as the frontier area and hotspot in the field of materials. With the development of computer, the method of molecular simulation has been broken through the limitations of traditional methods, it has been wildly used to study the structure and properties of materials by Canonical Monte Carlo(MC).In this work, grand Canonical Monte Carlo(GCMC) is used for investigating the thiophene, benzene and alkanes mixture adsorption separation in Metal-Organic Frameworks and Covalent Organic Frameworks. The main results are the bellow.First, for this study, eight ZIFs matetials (ZIF-2,-3,-6,-8,-10,-68,-69 and -79) with different pore sizes were adopted as the respresentative of MOF solid. Then Grand Canonical Monte Carlo(GCMC) simulation were performed to investigate the adsorption of pure component thiophene and benzene and the separation of thiophene/benzene mixture and thiophene/benzene/o-ctane mixture in these ZIFs materials. The simulation results show that the calculated amount absorbed of benzene in ZIF-8 is agreement with the experiment data. For pure component, at low pressures, the extent of adsorption is small corresponding to cluster formation at preferential adsorption sites. The preferential adsorption sites are located in the organic ligand and C=C.Due to size entropy effects for some ZIFs, thiophene molecules adsorb more strongly than benzene in ZIF-3. Because there are many preferential adsorption sites for adsorption of benzene in ZIF-79, thus the calculated amount absorbed of benzene is higher than that of others ZIFs. Binary mixture simulations at two different compositions show that ZIF-3 is very selective towards thiophene over benzene at 363 K. The thiophene selectivity shows a significant dependence on pore size in binary mixtures, and the smaller thiophene molecule can replace the benzene at elevated pressures due to size entropy effects for the selected ZIFs. For ternary mixtures of thiophene, benzene and alkanes, the results show that the selectivity is low in ZIF-2,-6,-10,-68,-69 and -79, while the presence of n-octane has insignificant effects on the thiophene selectivity in ZIF-3.Second, GCMC simulations were also performed to evaluate the adsorption of pure component thiopehene and benzene and the separation of thiophene/benzene mixture in four CPO-27-M matetials (CPO-27-Mg, CPO-27-Co, CPO-27-Ni and CPO-27-Zn) at 303 K. The simulation resuslts show that the amount absorbed of benzene is higher than that of thiophene at low pressure. At the same time, the amount absorbed of thiophene is the highest in CPO-27-Mg. For ternary mixtures of thiophene and benzene, the results show that the the selectivity is low in CPO-27-Mg, CPO-27-Ni and CPO-27-Zn, while the thiophene selectivity reaches to 3 in CPO-27-Co.Third, we have studied four COFs matetials (COF-1,-6,-102 and-103). Grand Canonical Monte Carlo(GCMC) were performed to investigate the adsorption of pure component thiopehene and benzene and the separation of thiophene/benzene mixture and thiophene/benzene/o-ctane mixture in these COFs matetials. The simulation results show that the calculated amount absorbed of thiophene and benzene in three-dimensional COF is higher than that of them in two dimensional COF in the whole pressure range. The high specific surface area and free pore volume of COF-102 and COF-103 play an important role, regardless of the pore size. For three-dimensional COF, the amount absorbed of thiophene is higher than benzene at high perssure.This is because the configuration of thiophene match well with COF-102 and COF-103. Binary mixture simulations at two different compositions show that the absorbed of thiophene and benzene in COF-1 and COF-6 belong to volume-filling, while the adsorption of thiophene and benzene in COF-102 and COF-103 comform competetion. For ternary mixtures of thiophene, benzene and n-pentane, the results show that the the selectivity is low in COF-1 and COF-6, while the presence of n-pentane has insignificant effects on the thiophene selectivity in COF-102 and COF-103.