Molecular simulations of adsorption and separation of acetylene and methane and their binary mixture on MOF-5, HKUST-1 and MOF-505 metal-organic frameworks

In this work, the adsorption of acetylene and its binary mixture with methane on MOF-5, HKUST-1 and MOF-505 was studied using Grand Canonical Monte Carlo molecular simulations. The preferred adsorption sites of acetylene and methane molecules into metal-organic frameworks (MOFs) were investigated. The simulated adsorption isotherms of acetylene on MOF-5 and MOF-505 agreed well with the experimental ones without any reparameterisation of the potential parameters but for HKUST-1 the interaction parameters of the acetylene and copper ion were reparameterised. Comparisons of the calculated adsorption isotherms of acetylene in the studied MOFs showed that the MOF-5 had the lowest adsorption capacity. Our results revealed that guest molecules were most adsorbed on the entrance windows of the octagon pore of HKUST-1, while the preferred adsorption sites were large pores and on the metal ion cluster of MOF-505 and MOF-5, respectively. Adsorption of binary mixtures of methane and acetylene on MOF-5, HKUST-1 and MOF-505 revealed that acetylene adsorption is higher than that of methane. Finally, the results showed that C2H2/CH4 selectivity values on HKUST-1 are significantly higher than on MOF-505 and MOF-5. The preferred adsorption sites of acetylene and methane in an equimolar binary mixture were calculated and discussed.