Tailoring a robust Al-MOF for trapping C(2)H(6) and C(2)H(2) towards efficient C(2)H(4) purification from quaternary mixtures

Light hydrocarbon separation is considered one of the most industrially challenging and desired chemical separation processes and is highly essential in polymer and chemical industries. Among them, separating ethylene (C(2)H(4)) from C2 hydrocarbon mixtures such as ethane (C(2)H(6)), acetylene (C(2)H(2)), and other natural gas elements (CO(2), CH(4)) is of paramount importance and poses significant difficulty. We demonstrate such separations using an Al-MOF synthesised earlier as a non-porous material, but herein endowed with hierarchical porosity created under microwave conditions in an equimolar water/ethanol solution. The material possessing a large surface area (793 m(2) g(−1)) exhibits an excellent uptake capacity for major industrial hydrocarbons in the order of C(2)H(2) > C(2)H(6) > CO(2) > C(2)H(4) > CH(4) under ambient conditions. It shows an outstanding dynamic breakthrough separation of ethylene (C(2)H(4)) not only for a binary mixture (C(2)H(6)/C(2)H(4)) but also for a quaternary combination (C(2)H(4)/C(2)H(6)/C(2)H(2)/CO(2) and C(2)H(4)/C(2)H(6)/C(2)H(2)/CH(4)) of varying concentrations. The detailed separation/purification mechanism was unveiled by gas adsorption isotherms, mixed-gas adsorption calculations, selectivity estimations, advanced computer simulations such as density functional theory (DFT), grand canonical Monte Carlo (GCMC) and ab initio molecular dynamics (AIMD), and stepwise multicomponent dynamic breakthrough experiments.