Fluorinated metal-organic framework for methane purification from a ternary CH4/C2H6/C3H8 mixture

Herein we present a fluorinated metal-organic framework of {(Me2NH2)[Ni3(μ3-OH)(CF3-BPDC-CF3)3(tpt)]}n (1) constructed from 2,2'-bis(trifluoromethyl)biphenyl-4,4'-dicarboxylic (CF3-BPDC-CF32‒) and 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) ligands, which is developed for separating propane (C3H8) and ethane (C2H6) from natural gas. Compound 1 preferentially adsorbs C3H8 and C2H6 over CH4 demonstrated by gas adsorption experiments. The presence of trifluoromethyl groups on the biphenyl-4,4'-dicarboxylic ligands facilitates the highly polarized micropore environments for compound 1, thus providing suitable micorpores for capturing the C3H8 and C2H6 molecules with larger polarizabilities and sizes compared to CH4 molecule. The dynamic mixture breakthrough experiments showed that compound 1 can separate C3H8 and C2H6 from the ternary CH4/C2H6/C3H8 mixtures efficiently, endowing compound 1 with excellent methane purification ability.