Hierarchical metal-organic frameworks constructed from intergrowth for the adsorption of light hydrocarbons

Hierarchical metal organic frameworks (MOFs) are a type of MOF material with both micropores and mesopores. In this work, we demonstrate heterometallic hierarchical MOF particles formed by intergrowth of pillared MOFs. Pillared MOF MI2(ndc)2(dabco) (MI = Co, Ni, Cu, Zn, ndc = naphthalenedicarboxylic acid, dabco = 1,4-diazabicyclo[2.2.2]octane) particles were synthesized with various morphologies, on which MII2(ndc)2(dabco) (MII = Co, Ni, Cu, Zn) particles were intergrown. The intergrown particles preserved the structure, crystallinity, and morphology of their respective primary particles, while creating additional mesoporosity for gas adsorption. Adsorption of hydrocarbons (CH4, ethane, ethene, propane, and propene) at pressures up to 10 bar (absolute) was performed on the MOFs. Hierarchical MOFs have shown increased adsorption of hydrocarbons at low pressures, and IAST selectivity of propane/methane as high as 53 was observed (total pressure 1 bar, CH4 mole fraction: 0.8), suggesting that the hierarchical materials can be used for adsorptive removal of natural gas liquids from crude natural gas.