A Porous MOF Containing Accessible Open Metal Sites with Low Steric Hindrance for Selective Separation of Hydrocarbons.

Conventional hydrocarbon production yields impure products, while solvent-based purification techniques emit volatile pollutants and are energy-intensive. Metal-organic frameworks (MOFs) with open metal sites (OMSs) offer an energy-efficient and eco-friendly alternative, yet steric hindrance from OMSs with traditional geometries restricts multimolecule adsorption. Herein, a stable Ni-MOF incorporating novel seesaw-geometry OMSs was constructed using a 1,3,5-tris(pyrazolyl)benzene ligand. Owing to the presence of accessible low-steric resistance OMSs, the activated MOF displays exceptional binding affinities for CO2 and C2H2 over C2H4 and CH4, as well as high ideal adsorbed solution theory (IAST) selectivities for C2H2-CO2, C2H2-C2H4, C2H2-CH4, and CO2-CH4 mixtures. Experimental breakthrough curves further validated the potential of Ni-MOF for industrial C1/C2 hydrocarbon purification. Grand canonical Monte Carlo (GCMC) simulations revealed that the low-steric resistance OMSs could interact strongly with more C2H2 and CO2 molecules, leading to higher affinities and separation abilities.