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.