• A novel Co-MOF with open metal sites exhibits superior adsorption capacity for C2-C3 hydrocarbons over CH4, enabling efficient separation.
• Ideal adsorbed solution theory calculations show remarkable equilibrium separation selectivity for C2H6/CH4 and C3H8/CH4 at 273/298 K and 0.1 MPa.
• Dynamic breakthrough experiments confirm the practical ability of Co-MOF to purify methane from C2-C3 hydrocarbon mixtures.
• Molecular simulations reveal that anionic SBUs preferentially interact with C2-C3 hydrocarbons, providing a design paradigm for porous MOF adsorbents.