An anion-pillared ultra-microporous MOF with synergistic binding sites for efficient C2H2/CO2 separation

The separation of acetylene (C 2 H 2 ) from carbon dioxide (CO 2 ) and its subsequent storage remain formidable challenges in the petrochemical industry due to their nearly identical kinetic diameters and similar physical properties, which render conventional adsorption methods inefficient. Herein, we report an anion-pillared ultra-microporous metal–organic framework, Ni-TiF 6 -T4PP, engineered with tailored pore geometry and selective binding sites to achieve efficient C 2 H 2 /CO 2 separation. This material exhibits a high C 2 H 2 uptake of 3.99 mmol g −1 at 298 K and 1 bar. The pore environment, enriched with nitrogen and fluorine sites, promotes host–guest interactions with C 2 H 2 , resulting in a substantial differential in the isosteric heats of adsorption (Q st ): 36.04 kJ mol −1 for C 2 H 2 versus 19.35 kJ mol −1 for CO 2 . Combined with its low regeneration energy barrier, the framework can be readily regenerated, contributing to its recyclability. Breakthrough experiments demonstrate achieves separation performance for equimolar C 2 H 2 /CO 2 mixtures. At 353 K, a C 2 H 2 mixture with an initial concentration of 90% can be purified to achieve a final purity of > 99.2%. Based on the combined evidence from in situ infrared spectroscopy and molecular simulation, the underlying gas adsorption mechanism has been conclusively established that the extended π-surfaces of porphyrin and pyridine moieties enable multipoint cooperative binding with C 2 H 2 .