Specific Propyne Trapping Sites within a Robust MOF for Efficient Propyne/Propadiene Separation with Record Propadiene Productivity

Separating propyne/propadiene to produce pure propadiene is extremely challenging in industry due to their similar properties. Herein, a novel ZrF₆^2- anion pillared cage-like metal-organic framework (termed as CuZrF₆-TPA) for highly efficient propyne/propadiene separation is reported. It exhibits high propyne capacity (177.4/188.6 cm³/cm³ at 0.5/1.0 bar and 298 K), benchmark separation selectivity (6.0), and remarkable separation potential (5.7 mol L^-1 ) simultaneously. Record propadiene productivity (≈4.7 mol L^-1 ) is achieved through a single adsorption process in breakthrough experiments with excellent recycle stability even under humid conditions. Based on the structure of propyne-loaded single crystals, two binding sites are identified, including a major propyne trapping site at the windows and a minor binding site located in the large cages. Modelling studies further confirm that the contracted cage windows surrounded with rotating Lewis basic F atoms and aromatic rings are the optimal bonding sites to capture propyne with multiple hydrogen bonding and π···π interactions.