Double-Accessible Open-Metal Sites in Metal-Organic Frameworks with Optimal Pore Size for Efficient Xe/Kr Separation

The separation of Xe/Kr mixture is an industrially important but challenging process due to their inherent inert nature and similar atomic size. Porous materials containing open metal sites have been extensively proved to be an effective strategy for the Xe/Kr capture and separation. However, conventional materials with single open metal sites display the limitations of gas uptake at low pressure and separation selectivity of Xe/Kr mixture. Herein M(pz)[Ni(CN) 4 ], simplify as MpzNi (M = Co, Ni, pz = pyrazine), with optimal pore size and double accessible open metal sites, can synergistically afford strong interactions for Xe capture from Xe/Kr mixture. CopzNi exhibits high uptake of 2.49 mmol/g at 0.2 bar and remarkable dynamic adsorption amount of Xe (2.35 mmol/g), outperforming most of previously reported materials. DFT calculations further reveal that the excellent separation performance is driven by the compact pore size and cooperative interactions afforded by the double accessible open metal sites