Efficient Xe/Kr Separation Based on a Lanthanide–Organic Framework with One-Dimensional Local Positively Charged Rhomboid Channels

Efficient xenon/krypton (Xe/Kr) separation has played an important role in industry due to the wide application of high-purity Xe and with regard to the safe disposal of radioactive noble gases (85Kr and 133Xe). A less energy-demanding separation technology, adsorptive separation using porous solid materials, has been proposed to replace the traditional cryogenic distillation with intensive energy consumption. As a cutting-edge class of porous materials, metal-organic frameworks (MOFs) featuring permanent porosity, designable chemical functionalities, and tunable pore sizes hold great promise for Xe/Kr separation. Here, we report a two-dimensional (2D) lanthanide-organic framework (termed LPC-MOF, [Eu(Ccbp)(NO3)(HCOO)]·DMF0.3(H2O)2.5) with one-dimensional (1D) local positively charged rhomboid channels whose size matches well with the kinetic diameter of Xe, leading to its superior Xe/Kr separation performance. Column breakthrough experiments demonstrate that LPC-MOF exhibits a high Xe/Kr selectivity of 12.4 and an Xe adsorption amount of 3.39 mmol kg-1 under simulated conditions for real used nuclear fuel (UNF)-reprocessing plants. Furthermore, density functional theory (DFT) calculations elucidate not only the intrinsic mechanisms of Xe/Kr separation at the molecular level but also the detailed influence of the local positive charge (N+) on the performance of Xe/Kr separation in the MOF system.