The separation of C 3 H 6 and C 3 H 8 has been a technical challenge owing to their similar physical and chemical properties. The currently used separation technologies still suffer from the low efficiency, high operating cost and volatility of media, which urges researchers to develop greener and more efficient media. To achieve this, a series of protic cuprous-based ionic liquids (PCILs) combining both cuprous site and long alkyl chain were designed in this work for the absorption separation of C 3 H 6 and C 3 H 8 . Surprisingly, the solubility of C 3 H 6 in [TOAH][CuCl 2 ] is as high as 0.238 mol/kg at 313 K and 1.0 bar, which exceeds most of results reported so far. The experimental data and thermodynamic analysis showed that extending alkyl chain of ILs promoted the dissolution of C 3 H 6 and C 3 H 8 , while the introduction of Cu(I) improved the selectivity of C 3 H 6 /C 3 H 8 . In addition, the interaction mechanism of C 3 H 6 and C 3 H 8 with ILs was further clarified by quantum chemical calculations and FT-IR spectroscopy. Furthermore, regeneration of [TOAH][CuCl 2 ] can be easily realized under depressurizing condition without heating and loss in separation performance, and [TOAH][CuCl 2 ] was found very stable to both moisture and oxygen for at least fifteen days. The strategy of combining long-chain alkyl and Cu(I) site in this work may provide an important guideline for enhancing C 3 H 6 /C 3 H 8 selectivity, but more efforts on enhancing Cu(I) activity still need to be made for improving C 3 H 6 /C 3 H 8 selectivity.
Realizing ideal deuterium separation from isotopic mixtures remains a daunting challenge because of their almost identical sizes, shapes, and physicochemical properties. Using the quantum sieving effect in porous materials with suitable pore size and open metal sites (OMSs) enables efficient hydrogen isotope separation. Herein, synthetic HKUST-1-derived microporous mixed-valence Cu(I)Cu(II)-BTC (BTC = benzene-1,3,5-tricarboxylate), featuring a unique network of distinct Cu(I) and Cu(II) coordination sites, can remarkably boost the D2/H2 isotope separation, which has a high selectivity (SD2/H2) of 37.9 at 30 K, in comparison with HKUST-1 and other porous materials. Density functional theory (DFT) calculations indicate that the introduction of Cu(I) macrocycles in the framework decreases the pore size and further leads to relatively enhanced interaction of H2/D2 molecules on Cu(II) sites. The significantly enhanced selectivity of Cu(I)Cu(II)-BTC at 30 K can be mainly attributed to the synergistic effect of kinetic quantum sieving (KQS) and chemical affinity quantum sieving (CAQS). The results reveal that Cu(I) OMSs exhibit counterintuitive behaviors and play a crucial role in tuning quantum sieving without a complex structural design, which provides a deeper insight into quantum sieving mechanisms and a new strategy for the intelligent design of highly efficient isotope systems.
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