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The separation of structurally similar compounds, such as cholic acid (CA) and deoxycholic acid (DCA), is challenging due to their nearly identical physicochemical properties. This study demonstrates a synergistic 'push and pull' strategy with an ionic liquid (IL) biphasic system for significantly enhanced CA/DCA separation efficiency. Ethyl acetate was selected as the feed solvent to 'push' CA into the IL-rich extractant phase, while the IL 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) was chosen to 'pull' CA due to their strong hydrogen bonding interaction. This 'push and pull' system yielded a remarkable CA/DCA selectivity up to 47.8, much higher than the case using n-butanol which pulls both CA and DCA. The underlying separation mechanism was elucidated through computational screening with COSMO-RS, NMR analysis, and solvatochromic measurements. Results revealed the critical roles of specific hydrogen bonding between the chloride anion of [EMIM]Cl and the hydroxyl/carboxyl groups of CA/DCA, along with nonspecific interactions between the feed solvent and CA/DCA. Thermodynamic analysis of the phase transfer process confirmed the 'push and pull' synergy is energetically favorable for preferentially transferring CA from the ethyl acetate feed solution into the IL-rich extractant phase. Multi-stage simulation indicated that 99% purity and recovery of both CA and DCA can be obtained through this biphasic system under optimized conditions. Overall, strategically tuning both the feed solvent and IL extractant could significantly enhance the separation efficiency of structurally similar compounds while minimizing solvent and energy consumption. This 'push and pull' approach may shed light on improving separation processes for other structural analogues. [ABSTRACT FROM AUTHOR]

Removal of the CO 2 impurities from C 2 H 2 /CO 2 mixtures is an essential process to produce high-purity C 2 H 2 . Fabricating an adsorbent capable of discriminating these species, which have close kinetic diameters, is critical for developing advanced adsorption processes. Herein, we demonstrate a strategy to exploit the tunability of interlayer and intralayer spaces of two-dimensional (2D) layered metal-organic frameworks to achieve high performance for C 2 H 2 /CO 2 separation. This indicates that interlayer symmetrical control can achieve more efficient packing of C 2 H 2 into Ni(4-DPDS) 2 CrO 4 , with a high C 2 H 2 capacity of 45.7 cm 3 ·g -1 at 0.01 bar and a selectivity of 67.7 (298 K, 1 bar), which strikes a good balance between working capacity and separation selectivity compared to other isostructural Ni(4-DPDS) 2 MO 4 (M = Mo, W). Crystallographic studies and DFT-D calculations reveal that such a C 2 H 2 -selective adsorbent possesses strong binding interactions due to the tailored pore confinement provided by the angular anions and rich electronic environment. Experimental breakthrough results comprehensively demonstrate the efficient C 2 H 2 /CO 2 separation performance of this unique material.