Asymmetric recognition in metal-organic frameworks for enhanced ethylene/ethane sieving.

Ethylene/ethane (C2H4/C2H6) separation is one of the most energy-intensive processes in the petrochemical industry, highlighting the urgent need for efficient adsorbents to replace cryogenic distillation. In this work, a new metal-organic framework (MOF), TYUT-25, is constructed via an asymmetric recognition strategy to achieve directional regulation of adsorption behavior within channels. In conventional systems, structural modulation typically induces a synchronous adsorption response, where C2H4 and C2H6 uptake increase or decrease simultaneously, thereby limiting further improvements in selectivity. In contrast, the asymmetric recognition strategy results in inverse adsorption behaviors of C2H4 and C2H6. The pore aperture is contracted to suppress C2H6 entry, thereby enabling size-sieving discrimination between C2H4 and C2H6, while the pore cavity enhances interactions between C2H4 and the framework, leading to enhanced C2H4 uptake and suppressed C2H6 adsorption. Compared with Zn(BPA)(BDC), adsorption measurements show that the C2H4 uptake of TYUT-25 increases from 1.6 to 8.4 cm3 g-1 at 0.1 bar and reaches 34.4 cm3 g-1 at 1 bar. At 298 K and 1 bar, the C2H4/C2H6 selectivity exceeds 104. Breakthrough experiments further verify separation performance. DFT calculations and Hirshfeld surface analysis indicate enhanced host-guest interactions. This work demonstrates that asymmetric recognition enables inverse adsorption responses, providing an effective strategy for the coordinated regulation of adsorption capacity and selectivity within a MOF.