Gate-Tailoring with Protons and Metal Cations in a Flexible Zeolite for High-Efficiency Ethylene/Ethane Separation

Ethylene/ethane separation underpins global polyolefin production but remains one of the most energy-intensive processes in the chemical industry because it relies on cryogenic distillation. Adsorptive separation using porous materials offers a promising alternative to conventional cryogenic distillation, potentially reducing energy consumption. However, the nearly identical physical properties of ethylene and ethane make the development of highly selective adsorbents exceptionally challenging. Herein, we report a lithium-exchanged silicoaluminophosphate RHO zeolite (Li-SAPO-RHO) that achieves unprecedented ethylene/ethane separation by exploiting a cooperative gating mechanism in a flexible framework. A synergistic proton-Li⁺ gating effect at the flexible 8-ring apertures differentially modulates molecular transport barriers. Brønsted protons selectively facilitate ethylene diffusion, while Li⁺ cations create a trapdoor barrier that preferentially suppresses ethane transport, thereby amplifying kinetic discrimination. As a result, Li-SAPO-RHO exhibits excellent ethylene-selective adsorption performance, enabling the direct production of polymer-grade ethylene (>99.9%) from refinery dry gas with a productivity of 238.6 mmol/L. Structural analyses combined with ab initio molecular dynamics simulations reveal how proton-cation synergy amplifies kinetic discrimination between closely related molecules. These findings establish gate cooperativity as a powerful design principle for energy-efficient adsorptive separations. Due to its low cost, exceptional hydrothermal stability, and excellent cycling performance, Li-SAPO-RHO offers a promising platform for industrial light-olefin separations.