A cation gating–breathing synergetic mechanism in K-MER-2.0 zeolite enables unprecedented selective CO2 separation from hydrocarbon gas streams

Abstract

The ubiquitous presence of CO₂ impurities in industrial hydrocarbon streams underscores the critical need for developing efficient CO₂-selective adsorbents. Herein, we synthesized a flexible K-MER-2.0 (a silica–alumina ratio of 2.0) zeolite without using an organic template, which demonstrates exceptional selective adsorption performance in CO₂/hydrocarbon systems, and in particular achieves the unprecedented reverse separation of CO₂/C₂H₂. K-MER exhibits a CO₂ adsorption capacity of 70.9 cm³ g⁻¹ under ambient conditions, accompanied by a remarkable CO₂/C₂H₂ uptake ratio (13.4). Breakthrough experiments conducted with a CO₂/C₂H₂ (50/50, v/v) mixture reveal that K-MER-2.0 delivers a high dynamic CO₂ adsorption capacity (65.1 cm³ g⁻¹) and separation factor (12.1), and in particular a high C₂H₂ yield of 1872 mmol kg⁻¹, establishing a benchmark for CO₂/C₂H₂ reverse separation. The rapid adsorption kinetics, excellent regeneration and robust moisture resistance of K-MER-2.0 further confirmed its application potential under harsh practical conditions. Mechanistic analyses, including CO₂/C₂H₂ adsorption isotherms, in situ CO₂ powder X-ray diffraction (PXRD) patterns and periodic density functional theory (DFT) calculations, reveal a unique CO₂-triggered cation gating—breathing synergetic mechanism in K-MER-2.0 zeolite. This stimulus-responsive mechanism facilitates selective framework expansion during CO₂ adsorption while preserving a constricted pore geometry that excludes C₂H₂. Such discriminative structural adaptability drives the record-breaking separation performance of the material. Additionally, the unique recognition ability for CO₂ endows K-MER-2.0 with good dynamic separation ability for binary mixtures of CO₂/hydrocarbons.