Separation of Natural Gas and Flue Gas Based on Lanthanide Organic Frameworks: The Role of Pore Environment in the Pore Surface

Capturing CO₂ from natural gas and flue gas is of critical importance for energy conservation and achieving carbon-neutrality goals, yet it remains a significant challenge. Herein, we report two novel and stable 3D lanthanide MOFs, LCUH-123 and LCUH-124, which demonstrate remarkably selective CO₂ adsorption over CH₄ and N₂, exhibiting excellent separation performance for both CO₂/CH₄ and CO₂/N₂ gas mixtures. LCUH-123's channel is obstructed by two coordinated DMF molecules, leading to near-complete blockage and a significantly reduced adsorption capacity. In contrast, LCUH-124's micropores are enriched with H₂O-coordinated sites and free [(CH₃)₂NH₂]⁺ cations, enabling superior gas adsorption and separation performance. Compared to LCUH-123, LCUH-124 exhibits significantly improved gas adsorption and separation performance, achieving higher selectivity coefficients for CO₂/N₂ and CO₂/CH₄ at zero coverage. Breakthrough experiments confirm that LCUH-124 serves as an efficient adsorbent for high-purity separation of CH₄ and N₂ from binary CO₂/CH₄ and CO₂/N₂ mixtures. Furthermore, its cost-effective synthetic process offers substantial economic advantages for large-scale applications. Theoretical calculations have elucidated the distinct adsorption and separation mechanisms of CO₂/CH₄ and CO₂/N₂ mixtures in LCUH-124. The exceptional performance of LCUH-124 stems from its rationally engineered pore architecture and cavity-directed coordination of water molecules with [NH₂(CH₃)₂]⁺ cations within the channel.