Rational Design of a Multifunctional MOFs for Alkane-Selective Gas Separation

Efficient separation of light hydrocarbons-including the removal of CH₄ from N₂ and the purification of olefins such as C₂H₄ and C₃H₆ from their corresponding alkanes (C₂H₆ and C₃H₈)-is critical in natural gas upgrading, steam cracking, and downstream petrochemical production. Traditional adsorbents are tailored to specific mixtures, limiting their broader applicability. The development of multifunctional adsorbents that can efficiently operate across multiple gas separation systems represents a promising strategy to simplify material design and broaden industrial relevance. Herein, methyl-functional groups are innovatively introduced into porous coordination polymers (PCPs), synthesizing PCP-BDC-M and PCP-BDC-DM with precisely tailored microporous structures. Notably, the dimethyl-functionalized PCP-BDC-DM demonstrates superior multifunctional selectivity toward CH₄/N₂, C₂H₆/C₂H₄, and C₃H₈/C₃H₆ gas mixtures. Adsorption isotherms and Ideal Adsorbed Solution Theory (IAST) calculations reveal significantly higher alkane selectivity in PCP-BDC-DM compared to PCP-BDC-M and existing alkane-selective adsorbents. Grand Canonical Monte Carlo (GCMC) simulations provide molecular-level insight, confirming that methyl groups effectively enhance interactions between alkane molecules and the framework. Dynamic breakthrough experiments further validate PCP-BDC-DM's excellent practical separation capability and structural stability. This study offers valuable insights into designing advanced adsorbents for alkane-selective gas separation.