High-Stability Pillar-Layered Zn/ZnCd-MOFs with Optimized Pores for Efficient Methane Purification

Abstract

Efficient methane (CH₄) purification is critical for the full utilization of clean natural gas in the petrochemical industry. Compared with conventional energy-intensive low-temperature distillation, adsorptive separation using porous metal-organic frameworks (MOFs) represents a more energy-efficient and high-performance alternative. Herein, we synthesized a series of layer-based Zn- and Zn/Cd-MOFs (LIFM-260–265) by regulating metal nodes and pillar ligands of different sizes to tailor their topologies and pore dimensions. Of these materials, the porous MOFs with pillar-layer structures (LIFM-263–265) enable simultaneous removal of ethane (C₂H₆) and propane (C₃H₈) from a CH₄/C₂H₆/C₃H₈ ternary mixture. Among them, LIFM-265 delivers the highest productivity of high-purity (>99.8%) CH₄ (7.92 mmol g^-1) based on single breakthrough curve tests, outperforming its analogues LIFM-263 and LIFM-264. Theoretical simulations reveal that the optimal pore structures and aromatic surface environments of LIFM-263–265 promote favorable interactions with C₂H₆ and C₃H₈ molecules, thus enhancing selective adsorption of C₂/C₃ hydrocarbons. This work provides valuable insights for the rational design of pillar-layered MOFs for methane purification.