Small changes, big impacts: Ultra-fine tuning of ultra-microporous MOFs with remarkable C ₂H ₂ selectivity

The efficient separation of acetylene gas (C₂H₂) from C₂H₂/C₂H₄ and C₂H₂/CH₄ is of great significance in various applications due to its high commercial value and numerous practical production scenarios. In this study, a series of ultra-microporous metal‒organic frameworks (MOFs) (<strong>JLU-MOF161-164</strong>) were prepared using mixed-ligand strategy. Drawing upon the principles of isoreticular chemistry, the precise control over ultra-microporous MOFs at a sub-1 Å scale was achieved through functionalization of ligands. The pore sizes decreased from 5.70 to 4.90, 4.24, and 3.74 Å for <strong>JLU-MOF161-164</strong>. This ultra-fine tuning in pore size significantly improved the selectivity towards C₂H₂ for the series compounds. The C₂H₂ adsorption capacity of <strong>JLU-MOF164</strong> reached 76.1 cm³ g⁻¹ at 298K. Notably, the selectivities for C₂H₂/C₂H₄ (50/50) and C₂H₂/CH₄ (50/50) achieved remarkable values of 10.1 and 716.7, respectively. Compared with <strong>JLU-MOF161</strong>, these selectivities were enhanced by 3.6-fold and 9.9-fold, respectively. Breakthrough experiments further validated the outstanding dynamic separation performance and excellent cycling stability of <strong>JLU-MOF164</strong>, highlighting its significant potential for industrial application.