Highly Selective Ethylene/Ethane Separation in MOF Composites through Pore Contraction and Particle Size Enlargement Strategy

The discrimination of ethylene (C₂H₄) and ethane (C₂H₆) by the precise regulation of porous materials is important and challenging. In this work, the quasi-exclusion of C₂H₆ from C₂H₄ is realized through a facile polymer modification and shaping method of metal-organic framework ZnAtzPO₄ (Atz = 3-amino-1,2,4-triazole). The polymer (carboxymethyl cellulose, CMC) modification and shaping of ZnAtzPO₄@CMC result in pore contraction and particle size enlargement, which impedes the diffusion of larger C₂H₆ molecules and improves the kinetic separation of C₂H₄/C₂H₆. The C₂H₆ capacity decreases steeply from 1.63 (ZnAtzPO₄ powder) to 0.27 mmol g^-1 (ZnAtzPO₄@CMC), and the resulting C₂H₄/C₂H₆ uptake ratio increases from 1.38 to 6.67. Kinetic adsorption experiments confirm that ZnAtzPO₄@CMC presents a negligible C₂H₆ dynamic capacity and the diffusion difference between C₂H₄ and C₂H₆ is amplified significantly. The corresponding kinetic C₂H₄/C₂H₆ separation selectivity of ZnAtzPO₄@CMC increases from 13.06 (ZnAtzPO₄) to 34.67, superior to the most reported benchmark materials. Furthermore, ZnAtzPO₄@CMC exhibits excellent breakthrough performance for equimolar C₂H₄/C₂H₆ mixture separation. This study provides guidance to discriminate similar gases through polymer modification of MOFs.