Diffusion-Trap Mechanism-Mediated Trace Propylene Capture in a Microporous Metal-Organic Framework Enables Record...

Efficient separation of a propylene (C₃H₆) and ethylene (C₂H₄) mixture is very essential in the petrochemical industry but remains a major challenge due to their similar physicochemical properties. Herein, we report a diffusion-trap mechanism in a metal-organic framework (Cu-TBDA) with one-dimensional channels and functionalized side nanocages for excellent C₃H₆/C₂H₄ separation. The suitable channels and confined cavities in Cu-TBDA simultaneously boost the mass transfer efficiency and provide strong binding sites for C₃H₆ molecule. Thus, at 298 K, Cu-TBDA achieves ultrahigh C₃H₆ uptake of 2.06 mmol g^-1 at 0.01 bar, and record Henry selectivity of 44.0 and ideal adsorption solution theory (IAST) selectivity of 39.8 for C₃H₆/C₂H₄ mixtures. The kinetic experiments proved Cu-TBDA possesses fast C₃H₆ adsorption kinetics (0.66 min^-1) and high kinetic C₃H₆/C₂H₄ selectivity (4.57). Dynamic breakthrough tests confirm Cu-TBDA can gather high-pure C₂H₄ (> 99.95%) from C₃H₆/C₂H₄ mixtures with benchmark C₂H₄ productivities and C₃H₆/C₂H₄ separation factors, along with efficient C₃H₆ (> 99.90%) recovery during desorption. Additionally, Cu-TBDA has good structure stabilities and can be synthesized through the simple reflux technique, which renders it a promising adsorbent for practical C₃H₆/C₂H₄ separation. This work sets a new benchmark for achieving precise and efficient gas separation in industrial applications.