Diffusion-Trap Mechanism-Mediated Trace Propylene Capture in a Microporous Metal-Organic Framework Enables Record Ethylene Purification From Cracking Gas.

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.