Recognition of C Olefins by an Ultramicroporous ftw-Type Yttrium-Based Metal-Organic Framework with Distorted Cages.

Developing porous adsorbents for efficient separation of C olefins is significant but challenging in the petrochemical industry due to their similar molecular sizes and physical properties. The separation efficiency is often limited when separating C olefins by a single separation mechanism. Herein, an ultramicroporous yttrium-based MOF, Y-dbai, is reported featuring cage-like pores connected by small windows, for recognition and efficient separation of C olefins through a synergistic effect of thermodynamic and kinetic mechanisms. At 298 K and 1 bar, the adsorption capacities of Y-dbai for CH, 1-CH, and i-CH are 2.88, 1.07, and 0.14 mmol g, respectively, indicating a molecular sieving effect toward i-CH. The CH/i-CH and 1-CH/i-CH uptake selectivities of Y-dbai are 20.6 and 7.6, respectively, outperforming most of the reported adsorbents. The static and kinetic adsorption experiments coupled with DFT calculations indicate the separation should be attributed to a combined effect of thermodynamically and kinetically controlled mechanism. Breakthrough experiments have confirmed the excellent separation capability of Y-dbai toward CH/1-CH, CH/i-CH and CH/1-CH/i-CH mixtures.