Recognition of C4 Olefins by an Ultramicroporous ftw-Type Yttrium-Based Metal-Organic Framework with Distorted Cages.

Abstract

Developing porous adsorbents for efficient separation of C4 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 C4 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 C4 olefins through a synergistic effect of thermodynamic and kinetic mechanisms. At 298K and 1bar, the adsorption capacities of Y-dbai for C4H6, 1-C4H8, and i-C4H8 are 2.88, 1.07, and 0.14mmolg-1, respectively, indicating a molecular sieving effect toward i-C4H8. The C4H6/i-C4H8 and 1-C4H8/i-C4H8 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 C4H6/1-C4H8, C4H6/i-C4H8, and C4H6/1-C4H8/i-C4H8 mixtures.