Supramolecular framework crystallinity engineering via surface-confined polymerization for enhanced C3H6/C2H4 separation

Abstract

Crystalline supramolecular frameworks (SMFs) with high porosity are advantageous for propylene (C3H6) uptake and thus methanol to olefin (MTO) product separation. However, SMFs tend to transform into amorphous states and lose porosity upon activation, which limits the exploration of their performance. Herein, we for the first time report a new SMF, NUT-161 of high porosity, constructed from tri-nuclear zirconium clusters and 4,4'-(ethyne-1,2-diyl)dibenzoic acid (H2-EDBA), and reinforced its stability through a surface-confined polymerization of isophorone diisocyanate (IDI) onto its crystal surface. The obtained NUT-161@PolyIDI maintained a significantly improved crystallinity, showing a 324 % increment in specific surface area (2213 vs. 522 m2·g-1) compared to the activated pristine NUT-161. More importantly, the retention of high porosity enables NUT-161@PolyIDI to achieve better C3H6 adsorption performance with an increment of 249 % at 273 K, and its separation potential has been conspicuously improved. Besides, the dynamic breakthrough studies demonstrate that NUT-161@PolyIDI exhibits well-maintained separation capacity over three cycles. Grand Canonical Monte Carlo simulation was used to illustrate the separation mechanism of NUT-161@PolyIDI, and the results suggest the framework exhibits multiple C-H···π interactions with C3H6, preferentially binding to C3H6 over ethylene (C2H4). This strategy may provide a solution to improve the crystallinity of porous materials for applications in various scenarios.