Insights into the thermodynamic-kinetic synergistic separation of propyne/propylene in anion pillared cage MOFs with entropy-enthalpy balanced adsorption sites.

Propyne/propylene (C 3 H 4 /C 3 H 6 ) separation is an important industrial process yet challenged by the trade-off of selectivity and capacity due to the molecular similarity. Herein, record C 3 H 4 /C 3 H 6 separation performance is achieved by fine tuning the pore structure in anion pillared MOFs. SIFSIX-Cu-TPA (ZNU-2-Si) displays a benchmark C 3 H 4 capacity (106/188 cm 3 g -1 at 0.01/1 bar and 298 K), excellent C 3 H 4 /C 3 H 6 IAST selectivity (14.6-19.3) and kinetic selectivity, and record high C 3 H 4 /C 3 H 6 (10/90) separation potential (36.2 mol kg -1 ). The practical C 3 H 4 /C 3 H 6 separation performance is fully demonstrated by breakthroughs under various conditions. 37.8 and 52.9 mol kg -1 of polymer grade C 3 H 6 can be produced from 10/90 and 1/99 C 3 H 4 /C 3 H 6 mixtures. 4.7 mol kg -1 of >99% purity C 3 H 4 can be recovered by a stepped desorption process. Based on the in situ single crystal analysis and DFT calculation, an unprecedented entropy-enthalpy balanced adsorption pathway is discovered. MD simulation further confirmed the thermodynamic-kinetic synergistic separation of C 3 H 4 /C 3 H 6 in ZNU-2-Si.