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.