Guest-dependent pressure induced gate-opening effect enables effective separation of propene and propane in a flexible MOF

Propene (C3H6)/propane (C3H8) separation is an important but challenging industrial task. Adsorptive separation using porous materials tends to be an energy- and cost-effective strategy. In this work, a flexible porous MOF named NJU-Bai8 is demonstrated to be a promising adsorbent for the effective separation of C3H6 and C3H8 in a wide temperature range from 298 to 348 K due to its flexible microporous structure, which provides unique guest responsive molecule accommodation. Adsorption isotherms, ideal adsorbed solution theory (IAST) prediction of separation ability, and transient breakthrough on both simulation and experiment were performed to evaluate its separation selectivity and cycling experiments were carried out to explore its structural stability. It was found that the C3H6/C3H8 uptake ratio and IAST selectivity of NJU-Bai8 is 43.2 and 4.6 at 298 K and 20 kPa, respectively. The breakthrough time interval for C3H6 and C3H8 is over 10 min for a C3H6/C3H8/He (20%/20%/60%) mixture under ambient conditions, and this separation ability can maintain more than 10 cycles. Detailed analysis reveals that a guest-dependent pressure induced gate-opening effect in the flexible framework of this MOF is indeed responsible for the observed unique selective adsorption and separation performances. This material also shows good regenerability, being favorable for possible industrial application.