Exploiting thermodynamic-kinetic synergetic effect for C3H6/C3H8 separation in pillar-layer MOFs

Efficient adsorption separation of propylene (C3H6) and propane (C3H8) can largely lower the energy consumption compared to the current energy-intensive cryogenic distillation. Herein, we report an isoreticular family of pillar-layer metal-organic frameworks (MOFs), M(AIP)(BPY)0.5 (M = Co, Ni, and Zn), for efficient C3H6/C3H8 separation by exploiting thermodynamic and kinetic effects, circumventing disadvantages of each separation mechanism. The three MOFs feature an open metal site for each metal node and uniform but narrow one-dimensional (1D) channels, offering strong binding sites toward C3H6 via π-complexations while obstructing the diffusion of bulkier C3H8. The Ni-MOF shows the best separation performance based on the highest thermodynamic and kinetic C3H6/C3H8 selectivity, further verified by computational simulations. Ni(AIP)(BPY)0.5 has a moderate C3H6 uptake of 1.94 mmol/g but a remarkably high C3H6/C3H8 uptake ratio of 4.26 at 298 K and 1 bar. Efficient C3H6/C3H8 separation, good recyclability, moisture and water stability of Ni(AIP)(BPY)0.5 are confirmed.