A robust heterometallic ultramicroporous MOF with ultrahigh selectivity for propyne/propylene separation

Highly efficient removal of trace propyne (C₃H₄) (propyne <1000 ppm) from propylene (C₃H₆) is an essential and challenging industrial process due to the high molecular similarity of C₃H₄ and C₃H₆. Herein, we created a new ultramicroporous metal–organic framework (NKMOF-11) with exceptional water stability, superior C₃H₄ binding affinity, and ultrahigh uptake capacity of C₃H₄ at ultra-low pressure (0.1 mbar). Modelling studies revealed that the excellent performance of NKMOF-11 can be attributed to the suitable pore aperture and unique binding sites for C₃H₄ through strong hydrogen bonding and π–π interactions. Attributed to the preferred adsorption of C₃H₄, NKMOF-11 possessed ultrahigh selectivities towards C₃H₄/C₃H₆ mixtures (1/99 and 1/999 (v/v)) at room temperature. The simulation and experimental breakthrough results further revealed that NKMOF-11 possesses excellent separation performance towards C₃H₄ and C₃H₆ binary mixtures (1/99 and 1/999) and sets a new record for the productivity of polymer-grade C₃H₆ (>99.996%) among all reported materials. This study paves a new avenue for the design of adsorbent materials with both high selectivity and high productivity for a C₃H₄/C₃H₆ binary mixture.