A zeolitic imidazolate framework with uncoordinated cyano groups in mixed matrix membranes for efficient propylene/propane separation
Guangli Yu, Ziyang Wang, Junchao Dong, Fei Ni, Dandan Song, Xiaoteng Liu, Zhanhui Yuan, Kangjun Wang, Xiaoqin Zou
Abstract
• A porous MOF of CN-ZIF-8 was synthesized with uncoordinated cyano groups. • Continuous mixed-matrix membranes of CN-ZIF-8/6FDA-DAM were successfully prepared for C 3 H 6 /C 3 H 8 separation. • The separation performances greatly surpassed the trade-off plot. • The synergy of thermodynamic and kinetic effects was clarified. Membrane technology is poised to substantially lower the energy consumption involved in the separation of C 3 H 6 from C 3 H 8 . However, the quest for suitable membrane materials for this critical process remains an ongoing challenge. Herein, a novel metal–organic framework (MOF) having cyano groups, thus referring to CN-ZIF-8, has been successfully identified and developed as productive nanofillers into 6FDA-DAM polymer. Unlike ZIF-8, CN-ZIF-8 exhibits a stronger affinity for C 3 H 6 and demonstrates favorable thermodynamic selectivity for recognizing it from C 3 H 8 due to the presence of dangling cyano groups, as confirmed by gas sorption. The optimal membrane with a 15 wt% CN-ZIF-8 loading evinces improved separation performance in terms of ≥80 % increase in ideal selectivity (∼23.6) and 144 % in C 3 H 6 permeability (∼379.8 Barrer) compared to the pristine 6FDA-DAM membrane. Mixed gas separation of a 50C 3 H 6 :50C 3 H 8 delivers remarkable separation results, out-performing the current trade-off limits associated with conventional polymer membranes. The synergistic effects of high gas solubility and the unique diffusivity behavior of CN-ZIF-8 effectively discriminate C 3 H 6 from C 3 H 8 . This study offers valuable insights into the exploration and the design of MOFs intended for the industrial C 3 H 6 /C 3 H 8 separation.