Highly permeable zeolitic imidazolate framework (ZIF)-71 nano-particles enhanced polyimide membranes for gas separation

Abstract Zeolitic imidazolate framework (ZIF)-71 nano-particles have been demonstrated as potential inorganic fillers for fabricating high-performance membranes for gas separation. The newly synthesized ZIF-71 nano-particles with a particle size of less than 100 nm were compatibly incorporated in 6FDA-Durene polyimide membranes as novel mixed matrix membranes (MMMs). No obvious agglomeration between ZIF-71 nano-particles and the 6FDA-Durene matrix was observed. The effect of ZIF-71 loading on gas separation performance was investigated for H 2 , O 2 , N 2 , CO 2 , CH 4 , C 2 H 4 , C 2 H 6 , C 3 H 6 and C 3 H 8 . The incorporation of ZIF-71 nano-particles improves both gas permeation properties and membrane resistance against plasticization. With a 20 wt% ZIF-71 addition, the pure CO 2 permeability of the MMM is increased by 3-fold, while the ideal CO 2 /CH 4 selectivity is reduced from 16.4 to 12.8. In addition, the CO 2 plasticization pressure is increased from 16 atm to 30 atm. The MMM embedded with 20 wt% ZIF-71 also displays a remarkable enhancement of C 3 H 6 permeability from 57.6 Barrer to 371 Barrer without significantly compromising the ideal C 3 H 6 /C 3 H 8 selectivity. The Positron Annihilation Lifetime Spectroscopy (PALS) and gas sorption characteristics further indicate that the permeability improvement is mainly due to the enhanced diffusivity and the molecular sieving effect of ZIF-71 nano-particles for separating C 3 H 6 /C 3 H 8 .