Low-crystallinity ZIF-8/dcIm membranes for CO2 sieving

Metal-organic framework membranes have shown great potential for efficient separation applications. However, unavoidable grain boundary defects and the inconstant pore size due to framework flexibility hinder the application of MOF membranes for gas separation. Herein, low-crystallinity ZIF-8/dcIm-x membranes are synthesized via fast current-driven synthesis. The competitive coordination of 4,5-dichloroimidazole (dcIm) linker leads to the formation of a low-crystallinity MOF with reduced grain boundary defects for better gas separation performance. Meanwhile, the in-situ substitution of the mIm linker by dcIm narrows the pore size and transforms the ZIF-8 structure in the stiffened Cm polymorph, allowing precise CO 2 sieving. Consequently, the low-crystallinity ZIF-8/dcIm-14 membrane exhibits a promising CO 2 /CH 4 selectivity of 32.4 with a CO 2 permeance of 1.73 × 10 −8  mol m −2  s −1 Pa −1 , which surpasses other membranes. Furthermore, the membrane presents a remarkable pressure resistance up to 3 bar and stable temperature-swing operation between room temperature and 125 °C over 120 h.