Polymer membrane with enhanced organic solvent resistance enabled by a metal-organic framework cross-linker

Organic solvent nanofiltration (OSN) membranes with ideal flux and rejection rates, as well as a wide range of solvent resistance and good stability are highly required in daily chemical production. Chemical cross-linking strategies can improve the stability of polymer membranes for stable separation properties in a wide range of organic solvents, and they also play a crucial role in the aging and compaction resistance of membranes. However, the chemical cross-linker occupies free volume in the molecular chain, resulting a decrease in permeance. And they also break down the structure of the polymer backbone, affecting the membrane’s mechanical properties. This work proposes a metal organic framework (ZIF-8) based cross-linker to enhance the organic resistance of polymer membrane with largely improved permeance. Typically, nano-sized ZIF-8 particle were dispersed into a carboxyl-functionalized polyimide (C-PI). The obtained polymer membrane was in situ crosslinked by forming coordination bond between –COOH group of C-PI and Zn 2+ on the surface of ZIF-8. ZIF-8 crosslinked polymer membrane remained stable in a wide range of organic solvents including acetone, methanol, acetonitrile, dimethylformamide, etc. The methanol permeance of the crosslinked membrane is largely enhanced by 428 %. The optimized ZIF-8 crosslinked membrane showed a methanol permeance of 20.8 L m -2  h −1  bar −1 and a rejection rate of 91.3 % for Congo Red. The present study confirms the feasibility and advantage of framework-based material as a cross-linker to obtain OSN membranes with robust chemical stability and excellent separation performance.