Mixed matrix membranes with intrinsic microporous/UiO-66 post-synthesis modifications with no defects for efficient CO2/N2 separation

Abstract

Mixed matrix membranes (MMMs) based on metal–organic frameworks (MOFs) are expected to realize efficient separation of CO2. However, interfacial compatibility issues between MOFs and polymer matrices limit their performance. In this work, a post-synthesis modification (PSM) strategy was adopted to convert UiO-66 into porous liquids (PLs). MMMs were prepared by incorporating PLs into PIM-1 matrix. The PLs have a liquid-like behavior and can be evenly scattered in PIM-1 matrix to form an interface without defect. The SEM morphology analysis further certified that MMMs had no interface defect and PLs had brilliant compatibility with the polymer film. In addition, the CO2-philic ether bonds of the EO fragments enable the MMMs to have superior CO2 selective separation. Compared with pure PIM-1, the highest CO2 permeability was improved by 158.0 % and 62.5 % was the increase in CO2/N2 selectivity, arriving at 7211.7 Barrer and 26.0, respectively. Meanwhile, the overall separation performance of MMMs for CO2/N2 exceeds the 2008 Robson upper limit, showing outstanding gas separation performance.