Enhanced CO2 selectivity of mixed matrix membranes with carbonized Zn/Co zeolitic imidazolate frameworks

Abstract

In order to efficiently separate CO2, Zn/Co zeolitic imidazolate framework (Zn/Co-ZIF) nanoparticles were carbonized and then loaded in situ into PEBAX polymer to enhance CO2 permeability and selectivity of mixed matrix membranes (MMMs), simultaneously. Positron annihilation lifetime spectroscopy (PALS), gas adsorption apparatus, and FTIR were used to characterize Zn/Co-ZIF carbonized at 600 °C for various hours and MMMs. It was found that carbonized Zn/Co-ZIF obtained local defective structures with abundant carbon and nitrogen active sites, CO2 adsorption capacity of Zn/Co-ZIF carbonized at 600 °C for 24 h increased by 1.87 times to 2.64 mmol/g. With the increasing of carbonization time, CO2 permeability of MMMs firstly decreased and then increased, while selectivity showed the opposite tendency. CO2 permeability of PEBAX-8H membrane loaded with Zn/Co-ZIF carbonized at 600 °C for 8 h increased by 15% to 102.5 ± 3.0 barrers, and selectivity of CO2/N2, CO2/CH4 and CO2/H2 increased by 45%, 43% and 18% to 52.1, 16.4 and 9.4, respectively.