Fabrication of polyimide and covalent organic frameworks mixed matrix membranes by in situ polymerization for preliminary exploration of CO2/CH4 separation

Abstract

More and more polyimide (PI) mixed matrix membranes (MMMs) have been reported for gas separation. In this study, a novel PI MMM, named as PI/SNW-1 and composed of PI and Schiff base network (SNW) type covalent organic frameworks (COFs) SNW-1, was used for gas permeation measurements of carbon dioxide (CO2) and methane (CH4). The prepared PI/SNW-1 was investigated by the Fourier transform infrared spectroscopy, the field emission scanning electron microscopy, and the thermal gravimetric analysis. The results indicated that PI/SNW-1 had maintained a high thermal stability and uniform distribution of filler. Compared with the pure PI membrane, MMMs showed an increment of 48.7% in ideal selectivity of CO2/CH4 and an enhancement of 106.4% in CO2 permeability at 5 wt% SNW-1. The enhancement of permeability and selectivity was mainly attributed to the high porosity of SNW-1, the specific sorption affinity for CO2, and the close interface interaction with the PI matrix. It can be seen that PI/SNW-1 has a great potential for actual gas separation.