One-pot in situ synthesis of ZIF particles to prepare thin-film nanocomposite membranes for CO2 separation

Abstract

Mixed matrix membranes (MMMs) are more likely to break the Robeson upper bound because they combine the pros of both organic and inorganic membranes. However, in the conventional MMMs preparation processes, multi-steps are normally needed and, in many cases, the particle agglomeration and consequent non-selective voids are unavoidable, resulting in poor CO2 separation performances. In addition, the agglomeration makes it challenging to fabricate thin-film nanocomposite (TFN) membranes. In this study, zeolitic imidazolate framework (ZIF)-8- and ZIF-67-based TFN membranes were fabricated via a facile one-pot in situ synthesis protocol. The ZIF particles were synthesized in the polymeric solution, then the TFN membranes were fabricated by a dip coating method. With a casting solution concentration of 1.5 wt.%, a selective layer with a thickness of ∼300 nm can be prepared on the porous polyacrylonitrile (PAN) support. The results of thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), Fourier Transform Infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) showed that ZIFs were successfully synthesized in the casting solution. At 35 °C and 2 bar, the membrane containing 5 wt.% ZIF-67 had CO2 permeance of 223.35 gas permeation unit (GPU), which was 16.55% higher than that of pure Pebax.