Water-based, non-toxic, eco-friendly polymerization is carried out to synthesize a zwitterionic comb copolymer, i.e., poly(oxyethylene methacrylate)-co-sulfobetaine methacrylate (POEM-PSBMA). POEM-PSBMA undergoes a specific interaction with ferric (Fe3+) ions to form a three-dimensional, interconnected transporting channel for CO2. Without any post-treatment, the as-synthesized POEM-PSBMA solution complexed with ferric ions is directly coated onto a microporous polysulfone support to form thin-film composite membranes. The chain morphology and structure are determined by employing Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), small angle X-ray scattering (SAXS), and energy-filtered transmission electron microscopy (EF-TEM). Microphase-separated structures are observed for all membranes, and the structures become smaller with increasing ferric ion loadings. This results from the selective interaction between ferric ions and POEM chains in the copolymer, leading to an increased number of CO2-philic sites. The coordination of the ferric ions reduces the free volume in the polymer matrix and hinders the diffusion of non-polar gases such as CH4 and N2. As a result, the CO2/N2 ideal selectivity and CO2/CH4 mixture selectivity are dramatically enhanced from 4.01 and 8.26 to 423 and 695, respectively, which represent the highest performances reported so far, to our knowledge.
Bibliographical noteFunding Information:
This work was supported by a National Research Foundation (NRF) of South Korea grant funded by the Ministry of Science, ICT and Future Planning (NRF-2017R1A4A1014569, NRF-2018M3A7B4071535, and NRF-2017R1D1A1B06028030).
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)