Enhanced Gas Separation Performance of Rearrangeable Polyimide-Based Mixed Matrix Membranes via Incorporation of Iron Acetylacetonate

To improve the gas separation performance of polymeric membranes, mixed matrix membranes (MMMs) have been extensively developed. Herein, iron acetylacetonate (Fe(acac)3) was incorporated into rearrangeable polyimides (PIs) via in situ polymerization followed by thermal imidization. Owing to the formation of coordination bonds between Fe3+ and PI chains, the glass transition temperature of the MMMs was significantly increased. After thermal rearrangement (TR) treatment, their gas permeabilities were remarkably enhanced. Specifically, the TR-1.0%Fe(acac)3 sample exhibited exceptional gas permeabilities: 2417 Barrer for H2, 3027 Barrer for CO2, 427 Barrer for O2, 89 Barrer for N2, and 92 Barrer for CH4. Notably, its CO2/N2 and CO2/CH4 separation performances approached the 2019 upper bound. Furthermore, when the thermal treatment temperature was increased to 500 °C, the gas permeabilities were drastically enhanced to 15439 Barrer (H2), 29948 Barrer (CO2), 5488 Barrer (O2), 1152 Barrer (N2), and 1730 Barrer (CH4), with the CO2/CH4 separation performance surpassing the 2019 upper bound. After two years of ambient storage, the gas permeabilities of the MMMs significantly decreased but remained higher than those of the pristine TR membrane. This study proposes a facile strategy for improving gas separation performance by incorporating Fe(acac)3 into rearrangeable PIs, which offers promising potential for practical separation applications.