Metal-Coordinated, Dual-Crosslinked PIM Polymer Membranes for Upgraded CO Separation: Aging and Plasticization Resistance.

The practical use of polymers of intrinsic microporosity (PIMs) in CO separation is often hindered by their moderate selectivity, performance instability over time, and pressure constraints. To address these limitations, a straightforward approach is presented to enhance the CO separation capability of PIM-1 by incorporating metal ions into uniformly hydrolyzed PIM-1 (cPIM). This dual linking strategy, achieved via ionic and coordination bonding of metal ions with the polymeric side chains including ─COOH and ─CONH, restructures the polymer, disrupting hydrogen bonds between cPIM chains and creating active sites for CO via π-complexation. This modification enhances gas permeability while maintaining high selectivity. The optimized zinc-coordinated membrane achieves an impressive CO permeability of ≈2,500 Barrer with CO/N and CO/CH selectivities of 27.1 and 23, respectively, outperforming pristine cPIM (700 Barrer; CO/N = 27; CO/CH = 19). Notably, this performance surpasses the 2008 Robeson upper-bound limits for both gas pairs. Additionally, the metal-coordinated membranes exhibit remarkable long-term stability, resisting aging effects for up to 20 days and maintaining anti-plasticization properties at pressures up to 20 bar. These dual-crosslinked membranes demonstrate promising potential for mixed gas separation, indicating their suitability for real-world industrial applications.