High-Performance UiO-66-NH₂/PI MMMs: Overcoming Interfacial Defects for High-Temperature Gas Separation Applications

The efficient separation of gases under high-temperature industrial conditions is crucial for addressing global energy and environmental challenges, particularly in processes such as CO₂ capture in natural gas processing, power plant flue gas treatment, and cement plant emissions. However, conventional membranes often suffer from interfacial defects, low gas selectivity, and poor thermal stability, which limit their practical applications. In this study, we aimed to develop high-performance mixed matrix membranes (MMMs) to improve CO₂/CH₄ separation performance. Amino-functionalized UiO-66-NH₂ was incorporated into a polyimide (PI) matrix using a simple, scalable fabrication process involving phase inversion and thermal imidization, which ensured uniform dispersion of UiO-66-NH₂ particles and facilitated large-scale production of dense, defect-free membranes. At an optimal UiO-66-NH₂ loading of 2 wt%, the MMMs achieved a CO₂ permeability of 451 Barrer and a CO₂/CH₄ selectivity of 6.62 at 25°C and 0.1 MPa, representing improvements of 23.91% and 114.94%, respectively, compared to pure PI membranes. The performance enhancement was attributed to the increased free volume within the membrane and the strong Lewis acid–base interactions between the amino groups of UiO-66-NH₂ and CO₂ molecules. Long-term stability testing at 300°C demonstrated excellent thermal stability, with consistent gas separation performance maintained over 160 h, confirming the membranes' suitability for high-temperature industrial applications. Furthermore, the UiO-66-NH₂/PI MMMs achieved an excellent balance between high permeability and selectivity, outperforming both organic and inorganic membranes, as well as certain traditional MOF-based MMMs. These findings offer a promising strategy for the development of robust and sustainable MMMs for high-temperature industrial gas separation processes.