Optimizing SSMMP-Based Fillers with -NH₂ Functionalization and PIM‑1 Coating for High-Performance CO₂/CH₄ and CO₂/N₂...

Gas separation employing polymeric membranes is limited by the permeability-selectivity trade-off, which has driven the development, among numerous technologies, of mixed matrix membranes (MMMs) that combine highly permeable polymers with fillers capable of enhancing gas selectivity. The compatibility in the filler/polymer interface is therefore essential to design materials with superior separation performances. In this work, MMMs were produced with Pebax-2533, incorporating synthetic silico-metallic mineral particles (SSMMPs) and SSMMP-NH₂ fillers, both with and without PIM-1 surface coating, and were evaluated in the separation of CO₂/CH₄ and CO₂/N₂. The membranes were prepared in two types: dense and thin-film composite (TFC). These MMMs were characterized through several techniques, and gas permeation assessments of the dense membranes were conducted at pressures ranging from 1 to 10 bar. The findings demonstrated enhanced thermal, mechanical, and gas separation properties following the addition of the fillers. Specifically, the sample containing 20 wt % SSMMP-NH₂@PIM-1 achieved a permeability of 501.7 Barrer at 10 bar, representing a 129.8% increase relative to the pure membrane. Additionally, the TFC membrane was fabricated using a self-made porous polysulfone (PSF) support, which was subsequently coated with a selective layer and a protective layer of polydimethylsiloxane (PDMS), achieving a CO₂ permeance of 575 GPU and selectivities of 12 for CO₂/CH₄ and 33 for CO₂/N₂. The results demonstrated the beneficial effects of functionalizing the amine groups (-NH₂) in the fillers, particularly when employing the nonsolvent-induced surface deposition (NISD) technique to coat PIM-1 on the filler surface. The developed materials exhibit promising performance as visualized in the Robeson graph and TFCs target regions, suggesting that they could be suitable for industrial-scale CO₂ separation with additional development.