Enhancing polyimide-based mixed matrix membranes performance for CO₂ separation containing PAF-1 and p-DCX

Gradual permeability loss due to physical aging and the trade-off relationship between permeability and selectivity has largely hindered the advancement of membrane technology. In our prior works, porous aromatic framework (PAF-1) and poly-dichloroxylene (p-DCX) incorporated mixed matrix membranes (MMMs) have shown excellent anti-aging properties, achieved through polymer side chains adsorbing within PAF-1 or p-DCX pores. Advantageously, antiaging behaviour was usually also accompanied by enhanced membrane permeability due to the high porosity of the PAF-1 or p-DCX additive. However, these works mostly focused on polymers with moderate selectivities, such as polymers of intrinsic microporosity (PIM-1) and poly-trimethylsilyl-propyne (PTMSP). In this work, we investigated the anti-aging properties of PAF-1 and p-DCX in a highly selective polyimide (PI) polymer and demonstrated its potential for industrial CO₂ separation. As anticipated, PI membranes demonstrated a slower CO₂ aging rate with the addition of PAF-1 and p-DCX, for both single gases under low-pressure and mixed gas under high-pressure measurements. Additionally, the CO₂ permeability was significantly enhanced, and consequently the mixed-gas performance of the composite PI-based membranes surpassed 2008 Upper Bounds for both CO₂/N₂ and CO₂/CH₄ separation.