Efficient CO₂/CH₄ Separation Using Polysulfone/NH₂-MIL-125(Ti) Mixed Matrix Membranes

Abstract

This study investigates the fabrication and optimization of mixed matrix membranes (MMMs) composed of NH₂-MIL-125(Ti), a metal-organic framework (MOF), dispersed within a polysulfone (PSf) polymer matrix, for efficient CO₂/CH₄ separation. The MMMs were prepared by using a solution casting method, and their morphology and gas separation performance were systematically characterized. The effect of MOF addition into the polymer matrix, gas permeability, and selectivity were evaluated using a gas permeation setup. Results indicate that incorporating NH₂-MIL-125(Ti) nanoparticles enhances the selectivity of the membranes for CO₂ over CH₄ compared to pure polymer membranes while maintaining acceptable permeability. The membrane morphology demonstrates the uniform distribution of the filler in the polymer matrix. The PSf/NH₂-MIL-125(Ti)-15% membrane showed exceptional CO₂ permeability and selectivity performance. Specifically, it achieved a CO₂ permeability of 19.17 Barrer. Additionally, it exhibited a CO₂/CH₄ selectivity of 31.95, indicating its ability to effectively differentiate between the CO₂ and CH₄ gases, which is critical for applications such as natural gas purification and carbon capture. Furthermore, the MMMs produced in this study showed outstanding resistance to CO₂ plasticization. The PSf/NH₂-MIL-125(Ti)-15% membrane demonstrated superior pressure resistance, withstanding up to 14 bar without significant performance degradation compared to the pristine PSf membrane, which succumbed to plasticization at 4 bar. The enhanced plasticization resistance is attributed to incorporation of NH₂-MIL-125(Ti) into the PSf matrix. The combination of high CO₂ permeability, excellent selectivity, and robust plasticization resistance positions the PSf/NH₂-MIL-125(Ti)-15% membrane as a highly effective solution for CO₂ separation applications. The results underscore the potential of these MMMs to achieve significantly better performance metrics than traditional PSf membranes, making them a promising option for industrial gas separation processes.