Enhanced Carbon Capture Via Mixed Matrix Membranes With Molybdenum Disulfide Nanosheet Fillers

Most the of commercial gas separation membrane systems used today are polymer-based due to the ease of processing,feasibility and low cost.Polymeric membranes designed for gas separations however,have been known to exhibit a trade-off between selectivity and permeability as illustrated by Robeson's upper bound plots.The development of membrane materials that can surpass Robeson's upper bound has been a crucial issue for research concerned with gas separation membranes the past decade.In an attempt to overcome this limitation,several researchers have explored the concept of mixed matrix membranes?MMMs?.These membranes combine a polymer matrix with inorganic materials such as zeolites or molecular sieves.A suitable filler material for MMMs should have excellent properties as a molecular sieve or gas adsorbent,good dispersion properties in a polymer matrix of submicron thickness,and should form high quality interfaces with the polymer material.Molybdenum disulfide?MoS₂?is a layered inorganic material,similar to graphene.MoS₂ has been used as an inorganic filler to fabricate MMMs for the separation of CO₂ from CH₄ and N₂.Pebax 1657,a CO₂-loving polymer was used to form the polymer matrix which was then loaded with exfoliated MoS₂ nanosheets.MMMs were formed via simple mixture casting and solvent evaporation.The selectivity of the Pebax-MoS₂ membrane surpassed that of the pure Pebax membrane but experienced losses in permeability.The selectivity for the CO₂/CH₄ and CO₂/N₂gas mixtures reached maximums of 33 and 28 respectively.The results for the CO₂/CH₄ gas mixture lies on Robeson's 1991 upper bound.The prepared MMMs were found to be defect free and stable over a range of feed pressures.The MMM operates mainly according to the solution diffusion mechanism.This is accompanied by the stronger adsorption energy of MoS₂ for CO₂than CH₄ and N₂ which leads to enhancements in gas selectivity.