Bimodal-porous hollow MgO sphere embedded mixed matrix membranes for CO₂ capture

We reported the use of high-performance, CO₂-accelerated mixed matrix membranes (MMMs) consisting of sub-micron porous magnesium oxide (MgO) fillers and an amphiphilic polymer matrix. Bimodal-porous, hollow MgO (bh-MgO) spheres were synthesized through a one-step spray pyrolysis and precipitation method. The synthesized bh-MgO spheres were introduced into poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM), forming MMMs for CO₂/N₂ separation. The amphiphilic property of PVC-g-POEM ensured an intimate contact between the bh-MgO filler and polymer matrix with the encapsulation of bh-MgO spheres. The bimodal porous and hollow structure of bh-MgO decreased the gas diffusion resistance in the membranes. Moreover, specific interactions between the surfaces of the bh-MgO and CO₂ molecules enhanced the CO₂ solubility and accelerate the CO₂ molecules more than the N₂ molecules. The dual-functional bh-MgO sphere enhanced the CO₂ permeability through physical and chemical mechanisms, simultaneously. The best gas separation performance was obtained in the MMM with 10 wt% bh-MgO fillers, which demonstrated a CO₂ permeability of 179.2 Barrer and 42.6 of CO₂/N₂ selectivity.