Simple Strategy for the Fabrication of Thin Amine-Polysiloxane Hybrid Membranes Supported by Microfiltration Membranes

Membranes have been developed for effective CO2 separation from flue gas and are typically designed for room-temperature operation. However, some flue gases are emitted at moderate-to-high temperatures (100–200 °C). For such conditions, amine-functionalized polysiloxane membranes are suitable due to their thermal stability and CO2-philic properties. Traditionally, these membranes use a multilayer structure─an amine-polysiloxane layer over an intermediate layer on porous α-alumina supports─to prevent polysiloxane polymer penetration and achieve uniform layers, but this requires complex fabrication involving multiple coatings and heat treatments. In this study, we propose a simplified strategy of directly coating a sticky polysiloxane-amine polymer hybrid onto microfiltration membranes, including α-alumina tubes and flexible carbon hollow fibers. The membranes exhibited significant CO2/N2 permeance ratios exceeding Knudsen selectivity, achieving a CO2 permeance of 10–8 mol/(m2 s Pa) and a CO2/N2 ratio of ∼5 at 150 °C. This strategy presents a practical approach for high-temperature CO2 separation applicable to various supports.