Gravity-Induced Approach to Mixed Matrix Membrane with Asymmetric Structure for Ultrahigh CO₂ Separation: Influence of Particle Deposition

Mixed matrix membranes (MMMs) have been widely studied as the most promising gas separation membrane materials. However, the heterogeneous distribution of fillers within the membrane has not been fully explored. Herein, a series of asymmetric MMMs with selective, intermediate, and diffusion layers were constructed from top to bottom by gravity-induced deposition behavior of the fillers. MMMs exhibit extremely high CO2 separation performance for a particular asymmetric structure, changing the uniform permeability behavior of the gas. This also realizes the synergistic improvement of CO2 permeability and selectivity. In particular, the CO2 permeability of the UiO-H2O-27/Pebax-60 wt % MMM was up to 909.14 Barrer, which is 4.1 times higher than that of the homogeneous membrane (PCO2 = 223.64 Barrer). Compared to the pure Pebax membrane, the CO2 permeability of the optimized membrane increased 8.2 times (from 110.87 to 909.14 Barrer), and the CO2/N2 selectivity increased from 42.6 to 68, successfully surpassing the upper bound of 2019.