Gravity-Induced Approach to Mixed Matrix Membrane\nwith Asymmetric Structure for Ultrahigh CO<sub>2</sub> Separation:\nInfluence of Particle Deposition

Mixed matrix membranes (MMMs) have\nbeen widely studied as the most\npromising gas separation membrane materials. However, the heterogeneous\ndistribution of fillers within the membrane has not been fully explored.\nHerein, a series of asymmetric MMMs with selective, intermediate,\nand diffusion layers were constructed from top to bottom by gravity-induced\ndeposition behavior of the fillers. MMMs exhibit extremely high CO<sub>2</sub> separation performance for a particular asymmetric structure,\nchanging the uniform permeability behavior of the gas. This also realizes\nthe synergistic improvement of CO<sub>2</sub> permeability and selectivity.\nIn particular, the CO<sub>2</sub> permeability of the UiO-H<sub>2</sub>O-27/Pebax-60 wt % MMM was up to 909.14 Barrer, which is 4.1 times\nhigher than that of the homogeneous membrane (<i>P</i><sub>CO<sub>2</sub></sub> = 223.64 Barrer). Compared to the pure Pebax\nmembrane, the CO<sub>2</sub> permeability of the optimized membrane\nincreased 8.2 times (from 110.87 to 909.14 Barrer), and the CO<sub>2</sub>/N<sub>2</sub> selectivity increased from 42.6 to 68, successfully\nsurpassing the upper bound of 2019.