Molecular-Sieving Energy-Efficient Gas Separation Membranes Enabled by Multi-covalent-crosslinking of Microporous Polymer Blends

Abstract

\n Highly permeable and selective membranes that exceed the conventional permeability-selectivity upper bound are attractive for energy-efficient gas separations. In the context microporous polymers have gained increasing attention owing to their high porosity and exceptional permeability. However, the moderate selectivity of microporous polymers caused by inherent broad distribution of cavities leads to a loss of valuable gas products, making them unfavorable for separating similarly sized gas mixtures. Here we report a new approach to designing polymeric molecular sieve membranes via multi-covalent-crosslinking of miscible blends of Polymer of Intrinsic Microporosity, i.e. bromomethyl (PIM-BM) and Tröger s Base (TB), enabling simultaneously high permeability and selectivity. Selective gas permeation is achieved via adjusting reaction temperature, reaction time and the oxygen concentration with occurrences of polymer chain scissor, rearrangement and thermal oxidative crosslinking reaction simultaneously. Upon a thermal treatment at 300 oC for 5h, membranes exhibit an O2/N2, CO2/CH4 and H2/CH4 selectivity as high as 11.1, 155.7 and 814.1, respectively, with an O2, H2 and CO2 permeability of 18.2, 358.2 and 67.6 Barrer, respectively, transcending the state-of-art upper bounds. The design strategy represents a generalizable approach to creating molecular-sieving polymer membranes with enormous potentials for energy-efficient separation processes.