A Microporous Poly(arylene ether) Platform for Membrane-Based Gas Separation

Abstract

Membrane-based gas separations are viewed as a critical component to accessing low-energy feedstocks and decarbonizing the chemical industry. However, it is exceedingly challenging to synthesize membrane materials that are high-performing, scalable, and processable. As a class of materials, microporous organic polymers (MOPs), which combine the gas sieving ability of microporous materials with the solution-processability of organic polymers, are highly desirable. Herein, we report the rational design and synthesis of linear microporous poly(arylene ether)s (PAEs) via Pd-catalyzed C-O polycondensation reaction. The scaffold of these microporous polymers consists of rigid three-dimensional triptycene and highly stereocontorted spirobifluorene, which endow these polymers with large internal free volume as well as high porosity with angstrom-sized pores. Unlike classic polymers of intrinsic microporosity (PIMs), this robust methodology for the synthesis of poly(arylene ether)s allows for the facile incorporation of functionalities and branched linkers for control of permeation and mechanical properties. CO2-philic groups, such as nitrile and tertiary amine groups, can be incorporated into this microporous polymeric scaffold for enhancing CO2 separation performance. In addition, a solution-processable branched polymer prepared using this synthetic strategy showed good gas separation performance and enhanced mechanical properties, which allowed for the formation of a submicron defect-free film with permeance-selectivity property sets that are comparable to high-performance ultrathin polymer membranes that have been optimized at industrial scale. In contrast with commercially available polymer membranes, the easily accessible PAE branching motif endows these materials with plasticization resistance. The structural tunability, high physical stability, and ease of processing suggest that this new platform of microporous polymers provides generalizable design strategies to address outstanding separation challenges for gas separation membranes.