(681e) Leveraging Free Volume Manipulation to Improve Membrane Separation Performance of Amine-Functionalized PIM-1

Diffusion-selective microporous polymers have gained increased attention as energy-efficient alternatives for membrane-based gas separations. The archetypal polymer of intrinsic microporosity, PIM-1 has stood out due to its excellent performance and facile post-synthetic modification through functionalization and cross-linking. Here, we take advantage of this post-synthetic versatility to tune the performance of amine-functionalized PIM-1 (PIM-NH2). In previous work, PIM-NH2 displayed high CO2 sorption compared to PIM-1, resulting in reduced CO2-based diffusion selectivity. At the same time, PIM¬-NH¬¬2 had moderately improved H2-based separation performance through hydrogen-bonded mediated size-sieving. We have developed a post-synthetic method to address sorption and diffusion mediated effects in PIM-NH2 and achieve optimal CO2- and H2-based separation performance. Using protection and de-protection of the amine group through thermal and solution-based methods, we tuned the porosity and sorption capacity of the films. Protection and de-protection of a bulky group enabled discrete tuning of the film’s porosity to achieve size-sieving through narrowing of the pore size distribution or increased permeation through enlarged pores. Through de-protection, we also introduced cross-links which reduced CO¬2 sorption and enhanced CO2 diffusion. The thermally processed sample displayed significant enhancements in CO2-based selectivity and H2-based selectivity, ultimately crossing the 2008 Robeson upper-bound for H¬2-based pairs.