Membrane-based gas separation is a rapidly emerging technology that has been well established for the purification hydrogen streams, nitrogen production from air and is showing an increasingly larger roles in natural gas sweetening and vapor/gas separations. One actively pursued strategy to generate new polymeric membrane materials with combinations of high permeability and high selectivity is the introduction of a bimodal distribution of microporosity (pores < 20 Å) and ultramicroporosity (pores < 7 Å) in the polymer matrix. It has been shown that rigid ladder-type chains comprising fused rings joined by sites of contortion pack inefficiently in the solid state to produce polymers of intrinsic microporosity (PIMs). Furthermore, the successful integration of monomers contorted by spirobisindane, ethanoanthracene, Tröger’s base and triptycene moieties into polyimide structures has generated highly permeable intrinsically microporous polyimides (PIM-PIs). Some of these PIMs and PIM-PIs exhibited significantly enhanced performance for O2/N2, H2/N2, H2/CH4 and CO2/CH4 separations with properties located on the most recent permeability/selectivity upper bounds.1,2 Several series of PIM-PIs will be presented based on rigid and bicyclic moieties, which are solution processable to form mechanically robust films with high internal surface areas (up to 1000 m2 g-1). Gas permeation and physisorption data indicate the development of ultramicroporous structures that are tunable for different gas separation applications. Specific emphasis will be placed on the potential use of hydroxyl- and carboxyl-functionalized PIM-PIs for energy demanding applications for natural gas treatment and olefin/paraffin separation. PIM-PIs with highly polar functional groups define the recently proposed 2018 mixed-gas polymer upper bound for CO2/CH4 separation.3 The potential use of PIM-PIs as matrix materials for hybrid polymer/MOF and microporous carbons will be demonstrated. References 1. Swaidan, R., Ghanem, B., Pinnau, I., ACS Macro Lett. 2: 947-951, 2015. 2. Comesaña-Gándara, B., Chen, J., Grazia Bezzu, C., Carta, M., Rose, I., Ferrari, M.-C., Esposito, E., Fuoco, A., Jansen, J.C., McKeown, N.B., Energy. Environ. Sci. 12: 2733-2740, 2019. 3. Wang, Y., Ma, X., Ghanem, B.S., Alghunaimi, F., Pinnau, I., Han, Y., Mater. Today Nano 3: 69-95, 2018.