This dissertation discusses the development of microporous polymers with heterocyclic ring structures using iptycene motif for high-performance gas separation membranes. A large body of polymers containing rigid heterocyclic ring structures have demonstrated promising gas separation performances, attributed to high fractional free volume owing to disrupted chain packing. However, due to lack of control over the free volume architecture, these microporous polymers are still subject to the commonly observed permeability-selectivity tradeoff, where the ultrahigh permeability achieved with high fractional free volume is accompanied with much less attractive selectivity. Moreover, the solutions to physical aging (loss of permeability over time) and plasticization (loss of size sieving upon sorption of condensable gases like CO2) remain uncovered. Recently, macromolecular design strategies through the use of hierarchical triptycene moieties have emerged, which generated various microporous polymers with high gas separation performances that redefined the upper bound limits along with good resistance to physical aging and plasticization. Triptycene represents the simplest structure of iptycenes that has three-dimensional pedal wheel-like structure composed of fused rings. The bulky and rigid triptycene building blocks can efficiently disrupt chain packing to create low-barrier diffusion pathways for fast gas transport, while the intrinsic molecular free volume between the arene blades provides ultrafine free volume microcavity to simultaneously enhance size sieving.With the promise of utilizing triptycene moieties to create desirable free volume architecture, opportunities for further performance advancement exist for pentiptycene, which, in an even bulkier H-shape scaffold, can impose more efficient chain packing frustration for high permeability while offering more internal free volume to enable size sieving. The research in this thesis focused on the development and fundamental structure-property relationship studies of several classes of novel pentiptycene-based polymers with heterocyclic rings in the backbone including pentiptycene-based thermally rearranged (TR) polybenzoxazoles (PBO), Tröger's base (TB) polymers, and triptycene-based polybenzimidazoles (TPBI). It was demonstrated that pentiptycene-based TR PBOs and Tröger's base polymers achieved higher permeability-selectivity combinations than their triptycene-based counterparts and transcended the most recent Robeson upper bounds for H2/CH4, O2/N2, and CO2/CH4 gas pairs. In particular, pentiptycene-based TR polymer series showed excellent microstructure tunability enabled through engineering the precursor structures or varying thermal treatment protocols during film preparation processes, which, in turn, led to a wide range of separation performances along with excellent resistance toward plasticization and physical aging in these polymers. Lastly, the first introduction of triptycene moieties into PBI structure was demonstrated for high temperature H2/CO2 separation, from which the efficiently disrupted polymer chain packing led to much enhanced gas permeability compared to existing PBIs that suffer from low H2 permeability with comparable selectivity.