The synthesis of high-performance gas-sieving zeolitic film is challenging because it involves seeded secondary growth which is complex and difficult to reproduce. Additionally, expensive asymmetric inorganic porous supports are often needed for calcination of the zeolite films. Herein, scalable preparation of H2-sieving RUB-15 nanosheet films is reported bypassing the need for secondary growth and expensive supports. A novel, low-cost, thermally-robust, porous polybenzimidazole copolymer (PBI-AM Fumion (R)) support is prepared which allows deposition of thin, compact, and oriented RUB-15 nanosheets films without cracks or pinhole defects. The film hosts two transport pathways, H2-sieving six-membered silicate rings in the nanosheets and nonselective intersheet gaps maintained by the organic guest species in the gallery spacing. The latter is eliminated by a lowtemperature (330 degrees C) calcination where the crystalline order in the nanosheets is preserved. The resulting zeolitic films yielded H2 permeances of 100-400 GPU and H2/CO2 selectivities above 20 at temperatures above 200 degrees C. The facile and scalable fabrication procedure with an attractive H2-sieving performance at elevated temperatures make these membranes promising for pre-combustion carbon capture.