We report in this study the synthesis of thin-film bionanocomposite (BNC) membranes. In the presented study, at firstly, the synthesis and full characterization of new diamine and polyimide derived from amino acid (methionine) and benzimidazole fractions in the structure of pendant group are presented. Then, to improve the effect of surface modification, TiO2 was predisposed in ethanol via ultrasonic waves. Surface modification of TiO2 was conducted using 3-methacryloxypropyl-trimethoxysilane (MPS) under ultrasonic irradiation. The new BNC-containing chiral monomer (amino acid) is employed as a key monomer for the fabrication of a series of BNCs films with various TiO2 percentages under ultrasonic irradiation. The modified TiO2 presented good compatibility in PI matrix. The structures of the modified hybrid nanocomposites were identified with a FT-IR, whereas the size of the TiO2 in polyimides was characterized with a scanning electron microscope (SEM). SEM results indicated the formation and dispersion of nanometer scale size of inorganic domains inside the polyimide matrix due to the introduction of modified TiO2 and the interactions between organic and inorganic phases. The size of TiO2 particles in the modified system was about 25 nm. The transmission electron microscope analysis showing the well-dispersed nanosized titania NPs. Moreover, their thermal and mechanical properties exhibited a significant improvement. The studies on the optical properties of the hybrid films indicate redshift of the absorption band that increased with increased TiO2 content. The high TiO2, content in PI/TiO2, nanocomposite membranes resulted in the great enhancement of gas separation performance of the TiO2 polyimide nanocomposite materials compared with polyimide. When the TiO2, content in PI/TiO2, composite membranes was above 10 wt%, the permeability of the PI/TiO2 composite membranes was remarkably enhanced and the selectivity of PI/TiO2 composite membranes remained at a high level.