Metal-organic framework compounds used in gas separation membranes based on polyimides with different chemical structures have been surveyed. According to analysis of published data, a metal-organic framework compound composed of MIL-101 and two polyimides with different chemical structures has been selected. Samples of gas separation membranes containing the additive in an amount of 2.5-20 wt % have been prepared to analyze the gas transport characteristics. A significant difference in the permeability and selectivity for a wide range of gases has been shown. The morphological structure of the polymer composites with additive different contents has been analyzed, a the differences in the gas transport properties have been explained.