Research advances of cardo fluorene-based polymer based membranes for gas separation

Gas membrane separation has become one of the technologies to solve major problems in energy, environment and other fields. As the foundation and core of membrane separation technology, high performance membrane materials have always been the focus of research. Membranes based on organic polymer materials are the main commercial gas separation membranes due to their advantages of high design freedom, easy membrane formation and low cost. However, the application of most membranes based on polymer materials are limited by the mutual restriction between permeability and selectivity. The introduction of large volume and twisted groups into the polymer chain can effectively improve gas separation performance. Fluorenyl shows unique large space volume and rigid twisted structure, the introduction of which in polymers will limit the free rotation of the polymer backbone, forming loose accumulations of chain to increase the free volume, eventually improving the gas separation performance of the membranes. Therefore, fluorenyl is favored in the field of gas separation membranes. In this paper, the recent studies on membranes based on fluorene-based polymer materials in the field of gas separation are reviewed. These researches are classified by the structure of polymer materials that make up the membranes and introduced in terms of synthesis, separation mechanism and performance. Finally, the future research directions of fluorene-based polymer gas separation membrane is prospected.