Polyimide-carbonized membranes for gas separation: Structural, composition, and morphological control of precursors

It is widely accepted that the characteristics and separation performance of carbonized membranes can be optimized by controlling the parameters of pyrolysis protocol. In spite of this, plenty of research studies have pointed out that the chemical composition and moiety geometry, chain rigidity and structure, and physicochemical properties of polymeric precursors play major roles in determining the properties of the resultant pyrolytic membranes, especially the micropore structure and separation capability. Therefore, the morphological, structural and microphase control of the polymeric membranes are the essential keys to fabricate highly permeable and selective carbon membranes. This review paper aims to give an overview about the precursor materials aspects, preparations and their influence on the separation properties of carbon molecular sieve membranes (CMSMs). The evolution of membrane structure and separation performance from the state of polymer to carbon is also included. The subjects covered in this review paper intend to provide indepth understanding and insights to membranes' researchers with effective preparation of CMSMs from the precursor's point of view.