The goal of this book is to explore the advantage of employing new technique in increasing gas separation performance of carbon molecular sieve (CMS) membranes. The chemical structure of the blend polymeric components, microstructure of the precursors and the pyrolysis conditions play significant roles in the gas separation performance and transport properties. Membranes were ultimately analyzed with respect to their gas separation properties. Results revealed that interesting gas productivity and efficiency could be achieved in CMS membranes designed and engineered by optimization procedures. We hope that the book will serve as a reference and manual for the industrial and scientist professional academic, while also providing enough basic feed to introduce students to this subject. It is also our hope that the contents will offer guidance for future study, development and various industrial applications in this engineering field as appropriate gas separation membranes with effective performance.