Explore the comprehensive landscape of polymer membrane applications in this book, encompassing gas separation, organic solvent nanofiltration, water desalination, and fuel cells. The text delves into the subtle influence of polymer membranes on energy efficiency across diverse industries, spotlighting advanced variants such as bio-based, mixed matrix, and polyimides-based membranes. Offering an in-depth analysis, the book elucidates the discovery, development, and challenges associated with these state-of-the-art materials, underscoring their role in achieving enhanced performance and energy efficiency.