A gas separation membrane is a semi-permeable barrier that selectively allows certain gas molecules to pass through more rapidly than others, enabling the purification, concentration, or recovery of specific gases from a mixture. The technology operates on the principle of solution-diffusion for polymeric membranes: gases dissolve into the membrane material on the high-pressure side, diffuse through it, and desorb on the low-pressure side. The rate of permeation for each gas is determined by its solubility in the membrane material and its diffusivity through it, which in turn depends on the gas molecule's size and its interaction with the polymer. Membrane materials are engineered for specific separations and include polymeric membranes (e.g., cellulose acetate, polyimide, polysulfone), inorganic membranes (ceramic or zeolite), and advanced mixed-matrix membranes that incorporate inorganic fillers into a polymer matrix to enhance performance.

Gas separation membranes offer a compact, energy-efficient, and modular alternative to traditional processes like cryogenic distillation or pressure swing adsorption. Their major industrial applications are extensive: nitrogen generation from air for inerting and blanketing, oxygen enrichment for medical or industrial use, hydrogen recovery in refineries and ammonia plants, carbon dioxide removal from natural gas (sweetening) and from flue gas (carbon capture), and dehydration of air and natural gas. The advantages include lower energy consumption, no phase change or chemical additives, minimal moving parts, and easy scalability. Ongoing research focuses on developing membranes with higher permeability and selectivity for challenging separations (like olefin/paraffin), improved chemical and thermal stability for harsh conditions, and reduced costs to expand their use in large-scale applications like post-combustion carbon capture, making them a key technology for cleaner industrial processes and energy transition.