Sabatier principle in designing CO₂-philic but blocking membranes

Gas transport through polymers follows the sorption-diffusion mechanism, and gas-philic functional groups are often incorporated into polymers to enhance its solubility selectivity and thus separation efficiency. In contrast, we report that polymers exhibiting strong chemisorption toward specific gas molecules can counterintuitively impede their diffusion, illustrated by experimental and simulation studies of CO₂ transport in cross-linked polyamines, paralleling the Sabatier principle observed in catalysis. The CO₂-philic polyamine membrane attains an unprecedented H₂/CO₂ selectivity of 1800, making it highly desirable for H₂ purification. The cross-linked polyamines exhibit excellent self-healing properties and processability for fabricating thin-film composite membranes, indicating great promise for industrial separations. Retarded transport by introducing strongly binding groups presents a promising route for designing membranes for various separations.